Improved fuel economy is important for many applications, but it is especially important for military vehicles. These vehicles are adding armor to protect against improvised explosive devices. They’re also adding expensive and heavy armament and communication technology. As the vehicle weight increases, so does the need for more powerful engines to maintain the same performance characteristics. And, these more powerful engines add weight.
One way to reduce this weight, however, is to use propulsion systems with high power density. A paper written by Charles Raffa, Ernest Schwarz and John Tasdemir of the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC) emphasized that the “real need is for the complete propulsion system to be power dense”. This includes the engine, transmission, cooling system, air filtration system, intake and exhaust ducting, controls, accessories, batteries, fuel systems and final drives. A key way to increase the power density of the propulsion system: use a more efficient engine, since it can dramatically reduce the volume and weight of the fuel required for a given range.
Beyond allowing military vehicles to maintain their performance characteristics while being more capable and better protected, efficient engines improve the military’s warfighting capability. These warfighting benefits are outlined in a Department of Defense (DOD) paper titled, “More Capable Warfighting through Reduced Fuel Burden”. Among them: increases in flexibility, maneuverability, simplicity and security. More efficient engines require less fuel to transport and fewer refueling operations while providing easier logistical planning, increased range and a shorter time needed to assemble a force.
In addition, beyond their contributions to warfighting, more efficient engines save money. Some estimate that the military uses nearly 2% of all liquid fuels consumed in the U.S. And, all this fuel comes at a cost. For example, the Defense Energy Support Center (DESC), which is responsible for purchasing fuel for all DOD services and agencies, reported fuel expenditures of $3.6 billion in FY2000. That number jumped to $18 billion by FY2008, a nearly a 500% increase.
On December 4, TARDEC awarded a contract to Achates Power and AVL Powertrain Engineering, Inc. for design and construction of the Next-Generation Combat Engine. Worth a total of $4.9 million, the contract involves developing a powertrain that will deliver superior fuel efficiency, high power density and low heat rejection and will be multi-fuel capable.
To meet the program requirements, AVL—one of the world’s leading engineering services companies—proposed an engine based on the Achates Power opposed-piston, two-stroke technology. Why? Our powertrain is ideally suited for the military’s needs. After more than 3,600 hours of dynamometer testing, the Achates Power engine has demonstrated outstanding fuel efficiency—21% lower brake-specific fuel consumption when benchmarked against leading, conventional diesel engines. In addition:

  • Because the design eliminates the cylinder heads, the engine has low heat rejection to coolant. This is important for military vehicles because they often operate in hot environments, and combat vehicles do not have open grills for improved airflow.
  • As a two-stroke, the Achates Power engine requires less displacement and, therefore, less overall engine size and weight to achieve the same power requirement.

These benefits—low fuel consumption, low heat rejection to coolant, and good power density—are also valuable in engines for commercial vehicles, passenger vehicles, power generation and other applications.
Over the next few years, we look forward to collaborating with AVL on this Next-Generation Combat Engine and to updating you on our progress. In the meantime, we encourage you to read our blog post, “A More Efficient Engine for Military Applications”, for specifics on why our technology is especially well suited for military use.

Engine Design Fuel Efficiency Standards Military Engine