Abstract:

A direct injection, high-pressure common-rail diesel engine was converted into a diesel pilot-ignited
dual fuel engine using a developed dual-fuel engine control unit (ECU) for better economy and lower emissions.
A real-time diesel substitution rate control strategy for a dual fuel engine was proposed, and the control
strategy was validated by experiments. The results show that the substitution rate error between the target and
experiment was less than 5.2%, and the control strategy meets the demands of the dual fuel engine operation.
For the engine performance curves and emissions, the curves of the dual fuel mode were consistent with those
of the pure fuel mode. The maximum torque of the dual fuel mode increases 2.6% compared with that in diesel
mode with CO2 and NOx emissions decreasing 40% and 33%, and with the total hydrocarbon and CO peak
emissions increasing 20 and 6 times compared with those in the diesel mode. Therefore, the strategy is rational
and feasible for controlling natural gas dual-fuel engines.

Key words: diesel engine, high-pressure common-rail, dual fuel, natural gas, control strategy, equivalent heating value substitution