July 20, 2009--Following collaborative work with Ford Motor Company (Dearborn, MI) and GSI Group (Rugby, England), engineers at The University of Liverpool (England) have reported encouraging results in their quest for laser ignition (LI) in automobile engines. The approach offers the potential to address both increased fuel efficiency and reduced levels of harmful emissions. This month the team is embarking on the next phase of the research to develop LI systems for next-generation car engines based on efficient, downsized gasoline direct injection (GDI) technologies. The work is funded by the Carbon Trust, an independent company established by the UK government to accelerate the move to a low carbon economy.
GDI, a method for injecting fuel into the combustion chamber of each engine cylinder, enabled superior fuel efficiency--but GDI won't realize its full potential until there's an alternative to spark plugs, the 90-year old technology we still rely on to ignite the fuel, the researchers say.
Since 2002, members of the University of Liverpool's Laser Group have worked with colleagues from the Powertrain Laboratory to develop a laser ignition (LI) system that could circumvent the limitations of spark plugs and be used with existing GDI engine designs. Previous work had demonstrated successful LI in gas turbines and rockets, but automotive engines were a very different proposition.
With increasingly stringent limits on emissions from new vehicles due to come into force in the EU, the UK's Foresight Vehicle Link Programme invited researchers to submit proposals for projects which would reduce gaseous emissions significantly and help achieve reductions of 50 per cent or more in hydrocarbons, carbon monoxide and nitrous oxide emissions. Tom Shenton, head of the university's Powertrain Laboratory, had a long-standing research relationship with Ford Motor Company, while his colleague, Geoff Dearden of the Laser Group, had already collaborated with Spectron Laser Systems (which GSI Group purchased in 2003). They proposed--in partnership with Ford and Spectron--a study to determine the feasibility of LI systems for automotive engines fuelled by gasoline. The bid was successful, attracting £660,000 in public funding in 2005, with additional, in-kind funding from Ford and Spectron.
"Experience suggested that a laser operating in the near-infra red spectrum would be appropriate for this project--and that proved to be the case", says Dr Dearden. They tested a number of methods; delivering the beam through free space and channeling it into the combustion chamber through the optical plug achieved the best results--reducing the coefficient of variation and making combustion smoother and more fuel-efficient. The team identified the optimum LI configuration to achieve the best combustion stability and showed that LI enabled a greater operational window of engine parameters to be exploited, leading to reduced exhaust emissions over the full range of engine load conditions.
The team was keen to deliver the beam via optical fiber as well, since this was likely to be less susceptible to engine vibration and could facilitate improved engine layout. But the work turned out to be more difficult than the team had hoped. "The fiber didn't respond well to engine vibration, which increased the divergence of the output beam and reduced the beam mode quality," Dearden reports. "Bending the fibre was also problematical: up to 20 per cent of the beam energy was lost with small bend diameters, while tight bends caused the fibre to fail altogether after a period. What's more, the high density of laser energy can cause short or longer term degradation, causing loss of beam transmission--and therefore ignition. Careful design of laser parameters, fibre coupling and choice of optical media is crucial to avoid this. We're confident that we can solve these problems with further research."
The project has generated a series of invention disclosures, some of which have already been submitted for patent protection. Now the team has been expanded to include two more University of Liverpool researchers, Paul Dickinson and Jack Mullett . Their next phase of the research, funded by the Carbon Trust, will again involve partnership with Ford.
For more information see the full story at the University of Liverpool site. See also the Laser Ignition for IC Engines project on the Foresight Vehicle site.