空气辅助尿素泵电机驱动技术研究

分析了空气辅助尿素泵(ReNO_x2.0)的工作原理,并对其关键部件步进电机的控制,分别从电机驱动技术、电机加减速控制和电机驱动精度控制三方面进行了研究,使用8细分的步进电机驱动方式改善了电机的控制效果,增加步进电机的减速控制解决了原方案中尿素泵失步和堵转的问题,增加的电机驱动精度控制提升了尿素泵的转速区分度,明显降低了转速误差,改进设计后的ReNO_x2.0性能得到显著提高,基本达到进口件的性能水平。     

基于L6506/k298芯片细分步进电机驱动系统设计

步进电机广泛使用在数控领域,虽然市场有很多步进电机驱动器.但不能完全满足精密仪器高精度定位的特殊要求.文中分析了基于步进电机的恒流细分驱动原理和恒力矩均匀细分控制策略,设计了以单片机AT89C52为控制核心,结合两片8位DAC、L6506/L298芯片组成的驱动控制系统,采用细分和加减速控制技术,克服步进电机启动失步和...     

天然气发动机怠速控制的研究

本文采用步进电机式怠速控制阀对一台天然气发动机进行怠速控制,采用THB6128芯片控制步进电机,设计了怠速及过渡过程的控制策略。实验结果表明:通过对步进电机开环控制可使发动机从暖机工况快速平滑地过渡到怠速工况;通过闭环控制可使怠速转速最低稳定在550～600r/min;急减速时发动机可以平滑进入怠速工况。     

天然气发动机怠速控制的研究

本文采用步进电机式怠速控制阀对一台天然气发动机进行怠速控制,采用THB6128芯片控制步进电机,设计了怠速及过渡过程的控制策略。实验结果表明：通过对步进电机开环控制可使发动机从暖机工况快速平滑地过渡到怠速工况;通过闭环控制可使怠速转速最低稳定在550～600r/min;急减速时发动机可以平滑进入怠速工况。     

发动机怠速控制的研究

为了更好地控制怠速空气流量,以保持发动机的怠速稳定性,根据步进电机式怠速控制阀的工作原理设计了步进电机的驱动电路,并使用基于数字信号处理器(DSP)的已集成该驱动电路的控制电路板对怠速阀进行控制。分析了发动机怠速系统的控制模型,同时讨论了怠速控制方法。实验研究了怠速空气流量与步进电机位置的关系,由此可以通过怠速空气流量的计算值计算出步进电机应处的位置。     

发动机怠速控制的研究

为了更好的控制怠速空气流量,以保持发动机的怠速稳定性,本文根据步进电机式怠速控制阀的工作原理设计了步进电机的驱动电路,并使用基于DSP的已集成该驱动电路的控制电路板对怠速阀进行控制.分析了发动机怠速系统的控制模型,同时讨论了怠速控制方法.实验研究了怠速空气流量与步进电机位置的关系,由此可以通过怠速空气流量的计算值计算出步进电机应处的位置.     

基于PCC控制器的调速器步进电机失步问题研究

本文介绍了PCC控制器在某巨型水电站调速系统中的应用,主要介绍了PCC应用于水轮机调速器控制过程中出现的步进电机失步问题及改进措施.通过增加DM455发频模块监视程序、触摸屏故障录波功能、步进电机驱动器反馈监视等措施,最终查明步进电机失步产生的原因,并优化步进电机失步检测及失步后重启程序.控制程序改进后步进电机失步现象...     

基于油压比控制方法技术研究及仿真验证

燃气轮机加减速过程通常采用核心机升转速率控制,优点是加速时间稳定,测量参数精度高。随着用户对机动性要求变高,基于升转速率的控制模型无法识别燃气轮机状态,给燃气轮机加减速过程带来风险。航空发动机依据各部件间的相互匹配关系,采用油压比进行加减速控制,具备快速加减速的能力。根据燃气轮机相似原理,提出一种基于瞬态过程的各部件之间流量平衡方法,计算燃气轮机加减速供油规律。理论分析及仿真验证表明,基于油压比的控制模式能够识别燃气轮机工作状态,控制模式与升转速率控制方法相比更优。研究成果可为燃气轮机瞬态控制规律设计提供参考。     

基于PIC单片机的步进电机控制系统

采用PIC系列单片机作为步进电机控制系统的核心,实现了软件与硬件相结合的控制方法。用软件代替脉冲分配器,达到了对步进电机的最佳控制。采用单极性驱动电路对小功率步进电机进行驱动,电路简单,实用性好。用LCD显示屏对步进电机的预设工作状态进行动态显示,直观、明了。实验结果表明整个控制系统成本低,精度高,运行平稳,可靠性好。     

变频调速在DFS4005板式输送线中的应用

本文针对柴油机油漆后在板式输送线上进行飞轮、起动电机等装箱工作,阐述了采用交流变频调速后节省调速时间,加、减速性能好,并具较高的稳速精度,在专用设备的设计中是值得推广的一种调速方法。     

汽车发动机冷却系统动态特性仿真

本文建立了汽车发动机冷却系统的动态特性仿真模型,并在MATLAB/SIMULINK中对模型进行仿真计算。主要对汽车在启动、加速、减速三种情况下冷却系统的传热特性进行仿真,并将仿真结果与实验数据进行比较分析,仿真结果与实验值的相对误差在±3%以内,表明笔者的建模方法是合理的。     

柴油轿车NEDC循环的颗粒排放特性

以一台轻型柴油轿车为试验样车,采用颗粒数量及粒径分析仪对轿车NEDC循环的排气颗粒进行测试,研究其排气颗粒数量、粒径分布和几何平均粒径.结果表明:车辆加速阶段,总颗粒数密度增大且出现峰值;车辆减速阶段,总颗粒数密度先出现一个波峰,然后急剧下降,这在EUDC循环最后期的减速区域尤为明显.UDC首个循环单元的初始怠速工况下,核态颗粒数密度高于聚集态颗粒.暖机后的UDC和EUDC循环单元内,等速工况的聚集态颗粒数密度普遍高于核态颗粒.加速阶段,聚集态颗粒和核态颗粒数密度均有所升高.减速阶段,聚集态颗粒数密度降低,但核态颗粒数密度却有所升高且占主导地位,其数量分数大都在80%以上.UDC首个循环单元的单位里程颗粒数量排放最高,其余3个市区循环基本相同,而EUDC循环的单位里程排放颗粒数则明显低于UDC循环.NEDC每个循环单元的颗粒粒径均呈准正态分布,峰值粒径都出现在50～60,nm范围内.整个NEDC循环的颗粒几何平均粒径,最大为怠速工况时的55,nm,最小为减速工况时的37,nm.     

Numerical simulation of one-dimensional laminar flames propagating into reacting premixed gases

In this paper, the propagation of a one-dimensional flame front into a reacting combustible mixture was numerically studied. A simplified mathematical method, splitting the problem into a prereaction part and a flame propagation part, was applied to the completely nonstationary problem. Initially stoichiometric mixtures of H₂/O₂ and C₂H₆/O₂ were investigated for isothermal and adiabatic boundary conditions of the prereactions. In the isothermal case, the laminar burning velocity of the mixture decreased gradually with time. In conclusion, the reasons for this decrease are an increasing amount of combustion products combined with the heat loss necessary to maintain isothermal conditions. Compared with these phenomena, the accelerating effect of radical concentrations in the preflame region is of minor importance. In the adiabatic case, the laminar burning velocity increases steadily, until the ignition delay time of the initial mixture is reached. In this period, the accelerating effect resulting from the temperature increase in the preflame region dominates the decelerating effect of the increasing product concentration. The flame thickness, which was also computed for both boundary conditions, increases here for all examined flames during the time-dependent propagation through the reacting gas mixture. This change in thickness proceeds gradually in the isothermal and spontaneously in the adiabatic case.     

Non-similar solution of an unsteady mixed convection flow over a vertical cone with suction or injection

Non-similar solution of an unsteady mixed convection flow over a vertical cone in the presence of surface mass transfer has been obtained when the axis of the cone is inline with the flow. The time dependent free stream velocity varying arbitrarily with time introduces unsteadiness in the flow field. The results have been obtained for accelerating and decelerating free stream velocities. The numerical difficulties arising at the starting point of the stream wise coordinate and for time dependent flow field are overcome by applying an implicit finite difference scheme in combination with the quasilinearization technique. Numerical results are reported here to account the effects of Prandtl number, buoyancy and mass transfer (injection and suction) parameters at different streamwise locations for various times on velocity and temperature profiles, and skin friction and heat transfer coefficients.     

Heat transfer through the turbulent incompressible boundary layer in the presence of moderate pressure gradient

From the assumption that the “universal law of the wall” is applicable to the turbulent boundary layer for moderately accelerating and decelerating flows along a wall it is shown that the thickness and the eddy diffusivity variation through the thickness can be derived at any Reynolds number.

With the additional assumption that the eddy diffusivities for momentum and heat are equal solutions were carried out to the energy equation to obtain Stanton number variations with Reynolds number for both uniform wall temperature and uniform wall heat flux. Two Reynolds number values were considered at which the heating commenced, Prandtl numbers of 0.01, 0.7 and 10 were used and these cases were examined for a number of arbitrarily chosen uniform pressure gradient parameters corresponding to one dimensional diverging or converging ducts.     

Unsteady mixed convection flow over a vertical wedge

The behavior of unsteady mixed convection flow of an incompressible viscous fluid over a vertical wedge with constant suction/injection have been investigated. The unsteadiness is due to the time-dependent free stream velocity. The governing boundary layer equations along with the boundary conditions are first converted into dimensionless form by a non-similar transformation, and then resulting system of coupled non-linear partial differential equations is solved by an implicit finite-difference scheme in combination with the quasi-linearization technique. Numerical results for the effects of various parameters on velocity, temperature and concentration profiles and on their gradient at the wall are reported in the present study. The buoyancy force causes considerable velocity overshoot for low Prandtl number (Pr) fluids. Skin friction coefficient, heat and concentration transfer rates are found to alter significantly due to injection/suction for both accelerating and decelerating flow.     

Vortices within the Separation Region in a Decelerating Channel Flow （Effect of Inlet Velocity Gradient）

An experimental investigation was made into three-dimensional separated flow and the vortices within the flow separation in a decelerating channel flow generated by the suction from a porous side wall. The flows along the side and bottom walls were visualized by the surface tuft method. The turbulent internal flow was measured by the split-film probe to investigate the turbulent flow including the reverse flow. In the flow visualization for the strong decelerating flow (the suction flow ratio:0.8), two typical flow patterns appear alternatively. One is that the flow near the bottom wall separates more upstream than the flow near the top wall and a clockwise vortex can be seen in the separation region. Another is the reversal flow pattern with a counterclockwise vortex. By the turbulent flow measurement using the split-film probe, two peaks of turbulence level are observed for the strong decelerating flow case. These peaks can be related with two flow patterns mentioned above.     

Bubble separation and collision on thin wires during subcooled boiling

An experimental investigation was conducted to observe bubble separation and collision phenomena during subcooled boiling of water on heating wires, and a theoretical model was proposed to describe the associated dynamical phenomena and understand the physical significance. Both experimental and theoretical evidences indicate that interfacial thermocapillary force induced by temperature difference and their interaction between neighbor bubbles was the most important forces during bubble separation and collision. The bubble separation process with positive effectual viscosity can be divided into two stages, accelerating and decelerating stage. The collision with an immobile bubble was concluded as an elastic collision, and the two equivalent bubbles just exchanged their momentum during their collision. Bubbles coalescence characteristics were also analyzed using the collision dynamics. The theoretical conclusions were compared with experimental results, showing a reasonable agreement with each other.     

基于TR技术的开关柜局部放电超声波定位方法

针对到达时间差(TDOA)定位算法对时延误差很敏感,细小的时延误差可能造成定位失败的问题,提出了采用TR技术的开关柜局部放电超声波定位方法,该方法可忽略波形模态的影响,无需直接进行时延估计.利用实验室制作的针—板放电模型在开关柜内进行试验,验证了方法的可行性,分析了不同信噪比和传感器数量对定位精度的影响,并与TDOA定...     

基于PLC的立体仓库控制系统的设计

根据自动化立体仓库运行的基本原理和结构,在整个控制系统中以三菱FX2N系列PLC作为核心控制元件,专用键盘作为人机接口部件,控制步进电机来驱动一个有三自由度的仓库模型在高强度导轨上做三维运动。以步进电机每转输出的脉冲数为基础,通过键盘对每个仓位予以地址编码,通过PLC对命令键盘进行扫描并得到相应的仓位号,当PLC接收到来自键盘的输入命令后,便输出对应仓位的脉冲数,经过驱动器驱动步进电机按设定的方向转动一定的角度,进而控制传动部件丝杠旋转进行准确的定位,以完成货物的存取功能。