Recent Results on Liquid Fuelled APU for Truck Application

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%.

Section: Current Truck Related Research Initiatives Such As the 21st mentioning

confidence: 99%

Section: Stand-by Power Requirementsmentioning

confidence: 99%

Section: Vehicle Description and Modelingmentioning

confidence: 99%

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

Filipi

Louca

Stefanopoulou

et al. 2004

“…Nevertheless, there is an increasing need for on-board electric energy in both commercial and military trucks in order to supply the required power for electric accessories used during the so-called "silent-watch". 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].…”

Section: Introductionmentioning

confidence: 99%

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

Kokkolaras

Filipi

Stefanopoulou

et al. 2005

Medium trucks constitute a large market segment of the commercial transportation sector, and are also used widely for military tactical operations. Recent technological advances in hybrid powertrains and fuel cell auxiliary power units have enabled design alternatives that can improve fuel economy and reduce emissions dramatically. However, deterministic design optimization of these configurations may yield designs that are optimal with respect to performance but raise concerns regarding the reliability of achieving that performance over lifetime. In this article we identify and quantify uncertainties due to modeling approximations or incomplete information. We then model their propagation using Monte Carlo simulation and perform sensitivity analysis to isolate statistically significant uncertainties. Finally, we formulate and solve a series of reliabilitybased optimization problems and quantify tradeoffs between optimality and reliability. The most relevant design parameters of the diesel engine, fuel cell, driveline and vehicle are considered. The results demonstrate the necessity for addressing uncertainty to make valid assessments and design decisions.

“…[1] Fuel cells have the potential of having improved fuel efficiency over traditional internal combustion engines (ICE), as well as lower heat rejection, reduced emissions, and vibration/noise reduction. [2,3] One of the most important operations in a battlefield is what is called "silent watch," which means military forces are waiting to engage and/or move in the theater. A substantial percentage of time is devoted to waiting in these stationary vehicles, with an idling engine, while maintaining readiness.…”

Section: Introductionmentioning

confidence: 99%

Logistics and Capability Implications of a Bradley Fighting Vehicle with a Fuel Cell Auxiliary Power Unit

Conover¹,

Husted²,

MacBain³

et al. 2004

Modern military ground vehicles are dependent not only on armor and munitions, but also on their electronic equipment. Advances in battlefield sensing, targeting, and communications devices have resulted in military vehicles with a wide array of electrical and electronic loads requiring power. These vehicles are typically designed to supply this power via a main internal combustion engine outfitted with a generator. Batteries are also incorporated to allow power to be supplied for a limited time when the engine is off. It is desirable to use a subset of the battlefield electronics in the vehicle while the engine is off, in a mode called "silent watch." Operating time in this mode is limited, however, by battery capacity unless an auxiliary power unit (APU) is used or the main engines are restarted. Integration of a solid oxide fuel cell (SOFC) auxiliary power unit into a military vehicle has the potential to greatly extend silent watch operating time and capabilities while significantly reducing fuel use. In this paper the results of a study are presented which show the fuel usage and capability impacts of incorporating a fuel cell APU into the electrical system of a Bradley M2A3 Diesel Infantry Fighting Vehicle. Several APU sizes are presented with varying levels of electrical equipment and engine-off capability. Complete off-loading of engine-driven accessories is also studied as a scenario with the resulting impact on available engine power presented. The silent watch operating scenario shows an 86% reduction in fuel use. With fuel costing several hundred dollars per gallon as deployed on the battlefield, such a reduction is valuable. Furthermore, the SOFC APU offers 36 days of continuous silent watch using the same JP-8 fuel tank as the M2A3 without the need for a secondary fuel supply.