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Strain Gage Based Instrumentation For In Situ Diesel Fuel Injection System Diagnostics

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1997 Annual Conference


Milwaukee, Wisconsin

Publication Date

June 15, 1997

Start Date

June 15, 1997

End Date

June 18, 1997



Page Count


Page Numbers

2.371.1 - 2.371.11



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Paper Authors

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Steven J. Hoffman

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Samuel C. Homsy

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Kevin M. Morrison

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David R. Dowling

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Zoran S. Filipi

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Dennis N. Assanis

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 2259

Strain Gage Based Instrumentation for In-Situ Diesel Fuel Injection System Diagnostics

Zoran S. Filipi, Samuel C. Homsy, Kevin M. Morrison, Steven J. Hoffman, David R. Dowling, Dennis N. Assanis W. E. Lay Automotive Lab Department of Mechanical Engineering and Applied Mechanics University of Michigan Ann Arbor, MI 48109-2121


Dynamic start of injection (SOI) is identified as one of the key injection parameters that needs to be measured during engine operation in order to study ignition delay and its impact on the qualitative and quantitative aspects of the combustion process in the direct injection diesel engine. Application of traditional SOI measurement techniques, based on needle lift sensors, to unit injection systems presents challenges. Hence, a strain gage measurement technique which is readily available to engineering students and researchers has been adopted to determine SOI for unit injection systems. A strain gage was installed on the rocker arm acting on the unit-injector plunger, and the injection pressure was calculated from the force and the diameter of the plunger. Start of injection was determined from the profile of the injection pressure as a function of crank angle, and the known injector opening pressure. A series of tests was performed on a heavy-duty turbocharged diesel engine, and measurements from 20 consecutive cycles were statistically analyzed. Very small cycle-to-cycle variations in the SOI determined from the injection pressure signal indicate that the strain gage technique is reliable and suitable for rigorous combustion analysis.


The turbocharged direct injection diesel engine dominates the heavy-duty truck engine market as the most efficient powerplant available today. The ever more stringent emission standards have prompted the development of high pressure injection systems and associated electronic controls in order to reduce the amount of particulates and nitric oxide in the exhaust [1]. Electronic injection systems not only give the designer much more control over the combustion process, but also require the use of novel diagnostic techniques in the context of mixing and combustion studies. Such experimental investigations often require a multi- disciplinary approach and therefore have very high educational value for participating engineering students. The tasks include: identification of the parameters that need to be measured for the particular study, identification of signals that will allow indirect measurements of parameters that are difficult or impossible to measure directly; and finally development of post-processing routines that will extract the relevant information from the raw measurements.

Hoffman, S. J., & Homsy, S. C., & Morrison, K. M., & Dowling, D. R., & Filipi, Z. S., & Assanis, D. N. (1997, June), Strain Gage Based Instrumentation For In Situ Diesel Fuel Injection System Diagnostics Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6796

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