US Army selects Sturman Industries to develop high pressure injection system for heavy-fuel rotary engines
The US Army Research, Development, and Engineering Command (RDECOM) has selected Sturman Industries to examine, develop, and demonstrate the use of an advanced high pressure injection system in a heavy-fuel (DF-2 and JP-8 compatibility), rotary diesel engine for unmanned and manned ground vehicle applications, per SBIR Topic A11-064.
According to the SBIR topic description, there currently is a shortcoming of heavy fuel engines that have a rated power between 10 and 80 bhp; are compatible with both JP-8 and DF-2; have high power to weight and power to volume density; provide good fuel consumption characteristics; and operate over extreme climatic ranges ranging from below -25 °F to 125°F ambient. It is difficult to adapt light-duty, automotive diesel piston engines for such applications while meeting power density, packaging, and heavy fuel needs and thus other options are under exploration, the Army says.
What could potentially fit this niche market, according to the Army, are heavy-fuel, rotary diesel engines that can provide from 10 bhp to 60 bhp per rotor; have peak brake fuel consumption of less than 0.5 lbm/bhp-hr; and have an engine power density of 1 hp/lbm for ground vehicle applications.
A major challenge with such engines revolves around the combustion system development of which the fuel injection system presents a significant challenge due to difficult spray targeting length and time scales associated with rotary diesel combustion systems. Such combustion chamber geometry have significant challenges in properly targeting injector nozzle geometry for JP-8 and DF-2 due the time varying impingement length of each injector spray and the limitation on rotor pocket geometry for enhancing spray mixing and combustion rates without excessive liquid fuel rotor impingement.
The SBIR topic is focused on developing a flexible, high pressure fuel injection system that can be integrated onto a heavy-fuel, rotary diesel engine and meet the aforementioned power density, power to weight, power to volume, and climatic operating range conditions. Such a fuel system should be able to vary start of injection timing, deliver multiple injection events when necessary, and provide adequate spray formation to avoid excessive wall wetting while providing combustion characteristics amenable to both JP-8 and DF-2.
Using digital valve technology, Sturman offers a wide range of fuel injection solutions. For a military rotary engine application, Sturman will utilize features such as flight weight design, unique injection spray, custom packaging and integrated electronics. Sturman injectors are capable of nozzle pressures from 300 to 3000 bar and injection volumes from 1 mm3 to 2100 mm3/stroke. Furthermore, multi-fuel capability is a benefit of Sturman injectors via local intensification design and materials selection, allowing for utilization of fuels such as Jet-A, Jet-A1, JP-8, JP-5, DF-2, heavy fuel oil and biodiesel.
The SBIR award has three phases:
Identify and assess fuel injection technology that will meet the performance specifications and provide a relevant bench top demonstration. The assessment should include any necessary zero- or multi-dimensional analysis that will aid in selecting the proper fuel injector and nozzle geometry including hole size(s) and angle(s), and the bench top demonstration should provide evidence that the injector has single and multiple injection capability at various injection durations representative of light to high load engine operating conditions and qualitatively has a spray pattern that will minimize combustion chamber wall impingement.
The fuel injector should have the capability for multiple injections within the operating speed envelope of a representative rotary diesel with engine shaft speeds up to 5,500 RPM and peak injection pressures between 1,000 and 2,500 bar.
Demonstrate and validate the performance of the chosen phase I fuel injection system on a rotary diesel engine through computational analysis, bench top experimentation, and relevant engine hardware demonstration with the goal of meeting the aforementioned fuel consumption target, the rated power range per rotor, and the specific power characteristics described in the description section using both JP-8 and DF-2.
Develop a fuel injection system that can be readily integrated onto a heavy fuel rotary diesel engine for commercial vehicle or military ground vehicle use. It is envisioned that this technology will be transitioned to a military rotary diesel engine manufacturer.
Sturman provides fuel injectors for the Army’s MRAPs (Mine Resistant Ambush Protected vehicles) in the battlefield. The company is also working to demonstrate the benefits of using flexible hydraulic power in the military four-legged robot project.
Sturman, in collaboration with manufacturing partners, is also pursuing low- to medium- volume production opportunities of niche valve and injection applications such as for unmanned aerial vehicles (UAV), large marine, industrial and locomotive engines. Unit volumes for these applications range from 5,000-50,000 units per year and require special features and capabilities that Sturman is uniquely equipped to deliver. In these scenarios, Sturman is positioned as a Tier 1 supplier via alignment with strategic manufacturing partners. Production is expected to begin as early as 2013.