Research And Development Of Piston Thermal Fatigue Simulation Test Bench

With the continuous development of the internal combustion engine to the high-speed, high power, low fuel consumption, low emissions and high strengthen direction, the reliability and the service life of the engine and its major components has been put into severe test. Specifically, with the increase of heat load, some heated parts which make up the combustion chamber, such as piston, cylinder head and cylinder sleeve, will easily be damaged because of thermal fatigue. Therefore, a thermal fatigue simulation test bed for piston was designed independently, and it retained highly effective and automatic. This test bed can not only provide evaluation methods for piston reliability and durability design of high strengthen engine, but also can provide a reliable testing platform for basic theory, testing standards and regulation of piston thermal fatigue research.After researching and investigating the existing piston thermal fatigue simulation test bed at home and abroad, and with the consideration of the actual situation and the existing condition, mechanical platform, heating system, cooling system, temperature detection system, control system and security alarm system were designed.Two pistons can be tested on the test bed at the same time. By setting the maximum heating temperature value and minimum cooling temperature value of piston in advance, piston temperature can varied alternately between the highest and lowest temperature. In this way, thermal load of piston under the practical operating condition can be simulated. During the testing, the pistons are rotated to change its heating or cooling status driven by swing cylinder, and was turned over to change its direction of top and cavity by swing cylinder. The pistons are heated by burning compressed natural gas combustion to simulate its thermal load under actual operating conditions. The pistons cavity is cooled by the water cooling system and the top is cooled by air cooling system. The piston temperature is detected by K thermocouple. The upper computer and lower computer are combined to control the test bed and provide the temperature control mode. The core of upper computer is PC computer, and PC program is written by LabVIEW software; the core of lower computer is programmable logic controller PLC, and PLC program is written by GX Developer V8software. After testing, the following step is to check surface crack of pistons top. The pistons are qualified if there is no macroscopic crack or microcosmic crack. In the meanwhile, the test bed provides perfect security alarm system. The test bed structure is simple and high reliability, and its working performance is stable and testing process is visualized. The test bed is highly automatic, economical and operable, and it is equipped with good man-machine interface of exchange and environmental, effective heating pattern. The cooling water system is recycling and resource conservation.As long as the test bed is improved properly, it also can be used to study thermal fatigue damage for heated parts, such as the cylinder head, cylinder sleeve, which indicates its versatility.At last, debugging trails were conducted on the test bed and its main system. The result shows that mechanical platform, heating system, cooling system and temperature detection system of the test bed can operate normally and properly, and the test bed meets the predetermined target.