Fuel Cell APU for Silent Watch and Mild Electrification of a Medium Tactical Truck

Abstract

This paper investigates the opportunities for improving truck fuel economy through the use of a Fuel Cell Auxiliary Power Unit (FC APU) for silent watch, as well as for powering electrified engine accessories during driving. The particular vehicle selected as the platform for this study is a prototype of the Family of Medium Tactical Vehicles (FMTV) capable of carrying a 5 ton payload. Peak stand-by power requirements for onboard power are determined from the projected future digitized battlefield vehicle requirements. Strategic selection of electrified engine accessories enables engine shutdowns when the vehicle is stopped, thus providing additional fuel savings. Proton Exchange Membrane (PEM) fuel cell is integrated with a partial oxidation reformer in order to allow the use of the same fuel (JP8) as for the propulsion diesel engine. The APU system is modeled and linked with the complete vehicle system simulation, and accessory duty cycles are derived for both silent watch and driving. The results indicate six-fold improvements of the silent watch fuel economy with the FC APU compared to main-engine idling, and relatively modest improvements from the mild electrification and FC APU use during the driving cycle. Combined fuel economy benefits calculated over the hypothetical daily military mission with a combined 10 hour highway/local/off-road driving and 10 hour silent watch are 20.1%.

A Strategic Investigation for Fuel Economy Improvement of Medium-Duty Tactical Truck: Preliminary Simulation and Experimental Results

“…Based on this correlation, the predicted fuel economy from GT-Drive simulation is quite acceptable for the baseline vehicle. primary, and 30% cross-country roads) [14].…”

“…This project adopts the driving cycle of [14,18] which is created from portions of the Munson Road course at the Aberdeen Proving Ground and a modified U.S. Environmental Protection Agency (EPA) driving schedule [19]. Shown in Figure 5, a typical mission schedule of the LMTV includes the beginning segments of varying vehicle speed over flat terrain with frequent accelerations and decelerations (the primary and secondary roads), and then a segment with varying grades at a constant vehicle speed (cross-country road).…”

“…Table 2 summarizes the accessory power demand of the belt driven components of a medium tactical truck. The current M1078 has a single 660 mm diameter clutchtype fan which draws 21 kW to 23 kW of power from the engine in normal operation and up to 26 kW at peak operation [14].…”

Design Under Uncertainty and Assessment of Performance Reliability of a Dual-Use Medium Truck with Hydraulic-Hybrid Powertrain and Fuel Cell Auxiliary Power Unit

“…A detailed description of the VESIM model used in this work is given in [2,8]. It includes the embedded hydraulic system consisting of a pump/motor, a transfer case, a reservoir, and an accumulator [2].…”

“…To eliminate the need for excessive near-idle engine operation and overcome the energy density and capacity disadvantages of batteries, while fully exploiting the benefits of the hybrid-hydraulic configurations, fuel cells (FC) are considered as auxiliary power units (APUs) enabling electrification of powertrain components [3][4][5][6][7]. A recent simulation-based analysis demonstrated that using a fuel cell APU can improve fuel economy up to 10% while driving and almost six times while at standstill, during the silent watch (relative to using a diesel engine only) [8]. The benefits of electrifying the accessories and powering them with the FC APU during driving are over-and-above the improvements resulting from hybridization.…”