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Direct Injection Systems for Improved Performance, Durability, and Economy


OBJECTIVE: Develop and demonstrate an advanced high pressure, heavy fuel (JP-8) injection system for UAS/UGS applications, capable of performing multiple injections per cycle. DESCRIPTION: This effort is to develop a fast responding, light weight, direct injection system to operate within the fuel"s ignition delay time for UAS/UGS application. These systems must be applicable to engines that are 200 HP or less, either reciprocating or rotary. A technical challenge associated with the conversion of gasoline engines to heavy fuel (JP-8) is the avoidance of knock. An approach used to avoid knock is to operate within the fuel"s ignition delay time; hence to employ direct combustion chamber injection. The challenges of the reciprocating engine are to avoid end gas knock (auto ignition occurring in the end gas after spark) and to inject the fuel very late into the cycle. The challenges for the rotary engine are atomization and the avoidance of wall quenching due to its combustion chamber shape. Delaying the injection process causes higher pressure rise rates which can exceed the engine"s design capabilities. An injection system that offers fast response and multiple injections per cycle may alleviate excessive pressure rise and the avoidance of knock. Good combustion control eliminates many durability issues from overloading, shock, and combustion deposits. The shape of the combustion trace can be tailored through multiple injection pulses and combustion deposits can be controlled with better atomization and fuel patterns. Hence an injection system that offers fine atomization, fast response, and multiple injections per cycle is needed. System components are to include injectors, high pressure supply pump (1000 bar min), feed pump and controller with harness. PHASE I: Develop an improved fuel injector capable of performing multiple injections per cycle, operating at high pressures (above 1000 bar) and producing droplet sizes finer than 10 to 15 microns. These injectors will result in improvements to the direct injection process for reciprocating and rotary UAS engines. Analytical predictions of spray pattern through Computational Fluid Dynamics (CFD) and 3-D computations are desired. Bench tests of fuel system components operating at designed pressures and quantification of injection spray pattern are desired. The fuel injection system should have the capability to perform multiple injections per cycle and at engine operating speeds up to 6,000 rpm. PHASE II: Demonstrate and validate the performance of the Phase I technology in a laboratory environment on a representative engine. Engines should be of size and power appropriate for the Predator and Shadow-200 UAV class. Further analytical modeling and spray tests must supplement engine testing. The avoidance of knock while operating on JP-8 and delivering equivalent power is the desired outcome. PHASE III DUAL USE APPLICATIONS: Military Application: This technology is applicable to Air Force, Navy, and Army small, heavy fuel engines currently under development. The conversion and design of heavy fuel engines necessitates high responding injectors capable of fine atomization, fast response, and multiple injections per cycle. These injectors have the potential to be incorporated into engines such as the USAF"s Predator-Rotax 914 and the US Army"s Shadow-200 to minimize damaging effects of knock and to avoid wall quenching through fine atomization. Commercial Application: This technology has additional transition opportunities in the commercial sector for ground vehicles or civil UAVs. Companies could incorporate the injectors, high pressure supply pump, feed pump and controller with harness to optimize the fuel injection associated with the engines. This could lead to cleaner combustion that could greatly increase the life of the engine. Further, advanced direct injections systems have the potential to reduce specific fuel consumption.
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