Swiss researchers have developed a natural gas-and diesel-powered hybrid engine they claim emits half the CO2 of equivalent conventional systems.
Engineers at ETH Zurich redesigned a VW Golf diesel engine to run on 90 per cent natural gas. But unlike traditional gas engines, the new design is ignited by a small amount of diesel injected directly into the cylinder rather than a spark plug.
By continually monitoring and adapting the injection using pressure sensors and control algorithms, the researchers say they have increased the engine’s efficiency to a maximum of 39.6 per cent.
This gives it a fuel consumption of 2.4l per 100km (117.7mpgImp.) compared to the latest VW Golf diesel model’s rating of 3.2l per 100km (88.3mpgImp.).
Natural gas-diesel engines already exist but are typically used in industries where power is generated and used in one place – for example, to operate large machinery.
‘In a vehicle, the engine speed and load change constantly, which means the engine system is far more complicated,’ said Tobias Ott, a doctoral student at ETH who worked on the project.
To further improve the proof-of-concept device, the researchers are concentrating on increasing the temperature in the catalytic coverter by modifying control of the engine during the warm-up.
‘Our combustion engine converts heat energy into mechanical energy with such efficiency that the exhaust gas is not warm enough to create sufficient heat, particularly after start-up,’ said Ott.
The researchers linked the engine to a small electric motor to further reduce consumption, but they said it could be installed in a vehicle on its own to make it more suitable for large-scale industrial production.
Dr Christopher Onder, another of the engineers involved, said he believed the engine could be readied for series production in five years. ‘The prerequisite is that we find an industrial partner who can take charge of developing a prototype,’ he said in a statement.