Analysis of the effects of wall temperature swing on reciprocating internal combustion engine processes

Abstract

A thermal wall temperature-swing (TWTS) model was built to capture the transient effects of various material properties and coating layers on the intra-cycle wall temperature of an internal combustion engine. This model was used with a thermodynamic engine simulation to predict and analyze the effects of different types of in-cylinder insulation on engine performance. Coatings that allow the surface temperature to swing in response to the gas' cyclical heat flux enable approximately 1/3 of the energy that was prevented from leaving the gas during expansion to be recovered while improving volumetric efficiency (VE). Reductions in compression work due to better VE and less heat transfer from the walls to the gas accounted for half of the improvements, while additional work extraction during combustion and expansion accounted for the other half. As load increases, the temperature swing and benefits derived from it also increase. NSFC improvements of 0.5 to 1% were seen with a highly swinging coating in the throttled regime for a realistic engine geometry and coating area, up to 2.5% at high loads.

Assessing the capability of conventional in-cylinder insulation materials in achieving temperature swing engine performance benefits

“…Calibration of these convection coefficients was performed utilizing measurements in the literature [25][26][27][28] in addition to unique measurements taken through similar means in the experimental study. More details on this model are in prior publications by Andruskiewicz et al 1…”

“…There has been considerable recent activity to minimize heat losses and improve engine performance through in-cylinder insulation. [1][2][3][4][5][6] Historically, many authors have attempted to use incylinder insulation for engine performance benefits. Some of the pioneering works were performed by TACOM for military vehicles, emphasizing the elimination of the engine cooling system, and the tactical benefits provided by improved efficiency.…”

“…Ideal insulating thickness for reciprocating internal combustion engines is generally about 25% of the depth 1% due to the locations of maximum and minimum heat flux throughout the cycle, and the temperature waves through the coating that are established. This parameter is critical for properly designing coatings for effective temperature swing insulation, as demonstrated by Andruskiewicz et al 1 DT;…”

“…In general, the surface temperature swing will be related to the material properties through the relation proposed by Assanis and Badillo 20 in equation (1). The volumetric heat capacity ''r 3 c'' of a bulk material is a function of the composition (mass heat capacity-''c'') and density of the bulk material ''r.''…”

Experimental investigation of the relationship between thermal barrier coating structured porosity and homogeneous charge compression ignition engine combustion

“…To accomplish the desired effect, the coating needs to both be thin and have a low thermal mass, thereby enabling the coating temperature to more closely mirror the gas temperature throughout the cycle. [24][25][26][27][28] The effect of this type of coating can be seen in Figure 3 as the plot for ''Temperature Swing Insulation'' which has a much larger temperature swing than the ''Traditional Insulation,'' of the old adiabatic concept. The gas temperature increase caused by compression and combustion leads to a rapid increase in the coating surface temperature, yielding a temperature ''swing,'' reducing heat transfer by limiting the gas-wall temperature differential.…”