发动机临界爆震控制特性研究

对爆震的临界控制特性及发动机性能进行了试验研究，包括点火提前角变化控制规律、基本点火提前角变化影响和各缸爆震差异性，以及发动机的动力性和经济性的控制影响。爆震控制系统使发动机工作在轻微爆震或临界爆震状态下，追求最佳的动力性和经济性。试验研究表明，适宜的爆震控制对发动机性能影响是极其重要的，并具有明显优势。     

基于曲轴瞬时加速度分析的发动机启动过程着火判定与应用

提出不同于失火判定的基于曲轴瞬时加速度分析的发动机启动过程着火判定方法，即通过两次启动过程的瞬时加速度对比寻找喷油启动过程的着火始点。理论分析和试验表明该方法不仅可以准确识别着火始点，而且识别精度也从循环级提高到角度级。试验在一台6缸电控共轨柴油机上进行。     

电喷汽油机爆燃控制的策略及试验研究

介绍了BOSCH汽油机电喷系统爆燃识别及爆燃控制的策略,分析讨论了带有爆燃控制的发动机管理系统在协调发动机动力性、经济性与爆燃安全性等方面的优势,试验研究了不同爆燃情况下的发动机性能及排放的差异,以及系统过量空气系数和进气温度与爆燃边界点火提前角的关系。     

Combustion phase detection algorithm for four-cylinder controlled autoignition engines using in-cylinder pressure information

For several decades, the primary goal of the automotive industry has been to reduce harmful emissions and improve fuel economy. Gasoline engines are clean and powerful propulsion systems, but have poorer fuel economy than that of diesel engines. However, due to the development of new technologies such as variable valve timing and lift and direct gasoline injection, controlled autoignition (CAI) combustion can be realized. CAI engines combine the advantages of cleaner emissions and lower fuel consumption than conventional spark-ignition gasoline engines. In this study, a cylinder-pressure-based combustion phase detection method for CAI combustion is proposed. This method utilizes a normalized difference pressure (NDP), which is defined as the normalized pressure difference between the firing and motoring in-cylinder pressures. The proposed method was developed and validated with steady-state experimental data from an inline 4 cylinder, 2 L gasoline direct injection (GDI) CAI engine. Because the calculations in the NDP method are faster and simpler than in the conventional combustion phase detection method in CAI engines, this method can be embedded in a real-time controller. Furthermore, the proposed method displayed good accuracy in detecting the combustion phase and thus stabilized CAI combustion. Finally, the detailed experimental results are presented.     

换气与压缩过程对汽油机燃烧特性的影响研究

针对增压气道喷射汽油机进行了发动机换气与压缩过程对燃烧特性的影响研究,对比了两种状态下的气门升程与配气正时,基于发动机试验台架测试数据,重点分析了发动机动力性、经济性和燃烧特性。试验数据表明了配气相位的改变对燃烧有较大的影响,可使燃烧效率大幅度提高,爆震倾向减小。同时基于AVL-fire软件进行发动机进气与压缩过程三维CFD分析,分析结果表明:对燃烧特性的影响不能仅靠瞬态滚流比和缸内平均湍动能进行判断,真正影响燃烧的是火花塞附近湍动能的变化,即发动机换气与压缩过程对燃烧特性的影响来自压缩上止点火花塞附近的湍动能。     

强烈机械噪声下的爆燃控制策略

介绍了发动机爆燃产生的原因及影响,分析了点火时刻对发动机爆燃及性能的影响,阐述了发动机控制系统对爆燃的检测过程,对强烈高频机械噪声影响下发动机爆燃控制系统的爆燃检测及控制策略进行了试验研究.试验结果表明,对爆燃识别很差的气缸实施引导控制策略控制效果明显改善.     

Numerical analysis of the effect of inhomogeneous pre-mixture on the pressure rise rate in an HCCI engine using multi-zone chemical kinetics

The HCCI (Homogeneous Charge Compression Ignition) engine is an internal combustion engine under development, which is capable of providing both high diesel-like efficiency and very low NO_x and particulate emissions. However, several technical issues must be resolved before the HCCI engine is ready for widespread application. One issue is that its operating range is limited by an excessive pressure rise rate which is caused by the excessive heat release from its selfaccelerated combustion reaction and the resulting engine knock in high-load conditions. The purpose of this study was to evaluate the potential of thermal and fuel stratification for reducing the pressure rise rate in HCCI engines. The NO_x and CO concentrations in the exhaust gas were also evaluated to confirm combustion completeness and NO_x emissions. The computational work was conducted using a multi-zone code with detailed chemical kinetics, including the effects of thermal and fuel stratification on the onset of ignition and the rate of combustion. The engine was fueled with dimethyl ether (DME) which has a unique two-stage heat release, and methane which has a one-stage heat release.     

基于 GT-Power 的天然气发动机爆震分析与研究

为了改善增压天然气发动机的燃烧状况、提高发动机的性能,对某发电用增压天然气发动机爆震现象进行研究。利用 GT‐Power 软件建立了增压天然气发动机整机仿真模型,通过模拟数据与试验数据的对比验证了模型的准确性,然后在仿真模型中利用自主建立的爆震预测模型对天然气发动机的性能和爆震现象进行了模拟计算,并对得到的数值结果进行分析。结果表明：随着压缩比的增加,发动机发生爆震的可能性增大,爆震开始时刻提前,爆震强度增大,燃气消耗率呈现先减小后增大的趋势,压缩比为13时,燃气消耗率最小;随着点火提前角的增加,发动机发生爆震的可能性增大,爆震开始时刻提前,爆震强度基本不变,燃气消耗率变化趋势是先减小后增大,当点火提前角为－21°时,燃气消耗率最小。     

基于DDS技术的发动机爆震信号仿真研究

基于直接数字频率合成(DDS)技术,通过设计相应的硬件电路来模拟发动机的爆震信号,在发动机平均值模型的基础上添加改进的双区燃烧模型,用以计算分析缸内燃烧过程,进而预测、判断爆震,并以爆震等级强弱等信息作为模型的输出量,最终驱动硬件电路产生信号。对信号的发生及处理过程作了针对性的研究。试验结果表明,模拟信号的幅值、频率等参数均可调,实时性满足系统的要求。     

高负荷下应用米勒循环提升高压比汽油机热效率机理研究

对高负荷工况下应用进气阀早关(EIVC)或者迟关(LIVC)技术实现的米勒循环进行仿真计算,基于热力学第一定律比较分析两者改善高压缩比增压直喷汽油机热效率的机理。结果表明:几何压缩比的增加提高了发动机的理论热效率,但由于高负荷时的爆震限制使油耗恶化了1.9%;米勒循环的应用可以有效降低爆震倾向,与原发动机相比,采用EIVC与LIVC策略燃油经济性的分别提升2.4%和3.0%;对比分析EIVC与LIVC对汽油机热效率的影响发现,LIVC策略能使燃烧相位更加优化、缸内燃烧更为充分,使得其燃油改善效果好于EIVC策略。     

Using multiple regression analysis to estimate the contributions of engine-radiated noise components

The respective contributions of combustion noise, mechanical noise, load-dependent noise and other engine noise components must be identified in order to devise effective measures for reducing diesel engine noise under full load operation. This paper describes a method for estimating the contributions of engine noise components using multiple regression analysis. With this method, the engine noise level is regarded as a criterion variable and the cylinder pressure level and engine torque as explanatory variables. The accuracy of this method has been confirmed by comparing the results with experimental data. Some examples of its application are also presented.     

Knock in dual-fuel diesel combustion with an E85 ethanol/gasoline blend by multi-dimensional simulation

In this paper, knocking combustion in dual-fuel diesel engine is modeled and investigated using the CFD code coupled with detailed chemical kinetics. The ethanol/gasoline blend E85 is used as the primary fuel in a dual-fuel combustion concept based on a light-duty diesel engine equipped with a common-rail injection system. The E85 blend is injected and well mixed with intake air in the intake manifold and is ignited by the direct injection diesel fuel. A 46-species, 187-reaction Multicomponent mechanism is adopted to model the auto-ignition process of the E85/air/diesel mixture ahead of the flame front. Based on the model validation, knocking combustion under boost and full load operating condition for 0 %, 20 %, 50 %, as well as 70 % E85 substitute energy is simulated. The effects of E85 substitute rate and two stage injection strategies on knock intensity, power output, as well as location of the auto-ignition initiation is clearly reproduced by the model. The calculation result shows that, for a high E85 rate of 50 % and 70 % with single injection strategies, the most serious knock and the origin of auto-ignition always occurs far away from where the flame of diesel spray is first generated, at the center of combustion chamber, due to higher pressure wave, relatively richer E85 mixture and longer distances of flame propagation. The two stage injection strategies with a small amount of diesel pilot injection ahead of the main injection primarily influence the ignition behavior of the directly injected fuel, leads to a lower pressure rise rate and a reduced propagation distance, both of which contribute to the attenuation of knock intensity for a higher E85 rate.     

内燃机燃烧过程光纤传感器光电探测技术的研究

论述内燃机燃烧过程新型光纤传感器光电探测技术研究的初步成果，介绍光探测系统的主要构成及其在燃烧探测中的应用。研究表明，光纤探测系统对实现燃烧过程的燃烧时间、爆震、循环稳定性、温度及燃烧产物成分等多项燃烧特征的准确测量向步探测意义重大，光纤传感器是探测能力宽和具有良好发展应用前景的内燃机燃烧分析测试传感器。     

基于响应面法的内燃机曲轴优化

针对内燃机曲轴的结构强度问题,以内燃机实际运行工况下整体曲轴有限元仿真为基础,通过中心组合试验方法进行采样,运用最小二乘法、显著性分析和拟合精度检测,构建并修正了曲轴结构强度计算的响应面模型,选择关键几何结构参数为设计变量,采用模拟退火与直接搜索相结合的协同优化方法对响应面模型进行优化。对某内燃机曲轴的优化算例表明,该优化方法能大大提高曲轴设计的优化效率,具有较高的精度。     

可变气门正时汽油机控制不佳引起爆震的研究

对发动机处于稳态进行爆震传感器信号的测定,分析信号与爆震之间的关系,得出各个工况稳态情况下声场分布情况,从而找到该稳态工况下爆震时的标定限制;同时在瞬态工况下对其进行验证,根据试验数据,相应地调整瞬态修正值。     

二茂铁和乙醇对HCCI爆震影响的试验研究

为了抑制HCCI发动机在高负荷时的爆震,通过在基础燃料(PRF90)中分别添加少量二茂铁和乙醇,在一台改造过的4缸柴油机的第4缸进行HCCI燃烧试验,研究其对HCCI发动机爆震的影响。试验结果表明,在发动机转速为1 400 r/min、相同当量比的稳态工况下,随着二茂铁质量分数和乙醇体积分数的增加,HCCI发动机缸压和放热率峰值降低,燃烧持续期增加,爆震得到有效抑制,负荷范围得到拓宽。在较小的质量分数下,二茂铁作用不明显,而过多的二茂铁、乙醇导致发动机失火可能性增加,二茂铁的质量分数应为0.035%左右,乙醇体积分数应为1%左右。     

TGDI 发动机超级爆震特性研究

研究了单次喷射及二次喷射对涡轮增压直喷汽油机某工况下超级爆震的影响,分析了二次喷射策略下进排气凸轮相位、进气温度、点火提前角、空燃比、发动机水温及曲轴箱通风系统对超级爆震的影响情况。结果表明,采用适当的二次喷射策略能有效抑制超级爆震的发生,增加发动机水温,降低混合气空燃比,适当提前排气相位可以减少超级爆震的频次,进气温度及点火提前角对超级爆震现象的改善不大。     

Knocking detection using wavelet instantaneous correlation method

In this study, we propose a new method for knocking detection that utilizes the vibration signal measured by a knock sensor under the knocking conditions known as a real mother wavelet (RMW), and carry out instantaneous correlation from the wavelet transform. We call this method the wavelet instantaneous correlation (WIC) method. The degree of similarity between the RMW and the vibration of the engine block was judged and only the knocking signal from the vibration of the engine block was extracted. The results obtained here show that the method proposed in this study is useful for knocking detection even if the engine speed is very high at 6000 rpm.     

Application of a thermodynamic model with a complex chemistry to a cycle resolved knock prediction on a spark ignition optical engine

A combination of experimental and numerical methodologies is proposed for the investigation of knocking in spark ignition engines to aid in better understanding the physical and chemical processes that occur and to exploit the capabilities of a developed computational tool. The latter consists of a thermo-fluid dynamics model, which is part of an advanced 1-D fluid dynamics code for the simulation of the entire engine, and a complex chemistry model, which can be embedded into the thermo-fluid dynamics model using the same integration algorithm for the conservation equations and the reacting species. Their mutual interaction in the energy balance will be considered. The experimental activity was carried out in the combustion chamber of an optically accessible, single-cylinder P.F.I. engine equipped with a commercial head. The experimental data consisted of optical measurements correlated to the combustion and auto-ignition processes within the cylinder. The optical measurements were based on 2-D digital imaging, UV visible natural emission spectroscopy and the chemiluminescence of radical species (OH and HCO). The engine parameters, the pressure signals of the related data and optical acquisition are compared on an individual cycle basis in the simulation by running the engine at a constant speed and varying the spark advance from normal combustion to heavy knock conditions.     

A control strategy for parallel hybrid electric vehicles based on extremum seeking

An energy management control strategy for a parallel hybrid electric vehicle based on the extremum-seeking method for splitting torque between the internal combustion engine and electric motor is proposed in this paper. The control strategy has two levels of operation: the upper and lower levels. The upper level decision-making controller chooses the vehicle operation mode such as the simultaneous use of the internal combustion engine and electric motor, use of only the electric motor, use of only the internal combustion engine, or regenerative braking. In the simultaneous use of the internal combustion engine and electric motor, the optimum energy distribution between these two sources of energy is determined via the extremum-seeking algorithm that searches for maximum drivetrain efficiency. A dynamic programming solution is also obtained and used to form a benchmark for performance evaluation of the proposed method based on extremum seeking. Detailed simulations using a realistic model are presented to illustrate the effectiveness of the methodology.