Development of quasi-dimensional turbulence model for spark-ignition engine with physical analysis of tumble: Energy-based tumble model focusing on energy intake and turbulence production

摘要

Tumble plays a crucial role in a spark-ignition engine for generating turbulence that affects various in-cylinder properties, such as flame-propagation speed, flame geometry, and heat transfer. Therefore, much research related to tumble motion has been conducted to increase the thermal efficiency of a spark-ignition engine. Despite the importance of the flow motion affecting the overall properties of the engine, quasi-dimensional turbulence models that consider tumble motion have only recently been developed owing to the complexities of irregular flow shapes. This paper introduces a turbulence model that applies tumble features. Unlike previous tumble models that address tumble from the perspective of angular momentum, we propose a new energy-based tumble model. Throughout the model, kinetic energy is divided into rotational energy, which is regarded as the energy of tumble motion, and nonrotational energy. The development of the new model is primarily focused on the intake kinetic energies from both energy forms and turbulence production from rotational energy; these have a dominant effect on the turbulence during combustion. The model captures the differences in flow properties that were not distinguished in previous studies. Furthermore, since the model reflects the actual flow characteristics, it provides the understanding of energy phenomena of tumble which has not been attempted before. This paper presents the overall application of the turbulence model in the simulation along with the proposed tumble model.