Knock Limits and Performance of Some Gaseous Fuels in a Supercharged Spark-Ignition Engine

Abstract

Observations of knock limits, in terms of ignition time for borderline knock, are presented for methane and propane at a range of supercharge conditions up to 9 ***lbf/in²boost, in a spark-ignition engine of 105 mm bore running at speeds of 600 and 920 rev/min, with compression ratios of 7·7/1 and 9·5/1. Associated measurements of output and economy are given. Less extensive observations on a butane fuel, and on methane-propane and propane-butane mixtures, are also included.

From an examination of computed temperature-pressure histories in the unburned portion of the mixture, it is found that the knock limited ignition advance on the propane fuel at chemically-correct mixture can be closely predicted over the full range of operating conditions covered, by the attainment of a certain critical value of a simple parameter.