TecKnow of the day
New Fuel Injection System to make Petrol Engines as Efficient as Hybrids
Delphi is developing an engine fuel injection technology that could improve the fuel economy of gas-powered cars by 50 percent, potentially rivalling the performance of hybrid vehicles at less cost. Their test engine based on the technology is similar in some ways to a highly efficient diesel engine, but runs on gasoline.This approach, called gasoline-direct-injection compression ignition combines a collection of engine-operating strategies that make use of advanced fuel injection and air intake and exhaust controls, many of which are available on advanced engines today.The researchers found that if they injected the gasoline in three precisely timed bursts; they could avoid the too-rapid combustion that’s made some previous experimental engines too noisy. At the same time, they could burn the fuel faster than in conventional gasoline engines, which is necessary for getting the most out of the fuel.
In conventional gasoline-powered engines, a spark ignites a mixture of fuel and air. Diesel engines don’t use a spark; diesels compress air until it’s so hot that fuel injected into the combustion chamber soon ignites, instead. Several researchers have attempted to use diesel like compression ignition with gasoline, but it’s proved challenging to control such engines, especially under the wide range of loads put on them as a car idles, accelerates, and cruises at various speeds.T
This technology, which is called gasoline-direct-injection compression ignition, aims to overcome the problem with sophisticated injectors and injection control. It seems considerable computer and sensor technology is getting put to work.
The research team is using other strategies to help the engine perform well at the extreme range of loads. A common example is when the engine has just been started or is running at very low speeds. The fuel mixture temperatures in the combustion chamber can be too low to achieve combustion ignition. Under these conditions, the researchers directed exhaust gases into the combustion chamber to warm it up and facilitate combustion.
This technology is the latest research attempt to combine the best qualities of diesel and gasoline engines. In the Kevin Bullis story at Technology Review the quote is 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, both quite high estimates. Meanwhile, diesel engines burn a heavier fuel with an effluent that’s more rich in larger particles like soot that require expensive exhaust-treatment technology to meet emissions regulations.
The company has demonstrated the technology in a single-piston test engine under a wide range of operating conditions. It’s beginning tests on a multicylinder engine that will more closely approximate a production engine. The fuel economy estimates suggest that engines based on the technology could be far more efficient than even diesel engines. Those estimates are based on simulations of how a midsized vehicle would perform with a multicylinder version of the new engine.