Study of the short-term cylinder wall temperature oscillations during transient operation of a turbocharged diesel engine with various insulation schemes

This work investigates the phenomenon of short-term temperature (cyclic) oscillations in the combustion chamber walls of a turbocharged diesel engine during transient operation after a ramp increase in load. For this purpose, an experimentally validated simulation code of the thermodynamic cycle of the engine during transient conditions is used. This takes into account the transient operation of the fuel pump and the development of friction torque using a detailed per degree crank angle submodel, while the equations for each cylinder are solved individually and sequentially. The thermodynamic model of the engine is appropriately coupled to a wall periodic heat conduction model, which uses the gas temperature variation as boundary condition throughout the engine cycle after being treated by Fourier analysis techniques. Various insulation schemes are examined (plasma spray zirconia, silicon nitride) for load-increase transient operation. The evolution of many variables during transients is depicted, such as amplitude of oscillation, depth where the swing dies out, or gradient of temperature swing. The investigation reveals many interesting aspects of transient engine heat transfer, regarding the influence that the engine wall material properties have on the values of cyclic temperature swings.