Cycle analysis for fuel-inducted internal combustion engine configurations

Abstract

A quasi-one-dimensional computer code based on a fuel-air cycle analysis was developed to predict the performance of two- and four-stroke fuel-inducted engines. The analysis was developed to provide boundary conditions for a finite element analysis to predict thermal and mechanical loading of carbon-carbon pistons for use in advanced internal combustion engine concepts. The computer code can predict the required boundary conditions, which are gas pressure and temperature and heat transfer coefficients as a function of crank angle, along with engine indicated and brake power output, thermal efficiency and mean effective pressure. The code utilizes a variable specific heat calculation throughout the cycle. The compression of an air-fuel-residual gas mixture is calculated followed by a finite rate burn, where the burn duration is calculated on the basis of the turbulent flame speed and cylinder geometry. The residual gas content is calculated by an iterative technique. During combustion and expansion, ten equilibrium combustion product constituents are tracked. Engine friction, instantaneous heat transfer and blowby past the rings are calculated on the basis of empirical correlations. The tendency for engine knock or autoignition of the fuel is also calculated. Good agreement is obtained when compared with actual engine operation for power output, thermal efficiency and exhaust gas temperature.