Experimental study on performance and emissions characteristics of a spark ignition engine supplemented with hydrogen: Manifold injection method

Abstract

In the work described here, petrol is supplemented with varying amounts of hydrogen via manifold injection in Ricardo research engine. Two series of experiment were conducted: (1) keeping an overall stoichiometric mixture, and (2) enrichment of the mixture, with varying throttle and spark timing. Here we show the performance and emissions characteristics of the experimental results of stoichiometric and enrichment. Also, the stoichiometric and enrichment are compared. Four flow rates of hydrogen are chosen which correspond to hydrogen energy fraction of ~4%, ~7%, ~10% and ~14% at full throttle and hydrogen energy fractions of ~7%, ~12%, ~15% and ~19% at part throttle. Hydrogen enters the manifold just before the intake valve to reduce the risk of knocking. The results showed that near stoichiometric, at the lowest hydrogen energy fraction, torque is increased by ~0.8% compared to petrol only at full throttle and no changes to torque at part throttle. With λ~0.96 and at ~4% hydrogen energy fraction, torque is increased by ~2% compared to petrol only at full throttle and no changes to torque at part throttle. At λ~1.0, hydrogen enhances the combustion characteristics as shown by increased thermal efficiency, reduced cycle-by-cycle variability and increased rate of mass fraction burnt. For the same conditions, increases in NOx and decreases in THC are measured. With enrichment, hydrogen enhances combustion characteristics at the lowest hydrogen energy fraction; however, combustion characteristics worsen with increasing hydrogen. CO₂ and THC are reduced with enrichment. It is concluded that with hydrogen supplementation by the manifold injection method, the optimum performance is achieved at the hydrogen energy fraction of ~4% and with optimum spark timing setting.