A Synchronous Machine Model With Saturation and Arbitrary Rotor Network Representation

This paper addresses equivalent circuit and magnetic saturation issues associated with synchronous machine modeling. In the proposed synchronous machine model, the rotor equivalent circuits are replaced by arbitrary linear networks. This allows for elimination of the equivalent circuit parameter identification procedure since the measured frequency response may be directly embedded into the model. Magnetic saturation is also represented in both the$q$- and$d$-axis. The model is computationally efficient and suitable for dynamic time-domain power system studies.     

A Voltage-Behind-Reactance Synchronous Machine Model With Saturation and Arbitrary Rotor Network Representation

A voltage-behind-reactance formulation of a synchronous machine model is set forth, which incorporates saturation and cross-saturation, and is general enough to encapsulate a variety of rotor structures by use of arbitrary linear networks instead of equivalent circuits. Specifically, the model's equations - originally expressed in the qd-axes framework - are rewritten in such a way as to allow the actual abc stator windings to be represented by inductive branches, which can then be naturally connected in the desired circuit topology, e.g., to a rectifier. The model's predictions are validated against experimental results.     

Characterization of the Rotor Magnetic Field in a Brushless Doubly-Fed Induction Machine

The large increase in wind generation could improve the final development of wind systems with brushless doubly-fed induction machines (BDFIM) as an alternative to the doubly-fed asynchronous machines. For this reason, a detailed study of several aspects of the BDFIM design, as well as of its rotor configuration, is absolutely essential. In this paper, the authors present an alternative formulation of the BDFIM operating principle in synchronous mode. Besides the basic equation of the machine operation, it presents as main advantage the precise characterization of all the magnetic field components in a BDFIM with idealized stator windings and an idealized rotor cage. Based on this formulation, the paper provides a standard that may be used to compare the fields created by different real BDFIMs. This standard has been validated by laboratory tests.      

Generalized Procedure for Improved Accuracy of Thermal Contact Resistance Measurements for Materials With Arbitrary Temperature-Dependent Thermal Conductivity

Thermal contact resistance (TCR) is most commonly measured using one-dimensional steady-state calorimetric techniques. In these experimental methods, a temperature gradient is applied across two contacting beams and the temperature drop at the interface is inferred from the temperature profiles of the rods that are measured at discrete points. During data analysis, thermal conductivity of the beams is typically taken to be an average value over the temperature range imposed during the experiment. Here, a generalized theory is presented that accounts for temperature-dependent changes in thermal conductivity. The procedure presented enables accurate measurement of TCR for contacting materials whose thermal conductivity is any arbitrary function of temperature. For example, it is shown that the standard technique yields TCR values that are about 15% below the actual value for two specific examples of copper and silicon contacts. On the other hand, the generalized technique predicts TCR values that are within 1% of the actual value. The method is exact when thermal conductivity is known exactly and no other errors are introduced to the system.     

转子中心孔修磨机的设计与应用

介绍了转子中心孔修磨机的设计原理及应用。     

Comparison of a CFD Analysis and a Thermal Equivalent Circuit Model of a TEFC Induction Machine With Measurements

For a totally enclosed fan-cooled induction machine, two methods of numerical analysis are compared with measurements. The first numerical method is based on computational fluid dynamics (CFDs) and the second one uses a thermal equivalent circuit (TEC). For the analysis based on CFD, a 3-D induction machine including housing is modeled. The numeric solution of the flow equations is determined for stationary temperature distributions. For the TEC, a discretized one-and-a-half-dimensional model of the induction machine is considered. With the TEC model, stationary and transient operating conditions can be simulated. Measurement results are determined by iron–copper–nickel sensors embedded in the stator winding and the housing, as well as by an IR sensor for measuring the rotor temperature. With these measurement signals, stationary and transient operating conditions can be analyzed. For stationary operating conditions, additionally, the housing temperatures are determined by an IR camera. The investigated simulation and measurement methods reveal different local and global temperatures, and thus, only certain aspects and characteristics of the obtained temperatures can be compared. Nevertheless, certain conclusions can be drawn from comparing these aspects considering the actual restrictions of each of the applied methods.      

Model-Based Digital Generator Control Unit for a Variable Frequency Synchronous Generator With Brushless Exciter

This paper presents the design and implementation of a digital signal processor (DSP)-based generator control unit (GCU) for a variable frequency synchronous generator with brush-less exciter. A novel model-based control algorithm is proposed to better account for the wide operating frequency range and various load conditions. In addition to the model-based inner-loop exciter field current regulator and outer-loop generator voltage regulator, the control algorithm also adopts a generator-model-based d-axis current feed-forward loop to compensate for the load disturbance. Simulation and test results show a considerable performance improvement for the new controller when compared to the existing controllers, including better dynamics, better damping stability margin, and more uniform response over the operating range.     

A Simplified Model as the Basis for a Thermal Storage Test Procedure

A generalized thermal storage model is described whose parameters are identified using a test procedure. Provision is made for time and/or temperature dependent parameters. The same model is used for establishing the long term system performance.

The equations describing the model are solved numerically with a scheme that yields high accuracy during the identification phase but great speed during the long term system simulation. Examples are given for the use of the model in the identification phase and in a “long term” five day dynamic test sequence. These results indicate that the generalized model is a promising basis for testing and comparing thermal storage devices.     

燃气轮机拉杆转子有限元模型研究及临界转速计算

现代燃气轮机转子主要为拉杆转子,其形式分为中心单根或周向多根拉杆.无论哪种形式,拉杆转子已经不再是连续结构,轮盘之间的接触面将对转子动力学特性产生影响.首先分析了拉杆转子的受力情况,然后考虑接触面接触刚度对转子动力特性的影响,对传统的有限元方法进行了改进,并编写了相应的计算程序.最后计算了光轴、一对接触圆盘算例和某型真实燃气轮机拉杆转子的临界转速,并分别与传统有限元方法、三维有限元方法和测量值进行比较,验证了该改进有限元模型的正确性和有效性.     

A Double Excited Synchronous Machine for Direct Drive Application—Design and Prototype Tests

This paper presents the analytical, numerical, and experimental results obtained with a double excited synchronous machine (DESM) prototype designed and constructed for an electric vehicle traction system. To obtain a wide speed range, the flux-weakening technique is implemented. Analytical design, 2-D finite element method (FEM) analysis, thermal analysis, and prototype construction of the DESM are discussed, and the performances are assessed with experimental data.     

管程组合转子传热及阻力特性的实验研究

借助于实验手段,分别以油和水为管程工质,研究了管程组合转子的传热及阻力特性,同时将转子自身结构参数对传热及阻力特性的影响进行了比较分析,分析结果表明,Re数在500～8000的层流区和转捩区内,增大转子螺旋角度对传热强化的贡献显著;Re数在1×104～1×105的旺盛湍流区内,增大转子外径对传热强化的贡献明显,从而为转子组合式强化传热装置的工业应用奠定了基础。     

Experimental Characterization and Model Verification of Thermal Conductivity from Mesoporous to Macroporous SiOC Ceramics

Based on the chemical cross-linking method, this paper uses polydimethylsiloxane with various viscosities of 10 cSt, 20 cSt, 50 cSt, and 100 cSt to synthesize mesoporous and macroporous SiOC ceramics. Their thermal conductivities are measured by using 3ω method with high accuracy. Three typical models for their thermal conductivities, i.e., series model(SM), maxwell-Eucken 1 model(ME1), and effective medium theory(EMT) model, are utilized to derive the empirical formula through the multi-parameter linear optimization algorithm, which agrees well with the experimental results. The effects of pore size and specific surface area on the overall thermal conductivity of the porous structure are explored. Interestingly, it is found that the thermal conductivities of both gas phase and solid phase inside the porous structure increase with the increasing pore size at the nanometer scale, but the overall thermal conductivity of the porous structure decreases with the increasing pore size. Scanning electron microscopy graphs corroborate that the extension of the heat transfer route and the barrier of more pores between the solid phases together cause the reduction of the gas-solid coupling thermal conductivity of SiOC ceramics with larger pore size. On the contrary, the miniaturization of individual particles through modulating the synthesis parameters can increase the number of small pores in the sample itself to meet the pseudo-lattice vibration conditions, which results in the increment of the gas-solid coupling thermal conductivity and the overall thermal conductivity of the porous structure. These findings would provide meaningful guidance for designing SiOC porous ceramic super-insulation materials with extremely low thermal conductivity.     

汽轮机转子二维温度场在线仿真模型建立

在一体化过程模型开发平台(IMMS)的仿真系统支撑下,开发了汽轮机转子二维温度场有限元模型的通用仿真算法,并采用工程模块化的建模方法建立了汽轮机转子二维温度场的在线仿真模型(便于汽轮机转子和所划分网格几何尺寸的修改).通过仿真试验与同条件下的二维解析结果作了对比,结果表明:所建立的仿真模型具有计算精度高、计算速度快和通用性强等优点.同时,该模型还可用于其它具有类似边界条件轴对称体结构的热状态分析.     

N200型汽轮机低压转子轴承振动分析及处理

通过对某电厂一台汽轮机启动过程振动数据的分析,判断出造成低压转子轴承振动大的主要原因是转子质量不平衡.采用高速动平衡的方法,使低压转子在开、停机过临界及3 000r/min时的轴承振动均达到优良标准.     

转子的弯扭耦合振动研究

利用预应力法研究转子的弯扭耦合振动,计算了在弯扭耦合振动过程中转轴上的最大应力.分析了弯扭耦合振动的原因.     

石砭峪水库泄洪洞复合圆弧曲线弯道水力特性试验研究

石砭峪水库泄洪洞弯段布置为大底坡急流弯道，为调整其水流流态，进行了水工模型试验。根据隧洞已开挖的现状，又要较好的控制洞内水流流态，试验中曾对弯道体型进行了多次修改比较，其中复合圆弧弯道体型较好的控制了急流弯道水流流态。本文结合该工程试验研究，着重对复合圆弧弯道水流特性及其控制急流效果进行了阐述。并提出了急流弯道的初步选型方法。     

柴油机金属丝纤维过滤器的模拟和试验验证

建立了一个包括过滤器内部流场和颗粒沉积过程的数值模型。计算得到的过滤效率与柴油机试验的测量结果有较好的一致性。通过模型分析，解释了颗粒尺寸、废气流速等参数对过滤效率的影响机制。     

Experimental Characterization of a Compact Milli-Channel Heat Exchanger for Liquid–Liquid Heat Transfer

Abstract

The use of Milli-Channel Heat Exchangers (MCHE) presents numerous assets: efficient heat transfer, huge compactness, and limited pressure drop. For an engineer, the Fanning friction factor and the convective heat transfer coefficient are two main parameters to describe the performance of a heat exchanger. A brazed MCHE with rectangular channels in stainless steel made by the Institut für Mikrotechnik Mainz (IMM, Mainz, Germany) has been characterized experimentally and theoretically in a counter-current configuration. The selected working fluids are deionized water and oil without any phase change during experiments. The pilot unit ensures measurements of pressure drops, temperatures, and volumetric flow rate of each fluid flowing in laminar regime. A one-dimensional model has been developed. The temperature and pressure profiles of each fluid are represented by differential equations associated with boundary conditions. The system of coupled equations consists in a two-point boundary value problem solved numerically by the Matlab software. The parameters of a Nusselt number correlation are identified together with those of a Fanning friction factor one by minimizing a sum of squared differences between experimental and predicted data. The calculated temperature and pressure profiles present a good agreement with measurements. A statistical analysis shows that each optimized parameter is significant.