Prototype low-emissions natural gas engine saves fuel

Using a unique fuel system design, researchers at NREL have developed a prototype natural gas engine that significantly improves fuel efficiency without increasing emissions.

BODY:Using a unique fuel system design, researchers have developed a prototype natural gas engine that significantly improves fuel efficiency without increasing emissions.

A recent report from the US Department of Energy’s National Renewable Energy Laboratory (NREL) highlights the promise of the prototype medium-duty natural gas engine equipped with fuel-injected pre-chamber (FIPC) technology.

In tests conducted by Southwest Research Institute on behalf of NREL, a John Deere 8.1-liter compressed natural gas (CNG) engine equipped with a specially designed FIPC system reportedly showed fuel efficiency gains of as much as 17 percent.

Tests showed that emissions of such pollutants as oxides of nitrogen (NOx) and carbon monoxide (CO) compared favourably to those of today’s natural gas engines.

In testing, the prototype engine operated over the full speed and load range, delivering 250 horsepower at 2,200 rpm and 800 lb.-ft of torque at 1,400 rpm, which is a torque output similar to that of a diesel engine.

The FIPC engine can operate in throttleless mode across most load levels and in a ‘leaner’ mode than most spark-ignited, open-chamber natural gas engines, meaning it burns less fuel. In tests, the concept engine is said to have achieved 40 percent maximum efficiency at a speed of 1,600 rpm.

The overall performance of the FIPC engine suggests that this design could improve natural gas engines to where they can compete with their diesel counterparts in fuel efficiency while maintaining an emissions advantage.

The report is one of a series issued by NREL to provide information about promising alternative transportation technologies. Most of those reports, plus details on NREL projects and activities in alternative fuels and vehicles are available at www.afdc.nrel.gov.

A copy of the full NREL report, entitled ‘Development of a Throttleless Natural Gas Engine: Final Report’ can be found at www.ctts.nrel.gov/heavy_vehicle/natgas_pub.html