Parameter Study of Some Key Structures for Cylinder Head

Using the method of the parameter study, some important dimensions of the cylinder head of an internal-combustion engine are analyzed. Under the mechanical load, the variational rules of the von Mises maximum stress on cylinder head are obtained, which are influenced by the thickness of the floor plate, head plate, jobbing sheet, standing partition board, and side plate of inlet port and exhaust port. A hypothesis is verified that there is an ideal matching point among those above-mentioned main parameters. The quantificational proportion relations, between these key structural parameters and von Mises maximum stress of cylinder head, can provide a good help for the cylinder head's structural design.

Numerical simulation and optimization of the cylinder head water jacket based on the two-phase flow boiling heat transfer

Boiling heat transfer and the controllability of the thermal load of the cylinder head were studied.The thermodynamic phase change characteristics of the cylinder head coolant were considered and the mass,momentumand energy transfers between two phases were calculated with the interface transfer submodels by using the computational fluid dynamics software CFX. Results showed that compared with the single-phase flow without considering the boiling heat transfer,the sub-cooled boiling heat transfer of the cylinder head was greatly increased. According to the results of the numerical simulation,an optimized structure of the water jacket was proposed. Finally,temperature and velocity of coolant,diameter of flow passage and mean bubble diameter that influences sub-cooled boiling were studied using the orthogonal experiment method.

Influence of the cylinder head structure of a diesel engine on fatigue strength

Using finite element method,influence of diesel cylinder head structure on fatigue strength is investigated.A simplified head model with function characteristics is built for thermal-mechanical simulation.From the simulation results,the influence of valve bridge structure and roof transition fillet dimension on fatigue strength are obtained.And a new valve bridge structure which can effectively improve the fatigue life is proposed.

Thermo-Mechanical Analysis of the Sealing Performance of a Diesel-Engine Cylinder Gasket

Taking the combustor composite structure of a high-strength diesel engine as the main research object,dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation models.Using the measured cylinder gasket compression rebound curve,a gasket unit has been designed and manufactured.For this unit,the influence of the bolt pretension,cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling.The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure.The change of the body material has little effect on this pressure.The cylinder gasket seal pressure decreases progressively with the reduction of the elastic module of the cylinder head material.

加氢反应器的设计

加氢反应器高温、高压、临氢等特点使其在材料选用、结构等方面较为特殊,与常见的中低压容器有所不同,设计时应选用合理的材料、采用合理的结构才能确保其既能便于制造和检验,又能满足设备的使用要求,文章对加氢反应器的设计进行了简单的概述。

柱面内爆驱动下铅飞层对碰区动载行为的实验研究

采用光学阴影照相和脉冲X光照相,对柱面内爆对碰驱动下铅飞层对碰区凸起行为进行了实验研究。实验结果显示,铅飞层对碰区出现严重的射流状超前凸起,凸起行为表现出明显的失稳发展倾向。由于对碰产生高压,因此铅飞层对碰区可能完全熔化,变成名义上无剪切强度的流体。材料的低强度、低熔点(冲击熔化压力)性能是造成铅飞层对碰区出现射流状超前凸起现象的主要因素。还观察到对碰区出现3个超前凸起现象,初步分析可能是由于柱面滑移爆轰波对碰导致的波系反射、叠加造成的,具体原因还有待于进一步分析研究。