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Development of a Robust and Reliable Turbocharger Speed Sensor



OBJECTIVE: To develop and demonstrate a highly robust and reliable speed sensor for an aviation diesel engine turbocharger with speeds as high as 250,000 rpm. 

DESCRIPTION: Both the US Army and US Airforce have a critical need for a turbocharger speed sensor for the UAV engines that can provide accurate shaft speed sensing. The highest priorities are that the sensor be robust, reliable, easy to install, and suited for rigorous operation in a military environment. At shaft speeds coinciding with resonant frequencies in the turbocharger, the blades on the compressor or turbine wheel may fail, destroying the turbocharger, and likely leading to loss of aircraft. Accordingly, the shaft speed parameter is critical to the safe operation of the turbocharger, and the air vehicle as a whole. To use with currently deployed hardware, the sensor must be able to measure speeds as high as two hundred and fifty thousand (250,000) rpm, with as many as 20 blades on the compressor wheel. The compressor blades are made of titanium, a metal which can be problematic for eddy current sensors. Because this is an aircraft application, weight is critical. Therefore, the sensor itself, and any required signal conditioners, or accessory hardware must weigh three pounds or less. The measurement system should be powered by 28 VDC power. The system should provide a voltage output that is linearly proportional to the shaft speed which can be read by the engine control unit. The system must be able to perform in the extreme environments found at altitude, where the pressure may be as low as 30 kPa (absolute), and the temperature as low as -40 °C, while compressor outlet temperature may reach as high as 200 °C. Vibration levels may reach as high as 100 g. The system should be able to perform with high reliability for no less than 500-hr under such conditions. With these requirements met, a turbocharger speed sensor could be incorporated into the operating logic of the engine control unit, thereby reducing the risk that the engine faces due to resonant modes. With the risk abated, the Army UAV engines will perform more reliably and provide the warfighter with continuous intelligence, surveillance, and reconnaissance. The sensor technology developed through the SBIR process could be widely implemented in the general aviation industry, commercial ‘drone’ industry, and in defense applications. 

PHASE I: Develop a speed sensor concept that can meet the Army requirements of turbocharger shaft speed of up to 250,000 rpm with an accuracy of +/- 2% , temperature range of -40°C to 200 °C, power supply of 28 VDC, up to 100 g acceleration, and at least 500-hr endurance test. Any required operating conditions will be provided by the Army once the contract award is made. Provide the analysis results of the concept speed sensors compared with the existing off-the-shelf ones. CAD models should be supplied 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. 

PHASE II: Develop and demonstrate the technology and manufacturing methods. Assess and quantify the measurement capabilities of the turbocharger speed sensor in realistic operating conditions in terms of temperatures and flowrates. Parameters for assessment include the Army requirements including turbocharger shaft speed of up to 250,000 rpm with an accuracy of +/- 2% , temperature range of -40°C to 200 °C, power supply of 28 VDC, up to 100 g acceleration, at least 500-hr endurance test, and electronic noise level. In addition, system complexity and ease of installation will be assessed. Manufacturing assessment will evaluate the method, repeatability, and tolerance-holding capability. Deliverables include a demonstration of the prototype sensor, a formal report, and comprehensive test and analysis results. 

PHASE III: Commercialize the technology for use by the department of defense, and private commercial sector. It is expected that the technology would be widely applicable in the general aviation industry, as well as the commercial ‘drone’ industry. Success of the project would lead to more advanced and reliable propulsion systems for future DoD UAV systems. 


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

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

5:  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.

6:  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.

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

8:  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: Speed Sensor, Eddy Current Sensor, Turbocharger, Supercharger, Proximity Sensor, Unmanned Aerial System, Compression Ignition, Altitude, Aviation, Boost, Performance, Reliability 


Jacob Temme 

(410) 278-9455 

Frederick Schauer 

(937) 503-9903 

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