采用文曲利管降低柴油机NOx排放

废气再循环(EGR,Exhaust Gas Recirculation)是大幅降低整机排放污染物的有效办法,也是目前较为常用和有效的措施.废气再循环(EGR)就是通过将柴油机排出的废气重新引回到气缸内参与燃烧的装置,可更好地控制和减少其尾气中NOx的排放量.文中介绍了柴油机工作时产生NOx的机理和文曲利管降低柴油机NOx排放的原理,通过对安装有文曲利管的柴油机进行试验,分析废气再循环率对柴油机动力性能和NOx排放的影响.     

柴油机EGR系统及其PID控制过程浅析

废气再循环技术是降低柴油机NO_x排放的一种有效措施,通过将一部分废气导入燃烧室,增加燃烧室内气体的热容量,降低燃烧最高温度,从而抑制NO_x生成。柴油机不同工况下对再循环废气需求量不同,因而需要对EGR率进行实时控制,利用PID控制可实现对EGR系统的即时精确控制,以保证兼顾柴油机排放和燃烧性能。     

柴油机EGR系统电控单元的设计与应用

针对增压直喷柴油机开展废气再循环(EGR)技术的研究与应用,以降低氮氧化物(NOx)排放.依据柴油机EGR控制系统的工作特点和功能要求,进行了控制系统的硬件电路设计和控制软件编写,实际控制效果良好.     

柴油机EGR系统电控单元的设计与应用

针对增压直喷柴油机开展废气再循环(EGR)技术的研究与应用,以降低氮氧化物(NOx)排放.依据柴油机EGR控制系统的工作特点和功能要求,进行了控制系统的硬件电路设计和控制软件编写,实际控制效果良好.     

博格华纳EGR冷却器用于雷诺柴油发动机

雷诺1．6L柴油机将采用博格华纳出品的最新废气再循环（EGR）冷却器。博格华纳先进的EGR技术使用混合管总成模块,燃油效率提高3％,并使发动机废气排放量符合欧Ⅵ排放标准。博格华纳将涡轮增压技术和最新的紧凑型EGR技术结合起来,延长发动机寿命,以适应未来市场对发动机技术的要求。     

柴油机废气再循环系统冷却器的数值模拟

柴油机废气再循环(EGR)技术能有效降低NOx有害排放,而EGR冷却器的结构优化是提高冷却器效率,减少NOx排放的有效手段.应用FLUENT软件对柴油机废气再循环系统冷却器的数值模拟,为柴油机废气再循环系统冷却器的设计和优化提供理论依据.     

文丘里管废气再循环系统对涡轮增压柴油机性能影响的研究

加装文丘里管的高压废气再循环(Exhaust gas re-circulation,EGR)进气系统,在兼顾柴油机经济性、动力性的前提下,研究该进气系统对NO_x排放的影响。根据一款柴油机的基本结构建立柴油机一维仿真计算模型和燃烧室的三维仿真计算模型。在对模型进行标定和对柴油机原机性能仿真计算的基础上,为进气系统引入文丘里管装置并对其结构参数进行优化设计。应用所建立的一维和三维柴油机模型,对文丘里管EGR系统柴油机的经济性、NO_x和Soot排放特性进行仿真计算研究,并对计算结果进行试验验证。研究结果表明,优化设计的文丘里管EGR系统可使柴油机在欧洲稳态循环(European steady state cycle,ESC)各工况下实现较为理想的EGR率,并在不明显影响柴油机燃油经济性的前提下,使NO_x排放量下降了约28.4%。文丘里管进气系统可以实现较为理想的高压EGR循环,在柴油机ESC工况下(怠速除外)能够达到较为理想的EGR率。     

基于柴油机各缸EGR率差异的分缸仿真分析

利用发动机仿真模拟软件,对电控单体泵柴油机的燃烧过程进行数值模拟分析。通过研究电控单体泵柴油机各缸实际EGR(Exhaust Gas Recycling,废气循环)率不均匀的成因以及对柴油机燃烧排放的影响,提出柴油机各缸喷油参数分缸标定的优化方案。经过对喷油量和喷油提前角同时进行分缸标定仿真模拟研究,结果表明,分缸标定能有效地解决因柴油机各缸实际EGR率差异导致的柴油机各缸燃烧不均衡的问题,并能有效降低柴油机尾气中SOOT(碳烟)和NOx(氮氧化物)的排放。     

柴油机冷EGR温度控制器的研究

为了降低柴油机NOx的排放量,设计了一种冷EGR温度控制器。该控制器可通过控制直流电动水泵的转速来调节冷却水的循环量,确保不同工况下的最佳EGR冷却温度。通过传感器信号获得EGR的冷却温度,如果EGR的冷却温度不在最佳冷却温度范围内,控制器通过PID控制改变脉宽调制信号PWM的占空比来调整水泵电机的平均电压以改变水泵的转速进而调节冷却水的循环量,从而实现冷EGR温度的自动控制。在CA498型柴油机上对该温度控制器进行了试验,结果表明,与未冷却的EGR系统相比,该冷EGR温度控制器可以有效地降低NOx的排放量。     

渔船用柴油机废气再循环系统的数值模拟

为了降低渔船用柴油机的NOx排放量,达到符合国际海事组织对船舶防止空气污染的规定中的NOx章程的规范。利用废气再循环原理设计了一套柴油机废气减排系统,以降低渔船用柴油机的NOx排放量。通过CFD数值模拟的方法对某柴油机的废气再循环系统进行了二维流场的数值模拟,以确定合理的废气回流比例。模拟过程使用不同的EGR阀门开度进行分析,得到了EGR阀门开度与EGR率之间的比例关系,为柴油机废气再循环系统的设计提供了理论依据。     

EFFECTS OF COOLED EXTERNAL EXHAUST GAS RECIRCULATION ON DIESEL HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE

The effects of cooled external exhaust gas recirculation (EGR) on the combustion and emission performance of diesel fuel homogeneous charge compression ignition (HCCI) are studied. Homogeneous mixture is formed by injecting fuel in-cylinder in the negative valve overlap (NVO) period. So, the HCCI combustion which has low NOx and smoke emission is achieved. Cooled external EGR can delay the start of combustion effectively, which is very useful for high cetane fuel (diesel) HCCI, because these fuels can easily self-ignition, which makes the start of combustion more early. External EGR can avoid the knock combustion of HCCI at high load which means that the EGR can expand the high load limit. HCCI maintains low smoke emission at various EGR rate and various load compared with conventional diesel engine because there is no fuel-rich area in cylinder..     

Precise instrumentation of a diesel single-cylinder research engine

The accuracy of any empirical result is a direct consequence of the quality of experimental setup and the strict control over testing conditions. For internal combustion engines, a large number of parameters that also exhibit complex interdependence may significantly affect the engine performance. Therefore, this work describes the essentials required to establish a high-quality diesel engine research laboratory. A single-cylinder diesel engine is taken as the fundamental building block and the requirements for all essential sub-systems including fuel, intake, exhaust, coolant and exhaust gas recirculation (EGR) are laid out. The measurement and analysis of cylinder pressure, and exhaust gas sampling/conditioning requirements for emission measurement are discussed in detail. The independent control of EGR and intake boost is also highlighted. The measurement and analysis techniques are supported with empirical data from a single-cylinder diesel engine setup. The emphasis is on providing the necessary guidelines for setting up a fully-instrumented diesel engine test laboratory.     

柴油机尾气排放净化臭氧量的优化研究

臭氧具有强氧化性,对内燃机燃烧过程具有催化和强化作用,能提高内燃机的燃烧性能,并降低有害成分的排放。本文在采用臭氧技术的基础上,研究了臭氧浓度变化对柴油机污染物排放的影响,并对其进行优化,以获得最佳的排放降低效果。     

The experimental investigations of recirculated exhaust gas on exhaust emissions in a diesel engine

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads were experimentally investigated by using a four-cycle, four-cylinder, swirl chamber type, water-cooled diesel engine operating at three engine speeds. The purpose of this study was to develop the EGR-control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions, and a novel diesel soot removal device with a cylinder-type scrubber for the experiment system was specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. The experiments were performed at the fixed fuel injection timing of 4° ATDC regardless of experimental conditions. It was found that soot emissions in exhaust gases were reduced by 20 to 70% when the scrubber was applied in the range of the experimental conditions, and that NOx emissions decreased markedly, especially at higher loads, while soot emissions increased owing to the decrease in intake and exhaust oxygen concentrations, and the increase in equivalence ratio as the EGR rate is elevated.     

The effect of exhaust gas recirculation (EGR) on combustion stability, engine performance and exhaust emissions in a gasoline engine

The EGR system has been widely used to reduce nitrogen oxides (NOx) emission, to improve fuel economy and suppress knock by using the characteristics of charge dilution. However, as the EGR rate at a given engine operating condition increases, the combustion instability increases. The combustion instability increases cyclic variations resulting in the deterioration of engine performance and emissions. Therefore, the optimum EGR rate should be carefully determined in order to obtain the better engine performance and emissions. An experimental study has been performed to investigate the effects of EGR on combustion stability, engine performance, NOx and the other exhaust emissions from 1. 5 liter gasoline engine. Operating conditions are selected from the test result of the high speed and high acceleration region of SFTP mode which generates more NOx and needs higher engine speed compared to FTP-75 (Federal Test Procedure) mode. Engine power, fuel consumption and exhaust emissions are measured with various EGR rate. Combustion stability is analyzed by examining the variation of indicated mean effective pressure (COV_imep) and the timings of maximum pressure (P_max) location using pressure sensor. Engine performance is analyzed by investigating engine power and maximum cylinder pressure and brake specific fuel consumption (BSFC).     

The effect of combustion parameters on the nitric oxide emission in direct injection type diesel engine

This paper presents the investigation of influence factors on the output performance and the reduction of exhaust emission in the direct injection type diesel engine. In this work, the analysis of combustion products and combustion characteristics are investigated by numerical method and experiment under the various engine operating conditions. The combusion performance and exhaust emissions are analyzed in terms of the heat release, cylinder pressure and major exhaust emissions of engine. The accuracy of the prediction versus experimental data and the capability of the heat release, cylinder pressure and all the major exhaust emissions are demonstrated. The results of this study show that the combustion parameters have influence on the combustion processes and the nitric oxide emission in the direct injection type diesel engine. The nitric oxide concentration decreases with the increase of engine speed and the advance of injection timing.     

A study of the fouling characteristics of EGR coolers in diesel engines

Diesel emission regulations have recently become more severe. An important goal in diesel engine research is the development of methods to reduce the emissions of NOx and PM (particulate matter). Cooled EGR (exhaust gas recirculation) system has been widely used to reduce the NOx and PM emissions of light-duty diesel engines. In this study, numerical analyses, rig tests and engine tests were performed to assess how changes in internal shape characteristics can improve the heat exchange efficiencies of EGR coolers. The heat exchange efficiencies of EGR coolers have been numerically and experimentally measured during a fouling process. The results show that the second type of oval EGR cooler tested (oval #2) exhibited better heat exchange efficiency than either the first type of oval EGR cooler was tested (oval #1) or the shell and tube cooler examined. The turbulence generated in exhaust gas flows by the wavy-finned design of the oval EGR coolers facilitated PM desorption that allows these coolers to self-purify. With respect to the two similar oval EGR coolers, the cooler with fin pitch 4 mm has better efficiency than the cooler with fin pitch 6 mm due to differences in the heat transfer areas of these coolers. Both CFD analyses involving extreme conditions of engine operation and engine fouling tests involving conditions experienced during vehicular operation indicate that the two oval coolers differed by less than 4% with respect to both initial heat transfer efficiency and heat transfer efficiency after a 78-hour fouling test.     

Emission characteristics of exhaust gases and nanoparticles from a diesel engine with biodiesel-diesel blended fuel (BD20)

This experimental study sought to investigate the characteristics of the exhaust emissions, and nanoparticle size distribution of particulate matter (PM) emitted from diesel engines fueled with 20% biodiesel-diesel blended fuel (BD20). The study also investigated the conversion efficiency of the warm-up catalytic converter (WCC). The emission characteristics of HC, CO, NOx and nano-sized PM were also observed according to engine operating conditions with and without exhaust gas recirculation (EGR). The study revealed that the maximum torque achievable with the biodieseldiesel blended fuel was slightly lower than that achievable with neat diesel fuel at high-load conditions. Smoke was decreased by more than 20% in all 13 modes. While the CO and THC emissions of BD20 slightly decreased, the NOx emission of BD20 increased by 3.7%. Measured using the scanning mobility particle sizer (SMPS), the total number and total mass of the nanoparticles in the size range between 10.6nm and 385nm were reduced by about 10% and 25%, respectively, when going from D100 to BD20. The particle number and mass for both fuels were reduced by about 43% when going from with EGR to without EGR. When EGR was applied in the engine system, the particle number and mass were reduced by 24%, and 16%, respectively, when going from D100 to BD20.