电动汽车 CO2热泵空调制热性能分析

为提升电动汽车CO2热泵空调的系统性能及扩宽热泵空调的使用温区，构建了回热器+补气增焓的跨临界CO2系统，通过建立数值模型对该系统的制热性能进行了仿真分析。研究结果表明，气体冷却器压力对制冷系数 （Coefficient of Performance，COP） 影响较大，且存在最优气体冷却器压力和中间补气压力使COP达到最大值；中间补气过程能有效提升COP和制热量，且能有效降低压缩机排气温度；回热器过热度对COP和制热量影响较小，但会导致压缩机排气温度上升。     

3-D numerical and experimental analysis for airflow within a passenger compartment

People use cars so frequently that they always consider the air-conditioning, and thermal comfort of the driver and passenger when buying a new car. Therefore accurate simulation of the thermal performance of automobile air conditioners to improve human comfort has become increasingly important. In order to improve the thermal comfort of passengers, 3-D flow motion and thermal behavior within vehicles must be analyzed. In this paper, a numerical simulation was used to investigate thermal behavior in a vehicle. Because air temperature at an air vent is related to the cooling capacity of the air conditioner, the cooling capacity was calculated using ɛ-NTU (effective number of transfer unit) theoretical equations. Using the air temperature relationship between inlet and outlet vents as boundary conditions, a 3-D unsteady κ-ɛ turbulent model was used to give a transient analysis simulation of the temperature field and flow conditions in a vehicle’s passenger cabin. Cooling cycle analysis and conjugate heat transfer analysis at the inside surface of the cabin’s ceiling, floor and sides were also considered. The predicted temperature distributions in the vehicles passenger cabin were in good agreement with those obtained experimentally.     

Experimental studies on the heating performance of the PTC heater and heat pump combined system in fuel cells and electric vehicles

In this study, a combined system consisting of a heat pump and a PTC heater was developed as a heating unit in electric vehicles. The system consists of a compressor, a condenser, an evaporator, an expansion device and a PTC heater. Experiments were conducted to examine the steady-state performance and dynamic characteristics of this system. The compressor speed, outdoor air inlet temperature, and indoor air inlet temperature were varied, and the performance of the system was experimentally investigated. The heating capacity, compressor power consumption and COP were obtained. Warm-up experiments were performed to investigate the dynamic characteristics of the system with a heat load of 1.5 kW in the indoor chamber. For the heat pump system, the PTC heater and the combined system, the heating performance and efficiency were investigated to determine an optimal control method. The results of this study agree well with the experimental results available in literature. This study provides experimental data of good quality for heating system design and the development of electric vehicles.     

Performance of air conditioners with a gas-liquid separation condenser and one-tank laminated evaporator

In this study, a parallel flow condenser and laminated evaporator for an automotive air-conditioning system were modified to improve performance. Gas-liquid separation type condensers, in which the condenser and receiver drier are integrated, and one-tank laminated type evaporators were developed, and their performances were investigated experimentally using HFC-134a. Heat transfer characteristics in the condenser are examined by means of air temperature, air velocity entering the condenser and inlet pressure of the refrigerant; heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, flow rate of air, outlet pressure of refrigerant and superheat. Pressure drops for both evaporator and condenser are also measured, and correlations for pressure drop are derived for the condenser and evaporator, respectively. Air velocity and mass flow rate of the refrigerant have a significant effect on the overall heat transfer coefficient, and flow pass is not significantly influenced by the cooling capacity of the condenser. The overall heat transfer coefficient of the evaporator increases as air flow rate, air temperature and relative humidity increases.     

Experimental study of EGR cooler regeneration aided by oxygen-fed NTP and air-fed NTP

Based on non-thermal plasma (NTP) technology fed by oxygen and air as the gas source respectively, the experimental system of exhaust gas recirculation (EGR) cooler regeneration was built to do a study at different regeneration temperatures. By measuring the concentration of main active substance and CO_x in regeneration process, the influence of temperature on regeneration aided by oxygen-fed NTP and air-fed NTP was investigated. The experimental results indicate that EGR cooler can be regenerated both by air-fed NTP and oxygen-fed NTP at a wide temperature range of 18 °C ～ 300 °C. By comparison of the regeneration with oxygen-fed NTP and air-fed NTP, it can be easily known that the regeneration effect is most remarkable at 150 °C with oxygen-fed NTP and at 120 °C with air-fed NTP. In addition, when the temperature is below 150 °C especially at 120 °C, the regeneration efficiency of air-fed NTP is lower than oxygen-fed NTP, nevertheless, when the temperature is above 150 °C, air-fed NTP has a superiority in regeneration and the higher the temperature is, the more obvious the superiority will be.     

Analysis of the performance of the evaporator of automotive air conditioning system

The purpose of this research was to establish a theoretical model for the evaporator of automotive air conditioning system and conducting simulations to evaluate the effect of operation parameters, environmental conditions, and design parameters on the performance of evaporator. An automotive air conditioning system primarily consists of four components: the compressor, the condenser, the refrigerant controller, and the evaporator. The refrigerant flow in the evaporator can be divided into two regions: the evaporating region and the superheat region. The refrigerant in the first region is a two-phase flow, while the refrigerant in the latter region is in the state of superheated vapor. The air flowing through the interior of the evaporator can also be divided into two zones: the unsaturated zone and the saturated zone. Water vapor is condensed in the saturated zone while in the unsaturated zone, no water condenses. Because the refrigerant flow and the airflow are perpendicular to each other, the distribution of refrigerant in the evaporating region and the superheat region does not coincide with the distribution of air in the unsaturated zone and the saturated zone. This study examines the effects of different design parameters, environmental conditions and operating parameters on the cooling capacity and superheat of an air conditioning system. Design parameters include the length of the refrigerant channel, the length of the air channel, and the thickness of the fins. Environmental conditions include the air inlet temperature and absolute humidity. Operation conditions include the refrigerant inlet enthalpy, inlet air flow rate, and refrigerant mass flow rate. Results of simulation demonstrated that fins with 50 micron meters width has the greatest cooling capacity for identical outer dimensions; thicker or thinner fins only decreased cooling capacity. Under different outer dimensions, longer refrigerant tubes and air channels created a greater cooling capacity. However, the increase in cooling capacity becomes less and less if the refrigerant flow was fixed because the heat transfer capability of the gaseous refrigerant was limited. In this study, an increase of 19% in cooling capacity can be reached as the length of refrigerant channels was increased, and the increased length of the air channels can promote the cooling capacity by 22%. Besides, it was found in this study that a decrease in the refrigerant inlet enthalpy, the inlet air flow rate, the air inlet temperature, and the inlet absolute humidity, or an increase in the refrigerant mass flow rate, would extend the superheat region and decrease the refrigerant’s superheat. It was also found that the cooling capacity of air conditioners is extremely sensitive to changes in the refrigerant mass flow rate and the inlet enthalpy, and variations more than 50% were found in the operating ranges examined in this study. However, changes in the inlet temperature, absolute humidity, and inlet air flow rate only resulted in variations between 10% and 20% in the examined ranges of conditions. Finally, a correlation among these variables and the simulated cooling capacity was obtained in this study, enabling the relevant researchers to evaluate automotive air conditioning performance under different environmental conditions and operation parameters more easily.     

Heat exchanger/catalytic system for reducing the exhaust emissions from diesel engines

A system has been researched over the past 3 years for reducing the exhaust pollutants from diesel engines for light commercial vehicles. The system researched achieves Euro 6 standards for reduction of polluting gases (CO, HC, PM, NO). It consists of 4 main sections: 1. A heater and heat exchanger (HE); 2. A CO/HC oxidising catalyst (D°C); 3. Pt catalyst on a diesel particulate filter (DPF); 4. A NO reducing reaction (SCR) within the DPF. The system operates as follows. The exhaust gas contains oxidising gases, namely both O₂ and NO₂. The levels of CO and HC are oxidised by O₂ to CO₂ for temperatures above 200°C. Carbon (PM) is oxidised to CO₂ by NO₂ but requires a temperature above 250°C. The operating exhaust temperature of 300°C is ideal for the removal of NO by using the Pt catalyst and the CO generated within the DPF. The heater is required to be able to raise the exhaust temperature at any time to 300°C in order to optimise the performance of the system, since diesel engine exhaust temperatures vary between 160°C (slow speeds) to 350°C (high speeds). Considerable heat is required (??3 kW) to maintain the exhaust gas for a 2l engine at 300°C for engine idle conditions. Therefore a heat exchanger is required to re-circulate the input heat and thereby reduce the maximum power consumption to a maximum of 500W over the engine full operating test cycle. This energy is supplied by the engine battery and alternator. Experimental results have been obtained for the exhaust from a Kubota diesel engine and the reductions in exhaust emissions of 83% (CO/ HC), 58% (NOx) and 99% (PM) were obtained. The PM was continuously cleaned so that there was no build up of back pressure.     

质子交换膜燃料电池系统建模与仿真分析

本文基于Amesim软件建立完整的燃料电池系统模型,包含电堆、空气系统、氢气系统和冷却系统模型,研究系统操作条件变化对系统性能的影响,结果表明,该模型可对空气计量比、电堆空入压力、电堆氢入压力、电堆水入温度等参数进行敏感性分析,并选出了最优系统运行操作条件及其对应的系统功率和效率输出,支持系统开发和操作条件优化。     

Experimental evaluation of SOF effects on EGR cooler fouling under various flow conditions

An experiment was conducted to characterize the effects of SOF on EGR cooler fouling. A removable singletube test rig combined with a soot generator was developed to represent an EGR cooler and diesel exhaust gas. The use of a soot generator, which controlled the size and concentration of soot particles, enabled independent variables to be completely controlled. Either n-dodecane or diesel lube oil as substitute SOFs were vaporized and injected into the test rig to evaluate their effects on the growth of PM deposits and the degradation performance of the EGR cooler. Coolant temperature, which seemed to be associated with SOF content, was chosen as an independent variable, and PM deposit mass per unit area and the effectiveness drop versus time increased as the coolant temperature decreased. The PM deposit mass per unit area and effectiveness drop had maximum values at a coolant temperature of 40°C for every n-dodecane injection rate. For substitute SOFs tested in this experiment, the deposit mass increased when either n-dodecane or diesel lube oil was injected, but the effect of lube oil was more significant. Diesel lube oil seemed to have a stronger effect on the reduction of thermal conductivity by filling pores in the deposits. When diesel lube oil was injected, the deposit mass per unit area increased 127% compared to dry soot without injection. The effectiveness drop after 10 hours increased only 12.5%.     

车用燃料电池发动机热管理系统研究

建立了车用燃料电池发动机热管理系统模型,该模型能考虑系统内各部件间及部件与电池堆间的相互影响;应用该模型计算分析了某65 kW车用燃料电池热管理系统对燃料电池堆性能的影响、热管理系统运行参数的控制依据和散热器布置形式的影响等。结果表明,应主要通过调节冷却风扇转速来调整电池堆温度,通过调节冷却水泵来保持电池堆进出口水温温差;散热器并联要优于散热器串联。     

Numerical analysis and experimental study on the performance optimization of cold storage heat exchanger integrated with evaporator

The ISG (Idle Stop and Go) systems are commonly used in modern automobiles because they are economical and environmental friendly technology. However, when a vehicle stops, the air-conditioning system stops, resulting in thermal discomfort to passengers in the cabin. This paper examines a cold storage heat-exchanger (CSH) integrated with an evaporator. The position of the cold storage parts inside a heat exchanger was analyzed through numerical simulations using FLUENT to create an adequate design for a CSH. The CSH performance was then examined with various airflow volumes and optimized experimentally in terms of the refrigerant flow circuit and fin density in the heat exchanger. Next, an experiment on the coldness release performance of the CSH was conducted in the air-conditioning system. The cold storage system with optimized CSH experiment resulted in lower air discharge temperatures (3.5 °C ~ 4.9 °C) than current air-conditioning systems, and delayed the warm-up by approximately 155 seconds to reach 18 °C temperature of air discharge. For this study, the CSH is an effective solution for the ISG-applied vehicles with less investment by transforming current air-conditioners’ structures more effectively.     

汽车空调系统工作原理及故障诊断

作为汽车的重要组成部分,空调系统一直都在汽车中扮演着重要角色。驾驶员可以借助空调系统,对车内环境(如温湿度等)进行调节,既可提高车内人员舒适度,还可消除附着在挡风玻璃的雾气,避免影响驾驶员的视线。但是经过长时间使用以后,汽车空调系统不可避免地会出现各种问题。文章首先对空调系统的运行原理进行了简单描述,然后分别介绍了空调系统制冷量不足、不制冷以及制冷效果时好时坏三种情况下的故障诊断。     

Experimental study on performance characteristics of cold storage heat exchanger for ISG vehicle

The ISG (Idle Stop and Go) system isvery useful in the automobile industry because it increases fuel consumption and reduces green house gas emissions. However, when the engine is on standby, the air-conditioning system does not work due to compressor inactivity, causing thermal discomfort to passengers. This study examines the thermal storage system, which is a cold storage heat exchanger integrated with a current evaporator. The experiments were conducted for an optimum cold storage heat exchanger design with various fin heights and densities, a number of stacking evaporator plates, refrigerant flow circuits inside the evaporator, and PCMs (Phase Change Materials) in the heat exchanger. The effects of coldness-release performance were examined with various ambient temperatures and air flow volume rates to the cold storage heat exchanger. The visualization of PCM’s freezing and melting was conducted with the cold storage heat exchanger. From the results, we found that the air discharge temperature of the air-conditioning system that was applied to the optimum cold storage heat exchanger was delayed around 540 seconds compared to the current air-conditioning system to reach 24 °C. Thus we can say that the cold storage heat exchanger integrated with an evaporator is an effective solution for ISG vehicles in maintaining thermal comfort in vehicle cabins during short engine stops.     

国六排放法规下的重卡冷却系统方案研究

文章介绍了国六排放升级,发动机对冷却系统散热量需求增加下的冷却系统布置方案研究。通过对国六发动机增加EGR冷却器后串联式冷却系统和并联式冷却系统方案工作原理分析,并应用原理进行整车方案设计,最终根据整车热平衡试验对整车设计方案进行论证分析,为国六车型设计开发提供数据及经验支持。     

双蒸发器汽车空调系统的改进

分析了传统的双蒸发器设计存在的出风口温差大、油循环率低等问题，对其汽车空调系统进行了改进，即采取了在顶置蒸发器处分液并在吸气管道上增加一个压力平衡装置的设计。通过环境模拟试验和油循环率试验对改进设计进行了验证。试验结果表明，蒸发器出风口温差明显减小，油循环率明显提高。     

安装参数影响散热器模块性能的风洞研究

为解决车辆冷却系统中多散热器模块的匹配问题,在风洞试验台上研究了间距和热介质进出口位置对某散热器模块性能的影响。试验散热器模块的第1排为中冷器和液压油冷却器,第2排为冷却水箱,第3排是变矩器油冷器。试验结果表明,增大间距可以提高散热器模块总的散热量,但对模块中单个散热器的影响差异很大;调换散热进出口位置有利于提高散热器的换热性能;调整以上两结构参数对模块的总压差影响不大。     

基于往复流风冷的动力锂电池热仿真正交分析

随着电动汽车销量的增加,动力电池的热安全问题日益受到关注,电池温度过高会影响电池的性能,严重时会导致热失控的发生。为研究锂电池的放电特性,探究不同因素对电池组往复流风冷散热的影响规律,基于外接UDF的Fluent仿真计算,利用正交试验,分析了入口风速、冷却空气温度、往复流周期三个参数对电池温度分布的影响规律。研究结果表明往复流周期对电池组温度分布均匀性的影响最大,入口风速对电池组最高温度影响最大,而冷却空气温度影响则相对较小。在此基础上,进一步获得了往复流散热性能的最优匹配参数。     

Carbon Deposit Incineration During Engine Flameout Using Non-Thermal Plasma Injection

In order to investigate the influence of initial regeneration temperatures on diesel particulate filter (DPF) regeneration, an experimental study of DPF regeneration was implemented using a dielectric barrier discharge (DBD) reactor, aided by exhaust waste heat after engine flameout. DPF trapping characteristics and carbon deposit mass were discussed to facilitate further data analysis and calculation. DPF regeneration was then investigated by comparison analysis of deposit removal mass, backpressure drop, and internal temperature change. The results revealed that a large amount of particulate matter (PM) was deposited in DPF with a high filtration efficiency of about 90 %. The deposit removal rate and percentage drop of the backpressure both maximized at the initial temperature of 100 °C. During DPF regeneration, the sharp rise of internal temperature indicated vigorous PM incineration and high CO₂ emission. The results successfully demonstrated DPF regeneration using non-thermal plasma injection during engine flameout, and prominent heat durability was achieved in this method.     

Cooling Efficiency According to Shape Changes to the Straight Ventilation Hole in Carbon-Ceramic Brake Disks

In this study, in order to examine the cooling efficiency of a carbon-ceramic brake disk, the temperature distribution of the disk, depending on the AMS (Auto-Motor-Sport) Fade mode, was analyzed using a numerical method. Two brake disks with different straight ventilation hole shapes were considered. The ventilation holes configuration was changed from base models in order to find a higher cooling efficiency disk design. In the Model A disk, the mean temperatures of the mid-plane and the entire disk, at the AMS Fade mode end time decreased 1.9 oC and 3 oC, hole length respectively. This was done by decreasing the length of the a2 hole from 94 mm to 59 mm. When a₂ hole length was increased from 94 mm to 128 mm, the mean temperature of the entire disk and the disk mid-plane increased 3.7 oC and 16.2 oC, respectively. This was due to the increased affined air stagnation in the disk. In the Model B disk, after removing stagnation region of the b₂ hole, the hole diameter expanded from 13 mm to 17.6 mm. As a result, the mean temperature of the entre disk and the mid-plane decreased 2.8 oC and 18.7 oC, respectively, (compared to the base model). As a result, increasing the surface area of the ventilation holes gave a higher cooling efficiency.     

水冷PEMFC热管理系统建模和控制

为了维持质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell,PEMFC)工作在合理的温度区间,文章首先建立了PEMFC热管理系统的电堆温度模型和电堆冷却回路模型,然后建立了PEMFC本体模型,并进行了本体模型的验证,采用基于Bang-Bang控制的热管理控制策略,并进行了离线仿真和快速控制原型试验。结果表明:在不同的电流负载变化的情况下,电堆能够很好地保持在目标温度(70±1)℃,散热器冷却水温度保持在目标温度(70±2)℃,达到了预期的控制效果。