Study On The Feature Parameters For The Consistency Of Multi-cylinder Diesel Engine

Each cylinder of Multi cylinder engine works inconsistently will lead to the increase ofconsumption, emission and vibration of the engine, and shorten its life-cycle. Traditionalengine can’t achieve consistency control of each cylinder due to the inconsistency can’t bedetected, but the development of sensor and electronic technology made the detection andconsistency control of engine become possible. Now the common technology used to detect theconsistency of each cylinder include the cylinder pressure, transient speed, and then achieve thecontrolling of the consistency of each cylinder by the high pressure common rail technology.This paper is based on a four-cylinder diesel with common rail technology as the researchobject to acquire the influence of operating parameters of the engine in achieving the controlparameters of consistency of each cylinder based on the cylinder pressure and transient speed，provide the basis for consistency control.The transient speed measurement system is developed based on Labview software, thetransient speed is acquired through a USB-6259acquisition card after filtering and shaping theposition signal of the crankshaft, then complete the sub-cylinder and missing teeth of thetransient speed, this providing a method of transient speed in actual control of consistency ofeach cylinder by reducing the sample factor. The test results show the consistency of eachcylinder can be judged better by reducing the sample factor in the state condition of1600rpm ofthe engine.To acquire the influence of operation parameters of the engine to the feature parameters,study the effect of speed and load under low speed and load, and study effect of cooling watertemperature, injection timing and common rail pressure under idling speed condition, the testresults showed that:The feature parameters based on in-cylinder pressure at the same load as the increase ofthe engine speed: as the increase of Pmax, IMEP, CA10and CA50, the max of dp/dφdecreased; the feature parameters based on transient speed: both the max transient speed andthe min transient speed decreased, and the fluctuation amplitude and volatility are not inlinear relationship with the engine speed, besides, the waveform of transient speed isdetermined by the average speed.The feature parameters based on in-cylinder pressure at the same load as the increase ofthe engine speed: as the increase of Pmax, IMEP and the max value of dp/dφ, the CA10andCA50decreased; the feature parameters based on transient speed: the max transient speed isincreased and the min transient speed is decreased, but the fluctuation amplitude and volatilityare in linear relationship with load.The temperature of the cooling water has obvious effect on Pmax, the max valve ofdp/dφ, IMEP, and CA50when the temperature is low, this is because of the higher cooling water temperature will accelerate the higher combustion rate of the oil; the combustion timingis changed with the injection timing when the cooling water temperature is80℃，thusmaking the Pmax, max valve of dp/dφ, and CA50change, but the IMEP doesn’t change; asthe common rail pressure increased when the injection timing is-8°ATDC, the combustiontiming will advance, this will make the Pmax, max valve of dp/dφ and CA50change，andcause a higher oil consumption and cannot improve the stability of combustion.The max and min transient speed, fluctuation amplitude and volatility of transient speedare decreased as the increase of cooling water temperature; the different injection timing hasan effect on the max transient speed, fluctuation amplitude and volatility of transient speedwhen the cooling water temperature is80℃, and they are not in linear relationship with eachother, but it has no effect on the min transient speed; as the common rail pressure increasedwhen the injection timing is-8°ATDC the feature parameters based on transient speed isessentially the same.