In order to solve cylinder-scraping of a four-cylinder high speed diesel engine, based on the measurement of piston temperature, the piston temperature field was numerically simulated by using temperature fitting method, the calculation results were well consistent with the measured temperature. By finite element analysis of piston thermal load based on the calculation results as temperature load, enlarging oil cooling cavity in the piston head was proposed to enhance cooling locally, which could effectively reduce temperature of the piston head and the first ring groove and avoid the occurrence of cylinder-scraping.

The micro-emulsified ethanol-diesel blended fuel is an ideal alternative oxygenous fuel for diesel engines due to its physical and chemical properties and excellent combustion characteristics. Fueled with this fuel, a diesel engine can give off remarkably lower harmful emissions,especially particulate. It is necessary to take into account instantaneous variations of the thermophysical parameters of blended fuels with temperature and pressure. For these reasons, this paper use the empirical formulas calculates the thermophysical parameters of this blended fuel，including the specific heat capacity, viscosity, thermal conductivity and diffusion coefficient. And the effects of the temperature, pressure and ethanol content on the initial blended fuel’s condition are investigated. The results show that the addition of some ethanol to the diesel oil can contribute to the evaporation of the micro-emulsified ethanol-diesel blended fuel, and these empirical formulas are able to be employed to calculate the thermophysical parameters of this blended fuel.