Evaluations of Combustion Parameters Using Engine Speed Fluctuation Measurements

The combustion process in an IC engine is of significant importance for its noise and vibration characteristics in the vehicle. Describing the combustion process with thermodynamic metrics typically demands extensive instrumentation of the engine to obtain the cylinder pressure from the combustion chamber. This time consuming task often requires, that the engine be removed from the vehicle, instrumented with pressure transducers, and then either reinstalled in the vehicle and tested or installed in a test cell and evaluated. This paper describes a new relatively simple approach towards examining important combustion parameters.

The technique is based on statistical analysis of the crankshaft's speed fluctuation. This approach requires relatively simple instrumentation of the engine and is therefore more applicable for vehicle level investigations. Several correlations between speed fluctuation and combustion parameters not found in current literature are described here in the form of a case study on an engine. The advantages and limitations of the technique are discussed and recommendations are advanced for future work.