May 21, 2012 report
Delphi gasoline-injection engine technique rivals hybrid's edge
Running a diesel-like engine on gasoline is something that researchers have tried in the past. Diesel engines are 40 to 45 percent efficient in using the energy in fuel to propel a vehicle, compared to roughly 30 percent efficiency for gasoline engines. But diesel engines are dirty. As the Delphi engineers say, Diesel engines are challenged to meet future stringent NOx and PM emissions regulations at acceptable cost.
Tested on a single-cylinder engine, Delphi's approach is called a gasoline-direct-injection compression ignition. Engine-operating strategies leverage advanced fuel injection and air intake and exhaust controls. The researchers wrote a technical paper on the subject, which was presented at SAE, an association of engineers and other experts in aerospace, automotive, and commercial vehicle industries. Delphis team, Mark Sellnau, James Sinnamon, Kevin Hoyer, and Harry Husted are the authors of the paper, Gasoline Direct Injection Compression Ignition(GDCI) Diesel-like Efficiency with Low CO2 Emissions. Their experiments were carried out on a Ricardo Hydra light-duty single-cylinder engine, which they said was considerably flexible, with parts that can be easily interchanged.
Tests were conducted at 6 bar IMEP - 1500 rpm using various injection strategies with low-to-moderate injection pressure, they said. Their results showed that what they called triple injection GDCI achieved about eight percent greater indicated thermal efficiency and about 14 percent lower specific CO2 emissions relative to diesel baseline tests on the same engine.
The researchers reference to triple injection GDCI refers to their approach of injected gasoline in three precisely-timed bursts, avoiding the rapid combustion that has caused past experimental engines to be noisy. They also succeeded in burning the fuel faster than in conventional gasoline engines, to get the most out of the fuel.
Mark Sellnau, engineering manager of advanced powertrain technology at Delphi, says the engine could be used along with a battery pack and electric motor, as in hybrids, which may improve efficiency still more. He also added that it was not clear to him whether the cost of doing that would be worth it.
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