共查询到19条相似文献,搜索用时 937 毫秒
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为实现瞬态空燃比精确控制,提出基于小波网络逆系统的复合预测控制策略。利用小波网络辨识空燃比系统逆模型,实现对瞬态空燃比系统中进气量的动态前馈补偿,并将该逆系统与原系统串联构成一伪线性系统,然后结合动态矩阵控制对系统的扰动、误差等进行修正,实现对非线性、时滞、时变的瞬态空燃比系统的预测控制;最后利用瞬态工况试验数据进行仿真,并与台架试验数据进行对比,结果表明小波网络逆模型能高精度地逼近空燃比瞬态过程,结合动态矩阵控制可提高系统的鲁棒性和抗干扰能力,该复合预测控制策略能实现、也适合发动机瞬态工况空燃比的精确控制。 相似文献
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发动机控制单元(ECU)对空燃比的控制是通过对喷油量(喷油脉宽)的控制来完成的。ECU在控制空燃比时可采用2种方式:开环控制和闭环控制。在空燃比开环控制中,ECU先根据发动机转速和进气量,按理论空燃比(14.7:1)计算出基本喷油量,然后结合冷却液温度、负荷等发动机实际运行条件对基本喷油量进行适当修正,以使发动机在各种运行条件下均能获得最佳空燃比,这种控制方式不对实际空燃比进行监测。 相似文献
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为了解决进气管喷射汽油机在瞬态工况的空燃比控制问题,针对现有的发动机平均值模型,讨论了其中的油膜模型和油膜补偿器模型存在的问题和原因,建立了能直接用于微控制器的离散化油膜模型以及相应的油膜补偿器模型,用Matlab/Simulink对补偿效果进行仿真研究。结果表明,该模型能很好地补偿发动机瞬态工况的喷油量,把空燃比误差控制在允许的范围内,使发动机的动态响应更加迅速和平稳。 相似文献
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伏 尔伏轿车LH型电控 燃油喷射系统采用加热型氧传感器,检测实际空燃比与理论空燃比的偏差情况,控制电脑接收到空燃比偏差值后及时修正喷油量,使实际空燃比与理论空燃比相一致,降低排污,实现发动机电控单元的闭环控制。 相似文献
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车用LPG电控发动机排放控制的研究 总被引:2,自引:0,他引:2
文中所研究的LPG发动机电控系统综合利用了下列控制策略:基于步进电机步数的LPG燃料精确预控制与空燃比闭环控制;优化发动机起动后及暖机过程的空燃比控制;通过提高怠速及推迟点火的催化器快速起燃控制;通过氧传感器的加热以快速实现发动机起动后的空燃比闭环控制。并对1.8L汽油发动机进行了匹配试验,在兼顾发动机动力性及经济性的前提下有害气体排放达到欧Ⅱ法规的50%。 相似文献
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This research attempted to analyze nanoparticles and other harmful exhaust emissions in accordance with injection strategies and air-fuel ratio (AFR) changes for small diesel engines. The emission characteristics were analyzed in the medium-speed condition, which is the main driving range of a diesel engine. In the case of particulate matter (PM), the number of particles was measured, analyzed, and compared to identify the correlation and emission characteristics of nanoparticles by using a dilution device and condensation particle counter (CPC), which are international standards for particle measurement recommended by the Particulate Measurement Programme (PMP). The engine torque tended to be reduced as pilot injections were added, and the torque was increased by the increased boost pressure, but reduced by the exhaust pressure increase in a part of the low-load range. The number of nanoparticles was not influenced greatly by the change in AFR, but the reduction effect on the PM weight was great depending on the boost pressure increase. In addition, the number of nanoparticles tended to increase as the fuel injection timing became closer to TDC in all conditions, and its difference became larger with an increase in AFR. In addition, in the case of the pilot injection, nanoparticle emission showed similar characteristics depending on the main injection timing, but it was increased by advanced injection timing when performing the main injection only, and the number of the nanoparticles increased as pilot injections were added. Last, the optimal conditions for EMS calibration were analyzed by selecting the conditions of torque reduction and NOx increase within 5 % from all of the engine operating conditions; optimized conditions are presented. 相似文献
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为了更加精确地确定汽油机空燃比,使发动机在不同工况下得到最佳的动力性、经济性和排放性能,需要定时、定量地提供当量空燃比。而喷油量是基于进气量变化的,所以精确地控制进气量是整个控制系统的基础。在传统的进气歧管空气流量平均值模型(MVEM)基础上,考虑了曲轴箱强制通风系统(PCV系统)对进气量的影响,并对改进后的模型在simulink环境下进行稳态和瞬态仿真。通过分析仿真结果,得出了改进模型的进气量和进气歧管压力等参数,模拟结果更能接近实际进气过程,空燃比控制精度得到提高。还对传统进气模型提出了一些改进方向。 相似文献
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J. Lee S. Choi H. Kim D. Kim H. Choi K. Min 《International Journal of Automotive Technology》2013,14(4):551-558
Recent studies on dual-fuel combustion in compression-ignition (CI) engines, also known as diesel engines, fall into two categories. In the first category are studies focused on the addition of small amounts of gaseous fuel to CI engines. In these studies, gaseous fuel is regarded as a secondary fuel and diesel fuel is regarded as the main fuel for combustion. The objectives of these studies typically involve reducing particulate matter (PM) emissions by using gaseous fuel as a partial substitution for diesel fuel. However, the addition of gaseous fuel raises the combustion temperature, which increases emissions of nitrogen oxides (NOx). In the second category are studies focused on reactivity-controlled compression-ignition (RCCI) combustion. RCCI combustion can be implemented by early diesel injection with a large amount of low-reactivity fuel such as gasoline or gaseous fuel. Although RCCI combustion promises lower NOx and PM emissions and higher thermal efficiency than conventional diesel combustion, it requires a higher intake pressure (usually more than 1.7 bars) to maintain a lean fuel mixture. Therefore, in this study, practical applications of dual-fuel combustion with a low air-fuel ratio (AFR), which implies a low intake pressure, were systemically evaluated using propane in a diesel engine. The characteristics of dualfuel combustion for high and low AFRs were first evaluated. The proportion of propane used for four different operating conditions was then increased to decrease emissions and to identify the optimal condition for dual-fuel combustion. Although the four operating conditions differ, the AFR was maintained at 20 (? approximately equal to 0.72) and the 50% mass fraction burned (MFB 50) was also fixed. The results show that dual-fuel combustion can reduce NOx and PM emissions in comparison to conventional diesel combustion. 相似文献
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针对降雨入渗引起的暂态饱和边坡稳定性问题,考虑暂态饱和边坡重度变化、基质吸力以及暂态水压力的影响,分析了降雨入渗条件下暂态饱和边坡失稳机制,揭示了暂态水压力分布规律,并阐述了相应的暂态水压力数学计算方法。依据边坡滑动面是、否位于悬挂暂态饱和区内2种分布条件,提出了考虑暂态水压力、基质吸力及重度变化的Janbu极限平衡分析方法,并编写了可自动搜索圆弧形和折线形滑面的暂态饱和边坡稳定性计算程序。通过算例深入研究了悬挂型暂态饱和边坡安全稳定性的变化规律以及滑移机制。研究结果表明:降雨前期,由于暂态饱和区厚度较小,边坡基质吸力作用对边坡稳定性影响占主导作用;持续降雨引起暂态饱和区厚度增加条件下,边坡内暂态水压力逐渐转化为边坡失稳的主控因素,边坡安全系数持续下降;相同计算条件下,随着暂态饱和区厚度的增加,折线形滑动面的安全系数始终小于圆弧形滑动面的安全系数;折线形最危险滑动面的深度随暂态饱和区厚度的增加呈减小趋势,但普遍浅于圆弧形滑动面。圆弧形滑动面的深度呈现先减少后增加的趋势,深入研究发现此现象与边坡底部暂态水压力及边坡的抗剪强度参数密切相关。悬挂型暂态饱和边坡更容易产生浅层折线形滑动破坏。 相似文献
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根据发动机稀薄燃烧的要求,采用16位单片机MC9S12XDP512微控制器,利用其增强型输入捕捉输出比较定时器,自主开发出电控系统。采用稀燃、快燃(滚流)、推迟点火和二次喷油的可控燃烧方案,改变二次喷油比例和二次喷油时刻等参数,实现二次喷油过程的优化,在气流运动的作用下,实现了发动机稀薄燃烧复杂时序控制,明显改善燃烧过程。在稀薄燃烧发动机典型工况下,空燃比越大,二次喷油比例对燃油经济性的改善越明显。 相似文献