Going "au naturel"

Getting diesel engines to run off natural gas

December 2012 Spotlight

Engineers at Westport Innovations Corp. used a unique one-dimensional simulation platform to model an injection system that would allow diesel engines to run on clean-burning natural gas.

Natural gas is in abundant supply and prices have remained relatively stable for years-well below that of diesel. Also, natural gas burns much cleaner with 33 percent less NOx and 20 percent lower greenhouse gas emissions than equivalent diesel-fueled engines.

Converting a diesel engine to run on natural gas is a tricky engineering problem. To provide enough power, the flow of large amounts of the natural gas, in much greater volumes than diesel fuel, must be carefully regulated and quickly delivered to the cylinder at just the right time in the combustion cycle. To complicate matters, natural gas requires a temperature of 800 degrees to ignite, considerably higher than the easy-to-achieve 500 degrees for burning diesel fuel.

Enter the liquid spark plug. Engineers have overcome these technical roadblocks with an ingenious fuel injector specifically designed for natural gas engines. At the heart of the Westport HPDI (high-pressure direct injection) system is a revolutionary injector tip assembly with dual-concentric needles. The needles serve as little valves that open as they are lifted at just the right time. This allows a small amount of diesel fuel to be injected as an ignition source-sort of a "liquid spark plug"-followed in a matter of milliseconds by large quantities of natural gas sprayed at high pressure into the combustion chamber.

To gear up for the market's growing demand for natural gas engines, Westport needed a more efficient process for developing optimal injector designs much faster. With this goal in mind, they investigated the LMS Imagine.Lab AMESim 1D simulation platform.


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