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Zhang L.,Chongqing University | Kang J.,Chongqing University | Xu F.-C.,Chongqing Jianshe Motorcycle Co. | Li Y.-H.,Chongqing University | Huang Y.-S.,Institute of Armored Technique
Neiranji Xuebao/Transactions of CSICE (Chinese Society for Internal Combustion Engines)

Siemens VDO method is widely used in knock detection in gasoline engine. However, identification of knock event and evaluation of knock intensity strongly depend on the threshold of Knock Factor which is subjectively determined by experience. Research demonstrates that Knock Factor signal is random, and the signal gives a knock event in the relative way rather than the absolute way. Statistical knock diagnosis method based on distribution characteristic of Knock Factor sample was investigated by normality test such as the Lilliefors test and the D test. It is confirmed that the Knock Factor sample without knock event obeys the law of normal distribution, and the Knock Factor sample with knock event does not but can be normalized by step-by-step kicking out the peak individual of the Knock Factor sample until the sample satisfies the normality test. The kicked out individual can be identified as knock event. Statistical knock diagnosis method can avoid deciding subjectively the empirical threshold of Knock Factor, and is insensitive to the Knock Window width of Siemens VDO algorithm. Source

Zhang L.,Chongqing University | Shang H.-C.,Chongqing University | Yuan Z.-Q.,Automobile Engineering Institute of Changan Automobile Ltd. | Ma W.,Automobile Engineering Institute of Changan Automobile Ltd. | And 2 more authors.
Chongqing Daxue Xuebao/Journal of Chongqing University

Intake camshaft equipped with continuously adjustable cam phasing units is applied to a 486Q gasoline engine. Phasing strategies are researched through engine cycle simulation to achieve superior engine performance. The simulation results show that at high load and low and moderate speed of the engine, phasing adjustment can lead to 6% to 8% increase in power performance because phasing advance contributes to suppressing intake backflow at IVC(intake valve closed). Cam phases obtained from numerical optimization have good agreement with engine test. At moderate load, cycle simulations show that phasing advance can increase residual gas coefficient from 9% to 20%, and reduce NO emission by 80%, BSFC(brake specific fuel consumption) by 2% at a demonstration operation. With regard to fuel economy and emissions, adjustment and optimization of intake phasing at moderate load are further verified by engine test. At low load, technical approaches to enhance combustion stability, reduce HC emission and improve cold start are investigated. The effectiveness of suppressing exhaust backflow into intake duct by phasing retard is testified by simulation. Phasing changes at the operating condition are optimally obtained by engine test for improvement of combustion stability. Source

Shang H.-C.,Chongqing University | Zhang L.,Chongqing University | Chen H.,Chongqing Zongshen Engine Manufacture Corporation Ltd | Li F.,Chongqing Zongshen Engine Manufacture Corporation Ltd | Huang Y.-S.,Institute of Armored Technique
Neiranji Gongcheng/Chinese Internal Combustion Engine Engineering

In model 158FMI gasoline engine, effects of dual sparkplug ignition on heat release rate, cycle fluctuation and knocking were analyzed experimentally using five types of ignition control strategies. Combustion test and diagnosis results show that dual sparkplug ignition effectively promotes the combustion process, increases maximum pressure and pressure rise rate, advance the crank angle corresponding to the maximum pressure, shortens the combustion duration and reduces the cycle fluctuation coefficient. Especially under lower load, the effects are more obvious. Further analysis reveals that at full load condition, combustion duration shortening for dual sparkplug ignition is mainly in the early stage of MFB of 10% to 50%, its knock trend is greater than single sparkplug ignition; and the dual sparkplug engine potential to improve power and fuel economy largely depends on optimization of ignition advance. The effects of in-phase and out-phase ignition strategies of the dual sparkplug ignition on engine combustion characteristics are not considerable. Based on ignition strategy optimization, power of the model 158FMI gasoline engine increases by 5%~6% due to cyclic heat efficiency improvement. ©, 2014, Chinese Society for Internal Combustion Engines. All right reserved. Source

Wu L.,Chongqing University | Zhang L.,Chongqing University | Li Y.,Chongqing University | Hou J.,Chongqing University | Huang Y.,Institute of Armored Technique
2010 International Conference on Mechanic Automation and Control Engineering, MACE2010

Siemens Automotive (VDO) algorithm is widely used in the evaluation of knock. But VDO algorithm can't evaluate the intensity accurately when the knock occurs earlier than the peak pressure. An algorithm based on VDO algorithm to evaluate the knock has been developed, and is called Moving Windows algorithm. Moving Windows algorithm uses two moving windows of the same width to analyze the high frequency pressure oscillation in a specified crank angle period. The high frequency pressure oscillations' energy in one window can be evaluated by the integral of the modulus of the high frequency pressure oscillations. The knock indicators ΔKmax and KI of the Moving Windows algorithm were determined by comparing the two moving windows' energy. The Moving Windows algorithm can detect the start point of the knock, and its knock intensity indicators have better accuracy than that of the VDO algorithm. ©2010 IEEE. Source

Wang M.,Chongqing University | Zhang L.,Chongqing University | Xie B.,Chongqing University | Jiang L.,Chongqing University | Huang Y.,Institute of Armored Technique
Qiche Gongcheng/Automotive Engineering

A test system of variable valve timing (VVT) mechanism is designed for the valve phaser of a VVT engine, the working medium flow characteristics of oil control valve (OCV) is measured by test, and the testing principle of VVT dynamic response characteristics is analyzed. The dynamic response curves of the phaser with different OCVs, engine speeds and oil temperatures and pressures are obtained by using the test system. Finally the leakage of phaser are measured. Source

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