New valve technologies for car engines could make a real difference in terms of fuel consumption and carbon dioxide emissions. With some expert help from Chinese friends, researchers have breathed new life into an EU-funded project that looked ready to fail.
The voluntary commitment by the European automotive industry to reduce carbon dioxide emissions by 20% from new car fleets by 2008 is driving a variety of research and development projects. Progressive technical modifications to engines and drive chains are already reducing greenhouse gas emissions every year, but experts say reaching the 20% target is going to demand more than modifications. Instead, truly radical advances in vehicle technology are needed.
The LIVALVES project (Light-weight valves for high-efficiency engines), funded under the European Commission’s Fifth R&D Framework Programme, is improving the way car engines work by reducing the weight of the valves that open and close to admit fuel and remove exhaust gases from engine cylinders.
Project coordinator Klaus Gebauer of TRW Deutschland, an automotive systems company, explains the advantages. “Current engines use steel valves actuated (opened and closed) by rotating cams linked to the crankshaft. This link between valve actuation and the crankshaft is necessary because steel valves are heavy and need a lot of force to move them.
“Lighter valves, on the other hand, require significantly less power to move. With this new feature available, it is much easier to envisage the use of advanced valve actuation systems, in particular electromagnetic actuators such as those developed in parallel by the European ELVAS project. This type of systems decouples valve actuation from the crankshaft and allows valve timing to be fine tuned independently to improve engine efficiency – and this is where fuel can be saved and emissions cut.”
The consortium estimates that carbon dioxide emissions, fuel consumption and engine noise could be cut by 10% by this technology – a major contribution to meeting emission targets.
The project originally had three candidate materials for the new valves: aluminium silicon alloys, titanium aluminium (TiAl) intermetallics, and ceramics. After casting and machining, protective coatings would be developed for each of these materials, before moving on to testing in a running engine. The composition of the project consortium reflects these activities; including a ceramics manufacturer, metals research groups, coating specialists as well as automotive systems and car manufacturers.
The ceramics option was dropped first, as components of sufficient quality for machining could not be developed. Further work produced valves made of aluminium silicon alloys, candidates for the cooler intake valves, but it proved too difficult to find an appropriate wear coating. Everything then depended on the TiAl intermetallics option.
The Interdisciplinary Research Centre (IRC) in Materials Processing, based at Birmingham University in the UK, was the partner responsible for delivering the TiAl intermetallics valves. However, hoped for national funding for a new metal casting facility did not materialise and the IRC was only able to produce TiAl valves using older furnace technology. The method in question commonly results in materials of high porosity and the new valves, though promising, were unusable – so the project was facing failure.
With options for the LIVALVES project disappearing fast, Xinhua Wu, a senior lecturer at the IRC, suggested contacting the Institute of Metal Research (IMR), part of the Chinese Academy of Sciences, which was already involved in joint research with the IRC. Wu had studied at the IMR before taking a Ph.D as a visiting scholar at Birmingham University.
The IMR has developed a unique casting technology for TiAl alloys combining superheating of the molten alloy with centrifugal casting that reduces porosity. They saw the advantages of their technology for the LIVALVES project and immediately undertook the necessary research work, at their own expense and in a spirit of co-operation, to develop usable TiAl valves.
The Chinese Academy of Sciences and the UK Royal Society provided support for travel under a joint research scheme. Together, the IMR and IRC delivered excellent TiAl intermetallic valves to the project. The benefits of networking were evident in this result, as Xinhua Wu says, “To a certain extent LIVALVES was at a dead end, but luckily we had other sources of help arising from the kind of international contacts that only come from student and scholar exchanges, even if these happened a long time ago, 12 years in my case.
“A further lesson is that excellence isn’t always in the most expected places – China is not a leader in automotive applications research, but when the European automotive industry is searching for innovative technologies then the materials and processing leaps needed mean you have to cast your net wider to centres of excellence outside of the normal industry players. It is here that the real benefits of international networking are seen.”
When the Chinese valves were mounted, after appropriate surface engineering in an engine test rig, they showed excellent performance and almost no wear in a mechanical simulation. Klaus Gebauer explains, “Although some smaller defects prevented us from running the valves extensively in a fired engine we could do mechanical accelerated life testing in an engine test rig. As the valves performed excellently with almost no wear after 200 hours, a short life engine test was undertaken for another 200 hours. This confirmed the extremely positive results and is reason enough for us to continue, even after the LIVALVES project has ended.
“The LIVALVES project is now over, but the co-operation between IRC, TRW and IMR is continuing – the first results are just too good to ignore. We have now received a set of valves without defects and these will be tested very extensively in a fired engine shortly, applying really challenging load cycles, as is done with steel valves during their validation.
“In view of the difficulty of developing the aluminium silicon intake valves, the new TiAl valves are being considered for use as lightweight intake valves in addition to their initial application as exhaust valves only.
“Of course there are many possibilities for replacing steel parts in cars and the co-operative relationship we have established with the IMR means we now can supply these light-weight, high-performance alloys to a variety of development programs and are open to a range of other possibilities”.
For more information on valves