THE EFFECT OF ADDING HYDROGEN ON THE PERFORMANCE AND THE CYCLIC VARIABILITY OF A SPARK IGNITION ENGINE POWERED BY NATURAL GAS

This paper deals with the influence of blending hydrogen (from 0 to 50% vol.) on the parameters and the cyclic variability of a Lombardini LGW702 combustion engine powered by natural gas. The experimental measurements were carried out at various air excess ratios and at various angles of spark advance, at an operating speed of 1500 min−1. An analysis of the combustion pressure showed that as the proportion of hydrogen in the mixture increases, the maximum pressure value also increases. However, at the same time the cyclic variability decreases. Both the ignition-delay period and the period of combustion of the mixture become shorter, which requires optimization of the spark advance angle for various proportions of hydrogen in the fuel. The increasing proportion of hydrogen extends the flammability limit to the area of lean-burn mixtures and, at the same time, the coefficient of cyclic variability of the mean indicated pressure decreases.