Electrically Actuated Injectors for Gaseous Fuels

Newly legislated exhaust emission standards for heavy duty engines have revived interest in the use of alternative fuels. Fuel substitution is one possible means of reducing emissions sufficiently to comply with the new standards. Two gaseous fuels, natural gas and hydrogen, are among the alternative fuels having the potential to reduce emissions. Since the density of these gases is roughly an order of magnitude smaller than typical liquid fuels, metering devices must be capable of handling correspondingly larger volumes to obtain equivalent energy flows. This need for large volume flows requires substantially larger components. In the case of timed metering devices or injectors, large components and their associated large mass require substantial force to achieve fast actuation. This paper describes the use of a powerful solenoid as an actuator for gaseous injectors. The same principles were used to design injectors for two applications. The first application involves injection of high pressure hydrogen gas directly into the cylinder of a DI diesel engine. Injection durations as short as 1.5 ms were achieved with 1800 cycles per minute. In the second application, the injector controls the flow of fumigated natural gas to the intake ports of a two stroke diesel engine so as to prevent shortcircuiting of the gas directly to the exhaust system. Natural gas is supplied at 300 psi. Again, injection durations as short as 1.5 ms were achieved with 2100 cycles per minute.

Test results illustrating the flow and operating characteristics of the two injectors are presented.