EXPERIMENTAL STUDY ON DIRECT INJECTION OF PROPANE AND HYDROGEN IN A SI ENGINE WITH A MECHANICAL INJECTOR

In this study, a single-cylinder, air-cooled, four-stroke, spark-ignition internal combustion engine was modified to operate with both gaseous propane and hydrogen fuels. The cylinder head was redesigned, and a mechanically actuated hydrogen injector was integrated into the system. Various measurement instruments were installed on the test engine to record critical operational parameters for comparative analysis. To ensure safe fuel injection process, the necessary safety mechanisms were implemented. Initially, the engine was tested with propane under throttle positions ranging from 20 to 90 (in increments of 10) and speeds between 1000 and 4300 rpm, recording values for torque, net mechanical output, fuel consumption per unit output, engine thermal efficiency, and engine volumetric efficiency. The same parameters were subsequently measured while operating with gaseous hydrogen. Optimal performance for propane was observed at throttle openings of 80 and 90, within the speed range of 1600 1850 rpm, while hydrogen exhibited the most favorable results at 30 throttle opening and speeds between 1300 and 1775 rpm. When the performance of both fuels was compared, it was found that hydrogen operation resulted in a 27.8% reduction in mechanical output and a 62.2% decrease in engine torque. This decline is attributed to hydrogens lower volumetric energy density, which, under identical pressure and temperature conditions (1 bar, 20 C), is approximately 2,850 kcal/m, whereas propanes lower heating value is 22,800 kcal/m. Propane was supplied to the engine at a regulated pressure of 1.5 bar. Throughout the experimental procedures, common challenges associated with hydrogen manifold fuel injection, such as knocking, pre-ignition, and backfire, were not observed. This study presents an innovative approach, as no previous research has employed a mechanically actuated hydrogen injector synchronized with the intake valve for direct hydrogen injection into the combustion chamber.