Alternative fuel in car design
5 September 2005
UCL's Dr Pavlos Aleiferis (Mechanical Engineering) is leading a project to investigate the adaptation of current car engine designs to use hydrogen as an alternative fuel source.
Engine manufacturers are under increasing pressure from legislative demands of low emissions, but also by the need to decrease dependency of non-renewable fuels such as oil. Hydrogen is a possible candidate as a replacement for fuels used today and can be produced by sustainable methods, such as the electrolysis of water.
"The main advantage of burning hydrogen in internal combustion engines is its lack of carbon content, leading to total absence of carbon dioxide, carbon monoxide particulate matter and unburned hydrocarbon exhaust emissions" said Dr Aleiferis.
There are two types of internal combustion engines commonly used in car manufacture today, gasoline spark ignition (SI) and diesel compression ignition (CI) engines. However, recently, significant research has been carried out worldwide on the development of homogenous charge compression ignition (HCCI) engines.
HCCI engines are a hybrid of SI and CI engines. They use a premixed charge of fuel and air, as in SI engines, but the charge is forced to auto-ignite by compression, as in CI engines. Dr Aleiferis said: "The advantages of HCCI engines are the very low nitrogen oxide emissions as well as improved efficiency. The concept of an HCCI engine using hydrogen fuel technology would result in a locally emission-free, highly efficient engine. The scope of this project is to study the key processes involved in hydrogen HCCI combustion and examine whether the mechanisms of these processes can be easily incorporated into contemporary engine designs."
A breakthrough has the potential to revolutionise the automotive industry, and bridge the gap between now and the time when fuel cell technology is a feasible option for everyday transport, said Dr Aleiferis: "UCL is the only institution that is currently focusing on this technology. Most institutions are working towards the introduction of fuel cell technology. However, all the cars on our roads will not simply disappear overnight, and I am fairly certain that I will not see full prevalence of fuel cell cars in the next couple of decades or, perhaps, even in my lifetime. What we propose is a solution that will dramatically cut emissions until we have the means to introduce alternatives. It will also keep the fun of driving alive! Furthermore, rapid introduction of hydrogen internal combustion engines into the market will push development of the necessary infrastructure to refuel with hydrogen at gas stations."
One of the problems that Dr Aleiferis has also to overcome is the 'volatile' nature of hydrogen. "In the laboratory we are able to create a completely controlled environment. We need to study hydrogen autoignition on a fundamental level in the laboratory first in order to understand how to control it before employing such technology for everyday use. We have to ensure that the hydrogen ignites consistently and efficiently in the cylinder and nowhere else."
Dr Aleiferis will employ novel techniques to quantify what goes on in a test hydrogen HCCI engine. Engine researchers use 'optical' engines in order to photograph and study in detail the inner workings of an engine. In addition, laser-based instrumentation is used for in-cylinder optical diagnostics. "With the employment of laser techniques, we can find out what's going on at a molecular level," said Dr Aleiferis. "Such techniques will be used and developed further to provide new insight into the mechanics of hydrogen combustion in piston engines and unique benchmark comparisons with gasoline-fuelled combustion."