A New Analysis Method for Accurate Accounting of IC Engine Pumping Work and Indicated Work 2004-01-1262
In order to improve fuel economy, engine manufacturers are investigating various technologies that reduce pumping work in spark ignition engines. Current cylinder pressure analysis methods do not allow valid comparison of pumping work reduction strategies. Existing methods neglect valve timing effects which occur during the expansion and compression strokes, but are actually part of the gas exchange process. These additional pumping work contributions become more significant when evaluating non-standard valve timing concepts.
This paper outlines a new analysis method for calculating the pumping work and indicated work of a 4-stroke internal combustion engine. Corrections to PMEP and IMEP are introduced which allow the valid comparison of pumping work and indicated efficiency between engines with different pumping work reduction strategies. Several example data sets are presented which illustrate the method and the necessity for the corrections when analyzing engines with non-standard valve timings.
The upper limit potential improvement in BSFC available from PMEP reduction is presented and compared to the actual benefit obtained with three pumping work reduction strategies: 1) variable valve timing, 2) intake charge dilution (stratified lean operation) and 3) cylinder deactivation.