The Effects of Squish Motion on the Burn-Rate and Performance of a Spark-Ignition Engine

An experimental investigation of the effects of squish motion on turbulence generation, burn-rate and engine performance has been undertaken in a Ricardo Hydra single-cylinder research engine. An experimental combustion chamber design incorporating a number of squish generated jets was used to enhance the turbulent motion in the chamber during combustion. Flow-field measurements were made with a hot-wire anemometer in order to characterize the turbulence field. Measurements of brake thermal efficiency and mass burn-rate showed that enhanced turbulence generated by combustion chamber geometry is effective in improving performance under lean operating conditions. A single squish generated jet motion directed towards the spark plug resulted in the highest thermal efficiency during high speed lean operation, while burn-rate analysis indicated that squish action was most effective during the main burn period.