实时检测过热蒸汽流量计的数学模型

该文提出的数学模型,对于研制补偿式流量计有一定参改价值,可供有关用户和研制单位参考。     

发动机热膜式空气流量计设计与试验研究

针对目前国内船用双燃料发动机空气流量计设计较少以及模拟电路设计方案难以适用的问题,对流量计控制电路存在的缺陷以及非线性误差进行了研究,设计了一种基于MC9S08QD4单片机的发动机热膜式空气流量计.在充分利用芯片内部的硬件资源基础上,开发了热膜传感单元输出模拟信号采集、模/数转化以及流量信号输出控制等电路.同时,针对流量信号存在对环境温度交叉敏感等问题,采取了基于查表的自动标定方法和基于多项式拟合的误差补偿方法.对该设计进行了与标准流量计的性能对比试验和发动机不同工况下的性能对比试验.试验结果表明,该设计能有效减小的非线性误差影响以及减少工况变化对测量精度的影响,有利于实现空气流量计的自动化和智能化.     

压力与流量的波动引起的涡轮流量计的误差

本文针对新研制的低能耗高精度涡轮流理计，就其变送器前后压力变化与流量变化研究了其与仪表精度之间的关系，并量化了这一因果关系，提出了改善该型流量计精度的途径。     

质量流量计测量液体密度的特性分析

本文针对利用哥氏力质量流量计的单井计量时测量混合液体密度的问题，对其作用原理及影响测量精度的主要因素进行了理论分析，并根据已有产品的实测数据，对其基本计算公式进行了验证，说明了理论分析的正确性。     

电容角位移式智能金属管浮子流量计的研究

基于浮子流量计普遍流量方程及电容角位移式传感器检测机理的新型智能金属管浮子流量计，实现了对流量的精确测量。本文详细介绍该流量计计量原理、转换器的设计、信号的智能化处理、样机标定及误差分析，给出了3台样机均显示可喜成绩，获得较高精度。     

涡轮流量计计量液体误差的补偿方法

本文讨论了用微机实现液体计量的误差修正方法,给出了误差补偿的数学模型,与口径为10mm—80mm涡轮流计配用使计量过程中的最大相对误差修正到0.001％。     

论述气体涡轮流量计耐久性试验

介绍对气体涡轮流量计产品进行耐久性试验的重要性,以及相关的试验要求、试验装置、试验过程,证明该产品在预期的使用寿命期限内,能够保持其计量上的准确性。     

超声波流量计的弯管误差分析及修正研究

针对中小口径超声波流量计的弯管二次流误差问题,运用数值仿真技术,分析了弯管二次流垂直误差与水平误差,由二次流流线规律推导出了二次流误差的计算公式。结合实际的流量计测量范围,设定雷诺数的变化范围为3 000~50 000,定量分析了安装在弯管下游5D、10D、20D位置的流量计在不同雷诺数下的误差规律。提出了"用压力差来表现二次流强度,最终结合误差规律通过测量压力差来对弯管二次流误差进行修正"的方法。研究结果表明,在雷诺数29 000之后,10D处的二次流垂直误差超过了5D处的误差,二次流垂直误差和水平误差的最大值分别约为1.2%和0.7%,经过仿真验证结果表明,该修正方法可行。     

Hybrid inversion method for equivalent electric charge of thunder cloud based on multi-station atmospheric electric field

This article proposes the hybrid method to inverse the equivalent electric charge of thunder cloud based on the data of multi-station atmospheric electric field. Firstly,the method combines the genetic algorithm( GA) and New ton method through the mosaic hybrid structure. In addition,the thunder cloud equivalent charge is inversed based on the forw ard modeling results by giving the parameters of the thunder cloud charge structure. Then an ideal model is built to examine the performance compared to the nonlinear least squares method. Finally,a typical thunderstorms process in Nanjing is analyzed by Genetic-New ton algorithm with the help of weather radar. The results show the proposed method has the strong global searching capability so that the problem of initial value selection can be solved effectively,as well as gets the better inversion results. Furthermore,the mosaic hybrid structure can absorb the advantages of tw o algorithms better,and the inversion position is consistent with the strongest radar echo.The inversion results find the upper negative charge is small and can be ignored,w hich means the triple-polarity charge structure is relatively scientific,w hich could give some references to the research like lightning forecasting,location tracking.     

POWER FLOW ANALYSIS AND APPLICATION SIMULATION OF ELECTROMAGNETIC CONTINUOUSLY VARIABLE TRANSMISSION

With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission（EMCVT） is a novel power-split continuously variable transmission（CVT）. There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle（HEV） as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force（EMF） equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission（AT） vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.     

运用EMD和GA SVM的齿轮故障特征提取与选择

针对齿轮故障特征提取,首先将齿轮箱振动信号进行经验模态分解,得到一组固有模态函数.计算各固有模态函数的能量和矩阵的奇异值,采用Shannon熵和Renyi熵度量能量和奇异值分布,构成原始特征子集.再采用遗传算法和最小二乘支持向量机的Wrapper方法选择最优特征子集.该方法能够利用较少的特征参数集准确判别齿轮故障,提高了齿轮故障诊断的精度与效率.     

基于等厚涡轮盘结构的可靠性研究

利用有限元软件对转子进行可靠性分析时,转子的结构以及其他设计参数都是以确定量来进行分析的,不能实现所有参数的随机性分析.以弹性力学为基础,从转子的微元体出发,推导出同时考虑离心力和温度场对转子系统影响的等厚度轮盘任意一点的应力计算式和实际工程常用的变厚度轮盘任意一点的应力计算式.以传统的应力-强度干涉模型为基础,考虑转子随机结构尺寸、温度应力、转速和材料强度等参数的随机性,利用积分随机有限元方法对转子进行可靠性分析,该方法利用确定性有限元实现了随机分析,计算精度较高,实现了转子系统随机结构的可靠性分析.     

汽车发动机检测诊断技术探析

通过对现行汽车发动机检测与诊断技术的应用状况进行分析研究,从保证发动机正常工作的动力性和经济性指标方面,介绍了运用先进的汽车诊断专用设备对发动机的各项主要状态参数进行分析、处理的方法和步骤,以实现汽车发动机使用的安全性和最佳经济性的目的。     

OPTIMAL SYNTHESIS OF PLANAR 4 LIMBS 3-DOF OVERACTUATED PARALLEL MECHANISMS

Optimal synthesis of a 3-DOF 4 limbs planar parallel mechanism with actuated redundancy is studied. The kinematics equation of the mechanism is developed and the topology of the mecha-nism is classified. The kinematics and force properties of the mechanisms according to the topologies are compared. Furthermore, a global optimizing formulation is derived from the condition number that is a local index usually used to scaling the manipulability isotropy quantitatively. The optimiza-tion is solved by genetic algorithm. The numerical results show that the topology of the mechanisms can influence the kinematics and force property considerably, and the manipulation dexterity of the mechanisms can be improved distinctly by the given formulations and the suggested optimization algorithm.     

COMPUTER SIMULATION OF CONTINUOUS ELECTROMAGNETIC STIRRING FOR MAKING RHEOLOGIC SEMI-SOLID SLURRY OF ZL112Y ALUMINUM ALLOY

To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils. In the first section of the paper, eletromagnetic force field and fluid velocity field caused by single coil were simulated. The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt. And, from this result, a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established. The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment, in which the primary α was obviously refined and sphericized. Based on this simulation of single coil electromagnetic stirring, in the second section of the paper, eletromagnetic force field and fluid velocity field caused by three coils were simulated. The result of the simulation shows that, 1） there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper; 2） the electrical current intensities of three coils of 400 A, 600 A, and 400 A, which were set to top range, middle range and bottom range of the tube, respectively, were the optimum parameters of electromagnetic current intensity under the condition of this investigation; and 3） under effect of these electromagnetic current intensity, the fluid velocities of the melt in the tube were 6.3 cm/s in top range, 3.75 cm/s in middle range, and 3.9 cm/s in bottom range of it, respectively.     

基于有限脉冲响应模型的飞机磁场补偿方法

通过分析飞机磁场数学模型,将飞机磁场表示成方向余弦与其乘积项的函数.鉴于模型参数之间存在很强的复共线性,提出了基于有限脉冲响应模型飞机磁场补偿方法.该方法将光泵磁强计和三轴磁强计的输出作为有限脉冲响应模型的输入,由带通滤波器提取信号中的变化成分,再用最小方差估计有限脉冲响应模型参数,并利用有限脉冲响应模型参数计算飞机磁场.从测量总磁场中减去飞机磁场,可得到目标信号磁场数据.最后,通过计算机仿真验证了该磁场补偿方法的有效性.     

NEW SCALING METHOD FOR COMPRESSOR MAPS USING AVERAGE INFINITESIMAL STAGE

The estimation of the precise performance of existing multistage axial-flow compressors of gas turbine engines is fast becoming a great concern, as the use of gas turbine engines in the power generation and in the military industry increases. In order to reduce the analysis performance error of the traditional scaling method, a new scaling method for estimating the characteristics of multistage axial flow compressors is proposed. This novel method is based on experimental and partial data provided by engine manufacturers. Taking the effect of density-change into account, we introduce the average infinitesimal stage concept, and thereby divide the compression process into an infinite number of infinitesimal processes corresponding to infinitesimal stages. Subsequently, we adopt the corrected Reynolds analogy method for compressible flow calculation in order to ensure much better compliance with the similarity criterion. Validation checks show that the proposed method has enough precision to predict the off-design performance characteristics of multistage axial flow compressors.