automotive design 21


reduce levels of carbon dioxide and other greenhouse gases has increased in importance. This, again, directly impacts on engine design. European legislation to cap the levels of CO2 that


vehicles produce is getting ever more stringent, and similar measures are being adopted in the USA and elsewhere. At the same time, vehicle tax paid by the consumer is evolving across many countries to reward consumers who buy vehicles with lower emissions and penalise those who do not. Unlike the issues that drove the marketing in


earlier decades, the need for fuel economy and reduced emissions are unlikely to go away. In the long term we can expect to see a far greater reliance on electric vehicles with fuel cells or on cars powered by compressed natural gas or liquefied natural gas.


Split-cycle engine


What, then, are the innovations in internal combustion engine design that will carry us through the next decade or so, meeting the need to increase efficiency and reduce emissions? For one, earlier this year the Scuderi Group unveiled a proof-of-concept prototype split- cycle engine. The new engine, which its designers claim has the ability to revolutionise the long-term viability of the internal combustion engine, was unveiled as a naturally aspirated one-litre petrol unit (Fig. 1). Scuderi Group expects it to produce up to 80 per cent fewer toxins than a typical internal combustion engine and, when fully developed with turbocharged and air-hybrid components, to achieve significant gains in fuel efficiency. Scuderi’s technology divides


the four strokes of a conventional combustion cycle over two paired cylinders: one intake/compression cylinder and one power/exhaust cylinder. Unlike conventional engines that require two crankshaft revolutions to complete a single combustion cycle, the Scuderi engine requires just one. Alongside the improvements in efficiency and emissions, studies show that the Scuderi engine is capable of producing more torque than conventional petrol and diesel engines. Split-cycle engines have been


around since 1914 and, over the years, many split-cycle configurations have been developed. However, none has matched the efficiency or performance of conventional engines. In particular, previous split-cycle engines have had problems relating to poor breathing (volumetric efficiency) and low thermal efficiency.


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Fig. 2. The Z engine developed by Aumet is a diesel powerplant promises low emissions, high efficiency under part-load conditions, high power density and low manufacturing costs.


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