Development of Ultra-Low Emission Liquid Fuel-Fired Microturbine Engines for Vehicular Heavy Duty Applications

Worldwide regulations currently set very stringent emissions standards for new on-road heavy-duty diesel engines (HDDE’s). For example, the United States Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) require 2010 and subsequent HDDE and vehicles to emit less than 0.2 g/bhp-hr (0.27 g/kW-hr) NOx and 5.0 g/bhp-hr (6.7 g/kW-hr) CO in addition to other strictly regulated pollutants. Diesel or biodiesel fired Microturbine engines are in use in hybrid electric vehicular (HEV) urban bus applications because of their extremely low emissions. In Capstone’s model years 2001 through 2003, liquid fueled gas turbines were certified by CARB for on-road heavy duty engine use, including urban bus applications. The engines achieved a low emission level of 0.7 g/hp-hr (0.94 g/kW-hr) NOx, 0.2 g/hp-hr (0.27 g/kW-hr) CO and 0.01 g/hp-hr (0.013 g/kW-hr) PM, which met emissions compliance levels for EPA and CARB regulations until 2010. To meet the upcoming 2010 EPA and CARB HDDE regulations, continuous research and development efforts have been taken at Capstone Turbine Corporation for its C30 family engines to further reduce the criteria pollutant emissions. Pollutant emissions were measured and analyzed for a Capstone C30 engine using ultra low sulfur diesel (ULSD) and five other opportunity fuels to obtain their actual cycle emissions for a typical New York City M60 route. By injector modification alone, the C30 engine was able to achieve 62% reduction in NOx emission. Additionally, an adjustment of turbine exit temperature was able to further reduce NOx. It was predicted that the liquid-fueled C30 engines would be able to demonstrate the compliance to the 2010 EPA/CARB new ultra-low emission standards.