A Competitive Approach to an Active Exhaust Heat Recovery System Solution 2020-01-0161
As greenhouse gas regulations continue to tighten, more opportunities to improve engine efficiency emerge, including exhaust gas heat recovery. Upon cold starts, engine exhaust gases downstream of the catalysts are redirected with a bypass valve into a heat exchanger, transferring its heat to the coolant to accelerate engine warm-up. This has several advantages, including reduced fuel consumption, as the engine’s efficiency improves with temperature. Furthermore, this accelerates readiness to defrost the windshield, improving both safety as well as comfort, with greater benefits in colder climates, particularly when combined with hybridization’s need for engine on-time solely for cabin heating. Such products have been in the market now for several years; however they are bulky, heavy and expensive, yielding opportunities for competitive alternatives. Customer voice expresses needs for less complex designs that reduce package space, mass and part count (i.e. cost) while maintaining or improving performance, including the integration of an active bypass control valve. This paper highlights the design of an exhaust heat recovery system including relative benchmarking of commercially available products, comparing various aspects of performance through modeling as well as testing, bench and vehicle. The paper also highlights performance enhancements, yielding a product that is lightweight, easy to package and contains significantly fewer components. Additionally, the applied valve and its actuator leverage decades of commercialized experiences from both active and passive exhaust valves, ensuring durability and avoidance of squeak and rattle concerns. Such overlap of components across various valve technologies also enables commercial benefits from the supply chain, as the actuator is already applied on millions of exhaust valves each year. Recommendations for future enhancements are made, such as further reduction of package volume and system cost, particularly as hybridization continues to drive significant space and financial constraints.