Scavenging

Scavenging

Port, Valve, Intake, and Exhaust System Design

Published in John B. Heywood, Eran Sher, The Two-Stroke Cycle Engine, 2017

Poppet valves are widely used in large-bore diesel engines and also in some recent designs of medium-sized gasoline two-stroke engines. In large-bore engines, a uniflow scavenging system is commonly employed. Scavenging is usually performed from the bottom of the cylinder to the top, where the scavenging ports are controlled by the piston and the exhaust flow by one or more poppet valves (e.g., Fig. 1-7). When poppet valves have been used in medium-sized two-stroke engines instead of exhaust and scavenging ports, it is to retain the standard wet crankcase and oil sump systems and the valve train of conventional four-stroke cycle engines (see Fig. 1-26). These valved two-stroke engines then use an external compressor (often a roots blower) to compress the scavenging air.

Numerical analysis of modified crossbreed engine cycle under BS VI norms

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Journal Information

Published in International Journal of Ambient Energy, 2022

P. V. Elumalai, M. Parathasarathy, S. Sathishkumar, M. Murugan, A. Saravanan, M. Sreenivasa Reddy, Keerty Venkata Sri Ramachandra Murthy

The CFD analysis in Figure 21 shows the fluid flow trajectories during the effective exhaust condition. In this condition, the fresh air from the intake valves pushes out flue gases effectively from the cylinder. The flow of the fresh air from the intake ports acts as a jet projection to make a swirl flow inside the cylinder. This improves the efficiency of the exhaust scavenging process.

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Port, Valve, Intake, and Exhaust System Design

Numerical analysis of modified crossbreed engine cycle under BS VI norms