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Добірка наукової літератури з теми "Low-swirl"

Автор: Grafiati

Опубліковано: 10 березня 2023

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Статті в журналах з теми "Low-swirl"

Xiao, Yinli, Zhibo Cao, and Changwu Wang. "Flame stability limits of premixed low-swirl combustion." Advances in Mechanical Engineering 10, no. 9 (September 2018): 168781401879087. http://dx.doi.org/10.1177/1687814018790878.

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The objective of this study is to gain a fundamental understanding of the flow-field and flame behaviors associated with a low-swirl burner. A vane-type low-swirl burner with different swirl numbers has been developed. The velocity field measurements are carried out with particle image velocimetry. The basic flame structures are characterized using OH radicals measured by planar laser-induced fluorescence. Three combustion regimes of low-swirl flames are identified depending on the operating conditions. For the same low-swirl injector under atmospheric conditions, attached flame is first observed when the incoming velocity is too low to generate vortex breakdown. Then, W-shaped flame is formed above the burner at moderate incoming velocity. Bowl-shaped flame structure is formed as the mixture velocity increases until it extinct. Local extinction and relight zones are observed in the low-swirl flame. Flow-field features and flame stability limits are obtained for the present burner.

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Kida, Shigeo, and Hideaki Miura. "Swirl Condition in Low-Pressure Vortices." Journal of the Physical Society of Japan 67, no. 7 (July 15, 1998): 2166–69. http://dx.doi.org/10.1143/jpsj.67.2166.

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Verbeek, Anton A., Thijs W. F. M. Bouten, Genie G. M. Stoffels, Bernard J. Geurts, and Theo H. van der Meer. "Fractal turbulence enhancing low-swirl combustion." Combustion and Flame 162, no. 1 (January 2015): 129–43. http://dx.doi.org/10.1016/j.combustflame.2014.07.003.

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Jeong, Hwanghui, and Keeman Lee. "Effect of Swirl Angles and Combustion Characteristics of Low Swirl Model Combustor." Journal of the Korean Society of Propulsion Engineers 20, no. 4 (August 1, 2016): 40–49. http://dx.doi.org/10.6108/kspe.2016.20.4.040.

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Wang, Y., W. Xu, H. Yin, Y. Zhang, and H. S. Dou. "Numerical study on the influence of pre-swirl angle on internal flow characteristics of centrifugal pumps." AIP Advances 12, no. 4 (April 1, 2022): 045019. http://dx.doi.org/10.1063/5.0085903.

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The effect of inlet pre-swirl on the performance of a centrifugal pump is studied by numerical simulation. The governing equations are Navier–Stokes equations and the shear stress transport k–ω turbulence model. The numerical results show that the optimal operating point moves from the low flow region to the high flow region as the pre-swirl angle shifts from positive to negative. It is found by contours of Omega–Liutex that the positive pre-swirl angle is able to weaken the vortex on the blade suction and reduce the energy dissipation. On both the 0.5Q0 and 1.2Q0 operating conditions, the proportion of entropy production loss in the impeller and volute is about 60% and 30%, respectively. As the pre-swirl angle changes from negative to positive, the entropy production loss in the inlet and outlet pipes increases slowly, and the entropy production loss in the volute and impeller shows a decreasing trend and the peak area of entropy loss moves toward the outlet. Under the four pre-swirl angles, the main frequency is always the passing frequency of the blade. The pre-swirl angle affects the pressure fluctuation at the main frequency but has little effect at the secondary frequency. The change in velocity pulsation amplitude in the impeller in the positive pre-swirl angle is smaller than that in the negative pre-swirl angle. As a result, for the positive pre-swirl angle, the turbulent kinetic energy density in the impeller is low, and the energy loss is low, compared with negative pre-swirl. Under the low flow condition (0.5Q0), the change in velocity pulsation amplitude in the inertial range of the energy spectrum under negative pre-swirl is greater than that under positive pre-swirl.

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Wang, Xuegao, Jun Hu, Jin Guo, Baofeng Tu, and Zhiqiang Wang. "An experimental investigation on the interaction between inlet swirl distortion and a low-speed axial compressor." Science Progress 103, no. 3 (July 2020): 003685042094092. http://dx.doi.org/10.1177/0036850420940920.

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The aim of this article mainly lies in two aspects. The first is to investigate the effect of inlet swirl distortion on the performance and stability of a low-speed compressor experimentally. The second is to quantify swirl pattern revolution through the compressor and find out background causes of the change in compressor performance. Swirl distortion makes the leading-edge incidence opposite between tip and hub regions, compared to that of clean flow. And the compressor performance change is ultimately determined by these two aspects. Results indicate that negative bulk swirl improves pressure rise, and the effect is on the contrary to the positive bulk swirl. Under the condition of paired swirl, pressure rise also presents a reduction. All these three types of swirl have little effect on the stall boundary. Although swirl distortion shows clear recovery at rotor exit, downstream components still work at off-design conditions due to the induced nonuniformity in axial velocity and total pressure.

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Balakrishnan, P., and K. Srinivasan. "Pipe jet noise reduction using co-axial swirl pipe." Aeronautical Journal 121, no. 1238 (March 6, 2017): 488–514. http://dx.doi.org/10.1017/aer.2017.5.

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ABSTRACTThe present experimental work highlights the acoustic far field and flow field characteristics of confined co-axial swirling pipe jets. Co-axial confinements with six vanes at angles of 0°, 20° and 40° are considered here. Two pipe lengths of L/D=0.5 and 2 are studied. The Mach numbers studied range from 0.85 to 1.83. An increase in the pipe length causes suppression of the transonic tones in non-swirl pipe jets. Swirl reduces the low frequency noise components and increases the high-frequency components compared to non-swirl jet. The broadband shock associated noise is mitigated by the swirl pipe jets. However, the screech tone is completely eliminated by the swirl pipe jets. Further, swirl pipe jets radiate low levels of noise at all the emission angles compared to non-swirl pipe jets, for both the pipe length cases at supersonic Mach numbers. Increase in the pipe length enhances the shock associated noise and OASPL for the non-swirl pipe jet. Centreline pitot survey and schlieren visualisation show a reduction in core length, reduction in the number of shock cells, weakening/destruction of the shock cells by the swirl pipe jets compared to the non-swirl pipe jets.

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Hsu, Yun, and Christopher E. Brennen. "Effect of Swirl on Rotordynamic Forces Caused by Front Shroud Pump Leakage." Journal of Fluids Engineering 124, no. 4 (December 1, 2002): 1005–10. http://dx.doi.org/10.1115/1.1511164.

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Unsteady forces generated by fluid flow through the impeller shroud leakage path of a centrifugal pump were investigated. The effect of leakage path inlet swirl (pump discharge swirl) on the rotordynamic forces was re-examined. It was observed that increasing the inlet swirl is destabilizing both for normal and tangential rotordynamic forces. Attempts to reduce the swirl within the leakage path using ribs and grooves as swirl brakes showed benefits only at low leakage flow rate.

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Kang, D. M., F. E. C. Culick, and A. Ratner. "Combustion dynamics of a low-swirl combustor." Combustion and Flame 151, no. 3 (November 2007): 412–25. http://dx.doi.org/10.1016/j.combustflame.2007.07.017.

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Li, Shuai, Yan Liu, Mohammad Omidi, Chuang Zhang, and Hongkun Li. "Numerical Investigation of Transient Flow Characteristics in a Centrifugal Compressor Stage with Variable Inlet Guide Vanes at Low Mass Flow Rates." Energies 14, no. 23 (November 25, 2021): 7906. http://dx.doi.org/10.3390/en14237906.

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This study numerically investigates the beneficial effects of positive pre-swirl on the aerodynamic performance and internal flow field in a centrifugal compressor stage with variable inlet guide vanes (VIGVs) at low mass flow rates. Four positions of VIGV are considered, including 0°, 30°, 45°, and 60° angle. The latter three positions of VIGV induce positive pre-swirl. Numerical results show that as positive pre-swirl increases, the aerodynamic performance curve of the stage moves in the low mass flow rate direction. In the three cases of positive pre-swirl, there was an improvement of approximately 9.95% of stall/surge margin greater than in conditions with no pre-swirl. The regulation of IGV can effectively improve the unstable flow of the compressor stage at low mass flow rates. A low frequency that has a great influence on the internal flow of the compressor stage is found, and the unstable flow caused by low frequency is analyzed by the combination of streamline distribution, spectrum analysis, vector, entropy increase, and modal decomposition method. Meanwhile, the modal decomposition method and flow field reconstruction techniques are used to investigate the coherent flow structures caused by low frequency under different guide vane openings.

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Більше джерел

Дисертації з теми "Low-swirl"

Spangelo, Øystein. "Experimental and Theoretical Studies of a Low Nox Swirl Burner." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-310.

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Nitrogen oxides emitted to the atmosphere can cause health problems for humans and environmental problems such as acid rain and global warming. The main part of the world energy consumption involves combustion; hence nitrogen oxide abatement in combustion is an important research field. Formation and reduction of NO_xin combustion and the current regulations on NO_x emissions are reviewed.

A novel low NO_xswirl stabilized gas burner concept, the Swirl Burner, has been studied experimentally, theoretically and numerically. Flame stabilization, rapid air and fuel mixing and internal flue gas recirculation are provided by a strongly swirling flow generated in this patented burner concept. NO_xemissions have been measured below 25 and 45 ppmv dry corrected to 3% O₂ in the flue gases using methane and propane as fuel respectively.

Studying the effect of varying geometrical parameters on the emissions of NO_x, fuel and air supply pressure and flame stability, have resulted in an optimized burner design. The optimized Swirl Burner has successfully been scaled from a 200 kW burner down to a 20 kW burner and up to a 370 kW burner, using a constant velocity scaling criteria which is the most commonly used scaling criteria for industrial burners. Experiments with the scaled burners have revealed that the fuel to air momentum should be preserved while scaling the burner. The 200 kW and the 370 kW burners were operated stable with the boiler to burner diameter (confinement) ratio in the range 5.3-6.7. The 20 kW burner, which was operated in an un-cooled and a water-cooled combustion chamber with confinement ratio of 8.1, was found to have a narrower range of stable operation with regards to thermal throughput. High post-flame heat extraction, which is enhanced by increased confinement ratio and combustion chamber cooling, reduces the emissions of NO_x, but might cause flame instabilities.

NO_x emissions measured from the three Swirl Burners scale well with NO_x scaling correlations based on flame volume as a leading-order parameter for NO_x formation (Weber, 1996). The correlations consider the effect of heat extraction on flame volume and emissions of NO_x. These correlations indicate that the heat extraction from the 20 kW burner is increasing with increasing thermal throughput. The 200 kW and the 370 kW burners were, from the correlations, found to operate with constant heat extraction.

Flame volume and shape are studied by non-intrusive measurements of OH radicals with the 20 kW burner using laser induced fluorescence. The measurements show that the flame volume is reduced with increasing thermal throughput. Measurements of NO_x from this burner also show a reduction with increasing thermal throughput. These results support the theoretical considerations of the flame volume as being the leading-order parameter for NO_xformation.

An evaluation of turbulence models and combustion models suitable for studying the Swirl Burner by computational fluid dynamics has been carried out. For this evaluation, a 2D computational model of the 20 kW burner has been used. For closure of the Reynolds Averaged Navier-Stokes equations for turbulent flow, three models have been evaluated.

These are the standard k-ε model, the RNG k-ε model and the Reynolds Stress model.

Also for modelling of combustion, three models have been evaluated, namely the Eddy Dissipation model, the Equilibrium PDF model and the Flamelet PDF model. For studying the Swirl Burner, a combination of the Reynolds Stress model and the Flamelet PDF model were found to be most suitable for modelling of turbulence and combustion respectively.

Computational results with the 20 kW burner indicate that flue gases are recirculated into a central toroidal recirculation zone downstream the burner exit. The computations are further compared with the OH concentrations measured with laser induced fluorescence.

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Endicott, Derick S. "Experimental Development of a Lean Direct Injection Combustor Utilizing High-Low Swirl Intensity Combinations." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416231599.

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Periagaram, Karthik Balasubramanian. "Determination of flame characteristics in a low swirl burner at gas turbine conditions through reaction zone imaging." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45828.

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This thesis explores the effects of operating parameters on the location and shape of lifted flames in a Low Swirl Burner (LSB). In addition, it details the development and analysis of a CH PLIF imaging system for visualizing flames in lean combustion systems. The LSB is studied at atmospheric pressure using LDV and CH PLIF. CH* chemiluminescence is used for high pressure flame imaging. A four-level model of the fluorescing CH system is developed to predict the signal intensity in hydrocarbon flames. Results from imaging an atmospheric pressure laminar flame are used to validate the behavior of the signal intensity as predicted by the model. The results show that the fluorescence signal is greatly reduced at high pressure due to the decreased number of CH molecules and the increased collisional quenching rate. This restricts the use of this technique to increasingly narrow equivalence ratio ranges at high pressures. The limitation is somewhat alleviated by increasing the preheat temperature of the reactant mixture. The signal levels from high hydrogen-content syngas mixtures doped with methane are found to be high enough to make CH PLIF a feasible diagnostic to study such flames. Finally, the model predicts that signal levels are unlikely to be significantly affected by the presence of strain in the flow field, as long as the flames are not close to extinction. The results from the LSB flame investigation reveal that combustor provides reasonably robust flame stabilization at low and moderate values of combustor pressure and reference velocities. However, at very high velocities and pressures, the balance between the reactant velocity and the turbulent flame speed shifts in favor of the former resulting in the flame moving downstream. The extent of this movement is small, but indicates a tendency towards blow off at higher pressures and velocities that may be encountered in real world gas turbine applications. There is an increased tendency of relatively fuel-rich flames to behave like attached flames at high pressure. These results raise interesting questions about turbulent combustion at high pressure as well as provide usable data to gas turbine combustor designers by highlighting potential problems.

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Emadi, Majid. "Flame structure and thermo-acoustic coupling for the low swirl burner for elevated pressure and syngas conditions." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/4968.

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Reduction of the pollutant emissions is a challenge for the gas turbine industry. A solution to this problem is to employ the low swirl burner which can operate at lower equivalence ratios than a conventional swirl burner. However, flames in the lean regime of combustion are susceptible to flow perturbations and combustion instability. Combustion instability is the coupling between unsteady heat release and combustor acoustic modes where one amplifies the other in a feedback loop. The other method for significantly reducing NOx and CO2 is increasing fuel reactivity, typically done through the addition of hydrogen. This helps to improve the flammability limit and also reduces the pollutants in products by decreasing thermal NOx and reducing CO2 by displacing carbon. In this work, the flammability limits of a low swirl burner at various operating conditions, is studied and the effect of pressure, bulk velocity, burner shape and percent of hydrogen (added to the fuel) is investigated. Also, the flame structure for these test conditions is measured using OH planar laser induced fluorescence and assessed. Also, the OH PLIF data is used to calculate Rayleigh index maps and to construct averaged OH PLIF intensity fields at different acoustic excitation frequencies (45-155, and 195Hz). Based on the Rayleigh index maps, two different modes of coupling between the heat release and the pressure fluctuation were observed: the first mode, which occurs at 44Hz and 55Hz, shows coupling to the flame base (due to the bulk velocity) while the second mode shows coupling to the sides of the flame. In the first mode, the flame becomes wider and the flame base moves with the acoustic frequency. In the second mode, imposed pressure oscillations induce vortex shedding in the flame shear layer. These vortices distort the flame front and generate locally compact and sparse flame areas. The local flame structure resulting from these two distinct modes was markedly different.

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Zejda, Vojtěch. "Měření rychlostních profilů za vířičem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232121.

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A burner is very important device in process furnaces that significantly affect the production of emissions during the combustion process. One of the key things in development of the modern low-NOX burners is the evaluation of flow field downstream of an axial blade swirler inside the burner. The computational fluid dynamics (CFD) is often used to predict the attributes of the flow. Predicted values should be validated with measurement. It is the reason why the velocity fields for several choosen swirlers were measured. The hot wire anemometry was choosen and the dual-sensor probe was used during the measurement. The data can be then used for CFD validation. This thesis describes procedure of measurement set-up. The experimental facility was designed according to the anemometry method. The new probe traversing system was designed, which provides desired accuracy. Five different swirlers were measured. Large data set, need for customized post-processing and control over calculation procedures lead to new software design. For each swirler the velocity profiles were gathered and the swirl numbers calculated. That final data were transferred in to graphical format. Uncertainty of measured data was calculated. Results show counter-rotating flow in some areas closed to the swirler. Some drawbacks of current measurement set-up are discussed. Based on the thesis reader can obtain the information and knowledge for consequent measurements of swirl burners velocity profiles.

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Kaufman, Kelsey Leigh. "Effect of hydrogen addition and burner diameter on the stability and structure of lean, premixed flames." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4661.

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Low swirl burners (LSBs) have gained popularity in heating and gas power generation industries, in part due to their proven capacity for reducing the production of NOx, which in addition to reacting to form smog and acid rain, plays a central role in the formation of the tropospheric ozone layer. With lean operating conditions, LSBs are susceptible to combustion instability, which can result in flame extinction or equipment failure. Extensive work has been performed to understand the nature of LSB combustion, but scaling trends between laboratory- and industrial-sized burners have not been established. Using hydrogen addition as the primary method of flame stabilization, the current work presents results for a 2.54 cm LSB to investigate potential effects of burner outlet diameter on the nature of flame stability, with focus on flashback and lean blowout conditions. In the lean regime, the onset of instability and flame extinction have been shown to occur at similar equivalence ratios for both the 2.54 cm and a 3.81 cm LSB and depend on the resolution of equivalence ratios incremented. Investigations into flame structures are also performed. Discussion begins with a derivation for properties in a multicomponent gas mixture used to determine the Reynolds number (Re) to develop a condition for turbulent intensity similarity in differently-sized LSBs. Based on this requirement, operating conditions are chosen such that the global Reynolds number for the 2.54 cm LSB is within 2% of the Re for the 3.81 cm burner. With similarity obtained, flame structure investigations focus on flame front curvature and flame surface density (FSD). As flame structure results of the current 2.54 cm LSB work are compared to results for the 3.81 cm LSB, no apparent relationship is shown to exist between burner diameter and the distribution of flame surface density. However, burner diameter is shown to have a definite effect on the flame front curvature. In corresponding flow conditions, a decrease in burner diameter results a broader distribution of curvature and an increased average curvature, signifying that compared to the larger 3.81 cm LSB, the flame front of the smaller burner contains tighter, smaller scale wrinkling.

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Dawson, Dylan Paul. "Design and Low-Speed Validation of a Tailored Low-Loss Flow Straightening Device." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/97888.

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In many applications, non-uniform flows are undesirable and have a negative system impact. Non-uniform flows can arise in many ways such as in geometry changes and turns in piping/ducting, as well as with lip separation in certain aircraft engine inlets at high angle of attack. These non-uniformities can come with a variety of secondary flow patterns and thus highly three-dimensional flow. In a cylindrical coordinate system, these secondary (or in-plane) velocities have tangential and radial components. The tangential velocity is typically referred to as swirl and is the component of secondary flow that has the most system impact. These systems include industrial compressors, aircraft engines, and flow metering devices. In industrial compressors and aircraft engines, swirl translates into off-design incidence angles on the blades. The off-design incidence can lead to blade stall, losses in performance, and loss in system operability. In flow metering, swirl can significantly reduce measurement accuracy, and is regulated in industries such as the oil and gas industry. In the straightening of low-speed flows with approximately constant density and axial velocity, the velocity magnitude decreases and pressure increases along streamlines. This creates an unfavorable streamwise pressure gradient that inhibits the fluids ability to remain attached to the convex suction surface of the turning vane. This suction side separation causes the flow to under turn and exit at an angle not equal to the vane's trailing edge angle. The angle measured between the vane's trailing edge and the actual exiting flow angle is referred to as the deviation. Research on specific airfoil shaped turning vanes set up in linear cascade arrangements provides experimental data detailing the deviation measured at ranges of inlet flow conditions and vane spacing. These experimental data sets indicate that deviation angles were measured to be 10 degrees or higher in large vane spacing, high design flow turning arrangements. It is evident that in order to effectively straighten flow with turning vanes, the deviation must be predicted and accounted for in the design stage. In this work, the design system of a new method of swirl mitigation is detailed and experimentally validated in a low-speed wind tunnel. The design system builds upon the fundamentals of the swirl-producing StreamVane design methods and is thus designated as the Inverse StreamVane. The complex arrangement of turning vanes in the StreamVane and Inverse StreamVane alike creates a spanwise variation of vane spacing. Calculated by a proximity approximation method, this local vane spacing, along with the local inlet flow conditions, become inputs to a derived function that predicts the local flow deviation. A root-finding method is utilized at each incremental vane section of each turning vane to converge on the design cambers that set the predicted local deviation angles equal to the local trailing edge angles. Experimental and computational results validate the design method employed with the reduction of an experimentally measured 30 degree peak paired swirl profile to a 3 degree peak, 1.01 degree rms, swirl profile. Flow angularity and loss measurements detailed at 1/2 duct diameter downstream of the 1/6 duct diameter axial length of the device introduce the Inverse StreamVane as a very effective and efficient method of swirl mitigation.
MS

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Cejpek, Ondřej. "Návrh a realizace aerodynamického tunelu pro rozstřikovací trysky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417116.

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Pracovní podmínky atomizérů v reálných operacích v průmyslu a zemědělství se liší od podmínek laboratorních, ve kterých jsou atomizéry testovány. Částečné přiblížení k realističtějším podmínkám nám může poskytnout použití větrného tunelu. Větrný tunel se používá k simulaci okolního proudění. Studium spreje ve větrném tunelu nám poskytne realističtější představu o chování spreje. Tato diplomová práce se zabývá návrhem malého, nízko rychlostního větrného tunelu pro experimenty s tlakovými vířivými tryskami s obtokem v příčném a podélném proudění. Existuje mnoho typů větrných tunelů, ale jako nejvhodnější typ byl zvolen otevřený, výtlačný větrný tunel s uzavřenou testovací sekcí. Výhodou jsou jeho kompaktní rozměry, ochrana částí tunelu před kapičkami spreje a poměrně jednoduchý návrh. Konstrukce větrného tunelu se skládá z několika částí, každá část je zkonstruována tak, aby bylo dosaženo co nejlepší kvality proudu v testovací sekci. Sprej je zkoumán pomocí optických metod Fázové Dopplerovské anemometrie (PDA), Laserové Dopplerovské anemometrie (LDA), Integrální laserová anemometrie (PIV) a pomocí vysokorychlostního záznamu. Tyto optické metody kladou speciální požadavky na konstrukci tunelu, především na konstrukci testovací sekce, která musí umožňovat optický přístup ke spreji a musí být pro tyto měřící techniky uzpůsobena. Rychlost v testovací sekci se pohybuje v rozmezí 0 až 40 m/s s intenzitou turbulence pod 0,7 %. V závěru práce je ukázka vizualizace spreje, v příčném proudění, pomocí vysokorychlostní kamery. Okolní proudění mění rozpadovou vzdálenost spreje, úhel kužele spreje i jeho tvar. Dochází k vymývání menších kapek, které jsou unášeny okolním proudem.

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Marshall, Andrew. "Turbulent flame propagation characteristics of high hydrogen content fuels." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53859.

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Increasingly stringent pollution and emission controls have caused a rise in the use of combustors operating under lean, premixed conditions. Operating lean (excess air) lowers the level of nitrous oxides (NOx) emitted to the environment. In addition, concerns over climate change due to increased carbon dioxide (CO2) emissions and the need for energy independence in the United States have spurred interest in developing combustors capable of operating with a wide range of fuel compositions. One method to decrease the carbon footprint of modern combustors is the use of high hydrogen content (HHC) fuels. The objective of this research is to develop tools to better understand the physics of turbulent flame propagation in highly stretch sensitive premixed flames in order to predict their behavior at conditions realistic to the environment of gas turbine combustors. This thesis presents the results of an experimental study into the flame propagation characteristics of highly stretch-sensitive, turbulent premixed flames generated in a low swirl burner (LSB). This study uses a scaling law, developed in an earlier thesis from leading point concepts for turbulent premixed flames, to collapse turbulent flame speed data over a wide range of conditions. The flow and flame structure are characterized using high speed particle image velocimetry (PIV) over a wide range of fuel compositions, mean flow velocities, and turbulence levels. The first part of this study looks at turbulent flame speeds for these mixtures and applies the previously developed leading points scaling model in order to test its validity in an alternate geometry. The model was found to collapse the turbulent flame speed data over a wide range of fuel compositions and turbulence levels, giving merit to the leading points model as a method that can produce meaningful results with different geometries and turbulent flame speed definitions. The second part of this thesis examines flame front topologies and stretch statistics of these highly stretch sensitive, turbulent premixed flames. Instantaneous flame front locations and local flow velocities are used to calculate flame curvatures and tangential strain rates. Statistics of these two quantities are calculated both over the entire flame surface and also conditioned at the leading points of the flames. Results presented do not support the arguments made in the development of the leading points model. Only minor effects of fuel composition are noted on curvature statistics, which are mostly dominated by the turbulence. There is a stronger sensitivity for tangential strain rate statistics, however, time-averaged values are still well below the values hypothesized from the leading points model. The results of this study emphasize the importance of local flame topology measurements towards the development of predictive models of the turbulent flame speed.

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Paštěka, František. "Projekt malé vodní elektrárny pro konkrétní lokalitu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228743.

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This master's thesis is specialised in designing of small hydropower plant for specific location. In work should be designed suitable turbine for parameters found on the site, then created a basic project documentation of small hydropower plant with all devices and used principles, so that the plant would be capable of operation. In the next part of thesis should be extented the calculation of flow in the turbine delivery and assessed effect of geometry of turbine delivery on the flow.

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Книги з теми "Low-swirl"

Center, Ames Research, ed. SWIRL as a means of liquid management in low gravity. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1993.

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National Aeronautics and Space Administration (NASA) Staff. Swirl As a Means of Liquid Management in Low Gravity. Independently Published, 2018.

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Rai, Dibya Prakash, ed. Advanced Materials and Nano Systems: Theory and Experiment - Part 2. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/97898150499611220201.

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The discovery of new materials and the manipulation of their exotic properties for device fabrication is crucial for advancing technology. Nanoscience, and the creation of nanomaterials have taken materials science and electronics to new heights for the benefit of mankind. Advanced Materials and Nanosystems: Theory and Experiment covers several topics of nanoscience research. The compiled chapters aim to update students, teachers, and scientists by highlighting modern developments in materials science theory and experiments. The significant role of new materials in future technology is also demonstrated. The book serves as a reference for curriculum development in technical institutions and research programs in the field of physics, chemistry and applied areas of science like materials science, chemical engineering and electronics. This part covers 12 topics in these areas: 1. Recent advancements in nanotechnology: a human health Perspective 2. An exploratory study on characteristics of SWIRL of AlGaAs/GaAs in advanced bio based nanotechnological systems 3. Electronic structure of the half-Heusler ScAuSn, LuAuSn and their superlattice 4. Recent trends in nanosystems 5. Improvement of performance of single and multicrystalline silicon solar cell using low-temperature surface passivation layer and antireflection coating 6. Advanced materials and nanosystems 7. Effect of nanostructure-materials on optical properties of some rare earth ions doped in silica matrix 8. Nd2Fe14B and SmCO5: a permanent magnet for magnetic data storage and data transfer technology 9. Visible light induced photocatalytic activity of MWCNTS decorated sulfide based nano photocatalysts 10. Organic solar cells 11. Neodymium doped lithium borosilicate glasses 12. Comprehensive quantum mechanical study of structural features, reactivity, molecular properties and wave function-based characteristics of capmatinib

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Частини книг з теми "Low-swirl"

Grigoryev, K. A., Yu A. Roundyguine, V. E. Skuditskii, R. G. Anoshin, A. P. Paramonov, and A. A. Trinchenko. "Low-Temperature Swirl Fuel Combustion: Development and Experience." In Cleaner Combustion and Sustainable World, 999–1003. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-30445-3_133.

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Fuchs, L. "Some Characteristics of Non-Reacting and Reacting Low Swirl Number Jets." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14139-3_1.

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Bian, Jiang, Xuewen Cao, Yang Liu, Yuan Sun, and Qi Chu. "Influence of Swirl Vane on the Low-Pressure Gas Flow in Supersonic Separators." In Proceedings of the International Field Exploration and Development Conference 2018, 1841–49. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-7127-1_174.

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Zhang, Xin-ai, and Hai-bin Tang. "The Effects of Swirl on Low Power Arcjet Thruster Flowfield and Heat Transfer Characteristics." In Lecture Notes in Electrical Engineering, 1948–68. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-3305-7_158.

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Sahu, Nitesh Kumar, Mayank Kumar, and Anupam Dewan. "A Computational Study of Entrained Flow Furnace with Swirl Burner Configuration and Low Turbulence Intensity Flow." In Lecture Notes in Mechanical Engineering, 73–80. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0698-4_8.

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Iavarone, S., H. Yang, Z. Li, Z. X. Chen, and N. Swaminathan. "On the Use of Machine Learning for Subgrid Scale Filtered Density Function Modelling in Large Eddy Simulations of Combustion Systems." In Lecture Notes in Energy, 209–43. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-16248-0_8.

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AbstractThe application of machine learning algorithms to model subgrid-scale filtered density functions (FDFs), required to estimate filtered reaction rates for Large Eddy Simulation (LES) of chemically reacting flows, is discussed in this chapter. Three test cases, i.e., a low-swirl premixed methane-air flame, a MILD combustion of methane-air mixtures, and a kerosene spray turbulent flame, are presented. The scalar statistics in these test cases may not be easily represented using the commonly used presumed shapes for modeling FDFs of mixture fraction and progress variable. Hence, the use of ML methods is explored. Particularly, deep neural network (DNN) to infer joint FDFs of mixture fraction and progress variable is reviewed here. The Direct Numerical Simulation (DNS) datasets employed to train the DNNs in each test case are described. The DNN performances are shown and compared to typical presumed probability density function (PDF) models. Finally, this chapter examines the advantages and caveats of the DNN-based approach.

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Trinchenko, Aleksey, and Aleksandr Paramonov. "Low-Temperature Swirl Burning as Technological Method of Simultaneous Decrease in Emissions of Nitrogen and Sulfur Oxides (Part 1. Principles, Organization and Mathematical Model of Furnace Process)." In International Scientific Conference Energy Management of Municipal Transportation Facilities and Transport EMMFT 2017, 1074–82. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-70987-1_116.

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Trinchenko, Aleksey, and Aleksandr Paramonov. "Low-Temperature Swirl Burning as Technological Method of Simultaneous Decrease in Emissions of Nitrogen and Sulfur Oxides (Part 2. Results of Modeling, Their Practical Implementation and Analysis)." In International Scientific Conference Energy Management of Municipal Transportation Facilities and Transport EMMFT 2017, 1083–92. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-70987-1_117.

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Froud, D. Y., W. Fick, P. J. Bowen, T. O'Doherty, and N. Syred. "CHARACTERISATION OF INDUSTRIAL SWIRL BURNERS FOR EFFICIENT COMBUSTION OF LOW CALORIFIC VALUE GASES." In The Institute of Energy's Second International Conference on Combustion & Emissions Control, 239–48. Elsevier, 1995. http://dx.doi.org/10.1016/b978-0-902597-49-5.50026-3.

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Han, Yong Oun, and Young Soo Kim. "Correlating structure of tip vortices and swirl flows induced by a low aspect ratio rotor blade." In Engineering Turbulence Modelling and Experiments 4, 471–80. Elsevier, 1999. http://dx.doi.org/10.1016/b978-008043328-8/50045-x.

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Тези доповідей конференцій з теми "Low-swirl"

Escandon, Rodrigo, Randall D. Manteufel, and Q. Ken Su. "Enhanced Low-Pressure Pneumatic Conveyance Using Swirl." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39432.

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Two designs for swirl amplification have been considered for pneumatic conveyance in vertical pipes. Both designs have been experimentally evaluated in order to predict their capability. The designs have been compared to other methods of amplification or swirl generation. The motivation for the swirl in pneumatic conveyance is to minimize axial velocity by using multiple swirl amplifications to enhance the transportation for long distances. In this experimental evaluation two swirl amplifiers are considered. The evaluations are done by determining the static pressures before and after the swirl amplifier in the vertical section of an experimental system. This difference in pressure points allowed the determination of length of decay, which is the distance in which this two-phase system travels before a reduction in radial velocity. In the amplifiers, compressed air at two pressures was used for the purpose of creating a low pressure pneumatic conveying system. It is determined that when using these amplifications in the air boost, longer lengths of decay can be achieved in comparison to a no swirl system. This meant that the products transportation could be enhanced due to the addition of the swirl amplifiers. The experimental values were used to compare both designs. The more productive one was determined by its length of decay. As well as estimating the maximum obtainable distances for both swirl amplifiers at each particular amplification.

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Sequera, Daniel, and Ajay Agrawal. "Emissions and Acoustics Measurements in a Low-Swirl Burner." In 45th AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2007. http://dx.doi.org/10.2514/6.2007-1347.

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Sakurai, Shigeru, and Tsutomu Matsuoka. "Development of Low Particulate Engine with Ceramic Swirl Chamber." In Passenger Car Meeting & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1986. http://dx.doi.org/10.4271/861407.

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Deng, Yangbo, Luohan Zheng, Fengmin Su, and Chenshuo Ma. "Combustion Characteristic of Flow Through a Low Swirl Injector." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65957.

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An experimental study was carried out in order to provide a better understanding of the combustion characteristics of a low swirl injector (LSI). The swirl vanes angles are respectively 37°, 42° and 50°, and the swirl numbers are varied in a wide range. The fuel gases used in the experiment include propane, methane and methane with hydrogen. The results show: (1) the lean premixed propane, methane, methane with hydrogen and air flow through the LSI can sustain steady combustion at a lower swirl number; (2) the LSIs can generate a blue lift-off “W” type flames surrounding a long yellow pulsating flame and the blue flame consists of four clusters blue flames connected together along circumferential direction; (3) the flame structure converts the “W” type flame into the “broom” type flame with the pulsating yellow flame, and the distance between the front of the flame and the nozzle shortens with increasing swirl number in the same vane angle case; (4) the spectroscopic of the flame shows the yellow flames are emitted by diatomic carbon.

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Dawson, James, Victor Rodriguez-Martinez, Nick Syred, and Tim O'Doherty. "Low-frequency Combustion Oscillations in a Swirl Burner/furnace." In 42nd AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2004. http://dx.doi.org/10.2514/6.2004-811.

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Littlejohn, David, Robert K. Cheng, D. R. Noble, and Tim Lieuwen. "Laboratory Investigations of Low-Swirl Injectors Operating With Syngases." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51298.

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The low-swirl injector (LSI) is a lean premixed combustion technology that has the potential for adaptation to fuel-flexible gas turbines operating on a variety of fuels. The objective of this study is to gain a fundamental understanding of the effect of syngas on the LSI flame behavior, the emissions and the flowfield characteristics for its adaptation to the combustion turbines in IGCC clean coal power plants. The experiments were conducted in two facilities. Open laboratory flames generated by a full size (6.35 cm) LSI were used to investigate the lean-blow off limits, emissions, and the flowfield characteristics. Verification of syngas operation at elevated temperatures and pressures were performed with a reduced scale (2.54 cm) LSI in a small pressurized combustion channel. The results show that the basic LSI design is amenable to burning syngases with up to 60% H2. Syngases with high H2 concentration have lower lean blow-off limits. From PIV measurements, the flowfield similarity behavior and the turbulent flame speeds of syngases flames are consistent with those observed in hydrocarbon and pure or diluted hydrogen flames. The NOx emissions from syngas flames show log-linear dependency on the adiabatic flame temperature and are comparable to those reported for the gaseous fuels reported previously. Successful firing of the reduced-scale LSI at 330 < T < 446° F and 8 atm verified the operability of this concept at gas turbine conditions.

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Deng, Yangbo, Jingming Dong, and Xu Zhen. "Study on Flow Field Characteristics of Low Swirl Injector." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37423.

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The flow characteristics of six kinds of LSIs, which are designed by different pore sizes in the center channel screen, are analyzed. The velocity vectors on the spanwise sections and the vertical sections in a channel at atmospheric condition are captured using a Particle Image Velocimetry (PIV) system. The swirl number of the airflow through the LSIs ranges from 0.5 to 0.58, and the inlet velocity is kept at 14m/s. The results show that the swirl number under a threshold can form low swirl flow. The velocity vector distribution of the low swirl flow is a diffuse shape without recirculation, and has the self-similar characteristic. The separation of low speed flow in the center zone and the high speed in the annulus zone generates the unique “W” shape distribution of the through the LSI. With the swirl number increasing, the area of the low vorticity zone decreases, and the vorticity value of the flow in the outer annular zone increases.

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Yadav, N. P., and Abhijit Kushari. "Turbulent Behaviour in a Low Aspect Ratio Dump Combustor at Low Swirl Number." In ASME 2013 Gas Turbine India Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gtindia2013-3734.

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This paper reports an experimental investigation of a non-reacting flow in a low aspect ratio dump combustor with taper exit. The separated flow reattachment length for this combustor was higher than the length of the combustor. In order to understand the flow behavior inside the combustor, the velocity measurement inside the combustor was carried out by calibrated one-dimensional hot wire probes for the same flow conditions. The turbulent intensity variation inside the combustor without swirl flow was found to be axi-symmetric. The turbulence intensity along the centre line is lower than at other radial locations because of the presence of the potential core. The intensity in the core region increases as one moves along the centerline in the axial direction, which can be attributed to the weakening of the potential core and the increase in the extent of the shear layer. The turbulence behavior significantly changed with the use of a swirler at the inlet of the combustor. The intensity variation inside the combustor is more uniform than the low swirl number SN = 0.23. The higher turbulence kinetic energy and turbulent dissipation rate was observed at this swirl number. Therefore, the effect of swirl is expected to improve the combustion through better mixing and flame stabilization.

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Funk, Charles, Volker Sick, David L. Reuss, and Werner J. A. Dahm. "Turbulence Properties of High and Low Swirl In-Cylinder Flows." In SAE Powertrain & Fluid Systems Conference & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2002. http://dx.doi.org/10.4271/2002-01-2841.

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Therkelsen, Peter L., David Littlejohn, and Robert K. Cheng. "Parametric Study of Low-Swirl Injector Geometry on its Operability." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68436.

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The low swirl injector (LSI) is a combustion technology being developed for low-emissions fuel-flexible gas turbines. The basic LSI configuration consists of an annulus of swirl vanes centered on a non-swirled channel, both of which allow for the passage of premixed reactants. LSIs are typically designed by following a general guidance of achieving a swirl number between 0.4 and 0.55. This paper aims to develop a more specific guideline by investigating the effects of varying geometry, i.e. vane angle, vane shape, and center channel size, on the LSI performance. A well-studied LSI provides a baseline for this investigation. Nine LSI variations from this baseline design have been evaluated. All LSI are tested with CH4 fuel at bulk flow velocity of 8 to 20 m/s firing into the open atmosphere. Performance metrics are the lean blowoff limit, the pressure drop, flowfield characteristics and emissions. Results show that the lean blow-off limit and NOx and CO emissions are insensitive to LSI geometric variations. The flowfields of seven LSIs exhibit self-similarity implying their turndown ranges are similar. Reducing the center channel size and/or the use of thin vanes instead of thickened vanes can reduce pressure drop across the LSI. Additionally, all ten LSI share a common feature in that 70% to 80% the premixture flows through the vane annulus. These findings are used to develop a more specific engineering guidelines for designing the LSI for gas turbines.

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Звіти організацій з теми "Low-swirl"

Ala Qubbaj. SIMULATION MODELING OF AN ENHANCED LOW-EMISSION SWIRL-CASCADE BURNER. Office of Scientific and Technical Information (OSTI), April 2004. http://dx.doi.org/10.2172/838121.

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Ala Qubbaj. SIMULATION MODELING OF AN ENHANCED LOW-EMISSION SWIRL-CASCADE BURNER. Office of Scientific and Technical Information (OSTI), April 2003. http://dx.doi.org/10.2172/822877.

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Ala Qubbaj. SIMULATION MODELING OF AN ENHANCED LOW-EMISSION SWIRL-CASCADE BURNER. Office of Scientific and Technical Information (OSTI), October 2003. http://dx.doi.org/10.2172/822878.

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Ala Qubbaj. Simulation Modeling of an Enhanced Low-Emission Swirl-Cascade Burner. Office of Scientific and Technical Information (OSTI), September 2004. http://dx.doi.org/10.2172/875407.

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Rapp, Vi H., Robert K. Cheng, and Peter L. Therkelsen. A high turndown, ultra low emission low swirl burner for natural gas, on-demand water heaters. Office of Scientific and Technical Information (OSTI), June 2017. http://dx.doi.org/10.2172/1363643.

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Yegian, D. T., and R. K. Cheng. Development of a vane-swirler for use in a low NO{sub x} weak-swirl burner. Office of Scientific and Technical Information (OSTI), October 1996. http://dx.doi.org/10.2172/414339.

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