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Artykuły w czasopismach na temat "Exhaust valve opening"
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Wang, Xinyan, Jun Ma i Hua Zhao. "Analysis of scavenge port designs and exhaust valve profiles on the in-cylinder flow and scavenging performance in a two-stroke boosted uniflow scavenged direct injection gasoline engine". International Journal of Engine Research 19, nr 5 (10.08.2017): 509–27. http://dx.doi.org/10.1177/1468087417724977.
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In this study, effects of intake scavenge port designs and exhaust valve opening profiles were studied on the scavenging process in a newly proposed two-stroke boosted uniflow scavenged direct injection gasoline engine by detailed three-dimensional engine simulations. As the most important geometric parameters, the axis inclination angle and swirl orientation angle of scavenge ports, as shown in Figure 1, were investigated and optimized for best scavenging performances at first. With the optimal axis inclination angle of 90° and swirl orientation angle of 20°, various combinations of scavenge port opening timing, exhaust valve opening duration and exhaust valve opening timing were then analysed. Four distinct scavenging periods, that is, early backflow period, backflow scavenging period, main scavenging period and post backflow period, were identified and their impacts on the in-cylinder flow motions and scavenging performances were investigated. The results show that the optimal scavenging performance can be achieved with a higher delivery ratio, charging efficiency and scavenging efficiency when the post backflow is just avoided by tuning the difference between the closing timings of scavenge ports and exhaust valves (Δ close) and the overlap between the opening profiles of scavenge ports and exhaust valves (Δ overlap) for a specific exhaust valve opening duration. A longer exhaust valve opening duration can be used to further improve the scavenging performances. In addition, the difference between the opening timings of scavenge ports and exhaust valves (Δ open) can be increased to improve scavenging efficiency. The Δ close also shows strong positive correlation with in-cylinder swirl ratio and negative correlation with tumble ratio. The results presented in this study provide the fundamental knowledge of the scavenging process in the uniflow scavenged two-stroke engine and assist the design of scavenge ports and valve strategies to optimize in-cylinder flow motion and scavenge performances in the two-stroke boosted uniflow scavenged direct injection gasoline engine with a variable valve actuation system for exhaust valves.
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Romandoni, Nanang, Noorsakti Wahyudi, Kholis Nur Faizin i Firdho Putra Fadillah. "KADAR EMISI GAS BUANG PADA SI ENGINE 4 STROKE-LPG FUEL DENGAN VARIASI BUKAAN KATUP GAS". Jurnal Mekanova: Mekanikal, Inovasi dan Teknologi 8, nr 1 (19.04.2022): 42. http://dx.doi.org/10.35308/jmkn.v8i1.5365.
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Abstract The use of LPG fuel in spark ignition engines continues to be developed, including the use of converter kits as a conversion tool from gasoline to LPG. However, the use of converter kits is not optimal because the mixture of air and gas has not been mixed heterogeneously in the combustion chamber. Therefore, it is necessary to redesign the converter kits that speed up the mixing process between air and gas. This study aims to evaluate the use of LPG fuel in spark ignition engines with converter kits on variations in throttle valve openings on exhaust gas emissions and exhaust gas temperatures. The research method used is an experiment with variations in the throttle valve opening on the engine are 25%, 50%, 75%, and 100%. Data that will be compared on the use of gasoline and LPG fuels include carbon monoxide (CO), hydrocarbon (HC), and mean gas temperature. The results showed that the use of fuel between gasoline and LPG on exhaust gas emission levels in spark ignition engines with variations in throttle valve openings was able to reduce CO emissions by 92% on average, HC by 72%, and increase the mean average temperature by 17%. This shows that the use of converter kits at each valve opening is able to reduce levels of CO and HC exhaust emissions compared to gasoline. However, it is inversely proportional to the mean gas temperature, at each variation of the gas valve opening there is a significant increase in temperature. This is because the heating value of LPG is greater than that of gasoline.Keywords—Exhaust gas emission, spark ignition engine, throttle valve open
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Vos, Kalen R., Gregory M. Shaver, Mrunal C. Joshi i James McCarthy. "Implementing variable valve actuation on a diesel engine at high-speed idle operation for improved aftertreatment warm-up". International Journal of Engine Research 21, nr 7 (16.10.2019): 1134–46. http://dx.doi.org/10.1177/1468087419880639.
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Aftertreatment thermal management is critical for regulating emissions in modern diesel engines. Elevated engine-out temperatures and mass flows are effective at increasing the temperature of an aftertreatment system to enable efficient emission reduction. In this effort, experiments and analysis demonstrated that increasing the idle speed, while maintaining the same idle load, enables improved aftertreatment “warm-up” performance with engine-out NOx and particulate matter levels no higher than a state-of-the-art thermal calibration at conventional idle operation (800 rpm and 1.3 bar brake mean effective pressure). Elevated idle speeds of 1000 and 1200 rpm, compared to conventional idle at 800 rpm, realized 31%–51% increase in exhaust flow and 25 °C–40 °C increase in engine-out temperature, respectively. This study also demonstrated additional engine-out temperature benefits at all three idle speeds considered (800, 1000, and 1200 rpm, without compromising the exhaust flow rates or emissions, by modulating the exhaust valve opening timing. Early exhaust valve opening realizes up to ~51% increase in exhaust flow and 50 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder via an early blowdown of the exhaust gas. This early blowdown of exhaust gas also reduces the time available for particulate matter oxidization, effectively limiting the ability to elevate engine-out temperatures for the early exhaust valve opening strategy. Alternatively, late exhaust valve opening realizes up to ~51% increase in exhaust flow and 91 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder to pump in-cylinder gases across a smaller exhaust valve opening. In short, this study demonstrates how increased idle speeds, and exhaust valve opening modulation, individually or combined, can be used to significantly increase the “warm-up” rate of an aftertreatment system.
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Jiang, Da Hua, An Gui Li, Fa En Shi i Yu Jiao Zhao. "Test Analysis on Flow Field of Exhaust Hood in Commercial Kitchen". Advanced Materials Research 374-377 (październik 2011): 560–63. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.560.
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Making exhaust hood model in laboratory according to exhaust hood in commercial kitchen, steam instead of fume, and characteristics of flow field are studied in kitchen exhaust hood. The distribution of velocity and temperature at typical planes was measured at valve opening of 45 degrees when water boiling. Results show that in a certain range, air velocity of exhaust hood decreases when air from the exhaust opening distance increases, velocity reduces with x and y increasing, steam velocity reaches maximum value close to exhaust outlet of fan.
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Park, Cheolwoong, Wonah Park, Yongrae Kim, Young Choi i Byeungjun Lim. "Effect of Valve Timing and Excess Air Ratio on Torque in Hydrogen-Fueled Internal Combustion Engine for UAV". Energies 12, nr 5 (26.02.2019): 771. http://dx.doi.org/10.3390/en12050771.
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In this study, in order to convert a 2.4 L reciprocating gasoline engine into a hydrogen engine an experimental device for supplying hydrogen fuel was installed. Additionally, an injector that is capable of supplying the hydrogen fuel was installed. The basic combustion characteristics, including torque, were investigated by driving the engine with a universal engine control unit. To achieve stable combustion and maximize output, the intake and exhaust valve opening times were changed and the excess air ratio of the mixture was controlled. The changes in the torque, excess air ratio, hydrogen fuel, and intake airflow rate, were compared under low engine speed and high load (wide open throttle) operating conditions without throttling. As the intake valve opening time advanced at a certain excess air ratio, the intake air amount and torque increased. When the opening time of the exhaust valve was retarded, the intake airflow rate and torque decreased. The torque and thermal efficiency decreased when the opening time of the intake and exhaust valve advanced excessively. The change of the mixture condition’s excess air ratio did not influence the tendency of the torque variation when the exhaust valve opening time and torque increased, and when the mixture became richer and the intake valve opening time was fixed. Under a condition that was more retarded than the 332 CAD condition, the torque decreased by about 2 Nm with the 5 CAD of intake valve opening time retards. The maximum torque of 138.1 Nm was obtained at an optimized intake and the exhaust valve opening time was 327 crank angle degree (CAD) and 161 CAD, respectively, when the excess air ratio was 1.14 and the backfire was suppressed. Backfire occurred because of the temperature increase in the combustion chamber rather than because of the change in the fuel distribution under the rich mixture condition, where the other combustion control factors were constantly fixed from a three-dimensional (3D) computational fluid dynamics (CFD) code simulation.
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Joshi, Mrunal C., Dheeraj Gosala, Gregory M. Shaver, James McCarthy i Lisa Farrell. "Exhaust valve profile modulation for improved diesel engine curb idle aftertreatment thermal management". International Journal of Engine Research 22, nr 10 (9.04.2021): 3179–95. http://dx.doi.org/10.1177/1468087420969101.
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Rapid warm-up of a diesel engine aftertreatment system (ATS) is a challenge at low loads. Modulating exhaust manifold pressure (EMP) to increase engine pumping work, fuel consumption, and as a result, engine-outlet temperature, is a commonly used technique for ATS thermal management at low loads. This paper introduces exhaust valve profile modulation as a technique to increase engine-outlet temperature for ATS thermal management, without requiring modulation of exhaust manifold pressure. Experimental steady state results at 800 RPM/1.3 bar BMEP (curb idle) demonstrate that early exhaust valve opening with negative valve overlap (EEVO+NVO) can achieve engine-outlet temperature in excess of 255°C with 5.7% lower fuel consumption, 12% lower engine out NOx and 20% lower engine-out soot than the conventional thermal management strategy. Late exhaust valve opening with internal EGR via reinduction (LEVO+Reinduction) resulted in engine-outlet temperature in excess of 280°C, while meeting emission constraints at no fuel consumption penalty. This work also demonstrates that LEVO in conjunction with modulation of exhaust manifold pressure results in engine-outlet temperature in excess of 340°C while satisfying desired emission constraints. Aggressive use of LEVO can result in engine-outlet temperatures of 460°C, capable of active regeneration of DPF at curb idle, without the significant increase in engine-out soot emissions seen in previously studied strategies.
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Luo, Qing Guo, Hong Bin Liu i Qiang Ma. "Study on Optimization of the Diesel Engine Controlling Parameters Based on Genetic Algorithm". Applied Mechanics and Materials 253-255 (grudzień 2012): 2125–29. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.2125.
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The diesel engine simulation model build by the GT-POWER software was tested and verified. The advance angle of injection, the opening angle of intake valve and the opening angle of exhaust valve was calculated to get the virtual test sample of diesel engine running under the rated condition. The optimization model was built based on the genetic algorithm, and three parameters were optimized aimed at the economic efficiency under the constraint of the maximum pressure in cylinder and the exhaust temperature; the error between the optimization and the simulation result was below 3%.
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Poljak, Igor, Ivica Glavan i Toma Ribičić. "Hydraulic System of Fuel Oil Supply to the Electronically Controlled Main Engine". Journal of Maritime & Transportation Science 60, nr 1 (lipiec 2021): 9–19. http://dx.doi.org/10.18048/2021.60.01.
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Hydraulic system of the fuel oil supply to the electronically controlled main engine resolve the problem of the optimized control of the engine which act beneficially to the specific fuel oil consumption and a reduction of the NOx emission. The assumed numerical example is giving insight to the power consumption for the hydraulic control of the fuel oil injection and exhaust valve operation for the two stroke marine engine. The calculated power is higher for the fuel oil pressure booster operation compared to the exhaust valve actuator for about 88%, which is resulted due to the higher operating pressure of the fuel injection to the cylinder, versus lower operating pressure required for the opening of the exhaust valve.
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Zhang, Defu, Zhenyu Shen, Nan Xu, Tingting Zhu, Lei Chang i Hui Song. "Development of a Zero-Dimensional Model for a Low-Speed Two-Stroke Marine Diesel Engine with Exhaust Gas Bypass and Performance Evaluation". Processes 11, nr 3 (19.03.2023): 936. http://dx.doi.org/10.3390/pr11030936.
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Most large commercial vessels are propelled by low-speed two-stroke diesel engines due to their fuel economy and reliability. With increasing international concern about emissions and the rise in oil prices, improvements in engine efficiency are urgently needed. In the present work, a zero-dimensional model for a low-speed two-stroke diesel engine is developed that considers the exhaust gas bypass and geometry structures for the gas exchange model. The model was applied to a low-speed two-stroke 7G80 ME-C9 marine diesel engine and validated with engine shop test data, which consisted of the main engine performance parameters and cylinder pressure diagrams at different loads. The simulation results were in good agreement with the experimental data. Thus, the model has the ability to predict engine performance with good accuracy. After model validation, the variations in compression ratio, fuel injection timing, exhaust gas bypass valve opening portion, exhaust valve opening timing, and exhaust valve closing timing effects on engine performance were tested. Finally, the influence level of different parameters on engine performance was summarized, which can be used as a reference to determine the reasons for high fuel consumption in some cases. The developed engine performance model is considerable in digital twins for performance simulation, health management, and optimization.
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Guan, Wei, Vinícius B. Pedrozo, Hua Zhao, Zhibo Ban i Tiejian Lin. "Variable valve actuation–based combustion control strategies for efficiency improvement and emissions control in a heavy-duty diesel engine". International Journal of Engine Research 21, nr 4 (26.04.2019): 578–91. http://dx.doi.org/10.1177/1468087419846031.
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High nitrogen oxide levels of the conventional diesel engine combustion often requires the introduction of exhaust gas recirculation at high engine loads. This can adversely affect the smoke emissions and fuel conversion efficiency associated with a reduction of the in-cylinder air-fuel ratio (lambda). In addition, low exhaust gas temperatures at low engine loads reduce the effectiveness of aftertreatment systems necessary to meet stringent emissions regulations. These are some of the main issues encountered by current heady-duty diesel engines. In this work, variable valve actuation–based advanced combustion control strategies have been researched as means of improving upon the engine exhaust temperature, emissions, and efficiency. Experimental analysis was carried out on a single-cylinder heady-duty diesel engine equipped with a high-pressure common-rail fuel injection system, a high-pressure loop cooled exhaust gas recirculation, and a variable valve actuation system. The variable valve actuation system enables a late intake valve closing and a second intake valve opening during the exhaust stroke. The results showed that Miller cycle was an effective technology for exhaust temperature management of low engine load operations, increasing the exhaust gas temperature by 40 °C and 75 °C when running engine at 2.2 and 6 bar net indicated mean effective pressure, respectively. However, Miller cycle adversely effected carbon monoxide and unburned hydrocarbon emissions at a light load of 2.2 bar indicated mean effective pressure. This could be overcome when combining Miller cycle with a second intake valve opening strategy due to the formation of a relatively hotter in-cylinder charge induced by the presence of internal exhaust gas recirculation. This strategy also led to a significant reduction in soot emissions by 82% when compared with the baseline engine operation. Alternatively, the use of external exhaust gas recirculation and post injection on a Miller cycle operation decreased high nitrogen oxide emissions by 67% at a part load of 6 bar indicated mean effective pressure. This contributed to a reduction of 2.2% in the total fluid consumption, which takes into account the urea consumption in aftertreatment system. At a high engine load of 17 bar indicated mean effective pressure, a highly boosted Miller cycle strategy with exhaust gas recirculation increased the fuel conversion efficiency by 1.5% while reducing the total fluid consumption by 5.4%. The overall results demonstrated that advanced variable valve actuation–based combustion control strategies can control the exhaust gas temperature and engine-out emissions at low engine loads as well as improve upon the fuel conversion efficiency and total fluid consumption at high engine loads, potentially reducing the engine operational costs.
Rozprawy doktorskie na temat "Exhaust valve opening"
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Kumar, Krishna Mohan. "Direct Estimation of Acoustic Source Characteristics of the Internal Combustion Engine Exhaust System and Analysis of Complex Muffler Configurations". Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5080.
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Reduction in noise radiated from the IC engines is needed to meet the ever increasingly stringent noise regulations. The unmuffled exhaust noise of an IC engine is the biggest contributor to the overall engine noise. Prediction of the unmuffled sound pressure level (SPL) spectrum calls for prior estimation of both the source characteristics, namely, source pressure and source impedance, whereas prediction of the insertion loss (IL) spectrum of a muffler needs only source impedance. The present study aims at estimation of both these source characteristics using a novel direct evaluation method.
Computation of source impedance and exhaust gas mass flow rate calls for the aero-thermodynamic computation in the time-domain making use of the values of pressure and temperature of the in-cylinder gas at the exhaust valve opening (EVO) along with the basic geometrical details of the cylinder, intake and exhaust valves or ports. Equivalent source impedance of the time-varying source is estimated as the reciprocal of the crank-angle-area-weighted average of the admittance of the source. A simple, albeit approximate, parametric expression of source impedance is derived in terms of the cylinder capacity for ready reference of the muffler designers.
This novel direct evaluation method is now applied to the naturally aspirated (NA) as well as turbocharged (T/C) multi-cylinder engine exhaust system by estimating the source characteristics of each cylinder assuming that the other cylinders are not exhausting at the same time. The estimated source characteristics for each cylinder at the downstream end of the exhaust valve are then transferred downstream to the end of the runner. These are then combined and transferred across the manifold (runners) and turbine to estimate the source characteristics of the complete engine at any desired source-load junction. For turbocharged engines, transfer matrix of the turbine is derived using the mass continuity upstream and downstream of the turbine along with its static pressure ratio. Finally, the estimated source characteristics of the complete engine are used to predict the unmuffled SPL spectrum which is shown to compare reasonably well with the measured spectrum.
Efficient mufflers are needed to comply with the stringent noise regulations as well as the requirement of low backpressure to ensure low brake specific fuel consumption. Design and analysis of some commercial complex mufflers are therefore studied here. For mufflers used in multi-cylinder engines, it is observed that anechoic source assumption is reasonable, and therefore, the IL spectrum is computed using characteristic impedance of exhaust pipe as source impedance. The mufflers are analysed using the 1-D integrated transfer matrix (ITM) approach and validated against the 3-D finite element analysis. Three different types of mufflers; double flow-reversal muffler with a few holes in baffles, multiply-connected co-axial (MCCA) perforated element muffler, and side-inlet side-outlet (SISO) perforated element muffler are investigated here.
The parametric studies on one of the configurations out of the four different MCCA muffler configurations highlights the crucial role of mean flow on the flow-acoustic performance. Some design guidelines have been developed for the MCCA mufflers with higher specific IL (ratio of overall IL (in dBA) to the muffler-to-engine volume ratio) as well as modest backpressure.
In general, large volume of the muffler for a diesel generator (DG) set engine is not a concern, but logistics of an acoustic enclosure require mounting of the exhaust muffler on the top of the enclosure with side-inlet and side-outlet. Four different, yet somewhat similar, SISO perforated element muffler configurations with approximately same backpressure have been investigated. Finally, some design guidelines have been evolved for the SISO mufflers.
Części książek na temat "Exhaust valve opening"
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Liu, Wenbo, Junmei Li i Yanfeng Li. "Numerical Simulation on Smoke Control for Extra-Long Tunnel Fires". W Lecture Notes in Civil Engineering, 113–22. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2532-2_10.
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AbstractBased on an actual project in Beijing, this article investigates the effect of smoke control strategies on smoke extraction efficiency under different fire source locations of the point smoke extraction system in extra-long tunnels using Airpak software. The results show that when a fire occurs in a tunnel, the smoke extraction efficiency of the tunnel smoke extraction system varies greatly depending on the location of the fire source and the adoption of different smoke extraction strategies. Due to the suction of the smoke exhaust shaft fan, the relative distance between the electric smoke exhaust valve and the entrance of the tunnel is close, which will cause the smoke exhaust valve within a certain range to be plug-holing, seriously affecting the smoke exhaust effect of the smoke exhaust system. Smoke exhaust valve beyond this range, although not occurring plug-holing the smoke exhaust efficiency is also relatively low, by changing the opening strategy of the smoke exhaust valve can effectively improve the smoke exhaust valve plug-holing, so as to improve the smoke exhaust efficiency.
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Brittenham, Claudia. "Introduction". W Vessels. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198832577.003.0006.
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The vessel might seem an unproblematic category. Vessels are, after all, essential to human survival. They are necessary to contain water, to cook, to store food and goods for future use. Nearly all societies have made and used them; indeed, clay vessels, or their fragments, are one of the principal kinds of archaeological data that give us empirical access into distant worlds of the past. A good proportion of ancient art in museum collections around the world consists of things we would categorize as vessels. Such ubiquity makes vessels central to many kinds of historical investigation. Archaeologists rely on quantitative surveys of durable potsherds to answer questions about chronology, population, trade, and the function of particular spaces, while close attention to the iconography on vessels furnishes important documentary evidence about many aspects of ancient society. Yet as the essays in this volume demonstrate, such approaches by no means exhaust the perspectives that vessels may offer on ancient societies. Many vessels—and assemblages of vessels— were in their own time sites of considerable intellectual power, smart and sophisticated commentaries on the very categories that they embody. On closer examination, the category of the vessel is complex. A vessel is defined not only by its shape, but also by its function, by the presumption that it contains something, though that something may be concealed when the vessel is in use and is not always easy to reconstruct from the archaeological record. But what about a Greek rhyton, a drinking horn with an opening at the bottom, so that liquids poured into one end stream out the other? What about an unused vessel that never held its intended contents; a Maya chocolate pot, broken and then repaired in a way that is no longer watertight; or a thin and fragile gu cup from a Chinese tomb, the form so attenuated that it could never be used? “Is it really a vessel?” is perhaps the least interesting question we can ask about these objects. As Richard Neer argues in his essay in this volume, for us as much as for the ancient Greeks, the value of the category “vessel” might lie precisely in its openness.
Streszczenia konferencji na temat "Exhaust valve opening"
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Schernus, C., F. Van Der Staay, H. Janssen, J. Neumeister, B. Vogt, L. Donce, I. Estlimbaum, E. Nicole i C. Maerky. "Modeling of Exhaust Valve Opening in a Camless Engine". W SAE 2002 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2002. http://dx.doi.org/10.4271/2002-01-0376.
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Salehi, Rasoul, i Anna G. Stefanopoulou. "Optimal Exhaust Valve Opening Control for Fast Aftertreatment Warm Up in Diesel Engines". W ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9178.
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This paper proposes to optimally adjust the exhaust valve opening (EVO) timing for faster selective catalytic reduction (SCR) aftertreatment system warm-up during the cold start phase of the federal test procedure (FTP). Early termination of the power stroke by EVO timing advance increases the engine exhaust gas temperature. It, on the other hand, causes exhaust flow rate reduction that decreases the coefficient of the heat transfer from the exhaust gas to the catalyst. The competing effects along with the fuel consumption increase associated with early EVO need careful consideration and the optimal EVO timing is a load-dependent balance of all these effects. This careful balance is achieved in this paper by dynamic programing (DP). Specifically, the minimum time to light-off (TTL) is formulated and applied to the cold phase of the FTP. A high fidelity detailed and verified engine and aftertreatment model is effectively simplified to enable utilizing computationally expensive DP optimization algorithm. Optimization results indicate that advancing the EVO reduces the TTL for the SCR catalyst from 659 s to 500 s, a 24% reduction. This fastest possible increase in the SCR temperature is shown to be with an expense of 4.1% increase in the fuel consumption. The results are dependent to the target light-off temperature and the load profile. Assuming a specific light-off temperature and the FTP, possible rule-based scenarios for online optimization are discussed.
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Sakamoto, Masahiko. "Ship Propulsion Equipment Driven by Air Compressed by Pressure Fluctuation in Blower Piping System". W ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16103.
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The characteristics of thrust for ship propulsion equipment directly driven by air compressed by pressure fluctuation in a blower piping system are investigated. The pressure in the piping system with a discharge opening under the surface of water is measured for the depth and the cross-sectional area of the discharge opening. An exhaust valve is positioned upon the air ejection hole, and the effects of the valve on the pressure in the pipes and the thrust for the propulsive nozzle were examined. The following results were obtained. The pressure fluctuation owing to the columnar resonance or Helmholtz resonance occurs at the certain specific depth or cross sectional area of the discharge opening. The pressure in the pipes decreases immediately after the exhaust valve was opened, and it increases just before the valve is closed. The dominant frequency of the pressure fluctuation in the pipes agrees with that of the opening-closing cycle for the exhaust valve. The thrust for the propulsive nozzle monotonically increases with increasing number of revolutions and depth. The interfacial wave in the nozzle appears in the frequency of approximately 4Hz, and it is important for the increase of the thrust to synchronize the opening-closing cycle for the exhaust valve with the generation frequency of the interfacial wave. The finite difference lattice Boltzmann method is helpful to investigate the characteristics of the flow in the nozzle.
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Lavertu, Thomas M., Roy J. Primus i Omowoleola C. Akinyemi. "An Investigation in Improving the Exhaust Management Process on Miller Cycle and Turbocompounding". W ASME 2012 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ices2012-81159.
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A reduction in diesel engine fuel consumption at a constant emissions level can be achieved by various means. A power turbine as a means of waste heat recovery (i.e., turbocompounding) and altered intake valve closure timing (Miller cycle) are two such mechanisms. Each of these technologies act as a means of improving the expansion process of the combustion gases, requiring reduced fueling for the same work extraction. When these embodiments are typically implemented, the timing of the exhaust valve opening is maintained. However, optimization of the timing of the exhaust valve opening presents the potential for further improvement in the expansion process. Variations in the exhaust valve opening timing will be investigated for Miller and turbocompounding cycles as well as the combination of the two features. Results will be shown to quantify the impact these variations have in system efficiency. Second law analysis will be used to show how these variations in engine configurations impact individual loss mechanisms. Finally, comparisons will be made to show the relative differences between Miller cycle and turbocompounding with and without optimization of the exhaust valve timing.
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Hu, Bo, Sam Akehurst, Chris Brace, Pengfei Lu, Colin D. Copeland i J. W. G. Turner. "Fuel Efficiency Optimization for a Divided Exhaust Period Regulated Two-Stage Downsized SI Engine". W ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43023.
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In our previous paper, a new gas exchange concept termed Divided Exhaust Period Regulated 2-stage (DEP R2S) system has been proposed. In this system, two exhaust valves in each cylinder are separately functioned with one valve feeding the exhaust mass flow into the high pressure (HP) manifold whilst the other valve evacuating the remaining mass flow directly into the low pressure (LP) manifold. By adjusting the timing of the exhaust valves, the target boost can be controllable whilst improving the engine’s pumping work and scavenging is attainable which results in better fuel efficiency from the gas exchange perspective. This paper will continue this study by adding an appropriate knock model to examine the benefits this concept could bring to the combustion phasing. The results at full load showed that under knock limited spark advance (KLSA) and fully optimized exhaust valve timing condition, the DEP R2S system benefited from lower pumping loss and better scavenging due to the reduced backpressure and improved pulsation interference despite suffering from reduced expansion ratio and expansion work. The combustion phasing was advanced across the engine speed which is mainly attributed to the reduced residual and the reduced requirement of gross IMEP. The net BSFC was observed to improve by up to 3% depending on the engine operating points. At part load, the DEP R2S system could be used as a mechanism to extend the ‘duration’ of the exhaust valve. This will reduce the recompression effect of the exhaust residuals during the beginning and the end of the exhaust stroke compared to the original R2S model with late exhaust valve opening and early exhaust valve opening. In addition, increased internal EGR due to the increased overlap between the LP and the intake valve is also beneficial for the improved PMEP as the throttle can be further opened to reduce the corresponding throttling loss. The average net BSFC improvement is expected to be approximately 6–7%.
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Jiang, Lei-Yong, Keith Depooter i William Carscallen. "Flow Field in the Vicinity of a High-Pressure-Drop Ball Valve". W ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15711.
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The testing of gas turbine combustors requires large flow rates at high pressures and elevated temperatures. In order to control the flow and pressure inside the combustor, some type of control valve is required in the exhaust section of the testing system. This backpressure valve is exposed to severe operating conditions. To understand the complex flow features in the exhaust section and provide relevant information for selecting suitable low-cost valves for new large test cells, a numerical study was carried out on a backpressure valve that has been used in a number of testing programs. The flow fields in the vicinity of the valve and the piping sections ending at the exhaust stack were resolved for three practical operating conditions. The results indicate that because of the presence of the valve with a V-shape opening, the flow field behind experiences a series of three-dimensional expansion and shock waves. The strong interactions exist between the flow behind the blockage and the flow passing through the opening area. More importantly, it is found that most of the pressure drop occurs immediately downstream of the valve, and its values are much larger than those provided by suppliers based on shock-free flow calculation. This may explain why the valve lost its function during testing and its stainless-steel seat had to be removed in order to maintain its rotational function. Based on this study, it is recommended that a second pressure-drop element be installed in the exhaust section in order to keep the expected lifetime of valves and reduce noise level. This suggestion has been implemented in the new large test cell at the Gas Turbine Laboratory.
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Gajula, V., i S. Bari. "Performance Tuning of an IC Engine Based on Pressure Wave Propagation With a Continuously Variable Exhaust Runner Length and Exhaust Valve Timing System". W ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70362.
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The momentum of exhaust gas flowing out of the valve creates a pressure wave which can have a positive effect on the evacuation of gases. This concept is known as wave tuning, utilizes the sub-atmospheric pressure waves in the runner to evacuate more exhaust gases. When tuned precisely by varying length and/or exhaust valve timing in such a way that the wave returns in accordance to the exhaust valve opening, it creates a scavenging effect and this improves the engine performance. In this research both exhaust runner length and valve duration have been changed to arrive the sub-atmospheric wave at exhaust valve to improve the performance of the engine using Ricardo WAVE software. It was found that varying the exhaust valve timing managed to improve the torque by 1–3% at different rpm. However, varying both length and timing improved the toque 7–10% at lower speed and 3–6% at higher rpm.
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Koeberlein, Ed, Lyle Kocher, Dan Van Alstine, Karla Stricker i Greg Shaver. "Physics Based Control Oriented Modeling of Exhaust Gas Enthalpy for Engines Utilizing Variable Valve Actuation". W ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-6001.
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Accurate calculation of the conditions (i.e., temperature, pressure, and enthalpy) of internal combustion engine cylinder exhaust is critical to the modeling of, and control design development for, gas exchange in modern and future diesel engine systems. In this paper, a physically-based model for cylinder exhaust temperature, pressure, and enthalpy for engines equipped with variable valve actuation is outlined and extensively validated against experimental data from 193 operating points. The model takes the known conditions when the intake valves close and steps through a polytropic compression process, constant pressure combustion process beginning at top-dead center, and a polytropic expansion process to achieve the desired results when the exhaust valves open. To incorporate the flexibility of modulating the intake valve opening and closing, the effective compression ratio is used to establish the conditions when the intake valves close. Experimental model validation, via a unique multi-cylinder diesel engine utilizing fully flexible intake valve actuation, shows that the model captures the influences of all of the model inputs: engine speed, charge flow, total fueling quantity, intake manifold pressure, and effective compression ratio.
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Bharath, Anand Nageswaran, Nitya Kalva, Rolf D. Reitz i Christopher J. Rutland. "Use of Early Exhaust Valve Opening to Improve Combustion Efficiency and Catalyst Effectiveness in a Multi-Cylinder RCCI Engine System: A Simulation Study". W ASME 2014 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icef2014-5534.
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Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) can result in significant improvements of fuel economy and emissions reduction. However, they can produce significant carbon monoxide and unburnt hydrocarbon emissions at low load operating conditions due to poor combustion efficiencies at these operating points, which is a consequence of the low combustion temperatures that cause the oxidation rates of these species to slow down. The exhaust gas temperature is also not high enough at low loads for effective performance of turbocharger systems and diesel oxidation catalysts (DOC). The DOC is extremely sensitive to exhaust gas temperature changes and lights off only when a certain temperature is reached, depending on the catalyst specifications. Uncooled EGR can increase combustion temperatures, thereby improving combustion efficiency, but high EGR concentrations of 50% or more are required, thereby increasing pumping work and reducing volumetric efficiency. However, with early exhaust valve opening, the exhaust gas temperature can be much higher, allowing lower EGR flow rates, and enabling activation of the DOC for more effective oxidization of unburnt hydrocarbons and CO in the exhaust. In this paper, a multi-cylinder engine system simulation of RCCI at low load operation with early exhaust valve opening is presented, along with consideration of the exhaust aftertreatment system. The combustion process is modeled using the 3D CFD code, KIVA, and the heat release rates obtained from this combustion are used in a GT-Power model of a turbocharged, multi-cylinder light-duty RCCI engine for a full system simulation. The post-turbine exhaust gas is fed into GT-Power’s aftertreatment model of the engine’s DOC to determine the catalyst response. It is confirmed that opening the exhaust valve earlier increases the exhaust gas temperature, and hence lower EGR flow rates are needed to improve combustion efficiency. It was also found that exhaust temperatures of around 457 K are required to light off the catalyst and oxidize the unburnt hydrocarbons and CO effectively. Performance of the DOC was drastically improved and higher amounts of unburnt hydrocarbons were oxidized by increasing the exhaust gas temperature.
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Kim, Dong-Hun, Tae-Hyung Park, Hoon-Suk Kim, Sang-Lip Kang i Ju-Tae Kim. "Improvement of the Exhaust Valve Damping Unit for a 2-Stroke Large Diesel Engine". W ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37619.
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Hydraulic exhaust valve actuating system is generally applied on a 2-stroke large diesel engine for the purpose of structural stability and simplification. In this type of system, damping unit has the function of decreasing impact at the moment of valve closing and preventing damage of exhaust valve and valve seat. However, in the opening stage of exhaust valve, existing damping unit substantially increases maximum hydraulic pressure and causes the cavitation inside which lead to vibration, noise, and higher pressure fluctuation and cavitation damage. Design modification of damping unit was performed to solve existing problems. Hydraulic simulation of exhaust valve actuating system was carried out to verify the application possibility of design modification. Also the effect of design modification could be verified by the rig test of prototype. Finally, it was applied on actual engines and proved to give satisfactory results in solving the substantial problems of the existing damping unit.
Raporty organizacyjne na temat "Exhaust valve opening"
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Kawasaki, Kiyoshi, Akihiro Takegoshi, Koji Yamane, Hiroyuki Ohtsubo, Tohru Nakazono i Kazuyuki Yamauchi. Improvement of the Performance on the Small-Scale PCCI Engine Fueled by Natural Gas (2nd Report)~Effects of the Internal EGR by Pilot-Opening of an Intake Valve in an Exhaust Stroke. Warrendale, PA: SAE International, maj 2005. http://dx.doi.org/10.4271/2005-08-0272.
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