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A significant driver for the development of future commercial vehicles is likely to be the introduction of fuel consumption related legislation in various regions around the world. The application of a waste heat recovery system to the powertrain of such vehicles is seen as a possible step, amongst many, to help them achieve the required fuel economy. In particular, the Rankine Cycle (a closed steam cycle) is often proposed as a potential means for deriving work from the engine exhaust heat. Rankine Cycle systems are already in use in off-highway applications, such as stationary engines or marine power-packs. However, the technical and commercial viability of these systems for on-highway, principally long haul truck application is as yet unproven. Aspects such as the in-use economy benefits, the system performance density, the component robustness and all interactions with the other vehicle systems have to be evaluated.

After many years of successful Visco fan drive applications, Behr has now transferred the Visco technology to the coolant pump drive. The continuously variable Visco drive allows the coolant pump to deliver the optimum flow dependent upon the requirements, therefore reducing the drive power to the minimum possible. Up to now coolant pumps, world wide, have almost always been powered by direct, uncontrolled drives. Consequently, the delivery and the power consumption have been directly related to the engine speed, which, in many conditions, results in an unnecessarily high flow rate. The potential to reduce the flow rate is inherent within the Visco coolant pump. As a concept with continuous control of the impeller speed it has been found to be more fuel efficient than incremental impeller speed control or concepts which only restrict or divert the flow rate. The torque transmission via the shear forces of a silicone oil results in a robust and wear-free drive unit.