Effect of excess air ratio on idle performance of a HCNG (H_2+CNG) engine with different hydrogen blend ratios

摘要

To investigate the idle performance of a HCNG with high hydrogen blend ratios, the effects of different excess air ratios (λ) and different hydrogen blend ratios on combustion, indicated thermal efficiency (ITE) and emissions of a 6-cylinder CNG engine were investigated. The results show that, with the increase of hydrogen blend ratio, rather high ITE can be achieved in a much wider range of λ. Under conditions of λ=1.2～1.4, emissions of CH_4, NMHC and CO are relatively low for different hydrogen blend ratios. When the hydrogen blend ratio is greater than 75%, emissions of CH_4, HMHC and CO increase only slightly with the increase of λ. NO_x emissions increase with the increase of hydrogen blend ratio. And these emissions reach their peaks for different hydrogen blend ratios under the conditions of λ=1.1-1.2.