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.
