Active coolant control strategies in automotive engines

The coolant flow rate in conventional cooling systems in automotive engines is subject to the mechanical water pump speed, and high efficiency in terms of fuel economy and exhaust emission is not possible given this limitation. A new technology must be developed for engine cooling systems. The electronic water pump is used as a substitute for the mechanical water pump in new engine cooling systems. The new cooling system provides more flexible control of the coolant flow rate and engine temperature, which previously relied strongly on engine driving conditions such as load and speed. In this study, the feasibility of two new cooling strategies was investigated using a simulation model that was validated with temperatures measured in a diesel engine. Results revealed that active coolant control using an electronic water pump and valves substantially contributed to a reduction of coolant warm-up time during cold engine starts. Harmful emissions and fuel consumption are expected to decrease as a result of a reduction in warm-up time.     

Measurement of hydrocarbon and carbon monoxide emissions during the starting of automotive DI Diesel engines

Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions. Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly unfavorable for the combustion progress. Additionally, the catalytic converter is ineffective due to the low engine temperature. In conjunction with adequate engine settings (fuel injection and fresh air control), either the glow plugs or the intake air heater are activated during a portion of the engine warm-up period, so that a nominal engine temperatures is reached faster, and the impact of these difficulties is minimized. Measurement of gaseous pollutants during engine warm-up is currently possible with detectors used in standard exhaust gas analyzers (EGA), which have response times well-suited for sampling at such transient conditions. However, these devices are not suitable for the measurement of exhaust emissions produced during extremely short time intervals, such as engine starting. Herein, we present a methodology for the measurement of the cumulative pollutant emissions during the starting phase of passenger car DI Diesel engines, with the goal of overcoming this limitation by taking advantage of standard detectors. In the proposed method, a warm canister is filled with an exhaust gas sample at constant volumetric flow, during a time period that depends on the engine starting time; the gas concentration in the canister is later evaluated with a standard EGA. When compared with direct pollutant measurements performed with a state-of-art EGA, the proposed procedure was found to be more sensitive to combustion changes and provided more reliable data.     

Comparison of two injection systems in an HSDI diesel engine using split injection and different injector nozzles

The demand for reduced pollutant emissions has motivated various technological advances in passenger car diesel engines. This paper presents a study comparing two fuel injection systems and analyzing their combustion noise and pollutant emissions. The abilities of different injection strategies to meet strict regulations were evaluated. The difficult task of maintaining a constant specific fuel consumption while trying to reduce pollutant emissions was the aim of this study. The engine being tested was a 0.287-liter single-cylinder engine equipped with a common-rail injection system. A solenoid and a piezoelectric injector were tested in the engine. The engine was operated under low load conditions using two injection events, high EGR rates, no swirl, three injection pressures and eight different dwell times. Four injector nozzles with approximately the same fuel injection rate were tested using the solenoid injection system (10 and 12 orifice configuration) and piezoelectric system (6 and 12 orifice design). The injection system had a significant influence on pollutant emissions and combustion noise. The piezoelectric injector presented the best characteristics for future studies since it allows for shorter injection durations and greater precision, which means smaller fuel mass deliveries with faster responses.     

基于冷却液温度的内燃机能量流试验研究

内燃机能量流试验是评估不同控制策略下内燃机能耗和指明其改善方向的重要方法。通过试验对1台涡轮增压缸内直喷汽油机进行了基于冷却液温度的能量平衡分析,基于热力学定律,将能量平衡项分为有效功、冷却液损失、排气损失和通过辐射传热产生的未计入热损失。结果表明:小负荷时,随着冷却液温度的升高,燃油消耗率略有下降,NO_x排放量增加;全工况下,HC排放量随着冷却液温度的升高而减少,CO和CO_2排放量变化不大;有效功占比和排气损失占比随负荷的增大而增大,几乎不受冷却液温度的影响;冷却液损失占比随冷却液温度的升高而减小。     

Multiair~技术:突破性的空气管理策略

Multiair是一种新型电子液压发动机气门控制系统，通过发动机进气门直接控制进气，无须借助节流阀，因而有助于降低油耗，还可以通过控制燃烧减少污染物排放。Multiair可应用于各种汽油发动机，未来还可能开发用于柴油发动机。     

轻型汽油车海拔环境排放和油耗特性的研究

海拔高度增加会导致空气密度减小,氧含量下降而使发动机的燃烧变差,污染物排放增加,整车油耗也会发生变化。因此有必要对不同海拔地区的汽油车排放及油耗情况进行研究,目前国内对相关领域的研究还处于空白。本文利用我中心海拔环境仓对两辆轻型汽油车进行各海拔高度环境下的排放及油耗试验,并对其在相应条件下排放污染物的排放量和油耗情况进行分析和比较,最终得出轻型汽油车的排放及油耗随海拔高度的变化规律。     

Exhaust nanoparticle emissions from internal combustion engines: A review

This paper reviews the particle emissions formed during the combustion process in spark ignition and diesel engine. Proposed legislation in Europe and California will impose a particle number requirement for GDI (gasoline direct injection) vehicles and will introduce the Euro 6 and LEV-III emission standards. More careful optimization for reducing particulate emission on engine hardware, fuel system, and control strategy to reduce particulate emissions will be required during cold start and warm-up phases. Because The diesel combustion inherently produces significant amounts of PM as a result of incomplete combustion around individual fuel droplets in the combustion zone, much attention has been paid to reducing particle emissions through electronic engine control, high pressure injection systems, combustion chamber design, and exhaust after-treatment technologies. In this paper, recent research and development trends to reduce the particle emissions from internal combustion engines are summarized, with a focus on PMP activity in EU, CARB and SAE papers and including both state-of-the-art light-duty vehicles and heavy-duty engines.     

基于电控集成智能控制的柴油机降油耗技术研究

为了进一步降低商用车的燃油消耗和CO2排放,开展基于发动机工况需求的电控集成优化控制研究。以某直列4缸电控共轨柴油机为研究对象,以发动机水温为反馈,对发动机水泵、节温器等电控冷却系统零部件进行综合调节,实现快速暖机升温以及正常行驶中发动机水温恒定在最佳温度,并通过优化VGT,改善燃烧过程。试验结果表明,采用智能控制系统可将冷却水温控制在各工况所对应的最优冷却水温附近,基于发动机工况需求的电控集成优化控制可以降低柴油机油耗3.51%,充分验证了智能控制方案的可行性和有效性。     

Thermal anaysis of an electric water pump for internal combustion engine vehicles

An electric water pump for engine cooling system has an advantage which particularly in the cold start, the use of the electric water pump saves fuel and leads to a corresponding reduction in emissions. However, the electric water pump for internal combustion engine generates much more heat loss than that for hybrid electric vehicle or electric vehicle since it is operated by electric power of high current and low voltage. In this study, the fluid flow and thermal characteristics of the canned type electric water pump with an inverter integrated has been investigated under the effects of heat generation. The analysis conditions such as outdoor air temperature of 125°C, water pump speed of 6000 rpm, coolant temperature of 106°C and coolant flow rate of 120 L/min were used as a standard condition. Therefore, the thermal performance of the canned type electric water pump’s motor and inverter was evaluated by comparison with that of mechanical seal type. In the motor, the temperature reduced by over 10°C, and in the inverter, the amount of temperature decrease equaled to the maximum temperature difference, about 18.7°C. Also, canned type electric water pumps of variable materials were compared for the evaluation of thermal transfer performance for variable thermal conductivity of a can. The motor and inverter were cooled lower to 42°C at motor and about 40°C at inverter for reasonable selection of can’s thermal conductivity.     

不同辛烷值参比燃料HCCI燃烧特性的试验研究

对不同辛烷值基本参比燃料及其混合物在高速4缸柴油机上进行单缸HCCI燃烧试验,研究了燃料辛烷值、发动机冷却水温度、进气温度以及冷EGR率对HCCI发动机燃烧特性和排放特性的影响。结果表明;在同一当量比下,随燃料辛烷值增大,着火时刻推迟,燃烧放热速率降低,HC和CO排放增大。HCCI燃烧随负荷的增大、EGR牢的减小、进气温度和冷卸水温度的升高,着火时刻提前,燃烧放热速率加快。     

Effect of fuel injection strategies on the combustion process in a PFI boosted SI engine

A low-cost solution based on fuel injection strategies was investigated to optimize the combustion process in a boosted port fuel injection spark ignition (PFI SI) engine. The goal was to reduce the fuel consumption and pollutant emissions while maintaining performance. The effect of fuel injection was analyzed for the closed and open valve conditions, and the multiple injection strategies (MIS) based on double and triple fuel injection in the open-valve condition. The tests were performed on an optical accessible single-cylinder PFI SI engine equipped with an external boost device. The engine was operated at full load and with a stoichiometric ratio equivalent to that of commercial gasolines. Optical techniques based on 2D-digital imaging were used to follow the flame propagation from the flame kernel to late combustion phase. In particular, the diffusion-controlled flames near the valves and cylinder walls, due to fuel deposition, were studied. In these conditions, the presence of soot was measured by two-color pyrometry, and correlated with engine parameters and exhaust emissions measured by conventional methods. The open valve fuel injection strategies demonstrated better combustion process efficiency than the closed ones. They provided very low soot levels in the combustion chamber and engine exhaust, and a reduction in specific fuel consumption. The multiple injection strategies proved to be the best solution in terms of performance, soot concentration, and fuel consumption.     

二甲醚发动机的燃烧与排放研究

在一台2135直喷柴油机上，对燃油供给系统进行了适当的改造，测试了燃用二甲醚发动机的燃料喷射时刻、气缸压力和有害排放，计算分析了放热规律及滞燃期变化规律。研究结果表明，在供油提前角相同的情况下，二甲醚的喷射延迟比柴油长而滞燃期比柴油短，着火时刻落后于柴油；二甲醚的最大放热速率小，而燃烧持续期短；二甲醚发动机接近无烟排放，N0x排放浓度显著低于柴油机。     

低电导率乙二醇冷却液使用性能研究

质子交换膜燃料电池发动机正常运行时会产生大量热,其中热量的95%由冷却介质带走,而冷却液中离子含量高会导致燃料电池发动机绝缘问题,因此要求冷却液具有高散热性、低的腐蚀速率、高的密封材料兼容性,行业内通常要求电导率小于5μS/cm,传统的冷却液(电导率大于2000μS/cm)不满足质子交换膜燃料电池的使用要求,无法直接使用。本文长期跟踪氢燃料电池车辆运营2万公里左右,对其冷却系统使用的低电导率乙二醇冷却液性能进行全面的跟踪及研究,主要包括冷却液消耗、冰点值,并解释其原理。通过本文的研究为燃料电池低电导率冷却液的开发、标准的制定及车辆的运营维护保养提供了数据支撑及理论指导。     

发动机燃用水乳化柴油的研究进展

综述了柴油机燃用水乳化柴油的燃烧与喷雾特性、动力性与经济性及排放特性,对比分析了发动机燃用水乳化柴油与普通柴油在性能上的差异及其原因,总结了水乳化柴油在柴油机上的应用优化方法。结果表明:与柴油相比,乳化柴油着火滞燃期延迟,燃烧持续期缩短,喷雾贯穿距变长或相差不大,火焰升起高度增加;燃用乳化柴油时动力性下降,但有效热效率较柴油升高;乳化柴油可以明显降低NOx和炭烟排放,但多数工况下HC和CO排放有所升高,低转速和中低负荷工况下尤为明显;燃用乳化柴油时颗粒物数量浓度增加,体积浓度减小,且对于醛类和噪声排放并没有改善作用;添加合适添加剂或结合发动机技术协同作用,可以针对性地改善乳化柴油的燃烧过程,进一步起到节能减排的效果。基于燃料稳定性与燃料理化特性综合优化目标的燃料设计,以及适用于乳化柴油的高压共轨柴油机燃烧组织参数优化是未来的研究方向。     

Improving pollutant emissions in diesel engines for heavy-duty transportation using retarded intake valve closing strategies

A combined theoretical and experimental study has been carried out to determine the real potential of reducing pollutant emissions in a HD diesel engine by means of retarding the intake valve closing. The effects produced by this alteration of the basic operation cycle have been examined by a preliminary modelling study, and from the obtained results, a modified camshaft was manufactured with a delayed intake valve closing of 60 crank angle degrees. Single-cylinder engine tests were carried out with this modified camshaft, and the emissions and fuel consumption were recorded. The results showed that the retarded intake valve closing can enhance the premixed combustion phase, and thus simultaneously reduce soot and NOx emissions. Moreover, the combustion process attained is extremely tolerant to exhaust gas recirculation, and by adoption of this measure, Euro-5 emissions limits can be achieved at the tested conditions without after-treatment.     

冷却液温度为边界条件的柴油机起动试验研究

为了研究冷却液温度对柴油机起动过程初期燃烧不稳定性及排放的影响规律,在一台单缸直喷式柴油机上,利用缸压和单循环采样测试系统对柴油机起动初期单个工作循环的燃烧和排放进行了试验研究。结果表明:冷却液温度是影响柴油机起动过程不稳定的重要因素之一。较低的冷却液温度导致柴油机起动初期燃烧不稳定性增加,失火和不完全燃烧循环较多,从而导致HC排放升高,而且冷却液温度低造成的滞后燃烧会产生较高的CO排放。冷却液温度升高后,失火循环消除,同时着火延迟期明显缩短,最高燃烧压力升高,HC和CO排放显著降低,NOx排放升高,表明燃烧状况改善。     

单缸直喷柴油机涡流室燃烧系统外部增压的实验研究

为满足非道路用柴油机的排放法规,从改善柴油机缸内混合气形成质量出发,提出了直喷式柴油机涡流室燃烧系统;设计了柴油机外部增压系统,进行了新型燃烧系统在外部增压下性能的实验研究。结果表明,外部增压能降低柴油机的油耗和排放;增压压力为0.15MPa时,柴油机油耗率最低。增压压力为0.18MPa时,使用4×0.36×140°喷油嘴在供油提前角为8°CA、90%负荷下,NOx排放量仅为常压下的25%。     

汽油发动机水温传感器检测与故障分析

水温传感器的功能是检测发动机冷却液温度,并将温度信号转换为电信号传送给发动机电控单元,电控单元根据该信号修正喷油时间和点火时间,使发动机工况处于最佳运行状态。当水温传感器发生故障时,发动机会易出现冷、热车启动困难、油耗增加、怠速稳定性降低、废气排放量升高等等故障现象。     

Reduction of engine emissions via a real-time engine combustion control with an egr rate estimation model

Vehicle emissions regulations are becoming increasingly severe and remain a principal issue for vehicle manufacturers. Since, WLTP (Worldwide harmonized Light vehicles Test Procedures) and RDE (real driving emission) regulations have been recently introduced, the engine operating conditions have been rapidly changed during the emission tests. Significantly more emissions are emitted during transient operation conditions compared to those at steady state operation conditions. For a diesel engine, combustion control is one of the most effective approaches to reduce engine exhaust emissions, particularly during the transient operation. The concern of this paper is about reducing emissions using a closed loop combustion control system which includes a EGR rate estimation model. The combustion control system calculates the angular position where 50 % of the injected fuel mass is burned (MFB50) using in-cylinder pressure for every cycle. In addition, the fuel injection timing is changed to make current MFB50 follow the target values. The EGR rate can be estimated by using trapped air mass and in-cylinder pressure when the intake valves are closed. When the EGR rate is different from the normal steady conditions, the target of MFB50 and the fuel injection timing are changed. The accuracy of the model is verified through engine tests, as well as the effect of combustion control. The peaks in NO level was decreased during transient conditions after adoption of the EGR model-based closed loop combustion control system.     

Investigation into the development of a bus electrical cooling fan system

Manufacturers of commercial vehicles are facing a substantial increase of heat release into their cooling systems. The main sources for this increase are more stringent emissions leading to new combustion technologies and the increased power of these engines. The total increase in the cooling requirement may be up to 20% over the current level. At the same time, the noise levels must be decreased, and fuel economy has to improve. This forces manufacturers to consider new concepts and optimize the efficiency of the cooling system. A bus engine cooling fan system is one of the main means of vehicular fuel efficiency reduction. This is becoming a major factor in city noise, and the necessity of electromagnetic technical development is very great. This study features a highly effective BLDC motor for engine cooling fans with high effectiveness and low noise, which is most suitable for fan blade technical development and cooling fan performance evaluation technical development.