Browse Publications Technical Papers 2013-01-0323

Investigation of Robustness Control for Practical Use of Gasoline HCCI Engine 2013-01-0323

The purpose of this study was to develop a method for detecting combustion fluctuation and noise to improve homogeneous charge compression ignition (HCCI) engine system robustness.
In the present study, the maximum rate of pressure rise (dp/dθmax) was used as an index of noise and the standard deviation of indicated mean effective pressure (σIMEP) was used as an index of HCCI combustion fluctuation. A knock sensor and crank angle sensor, which are equipped with a conventional spark ignition (SI) engine system, were used as combustion noise and fluctuation detection sensors. For acquiring knock sensor signals, the time series of data were analyzed using fast Fourier transformation (FFT). The integral value of the power spectrum shows the vibration intensity of the engine. For acquiring crank angle sensor signals, the time series of data were analyzed using the average calculation of crankshaft revolution.
As a result of having performed a basic simulation, the frequency range was preferably set to between 5 - 7 kHz because the combustion temperature of HCCI was lower than that of SI combustion. The beginning of rotational fluctuation detection was preferably set to 20 deg. ATDC CA and the ending period was set to 180 deg. ATDC CA.
A prototype control logic, which was incorporated into the analysis results mentioned above was validated on a test bench. As dp/dθmax increased by increasing the period of the negative valve overlap and the period of injection, the vibration intensity increased. Likewise, as σIMEP increased by decreasing the period of the negative valve overlap, the rotational fluctuation increased. The coefficient of determination of the detection parameters for noise and fluctuation indices was higher than 0.9. Therefore, the following detection methods were used to estimate the noise and fluctuation levels of HCCI combustion. Feedback control based on these methods was conducted on a test bench. As a result, the stability of HCCI combustion was improved.


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