'Boosted hybrid' technology offers economy

Paul Boughton

A new approach to hybrid automotive powertrain design, combining advanced pressure boosting technology with electric torque assist in one compact unit, has been demonstrated to offer a low-cost route to CO2 emission reductions and performance improvements.

By combining hybrid capability with advanced pressure boosting technology, automotive engineering specialist Integral Powertrain and power transmission innovator Nexxtdrive have created a system that will allow a gasoline C segment vehicle to deliver 170bhp with CO2 emissions of 120g/km.

The system, called the Supergen i-Hybrid, is currently undergoing hardware testing at Integral Powertrain's Milton Keynes facility in the UK. Designed to be fully compatible with conventional gasoline powertrain architecture, it is said to offer car makers all of the benefits of a hybrid transmission at around one-third of the cost of a conventional hybrid system. With substantially reduced energy storage requirements, the system provides robust performance, responsiveness and driveability that is independent of battery condition or state of charge. Supergen i-Hybrid can be applied to all mainstream gasoline engines and also diesels, acting as a pre-booster.

At the heart of the Supergen technology is a unit connected by belt to the engine crankshaft. The unit contains a compressor, two electric motor/generators and an advanced gearing system that allows the speed of the compressor to be varied from zero up to 150 times crank speed. Depending on vehicle mode, a set of control algorithms determines the energy flow between the electrical machines and a capacitor bank capable of storing 300kJ. When needed, up to 14kW of electrical energy is dynamically allocated between direct torque assist and pressure boosting to improve torque output from the engine.

Supergen i-Hybrid is all about maximising the benefits from the electrical technology says Luke Barker, technical director at Integral Powertrain. By integrating pressure boosting and hybrid functions we get much better value from our electrical machines and their associated power electronics and storage systems. Most hybrids require expensive and heavy storage systems so that electrically augmented output is available for hill climbing or towing; the i-Hybrid provides greater torque augmentation yet it is fully self-sustaining in these operating conditions." In addition to continuous torque augmentationthe i-Hybrid system also captures energy from brakingenables stop/start and provides torque assistance at launch.

With a similar diameter to a high-output alternatorthe Supergen system is straightforward to package and can be integrated with existing engine designs with no redesign or retooling required. Initial results from hardware testingbased on the use of a 1.4 litre gasoline engine in a C segment vehicledemonstrate that the Supergen i-Hybrid system delivers both exciting vehicle performance (0-100kmh in 7.7sec) and highly attractive CO2 emissions (120g/km) in a cost-effective package.

Dynamometer testing of the Supergen systemin both conventional and i-Hybrid variantsis scheduled to continue until the autumn. Designs and control strategies are mature and there has been a great deal interest in the system from major automotive OEMs. "Our technologies offer significant benefits for all kinds of vehicle hybridisation programmes from stop-start and power take-off solutions to full hybrid drivetrains says Rod Keech, chairman of Nexxtdrive, Supergen i-hybrid is creating a lot of excitement as it offers a unique solution for the increasingly important segment of smallhigh-performancelow-CO2 engines."

For more informationvisit www.integralp.com

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