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.
Delphi’s 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.
Delphi Fuel Injection Engine Lab Test Rig.
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.
Delphi’s 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 Delphi 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.
The Delphi 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.
Researchers have decades invested in attempts to run diesel-like engines on gasoline to achieve high efficiency with low emissions. Such engines might be cheaper than hybrid technology, since they don’t require a large battery and electric motor.
Mark Sellnau, engineering manager of advanced powertrain technology at Delphi Powertrain, says the new engine could be paired with a battery pack and electric motor, as in hybrid cars, to improve efficiency still more, although he notes that it’s not clear whether doing that would be worth the added cost.
Both gasoline and diesel engines are going to get another efficiency boost from the development of fuel injection technology. As computers, sensors and injection equipment improve and become more robust we’re sure to see better exploitation of the fuel inside engines. Carburettors seems almost quaint today, throttle body injection a cheap route to better emissions and sequential injection the power and efficiency choice.
Engineering presses on solving the problems of very quick injection timing, now with three bursts per firing, higher pressures in common fuel delivery rails, and ever more precise injectors.
While the 50% improvement seems an outlandish projection, getting gasoline fuelled engines working that well would offer many more engineering choices, it’s likely Delphi is there in the lab.
Keep it up Delphi.
By. Brian Westenhaus
Source: A Better Gasoline Engine