The constant-volume combustion fuel-air cycle model can be used to estimate the effect of changes in internal combustion engine design and operating variables on engine efficiency. The following table gives the major differences between a diesel and a spark-ignition engine both operating at half maximum power.
(a) Use the graphs of fuel-air cycle results (Figs. 5-9 and 5-10) to estimate the ratio of the diesel engine brake fuel conversion efficiency to the spark-ignition engine brake fuel conversion efficiency.
(b) Estimate what percentage of the higher diesel brake M conversion efficiency comes from:
(1) The higher diesel compression ratio
(2) The leaner diesel equivalence ratio
(3) The lack of intake throttling in the diesel compa~ed with the spark-ignition engine
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