Armor & Mobility

MAR-APR 2018

Military magazines in the United States and Canada, covering Armor and Mobility, focuses on tactical vehicles, C4ISR, Special Operations Forces, latest soldier equipment, shelters, and key DoD programs

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Combat vehicle weights have been steadily increasing due to battlefield realities associated with evolving enemy threats (both conventional and asymmetrical warfare). In order to decisively confront these threats, the warfighter needs overwhelming technological battlefield superiority with greater armor protection, increased lethality weapon systems, secondary defensive weapon systems, greater electrical power generation capabilities, and enhanced prime power (mobility). These enhanced defensive and offensive capabilities result in increased vehicle weight at the cost of mobility. Under-armor volume is valuable in a combat vehicle because the weight of the vehicle increases exponentially with volume. Advances in Thermal Efficiency Through improvements in thermal efficiency and lower heat rejection, the two-stroke opposed-piston Advanced Combat Engine (ACE) will provide a reduction in total powertrain system volume, including in the intake and exhaust ducting, cooling system, air management system, fuel system, controls, and accessories. ACE also brings fuel economy improvement opportunities realized through either smaller fuel tanks (reducing under armor volume/weight) or extended vehicle range (lengthening the battlefield day). The resulting benefits from the engine's lower heat rejection to coolant will also reduce parasitic and accessory system loads (through reduced cooling system fan power), thereby increasing power available to the sprocket for increased mobility, enabling greater electrical power generation, or a combination of both. The ACE engine is being designed by Cummins with a scalable and modular architecture (250 horsepower per cylinder increments). This feature will enable a military family of combat engines that share a large number of common parts (pistons, rings, replaceable liners, injectors, connecting rods, bearings, seals, fasteners, etc.) bringing lower logistics costs (higher production and reduced price) and reduced inventory burden while minimizing technician training and lowering technical manual publication costs. Countering Rising Vehicle Mass Combat vehicle platforms have recently experienced weight gains associated with increased armor protection to offset growing improvised explosive device (IED) and other kinetic threats. Heavier vehicle weight ultimately has a detrimental effect on mobility (dash speed, side slope, acceleration, top speed, etc.). The ACE engine is designed to return lost mobility, provide extra power for electrical power generation, and enhance performance. Additionally, vehicle designs are also limited in the location and availability of openings for air flow (intake, exhaust, and cooling) with additional restrictions caused by ballistic grills. Due to the inherent high thermal efficiency of two-stroke opposed- piston engine design and the noticeably lower heat rejection to coolant, the ACE engine will help minimize under-armor volume requirements and provide fuel efficient, compact prime power solutions across a wide range of military vehicle configurations. The scalable and modular nature of the ACE enhances the engine's capability to conform to individual vehicle powertrain packaging needs with greater range, mobility, and electrical power generation. The ACE design also allows for flexible engine orientation (vertical to horizontal), greatly increasing the number of possible engine-to- transmission configurations (three transverse and two parallel) utilizing the same basic engine hardware with minor modifications. When integrated with other Advanced Powertrain Demonstrator (APD) technologies such as Advanced Combat Transmission (ACT), Integrated Starter Generator (ISG), and Advanced Thermal Management System (ATMS), installed propulsion system power density may increase from 50% to 100% depending on the vehicle application. The resulting reduction in under armor volume and weight (and reduced parasitic power losses) may deliver an estimated 20 percent improvement in vehicle fuel efficiency. EXPANDING THE COMBAT POWER ENVELOPE The U.S. Army's Tank Automotive Research and Development Center (TARDEC) has been advancing the Army's Advanced Combat Engine (ACE) program, an effort to provide existing and future ground combat vehicles with next-generation propulsion power and efficiency to address mobility needs. By John Tasdemir, Powertrain, Team Leader, U.S. Army RDECOM TARDEC GVPM John Tasdemir The Advanced Combat Engine provides enhanced power in a compact and scalable package, enabling advancements in vehicle mobility for the Army's highest-demand vehicle applications. (TARDEC) ENGINE UPGRADE ADVANCED GROUND PROPULSION www.tacticaldefensemedia.com 26 | Armor & Mobility | March/April 2018

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