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配制辛烷值相同而敏感性不同的高辛烷值燃料,在一台改造的单缸试验发动机上进行了燃料敏感性对部分预混燃烧的燃烧和排放特性影响的研究。采用的不同敏感性的燃料为配制的甲苯参比燃料和市售92#汽油。研究结果表明:燃料敏感性越高,滞燃期越长,油气混合越充分,预混燃烧比例越大,NOx排放越高。燃烧重心(CA50)随着敏感性的增高先推迟后提前,敏感性为2的燃料CA50最迟。燃料敏感性越低,压升率越低,而市售92#汽油挥发性较强,预混比例较大,最大压升率最高;敏感性为2的燃料在上止点附近放热较多,指示热效率较高;汽油及敏感性为5和8的燃料的碳烟排放比其他燃料低。 相似文献
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Although dual‐fuel (DF) engines using a low cetane number primary fuel such as natural gas (NG) ignited by a pilot diesel spray have been the subject of much investigation over years, there are still many unknown problems related to the fundamental combustion process of two fuels. In this work, a quiescent constant volume combustion bomb and a 3‐D numerical model have been used to study the effects of injection nozzle characteristics on the combustion of pre‐mixed NG/air with pilot distillate spray. Experimental tests were conducted on combustion process of pre‐mixed natural gas/air with pilot injection pressure of 30 and 20 MPa with a 4 hole injector, and also with injector nozzle of 8 and 4 holes. The global results obtained from computations compared well with the experimental results. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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介绍了长城汽车研发的一款高性能"2.0VGT"柴油发动机燃烧系统的设计优化过程,通过模拟计算发动机整个工作过程,对进排气系统和进气道形状、气流运动形式、喷油器喷雾特性、燃烧室形状进行多方案优化选型。研究不同工况下,喷油规律(次数、喷油间隔、每次喷油量、喷油时刻)、喷油器特性(喷孔数量、喷孔直径、喷油压力、喷油锥角)的喷雾特性(油滴细化程度、贯穿度)对发动机性能、排放和油耗的影响规律。并对发动机实现国Ⅴ排放要求,对所需要的喷油系统特性及燃烧室形状进行研究。 相似文献
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An experimental study is conducted to investigate the fuel-injection-pressure and engine-speed effects on the performance and exhaust emissions of a naturally aspirated four-stroke indirect-injection (IDI) diesel engine with a swirl combustion chamber. The influence of the injection pressure and the engine rotational speed on fuel consumption, exhaust-gas temperature, exhaust smokiness and exhaust-gas emissions (nitrogen oxides and unburned hydrocarbons) is examined, following a detailed experimental investigation. Empirical easy-to-use correlations are produced, expressing the variation of the various parameters with injection pressure, by applying a regression analysis on the curves fitting the relevant experimental data. Theoretical aspects of diesel fuel spray progress (atomization, evaporation and mixing), combustion and emissions formation are used for the interpretation of the observed engine behaviour. 相似文献
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Due to the scarcity of fossil fuels and the future stringent emission limits, there is an increasing interest for the use of renewable biofuels in compression ignition engines. However, these fuels have different physical, chemical and thermodynamic properties affecting atomization, spray development and combustion processes. The results reported in this paper have been obtained by experimentation with a constant volume combustion chamber. The influences of physical fuel properties on injections under non-evaporating conditions are studied, using a pump-line-nozzle system from a medium speed diesel engine with injection pressures up to 1200 bar, by changing the fuel type and temperature. Experiments were conducted for diesel, biodiesel, straight vegetable oils and animal fats. Injection pressure and needle lift measurements were analyzed. A high speed camera was used to visualize the spray, which enabled us to study the spray penetration and spray angle. Our results show that the fuel temperature is an important parameter to control because it significantly affects the fuel properties. Both the injection timing and injection duration are affected by the fuel properties. The influences of these properties on the spray development were less pronounced. At low temperatures, a strongly deteriorated atomization of oils and fats was observed. 相似文献
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为研究乙醇汽油在缸内直喷汽油机中的积碳生成问题及喷雾特性,选取5孔直喷喷嘴为研究对象,通过试验模拟缸内积碳生成环境,制备得到积碳喷油器。基于高速摄像技术和定容弹,对未积碳喷油器和积碳喷油器进行喷雾试验,得到5孔直喷喷嘴的喷雾图像,利用MATLAB程序对喷雾图像进行可视化处理。针对喷雾中可能出现的闪急沸腾现象,研究燃料温度与背景压力对乙醇汽油喷雾闪沸的影响,结果表明:乙醇汽油的使用会加重直喷喷嘴的积碳问题,导致喷嘴的喷油量减小,雾化质量恶化。 相似文献
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An experimental study is conducted to evaluate the use of JP-8 aviation fuel as a full substitute for diesel fuel in a Ricardo E-6 high-speed naturally-aspirated four-stroke experimental engine having a swirl combustion chamber. The study covers a wide range of engine load and speed operating conditions, comprising measurements of cylinder pressure diagrams, high-pressure fuel pipe pressures, exhaust gas temperatures, fuel consumptions, exhaust smokiness and exhaust gas emissions (nitrogen oxides, unburned hydrocarbons and carbon monoxide). Processing of the measurements provides important performance parameters such as maximum combustion pressure, dynamic injection timing, ignition delay, combustion irregularity and knocking tendency. The differences in the measured performance and exhaust emission parameters are determined for engine operation with JP-8 fuel, against baseline engine operation using diesel fuel. The study shows that the exhaust emission levels are not much different for operation with the two fuels. On the contrary, operation with JP-8 fuel increases combustion pressures, combustion intensity and irregularity. This is caused mainly by high pressure fluctuations present in the fuel injection system due to the different physical properties of JP-8 fuel (compared to diesel fuel), which totally change the injection characteristics. Retardation of the static injection timing is one means of improving this situation, while using the same fuel injection equipment. © 1997 John Wiley & Sons, Ltd. 相似文献
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This article is a condensed overview of a dimethyl ether (DME) fuel application for a compression ignition diesel engine. In this review article, the spray, atomization, combustion and exhaust emissions characteristics from a DME-fueled engine are described, as well as the fundamental fuel properties including the vapor pressure, kinematic viscosity, cetane number, and the bulk modulus. DME fuel exists as gas phase at atmospheric state and it must be pressurized to supply the liquid DME to fuel injection system. In addition, DME-fueled engine needs the modification of fuel supply and injection system because the low viscosity of DME caused the leakage. Different fuel properties such as low density, viscosity and higher vapor pressure compared to diesel fuel induced the shorter spray tip penetration, wider cone angle, and smaller droplet size than diesel fuel. The ignition of DME fuel in combustion chamber starts in advance compared to diesel or biodiesel fueled compression ignition engine due to higher cetane number than diesel and biodiesel fuels. In addition, DME combustion is soot-free since it has no carbon–carbon bonds, and has lower HC and CO emissions than that of diesel combustion. The NOx emission from DME-fueled combustion can be reduced by the application of EGR (exhaust gas recirculation). This article also describes various technologies to reduce NOx emission from DME-fueled engines, such as the multiple injection strategy and premixed combustion. Finally, the development trends of DME-fueled vehicle are described with various experimental results and discussion for fuel properties, spray atomization characteristics, combustion performance, and exhaust emissions characteristics of DME fuel. 相似文献
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The purpose of this study was to develop numerical simulation of spray combustion of emulsified fuel with considering puffing and micro-explosion. First, a mathematical model for puffing was proposed. In the proposed puffing model, the rate of mass change of a droplet during puffing was expressed by the evaporation rate of dispersed water and the mass change rate due to fine droplets spouted from the droplet surface. The mass change rate due to fine droplets was related to the evaporation rate of the dispersed water and each liquid content. This model had only one experimental parameter. The essential feature of this model was that it was simple to apply to numerical simulation of spray combustion. First, the validity of the proposed puffing model was investigated with the experimental results for a single droplet. The calculated results for a single droplet with the experimental parameter varying from 5.0 to 10 were in good agreement with the experimental results. Moreover, numerical simulation of spray combustion of emulsified fuel was carried out. The occurrence of puffing and micro-explosion was determined by the inner droplet temperature. When micro-explosion occurred, a droplet changed to vapor rapidly. When the proposed puffing model was used in numerical simulation of spray combustion, the experimental parameter in the puffing model was determined for each droplet by random numbers within the range 5.0-10. The calculated results of spray combustion of emulsified fuel without considering puffing or micro-explosions were different from the experimental results even where combustion reactions were almost terminated. Meanwhile, the calculated results when considering puffing and micro-explosions were in good agreement with experimental results at the same location. 相似文献
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为提升燃油系统电控化改造后4190ZLC-2船用中速柴油机的经济性能和排放性能,开展了燃油系统多参数优化试验;利用AVL FIRE软件对试验得到的经济性最优匹配参数下的柴油机高压工作过程进行了仿真计算;通过对燃烧室内三位流场的分析,提供进一步提高喷油压力和修改燃烧室形状的方案;再利用仿真计算得到喷油压力进一步提高后较优的燃烧室匹配方案。研究结果表明:喷油压力提高后,柴油机总体性能提高;为适应喷油压力的提高,燃烧室的深度和开口直径分别应该减小和增加,但燃烧室的深度太浅会造成燃烧不完全,导致油耗率上升。研究结果为该柴油机的燃烧系统改进提供了理论依据。 相似文献
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In a previous study on the stability of spray combustion for mixtures of alcohols (ethanol or 1-propanol) and water, the feasibility of burning fuels heavily diluted with water was demonstrated. In that study it was found that the preferential vaporization of alcohols in water can significantly enhance flame stability. Due to their high volatility and high activity coefficient in aqueous solution, the alcohols quickly evaporate from the droplets and generate a concentrated fuel vapor at the base of the jet. Therefore, a flame can be ignited and stabilize even though the water content of the fuel is quite high (up to 90 wt%) (Yi and Axelbaum, 2013). In this study, we develop a procedure for selecting chemical fuels showing strong preferential vaporization in water. t-Butanol was identified as an excellent candidate based on its physical and chemical properties, including activity coefficient, vapor pressure, heat of vaporization and heat of combustion. Flame stability was evaluated for aqueous solutions of both ethanol and t-butanol using a spray burner where the extent of swirl was adjustable. Under both high and low swirl intensity, the flame stability of t-butanol aqueous solutions was better than that of ethanol. The characteristic time for fuel release from a droplet was modeled for both ethanol and t-butanol. The time to release 99% of the fuel from the droplet for t-butanol is over 70% shorter compared to that for ethanol, which supports the improved flame stability observed for t-butanol in the experiments. 相似文献
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Ahmed M.R.N. Alrashidi Nor Mariah Adam Abdul Aziz Hairuddin Luqman Chuah Abdullah 《国际能源研究杂志》2018,42(5):1813-1833
In recent years, new ways of improving the combustion efficiency of fuel during gas turbine operations have been developed. The most significant has been the application of plasma technology for the combustion of fuel in gas turbine operations. Plasma is formed when gas is exposed to either high temperature or high‐voltage electricity. This technology is very promising and has proven to enhance the performance of gas turbines and reduce toxic emissions. Recent studies have shown the use of different types of plasma applications in gas turbine operations such as plasma torch, filamentary discharge, and nanosecond pulse discharge, whose results show that plasma technology has great potential in improving flame stabilization, the fuel/air mixing ratio, and flash point values of these fuels. These findings and advances have further provided new opportunities in the development of efficient plasma discharges for practical uses in plasma combustion of fuel for gas turbine operations. This article is a comprehensive overview of the advances and blind spots in the knowledge of plasma combustion of fuel during internal combustion engine operations. This review also focuses on applications, methods, and experimental results in plasma combustion of fuel in gas turbines. 相似文献
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The mathematical models to predict pressure, net heat release rate, mean gas temperature, and brake thermal efficiency for dual fuel diesel engine operated on hydrogen, LPG and mixture of LPG and hydrogen as secondary fuels are developed. In these models emphasis have been given on spray mixing characteristics, flame propagation, equilibrium combustion products and in-cylinder processes, which were computed using empirical equations and compared with experimental results. This combustion model predicts results which are in close agreement with the results of experiments conducted on a multi cylinder turbocharged, intercooled gen-set diesel engine. The predictions are also in close agreement with the results on single cylinder diesel engine obtained by other researchers. A reasonable agreement between the predicted and experimental results reveals that the presented model gives quantitatively and qualitatively realistic prediction of in-cylinder processes and engine performances during combustion. 相似文献
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İlker Temizer 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2021,43(1):17-34
ABSTRACT In this study, the effects on combustion characteristics and emission were investigated in a direct injection diesel engine. In experimental and numerical studies, the engine was operated at 2000 rpm. The analyzes were made in the AVL-FIRE ESE Diesel part with Computational Fluid Dynamics (CFD) software. Standard combustion chamber (SCC) and Modified combustion chamber (MCC) geometry were compared in the modeling. By means of the designed MCC combustion chamber geometry, the fuel released from the injector was directed to the piston bowl area. Therefore, the mixture was homogenized and the combustion had been improved. In addition, the evaporation rate of the mixture increased with the MCC geometry. Also, lower NO and CO emissions were obtained with the MCC model compared to the SCC model. On the other hand, diesel fuel and mass 5% hydrogen fuel was used into diesel fuel as fuel in the study. The combustion process was investigated using hydrogen in different combustion chambers. The use of hydrogen as additional fuel resulted in higher combustion pressure, temperature and NO emissions. Compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, CO emission decreased of 6% and 3% for hydrogen-added mixture fuel. Also, compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, NO emission decreased of 11% and 32% for hydrogen-added mixture fuel. Moreover, flame velocity, heat release rate and flame propagation increased with the addition of hydrogen fuel. 相似文献
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采用高速摄影技术研究了缸内直喷周向分层(简称DICSC)燃烧系统火花塞附近两根油历史潮流的发展历程。研究结果表明,喷雾混合过程中燃油碰壁、反弹现象非常明显,大多数燃油的雾化与蒸发产生于油束碰壁以后。靠近壁面处燃油浓度最大,向燃烧室中心方向浓度逐渐降低,沿周向、顺涡流方向形成了明显的由浓到稀的分层。因而,为了保证较好的着火稳定性,在DICSC燃烧系统中火花塞靠近壁面布置并处于油束下游一定角度比较合适,此外有浓度合适、易于点燃的混合气以便火焰能够顺利扩展。另外,还研究了不同涡流比和油束夹角下的油束发展历程。 相似文献
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Motohiro Oshima Akiko Komeda Koji Tominaga Motoi Nakao Tetsuo Shimizu Jiro Senda Kozo Ishida 《亚洲传热研究》2009,38(5):284-296
We propose a novel system of chemical vapor deposition (CVD), i.e., flash boiling spray CVD (SF‐CVD) to eliminate several kinds of problems, such as the decomposition of precursors in the supply line and evaporator. In this method, liquid precursors are supplied directly to the vacuum chamber through an injector, just like fuel for an automobile engine, without any vaporizers, so as to induce an unsteady and intermittent flash boiling spray in the chamber. However, it is necessary to keep the lowest ambient pressure possible because the saturated vapor pressure of the precursors is very low. Thus, this is very useful for modifying the saturated vapor pressure of the precursors. A technique of lowering the vaporization pressure is proposed by mixing a more saturated vapor‐pressure organic solvent with a precursor. To determine the principles underlying FS‐CVD, we first formed SiO2 film on the Si substrate. A mixed solution of tetraethylorthosilicate (TEOS) and n‐pentane was used as the mixing solution. The film thickness distribution of SiO2 film on a 100‐mm‐diameter Si wafer was ±4% using this method. Furthermore, this method enabled us to control film with various thicknesses by optimizing the injection duration, cycle, and injection cycle per second. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20235 相似文献