Abstract
A quasi-one dimensional engine cycle simulation program was developed to predict the transient heat flux during combustion in a spark ignition engine. A two-zone heat release model was utilized to model the combustion process inside the combustion chamber. The fuel, air and burned gas properties throughout the engine cycle were calculated using variable specific heats. The transient heat flux inside the combustion chamber due to the change in the in-cylinder gas temperature and pressure during combustion was determined using the Woschni heat transfer model. The program was written in MATLAB together with the Graphical User Interface (GUI). Numerical results were compared with the experimental measurements and good agreement was obtained. Four thermocouples were used and positioned equi-spaced at 5mm intervals along a ray from the spark plug location on the engine head. These thermocouples were able to capture the heat flux release by the burned gas to the wall during the combustion process including the cycle-to-cycle variations. Pressure sensor was installed at the engine head to capture the pressure change throughout the cycle.
Highlights
Heat transfer between the working fluid and the combustion chamber in the internal combustion engine is one of the most important parameters for cycle simulation and analysis
The thermodynamic properties that used in this model were put in empirical function, where x value represents the mass fraction of the burnt cylinder content
The temperature history that obtained from the simulation was used in equation (2) and (3) in order to determine the heat flux of unburned and burned gas regions
Summary
Heat transfer between the working fluid and the combustion chamber in the internal combustion engine is one of the most important parameters for cycle simulation and analysis. The heat fluxes for both burned and unburned gases were expressed as functions of temperatures as follows: Qɺ b = hAb (Tb − Tw ) The combustion gases are defined into two zones which are unburned gas zone and burned gas zone where Qɺ b and Qɺ u are the heat transfer rates for the Equation (4) and (5) are empirical functions that have the correct limits in the case of a cylinder where x → 0 and when x →1 .
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