Practical Considerations in the Airflow Optimization of a Single Cylinder Diesel Engine

The present work is concerned with the design of an optimum air intake system for a single cylinder reciprocating diesel engine. It is a well known fact that air flow rates of a naturally aspirated engine are sensitive to the geometrical dimensions of the pipes that connect the engine to the atmosphere. Hence, tuning intake system dimensions for optimum airflow rates is of great importance. In this scenario simulation tools can be useful for the optimization of intake system. The one dimensional simulation tool AVL BOOST is used to predict air flow rates with different combinations of connecting hose diameters and lengths. Subsequently air flow rates are measured with selected clean hoses on an engine steady state test bench. It is found in the initial tests that the lengths and diameters of optimum hoses deviate from the AVL BOOST predicted optimum geometric dimensions. Analysis of test data and measurement systems is done to find out the possible reasons for mis-match between the predictions and measurements in order to improve the airflow rates on actual engine. Findings of the analysis are presented in the paper. At the junction of the clean hose and air filter; clean hose and engine intake pipe sudden contractions and expansions in the air flow path are observed. The pressure losses associated with these junction points are different than those considered in the AVL BOOST predictions and this results in the lower air flow rates. The interplay between flow dynamics at these junction points and the air flow rates is explained. In the subsequent test trials, tapered pipes are used to merge the air filter and clean hose; clean hose and engine intake pipe.