Combustion instabilities and nanoparticles emission fluctuations in GDI spark ignition engine

The main challenge facing the concept of gasoline direct injection is the unfavourable physical conditions at which the premixed charge is prepared and burned. These conditions include the short time available for gasoline to be sprayed, evaporated, and homogeneously mixed with air. These conditions most probably affect the combustion process and the cycle-by-cycle variation and may be reflected in overall engine operation. The aim of this research is to analyze the combustion characteristics and cycle-by-cycle variation including engine-out nanoparticulates of a turbocharged, gasoline direct injected spark ignition (DISI) engine at a wide range of operating conditions. Gasoline DISI, turbo-intercooled, 1.6L, 4 cylinder engine has been used in the study. In-cylinder pressure has been measured using spark plug mounted piezoelectric transducer along with a PC based data acquisition. A single zone heat release model has been used to analyze the in-cylinder pressure data. The analysis of the combustion characteristics includes the flame development (0–10% burned mass fraction) and rapid burn (10–90% burned mass fraction) durations at different engine conditions. The cycle-by-cycle variations have been characterized by the coefficient of variations (COV) in the peak cylinder pressure, the indicated mean effective pressure (IMEP), burn durations, and particle number density. The combustion characteristics and cyclic variability of the DISI engine are compared with data from throttle body injected (TBI) engine and conclusions are developed.     

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。     

车用发动机润滑系统最低润滑油供给量研究

以某1.8VVT发动机为研究对象,建立了发动机润滑系统计算模型和轴承动力学模型,对主油道压力、轴承处润滑油流量、轴承轴心轨迹、最小油膜厚度等参数进行了计算分析。通过计算轴承、凸轮和VVT系统等润滑系统关键部件的润滑油压力需求,获得了润滑系统在不同发动机转速下的最低润滑油压力,该计算结果可为润滑系统设计提供理论依据和边界条件。仿真计算结果表明:发动机润滑系统进油压力对轴承润滑的最小油膜厚度基本没有影响;原润滑系统供给润滑油的液压功率实测值超出理论需求值,最高可达72%,原润滑系统存在发动机中高转速工况下供油过量的问题。     

摩托车发动机弹性悬置减振研究

发动机弹性悬置可以减小发动机激振引起的摩托车振动,设计弹性悬置的主要工作是根据发动机质量、转动惯量和弹性元件刚度来计算弹性悬置发动机系统的自然频率,并修改弹性元件结构、材料以尽可能满足√2倍最高弹性悬置发动机系统自然频率小于发动机最低工作激振频率这一条件。试验结果表明,发动机弹性悬置具有很好的减振效果。     

Development of an idle speed engine model using in-cylinder pressure data and an idle speed controller for a small capacity port fuel injected SI engine

An idle speed engine model has been proposed and applied for the development of an idle speed controller for a 125 cc two wheeler spark ignition engine. The procedure uses the measured Indicated Mean Effective Pressure (IMEP) at different speeds at a constant fuel rate and throttle position obtained by varying the spark timing. At idling conditions, IMEP corresponds to the friction mean effective pressure. A retardation test was conducted to determine the moment of inertia of the engine. Using these data, a model for simulating the idle speed fluctuations, when there are unknown torque disturbances, was developed. This model was successfully applied to the development of a closed loop idle speed controller based on spark timing. The controller was then implemented on a dSPACE Micro Autobox on the actual engine. The Proportional Derivative Integral (PID) controller parameters obtained from the model were found to match fairly well with the experimental values, indicating the usefulness of the developed idle speed model. Finally, the optimized idle speed control algorithm was embedded in and successfully demonstrated with an in-house built, low cost engine management system (EMS) specifically designed for two-wheeler applications.     

基于虚拟仪器的瞬时转速测试与分析

应用虚拟仪器技术开发了由LabVIEW,NI—PXI—6259多功能数据采集卡等构成的瞬时转速测量系统,运用直接模数转换法对YN30高压共轨柴油机瞬时转速进行了测试,得出其瞬时转速的变化规律:当发动机平均转速一定时,瞬时转速波形的幅值随负荷的增加而增大;当发动机负荷一定时,瞬时转速波形的幅值随转速的升高而降低;当发动机工况相同时,其瞬时转速波形的幅值随大气压力的升高而增大。     

基于一维、三维耦合分析的歧管式催化转化器结构优化

通过所建立的一维发动机进排气系统CFD模型和三维排气歧管CFD模型,得到了各工况下排气歧管压力损失等数据和排气歧管瞬态流场分布等数据.采用一维、三维耦合方法对某型号歧管式催化转化器进行了结构优化,并通过评价试验分别对原模型及优化后模型进行了性能检测.结果表明,优化后模型的背压降低,压力波动范围变小,压力损失也比较小,改善了内部流场情况,提高了发动机性能.     

复合材料降低柴油机噪声的试验研究

在标准半消声室,用B&K3560噪声测量分析系统对4110Q柴油机整机和油底壳、飞轮壳、喷油泵、摇臂罩等零部件的噪声进行了台架试验研究。试验主要测量了柴油机整机在全负荷、不同转速下的声压级和主要零部件近声场标定工况下的声强级,并进行了频谱分析,提出了降低柴油机噪声的具体措施。研究结果表明,用复合材料覆盖柴油机的复合油底壳、喷油泵、飞轮壳、摇臂罩表面后,在标定工况下整机噪声声功率级下降2.2 dB(A)。     

接头分析在汽车NVH正向设计中的应用

轿车的NVH性能在现代轿车开发中已经越来越受到莺视。结合国内某轿车NVH性能开发流程,对该轿车结构设计阶段的白车身进行了模态分析和静态刚度分析。分析结果显示,一阶振型为顶棚横摆,且频率与发动机怠速激励频率接近,车身扭转刚度低于竞争车型。由此分析了A柱接头刚度,并对其进行了结构和尺寸优化以提高其刚度,达到了消除顶棚横摆模态,提高扭转刚度值的目的。     

基于振动信号分析的发动机轴瓦间隙异常诊断

对发动机的主要激励源和传播路径进行了研究,在实验的基础上对测取的发动机轴瓦振动信号在时、频域进行了对比分析,比较了不同轴瓦间隙工况下的振动能量幅值,验证了理论研究的正确性,在此基础上,提出了一种简单有效的诊断方法,能够对发动机的故障进行较准确的诊断。     

装甲车辆非稳定工况驱动性能仿真模型

基于发动机和传动系统的动态过程，本文开发了一个装甲车辆非稳定工况的驱动性能仿真模型。对一台装甲车辆的加速过程进行了实例仿真计算，计算结果与实测值符合较好。这个仿真模型可以方便地用于装甲车辆非稳定工况动力性能的研究。     

Coordinated vehicle traction control based on engine torque and brake pressure under complicated road conditions

Vehicle traction control system has been developed to enhance the traction capability and the direction stability of the driving wheels through the tyre slip ratio regulation. Under normal situations, if the tyre slip ratio exceeds a certain threshold, the slip ratio of the driving wheel is regulated by the coupled interaction of the engine torque and the active brake pressure. In order to obtain the best driving performance on a road under complicated friction conditions, the driving torque and the active brake pressure, need to be decoupled and adjusted to avoid penalisation of each other. In this paper, a coordinated cascade control method with two sliding-mode variable structure controllers is presented. In this control method, the driving wheel slip ratio is regulated by adjusting the engine torque and the wheel brake pressure. Through the sliding-mode controller, the engine torque is tuned to achieve the maximum driving acceleration and then the active brake pressure is applied to the slipped wheel for further modification of the wheel slip ratio. The advantage of this control method is that through proper regulation, the conflict between the two control inputs could be avoided. Finally, the simulation results validate the effectiveness of the proposed method.     

汽车电控燃油喷射模拟系统的开发

以汽车电控燃油喷射系统基本喷油持续时间的控制为出发点,旨在开发一套汽车电控燃油喷射模拟系统的教学设备。通过进气歧管压力、发动机转速和基本燃油喷射持续时间(喷油脉宽)的测量,得到发动机的喷油脉宽三维脉谱图(MAP),存于单片机ROM中;设计模拟系统硬件电路并对电控单元编程,实时显示传感器检测到的进气歧管压力、发动机转速和喷油脉宽,并控制驱动喷油器工作。     

轿车车内噪声源识别的道路试验方法

以某国产国力样车的车内噪声控制问题为例，阐述通过道路试验进行噪声源识别的方法，对实验方法确定、测试信号选择以及数据处理的程度和方法进行了系统的阐述。分析结果，该车车内噪声主要由于发动机的二阶振动引起，而且在传递途径上存在很强的共振，车身顶棚和前围板是主要的噪声辐射源，对该车的发动机悬置系统和车身顶棚进行了有针对性的减振降噪措施，取得了最大降噪8dB(A)的良好降噪效果。     

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。     

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。     

车用二级增压系统匹配方法与模拟计算

为某发动机匹配一套二级增压系统,介绍了二级增压系统中高低两级压气机的匹配方法。建立了二级增压发动机计算模型,并进行外特性稳定工况模拟计算,确定发动机各转速下旁通阀的最佳开度。根据模拟结果,分析了旁通阀开度对高低两级增压器转速及压比的影响,确定了高低两级压气机压比和总压比随发动机转速的变化趋势。计算结果表明,匹配的二级增压系统基本满足发动机强化要求。     

基于声固耦合非线性系统的汽车车内噪声计算研究

采用具有线性和非线性连接子结构的自由界面模态综合法，建立整车系统声固耦合非线性动力学模型。用该模型对发动机激励产生的车内噪声进行数值仿真，并通过试验对仿真结果进行验证。     

Optimal design of the exhaust system layout to suppress the discharge noise from an idling engine

At the idle engine speed, the exhaust discharge noise is influenced by resonances in the whole system, which is composed of connecting pipes and silencers. This pipe resonance radiates a high level of low frequency discharge noise, which is dominated by the low order harmonics of the engine firing frequency. This low frequency noise deteriorates the vehicle’s interior noise level and quality. The following study attempted to optimize the layout of an exhaust system to minimize low frequency noise by changing the position of silencers and the lengths of inlet and outlet pipes in each silencer. After modeling the exhaust system using four-pole parameters, the acoustical performance of the system was evaluated using the system insertion loss. In the optimization, the virtual attenuation coefficient, which corresponds to the amount of attenuation coefficient required for the silencers, was calculated to find a minimum value for the layout. The simulated annealing method, which is also known as finding an optimal, was employed in searching for the optimized exhaust layout. Test examples of two cases, for two and six design variables, were used. When the number of design variables was two, the positions of the center and rear silencers were considered. When the number of design variables was six, the positions of the two silencers and the lengths of the inlet and outlet pipes were considered. Three typical layouts for the exhaust system of each case were designed, including the given system and an optimal system. By comparing the predicted and measured discharge noise level, it was confirmed that the optimized exhaust layout has a higher noise reduction than the other layout designs.     

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.