To obtain a more reasonable model of torch combustion in a spark ignition engine with a vertical or horizontal prechamber, the instantaneous temperatures of combustion gas are measured by an infrared absorption-emission pyrometer with a narrow band pass filter for CO2 gas, while changing the torch nozzle area and air-fuel ratio.
The gas temperature diagrams indicate that the ignition timing, flame propagation and combustion duration in the main chamber with vertical prechamber differ entirely from those with horizontal one. The fact is verified by comparing them with the heat release rates obtained from the pressure diagrams and with the flame propagation taken by means of high-speed photography. The measured gas temperature diagrams are, therefore, found to provide a lot of useful and local information concerning the combustion process and the engine performance in the prechamber engines.
In addition, the infrared pyrometer employed with a filter of 4.3 µm can determine the values of absorptivity over a wide range of crank angle during the combustion stroke. Therefore, it can be also used as a monochromatic radiation pyrometer to measure the gas temperature in a practical engine with only a single optical window.