Abstract
This paper investigates the performance, exhaust emissions, and combustion characteristics of a dual fuel diesel engine fueled by small amounts of hydrogen added to compressed natural gas (CNG) supplied into an intake-pipe as the main fuel. The experiments used ordinary gas oil for the ignition, and the equivalence ratios of the premixed mixtures with CNG and hydrogen were varied in the ranges 0-0.41 and 0-0.075, respectively. The brake thermal efficiency with the dual fuel operation showed similar values compared with normal diesel operation at high loads. With increasing CNG supply ratio, the CO concentration increases but this increase is suppressed significantly by the hydrogen addition. Regardless of the gas fuel, the smoke emissions decreased monotonously and sharply with increasing gas fuel (CNG + hydrogen) supply ratio. The hydrogen addition causes increases in the NOx emissions, and further study is necessary to determine ways to reduce these.
