F2008-12-304
Multilayered Semitransparent and Opaque Heat-Insulating Coatings for the Engine Combustion Chamber
Control methods of temperature conditions for elements of the diesel combustion chamber with multilayered semitransparent and opaque heat-insulating coating are discussed. This invastigation is connected with unresolved problem of acting of thermal flux radiant component on the heat-insulating coating which can be semitransparent. The fraction of the radiant component in the total thermal flux reaches ~ 40-50%. It is shown that in the engine combustion chamber visible and infrared radiation can penetrate into multilayered heat-insulating ceramic coatings and heat them internally for necessary depth. Physical and mathematical models of radiant and conductivity heat exchange problems and a method of its decision for a multilayered scattering and absorbing coating are considered. The common decision of heat conductivity and radiation transfer equations is analyzed. Evaluation of a radiation field parameters is carried out by means of the mathematical moment method and definited by the decision of the differential equations system for moments of radiation intensity. For engineering practice in two-term approach of a moment method the accuracy of numerical calculation is not less 5% for receiving of integrated characteristics of radiation field. Spectral and temperature dependence of optical parameters is considered. The examples illustrating practical importance of the considered problem are studied. Transient radiative heat transfer analysis has performed for model semitransparent thin coatings. The thick layers of semitransparent materials present quasi adiabatic combustion chamber wall executed completely from ceramics. A mathematical modeling of temperature and radiant fields carry out for system of traditional opaque and new semitransparent (SHIC) heat-insulating coatings for operating conditions of high-speed diesel engines. The opportunity of formation of subsurface temperature maximum and positive gradient of temperature in SHIC is shown. This effect is depended by an optimum ratio of thermal physical parameters and also scattering, absorption indexes; scattering indicatrix. Influence of a thickness (co-ordinate) of single-layered or multilayered coatings is discussed. Computer program of this problem is presented in language C++ and could be used at the decision of a different problems of radiant and conductivity heat exchange in various operating condition of diesel engines
Poster presentation: Simulation and testing