Evaluation of wall heat flux calculation methods for CFD simulations of an internal combustion engine under both motored and HCCI operation

Abstract

In the present work, a study of different numerical heat transfer models is presented used for Homogeneous Charge Compression Ignition (HCCI) internal combustion engine simulations. Since the heat loss through the walls of an engine is an important parameter during engine optimization, as it influences power, efficiency and emissions, accurate modeling techniques need to be available. In this work, the predictive capability of different Computational Fluid Dynamics (CFD) models has been assessed, by using data obtained from experiments on a Cooperative Fuel Research (CFR) engine, a simple single cylinder pancake engine, which has been probed with local heat flux sensors into the combustion chamber walls. The open-source software OpenFOAM R was used to perform simulations of this engine, under both motored and HCCI operation, with a specific focus on the performance of different heat flux models. Due to the simple engine geometry, more numerically demanding heat flux modeling methods could be used, maintaining an acceptable computation time. This allowed a full comparison between the equilibrium wall models as in standard use, an improved empirical heat flux correlation and a numerically intensive low Reynolds formulation. The numerical results considering all aspects of the heat flux-both its progress in time as well as quantitative aspects such as the peak heat flux or the total heat loss-have then been compared to an extensive experimental database. This allowed a full analysis of the performance of the different methods. It was found that the low Reynolds formulation described the physical behavior near the wall the best, while predicting acceptable results concerning the heat flux through the engine walls. The best heat flux prediction was however obtained with an improved empirical model, which additionally has a much shorter computation time. This is crucial when moving on to heat flux simulations of more complex production-type engines. Lastly, the equilibrium models were never capable of accurately predicting the wall heat flux.

Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry

“…The implementation of detailed models for radiative heat transfer is considered in [29,30]. The combination of combustion in the fluid domain and conjugate heat transfer in the solid domain was pursued, e.g., by the authors of [31][32][33].…”

“near wall” combustion model of spark ignition engine

“…Another important aspect of SI combustion is the post-flame oxidation of CO and HC when the flame front reaches the vicinity of the combustion chamber wall [2,3]. In the combustion model of SI engines in recent years, the decrease in the rate of heat release at the end of combustion is entirely attributed to a special phenomenon, resulted from the interaction between the flame and the wall is the cause of the decrease [4][5][6]. In this work, in the context of 0-D physical modeling, the following method employs a simpler physical description to reproduce the complex dynamics of the post-flame reaction.…”

Development of praxeological principles to model/study heat generation and heat consumption processes in the engine of rapid internal combustion

“…Increasingly common is the so-called HCCI-technology for the organization of a working cycle. The phenomenon of combustion in the gasoline engine of direct injection and in HCCI-engine has become an object or subject of thorough studied relatively recently [6,7], which is why the phenomenon of heat transfer through the walls of cylinder in such engines has been paid very little attention. And if one is to rely on the research methods that directly combine experiment and calculation, the difference between these engines in the methodological sense of elucidating the features of heat transfer is blurred.…”