Surface Temperature and Wall Heat Flux in a Spark-Ignition Engine Under Knocking and Non-Knocking Conditions

An experimental study was conducted to measure the instantaneous surface temperature and the wall heat flux from the gas to the combustion chamber in a spark-ignition engine under knocking and non-knocking conditions. The local instantaneous surface temperature and wall heat flux on the combustion chamber were measured at five positions, each at a different distance from the ignition plug, including three positions in the near knock zone, for various knock intensities. Relationships between the local heat transfer and the knock intensity were obtained. It was found that the instantaneous surface temperature and the heat flux rise rapidly at a crank angle when the knock is observed in the indicator diagram. For a knock intensity larger than 0.3 MPa, the maximum and the time-averaged heat flux, and the heat transfer coefficient increase with the knock intensity. In the near knock zone, these are strongly affected by the occurrence of the knock.