Optical and thermal radiating characteristics of heat- insulated walls and elements of the high-speed diesel combustion chamber

Abstract

The main objective of this research is the analysis of influence of optical and thermo radiating characteristics on the transient (steady state) temperature distributions inside the heat-insulating semitransparent (SHIC) и opaque (HIC) coatings for thermal regulation and control of walls and elements of the combustion chamber (СС) high speed diesel engines. Developed author's methodology of physical and mathematical simulation of parameters of the radiant and heat conductivity transfer was used to calculate optimal balance of optical and thermo radiating characteristics of coatings - as selectively absorbing and scattering materials with different transmittance, reflection and emittance depending on wavelength diapasons of irradiating or radiating heat fluxes. The paper presents a mathematical simulation of optimal balance of improved optical (transmittance, reflectance, absorption coefficients or absorption, scattering indexes) and thermo radiating (emittance coefficient) characteristics. It is considered the effect of the subsurface volumetric heating which at their display promotes decreasing of a surface overheating of coatings of the combustion chamber. It have been received by the numerical method temperature distributions for semitransparent heat-insulating coatings protecting metal substrate (CC wall) with different reflection of penetrating radiation by SHIC layer. It has been shown decreasing the surface temperature of SHIC in comparison with temperature of opaque HIC. The methods of improvement of thermal isolation of the combustion chamber with use heat-insulating coatings c are offered: 1) high volume reflection rλ > 60-80 % for thermal protection (barrier) against intensive radiation of red-hot soot particles of soot (λ ~ 0.7-2 μm) and 2) high surface emittance ελ > 80-90 % (λ >4- 5 μm) for counteraction convectional heat flux inside CС a diesel engine.