automotive design 23
2/4Sight engine does, with the promise of fuel savings of up to 27 per cent. Developed by Ricardo and a consortium of automotive partners, the 2/4Sight petrol engine uses novel combustion, boosting, control and valve actuation technologies to enable automatic and seamless switching between two- and four-stroke operation, thereby delivering significant performance and fuel economy improvements through aggressive downsizing (Fig. 3). The ability to operate in two-stroke mode delivers increased
power (and reduced fuel consumption) during acceleration, while switching to four-stroke mode gives high efficiency at cruising speeds. The idea is not a new one, having been tried before in the 1980s and 1990s, but the required technology to control the valves and switch modes of operation ‘on the fly’ was not sufficiently advanced. A key breakthrough came with Ricardo’s development of a patented mechanical cam switching system that was capable of delivering the required switching performance for the control strategies developed on the test bed. Air handling on the 2/4Sight concept is based on two-stage
boosting and intercooling using a Rotrex supercharger and Honeywell turbocharger. One of the problems with the traditional two-stroke engine, as discussed above, is the total-loss lubrication. However, the 2/4Sight’s boosting technology and the innovative valve actuation eliminates the need to use the crankcase for the intake charge. This means that no oil is burnt and emissions are minimised. The research prototype engine is based on a single bank of
a 2.1 litre V6, which, in six-cylinder 2/4Sight configuration, is intended to deliver levels of performance and driveability more usually associated with a V8 petrol engine of 3 or 4 litres capacity. Simulation results indicate that vehicle acceleration, including launch from rest, can be maintained with a 2.0 litre V6 2/4Sight petrol engine replacing a 3.5 litre baseline powerplant. This would deliver fuel savings of 27 per cent over the New European Drive
Cycle (NEDC) and would reduce the vehicle CO2 emissions of the baseline from 260 g/km to 190 g/km.
W
hile the engines discussed above offer significant potential, it is notable that none is yet in production. Scuderi says it is in discussion with engine manufacturers from
Asia, Europe, the USA and India, and is hopeful of seeing its engine in a production vehicle by 2012. Aumet’s Z engine has demonstrated how savings in manufacturing costs can be achieved over those for conventional four-stroke engines, so the company is now seeking a partner to deploy the Z engine in a production vehicle. Certainly it is an attractive proposition: the components used in the Z engine are similar to those already used in conventional internal combustion engines and compressors, hence there would be no need to make significant changes to the component supply chain. As for the 2/4Sight engine, having completed development
of the prototype, Ricardo and its partners are currently negotiating potential sources of funding and support for a vehicle demonstration programme. This may be a little way off, but Ricardo says that, in addition to validating the 2/4Sight concept, the research project is also delivering significant benefits in terms of its many constituent technologies that are likely be applied in the more immediate term. m
Circle 23 or ✔ at
www.engineerlive.com/ape
温度 灰尘 湿气 振动
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36