HCCI Holds Key to Gasoline Efficiency
Several obstacles still exist, but researchers at the University of Michigan are closing in on developing an affordable, reliable homogeneous charge compression ignition (HCCI) system.
Tucked away on the neatly manicured grounds of the University of Michigan campus is a nondescript red brick building. In this building, however, students and faculty are hard at work in various test labs trying to devise systems and components that can help make the gasoline engine even more efficient than it is today. One technology that has managed to garner the most attention is homogenous charge compression ignition, more commonly known as HCCI. The operating concept is pretty simple: take the best inherent benefits of a gasoline engine—low emissions—and marry them with the best of a diesel engine—improved fuel economy. The problem is getting this equation perfected to the point where an HCCI engine can run at high and low rpms without sacrificing fuel economy.
Dennis Assanis, the Jon R. and Beverly S. Holt professor of Engineering at the University of Michigan, believes his team is reaching pivotal points in their research that can make HCCI a reality. "The thermal kinetic process is very difficult to control and the one thing we have discovered is that while HCCI can give us a 15% fuel economy improvement over today's base line engine, but there are problems with combustion chamber deposits that develop during the combustion process." Assanis and his team accidentally discovered the deposits, which he calls "sponge like" in their make up in that they absorb and dissipate heat at certain times during the combustion cycle, making it increasingly difficult to maintain a precise temperature level inside the combustion chamber. This discovery is likely going to require changes to future engine control management systems to better monitor the build up of these deposits, which could require new sensor systems. "We are going to have to make sure the engine control unit will always know the status of your chamber. This will allow us to control chamber conditions better and maintain fuel economy," he says.
Maintaining consistent thermal properties is a critical part of the HCCI process, but another key area of development is expanding the operating range of HCCI beyond just low-load, low-rpm scenarios. Professor Assanis and his team are working on developing a new generation of turbos and superchargers that can help the engine operate in HCCI mode at higher speeds. "We're looking at using smaller size turbos, or what I like to call 'baby turbos,'" Assanis says. These turbo systems will likely require new material applications that can operate at lower exhaust gas temperatures because of the exacting temperature standards required to operate an engine in HCCI mode.
Assanis and his team aren't limiting their research solely to HCCI. The U of M team is also looking at developing technologies that can improve the performance of gasoline direct-injection systems. The team has devised a new set of technologies designed to provide high-speed, laser-based imaging diagnostics that can provide crucial data on in-cylinder flow, fuel-air mixture, ignition and combustion. "What we have developed here will give us a chance to look inside the beating heart of the engine the same way a doctor uses an MRI to take medical images inside your body," Professor Assanis says. The knowledge gained from this technology can be used to improve the accuracy of computational fluid dynamic (CFD) models, resulting in further reductions in product development schedules. Tom Stephens, GM's vice chairman for global product development, says this breakthrough could have a huge impact on math modeling for various aspects of future engines. "This laser activity is something we have never been able to do before...we could never see into the combustion chamber and this is going to be huge," he says.
Ford EcoBoost Hits the Line
In preparation for the launch of its new EcoBoost technology later this summer in its vehicles, Ford began production of the new 3.5-liter V6 engine at its Cleveland No.1 engine plant. The automaker’s $55-million investment in flexible tooling and a new turbo line will add 250 jobs to the facility. EcoBoost, which uses twin-turbos and direct injection to generate upwards 15% fuel economy improvement and 20% reduction in CO2 emissions, will make its debut on the 2010 Lincoln MKS, Ford Taurus SHO, Lincoln MKT and Ford Flex. The Cleveland facility has plenty of extra space to accommodate a future EcoBoost variant, as well as an additional turbo line.