Experimental and numerical investigation of large-bore engines port discharge coefficients

Abstract

This paper describes experimental and numerical investigations of the discharge coefficients from the ports in large-bore two-stroke cycle engines. The literature includes some information on the discharge coefficients from very small ports. The literature was found not to include data collected from very large ports, such as in Cooper, Clark, and Worthington two-stroke cycle engines. The methodology used was to conduct experimental tests and numerical simulations. In the experiments, a flow bench was designed to determine experimentally the discharge coefficients of three primary large-bore engine ports. The obtained data show that there is a considerable difference between the discharge coefficients of the three primary engines used in the natural gas industry. Furthermore, the data substantially differ from the thin-walled discharge coefficient data of the small-port engines reported in the literature. The numerical model was employed to study the effects of the pressure ratio across the Worthington engine intake ports and port open fraction on the discharge coefficients. As a result, a mathematical model was developed for the discharge coefficients as a function of port geometry, port open fraction, and pressure ratio. Hence the data and model provided in this paper can be used by designers to match turbochargers and aftercoolers better to large-bore engines.