The Influence of Cooling Air-Path Restrictions on Fuel Consumption of a Series Hybrid Electric Off-Road Tracked Vehicle

Electrification of off-road vehicle powertrains can increase mobility, improve energy efficiency, and enable new utility by providing high amounts of electrical power for auxiliary devices. These vehicles often operate in extreme temperature conditions at low ground speeds and high power levels while also having significant cooling airpath restrictions. The restrictions are a consequence of having grilles and/or louvers in the airpath to prevent damage from the operating environment. Moreover, the maximum operating temperatures for high voltage electrical components, like batteries, motors, and power-electronics, can be significantly lower than those of the internal combustion engine. Rejecting heat at a lower temperature gradient requires higher flow rates of air for effective heat exchange to the operating environment at extreme temperature conditions. High airflow rates, coupled with significant airpath restrictions, result in significant cooling power requirements and increased fuel consumption. This simulation-based study evaluates an off-road series hybrid tracked vehicle over High-speed and Complex-terrain driving scenarios at high ambient temperatures. From this case study it is found that 4-6% of fuel is utilized to cool the vehicle without air-path restriction. When significant restrictions are added to the air-path, the total percentage of fuel consumed to cool the powertrain increased to 11-16%.