1991-02-01

Improving the Cold Start Combustion in Methanol Fuelled Spark Ignition Engines by Means of Prompt EGR 910377

A methanol fuelled single cylinder research engine was tested under simulated cold start conditions of 0°C. The engine instrumentation provided dynamic measurements of pressures and temperatures in the cylinder, inlet port, and exhaust port. Initially, tests were conducted to gain a better understanding of the metabolism of methanol cold starting under limit conditions. Following these tests the exhaust charged cycle (ECC), a form of prompt exhaust gas recirculation, was employed as a means of improving in-cylinder mixture formation during starting.
Tests using a special camshaft to obtain prompt EGR showed that successful starts using neat methanol could be achieved if ignition occurred during cranking. Thus, unlike the standard engine configuration, the ignition and starting limits with the prompt EGR system were essentially the same. Prompt EGR typically gave higher and earlier peak cylinder pressures and produced heat release rates which were unusually rapid for cold start conditions. As well the modified system was found to be much more tolerant of the post-start and run-up fuelling calibration strategy than the standard system, making it easier to achieve idle speed without stalling.

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