Experimentally Determined Port Discharge Coefficients From Large-Bore Reciprocating Engines

Abstract

This paper describes the collection and analysis of discharge coefficients from the ports of large-bore two-stroke cycle engines. The literature includes some information on discharge coefficients from very small ports. The literature was found to not include data collected from very large ports, such is in Cooper, Clark, and Worthington two-stroke cycle engines. The methodology was to construct and then use a flow bench that was sized for large-bore engine cylinder liners. The flow bench is designed to experimentally determine the discharge coefficients of large bore engine ports. The discharge coefficients are an integral part of determining the air flow rate through an engine, and in modeling and predicting the airflow through an engine system. This information can be used by designers to better match turbochargers and aftercoolers to engines. Large bore engine cylinders are typically are 35–56 cm (14–22 in.) in diameter, and have power outputs ranging 745–3730 kW (1,000–6,000 hp). In general, the majority of these engines were built in the 1940–1950’s. The importance of predicting the airflow rate through these engines has become paramount due to increasingly stringent EPA emission regulations. The data shows that there is a vast difference between the discharge coefficients of the three primary engines used in the natural gas industry.