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Development of a Turbocharger for Small Aviation Diesel Engines

Description:

TECHNOLOGY AREA(S): Air Platform 

OBJECTIVE: Develop and demonstrate a turbocharger for an aviation compression-ignition engine with a maximum power of 180 hp at sea level which provides reliable boost up to 30,000-ft altitude. 

DESCRIPTION: Throughout the Department of Defense, there is a critical need for small, reliable, high-efficiency engines for unmanned aerial vehicles (UAVs). Such vehicles provide invaluable intelligence, surveillance, target acquisition, and reconnaissance directly to the warfighter. In alignment with Tactical Unit Energy Independence, the engines are multi-fuel capable to exploit local resources, and can provide extreme performance. However, there are very few propulsion system options in the 160-200 hp class available for aircraft application. Compression-ignition (CI) engines, also known as diesel engines, offer the high efficiency and low fuel consumption that the Army requires, but the existing engines were developed for automotive applications. Such engines exhibit a number of problems when operated at environmental conditions typical for the Army. The most serious problem resides in the boost system that the engine uses to force air into the cylinders, which is required to make sufficient power for the vehicle to maneuver in the low-density air found at altitude. Existing boost technology, such as turbochargers and superchargers, come directly from the automotive industry. At altitude, these automotive boost systems must run a shaft speeds outside of their design criteria, and they may dwell there for periods of time much longer than automotive applications. This can lead to unsafe operation because of resonant modes in the shaft and blades of the turbocharger. Because of this, the Army seeks to develop a new turbocharger system designed and optimized for aviation diesel engines. The primary goal is that the boost system be highly robust and reliable over the Army’s entire operating range. This includes altitudes from sea level to 30,000 feet, and temperatures from -60°F to 130°F. Significant resonances in the shafting of the system as well as compressor surge, which can reduce life or induce failure, must be avoided. The performance goal of the boost system should be to allow the engine, while operating at 30,000 feet, to provide 60% of the maximum power it provides at sea level. Through this SBIR process, it is expected that the boost technology that is developed could be commercialized. Besides the many applications in the Department of Defense, the technology will be of great value to the general aviation industry, and the rapidly expanding commercial ‘drone’ industry. 

PHASE I: Provide turbocharger concepts that can deliver air quantities for a 180-hp CI engine at sea level and 60% power (i.e. 108 hp) at 30,000 ft. These concepts should avoid shaft and compressor/turbine blade resonances as well as compressor surge. Provide analysis results of the concepts including shaft vibration and compressor/turbine blade deflection. Provide CAD models to the Army to determine interface compatibility with the existing Army engines. The manufacturability of the proposed technology should be assessed, and methods and equipment capable of production should be identified. The success of Phase I will be judged based on the metrics of air flowrates, shaft vibration, and compressor/turbine blade deflections from sea level to altitude up to 30,000 ft. Other metrics include the theoretical hardware life of target 2,000 hours, mass of less than 15 lbs, and interface compatibility with the existing Army system. 

PHASE II: Following the conceptual evaluation and analysis, the technology and manufacturing methods for a prototype should be developed and demonstrated. The prototype turbocharger should be assessed at critical operating points up to 30,000 ft altitude. The metrics will include required air flowrates to attain target engine power, shaft speed, shaft vibration, compressor/turbine blade deflections, surge, and interface compatibility with the existing Army engine. The prototype turbocharger should meet the reliability requirement of 100-hr endurance test. The turbocharger should also be affordable with a target cost less than $20K. Deliverables include a demonstration of prototype operation, formal test report, and comprehensive test and analysis results. 

PHASE III: Commercialization of the technology to the US Army and Air Force, as well as the civilian sector to solve turbocharger reliability issues at altitude for UAV applications. If the metrics assessed in Phase II exceeds the requirements of the Government for a specific application, the hardware could be incorporated into the Program of Record (POR) for future Unmanned Aircraft. 

REFERENCES: 

1: Szedlmayer, Michael, and Chol-Bum M. Kweon. Effect of Altitude Conditions on Combustion and Performance of a Multi-Cylinder Turbocharged Direct-Injection Diesel Engine. No. 2016-01-0742. SAE Technical Paper, 2016.

2:  Kim, Kenneth, Szedlmayer Michael, and Kweon Chol-Bum M. "Altitude and Fuel Property Effect on Aviation Diesel Engine Combustion: A First Look." Turbine Engine Technology Symposium, 2016.

3:  Office of the Under Secretary of Defense, "Report to Congress on Strategy to Protect United States National Security Interests in the Arctic Region." OUSD Policy A-CE2489B, December 2016.

4:  Tanya J., Gibson, "ARL opens unique combustion research lab, studies in JP-8 fuel could lead to "super engine" development." U.S. Army Research Laboratory (http://www.arl.army.mil/www/default.cfm?page=1217), October 9, 2012.

5:  Kech J., R. Hegner, and Mannle T. "Turbocharging: Key technology for high-performance engines." MTU online, January, 2014.

6:  Schweizer, Bernhard, and Mario Sievert. "Nonlinear oscillations of automotive turbocharger turbines." Journal of Sound and Vibration 321.3 (2009): 955-975.

7:  Kirk, R. G., A. A. Alsaeed, and E. J. Gunter. "Stability analysis of a high-speed automotive turbocharger." Tribology Transactions 50.3 (2007): 427-434.

8:  Holmes, R., M. J. Brennan, and B. Gottrand. "Vibration of an automotive turbocharger–a case study." Proceedings 8th International Conference on Vibrations in Rotating Machinery. 2004.

9:  Gunter, Edgar J., and Wen Jeng Chen. "Dynamic analysis of a turbocharger in floating bushing bearings." ISCORMA-3, Cleveland, Ohio (2005): 19-23.

10:  Wang, Zheng, et al. "Time-dependent vibration frequency reliability analysis of blade vibration of compressor wheel of turbocharger for vehicle application." Chinese Journal of Mechanical Engineering 27.1 (2014): 205-210.

KEYWORDS: Unmanned Aerial System, Compression Ignition, Turbocharger, Supercharger, Altitude, Aviation, Boost, Performance, Reliability, Heavy Fuel, Unmanned Ground System, Efficiency 

CONTACT(S): 

Michael Szedlmayer 

(410) 278-9020 

michael.t.szedlmayer.civ@mail.mil 

Frederick Schauer 

(937) 503-9903 

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