Performance and emissions of a dual fuel two stroke bus engine

n this study, a Detroit Diesel 6V-71 transit bus two stroke engine was converted to dual fuel natural gas/diesel operation. The Electronic Dual Fuel Injection System of Alternative Fuel Systems Inc. was used as the basis for the conversion. The existing compression ratio, blower drive, and diesel injection system were retained as much as possible. The existing diesel fuel injectors were used to inject pilot diesel as controlled by an electronic rack actuator. The gaseous fuel was delivered to each cylinder by individual high speed solenoid valves which controlled the timing and volume of injected natural gas. The converted engine retained the full capability to operate on straight diesel fuel.;To compare performance and emissions, the engine was tested in both diesel only and dual fuel mode at maximum torque and over the Japanese 13-mode test. All tests were carried out on an eddy-current type dynamometer. On dual fuel, the engine performance and emissions were investigated for the two different sets of gas injection tubes.;The converted engine maintained its original power and torque levels. The specific fuel consumption was higher in dual fuel modes than in straight diesel. This was mainly due to high natural gas losses encountered during the scavenging process. The high compression ratio (18.7:1) and high air intake charge temperatures limited the diesel fuel replacement ratio. As expected for natural gas fuelling, the...