进气相位对三角转子气动发动机性能的影响

分析了三角转子气动发动机的配气系统特点,采用旋转阀式配气机构的工作过程,建立了发动机工作过程的数学模型,在进气压力为0．6MPa的情况下,针对不同的进气提前角和进气持续角对发动机的性能进行了数值仿真。仿真结果表明：进气相位在高速时对气动发动机性能影响大;设置合适的进气提前角对发动机的整体性能有利,且提前角随着发动机的转速的提高而增大;设置最佳的进气持续角对发动机的动力性能有利,且随着转速的提高进气持续角减小。因此在三角转子气动发动机设计工作过程中,需要设置合适的进气提前角和进气持续角,提高三角转子气动发动机的动力性能和经济性能。     

直线式汽车怠速控制电磁阀的仿真与研究

通过对直线式电磁控制阀的结构和工作过程进行分析,建立了怠速控制阀的动态力学模型,并利用仿真分析软件对怠速控制电磁阀在不同工况下的响应进行了特性分析;根据发动机进气模型,进一步研究了电磁阀控制参数与发动机怠速工况下的进气量、发动机转矩以及发动机转速之间的关系。对怠速控制系统的闭环设计,稳定怠速工况转速、优化点火提前角以及确定合理的空燃比等要求提供重要的参考。     

小型航空二冲程煤油发动机小负荷试验研究

将1台点燃式二冲程气道喷射汽油机改造为缸内直喷煤油发动机,在3000r/min小负荷工况下进行了点火提前角、喷气结束角、过量空气系数对性能影响的试验研究。结果表明,喷气结束角为50°和80°（上止点前）时,适当增大点火提前角,能使功率增加、油耗降低,但点火提前角不宜过大,否则会造成HC和CO排放量的增加;点火提前角为15°和30°（上止点前）时,适度提前喷气结束时刻,可以使功率增加、油耗和排放降低;另外,偏浓混合气有利于提高功率输出,偏稀混合气有利于降低排放。     

燃气热泵(GHP)系统热泵运行时的数值模拟研究

通过建立天然气发动机驱动热泵系统的数学模型,研究了供热工况下,点火提前角、压缩比、过量空气系数、发动机转速等参数对天然气发动机及整个热泵系统运行性能的影响,为天然气发动机的优化设计提供一定的理论依据,并且预测了燃气热泵的性能,证明了该系统具有较好的部分负荷特性.     

发动机关键配气相位角的分析与优化

发动机的四个配气相位角中,排气提前角和进气晚关角最为重要。运用AVL BOOST软件建立了某款汽油发动机的数值仿真模型,根据台架实验数据对模型进行了标定。保持原气门重叠角和升程不变,按每5°CA的间隔分别对排气提前角和进气晚关角进行改变,研究不同排气提前角和进气晚关角对发动机不同转速扭矩和功率的影响规律,确定最佳的排气提前角和进气晚关角。经过优化发动机的最大扭矩提高了5.39N·M,最大功率提高了2.82kW。     

气动发动机的试验研究

为优化气动发动机的设计,提高气动发动机的工作性能,在一台由R175柴油机改装的二冲程气动发动机上进行详细的台架试验研究,并提出两个评价气动发动机性能的新指标--比质量流量和总能量效率.采用变压器机油、冷冻油和特制机油等三种不同的润滑油进行气动发动机的润滑油试验,试验结果表明润滑油对气动发动机的经济性和动力性影响很大.针对水套中无水、注入常温水和开水等三种不同换热条件进行气动发动机的换热试验,试验结果表明加强换热条件对气动发动机的经济性和动力性帮助有限,但多级利用压缩空气可以提高气动发动机的总能量效率.利用三种不同进气提前角的进气凸轮,进行三种不同配气相位的速度特性和负荷特性试验.试验表明:气动发动机在低速阶段拥有较好的经济性和动力性,进气提前角为10 ℃A时,气动发动机性能最好.     

二冲程发动机初始喷油脉谱图的仿真及验证

以提高某小型二冲程发动机的动力性、经济性和稳定性为研究目标,运用发动机热力学数值计算软件建立原型机数学模型,通过全负荷条件下的缸内压力示功图、总功率和燃油消耗率对模型进行验证。在此基础上计算得到进气空气质量流量,确定各工况空燃比条件下的发动机初始喷油量,获得初始喷油脉谱图,由此开发了电控燃油喷射系统。经台架试验验证,发动机运转正常。     

影响发动机最佳点火提前角因素的对比分析

发动机点火提前角影响汽车发动机的动力性、经济性、排放等性能指标,为加深对最佳点火提前角受相关因素影响的理解,本文对发动机最佳点火提前角的影响因素进行了梳理与分析。     

LNG发动机最佳点火提前角的模拟优化仿真

在某系列天然气发动机点火控制系统基础上,提出利用神经网络在线优化点火提前角,从而解决天然气发动机在使用过程中因磨损、老化等造成最佳点火提前角发生变化的问题,达到提高天然气发动机的动力性和燃气经济性的目的。首先通过Matlab/simulink建立的LNG发动机模型,编写标定程序,得出初始点火提前角,然后设计神经网络。优化策略为在稳定工况时,利用自适应神经网络在线修正,得出实时最佳点火提前角;在工况变化较快时直接读取MAP图,得到点火提前角。最后利用GT-POWER搭建天然气发动机模型进行仿真并与实测数据进行比较。     

基于BOSCH ME7系统的起动匹配研究

基于BOSCH ME7系统对轻型汽油车起动工况标定匹配的研究,从发动机起动阶段的喷油、点火、进气、扭矩补偿等方面对发动机起动转速、空燃比、点火角等进行匹配,从而得到一个较优的起动性能.     

Performance and emission characteristics of a low heat rejection spark ignited engine fuelled with E20

In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (Al₂O₃) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and compared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A maximum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved.

     

Effect of spark plug protrusion on the performance and emission characteristics of an engine fueled by hydrogen-natural gas blends

Mixtures of hydrogen and natural gas are promising for improving efficiency and reducing harmful emissions in spark ignition engines, since limits of flammability can be extended while stable combustion is secured. In this research, the combustion characteristics of long electrode spark plugs were evaluated in a hydrogen blended with natural gas (HCNG) engine. Decreases in the flame propagation distance through the use of spark plugs can lead to increased burning rates and further improvement of fuel economy in HCNG engines. An 11-liter heavy duty lean burn engine was employed and performance characteristics including emissions were assessed according to the spark timing of the minimum advance for best torque (MBT) for each operating condition. Retarded MBT spark advance timing with long electrode spark plugs due to increased burning speed supported increases in engine efficiency and reductions of nitrogen oxide (NO_x) emissions. The lower positions of initial flame kernels due to the use of long electrode spark plugs were preferable to improvements of cyclic variability due to reduced flame front quenching, and carbon monoxide (CO) emissions at the flammability limit were also improved.     

中冷器对非道路柴油机性能影响的对比研究

随着非道路移动工程机械发动机机功率的不断增加,为满足柴油机的动力性和经济性指标,对增压空的气冷却提出了越来越高的设计要求。本文通过场地试验的方法对比研究了水冷中冷器与空冷中冷器对某款装载机柴油机工作特性的影响。试验结果表明,水冷中冷器相比于传统的风冷中冷器能更有效的降低柴油发动机的进气温度:水冷中冷器在铲装作业和高速跑工况下增压空气平均出温分别比空冷中冷器低27.6%和10.5%,柴油机扭矩提升为1.6%和6.3%,并且油耗降低了4.0%和2.5%。相对进气压力对柴油机经济性指标有一定影响,适当增加进气压力可以减少油耗。     

Aeration effects on the performance of a turbocharger journal bearing

Turbocharger bearings have to work under high temperature, and are moreover rotated at high speed. They have to be designed by overcoming the high temperature. The type of oil inlet port, the inlet oil temperature and the sort of engine oil should be designed, controlled and selected carefully in order to reduce the bearing's inner temperature. In this study, the influence of aerated oil on a high-speed journal bearing is also examined by using the classical thermohydrodynamic lubrication theory coupled with analytical models for viscosity and density of an air–oil mixture in a fluid-film bearing. Convection to the walls and mixing with supply oil and re-circulating oil are considered. The considered parameters for the study of bubbly lubrication are the oil inlet port's type, oil aeration level and shaft speed. It is found that the type of oil inlet ports and shaft speed play important roles in determining the temperature and pressure distribution, and the friction in a journal bearing at high-speed operation. Also, the results show that, under extremely high shaft speed, the high shear effects on aerated oil and the high-temperature effects cancel out each other. So, the bearing load and friction show almost no difference between aerated oil and pure oil.     

离心脱开型超越离合器弹流润滑分析

离心脱开型超越离合器是航空传动系统中的重要部件,具有低速楔合传动、高速离心脱开的特性,使离合器在不同工作模式下接触载荷与转速呈不同的关系,因此需针对不同工况下离心脱开型超越离合器弹流润滑性能进行分析.建立离心脱开型超越离合器弹流润滑模型,采用多重网格分析方法进行数值求解,分析进油温度与速度对超越离合器弹流润滑性能的影响...     

COMPOSITIVE EMISSION CONTROL SYSTEM OF GASOLINE VEHICLE

The working principle of a kind of compositive emission control system is inquired into, which includes exhaust heater, secondary air supplement, exhaust gas recirculation (EGR), thermal reactor and catalytic converter, etc. The purification effect of CO, HC and NOx emission of the gasoline spark ignite (S.I.) engine is studied. The entire vehicle driving cycle tests based on the national emission standard and a series of the gasoline engine-testing bench tests including full load characteristic experiment, load characteristic experiment and idle speed experiment are done. The results show that the system has a very good emission control effect to CO, HC and NOx of gasoline engine. The construction of the system is very simple and can be mounted on the exhaust pipe conveniently without any alteration of the vehicle-use gasoline engine.     

发动机缸套-活塞环摩擦磨损特性试验研究

利用缸套-活塞环摩擦磨损试验台研究了速度，温度，载荷，供油等因素对缸套-活塞环系统摩擦磨损特性的影响。试验结果表明，缸套-活塞环摩擦副在发动机工作循环中润滑状态不断发生变化。在试验条件下，温度对摩擦磨损有显著影响，载荷和速度对摩擦力的影响较小。     

进水温度对水润滑轴承润滑特性的影响

为研究进水温度变化对水润滑轴承润滑特性的影响,采用有限差分法建立水润滑轴承弹流润滑模型,分析不同进水温度和载荷条件下水润滑轴承润滑特性的差异,并且通过试验验证摩擦因数的变化规律。研究发现：随着进水温度升高,轴承的水膜压力下降,但在水膜压力峰区域最大水膜压力升高、最小水膜厚度减小、偏心率增大,表明进水温度升高对润滑性能有着负面影响;在相同的载荷和转速下,轴承摩擦因数随着进水温度升高而下降,且高载荷下进水温度对摩擦因数的影响更大。通过试验发现进水温度越高对摩擦因数变化的影响越大,不同进水温度下载荷越低,载荷的变化对摩擦因数变化量的影响越大。