Demonstration of Air-Power-Assist (APA) Engine Technology for Clean Combustion and Direct Energy Recovery in Heavy Duty Application 2008-01-1197

A typical pattern of city driving includes many accelerations and decelerations. A significant portion of the fuel energy is spent to accelerate a vehicle. This energy is typically wasted during subsequent decelerations. Capturing and reusing some of this energy would improve fuel economy.

At present, it is generally accepted that electric hybrids represent a proven technology capable of capturing and reusing a portion of the braking energy. The major drawback of electric hybrids remains the high initial cost of hybrid drivetrains. An Air-Power-Assist (APA) engine, also known as “air hybrid”, accomplishes the same general type of energy storage and reuse as an electric hybrid but with greater simplicity [1, 2, 3, 4, 5]. The key advantage of an air hybrid over an electric hybrid is that an electric hybrid requires an additional propulsion source i.e., a separate powertrain, whereas an air hybrid uses the existing internal combustion engine and transmission itself to collect and reuse the braking energy. In addition, the storage device is simply a high pressure air tank that does not degrade over time. Therefore, the air hybrid eliminates the large initial cost of hybrid drivetrains and the associated battery life and replacement issues of electric hybrids. In addition to electric hybrids, work has been conducted on hydraulically assisted hybrid trucks [6]. As in the case of the electric hybrid, a separate powertrain is required, in this case consisting of hydraulic pumps and motors. In addition, expensive hydraulic accumulators are required to store hydraulic fluid at high pressure. Although very impressive claims for fuel economy improvement in medium duty trucks have been obtained, many issues related to noise and packaging have yet to be resolved and demonstrated. Due to its additional equipment, the hydraulic hybrid would be expected to increase the initial cost of the truck significantly.

The first development of an APA engine system for the compressed air hybrid concept and performing experimental investigation was initiated in 2005 by the authors for a refuse truck (stop and go) application. This paper presents information concerning the design and integration of this system and the initial experimental results that were obtained.