PUMPING FRICTION


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PUMPING FRICTION
PUMPING FRICTIONPumping air into the engine during the intake process, and burned gases out during the exhaust process, during the gas exchange process (in the four-stroke engine cycle), requires a work transfer between the in-cylinder gases and the piston. Several flow restrictions outside the cylinder head, in the inlet and exhaust systems—air filter, ducting, throttle, intake manifold (on the inlet side), exhaust manifold and tail pipe, catalytic converter, and muffler (on the exhaust side)—cause pressure drops which require work to overcome. Equally important are pressure losses in the inlet and exhaust ports and valves. As load is reduced in a spark-ignition engine, the airflow is reduced by partly closing the throttle increasing its flow restriction. The increase in throttling work is more r…
Citation
John B. Heywood: Internal Combustion Engine Fundamentals, Second Edition. PUMPING FRICTION, Chapter (McGraw-Hill Professional, 2018), AccessEngineering Export