Analysis of Pressure Pulsations in the Intake Duct of a Single Cylinder Diesel Engine

The inlet air flow rates of a naturally aspirated engine can be enhanced by proper synchronization of the pressure fluctuations to obtain maximum air flow rate. Single cylinder diesel engine is considered as a test case for this study. 1-D simulation software AVL-BOOST is used for predicting the air flow rates in intake duct. Using this validated simulation model, theoretical correlations from wave theories are used to explain the arrival of pressure pulses at the intake valve. The pressure pulsations at the port for different lengths of the intake duct are analyzed. It is found that, a weighted combination of one or more effects results in a peak in volumetric efficiency and it cannot always be determined from a single correlation. The effects of diameter of the intake duct on the air flow rates are also studied. The air flow rates for each crank angle are calculated based on gas dynamic relations and these numerical calculations are validated against the simulation model. The calculations are then extended, to analyze the choking effects based on a non-dimensional number. Its predominance during the early stage of intake is identified and it increased with decreasing diameter of intake duct.