Journal Article
Measurement and Characterization of Flow Resistance of Critical and Near Critical Pulsating Flow through an Orifice Located in the Exhaust Stream of a Diesel Engine
2019-04-02
2019-01-1176
The quasi-steady assumption is often used to determine the flow resistance of highly compressible critical or near-critical (approaching sonic velocity) pulsating flows through engine valves, EGR system and other flow restrictions for modeling and control. The quasi-steady assumption utilizes steady (non-pulsating) flow results where the discharge coefficient (Cd) of flow nozzles/orifices is solely a function of Reynolds number (Re), and Cd is constant at high Re. There exists some literature addressing the flow resistance of incompressible pulsating flows and also for compressible steady flow, but virtually no literature for the highly compressible, critical/near-critical pulsating flow typical in engines. In this work, the Cd of a square edged orifice placed in the exhaust stream of a four-cylinder diesel engine was measured and found not to be a sole function of Re, but correlated to Re.
