The Engineer

Brunel air hybrid system could be on the buses in China

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Brunel University has announced it will sign a technology development and licensing deal with Guangxi Yuchai Machinery Company next week that could see the its air hybrid system installed on buses throughout China.

Guangxi Yuchai Machinery Company is the largest diesel engine manufacturer in China and supplies 70 per cent of the Chinese bus engine market.

The university’s air hybrid system is based on regenerative engine braking stop/start technology developed by a team of academics in Brunel’s Centre for Advanced Powertrain and Fuels. It is claimed to be more efficient than an electric stop/start system and can lead to better vehicle performance.

In particular, it is compatible with existing vehicle powertrain systems and the production cost is significantly lower, making it suitable for high-volume production.

Prof Hua Zhao, director of the Centre for Advanced Powertrain and Fuels at Brunel University, said the technology works by exploiting the functional capability of a current bus engine to operate temporarily as an air compressor.

’It captures and stores energy as compressed air during braking using a production engine braking device commonly installed in heavy goods vehicles. The stored compressed air can then be used to restart the engine through an air starter motor.

’Unlike standard bus engines, this means that the bus can turn off its engine when stationary and then restart it using regeneratively captured braking energy, leading to significant fuel and cost savings.

’In addition, the compressed air can be used to provide instant boost to overcome the turbo-lag that is often associated with the sluggish performance and black smoke seen from city buses.’

The air hybrid system can also minimise the use of the engine-driven air compressor on buses resulting in further fuel saving and reduced maintenance, explained Brunel’s Dr Tom Ma.

When it is installed on a city bus, the system is expected to produce a 10 per cent fuel economy benefit. Unlike an electric hybrid system, the Brunel air hybrid system can be added on to production engines and will work with existing transmission systems.

The Brunel-Guangxi Yuchai team is currently developing a prototype of the air hybrid system. A demonstration vehicle will then be built to highlight the economic and environmental benefits to Chinese bus operators ahead of expected mass production.

Mr Jie Shen, chief engineer of Guangxi Yuchai Machinery, added: ’This air hybrid engine technology is the most cost-effective fuel-saving technology for city buses in China. We will work hard to ensure that it will be implemented in production in the near future.’

The Brunel technology is also attracting interest from parties in the US and India.