可变喷嘴涡轮增压器对车用柴油机瞬态性能的影响

应用自行开发的柴油机瞬态工况测控系统和VNT电控系统,试验研究了可变喷嘴涡轮增压器对车用增压中冷柴油机瞬态工况下烟度、增压压力、燃油消耗量及空燃比等性能参数的影响规律。研究结果表明,在典型瞬态工况下适当减小VNT的开度可以改善进气响应、增加进气充量,选取合理的VNT开度可以降低排气烟度,低速增负荷工况排气烟度可降低34%,但喷嘴环开度过小,将导致增压器效率下降,进气量降低,排气烟度增加。     

车用涡轮增压柴油机VVE系统的模拟研究

提出了一种适用于车用四行程涡轮增压中冷柴油机的变充气系数 (VVE)系统 ,装在一台 6缸柴油机上进行了性能模拟计算。结果表明 ,在不放废气的情况下 ,最大扭矩工况可使柴油机得到足够的进气充量 ,标定工况时最高燃烧压力不超标 ,而且可以降低燃油消耗率和NOx 排放。VVE系统可代替车用增压柴油机高工况放气     

复合增压系统结构参数对车用柴油机进气过程的影响

开发了适合于车用柴油机的脉冲谐振废气涡轮复合增压系统，对不同的复合增压系统结构参数进行了试验研究，测录了进气压力波和充量系数，找到了一定的规律性，为谐振涡轮复合增压系统的深入研究奠定了基础。     

一种新型车用柴油机高增压系统的研究

介绍一种自动变进气正时的增压系统，简称AVIVT系统。它能降低机械负荷、热负荷、NOx及油耗率，用在车用高增压中冷柴油机中，可替代高速工况放气。阐明了替代高速工况放气的机理，提出了具体结构方案，并以计算实例对比说明了其优越性。     

重型货车节省能源的途径

(一) 发动机方面 重型货车已大部使用热效率较高的直接喷射式柴油机,为进一步节省能源,在发动机方面采取了下列措施,即增压中冷,低转速大扭矩,和可能在80年代实现的绝热燃烧室等。 1.增压中冷:重型货车采用增压中冷柴油机的日益增加,部分原因是为了符合美国对柴油机汽车排气污染中NOx含量的规定,中冷后进气温度降低,也就降低了燃烧温度,减少了     

可变涡流进气系统及其对柴油机性能和排放的影响

研制具有控制涡流副气道的可变涡流进气系统,是用于研究如何控制进气流入气缸的角动量,同时研究这种可变涡流进气系统对直喷式柴油机性能及排放量的影响。 较低的涡流可以减少初始阶段的燃烧量(在整个发动机转速和负荷范围内,这一阶段燃烧,是与NOx徘放量,最大气缸压力和缸内压力升高率有关的)。因此,在高速或部分负荷时,低涡流可提高燃料消耗率并降低NOx排放量。 带有这种可变涡流进气系统的涡轮增压中冷发动机,根据发动机的不同情况,选择最佳涡流强度,可以得到较高的低速扭矩、较高的功率和较好的冷起动性能。     

可调二级增压结合EGR策略对米勒循环柴油机性能的影响

针对米勒循环柴油机新鲜充量系数低,扭矩输出能力不足的问题,引入了电子增压器(E-Booster)技术,讨论可调二级增压结合EGR策略对米勒循环柴油机性能的影响。在1 400 r/min,p_(me)=1.85 MPa工况分析了米勒度、二级增压策略以及EGR对柴油机性能及NO_x排放的影响。仿真结果表明:无论是在进气门早关还是进气门晚关策略下,随着米勒循环的加深,缸内燃烧温度逐渐下降,使得NO_x排放降低,但由于循环充量系数的减少,扭矩输出降低;采用E-Booster可调二级增压方案,合理控制E-Booster的介入策略,提高进气压力,能够弥补米勒循环扭矩输出能力的不足,同时提高燃油经济性,但也会造成缸内最大压力和NO_x排放的增加;采用EGR策略则能够弥补由较高进气压力造成的不利影响,降低机械负荷和NO_x排放。米勒度、p_(in)、π_H、EGR率分别为M30、0.286 MPa、7%、10%时,p_(me,ac)提高0.03 MPa,同时NO_x排放下降0.47 g/(kW·h),有效改善了米勒循环柴油机动力性和NO_x排放。     

可变涡流控制直喷式柴油机排放的试验研究

研制了一种向螺旋进气道入口处喷射空气的可变涡流进气系统———控制涡流型可变涡流进气系统 ,试验研究了该系统对直喷式柴油机排放性能的影响。结果表明 ,该系统在不影响进气充量的情况下 ,可以明显改变直喷式柴油机颗粒 (PM)和 NOx 的排放量     

车用重型柴油机二级增压系统模拟及试验研究

针对某车用重型柴油机进行了二级增压系统匹配研究,根据产品开发目标要求选择了高、低二级增压器。采用GT-Power软件建立了二级增压柴油机仿真模型,并对柴油机外特性稳态工况性能进行了模拟计算,分析了二级增压系统能量分配对柴油机性能的影响规律。建立了二级增压柴油机测试平台,并进行了外特性、万有特性及排放特性试验。模拟及试验结果表明,二级增压系统可以大幅提高柴油机低速扭矩,改善燃油经济性,拓宽柴油机燃油经济性运行区域,大幅降低柴油机PM排放。     

二级增压系统压气机效率的优化策略研究

对配置在1台重型车用柴油机上的二级增压系统进行了性能研究。结果表明:放气阀开启的二级增压系统存在进气能力不足、压气机效率低的问题;关闭二级增压放气阀后,在中、低转速低负荷工况仅采用高压级增压器,而其余工况借助高压级涡轮旁通阀实现进气压力可调,增压系统压气机效率均可超过60%,且最大进气压力可达334kPa;针对不同工况采用不同增压形式,通过控制涡轮旁通阀开度使二级增压系统进气压力及压比分配得到有效调节,可以改善压气机效率及燃油经济性,为二级增压系统与重型柴油机的性能匹配提供技术参考。     

Effects of valve timing and intake flow motion control on combustion and time-resolved HC & NOx formation characteristics

In SI engines, valve events have a major influence on volumetric efficiency, fuel economy and exhaust emissions. Moreover, swirl and tumble motions in the intake charge also improve combustion speed and quality by stratifying the mixture as well as intensifying the mixing rate of air and fuel. This paper investigates the behaviors of an engine and the combustion phenomenon for various intake valve timings and intake charge motions using CVVT system and port masking schemes. Test condition includes a part load and a cold idle condition inclusive of a cold start of the engine. Time-resolved HC and NOx emissions were also measured at an exhaust port to examine their formation mechanisms and behaviors with fast response HC/NOx analyzers. In conclusion, the fast burning of fuel and improved combustion quality by enhanced charge motions reduced unburned HC emissions, and advancing the intake valve opening reduced HC as well as NOx. Furthermore, HCs during the cold transient phase and idle conditions decreased with recalibrated start parameters such as lean air-fuel ratio and spark retardation via the enhancement of intake charge motions.     

变海拔下米勒循环对柴油机及DPF性能的影响

基于某高压共轨柴油机建立了一维热力学仿真模型,对DPF选型进行了优化,并分析了不同海拔下米勒循环对柴油机及DPF性能的影响。结果表明,选择非对称结构以及适当增加载体目数都有利于降低DPF压降,同时可降低DPF对柴油机动力性、经济性及原始排放的影响。进气门早关可以降低柴油机有效燃油消耗率,提高热效率,降低NOx排放,但会导致颗粒物排放增加;同时可降低DPF压降,提高DPF捕集效率,且随海拔升高,进气门早关的时刻越小,作用越明显。在低海拔条件下,进气门晚关策略对柴油机动力性、经济性及排放特性均影响不大;在高海拔条件下,适当增加进气门晚关时刻可以改善柴油机性能。     

进气节流对柴油机低负荷性能影响的试验研究

在柴油机上加装节流阀是提升小负荷工况排温、改善排放的途径之一,但会对柴油机的其他性能造成影响。本研究通过给柴油机加装节流阀,研究了进气节流对柴油机小负荷工况性能的影响。试验结果表明:进气节流对柴油机的排温和NOx排放提升明显;柴油机进气节流后缸内压力下降,缸内平均燃烧温度、机械效率升高,滞燃期延长,燃烧始点后移;中低转速小负荷工况,随着节流程度的增加,燃油消耗率和烟度增加;高转速小负荷工况,一定范围内通过进气节流可以实现燃油消耗率和烟度的降低。2 500r/min,29N·m工况,保持EGR阀全开,随着节流程度的增加,NOx和烟度出现同时下降趋势,当空气流量由191.4kg/h降至140.6kg/h时,燃油消耗率、NOx、烟度分别下降了7.9%,58.1%,27.3%,排温提升了42.5%。     

Comparison of fuel efficiency and exhaust emissions between the aged and new DPF systems of Euro 5 diesel passenger car

This study was conducted to examine the impact of aged and new DPF systems of the Euro 5 diesel passenger car on fuel efficiency and exhaust emissions. Test diesel vehicle used in this study was equipped with diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) as aftertreatment systems, and satisfied the Euro-5 emissions standard. The displacement volume of engine was 1.6 L and the cumulative mileage was 167,068 km before the test. The FTP-75 test procedure was used, and the time resolved and weight based exhaust emissions of total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxides (NOx) were measured. The results show that the vehicle with the new DPF system has lower emissions of THC, CO and NOx than the aged one, and fuel efficiency also increased about 5 percent. The aged DPF system had higher backpressure due to the particulate matter (mostly in the form of ash) accumulated in the DPF. As was shown in the analysis using X-CT (X-ray computer tomography), the aged DPF system had particulate matter (PM) accumulated to a length of 46.6 mm. In addition, a component analysis of PM through XRF (X-ray fluorescence) analysis found that 50 % or more of the components consisted of the P, S, Ca, and Zn.     

Operating strategy for gasoline/diesel dual-fuel premixed compression ignition in a light-duty diesel engine

Environmental problems have become a major issue for diesel engine development. Although emission aftertreatment systems such as DPFs (diesel particulate filters), LNTs (lean NOx traps) and SCR (selective catalytic reduction) have been used in diesel vehicles, the manufacturing cost increase caused by this equipment can be hard to be control. Thus, it is better for engine emissions to be reduced by improving the combustion system. A dual-fuel combustion concept is a recommended method to improve a combustion system and effectively reduce emissions. Low reactivity fuel including gasoline and natural gas, which was supplied to the intake port by the FPI (port fuel injector), improved the premixed air-fuel mixture conditions before ignition. Additionally, a small amount of high reactivity fuel, in this case diesel, was injected into the cylinder directly as an ignition source. This dual-fuel combustion promises lower levels of NOx (nitrogen oxide) and PM (particulate matter) emissions due to the elimination of local rich regions in the cylinder. However, it is challenging to control the dual-fuel combustion because the combustion stability and efficiency deteriorate due to the lack of ignition source and reactivity. Thus, it is important to establish an appropriate dual-fuel operating strategy to achieve stable, high efficiency and low emission operation. As a result of this research, a detailed operating method of dual-fuel PCI (premixed compression ignition) was introduced in detail at a low speed and low load condition by using a single cylinder diesel engine. Engine operating parameters including the gasoline ratio, a diesel injection strategy consisting of multiple injectors and timing, the EGR (exhaust gas recirculation) rate and the intake pressure were controlled to satisfy the low ISNOx (indicated specific NOx) and PM emissions levels (0.21 g/kWh and 0.1 FSN, 0.040 g/kWh, respectively) as per the EURO-6 regulation without any after-treatment systems. The results emphasized that a well-constructed dual-fuel PCI operating strategy showed low NOx and PM emissions and high GIE (gross indicated fuel conversion efficiency) with excellent combustion stability.     

Evaluation and visualization of stratified ultra-lean combustion characteristics in a spray-guided type gasoline direct-injection engine

To comply with reinforced emission regulations for harmful exhaust gases, including carbon dioxide (CO₂) emitted as a greenhouse gas, improved technologies for reducing CO₂ and fuel consumption are being developed. Stable lean combustion, which has the advantage of improved fuel economy and reduced emission levels, can be achieved using a sprayguided-type direct-injection (DI) combustion system. The system comprises a centrally mounted injector and closely positioned spark plugs, which ensure the combustion reliability of a stratified mixture under ultra-lean conditions. The aim of this study is to investigate the combustion and emission characteristics of a lean-burn gasoline DI engine. At an excess air ratio of 4.0, approximately 23% improvement in fuel economy was achieved through optimal event timing, which was delayed for injection and advanced for ignition, compared to that under stoichiometric conditions, while NO_x and HC emissions increased. The combustion characteristics of a stratified mixture in a spray-guided-type DI system were similar to those in DI diesel engines, resulting in smoke generation and difficulty in three-way catalystutilization. Although a different operating strategy might decrease fuel consumption, it will not be helpful in reducing NO_x and smoke emissions; therefore, alternatives should be pursued to achieve compliance with emission regulations.     

车用柴油机谐振涡轮复合增压系统的研究

本文介绍了所开发的适合于车用柴油机的脉冲振废气涡轮复合增压系统，对复合增压柴油机进行了试验研究，并与普通涡轮增压柴油机进行了对比，在较宽广的转速范围内测录了进排气管系中压力波动，充量系数及发动机性能参数，研究结果表明，采用该系统对改善增压柴油机低速性能和烟度有很大的潜力。     

DOC辅助DPF再生的二次污染研究

在氧化型催化转换器(DOC)前端的排气管中喷入柴油,通过提高柴油机尾气温度、燃烧并去除柴油机微粒捕集器(DPF)中的PM,实现了DPF再生。对整个再生过程中尾气成分进行分析和计算,发现碳氢化合物(HC)为主要二次污染物,且排放相对较大。通过试验方法,分别研究喷油流量和喷油时DOC前端排气温度对再生过程中HC排放的影响,并依此提出保温处理、分阶段喷油和低速再生等三项优化措施。优化后再生过程中HC排放降低了68%,且燃油经济性提高了21%。     

正丁醇-柴油对柴油机燃烧及排放影响的试验研究

通过配制不同正丁醇掺混比例的正丁醇-柴油混合油,在不改变供油提前角和燃油系统的条件下,测量了柴油机燃用正丁醇-柴油混合油的气缸压力、放热率以及NOx、炭烟等排放污染物,探讨了正丁醇掺混比例对柴油机燃烧过程的影响规律,分析了正丁醇对排放污染物的作用过程。结果表明:正丁醇掺混比例为0%,5%,10%时,低转速、低负荷工况下,缸内最大燃烧压力分别为6.2MPa,5.9MPa和5.8MPa,与燃烧柴油相比略有降低;高转速、高负荷工况时,缸内最大燃烧压力分别为7.5 MPa,7.6 MPa,7.7 MPa,与燃烧柴油相比稍有增加;随着正丁醇掺混比例增加,柴油机的CO和HC排放升高,在中低负荷下NOx排放有所降低,高负荷时升高明显,平均增加了6.4%,炭烟排放降低明显,燃用正丁醇添加比例为5%和10%时,在高负荷下炭烟分别下降了25%和36%。     

Adaptation Strategy for Exhaust Gas Recirculation and Common Rail Pressure to Improve Transient Torque Response in Diesel Engines

Fuel injection limitation algorithms are widely used to reduce particulate matter (PM) emissions under transient states in diesel engines. However, the limited injection quantity leads to a decrease in the engine torque response under transient states. To overcome this issue, this study proposes an adaptation strategy for exhaust gas recirculation (EGR) and common rail pressure combined with a fuel injection limitation algorithm. The proposed control algorithm consists of three parts: fuel injection limitation, EGR adaptation, and rail pressure adaptation. The fuel injection quantity is limited by adjusting the exhaust burned gas rate, which is predicted based on various intake air states like air mass flow and EGR mass flow. The control algorithm for EGR and rail pressure was designed to manipulate the set-points of the EGR and rail pressure when the fuel injection limitation is activated. The EGR controller decreases the EGR gas flow rate to rapidly supply fresh air under transient states. The rail pressure controller increases the rail pressure set-point to generate a well-mixed air-fuel mixture, resulting in an enhancement in engine torque under transient states. The proposed adaptation strategy was validated through engine experiments. These experiments showed that PM emissions were reduced by up to 11.2 %, and the engine torque was enhanced by 5.4 % under transient states compared to the injection limitation strategy without adaptation.