Subcooled boiling is the most effective form of heat exchange in the water jacket of the cylinder head. Chen?s model is the most widely used correlation for predicting boiling heat transfer, but the selection of the correlation for the nucleate boiling is controversial. The work of this paper is to simulate the heat transfer process in the water jacket of the cylinder head with a horizontal rectangular channel that is heated on one side. Using the coolant flow velocity, inlet temperature and system pressure as variables, the heat flux and heat transfer coefficient were obtained. The results show that the increase of the coolant flow velocity can effectively promote the convection heat transfer, and the change of inlet temperature and system pressure will affect the occurrence of nucleate boiling. However, the Chen?s model predictions does not fit well with the experimental data. Four nucleate boiling correlations were selected to replace Chen?s model nucleate boiling correlation. The correlation proposed by Pioro coincides best with the experimental data. The mean error after correction is 18.2%.

The radiator of special vehicle often exposed to sand condition, and the sand have great influence on the performance of radiator, in order to figure out the impact, the physical model of a radiator is built, the three-dimensional numerical simulation of the gas and water flow field of the radiator is carried out by adopting discrete phase model (DPM) as well as the SIMPLE scheme. Then, the relationship between different factors (such as air velocity, sand particle size, sand concentration) and heat transfer coefficient are obtained by means of simulation, which provides a basis for the optimization design of the special vehicle radiator. A test bench is built, and the simulation is verified to be correct by comparing the simulation result with the test result.

高功率密度推进系统产热部件多,温度范围广,对车辆热管理系统提出了很高的要求.文章从推进系统冷却润滑需求分析、一体化热管理系统总体方案设计、一体化热管理系统建模分析、动力舱空气流动与传热CFD仿真、一体化热管理系统自适应控制技术、关键部件技术等方面分析了实现高功率密度推进系统热管理系统的若干关键技术及其研究方法.

为了研究不同海拔对车用散热器性能的影响,采用Fluent软件建立车用散热器仿真模型.由于散热器结构复杂,直接建模仿真计算量较大,将散热器翅片部分视作多孔介质模型,多孔介质参数通过对散热器单元仿真得到.结果表明:空气密度的下降是影响散热器传热性能的主要原因,随着海拔的升高,大气压力逐渐降低,空气密度随之减小,导致气体雷诺数相应减小,同时对流换热系数和散热量呈现下降趋势.海拔每升高1000 m,换热系数下降4.72％,散热量下降6.58％.

The combustion characteristics of a turbocharged diesel engine in a plateau environment have always been a focus of research on diesel engine power recovery. However, the influence of altitude on the empirical parameters of the combustion model has rarely been addressed in the literature. This paper presents a zero-dimensional combustion modeling method based on support vector machine (SVM). Taking a diesel engine as an example, the heat release rate data under different working conditions were measured on the test bench of a diesel engine at variable altitude. An SVM model was constructed and trained to predict the empirical parameters of the combustion model under varying altitude conditions, and the working process of the diesel engine was simulated. The results show that the working process simulation model with SVM prediction has better predictability. When the altitude increases, the average cylinder pressure and maximum pressure both decrease, the cylinder temperature and maximum temperature both increase, the combustion start point lags, and the combustion duration increases.

对前期封闭动力舱冷却风道热流场和温度场仿真结果进行综合分析,发现动力舱内部温度较高,且部件表面热量高无通风结构带走,长时间使用会影响柴油机可靠性和电子器件寿命.针对这个问题,在封闭动力舱装甲板处上方开孔增设换气风扇,在不影响整体结构和满足散热条件下,采用熵值法和加权规划法相结合方法,对冷却风道进行综合评价确定最优方案,应用实例分析表明,动力舱内主要部件的温度有效降低,该综合评价方法确定可行有效.

利用GT-Power软件建立了柴油机工作过程仿真模型,通过柴油机台架试验证实了模型的正确性,掌握了变海拔环境下柴油机在外特性工况下的性能变化规律,有效减少了试验周期并获得了较全面的柴油机性能参数.结果表明:随海拔高度的增加,柴油机的动力性和经济性同时下降,海拔每升高1 km,功率下降4％,燃油消耗率升高7.2％;同时缸内燃烧恶化,后燃现象严重,燃烧始点后移,海拔每升高1 km,燃烧始点平均后移0.8℃A.

建立了线性标定和非线性标定数学模型,对不同温度的校准源在不同标定方法及不同标定策略测试的结果进行了分析.利用相对误差较小的标定方法和策略进行了试验,利用阈值函数筛选出了有效样本数据,经过充分训练和验证,建立了基于径向基神经网络的光谱辐射亮度校正模型,最后搭建了装甲车辆排烟红外辐射测试系统,得到了排烟的光谱辐射亮度.结果表明,针对不同的目标温度,采用相应的标定方法和策略能够减少红外辐射测试仪标定带来的测量误差;装甲车辆排烟利用测试数据建立径向基神经网络光谱辐射亮度校正模型能够有效降低大气吸收对测试结果的影响,获得更加准确的排烟红外光谱辐射亮度,该方法具有工程应用价值.

针对高功率密度(HPD)柴油机与增压器在不同工况下匹配性差的问题,搭建发动机性能试验台架,对分别匹配固定截面涡轮增压器和可变喷嘴环增压器(VNT)后的某型HPD柴油机的性能指标进行了研究;研究结果表明,相对于固定截面涡轮增压器,HPD柴油机匹配VNT增压系统后,压气机出口压力在外特性中低转速时大幅上升,进气效率提高,柴油机最大转矩升高13.2％,转速储备系数由1.03增大至1.28,转矩储备系数由1.02增大至1.16,不同负荷工况下燃油消耗率均降低,最大降低幅度达28.7％,柴油机的动力和经济性得到全面改善.

为了更好地揭示坦克动力舱的热状态及红外辐射特性,提高坦克战场生存能力,以某型坦克为例,利用商业软件fluent建立了舱内空气与流动的CFD模型.对于动力舱内热边界条件,由汽车仿真分析软件GT-SUITE给出,装甲板的温度场计算采用流固耦合的方法,使其转化为系统内部的边界,并考虑了太阳辐射的影响.最后根据装甲板温度场建立红外辐射特性计算模型,得到了稳态工况下动力舱的热流场和装甲板红外辐射特性强度分布图,可为下一步动力舱内热流场优化和红外特性抑制提供依据.

This study aims to minimize the error of the infrared radiation characteristic measurement on the exhaust gas discharged by armored vehicle. Linear and nonlinear calibration mathematical models are established to analyze the results of several calibration tests in which different calibration sources with different temperatures, calibration methods, and calibration strategies are used. An experiment is carried out using the nonlinear calibration method with relatively small errors, valid blackbody experimental sample data are screened using a threshold function. After intensive training and verification, a spectral radiance correction model based on the radial basis function (RBF) neural network is established. Finally, an infrared spectral radiance test system specialized for armored vehicle exhaust gas is designed to measure the spectral radiance variation of the exhaust gas discharged by armored vehicle. The test results show that adopting different calibration methods and strategies for different target temperatures can reduce the measurement error caused by improper calibration of an infrared radiation tester. The RBF neural network-based spectral radiance correction model can effectively reduce the influence of atmospheric absorption on the test results, the determination coefficient of the trained model is 0.9975, and the maximum error of the specific emissivity is about 2.25%.

Since the internal heat transfer is a complicated process, the heat pipe heat exchanger of the engine has not been fully understood yet, which is originated from its extreme complexity. In theoretical studies, the involvement of two-phase flow and phase change processes usually simplifies the processing very much, and the model built differs too much from the actual one, resulting in reduced simulation accuracy. In this study, the prediction model of heat transfer and heat resistance of the heat pipe intercooler is established based on artificial neural networks (ANNs). Then the performance of the heat pipe intercooler from heat transfer and heat resistance aspects is investigated. The average relative error between the heat transfer prediction model and the test value is 3.6%, and the average relative error between the resistance prediction model and the test value is 12.68%, which shows that the prediction model can predict the thermal performance of heat pipe intercooler more accurately. Finally, the proposed model is applied to optimize the structural parameters of the heat pipe intercooler, and the optimal parameters are obtained accordingly. These optimal design parameters can provide the basis for further investigation and development of the heat pipe intercooler in diverse applications.

The CFD simulation model of the spray and combustion in the cylinder of the diesel engine was built by mean of the FIRE software and was checked through the test; the influence of the common rail pressure and the injection period on the velocity field, fuel-air equivalent ratio distribution and the temperature field were studied when the injection mass was constant; the influence of injection timing on the velocity field, fuel-air equivalent ratio distribution and the temperature field was studied when the common rail pressure and the injection period were constant. The study provided the foundation to match the high pressure common rail system parameters.

研究了VNI增压系统及其对柴油机性能的影响.通过涡轮增压器台架试验,研究了VNT增压系统不同叶片开度的涡轮流通特性;建立了HPD柴油机工作过程及VNT联合仿真模型;计算分析了VNT可调叶片位置变化对压气机出口压力、涡轮前压力、柴油机功率的影响规律,为HPD柴油机增压系统方案设计提供了依据.

军用车辆烟气辐射特性参数的仿真结果直接影响其排烟红外辐射数值的计算精度,为了提高仿真的效率和结果可信度,研究了烟气辐射计算模型的修正方法.首先建立了基于宽带к分布的军用车辆烟气辐射计算模型,通过对比仿真与测试结果,验证了模型的可信性.通过析因试验设计筛选出待修正模型参数,建立了基于Kriging插值的待修正模型参数与目标函数的替代模型.针对修正问题的无约束性和非线性,采用改进型萤火虫算法进行模型参数的迭代计算,并确定了最终解.研究结果表明,军用车辆烟气辐射计算模型的仿真精度和效率得到了提高,为军用车辆排烟红外辐射的仿真计算提供了理论参考.

为降低空气流通阻力、增加空气流量以及获得最大的防护能力,对装甲车辆进气和排气百叶窗结构优化进行研究.建立装甲车辆进气和排气百叶窗数值计算模型,根据冷却系统工作特点搭建冷却风道半实物仿真模型,对比分析优化前的仿真结果和台架测试结果,并给出了优化目标函数表达式.为解决优化效率低、计算量大的问题,确定设计变量并建立设计变量与目标函数之间关系的椭圆基神经网络替代模型.通过分析目标函数随设计变量的变化规律,采用基于多种群协同进化免疫的多目标优化算法对模型进行优化,确定了最终解.利用自组织神经网络对样本点进行数据挖掘,找到了内在规律.研究结果表明,优化后的进气和排气百叶窗在提高防护能力的同时,提高了散热性能.

The load spectrum compression only removes the small damage load of the crankshaft in the load spectrum of each section of the test field. In order to further form the bench test load spectrum suitable for the laboratory, it is necessary to compress and extrude the load spectrum after compression. Based on the method of kernel density estimation, the rain flow matrix extrapolation of crankshaft torsional and bending load is realized.

为了对装甲车辆的红外辐射特征进行研究,提出了综合考虑排烟热气和外表面装甲红外辐射特征的红外辐射信号建模方法.首先,利用GT和CFX软件联合仿真得到了排烟热气的温度、压力的分布,考虑排烟热气对排烟管红外辐射的吸收作用,建立了装甲车辆排烟装置总体红外辐射数值计算模型;然后,利用CFX软件模拟了外表面装甲的温度分布,提出了装甲车辆外表面装甲的红外数值计算模型,并通过试验验证了该模型的正确性;最后,计算了装甲车辆全方向上3～5 μm和8～ 14 μm波带上的红外辐射强度,得到了目标辐射随方向的变化规律.结果 表明:装甲车辆的红外辐射信号具有明显的方向性,在进行红外抑制设计时应提出针对性的措施.

为了对坦克排烟热气的红外辐射特征进行分析,以坦克某一典型行驶工况为例,分析了不同高度和距离对穿透率的影响.基于最新版的HITRAN中的数据,针对算例给出的参数,利用高分辨率气体红外辐射计算模型计算得到了红外辐射特性.针对坦克某一工况下的排烟,利用高分辨率气体红外辐射计算方法对红外辐射特征进行了模拟计算,并进行了试验测试,最后对计算结果进行了比较.结果 表明:大气的衰减作用主要是气体中的CO2和H2O分子的吸收作用造成的,在计算排烟热气的红外辐射特征时,需要考虑大气的衰减作用.相较于Curtis-Godson近似谱带模型法,采用高分辨率气体红外辐射计算模型能够更精确地得到光谱辐射亮度.

以某型12缸柴油机为研究对象,利用软件GT-SUITE中的GEM3D模块将柴油机三维模型离散成大量小体积模块,转换为一维模型.将冷却系统模型和柴油机工作过程仿真模型进行集成,同时考虑了摩擦产热,将集成模型作为一个研究整体,实现了边界条件的实时传递,得到了柴油机本体的温度和其内部高温部件温度场.相比传统三维方法,减少了计算时间.柴油机本体温度可作为动力舱流场和温度场分析的热边界条件,柴油机内部高温部件的温度场可为零件热负荷的进一步分析和结构优化提供依据.