NUMERICAL COMPUTATION OF UNSTEADY GAS FLOW IN THE DUCTS OF RECIPROCATING ENGINES

Abstract

This article describes the numerical computation of unsteady compressible flow in the ducts of reciprocating engines, employing a total variation diminishing (TVD) scheme. A simplified version of TVD using an explicit upwind algorithm to solve the nonhomentropic gasdynamics in pipes was programmed into an engine cycle simulation package. The scheme was verified to diminish nonphysical oscillatory solution caused by sudden property changes in two extreme cases: one is the ‘De Holler’ problem; the other is a shock tube test. In order to evaluate the accuracy of this scheme to engine pipe flow calculations, an experiment on a single-cylinder research engine was carried out using a nonintrusive method, namely, laser Doppler velocimetry, to measure the instantaneous velocity in the intake and exhaust ducts. The velocity and the associated pressure-crank angle history at a specific location in the ducts have been examined by comparison of simulation and experimental results. It proves that the simplified TVD scheme is an accurate, efficient, and robust method in engine pipe flow calculations and may provide a useful tool for engine performance prediction.

Notes

Completion of this work was supported by the National Science Council under Contract No. NSC 83-0401-E007-091.

Address correspondence to Dr. Che-Wun Hong, Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30043, Taiwan. E-mail: [email protected]