An approach to the utilization of natural gas in the DDC 6V-92TA two-stroke engine is described. Diesel pilot ignition of a lean natural gas/air matrix allows operation of the modified engine over the normal speed/load matrix. The goal of the program was to develop an engine which exhibited low emissions.
A high speed eletrically actuated natural gas valve, designed for this engine, is used to deliever natural gas in the latter half of the gas exchange process. Gas injection timing and pulsewidth are optimized to minimize loss of natural gas. Maximum substitution of diesel fuel with natural gas is 85% by energy.
Performance and emissions (steady state and transient) from the engine in diesel pilot/natural gas mode are presented and discussed. Understanding of the gas exchange process and its affect on both engine knock and natural gas retention are critical to successful engine development
Five (5) demonstration engines have been installed in 40 foot transit buses which have been undergoing field evaluation. These buses are capable of reverting to normal diesel operation. Further test cell work is being carried out in parallel to assess durability. Results of these programs are reported as well.