A novel two-zone thermodynamic model for spark-ignition engines based on an idealized thermodynamic process

The thermodynamic model is a valuable simulation tool for developing combustion engines. The most widely applied thermodynamic models of spark-ignition engines are the single-zone model and the two-zone model. Compared to the single-zone model, the two-zone model offers more detailed in-cylinder thermodynamic conditions, but its governing equations are numerically stiffer, therefore it is restricted when applied in computationally intensive scenarios. To reduce the two-zone model s stiffness, this paper isolates an idealized thermodynamic process in the unburned zone and describes this idealized thermodynamic process by an algebraic equation. Assisted with this idealized thermodynamic process, this paper builds a novel two-zone model for spark-ignition engines, whose governing equations are simplified to a set of two ordinary differential equations accompanied by a set of three algebraic equations. Benchmarked against the single-zone model and conventional two-zone model, the novel two-zone model is formed and validated by experimental results, and its stiffness is quantitatively evaluated by linearizing its governing equations at simulation steps. The results show that the novel two-zone model inherits the conventional two-zone model s ability to estimate both zones state variables highly accurately while its simplified structure reduces its stiffness down to the level of the single-zone model, accelerating the computation speed.