Effect of equivalence ratios on the power, combustion stability and NO_x controlling strategy for the turbocharged hydrogen engine at low engine speeds

Increase the equivalence ratio is a good way to improve performance of turbocharged hydrogen engines at low engine speeds. To explore the feasibility of this strategy, this paper investigated the experimental data of a 2.3 L turbocharged port fuel injection (PFI) hydrogen engine at 1500 rpm and 2000 rpm. The results showed that the power can increase from 6.8 kW to 21 kW at 2000 rpm and from 6.4 kW to 16.5 kW at 1500 rpm with increasing of the equivalence ratio. However, the equivalence ratio corroding to the biggest power is 0.8 at 1500 rpm and 0.9 at 2000 rpm because the turbocharged pressure and the volumetric efficiency at 2000 rpm are higher than the ones at 1500 rpm. The biggest BTE can reach to 30.1% at 2000 rpm and 29.3% at 1500 rpm within the range of 0.65–0.8. The covariance of indicated mean effective pressure (CoV_imep) of turbocharged hydrogen is lower than 1.5% at low engine speeds and the combustion stability increased with the increase of equivalence ratio. The NO_x can be reduced from 877 ppm to 0 ppm at 1500 rpm and from 1259 ppm to 17 ppm at 2000 rpm, which means the reduction efficiency of H₂+TWC can exceed 99%.