Adaptive Air-Fuel Ratio Control with MLP Network

This paper presents an application of adaptive neural network model-based predictive control (MPC) to the air-fuel ratio of an engine simulation. A multi-layer perceptron (MLP) neural network is trained using two on-line training algorithms: a back propagation algorithm and a recursive least squares (RLS) algorithm. It is used to model parameter uncertainties in the nonlinear dynamics of internal combustion (IC) engines. Based on the adaptive model, an MPC strategy for controlling air-fuel ratio is realized, and its control performance compared with that of a traditional PI controller. A reduced Hessian method, a newly developed sequential quadratic programming (SQP) method for solving nonlinear programming (NLP) problems, is implemented to speed up nonlinear optimization in the MPC. Keywords Air-fuel ratio control - IC engine - adaptive neural networks - nonlinear programming - model predictive control Shi-Wei Wang PhD student, Liverpool John Moores University; MSc in Control Systems, University of Sheffield, 2003; BEng in Automatic Technology, Jilin University, 2000; Current research interests automotive engine control, model predictive control, sliding mode control, neural networks.Ding-Li Yu obtained B.Eng from Harbin Civil Engineering College, Harbin, China in 1981, M.Sc from Jilin University of Technology, Changchun, China in 1986 and PhD from Coventry University, U.K. in 1995, all in control engineering. He is currently a Reader in Process Control at Liverpool John Moores University, U.K. His current research interests are in process control, engine control, fault detection and adaptive neural nets. He is a member of SAFEPROCESS TC in IFAC and an associate editor of the IJMIC and the IJISS.

Transient Air-Fuel Ratio Control in a CNG Engine Using Fuzzy Neural Networks

The fuzzy neural networks has been used as means of precisely controlling the air-fuel ratio of a lean-burn compressed natural gas (CNG) engine. A control algorithm, without based on engine model, has been (utilized) to construct a feedforward/feedback control scheme to regulate the air-fuel ratio. Using fuzzy neural networks, a fuzzy neural hybrid controller is obtained based on PI controller. The new controller, which can adjust parameters online, has been tested in transient air-fuel ratio control of a CNG engine.

Effects of Pilot Fuel Ratio on Combustion Process:Flow Field Structure and Pollutant Emissions

As the only controllable means of a micro gas turbine(MGT)combustor during unit operation,pilot fuel ratio(PFR)is the key to achieving stable combustion and low pollutant emission.This paper discusses the influence of PFR on the inner flow field structure and pollutant emissions.The steady-state three-dimensional RANS method with a 40-step reduced methane-air kinetics mechanism is used to study the reaction flow field and species field with PFR of 9.0%,12.7%,15.2%and 17.6%.Results show that,with the decrease in PFR,the axial velocity and temperature near the central axis of the combustion chamber show a tendency to decrease.A similar separation phenomenon occurred in the core pyrolysis reaction zone(measured by HCO)and oxidation zone(measured by OH),which is more conducive to promoting the oxidation of CO.The quantitative effect of the pilot flame on nitrogen oxides(NO_(x))was separated by using inert gas instead of nitrogen in combustion air.It was found that the NOx produced by the pilot flame under the operation condition with a PFR of 9.0%was 3.2×10^(−6),accounting for 17.4%of the total NOx emission,which was twice that of PFR.

Air-fuel ratio control with stochastic L_2 disturbance attenuation in gasoline engines

In this paper, the problem of stochastic L2 disturbance attenuation of the air-fuel ratio is investigated with consideration of cyclic variation of the residual gas fraction （RGF）. A stochastic robust controller is designed based on a discrete-time dynamic model in which the RGF is modeled as a stochastic process with Markovian property. Finally, the sampling process-based statistical analysis for the RGF and the validation of the proposed control law are presented through the experiments conducted on a gasoline engine test bench.

Experimental Study of Influence of Fuel Ratio on Combustion Characteristics of Diesel-Wetted Wood Powder

In this study, experiments were conducted to examine the influence of the fuel ratio(i.e., the ratio of diesel mass to wood powder mass) on the combustion characteristics of diesel-wetted wood powder, in which 0# diesel and poplar wood powder were used and well mixed. The fuel ratios were set to 0, 0.5, 1.0, 1.5, and 2.0. Fire behaviors, temperature distributions, mass loss rates, and CO concentrations were measured and analyzed. The results showed that because of the coupled effect of evaporation and the capillary force, the ignition point of diesel-wetted wood powder(less than 3°C) dropped dramatically as compared with that of pure wood powder(higher than 280°C) and pure diesel(higher than 107°C). At the early stage of combustion, diesel is lifted upwards by the capillary force, increasing both the concentration of diesel vapor and the temperature at the surface. When the surface temperature reaches that of the pyrolysis of wood powder, considerable pyrolysis gas emerges and combusts. As the flammable gas is consumed gradually, carbon combusts prominently when plenty of oxygen diffuses to its surface. Regarding the influence of the fuel ratio, the results showed that in cases with lower fuel ratios, the combustion was not self-sustainable. When the fuel ratio was relatively high, the temperature at the flame center was lower owing to incomplete combustion. More CO could be found in cases with higher fuel ratios in the early and late stages of combustion. The results could help to improve knowledge regarding combustion of fuel-wetted wood powder.

Effect of rich air/fuel ratio and temperature on NO_x desorption of lean NO_x trap

An experimental and model-based study of the effect of rich air/fuel ratios(AFRs) and temperature on the NOx slip of a lean NOx trap(LNT) was conducted in a lean-burn gasoline engine with an LNT after-treatment system. The emissions of the engine test bench and the inlet temperature of the LNT were used as the major inlet boundary conditions of the LNT. The engine periodically operated between a constant lean AFR of 23 with alterable rich AFRs of 10, 11, 12, 13, and 14. A decrease in the rich AFR of the engine strengthened the desorption atmosphere in the LNT, an effect closely related to the number of reductants, and further heightened the NOx desorption of the LNT, but with a penalty in fuel consumption. To eliminate that penalty, the inlet boundary conditions of the LNT were varied by adjusting the inlet temperature within a range between 200℃ and 400℃. An increase in inlet temperature heightened the NOx desorption of the LNT, and a NOx breakthrough occurred after the inlet temperature exceeded 390℃. To control NOx breakthrough, the inlet temperature can be adjusted to offset the strong desorption atmosphere in the LNT commonly created by a rich AFR.

Simple adaptive air-fuel ratio control of a port injection SI engine with a cylinder pressure sensor

The problem of air-fuel ratio(AFR) control of the port injection spark ignition(SI) engine is still of considerable importance because of stringent demands on emission control. In this paper, the static AFR calculation model based on in-cylinder pressure data and on the adaptive AFR control strategy is presented. The model utilises the intake manifold pressure, engine speed, total heat release, and the rapid burn angle, as input variables for the AFR computation. The combustion parameters, total heat release,and rapid burn angle, are calculated from in-cylinder pressure data. This proposed AFR model can be applied to the virtual lambda sensor for the feedback control system. In practical applications, simple adaptive control(SAC) is applied in conjunction with the AFR model for port-injected fuel control. The experimental results show that the proposed model can estimate the AFR, and the accuracy of the estimated value is applicable to the feedback control system. Additionally, the adaptive controller with the AFR model can be applied to regulate the AFR of the port injection SI engine.

Air flow control based on optimal oxygen excess ratio in fuel cells for vehicles

Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.

超音速火焰喷涂氧燃比对铁基非晶涂层性能的影响

非晶涂层具有优良的物理和化学性能,在工业中有广泛的应用。以FeCrMoCBSi非晶粉末为喷涂粉末,采用超音速火焰喷涂(HVOF)技术在不同喷涂参数下在Q235钢基板上沉积了铁基非晶涂层。通过X射线衍射仪(XRD)、差示扫描热仪(DSC)、扫描电子显微镜(SEM)、维氏显微硬度计等测试方法,探讨氧燃比对涂层显微组织、微观结构及耐磨性的影响。研究表明,随着喷涂氧燃比的减小,涂层的非晶相含量呈增加趋势。这是因为过量的氧气会降低喷涂过程中颗粒的熔化程度,并使颗粒氧化。涂层的显微硬度和耐磨性随氧燃比的减小而增加。这是因为在较小氧燃比下,颗粒熔化程度增加,与基板间润湿性增加,孔隙率减小。三种铁基非晶涂层相比于Q235钢基板均具有更加优良的耐磨性,有望成为碳钢表面保护和耐磨涂层的候选材料。

燃料配比和点火提前角对氨氢发动机的性能影响研究

针对氨氢发动机在燃料匹配比和点火提前角参数不准确时会造成发动机输出效率较低、排放增加等问题,以某款直列六缸四冲程氨氢发动机为研究对象,给出不同研究参数,在GT-POWER中建立发动机仿真模型,并使用Simulink联合仿真验证了氨氢发动机仿真模型的可行性。研究燃料配比和点火提前角对发动机的性能影响规律,结果表明:发动机在9∶1的氨氢比下有最佳的综合使用效率;26°CA点火提前角时可以提高发动机效率,降低排气温度,但不利于减少污染物排放;14°CA点火提前角时可降低污染物排放,但会影响发动机工作效率;20°CA为最佳点火提前角。研究结果可为针对氨氢发动机的标定及进一步的性能规律研究提供参考。

柴油/醇氢双燃料发动机燃烧特性试验研究

在不改变Z6170发动机结构和参数的基础上,搭建一套基于尾气余热在线重整制氢的甲醇和重整气进气歧管喷射系统,并开展了柴油/醇氢双燃料发动机的燃烧特性研究。试验结果表明,柴油/甲醇双燃料模式下,随着替代率增加,燃烧持续期(CA10-90)逐渐减少,着火延迟期逐渐增长,燃烧重心(CA50)表现出先提前后滞后的特性。柴油/醇氢双燃料模式下,在同替代率时相比于甲醇模式,着火延迟期缩短,燃烧持续期反而延长。研究结果为柴油/醇氢双燃料发动机的性能进一步优化提供了试验支持。

超临界660 MW机组直流锅炉动态特性仿真研究

为提升煤电机组灵活性,锅炉需具备良好的可控性和适应负荷快速变化的能力。锅炉灵活性与控制系统性能密切相关,而后者是基于动态特性设计的。为研究锅炉的动态特性,在Dymola平台中建立了某超临界660 MW机组直流锅炉的动态模型。结果表明:当锅炉入口参数发生扰动时,蒸汽温度的响应时间比蒸汽流量更长;当给水温度、给水量与燃料量分别阶跃增加5%时,主蒸汽温度分别变化10.2℃、-28.5℃和35.7℃;在锅炉的水煤配比调节过程中,给水量和燃料量变化时间不同会对主蒸汽温度产生不同的影响;当给水量比燃料量延迟约100 s作用时,主蒸汽温度在瞬态过程中的最大偏差相对于二者同时变化的情况减少了27.4℃;当变负荷幅度相同时,变负荷速率越大,主蒸汽参数的波动越剧烈,趋于稳定所需的时间越长。

燃料电池系统建模与供气系统控制方法

为了研究燃料电池系统的特性以及空气系统对燃料电池特性的影响,利用Simulink仿真软件对燃料电池系统进行建模,模型包括电压模型、空压机模型、阴极模型、阳极模型.分别通过前馈比例-积分-微分(proportional-integral-differential, PID)和模糊PID对燃料电池空气系统进行控制.结果表明:在负载电流变化时,前馈PID和模糊PID都能够使过氧比达到设定的常数值2.0附近,但模糊PID比前馈PID响应更快,且模糊PID控制下的燃料电池输出功率波动较小,燃料电池系统更加稳定.

黄铁矿基MFC-CW耦合系统反硝化动力学研究

研究比较了黄铁矿基双阳极MFC-CW在不同碳氮比(0和2.5)及初始硝酸盐浓度(7、14和28 mg/L)条件下上阳极和下阳极的反硝化速率,以及对不同阶段硝酸盐还原反应动力学的模拟,从动力学角度揭示系统自养-异养协同反硝化机理。结果显示:不同碳氮比下系统两阳极硝酸盐还原效果差异不大,而亚硝酸盐累积、硫酸盐生成的差别较大,两阳极处微生物群落组成相似,优势菌属的相对丰度受C/N、阳极位置影响较大;两阳极处的硝酸盐还原动力学均属于一级反应,且C/N=0时反硝化速率常数(0.0087、0.0045和0.0188/h)均小于C/N=2.5(0.0151、0.0071和0.0798/h;以上阳极为例);MFC-CW系统的反硝化动力学更符合Monod-CSTR模型,且在停留时间较长时取得更好的拟合效果,随着停留时间的增加,C/N=0时系统的反硝速率增加,C/N=2.5时系统的反硝化速率在一定范围内波动[0.6662—0.7744 g/(m^(2)·d)]。实验结果可为黄铁矿基MFC-CW的实际工程应用提供理论指导。

不同燃料外配比例烧结杯试验及烧结矿冶金性能试验

本文针对酒钢烧结生产中存在的问题,系统研究了不同燃料外配比例对烧结垂直烧结速度、成品率、利用系数、烧结时间、转鼓强度及烧结矿冶金性能等指标的影响。试验结果表明:随着燃料外配比例的增加,烧结利用系数呈先提高后降低的趋势,综合考虑最佳的燃料外配比例为60%;随着燃料外配比例的增加,烧结矿低温还原粉化率RDI_(+3.15mm)、烧结矿900℃还原度、烧结矿软化熔滴性能均变化不大,基本持平。

氧气/燃料比对超音速火焰喷涂WC-Ni涂层抗冲击性能的影响

目的研究超音速火焰喷涂工艺参数对WC-12Ni硬质合金涂层抗冲击性能的影响。方法依据氧气/燃料比(λO/F)调节工艺参数,以λO/F=1.1为基准点,分别固定氧气流量811 L/min、降低煤油流量,或者固定煤油流量22.7 L/h、增大氧气流量,均使λO/F增至1.2和1.3,制备了5组涂层,分析涂层组织及力学性质的变化规律,研究柱-面接触大载荷冲击下的涂层抗冲击行为。结果λO/F对涂层组织及力学性质的影响并非已报道的单调变化规律。固定氧气流量、降低煤油流量使λO/F由1.1增至1.3时,涂层孔隙率由0.91%增至1.24%,硬度和弹性模量分别由10.1、344.0 GPa降至8.6、313.9 GPa;冲击坑体积由2.1×10^(-3)增至3.3×10^(-3)mm^(3),且损伤微观特征由WC颗粒剥落向涂层开裂发展。当固定煤油流量、增加氧气流量使λO/F由1.1增至1.3时,孔隙率降至0.85%,硬度和弹性模量分别增至10.8、382.5 GPa,冲击坑体积增至2.6×10^(-3)mm^(3),直到λO/F=1.3时涂层表面开始出现裂纹。结合涂层硬度和弹性模量分析结果可知,在H3/E2≤8.4 MPa时,涂层发生开裂损伤,裂纹长度随着H3/E2的增加而减小。在H3/E2>8.4 MPa时,涂层损伤以WC颗粒剥落为主,且随着H3/E2的增加而减轻。高H3/E2可提高涂层的抗冲击性能,当H3/E2由6.4 MPa增至8.7 MPa时,坑体积和WC剥落程度分别降低了36%、35%。结论超音速火焰喷涂WC-Ni涂层的H3/E2定量表征了其抵抗塑性变形和开裂的能力,决定了涂层的抗冲击性能。

预混煤油/空气两相旋转爆轰传播特性数值研究

为研究预混煤油/空气两相旋转爆轰波的传播特性,以煤油蒸气/液滴为燃料,空气为氧化剂,开展了二维旋转爆轰过程的数值模拟计算,研究了气态燃料当量比和液滴直径对气液两相旋转爆轰过程中流场结构、胞格形状和数目、爆轰分数以及传播速度等特征的影响。结果表明:较高的气态燃料当量比和较小的液滴直径有利于旋转爆轰波的成功传播。气态燃料当量比为0.83时,可起爆的液滴直径增大至40μm。研究发现,爆轰波成功起爆的前提下,提高气态燃料当量比或减小液滴直径均利于胞格数目的增多和平均尺寸的减小,胞格数目为5.0~6.7,低于5.0爆轰波将无法维持传播;燃料的爆轰分数与气态燃料当量比和液滴直径有关,提高气态燃料当量比或减小液滴直径均促进燃料的爆轰分数以及爆轰波传播速度的提高,爆轰分数最高可达94.9%,爆轰波的传播速度为1 638.34~1 777.62 m/s,速度亏损在13%以内。

考虑富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统优化调度

为降低燃气轮机的碳排放水平和提高灵活性,提出了计及富氧燃烧碳捕集技术和源荷双侧响应的综合能源系统低碳经济优化策略。首先,研究了富氧燃烧技术的运行原理及其能流特性,并构建空分制氧设备和碳捕集设备的耦合模型;其次,引入可调的热电比作为供给侧响应策略,需求侧对于电力、热能以及气负荷的特性进行综合权衡,借助能源价格的引导,并考虑其相互之间的可替代属性形成需求侧响应机制;最后,通过计及气负荷碳排放的阶梯式碳交易约束碳排放,以系统运行成本为目标优化各时段机组出力。设置多场景进行仿真分析,结果表明富氧燃烧碳捕集技术能够有效减少系统的碳排放量,源荷双侧响应能够灵活调节供给侧与需求侧的供能关系,并有效减少系统运行成本。

烘炉燃烧器空燃比精细化控制研究与现场应用

为提高燃烧器的燃烧效率,并研究精细化控制空燃比在燃烧器中的应用效果。采用燃气和空气量分别精细化控制的方法和装置,在燃烧器运行过程中,获取多个最佳空燃比数据,根据空燃比数据生成控制曲线。燃烧器控制系统可根据控制曲线,自主控制空气阀门和燃气阀门开度。通过测量尾烟的CO含量进行节能评价。结果表明,精细化控制空燃比,可精准控制空气阀门和燃气阀门开度,不同阀门开度情况下空燃比可调,尾烟的的CO含量低。说明精细化控制空燃比可有效提高燃烧器的燃烧效率、节约燃气耗量、降低碳排放。

二冲程柴油发动机冷起动控制策略研究

二冲程航空柴油发动机中,由于柴油粘性大,导致雾化质量较差。改善燃油的雾化质量,能够有效提高冷起动性能。利用GT-Power软件建立了二冲程柴油发动机一维冷起动模型,并校核了模型的准确性;将此模型计算出的压力和温度作为三维仿真模型的边界条件,研究了冷起动不同阶段采用多大的点火提前角、空燃比有利于起动,以及喷油结束时刻、喷油量和燃油温度对起动性能的影响。结果表明:拖动阶段,推迟点火,增加喷油量,有利于形成良好的混合气;起动阶段,较大的点火提前角能够改善起动性能,喷油量较多则会造成燃烧速率减小,不利于起动;稳定阶段和暖机阶段的点火提前角小于起动阶段,能够稳定转速。推迟喷油结束时刻,有利于形成良好的分层混合气;喷油量增大和燃油温度提高,在一定范围内能够改善混合气质量。