Effect of Optical and Structural Parameters of Thermal Barrier Coatings of the Combustion Chamber on Working Processes of a Diesel

Abstract

The paper describes the bulk mean thermodynamic parameters of the combustion space in the diesel engine cylinder during the whole operating cycle adjusted consideration the features of heat transfer between the working fluid and the combustion chamber wall made of (or coated) thermal barrier materials using semitransparent ceramics. The novelty of this study is a simulation of convective and radiant heat exchange by the forming gas atmosphere and the generating soot microparticle cloud near heat insulated walls with a temperature regime determined by the significant influence of the optical parameters of thermal barrier materials or coatings. The total thermal radiant flux within the IR long and short wavelength range was modeled as a part of the convective-radiant heat flux. The temperature regime of insulation material (with a transparency band up to $\sim 3-4 \mu m$) was mainly determined by exposure of penetrating radiation component (~ 1-2 $\mu m)$ primarily from red-hot soot particles. For the first time, the model developed by the authors suggests the study of convective and radiant processes in different locations within the chamber due to the temperature regime of the exposed semitransparent thermal barrier coatings with subsurface (internal) radiant thermal source with the power which is independently determined by its microstructure and optical parameters. The proposed physical model based on the independent impact of the long and short wavelength components allowed the authors to modify the traditional semi-empirical approximation of by including (for example, in the Annand formula) the real value without any correlating constants. The remaining additive radiant part used for solving a nonlinear problem of radiant-conductive heat transfer within the wall with TBC to determine its specified surface temperature Tw for further iterative and cyclic calculations depending on the angular rotation rate of the engine crankshaft.