A New Method to Measure the Spatial Distribution of Pressure Oscillations in Engine Knock Using Optical Diagnostics
KAUST DepartmentKing Abdullah University of Science and Technology, Clean Combustion Research Center, Thuwal 23900, Saudi Arabia
Mechanical Engineering Program
Physical Science and Engineering (PSE) Division
Clean Combustion Research Center
KAUST Grant NumberCRG, URF/1/3710-01-01
Permanent link to this recordhttp://hdl.handle.net/10754/676725
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AbstractEngine knock is one of the major obstacles limiting the thermal efficiency of spark-ignition (SI) engines. The in-cylinder spatial distribution of the pressure oscillation is of great importance to investigate the knock initiation and development. Using multiple pressure sensors to detect the local pressure oscillations is expensive and has a low spatial resolution. This study proposes a new method to measure the pressure oscillation distribution by monitoring the fluctuations of the local natural flame luminosity (NFL) during engine knocking combustion. To validate this method, simultaneous six-point pressure measurements and high-speed NFL imaging are implemented on an optical engine. The results indicate that end-gas auto-ignition leads to local fluctuations of both pressure and natural flame intensity. The local NFL oscillation phasing is 0.5 crank angle degrees earlier than those of the pressure signals, possibly due to the different response delays of high-speed imaging and pressure data acquisition systems. After applying a time offset and amplitude normalization, the flame luminosity oscillations could reproduce the pressure oscillations with very similar phase and frequency spectra. Based on the six channels of pressure signals, the distributions of pressure oscillation amplitude in the cylinder are exhibited by a fitted two-dimensional contour; the pressure oscillation distribution can be well predicted by the six flame monitors at the same locations. The prediction accuracy is affected by the flame monitor size and the optimal radius is between 5 and 8 mm. More flame detectors can present more details of the knock-induced pressure oscillations. A proper monitor number can maintain the measurement accuracy while keeping an appropriate computation load. The proposed new method provides a non-intrusive way to measure the spatial distribution of the knock-induced pressure oscillations, which could be directly applied in optical engines or metal engines through optical fibers.
CitationShi, H., Tang, Q., Uddeen, K., Magnotti, G., & Turner, J. (2022). A New Method to Measure the Spatial Distribution of Pressure Oscillations in Engine Knock Using Optical Diagnostics. SSRN Electronic Journal. https://doi.org/10.2139/ssrn.4098969
SponsorsFunded by the competitive research grant (CRG, URF/1/3710-01-01) from the King Abdullah University of Science and Technology (KAUST).