摘要
缸套承受不均匀的热负荷而产生的失圆变形,主要影响缸套与活塞组件间的密封、摩擦/磨损以及排放性能。控制缸套的变形与失圆,对降低机油耗,改善摩擦性能以及降低排放,具有重要的意义。该文应用流固耦合传热方法,建立了缸盖-冷却液-缸套-缸体耦合传热模型,在对冷却液流动特性以及缸套、缸盖关键点温度测试的基础上,研究了缸套的稳态传热温度场分布以及热态变形规律。研究表明:受各缸冷却水套流动与热负荷不均匀的影响,各缸缸套温度场分布不均匀,从缸套顶部到底部温度逐渐降低,相邻两缸间的缸套顶部温度高于其他部位,最高温度出现在3、4缸间的缸套顶部;各缸缸套综合热变形是不均匀的,1、4缸自由端综合热变形较大,最大综合膨胀变形位于第4缸90°位置(飞轮方向),最大综合收缩变形位于第1缸90°位置(1、2缸间);缸套不同截面径向变形呈现与综合变形不同的变化趋势,缸套中部与冷却液接触,主要呈现膨胀变形,上部与下部受缸体结构约束,膨胀变形较小;各缸呈现不均匀的"豌豆"形径向变形,其中2、3缸对称,1、4缸对称;缸套主推力面与次推力面径向变形量相对较小,各缸的变形差异也较小。
Deformation of the cylinder liners, which was caused by inhomogeneous mechanical and thermal loads, mainly affects the performances of sealing, lubrication and wearing between piston assembly, and the cylinder liners and emission performance. It is significantly important for reducing oil consumption, oil emissions, and improving friction properties to control cylinder liner deformation and out-of-roundness. The characteristics of deformation caused by mechanical load was researched in the author’s previous work. Therefore, there is a need to find out the distortion of liner caused by thermal load. In the present study, a coupled heat transfer model of the cylinder heads, the cooling water jacket, the cylinder liners, and the engine body of four cylinders, in-line, water cooling, turbocharged inter-cooled diesel engine was established by using the fluid-solid coupling heat transfer method. In this model, the external boundary conditions, which are difficult to determine on the fluid and solid contact faces, were translated into internal boundary conditions. The heat transfer in the solid and fluid was coupled by coupling the surfaces of the solid and fluid. Thus, the expected results of temperature distribution and coolant flow can be computed. The flow characteristics of coolant and the key point temperatures of the cylinder liners and cylinder heads were tested to correct the boundary conditions of flow and heat transfer. On the basis of correctional boundary conditions of heat transfer, the flow characteristics in the water jacket and heat transfer in the cylinder liners and cylinder heads were analyzed. Then, the steady-state heat transfer temperature distribution and the characteristics of thermal deformation of the cylinder liners were obtained. The results indicate that the coolant flow and cooling are uneven due to the difference of water jackets for each cylinder. The flow velocity is gradually reduced from the first to the fourth cylinder, and the temperature is gradually increased. The temperature of the exhaust side is higher than that of the intake side. The temperature distribution of each cylinder liner is uneven because of inhomogeneous coolant flow and thermal load. The temperature of the top of the cylinder liners, which is located between two adjacent cylinders, is higher than the other parts of cylinder liner （the highest temperature is 195℃, which is located at the top of the third and fourth cylinder liners）. Temperature gradually decreases from the top to the bottom of the cylinder liners. The temperature at the top of the liners, which has contact with the bodies, is high, and the temperature gradient is large. The temperature gradient decreases in the middle area of the liners surrounded by coolant. The temperature and gradient at the bottom area of the liners for each cylinder liner, which is located under the bottom dead center of the pistons, are similar. The synthetic thermal deformation of each cylinder liner is not uniform;deformations of the first and the fourth cylinder liner are larger. The maximum expansion of hot deformation is 0.216mm and located at 90＆#176; of the fourth cylinder on the flywheel end. The largest shrinkage deformation is -0.131mm and located in between the first and second cylinder. The trend of deformation at the radial section of the liners is different from the trend of synthetic deformation. The middle area of the liners, surrounded by coolant, mainly presents expansion deformation. Expansion deformation of the top and bottom of each liner, constrained by the body, is smaller. Each cylinder shows inhomogeneous radial deformation, which is just like the shape of a pea, and there is a symmetry between the second and the third cylinders, and between the first and the fourth cylinders respectively. Deformation of main and minor thrust face for each cylinder liner is relatively less, and the difference of deformation of each liner is also smaller.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2014年第7期34-41,F0003,共9页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(51366006)
科技人员服务企业行动项目(2009GJF30001)
人才培养基金项目(2008PY014)资助
关键词
柴油机
气缸
变形
流固耦合
温度分布
diesel engines
cylinders
deformations
fluid-solid coupling
temperature distribution
