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Journal articles on the topic 'Lean burn combustor'
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1
Straub, Douglas L., Kent H. Casleton, Robie E. Lewis, Todd G. Sidwell, Daniel J. Maloney, and George A. Richards. "Assessment of Rich-Burn, Quick-Mix, Lean-Burn Trapped Vortex Combustor for Stationary Gas Turbines." Journal of Engineering for Gas Turbines and Power 127, no. 1 (January 1, 2005): 36–41. http://dx.doi.org/10.1115/1.1789152.
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This paper describes the evaluation of an alternative combustion approach to achieve low emissions for a wide range of fuel types. This approach combines the potential advantages of a staged rich-burn, quick-mix, lean-burn (RQL) combustor with the revolutionary trapped vortex combustor (TVC) concept. Although RQL combustors have been proposed for low-Btu fuels, this paper considers the application of an RQL combustor for high-Btu natural gas applications. This paper will describe the RQL/TVC concept and experimental results conducted at 10 atm (1013 kPa or 147 psia) and an inlet-air temperature of 644 K (700°F). The results from a simple network reactor model using detailed kinetics are compared to the experimental observations. Neglecting mixing limitations, the simplified model suggests that NOx and CO performance below 10 parts per million could be achieved in an RQL approach. The CO levels predicted by the model are reasonably close to the experimental results over a wide range of operating conditions. The predicted NOx levels are reasonably close for some operating conditions; however, as the rich-stage equivalence ratio increases, the discrepancy between the experiment and the model increases. Mixing limitations are critical in any RQL combustor, and the mixing limitations for this RQL/TVC design are discussed.
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Micklow, G. J., S. Roychoudhury, H. L. Nguyen, and M. C. Cline. "Emissions Reduction by Varying the Swirler Airflow Split in Advanced Gas Turbine Combustors." Journal of Engineering for Gas Turbines and Power 115, no. 3 (July 1, 1993): 563–69. http://dx.doi.org/10.1115/1.2906744.
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A staged combustor concept for reducing pollutant emissions is currently under investigation. A numerical study was performed to investigate the chemically reactive flow with liquid spray injection for staged combustion. The staged combustor consists of an airblast atomizer fuel injector, a rich burn section, a converging connecting pipe, a quick mix zone, a diverging connecting pipe and a lean combustion zone. For computational efficiency, the combustor was split into two subsystems, i.e., the fuel nozzle/rich burn section and the quick mix/lean burn section. The current study investigates the effect of varying the mass flow rate split between the swirler passages for an equivalence ratio of 2.0 on fuel distribution, temperature distribution, and emissions for the fuel nozzle/rich burn section of a staged combustor. It is seen that optimizing these parameters can substantially improve combustor performance and reduce combustor emissions. The optimal mass flow rate split for reducing NOx emissions based on the numerical study was the same as found by experiment.
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Di Sarli, Valeria. "Stability and Emissions of a Lean Pre-Mixed Combustor with Rich Catalytic/Lean-burn Pilot." International Journal of Chemical Reactor Engineering 12, no. 1 (January 1, 2014): 77–89. http://dx.doi.org/10.1515/ijcre-2013-0112.
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Abstract In this work, a reactor network model was developed to study homogeneous gas-phase methane combustion taking place under typical operating conditions of lean pre-mixed combustors piloted by rich catalytic/lean-burn (RCL) systems. In particular, the thermo-kinetic interaction between the pilot stream (i.e. the stream exiting the RCL stage) and the main feeding stream to the homogeneous reactor was investigated in terms of combustion stability and emissions. The homogeneous combustor was modeled as a perfectly stirred reactor (PSR). The pilot stream was mixed with the main feeding stream prior to entering the PSR. Numerical results have shown that the opportunity to stabilize combustion is strongly linked to the presence of hydrogen in the pilot stream. Combustion stability is highly sensitive to variations in fuel split between catalytic pilot and homogeneous reactor. The increase in pilot fuel split (and, thus, in the inlet hydrogen concentration to the PSR) enlarges the operating window of stable combustion (in terms of higher heat losses, lower preheat temperatures and lower residence times), while still achieving NOx and CO emissions lower than 9 ppm (at 15% O2). These results highlight the potential of the RCL technology as a valuable alternative to conventional diffusion flame-based pilots.
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Hendricks, R. C., D. T. Shouse, W. M. Roquemore, D. L. Burrus, B. S. Duncan, R. C. Ryder, A. Brankovic, N. S. Liu, J. R. Gallagher, and J. A. Hendricks. "Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with High-Speed Diffuser Flow." International Journal of Rotating Machinery 7, no. 6 (2001): 375–85. http://dx.doi.org/10.1155/s1023621x0100032x.
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The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.
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Serbin, Serhiy, and Nataliia Goncharova. "Investigations of a Gas Turbine Low-Emission Combustor Operating on the Synthesis Gas." International Journal of Chemical Engineering 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/6146984.
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Investigations of the working processes in a gas turbine low-emission combustor operating on the synthesis gas, in which the principle of RQL (Rich-Burn, Quick-Mix, and Lean-Burn) combustion technology is realized, have been performed. Selected concept of a gas turbine combustor can provide higher performance and lower emission of nitrogen oxides and demonstrates satisfactory major key parameters. Obtained results and recommendations can be used for the gas turbine combustor operation modes modeling, geometry optimization, and prospective power generation units design and engineering.
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Li, J., X. Sun, Y. Liu, and V. Sethi. "Preliminary aerodynamic design methodology for aero engine lean direct injection combustors." Aeronautical Journal 121, no. 1242 (June 21, 2017): 1087–108. http://dx.doi.org/10.1017/aer.2017.47.
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ABSTRACTThe Lean Direct Injection (LDI) combustor is one of the low-emissions combustors with great potential in aero-engine applications, especially those with high overall pressure ratio. A preliminary design tool providing basic combustor sizing information and qualitative assessment of performance and emission characteristics of the LDI combustor within a short period of time will be of great value to designers. In this research, the methodology of preliminary aerodynamic design for a second-generation LDI (LDI-2) combustor was explored. A computer code was developed based on this method covering the design of air distribution, combustor sizing, diffuser, dilution holes and swirlers. The NASA correlations for NOxemissions are also embedded in the program in order to estimate the NOx production of the designed LDI combustor. A case study was carried out through the design of an LDI-2 combustor named as CULDI2015 and the comparison with an existing rich-burn, quick-quench, lean-burn combustor operating at identical conditions. It is discovered that the LDI combustor could potentially achieve a reduction in liner length and NOxemissions by 18% and 67%, respectively. A sensitivity study on parameters such as equivalence ratio, dome and passage velocity and fuel staging is performed to investigate the effect of design uncertainties on both preliminary design results and NOxproduction. A summary on the variation of design parameters and their impact is presented. The developed tool is proved to be valuable to preliminarily evaluate the LDI combustor performance and NOxemission at the early design stage.
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Talpallikar, M. V., C. E. Smith, M. C. Lai, and J. D. Holdeman. "CFD Analysis of Jet Mixing in Low NOx Flametube Combustors." Journal of Engineering for Gas Turbines and Power 114, no. 2 (April 1, 1992): 416–24. http://dx.doi.org/10.1115/1.2906607.
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The Rich-burn/Quick-mix/Lean-burn (RQL) combustor has been identified as a potential gas turbine combustor concept to reduce NOx emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NOx levels, cylindrical flametube versions of RQL combustors are being tested at NASA Lewis Research Center. A critical technology needed for the RQL combustor is a method of quickly mixing bypass combustion air with rich-burn gases. In this study, jet mixing in a cylindrical quick-mix section was numerically analyzed. The quick-mix configuration was five inches in diameter and employed 12 radial-inflow slots. The numerical analyses were performed with an advanced, validated 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Parametric varation of jet-to-mainstream momentum flux ratio (J) and slot aspect ratio was investigated. Both nonreacting and reacting analyses were performed. Results showed mixing and NOx emissions to be highly sensitive to J and slot aspect ratio. Lowest NOx emissions occurred when the dilution jet penetrated to approximately midradius. The viability of using 3-D CFD analyses for optimizing jet mixing was demonstrated.
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Garland, R. V., and P. W. Pillsbury. "Status of Topping Combustor Development for Second-Generation Fluidized Bed Combined Cycles." Journal of Engineering for Gas Turbines and Power 114, no. 1 (January 1, 1992): 126–31. http://dx.doi.org/10.1115/1.2906294.
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Addition of a fluidized bed combustor to a high-efficiency combined cycle plant enables direct firing of inexpensive run-of-the-mine coal in an environmentally acceptable manner. To attain high thermal efficiencies, coal pyrolysis is included. The low heating value fuel gas from the pyrolyzer is burned in a topping combustion system that boosts gas turbine inlet temperature to state of the art while the pyrolyzer-produced char is burned in the bed. The candidate topping combustor, the multi-annular swirl burner, based on a design by J. M. Bee´r, is presented and discussed. Design requirements differ from conventional gas turbine combustors. The use of hot, vitiated air for cooling and combustion, and the use of low heating value fuel containing ammonia, are two factors that make the design requirements unique. The multi-annular swirl burner contains rich-burn, quick-quench, and lean-burn zones formed aerodynamically rather than the physically separate volumes found in other rich-lean combustors. Although fuel is injected through a centrally located nozzle, the combustion air enters axially through a series of swirlers. Wall temperatures are controlled by relatively thick layers of air entering through the various swirler sections, which allows the combustor to be of all-metal construction rather than the ceramic often used in rich-lean concepts. This 12-in.-dia design utilizes some of the features of the previous 5-in. and 10-in. versions of the multi-annular swirl burner; test results from the previous projects were utilized in the formulation of the test for the present program. In the upcoming tests, vitiated air will be provided to simulate a pressurized fluidized bed effluent. Hot syngas seeded with ammonia will be used to simulate the low-Btu gas produced in the pyrolyzer.
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Blomeyer, M., B. Krautkremer, D. K. Hennecke, and T. Doerr. "Mixing Zone Optimization of a Rich-Burn/Quick-Mix/Lean-Burn Combustor." Journal of Propulsion and Power 15, no. 2 (March 1999): 288–95. http://dx.doi.org/10.2514/2.5425.
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McGuirk, J. J. "The aerodynamic challenges of aeroengine gas-turbine combustion systems." Aeronautical Journal 118, no. 1204 (June 2014): 557–99. http://dx.doi.org/10.1017/s0001924000009386.
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Abstract The components of an aeroengine gas-turbine combustor have to perform multiple tasks – control of external and internal air distribution, fuel injector feed, fuel/air atomisation, evaporation, and mixing, flame stabilisation, wall cooling, etc. The ‘rich-burn’ concept has achieved great success in optimising combustion efficiency, combustor life, and operational stability over the whole engine cycle. This paper first illustrates the crucial role of aerodynamic processes in achieving these performance goals. Next, the extra aerodynamic challenges of the ‘lean-burn’ injectors required to meet the ever more stringent NO x emissions regulations are introduced, demonstrating that a new multi-disciplinary and ‘whole system’ approach is required. For example, high swirl causes complex unsteady injector aerodynamics; the threat of thermo-acoustic instabilities means both aerodynamic and aeroacoustic characteristics of injectors and other air admission features must be considered; and high injector mass flow means potentially strong compressor/combustor and combustor/turbine coupling. The paper illustrates how research at Loughborough University, based on complementary use of advanced experimental and computational methods, and applied to both isolated sub-components and fully annular combustion systems, has improved understanding and identified novel ideas for combustion system design.
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Solanki Hitesh, K., N. R. Chaudhari, and D. B. Kulshreshtha. "Numerical Simulations of Rich Burn Quick Mix Lean Combustor." Indian Journal of Science and Technology 10, no. 19 (February 1, 2017): 1–5. http://dx.doi.org/10.17485/ijst/2017/v10i19/112544.
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SHAFFAR, S. W., and G. S. SAMUELSEN. "A Liquid Fueled, Lean Burn, Gas Turbine Combustor Injector." Combustion Science and Technology 139, no. 1 (October 1998): 41–57. http://dx.doi.org/10.1080/00102209808952080.
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Döbbeling, Klaus, Jaan Hellat, and Hans Koch. "25 Years of BBC/ABB/Alstom Lean Premix Combustion Technologies." Journal of Engineering for Gas Turbines and Power 129, no. 1 (September 28, 2005): 2–12. http://dx.doi.org/10.1115/1.2181183.
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The paper will show the development of lean premix combustion technologies in BBC, ABB, and Alstom gas turbines. Different technologies have been developed and applied in Brown Boveri Company (BBC) before 1990. Considerable improvements with respect to NOx emissions as compared to gas turbines with a single combustor and a single diffusion burner for liquid and gaseous fuel have been achieved with burners with extended premixing sections and with multi-injection burners for annular combustors. Between 1990 and 2005, burners with short but effective premixing zones (EV burners: environmentally friendly V-shaped burners) have been implemented in all new gas turbines of the ABB (and later Alstom) fleet with NOx levels well below 25 vppmd (@15% O2). In addition to this, three variants of premix technologies have been successfully developed and deployed into Alstom GT engines: the sequential EV burners—a technology that allows premixing of natural gas and oil into a hot exhaust stream to reheat the exhaust gases of a first high-pressure turbine; the MBtu EV burners that are used to burn syngas in a premix flame with low NOx emissions; and the advanced EV burners (AEV) that are capable to prevaporize and premix liquid fuel prior to combustion and burn it with very low NOx emissions without water injection. The paper will give an overview of these technologies and their usage in Alstom gas turbines over the last 25years.
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Smith, Lance L., Hasan Karim, Marco J. Castaldi, Shahrokh Etemad, William C. Pfefferle, Vivek Khanna, and Kenneth O. Smith. "Rich-Catalytic Lean-Burn Combustion for Low-Single-Digit NOx Gas Turbines." Journal of Engineering for Gas Turbines and Power 127, no. 1 (January 1, 2005): 27–35. http://dx.doi.org/10.1115/1.1787510.
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A new rich-catalytic lean-burn combustion concept (trademarked by PCI as RCL) was tested at industrial gas turbine conditions, in Solar Turbines’ high-pressure (17 atm) combustion rig and in a modified Solar Turbines engine, demonstrating ultralow emissions of NOx<2 ppm and CO<10 ppm for natural gas fuel. For the single-injector rig tests, an RCL catalytic reactor replaced a single swirler/injector. NOx<3 ppm and CO<10 ppm were achieved over a 110°C operating range in flame temperature, including NOx<1 ppm at about 1350°C flame temperature. Combustion noise was less than 0.15% peak to peak. Four RCL catalytic reactors were then installed in a modified (single can combustor) engine. NOx emissions averaged 2.1 ppm over the allowable operating range for this modified engine, with CO<10 ppm and without combustion noise (less than 0.15% peak to peak).
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Li, Jianzhong, Jian Chen, Li Yuan, Ge Hu, and Jianhan Feng. "Flow Characteristics of a Rich-Quench-Lean Combustor-Combined Low-Emission and High-Temperature Rise Combustion." International Journal of Aerospace Engineering 2019 (February 11, 2019): 1–22. http://dx.doi.org/10.1155/2019/4014120.
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To determine the flow field structure and flow characteristics of a rich-quench-lean (RQL) combustor-combined low-emission and high-temperature rise combustion, a two-dimensional PIV technology was used to evaluate the effect of aerodynamic and structural parameters on the flow field and flow characteristics of the combustor. The variation in the total pressure loss of the combustor has little effect on the flow field structure of the combustor. However, the variation in the parameters of primary holes significantly affects the structure of the central recirculation zone, the distribution of local recirculation zones in the rich-burn zone and quenching zone, and the average residence time in the quenching zone. On the plane that passes through the center of the primary hole, the variations in the array mode and diameter of primary holes would form entrainment vortexes with different characteristics, thus affecting the position and flow state of local recirculation in the rich-burn zone and the local structure of the central recirculation zone. As the rotational direction of local recirculation coincides with that of the main air flow in the primary zone, the local center recirculation is intensified. In contrast, it is weakened. As the primary holes are located at half height (H/2) of the combustor, the residence time of air flow at the quenching zone can be shortened by 65% through using the staggered structure of primary holes and increasing the momentum of the partial single-hole jet. The quick-mixing process in the quenching zone is not beneficial to increase the number of primary holes and decrease the momentum of the single-hole jet.
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Liu, Cunxi, Fuqiang Liu, Jinhu Yang, Yong Mu, Chunyan Hu, Gang Xu, and Shangmei Su. "Improvement on ignition and lean blowout performances of a piloted lean-burn combustor." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 230, no. 2 (January 7, 2016): 196–205. http://dx.doi.org/10.1177/0957650915623875.
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Li, Y. G., and R. L. Hales. "Steady and Dynamic Performance and Emissions of a Variable Geometry Combustor in a Gas Turbine Engine." Journal of Engineering for Gas Turbines and Power 125, no. 4 (October 1, 2003): 961–71. http://dx.doi.org/10.1115/1.1615253.
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One of the remedies to reduce the major emissions production of nitric oxide NOx, carbon monoxide (CO), and unburned hydrocarbon (UHC) from conventional gas turbine engine combustors at both high and low operating conditions without losing performance and stability is to use variable geometry combustors. This type of combustor configuration provides the possibility of dynamically controlling the airflow distribution of the combustor based on its operating conditions and therefore controlling the combustion in certain lean burn conditions. Two control schemes are described and analyzed in this paper: Both are based on airflow control with variable geometry, the second including fuel staging. A model two-spool turbofan engine is chosen in this study to test the effectiveness of the variable geometry combustor and control schemes. The steady and dynamic performance of the turbofan engine is simulated and analyzed using an engine transient performance analysis code implemented with the variable geometry combustor. Empirical correlations for NOx, CO, and UHC are used for the estimation of emissions. Some conclusions are obtained from this study: (1) with variable geometry combustors significant reduction of NOx emissions at high operating conditions and CO and UHC at low operating condition is possible; (2) combustion efficiency and stability can be improved at low operating conditions, which is symbolized by the higher flame temperature in the variable geometry combustor; (3) the introduced correlation between nondimensional fuel flow rate and air flow ratio to the primary zone is effective and simple in the control of flame temperature; (4) circumferential fuel staging can reduce the range of air splitter movement in most of the operating conditions from idle to maximum power and have the great potential to reduce the inlet distortion to the combustor and improve the combustion efficiency; and (5) during transient processes, the maximum moving rate of the hydraulic driven system may delay the air splitter movement but this effect on engine combustor performance is not significant.
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Fu, Zhenbo, Yuzhen Lin, Lin Li, and Chi Zhang. "Experimental and numerical studies of a lean-burn internally-staged combustor." Chinese Journal of Aeronautics 27, no. 3 (June 2014): 488–96. http://dx.doi.org/10.1016/j.cja.2013.12.017.
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Milcarek, Ryan J., and Jeongmin Ahn. "Rich-burn, flame-assisted fuel cell, quick-mix, lean-burn (RFQL) combustor and power generation." Journal of Power Sources 381 (March 2018): 18–25. http://dx.doi.org/10.1016/j.jpowsour.2018.02.006.
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Wang, Fei, Xueming Li, Shuai Feng, and Yunfei Yan. "Influence of Porous Media Aperture Arrangement on CH4/Air Combustion Characteristics in Micro Combustor." Processes 9, no. 10 (September 29, 2021): 1747. http://dx.doi.org/10.3390/pr9101747.
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Micro-electro-mechanical systems (MEMS) occupy an important position in the national economy and military fields, and have attracted great attention from a large number of scholars. As an important part of the micro-electromechanical system, the micro-combustor has serious heat loss due to its small size, unstable combustion and low combustion efficiency. Aiming at enhancing the heat transfer of the micro-combustor, improving the combustion stability and high-efficiency combustion, this paper embedded porous media in the combustor, and the effects of different parameters on the combustion characteristics were numerically studied. The research results showed that the layout of porous media should be reasonable, and the small and large pore porous media embedded in the inner and outer layers, respectively, can bring better combustion performance. Meanwhile, A: 10–30 has a high and uniform temperature distribution, and its methane conversion rate reached 97.4%. However, the diameter ratio of the inner layer to the outer layer (d/D) of the porous medium should be maintained at 0.4–0.6, which brings a longer gas residence time, and further enables the pre-mixed gas to preheat and burn completely. At a d/D of 0.5, the combustor has the highest outer wall temperature and CH4 conversion efficiency. Besides, compared with the pore size increasing rate of Δn = 10 PPI and Δn = 10 PPI, the radial temperature distribution of the Δn = 10 PPI combustor is more uniform, meanwhile avoids the occurrence of local high temperature. Under the condition of Δn = 10 PPI, A: 20–30 layout maintains excellent thermal and combustion performance. In addition, the lean flammable limits of MC-U20, MC-10/30-0.8, and MC-20/30-0.5 were compared, at an inlet velocity of 0.5 m/s, the corresponding lean flammable limits are 0.5, 0.4, and 0.3, respectively, among them MC-20/30-0.5 has a wider flammable limit range, showing excellent combustion stability. This research has guiding significance for the combustion stability of the micro combustor.
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Pekkan, K., and M. R. Nalim. "Two-Dimensional Flow and NOx Emissions in Deflagrative Internal Combustion Wave Rotor Configurations." Journal of Engineering for Gas Turbines and Power 125, no. 3 (July 1, 2003): 720–33. http://dx.doi.org/10.1115/1.1586315.
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A wave rotor is proposed for use as a constant volume combustor. A novel design feature is investigated as a remedy for hot gas leakage, premature ignition, and pollutant emissions that are possible in this class of unsteady machines. The base geometry involves fuel injection partitions that allow stratification of fuel/oxidizer mixtures in the wave rotor channel radially, enabling pilot ignition of overall lean mixture for low NOx combustion. In this study, available turbulent combustion models are applied to simulate approximately constant volume combustion of propane and resulting transient compressible flow. Thermal NO production histories are predicted by simulations of the STAR-CD code. Passage inlet/outlet/wall boundary conditions are time-dependent, enabling the representation of a typical deflagrative internal combustor wave rotor cycle. Some practical design improvements are anticipated from the computational results. For a large number of derivative design configurations, fuel burn rate, two-dimensional flow and emission levels are evaluated. The sensitivity of channel combustion to initial turbulence levels is evaluated.
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ZHAO, LIMING, HONGHI TRAN, and KIRSTEN MAKI. "Combustion behaviors of lignin-lean black liquor and lignin." July 2015 14, no. 7 (August 1, 2015): 451–58. http://dx.doi.org/10.32964/tj14.7.451.
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For kraft pulp mills that have thermally limited recovery boilers, lignin removal from black liquor has become an attractive option for increasing pulp production by allowing more black liquor to be processed through the boiler. This study systematically examined the combustion characteristics of lignin-lean black liquor and precipitated lignin from three kraft mills using a thermogravimetric combustor. The results confirm that adding lignin-lean black liquor to its original black liquor decreased the heating value and the degree of swelling of the mixed liquor. The effect on liquor swelling, however, was insignificant for mixed liquors that contained less than 20 wt% of lignin-lean liquor. As with other biofuels, the combustion of precipitated lignin was found to occur through three main stages: drying, volatile burning, and char burning. During the volatile burning stage, hardwood lignin swelled significantly, softwood lignin did not swell much, and mixed hardwood and softwood lignin was somewhere in between. Although the char content in lignin was about half of the volatile content, it took 10 times longer for the char to burn compared to the volatiles.
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Corbett, N. C., and N. P. Lines. "Control Requirements for the RB 211 Low-Emission Combustion System." Journal of Engineering for Gas Turbines and Power 116, no. 3 (July 1, 1994): 527–33. http://dx.doi.org/10.1115/1.2906851.
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The RB 211 DLE series staged, premix, lean burn combustor demands total integration of control system and combustion hardware. The controls design process is described from the conception of the Engine Management System (EMS), which provides protection and control in separate environments, through to implementation of engine development testing. The process of devising an acceptable fueling strategy to each combustion stage is discussed. This identified the requirements for the computation of complex routines in order to control combustion zone temperatures. The sensitivity of the control design to external conditions of humidity, ambient temperature, and fuel composition is explored. Extensive simulation was used to determine necessary instrumentation accuracies. The paper concludes with a review of the development testing and the final control system configuration.
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Leong, M. Y., C. S. Smugeresky, V. G. McDonell, and G. S. Samuelsen. "Rapid Liquid Fuel Mixing for Lean-Burning Combustors: Low-Power Performance." Journal of Engineering for Gas Turbines and Power 123, no. 3 (January 1, 2001): 574–79. http://dx.doi.org/10.1115/1.1362318.
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Designers of advanced gas turbine combustors are considering lean direct injection strategies to achieve low NOx emission levels. In the present study, the performance of a multipoint radial airblast fuel injector Lean Burn injector (LBI) is explored for various conditions that target low-power gas turbine engine operation. Reacting tests were conducted in a model can combustor at 4 and 6.6 atm, and at a dome air preheat temperature of 533 K, using Jet-A as the liquid fuel. Emissions measurements were made at equivalence ratios between 0.37 and 0.65. The pressure drop across the airblast injector holes was maintained at 3 and 7–8 percent. The results indicate that the LBI performance for the conditions considered is not sufficiently predicted by existing emissions correlations. In addition, NOx performance is impacted by atomizing air flows, suggesting that droplet size is critical even at the expense of penetration to the wall opposite the injector. The results provide a baseline from which to optimize the performance of the LBI for low-power operation.
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Verrilli, M. J., and D. Brewer. "Characterization of Ceramic Matrix Composite Fasteners Exposed in a Combustor Linear Rig Test." Journal of Engineering for Gas Turbines and Power 126, no. 1 (January 1, 2004): 45–49. http://dx.doi.org/10.1115/1.1639005.
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Combustion tests on SiC/SiC CMC components were performed in an aircraft combustion environment using the rich-burn, quick-quench, lean-burn (RQL) sector rig. SiC/SiC fasteners were used to attach several of these components to the metallic rig structure. The effect of combustion exposure on the fastener material was characterized via microstructural examination. Fasteners were also destructively tested, after combustion exposure, and the failure loads of fasteners exposed in the sector rig were compared to those of as-manufactured fasteners. Combustion exposure reduced the average fastener failure load by 50% relative to the as-manufactured fasteners for exposure times ranging from 50 to 260 hours. The fasteners exposed in the combustion environment demonstrated failure loads that varied with failure mode. Fasteners that had the highest average failure load, failed in the same manner as the unexposed fasteners.
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Antoshkiv, O., Th Poojitganont, L. Jehring, and C. Berkholz. "Main aspects of kerosene and gaseous fuel ignition in aero-engine." Aeronautical Journal 121, no. 1246 (December 2017): 1779–94. http://dx.doi.org/10.1017/aer.2017.113.
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ABSTRACTVarious liquid and gaseous alternative fuels have been proposed to replace the kerosene as aircraft fuel. Furthermore, new combustion technologies were developed to reduce the emissions of aero-engine. A staged fuel injection arrangement for a lean burn combustion system was applied to improve the operability of an aero-engine by achieving high flame stability at reduced combustion emissions. Originally, both circuits (pilot and main) are fuelled by kerosene; moreover, the pilot injector is operating at low power (engine idle and approach) and the pilot flame is anchored in an airflow recirculation zone. In the case of the performed research, the pilot injector was modified to allow the use of gaseous fuels. Thus, the burner model allows a flexible balancing of the mass flows for gaseous and liquid fuel. The present paper describes the investigation of ignitability for the proposed staged combustor model fuelled by gaseous and liquid fuels. A short overview on physical properties of used fuels is given. To investigate atomisation and ignition, different measurements systems were used. The effectiveness of two ignitor types (spark plug and laser ignitor) was analysed. The ignition performance of the combustor operating on various fuels was compared and discussed in detail.
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Lefebvre, A. H. "The Role of Fuel Preparation in Low-Emission Combustion." Journal of Engineering for Gas Turbines and Power 117, no. 4 (October 1, 1995): 617–54. http://dx.doi.org/10.1115/1.2815449.
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The attainment of very low pollutant emissions, in particular oxides of nitrogen (NOx), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultralow NOx has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultralow emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas-turbine-generated pollutants and their mechanisms of formation are described, along with related environmental risks and various issues concerning emissions regulations and recently enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impacts of these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basic approaches to the design of “dry” low-NOx and ultralow-NOx combustors are reviewed. At the present time lean, premix, prevaporize combustion appears to be the only technology available for achieving ultralow NOx emissions from practical combustors. This concept is discussed in some detail, along with its inherent problems of autoignition, flashback, and acoustic resonance. Attention is also given to alternative methods of achieving ultralow NOx emissions, notably the rich-burn, quick-quench, lean-burn, and catalytic combustors. These concepts are now being actively developed, despite the formidable problems they present in terms of mixing and durability. The final section reviews the various correlations now being used to predict the exhaust gas concentrations of the main gaseous pollutant emissions from gas turbine engines. Comprehensive numerical methods have not yet completely displaced these semi-empirical correlations but are nevertheless providing useful insight into the interactions of swirling and recirculating flows with fuel sprays, as well as guidance to the combustion engineer during the design and development stages. Throughout the paper emphasis is placed on the important and sometimes pivotal role played by the fuel preparation process in the reduction of pollutant emissions from gas turbines.
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Serbin, Serhiy I., Igor B. Matveev, and Ganna B. Mostipanenko. "Investigations of the Working Process in a “Lean-Burn” Gas Turbine Combustor With Plasma Assistance." IEEE Transactions on Plasma Science 39, no. 12 (December 2011): 3331–35. http://dx.doi.org/10.1109/tps.2011.2166811.
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Notaristefano, Andrea, and Paolo Gaetani. "Design and Commissioning of a Combustor Simulator Combining Swirl and Entropy Wave Generation." International Journal of Turbomachinery, Propulsion and Power 5, no. 4 (October 19, 2020): 27. http://dx.doi.org/10.3390/ijtpp5040027.
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Modern aero-engine combustion chambers burn a lean and premixed mixture, generating a turbulent flame which involves large heat-release fluctuations, thus producing unsteady temperature phenomena commonly referred to as entropy waves (EWs). Furthermore, to enhance the fuel air mixing, combustion air is swirled, leading to vorticity disturbances. These instabilities represent one of the biggest challenges in gas turbine design. In this paper, the design and testing of a novel entropy wave generator (EWG) equipped with a swirler generator (SG) are described. The novel EWG will be used in future works on the high-speed test rig at Politecnico di Milano to study the combustor–turbine interaction. The paper shows the process of the EWG geometry and layout. The EWG is able to produce an engine-representative EW, the extreme condition is at the maximum frequency of 110 Hz, a peak-to-valley temperature value of 20 °C and swirling angles of ±25° are measured. By virtue of these results, the proposed system outperforms other EWG devices documented in the literature. Furthermore, the addition of a swirling generator makes this device one of a kind.
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Zhang, Wenhao, Zhiduo Wang, Zhihao Wang, Ruocheng Li, and Zhenping Feng. "Study on heat transfer characteristics of NGVs influenced by non-reacting lean burn combustor simulator flow." International Journal of Thermal Sciences 172 (February 2022): 107313. http://dx.doi.org/10.1016/j.ijthermalsci.2021.107313.
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Innocenti, Alessandro, Antonio Andreini, and Bruno Facchini. "Numerical Identification of a Premixed Flame Transfer Function and Stability Analysis of a Lean Burn Combustor." Energy Procedia 82 (December 2015): 358–65. http://dx.doi.org/10.1016/j.egypro.2015.11.803.
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Innocenti, Alessandro, Antonio Andreini, Bruno Facchini, and Antonio Peschiulli. "Numerical analysis of the dynamic flame response of a spray flame for aero-engine applications." International Journal of Spray and Combustion Dynamics 9, no. 4 (May 16, 2017): 310–29. http://dx.doi.org/10.1177/1756827717703577.
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Incoming standards on NO x emissions are motivating many aero-engine manufacturers to adopt the lean burn combustion concept. One of the most critical issues affecting this kind of technology is the occurrence of thermo-acoustic instabilities that may compromise combustor life and integrity. Therefore the prediction of the thermo-acoustic behaviour of the system becomes of primary importance. In this paper, the complex interaction between the system acoustics and a turbulent spray flame for aero-engine applications is numerically studied. The dynamic flame response is computed exploiting reactive URANS simulations and system identification techniques. Great attention has been devoted to the impact of liquid fuel evolution and droplet dynamics. For this purpose, the GE Avio PERM (partially evaporating and rapid mixing) lean injection system has been analysed, focussing attention on the effect of several modelling parameters on the combustion and on the predicted flame response. A frequency analysis has also been set up and exploited to obtain even more insight on the dynamic flame response of the spray flame. The application is one of the few in the literature where the dynamic flame response of spray flames is numerically investigated, providing a description in terms of flame transfer function and detailed information on the physical phenomena.
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Amoroso, Francesco, Angelo De Fenza, Giuseppe Petrone, and Rosario Pecora. "A Sensitivity Analysis on the Influence of the External Constraints on the Dynamic Behaviour of a Low Pollutant Emissions Aircraft Combustor-Rig." Archive of Mechanical Engineering 63, no. 3 (September 1, 2016): 435–54. http://dx.doi.org/10.1515/meceng-2016-0025.
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Abstract The need to reduce pollutant emissions leads the engineers to design new aeronautic combustors characterized by lean burn at relatively low temperatures. This requirement can easily cause flame instability phenomena and consequent pressure pulsations which may seriously damage combustor’s structure and/or compromise its fatigue life. Hence the need to study the combustor’s structural dynamics and the interaction between elastic, thermal and acoustic phenomena. Finite element method represent a largely used and fairly reliable tool to address these studies; on the other hand, the idealization process may bring to results quite far from the reality whereas too simplifying assumptions are made. Constraints modelling represent a key-issue for all dynamic FE analyses; a wrong simulation of the constraints may indeed compromise entire analyses although running on very accurate and mesh-refined structural models. In this paper, a probabilistic approach to characterize the influence of external constraints on the modal behaviour of an aircraft combustor-rig is presented. The finite element model validation was performed at first by comparing numerical and experimental results for the free-free condition (no constraints). Once the model was validated, the effect of constraints elasticity on natural frequencies was investigated by means of a probabilistic design simulation (PDS); referring to a specific tool developed in the ANSYS®software, a preliminary statistical analysis was at performed via Monte-Carlo Simulation (MCS) method. The results were then correlated with the experimental ones via Response Surface Method (RSM).
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Kim, Namsu, Minjung Lee, Juwon Park, Jeongje Park, and Taesong Lee. "A Comparative Study of NOx Emission Characteristics in a Fuel Staging and Air Staging Combustor Fueled with Partially Cracked Ammonia." Energies 15, no. 24 (December 19, 2022): 9617. http://dx.doi.org/10.3390/en15249617.
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Recently, ammonia is emerging as a potential source of energy in power generation and industrial sectors. One of the main concerns with ammonia combustion is the large amount of NO emission. Air staging is a conventional method of reducing NO emission which is similar to the Rich-Burn, Quick-Mix, Lean-Burn (RQL) concept. In air-staged combustion, a major reduction of NO emission is based on the near zero NO emission at fuel-rich combustion of NH3/Air mixture. A secondary air stream is injected for the oxidation of unburned hydrogen and NHx. On the other hand, in fuel-staged combustion, NO emission is reduced by splitting NH3 injection, which promotes the thermal DeNOx process. In this study, NOx emission characteristics of air-staged and fuel-staged combustion of partially cracked ammonia mixture are numerically investigated. First, the combustion system is modeled by a chemical reactor network of a perfectly stirred reactor and plug flow reactor with a detailed chemistry mechanism. Then, the effects of ammonia cracking, residence time, and staging scheme on NOx emission are numerically analyzed. Finally, the limitations and optimal conditions of each staging scheme are discussed.
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Treleaven, N. C. W., A. Garmory, and G. J. Page. "The Effects of Turbulence on Jet Stability and the Flame Transfer Function in a Lean-burn Combustor." Combustion Science and Technology 192, no. 11 (July 18, 2020): 2115–37. http://dx.doi.org/10.1080/00102202.2020.1777992.
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O'Doherty, T., D. J. Morgan, and N. Syred. "A Multi Fuelled Cyclone Combustor." Energy & Environment 3, no. 4 (June 1992): 401–16. http://dx.doi.org/10.1177/0958305x9200300405.
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The paper outlines a series of tests carried out on a prototype 1.5 MW vertical cyclone combustor with integral ash removal which removes in excess of 80% of the ash. For high calorific value fuels such as coal the system is run fuel rich to avoid slagging. The low calorific value exhaust gases are passed via a transfer duct into an inverted swirl burner/furnace arrangement where final burnout of the gasified products occur. The sytem, designed to utilise a wide range of solid fuels was evaluated for a range of biomass materials and coal. The coal work investigated the effects of crushed (dm ≃ 250 μm) and pulverised (dm ≃ 70–80 μm) bituminous coals on system performance whilst biomass trials investigated the effects of chopped straw, chicken litter, shredded paper and refuse derived fuels. The fuel and air were premixed and fired tangentially in all cases into the primary combustor. The combustor was operated over a range of mixture ratios (φ) from fuel rich (φ = 0.5) to fuel lean (φ = 2.0) with temperatures in the order of 1250°C, hence operated in a non-slagging mode. The whole system was operated with a minimum of secondary air, required only to burn the gasified products from the primary chamber. The trials included monitoring of exhaust gases for a range of emissions. In addition, isokinetic sampling of the exhaust gases was carried out to determine particulate emission levels. Results show that best fuel burnout is achieved with biomass material levels better than 99% being achieved. Satisfactory performance was achieved with coal, (ash retention emissions) with fuel burnout in the order of 80%. Ash retention values for the biomass materials was in excess of 80% up to 98%. Coal ash retention levels were lower when analysed on a mass balance basis but of the same order when considering particulate emissions.
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Karim, H., K. Lyle, S. Etemad, L. L. Smith, W. C. Pfefferle, P. Dutta, and K. Smith. "Advanced Catalytic Pilot for Low NOx Industrial Gas Turbines." Journal of Engineering for Gas Turbines and Power 125, no. 4 (October 1, 2003): 879–84. http://dx.doi.org/10.1115/1.1586313.
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This paper describes the design and testing of a catalytically stabilized pilot burner for current and advanced Dry Low NOx (DLN) gas turbine combustors. In this paper, application of the catalytic pilot technology to industrial engines is described using Solar Turbines’ Taurus 70 engine. The objective of the work described is to develop the catalytic pilot technology and document the emission benefits of catalytic pilot technology when compared to higher, NOx producing pilots. The catalytic pilot was designed to replace the existing pilot in the existing DLN injector without major modification to the injector. During high-pressure testing, the catalytic pilot showed no incidence of flashback or autoignition while operating over wide range of combustion temperatures. The catalytic reactor lit off at a temperature of approximately 598 K (325°C/617°F) and operated at simulated 100% and 50% load conditions without a preburner. At high pressure, the maximum catalyst surface temperature was similar to that observed during atmospheric pressure testing and considerably lower than the surface temperature expected in lean-burn catalytic devices. In single-injector rig testing, the integrated assembly of the catalytic pilot and Taurus 70 injector demonstrated NOx and CO emission less than 5 ppm @ 15% O2 for 100% and 50% load conditions along with low acoustics. The results demonstrate that a catalytic pilot burner replacing a diffusion flame or partially premixed pilot in an otherwise DLN combustor can enable operation at conditions with substantially reduced NOx emissions.
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Bell, R. C., T. W. Prete, and J. T. Stewart. "Specification, Development, and Testing of the FT8-2 Dry Low NOx Control System." Journal of Engineering for Gas Turbines and Power 118, no. 3 (July 1, 1996): 547–52. http://dx.doi.org/10.1115/1.2816682.
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This paper describes the specification, development, and testing of the FT8-2 Dry Low NOx control system, and how the lean burn process requires an integration of the control system and combustion hardware. The FT8-2 digital fuel control system was developed to achieve the precise multizone fuel metering of both gas and liquid fuels, the calculation of combustor air flow necessary to achieve Dry Low NOx and the traditional governing/limiting control loops necessary for safe, stable engine operation. The system design goals were accomplished by the concurrent development of software-based fuel metering algorithms and fuel metering hardware. The fuel metering hardware utilizes an all-electronic valve positioner, employing a combination of feedback and software to achieve closed-loop control of actual fuel flow. Extensive testing under actual gas flow conditions and closed-loop bench testing using a real time engine model and fuel system model was conducted to prove system operation and develop system transient response prior to installation on the test engine. The setup and results of the flow testing and closed-loop testing are described. The paper describes the control scheme used to apportion the gas fuel between combustion zones and how external conditions such as ambient temperature and fuel gas composition affect the apportionment. The paper concludes with a description of the control system installation in the engine test cell and a review of engine test results.
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Mills, Andrew Robert, and Visakan Kadirkamanathan. "Sensing for aerospace combustor health monitoring." Aircraft Engineering and Aerospace Technology 92, no. 1 (January 6, 2020): 37–46. http://dx.doi.org/10.1108/aeat-11-2018-0283.
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Purpose This paper proposes new methods of fault detection for fuel systems in order to improve system availability. Novel fault systems are required for environmentally friendly lean burn combustion, but can carry high risk failure modes particularly through their control valves. The purpose of the developed technology is the rapid detection of these failure modes, such as valve sticking or impending sticking, and therefore to reduce this risk. However, sensing valve state is challenging due to hot environmental temperatures, which results in a low reliability for conventional position sensing. Design/methodology/approach Starting with the business needs elicited from stakeholders, a quality functional deployment process is performed to derive sensing system requirements. The process acknowledges the difference between test-bed and in-service aerospace needs through weightings on requirements and maps these customer requirements to systems performance metrics. The design of the system must therefore optimise the sensor suite, on- and off-board signal processing and acquisition strategy. Findings Against this systems engineering process, two sensing strategies are outlined which illustrate the span of solutions, from conventional gas path sensing with advanced signal processing to novel non-invasive sensing concepts. While conventional sensing may be feasible within a test cell, the constraints of aerospace in-service operation may necessitate more novel alternatives. Acoustic emission (detecting very high frequency surface vibration waves) sensing technology is evaluated to provide a non-invasive, remote and high temperature tolerant solution. Through this comparison, the considerations for the end-to-end system design are highlighted to be critical to sensor deployment success in-service. Practical implications The paper provides insight into different means of addressing the important problem of monitoring faults in combustor systems in gas turbines. By casting of the complex design problem within a systems engineering framework, the outline of a toolset for solution evaluation is provided. Originality/value The paper provides three areas of significant contributions: a diversity of methods to diagnosing fuel system malfunctions by measuring changes fuel flow distributions, through novel means, and the combustor exit temperature profiles (cause and effect); the use of analytical methods to support the selection (types and quantities) and placement of sensors to ensure adequate state awareness while minimising their impact on the engine system cost and weight; and an end-to-end data processing approach to provide optimised information for the engine maintainers allowing informed decision-making.
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Huang, Shengfang, Zhibo Zhang, Huimin Song, Yun Wu, and Yinghong Li. "A Novel Way to Enhance the Spark Plasma-Assisted Ignition for an Aero-Engine Under Low Pressure." Applied Sciences 8, no. 9 (September 1, 2018): 1533. http://dx.doi.org/10.3390/app8091533.
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Finding a new ignition strategy for ignition enhancement in a lean-burn combustor has always been the biggest challenge for high-altitude, long-endurance unmanned aerial vehicles (UAVs). It is of great importance for the development of high-altitude, long-endurance aircraft to improve the secondary ignition ability of the aero-engine at high altitude where the ignition capability of the aero-engine igniter rapidly declines. An innovative ignition mode is therefore urgently needed. A novel plasma-assisted ignition method based on a multichannel discharge jet-enhanced spark (MDJS) was proposed in this study. Compared to the conventional spark igniter (SI), the arc discharge energy of the MDJS was increased by 13.6% at 0.12 bar and by 14.7% at 0.26 bar. Furthermore, the spark plasma penetration depth of the MDJS was increased by 49% and 103% at 0.12 bar and 0.26 bar, respectively. The CH* radicals showed that the MDJS obtained a larger initial spark kernel and reached a higher spark plasma penetration depth, which helped accelerate the burning velocity. Ignition tests in a model swirl combustor showed that the lean ignition limit was extended 24% from 0.034 to 0.026 at 25 m/s with 20 °C kerosene and 17% from 0.075 to 0.062 at 12 m/s with −30 °C kerosene maximally. The MDJS was a unique plasma-assisted ignition method, activated by the custom ignition power supply instead of a special power supply with an extra gas source. The objective of this study was to provide a novel multichannel discharge jet-enhanced spark ignition strategy which would help to increase the arc discharge energy, the spark plasma penetration depth and the activated area without changing the power supply system and to improve the safety and performance of aero-engines.
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Bertini, Davide, Lorenzo Mazzei, and Antonio Andreini. "Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD." Entropy 23, no. 7 (July 15, 2021): 901. http://dx.doi.org/10.3390/e23070901.
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Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.
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Meyers, D. P., and J. T. Kubesh. "The Hybrid Rich-Burn/Lean-Burn Engine." Journal of Engineering for Gas Turbines and Power 119, no. 1 (January 1, 1997): 243–49. http://dx.doi.org/10.1115/1.2815555.
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This paper describes a new low-emissions engine concept called the hybrid rich-burn/lean-burn (HRBLB) engine. In this concept a portion of the cylinders of a multicylinder engine are fueled with a very rich natural gas-air mixture. The remaining cylinders are operated with a lean mixture of natural gas and air and supplemented with the rich combustion exhaust. The goal of this unique concept is the production of extremely low NOx (e.g., 5 ppm when corrected to 15 percent exhaust oxygen content). This is accomplished by operating outside the combustion limits where NOx is produced. In rich combustion an abundance of hydrogen and carbon monoxide is produced. Catalyst treatment of the rich exhaust can be employed to increase the hydrogen concentration and decrease the carbon monoxide concentration simultaneously. The hydrogen-enriched exhaust is used to supplement the lean mixture cylinders to extend the lean limit of combustion, and thus produces ultralow levels of NOx. Results to date have shown NOx levels as low as 8 ppm at 15 percent oxygen can be achieved with good combustion stability and thermal efficiency.
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Stone, C. R., K. J. S. Mentis, and M. Daragheh. "Measurements and Modelling of a Lean Burn Gas Engine." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 210, no. 6 (December 1996): 449–62. http://dx.doi.org/10.1243/pime_proc_1996_210_072_02.
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Natural gas is an alternative fuel that has potential for low emissions and a high efficiency. This paper presents the experimental results and predictions from a computer simulation of a fast burn high compression ratio (FBHCR) combustion system intended for use in a lean burn natural gas engine. Comparisons are made between the FBHCR combustion system at two compression ratios, predictions made by a two-zone combustion model and measurements from the original combustion system, for the brake efficiency, brake mean effective pressure, maximum cylinder pressure and the brake specific NOx emissions. Experimental measurements of the unburnt hydrocarbon emissions, the burn duration and the cycle-by-cycle variations in combustion are also discussed from the original and fast burn combustion systems. The results show how the conflicting aims of low emissions and low fuel consumption can be satisfied using a lean burn combustion system. The computer predictions are shown to be reliable, and thus suitable for estimating the performance of other engine builds.
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Mendis, K. J. S., C. R. Stone, N. Ladommatos, and M. Daragheh. "A Lean Burn Low Emissions Gas Engine for Co-Generation." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 210, no. 3 (June 1996): 203–11. http://dx.doi.org/10.1243/pime_proc_1996_210_033_02.
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This paper presents the rationale behind a fast burn high compression ratio (FBHCR) combustion system intended for use in a lean burn natural gas engine. Comparisons are made between the FBHCR combustion system, predictions made by a two-zone combustion model and measurements from the original combustion system, for the brake efficiency, brake mean effective pressure and the brake specific NOx emissions. Experimental measurements of the unburnt hydrocarbon emissions, the burn duration and the cycle-by-cycle variations in combustion are also discussed from the two combustion systems. The results show how the conflicting aims of low emissions and low fuel consumption can be satisfied by using a lean burn combustion system. A comparison is also made between the following ways of expressing the exhaust emissions: volumetric, brake specific, mass per megajoule of fuel and gravimetric referenced to a specified oxygen level.
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Mehdi, Ghazanfar, Sara Bonuso, and Maria Grazia De Giorgi. "Plasma Assisted Re-Ignition of Aeroengines under High Altitude Conditions." Aerospace 9, no. 2 (January 26, 2022): 66. http://dx.doi.org/10.3390/aerospace9020066.
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Re-ignition of aeroengines under high altitude conditions is of great importance to the safety and use of lean-burn flame. This study is focused on the experimental and numerical characterization of flow dynamics and flame re-ignition in a rectangular burner. A ring-needle type plasma actuator was considered and run by high-voltage (HV) nanopulsed plasma generator. The electrical power delivered to the fluid and an optimal value of reduced electric field (EN) was calculated considering non-reactive flow. Smoke flow visualizations using a high-speed camera and proper orthogonal decomposition (POD) were performed to recognize the most dominant flow structures. Experimental results revealed the transport effects due to plasma discharge, such as the induced flow, that could have a strong impact on the recirculation zone near the corners of combustor, improving the mixing performance and reducing the ignition delay time. Two different numerical tools (ZDPlasKin and Chemkin) were used to investigate the ignition characteristics. ZDPlasKin calculated the thermal effect and the plasma kinetic of nanopulsed plasma discharge at the experimentally measured EN. Finally, based on the output of ZDPlasKin, Chemkin estimated the flame ignition at low pressure and low temperature conditions. It was noticed that time required to achieve the maximum flame temperature with plasma actuation is significantly less than the auto-ignition time (‘clean case’, simulation result of the model without considering the plasma effect). Maximum reduction in ignition time was observed at inlet pressure 1 bar (3.5 × 10−5 s) with respect to the clean case (1.1 × 10−3 s). However, as the inlet pressure is reduced, the ignition delay time was increased. At 0.6 bar flame ignition occurred in clean case at 0.0048 s and at 0.0022 s in presence of the plasma actuation, a further decrease of the pressure up to 0.4 bar leads the ignition at 0.0027 s and 0.0063 s in clean and plasma actuation, respectively.
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Costa, Roberto B. R., Carlos A. J. Gomes, Fabricio J. P. Pujatti, Ramon Molina Valle, and José E. M. Barros. "Ethanol Lean Combustion Characteristics of a GDI Engine." Applied Mechanics and Materials 798 (October 2015): 219–23. http://dx.doi.org/10.4028/www.scientific.net/amm.798.219.
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In the present study, ethanol combustion analysis was carried in a wall guided type GDI engine, to achieve combustion stability under lean burn operation and to expand the flammability limit for increasing engine efficiency. Tests were performed at constant engine speed, load and injection pressure (1000 rpm, NIMEP = 3 bar, 100 bar), for a wide range of injection, ignition and mixture formation parameters. NISFC, combustion stability, PMEP and burn duration were evaluated at each excess air ratio. An improvement on fuel economy and, consequently, increased engine efficiency was achieved for excess air ratios of λ = 1.1 and λ = 1.2.
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Shahzad, Raja, P. Naveenchandran, A. Rashid, and Amir Aziz. "Characteristics of Lean and Stoichiometric Combustion of Compressed Natural Gas in a Direct Injection Engine." Applied Mechanics and Materials 110-116 (October 2011): 357–69. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.357.
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This paper discusses the combustion characteristics of CNG under lean and stochiometric conditions in a direct injection engine. The experiments were carried out on a dedicated CNG-Direct Injection engine with 14:1 compression ratio. Combustion characteristics of CNG have been investigated on various injection timings. Injection timing of the fuel injection timing had significant effects on the engine performance, combustion and emissions. The effects became more significant when injection timing was retarded. Injection timing was set after the closing of intake valve and experiments are conducted at 0% and 50% load conditions. Lean stratified operation experiences faster combustion compared to that of stochiometric. In lean stratified operation, there were fast burn rates at the initial stage and slower burning at the later stage. Whereas in stochiometric conditions there is a slightly slower burn at the initial stage and a moderately faster burn at the later stage. The faster initial combustion in lean stratified operation might be due to rapid burn of the initial mixture due to higher turbulence, while a slower burn in the later stage due to diffusion. In contrary to that in stochiometric operations the initial burn is slightly slower, due to moderately strong turbulence and a faster burn due to moderately proceeding mixture. Thus the main effect of fuel injection timing can be explained by the fuel air mixing and the turbulence produced.
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Bureshaid, Khalifa, Dengquan Feng, Hua Zhao, and Mike Bunce. "Combustion and emissions of gasoline, anhydrous ethanol, and wet ethanol in an optical engine with a turbulent jet ignition system." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 13 (February 8, 2019): 3528–37. http://dx.doi.org/10.1177/0954407019825999.
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Turbulent jet ignition is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. Turbulent jet ignition works by injecting chemical active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of turbulent jet ignition is its ability to ignite and burn completely very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at lower combustion temperature. The purpose of the paper is to study the combustion characteristics of gasoline, ethanol, and wet ethanol when operated with the pre-chamber combustion system and the ability of the pre-chamber ignition to extend the lean-burn limits of such fuels. The combustion and heat release process was analyzed and exhaust emissions measured. Results show that the effect of turbulent jet ignition system on the lean-burn limit and exhaust emissions varied with fuels. The lean limit was extended by using fueled pre-chamber furthest, to λ = 1.71 with gasoline, followed by λ = 1.77 with wet ethanol and λ = 1.9 with ethanol. NOx emissions were significantly reduced with increased lambda for each fuel under stable combustion conditions. For ethanol, at maximum lean limit lambda 1.9, the NOx emissions were almost negligible due to lower combustion temperature.
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Breitbach, Hermann, Anton Waltner, Tilo Landenfeld, and Christian Schwarz. "Lean-burn Stratified Combustion at Gasoline Engines." MTZ worldwide 74, no. 5 (April 12, 2013): 10–16. http://dx.doi.org/10.1007/s38313-013-0047-y.
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Fu, Xue-Qing, Bang-Quan He, Si-Peng Xu, Tao Chen, Hua Zhao, Yan Zhang, Yufeng Li, and Honglin Bai. "Multi-point micro-flame ignited hybrid lean-burn combustion of gasoline with direct injection dimethyl ether." International Journal of Engine Research 22, no. 1 (April 8, 2019): 140–51. http://dx.doi.org/10.1177/1468087419840469.
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Lean-burn combustion is effective in reducing fuel consumption of gasoline engines because of the higher specific heat ratio of the fuel lean mixture and reduced heat loss from lower combustion temperature. However, its application to real engines is hampered by the unstable ignition, high cyclic variability, and partial-burn due to slower combustion, as well as the restricted maximum lean-burn air/fuel ratio limit and the insufficiently low nitrogen oxides emission. Multi-point micro-flame-ignited hybrid combustion has been proposed and applied to extend the lean burn limit of premixed gasoline and air mixture. To achieve micro-flame-ignited combustion in premixed lean gasoline mixture formed by port fuel injection, a small amount of dimethyl ether is injected directly into the cylinder of a four-stroke gasoline engine to control and accelerate the ignition and combustion process so that the engine could be operated with the overall excess air coefficient (Lambda) of 1.9. The results show that heat release processes can be grouped into three forms, that is, ramp type, double-peak type, and trapezoid type. Regardless of single or split injections, direct injection timing of dimethyl ether dominates the features of heat release. The ramp type occurs at early injection timing while the double-peak type takes place at late injection timing. Trapezoid type appears between the above two types. Dimethyl ether injection timing controls the ignition timing and has less effect on combustion duration. Single injection of dimethyl ether leads to much earlier ignition timing and slightly longer combustion duration, forming higher nitrogen oxides emissions than the split injections. Ultra-low nitrogen oxides emissions and higher thermal efficiency are achieved in the ramp type combustion compared to the other two types of combustion in both injection approaches.