电动汽车燃料电池增程器应用——小功率空气压缩机建模与仿真

将小功率燃料电池系统作为增程器是解决电动汽车续驶里程不理想的可选方法之一。针对适用于燃料电池增程器系统的滑片式空气压缩机,利用相关测试数据和热力学校正的方法,建立空气压缩机模型并进行相关仿真研究。仿真结果表明,该空气压缩机模型能够反映环境因素、出口背压和空压机转速对出口空气流量的影响,能为整个燃料电池增程器系统的设计和优化提供有用的信息。     

准均质充气压缩点火燃烧的模拟和试验研究

利用单区模型，结合详细化学反应动力学机理，模拟了DMM燃烧时的缸内压力和NO浓度及几种基团的浓度变化曲线；并将上述计算结果与试验结果进行了对比分析。结果表明该模拟能准确预测着火时间，并能合理预测缸内压力峰值和NO浓度变化趋势。利用该模型能指导优化发动机参数，更有效地组织发动机的燃烧过程。     

汽车发动机散热器特性仿真研究

针对常用的汽车发动机散热器,在大量试验和分析计算的基础上,建立散热器传热及阻力特性的数学模型,并在MATLAB/SIMULINK环境中建立其仿真模型。仿真结果与散热器试验数据基本一致,表明所建立的模型是可行的。     

切向进气道发动机缸内流场三维瞬态数值模拟

以动态网格技术为基础,采用三维、可压、黏性、湍流模型,应用控制容积法,对切向进气道发动机进气系统三维流场特性进行了瞬态数值研究。研究发现,在进气过程的初始阶段,缸内始终存在一对旋涡,并且沿气缸轴线向下缸内流体出现逐步融合的趋势;随着曲轴转角进一步增大,约在100°CA时缸内靠近活塞的横截面上出现单旋涡;在140°CA时,缸内横截面上大部分都只有单旋涡存在,只在靠近缸盖的横截面上有一个面积较大的主旋涡和一个面积很小的旋涡;当曲轴转角进一步增大,缸内仅存在一个单旋涡,流场压力趋于均匀。采用三维瞬态数值计算可获得稳态计算和试验难以得到的进气系统三维流场流动规律,为进气系统的优化设计提供可靠依据。     

基于响应面模型的智能台架供风系统开发

为解决瞬态工况下,汽车主动进气格栅（AGS）开度及风扇转速实时调整,换热器进风量时刻改变,热管理测试台架风机无法实时为换热器提供精准瞬态供风这一问题,应用计算流体力学（CFD）仿真技术,分析了换热器进风量与车速、AGS开度及风扇转速之间的关系,并构建了数学模型,模型预测误差小于6.6%。将该模型置于CANOE设备中,与VN1640设备及风机系统连接,可实时采集车速、AGS开度及风扇转速CAN信号,计算换热器进风量,从而控制风机输出相应风量,实现了台架风机为换热器提供精准、实时供风这一目标。     

Air flow trajectory and surge avoidance of centrifugal compressor under variable pressure operation of automotive fuel cells

The compressor of an automotive proton exchange membrane fuel cell requires severe dynamic performance under normal driving patterns. Because the air flow demand of the automotive fuel cell requires steep increase/decrease, it is very important to understand the air flow trajectory of the centrifugal compressor to avoid the compressor surge. In this study, a simulation model of an automotive fuel cell system with a dynamic compressor was developed to investigate the proper trajectory of air flow rate on a performance map of an air compressor. The dynamic response of the compressor shows that the cathode inlet and exit valves have a significant effect on surge evolution. In particular, the results showed that a proper combination of valve opening areas is required to avoid compressor surge. In this study, the original two valve approach was reduced to a single cathode exit valve control with fixed cathode inlet orifice. A surge rejection algorithm was also developed, based on the comparison of surge protection envelope pressure with actual measured pressure. The results show that surge evolution is effectively avoided by controlling the cathode exit valve.     

Tracked Air Cushion Vehicle Suspension Models: Analysis and Comparison

ABSTRACT

In this paper several dynamical models of fluid suspensions for tracked air cushion vehicles are analyzed and compared. Specifically, the models considered conform to: a fifth-order linear suspension, a nonlinear configuration with a constant supply pressure, a nonlinear model with compressor characteristics, and a sixth-order nonlinear model with a supply duct connecting the compressor to the cushion chamber. Nonlinearities included in the analysis are the flexible-skirted cushion capacitance, cushion entrance and exit orifice restrictions, feeding system duct fluid capacitance, and compressor pressure-flow characteristics. Temporal responses are obtained for guideway and external force inputs. Back flow conditions under which the supply compressor can stall are examined. It is shown that the general behavior resulting from linear analysis is in many respects similar to that obtained from the nonlinear analysis. Thus, a linear model could provide a good initial basis for a preliminary design and performance specifications.     

基于CFD的整车涉水性能仿真预测

发动机气缸进水将直接导致车辆熄火甚至发动机报废,因此避免发动机进气口水入侵是整车涉水性能开发的关注重点.本文采用流体力学的两相流模型和动网格模型建立整车涉水仿真模型.通过实时监测发动机舱水位高度、发动机进气口的水体积分数和进水量来预测整车涉水性能.对标发动机舱内水位高度的实验与仿真结果,验证了此方法可应用于车辆涉水性能...     

Tracked Air Cushion Vehicle Suspension Models: Analysis and Comparison

In this paper several dynamical models of fluid suspensions for tracked air cushion vehicles are analyzed and compared. Specifically, the models considered conform to: a fifth-order linear suspension, a nonlinear configuration with a constant supply pressure, a nonlinear model with compressor characteristics, and a sixth-order nonlinear model with a supply duct connecting the compressor to the cushion chamber. Nonlinearities included in the analysis are the flexible-skirted cushion capacitance, cushion entrance and exit orifice restrictions, feeding system duct fluid capacitance, and compressor pressure-flow characteristics. Temporal responses are obtained for guideway and external force inputs. Back flow conditions under which the supply compressor can stall are examined. It is shown that the general behavior resulting from linear analysis is in many respects similar to that obtained from the nonlinear analysis. Thus, a linear model could provide a good initial basis for a preliminary design and performance specifications.     

Model-based analysis of the mechanical subsystem of an air brake system

Most commercial vehicles such as buses and trucks use an air brake system, often equipped with an S-cam drum brake, to reduce their speed and/or to stop. With a drum brake system, the clearance between the brake shoe/pad and the brake drum may increase because of various reasons such as wearing of the brake shoe and/or brake drum and drum expansion caused by high heat generation during the braking process. Hence, to ensure proper functioning of the brake system, it is essential that the clearance between the brake shoe and the brake drum is monitored. In this paper, we present a mathematical model for the mechanical subsystem of the air brake system that can be used to monitor this clearance. This mathematical model correlates the push rod stroke transients and the brake chamber pressure transients. A kinematic analysis and a dynamic analysis of the mechanical subsystem of the air brake system were performed, and the results are corroborated with experimental data.     

Development of a model for an air brake system with leaks and a scheme for the estimation of the steady-state pushrod stroke

Brake systems in trucks are crucial for ensuring the safety of vehicles and passengers on the roadways. Most trucks in the USA are equipped with S-cam drum brake systems and they are sensitive to maintenance. Brake deficiencies such as leaks and out-of-adjustment of the pushrod are a major cause of accidents involving trucks. Leaks in the air brake systems drastically affect braking performance by decreasing the maximum attainable braking pressure and also increasing the time required to attain the same, thereby resulting in longer stopping distances. Out-of-adjustment of the pushrod leads to loss of braking torque even if no leaks are present in the air brake system. In this paper, we present a mathematical model for an air brake system in the presence of leaks, with a view towards developing a diagnostic system for the air brake system based on the models. Additionally, we present a scheme that estimates the severity of leak in terms of the mass flow rate of air leaking from the air brake system to the atmosphere. This scheme can be implemented using a simple look-up table. We also present a steady-state pushrod stroke estimation scheme, based on brake chamber pressure measurements in the absence of any leaks in the air brake system.     

Development and analysis of an air spring model

The analytical model of an air spring can be effectively used for the design of air spring equipped vehicles to provide better ride and handling characteristics along with various functions for passenger convenience. However, establishing a general model of an air spring poses particular difficulties due to the severe nonlinearities in the stiffness and the hysteresis effects, which are hardly observed in conventional coil springs. The purpose of this study is to develop a general analytic model of an air spring — one which represents the main characteristics of stiffness and hysteresis and which can be connected to a model of pneumatic systems desigined to control air spring height. To this end, the mathematical model was established on the basis of thermodynamics with the assumptions that the thermodynamic parameters do not vary with the position inside the air spring, that the air has the ideal gas property, and that the kinetic and potential energies of the air are negligible. The analysis of the model has revealed that the stiffness is affected by the volume variation, the heat transfer, and the variation of the air mass and the effective area. However, the hysteresis is mainly affected by the heat transfer and the variation of the effective area. In particular, it was revealed that the increase of the volume due to the cross-sectional area increases the stiffness, while the increase of the volume due to the other reason decreases it. In addition, the model was used to develop the sufficient stability condition, and the stability of the model was analyzed. The paper also presents the comparison between the simulation and experimental results to validate the established model and demonstrates the potential of the model to be usefully employed for the development of the air spring and its algorithm for use in a pneumatic system.     

虚拟样机技术在空气悬架系统设计中的应用

应用MSC.ADAMS及ANSYS软件,在ADAMS/Car[1]中建立了中型客车前空气悬架系统刚柔体耦合的动力学模型。模型的各类参数主要通过试验和Solidworks软件获得。在ADAMS/Car中,利用虚拟仿真试验对单纵臂式非独立悬架进行了多种性能分析,并结合空气悬架在设计及使用过程中出现的主要问题进行了探讨,提出了相应的解决办法。通过模型参数化分析及不同方案的仿真试验对比表明,利用基于ADAMS/Car软件建立的空气悬架系统模型可对悬架性能做出正确预测,对空气悬架系统的设计具有工程指导意义。     

分组选配法在旋叶式汽车空调压缩机中的应用

介绍如何利用分组选配法解决旋叶式汽车空调压缩机转子和气缸加工尺寸超差、装配合格率低的实际问题。     

二氧化碳汽车空调系统的动态仿真

文章建立了跨临界CO2汽车空调系统的动态仿真模型。利用移动边界法和平均空泡系数法对蒸发器建立了集总参数模型;利用移动边界法对气冷器和中间换热器分别建立了集总参数模型;由于压缩机和节流阀的热惯性较小,利用经验公式对其建立了稳态模型。计算结果同实验数据的比较表明,该动态模型比较准确地体现系统实际的动态性能。     

CA142空压机的正确使用与保养

简要介绍了ＣＡ１４２载货车所装用的空压机的结构和性能参数，详细分析了空压机的泵气和卸荷两工作过程，认为在使用中应注意管路中调压阀和安全空的压力值和空滤器的清洗问题。同时提出了对空压机卸荷失灵，空压机泵气不足，空压机温度高，空压机有异响等故障的排除方法。     

Design of a compressor-power-based exhaust manifold pressure estimator for diesel engine air management

In accordance with the development of hardware configurations in diesel engines, research on model-based control for these systems has been conducted for years. To control the air management system of a diesel engine, the exhaust manifold pressure should be selected as one of the control targets due to its internal dynamic stability and its physical importance in model-based control. However, it is difficult to measure exhaust pressure using sensors due to gas flow oscillation in the exhaust manifold in a reciprocated diesel engine. Moreover, the sensor is too costly to be equipped on production engines. Hence, the estimation strategies for exhaust manifold pressure have been regarded as a primary issue in diesel engine air management control. This paper proposes a new estimation method for determining the exhaust manifold pressure based on compressor power dynamics. With its simple and robust structure, this estimation leads to improved control performance compared with that of general observers. To compensate for the compressor efficiency error that varies with turbine speed, some correction maps are adopted in the compressor power equation. To verify the control system performance with the new estimator, a HiLS (hardware in the loop simulation) of the NRTC mode is performed. Experimental verification is also conducted using a test bench for the C1-08 mode.     

氢燃料发动机三维数值模拟研究

通过CFD软件STAR-CD建立了缸外预混合氢燃料发动机三维模拟仿真模型。对比氢燃料发动机与汽油发动机的性能发现,氢燃料发动机具有易点燃、火焰传播速度快、峰值压力及峰值温度高等特点。但氢气密度低,与空气形成的混合气单位体积的热值低,导致采用缸外预混合方式的氢燃料发动机比汽油机功率低15%左右。研究了过量空气系数和点火提前角对氢燃料发动机性能及NOx排放的影响,为提高氢燃料发动机的动力性能和排放性能提供依据。     

整条公路隧道通风与净化的三维数值模拟

现有的理论分析方法难以分析风速、污染物分布不均对隧道空气净化的影响,难以发现净化通风系统可能出现的问题。为准确地预测带有净化站的整条公路隧道内污染物的分布情况,建立考虑射流风机、车辆运动及净化站等因素的相互耦合作用的数值模型,对不同通风、净化和交通情况下隧道内的空气流动和污染物分布进行预测,并对模型进行验证。利用该模型对一采用旁通型净化站的实际公路隧道内的空气流动和污染物分布进行数值模拟。结果表明： 1）隧道内空气流动不是一维的,在旁通净化站处的主隧道中存在空气回流现象; 2）净化站的存在导致了局部通风量的下降,使净化段的主隧道污染物质量浓度突然升高,达到整条隧道的最大值; 3）在设计此类净化通风系统时,应该校核“与旁通风道平行的局部主隧道段末尾处”的污染物水平不高于相应的限值标准。     

车载储氢瓶快速充气后气体状态的预测模型

本文依照工程热力学基本理论建立了车载储氢瓶中氢气充入质量与氢气状态参数的预测模型,通过实验数据验证了模型的合理性。利用该模型分析了充氢温度对充气结束后气瓶内填充质量与最终温度的影响和环境温度对充气结束后车载储氢瓶内最终温度的影响。结果表明:车载气瓶内初始压力越低,可填充气体质量随充氢温度的升高其减少率越大,最终温度随充氢温度的升高其温升率越大;车载气瓶内初始压力越低,最终温度随环境温度的升高其温升率越低。同时该预测模型可以针对车载气瓶内不同的初始条件去预测气源氢气所需的最低预冷温度,为目前加氢站的气源氢气温度的控制提供理论依据,进而减少加氢站氢气冷却所需能耗。