带励磁二极管的交流发电机的建压转速

对调节器提出一个新的技术参数——调节器最低直流工作电压UDmin。通过对带励磁二极管的交流发电机的建压过程的定性分析,说明调节器最低直流工作电压UDmin对带励磁二极管的交流发电机的建压转速影响的机理,并通过大量试验证实了该影响。

基于黄金分割的异步发电机空载建压转速值的确定

从异步发电机稳态运行的等效电路模型出发,列写了等效电路模型的回路阻抗方程,令回路阻抗实部和虚部分别为零,建立方程组。在此基础上利用二维优化计算最小建压电容,然后利用基于黄金分割的一维优化方法计算最小建压转速值。此法编程简单,收敛速度快。论文最后通过实例计算验证了本方法的正确性和准确性。

汽车交流发电机的建压过程和建压转速

内置整流器和电压调节器的汽车交流发电机,其建压转速是一项重要的性能参数。较低的建压转速表征了汽车交流发电机在怠速状态运行时,亦会有良好的工作性能。本文从汽车交流发电机设计的角度出发,从建压过程说起,分析影响建压转速的各个因素,重点论述设计及制造中如何测量和降低建压转速,以满足产品达到整车配套的技术要求。

调压定转速法匹配风机盘管

由于风机盘管的整体性较强， 如果要提高它的整体性能， 保证机组的各项指标，那么风机、电机、盘管三者如何经济合理的匹配就是一个突出的问题了。本文提出一种新的匹配方法——调压定转速匹配法。此方法比较适合我国目前风机盘管的生产水平，它能有效地解决我国目前风机盘管行业存在的一些问题， 有助于提高产品的质量。

西藏安多县多才玛矿区强研磨性地层孕镶金刚石钻头使用效果分析

多才玛矿区位于三江源国家自然保护区内,任务量重、施工要求高、难度大,采用现场调研法和室内试验分析法分析孕镶金刚石钻头使用效果。通过研究分析得到:多才玛矿区岩石的研磨性为5~6级,可钻性为7~8级,地层破碎程度为Ⅲ~Ⅳ级。“NQ”系列孕镶金刚石钻头在多才玛矿区施工时的最优钻压在8~11MPa之间,最优转速在1.41~2.35m/s之间。通过激光扫描共聚焦显微镜观察分析两种典型的非正常钻进过程发现,在高转速、低钻压的条件下是新鲜的金刚石面无法出刃导致机械钻速低,在高转速、高钻压的条件下发生烧钻,胎体直接与岩体接触导致机械钻速低。孕镶金刚石钻头的金刚石平均出刃高度一定程度上可以反映钻头的寿命和机械钻速的大小。

Instantaneous rotation speed measurement and error analysis for variable speed hydraulic system

In order to monitor the working state of piston motor and measure its instantaneous rotation speed accurately, the measuring principle and method of instantaneous rotation speed based on industrial personal computer and data acquisition card are introduced, and the major error source, influence mechanism and processing method of data quantization error are dis- cussed. By means of hybrid programming approach of LabVIEW and MATLAB, the instantaneous rotation speed measurement system for the piston motor in variable speed hydraulic system is designed. The simulation and experimental results show that the designed instantaneous speed measurement system is feasible. Furthermore, the sampling frequency has an important influ- ence on the instantaneous rotation speed measurement of piston motor and higher sampling frequency can lower quantization er- ror and improve measurement accuracy.

美日汽车发电机性能指标解析

简明分析美日汽车发电机性能指标与我国行业标准的要求;从交流发电机设计的角度,分析影响主要性能指标的各项因素和调控规律。重点论述如何调整设计和制造工艺,使产品全面达到满足发动机和整车配套的技术要求。

最优化钻井技术在陕北石油钻井中的应用与推广

讨论了最优化钻井的基本理论；结合陕北石油钻井的实际情况，分析了陕北石油钻井施工中最优化钻并的设计程序，从钻井的井身结构、泥浆性能、水力参数、钻头类型、钻压和转速等方面进行了优化选择；给出了陕北石油钻井的最优化钻井模式；提出了今后陕北石油钻井发展的方向。

DF4B型内燃机车停机的原因分析与处理

文中对内燃机车提手柄泵风压转数停机的原因进行了分析。通过对机车走车、泵风压转数与调速器的动作关系,找出了故障原因,同时对该类故障的处理方法和预防措施提出了建议。

Strain rate-dependent high temperature compressive deformation characteristics of ultrafine-grained pure aluminum produced by ECAP

To explore the effect of strain rate ε on the high temperature deformation characteristics of ultrafine-grained materials, the deformation and damage features as well as microstructures of ECAP-treated pure Al at different temperatures T and strain ratesε were systematically studied through compression tests and microscopic observations. The increase in ε eliminates strain softening at T≤473 K, and largely enhances the yield strength and flow stress at 473?573 K. The shear deformation dominates the plastic deformation of ECAP-treated Al. Many cracks along shear bands (SBs) are formed at T≥473 K and secondary SBs basically disappear at 1×10?3 s?1; however, at 1×10?2 s?1, cracks are only observed at temperature below 473 K, and secondary SBs become clearer at T≥473 K. The microstructures of ECAP-treated Al mainly consist of sub-grains (SGs). The increase in ε inhibits the SG growth, thus leading to the increases both in yield strength and flow stress at high temperatures.

Wet Compression Performance of a Transonic Compressor Rotor at its Near Stall Point

In order to study the effects of wet compression on a transonic compressor,a full 3-D steady numerical simulation was carried out under varying conditions.Different injected water flow rates and droplet diameters were considered.The effect of wet compression on the shock,separated flow,pressure ratio,and efficiency was investigated.Additionally,the effect of wet compression on the tip clearance when the compressor runs in the near-stall and stall situations was emphasized.Analysis of the results shows that the range of stable operation is extended,and that the pressure ratio and inlet air flow rate are also increased at the near-stall point.In addition,it seems that there is an optimum size of the droplet diameter.

A new method for high precsion instantaneous speedmeasurement of hydraulic system

The instantaneous speed of a hydraulic system contains a wealth of operational information,and its accurate extraction is the basis for condition monitoring and fault diagnosis.In order to solve the problem of high hardware requirement for instantaneous speed measurement based on data acquisition card,a new method of high precision measurement is proposed.In this method,the time-displacement information of each tooth is obtained from the pulsed square wave signal of the gear disk collected by magnetoelectric sensors.The time-displacement curve is interpolated by the cubic spline interpolation method,and then the instantaneous speed is calculated by the five-point digital differential formula.The experimental results show that the method improves the speed measurement resolution and reduces the quantization error.The high precision instantaneous speed signal can also be acquired by hardware devices with less teeth and low sampling frequency.The related research results provide a theoretical basis and a method for improving the accuracy of instantaneous speed measurement.

Distribution characteristics and impact on pump＇s efficiency of hydro-mechanical losses of axial piston pump over wide operating ranges

A novel performance model of losses of pump was presented,which allows an explicit insight into the losses of various friction pairs of pump.The aim is to clarify that to what extent the hydro-mechanical losses affect efficiency,and to further gain an insight into the variation and distribution characteristics of hydro-mechanical losses over wide operating ranges.A good agreement is found in the comparisons between simulation and experimental results.At rated speed,the hydro-mechanical losses take a proportion ranging from 87% to 89% and from 68% to 97%,respectively,of the total power losses of pump working under 5 MPa pressure conditions,and 13% of full displacement conditions.Furthermore,within the variation of speed ranging from 48% to 100% of rated speed,and pressure ranging from 14% to 100% of rated pressure,the main sources of hydro-mechanical losses change to slipper swash plate pair and valve plate cylinder pair at low displacement conditions,from the piston cylinder pair and slipper swash plate pair at full displacement conditions.Besides,the hydro-mechanical losses in ball guide retainer pair are found to be almost independent of pressure.The derived conclusions clarify the main orientations of efforts to improve the efficiency performance of pump,and the proposed model can service for the design of pump with higher efficiency performance.

Aerodynamic performance of high-turning curved compressor cascade with boundary layer suction

The impact of boundary layer suction on the aerodynamic performance of a high-turning compressor cascade was numerically simulated and discussed.The aerodynamic performance of a curved and a straight cascade with and without boundary layer suction were comparatively studied at several suction flow rates.The results showed that boundary layer suction dramatically improved the flow behavior within the flow passage.Moreover,higher loading over the whole blade height,lower total pressure loss,and higher passage throughflow were achieved with a relatively small amount of boundary layer removal.The integration of curved blade and boundary layer suction contributed to better aerodynamic performance than the cascades with only curved blade or boundary layer suction used,and the more favorable effect resulted from the weakening of the three dimensional effects of the boundary layer close to the endwalls.

Statistical analysis of pressure fluctuations during unsteady flow for low-specific-speed centrifugal pumps

A three-dimensional transient numerical simulation was conducted to study the pressure fluctuations in low-specific-speed centrifugal pumps. The characteristics of the inner flow were investigated using the SST k-ω turbulence model. The distributions of pressure fluctuations in the impeller and the volute were recorded, and the pressure fluctuation intensity was analyzed comprehensively, at the design condition, using statistical methods. The results show that the pressure fluctuation intensity increases along the impeller streamline from the leading edge to the trailing edge. In the impeller passage, the intensity near the shroud is much higher than that near the hub at thc inlet. However, the intensity at the middle passage is almost equal to the intensity at the outlet. The pressure fluctuation intensity is the highest at the trailing edge on the pressure side and near the tongue because of the rotor-stator interaction. The distribution of pressure fluctuation intensity is symmetrical in the axial cross sections of the volute channel. However, this intensity decreases with increasing radial distance. Hence, the pressure fluctuation intensity can be reduced by modifying the geometry of the leading edge in the impeller and the tongue in the volute.

Mass Transfer and Reaction Kinetics in the Carbonization of Magnesium Oxide from Light Calcined Magnesia with Mechanical Force Enhancement

The carbonization of magnesium oxide particles by CO2 was investigated using a stirring mill reactor. The effects of the system temperature, stirring rotation speed, influx rate of CO2 and initial diameter of the magnesium oxide particles on the carbonization process were determined, The results show that the system temperature and the stirring rotation speed are the most significant influencing factors on the carbonization rate. The determi-nation of critical decomposition temperature (CDT) gives the maximum carbonization rate with other conditions fixed. A theoretical model involving mass transfer and reaction kinetics was presented for the carbonization process. The apparent activation energy was calculated to be 32.8kJ·mol-1. The carbonization process is co-controlled by diffusive mass transfer and chemical reaction. The model fits well with the experimental results.

Hydraulic cylinder control of injection molding machine based on differential evolution fractional order PID

Injection molding machine,hydraulic elevator,speed actuators belong to variable speed pump control cylinder system.Because variable speed pump control cylinder system is a nonlinear hydraulic system,it has some problems such as response lag and poor steady-state accuracy.To solve these problems,for the hydraulic cylinder of injection molding machine driven by the servo motor,a fractional order proportion-integration-diferentiation(FOPID)control strategy is proposed to realize the speed tracking control.Combined with the adaptive differential evolution algorithm,FOPID control strategy is used to determine the parameters of controller on line based on the test on the servo-motor-driven gear-pump-controlled hydraulic cylinder injection molding machine.Then the slef-adaptive differential evolution fractional order PID controller(SADE-FOPID)model of variable speed pump-controlled hydraulic cylinder is established in the test system with simulated loading.The simulation results show that compared with the classical PID control,the FOPID has better steady-state accuracy and fast response when the control parameters are optimized by the adaptive differential evolution algorithm.Experimental results show that SADE-FOPID control strategy is effective and feasible,and has good anti-load disturbance performance.

Hydrodynamic Behavior in a Rotating Zigzag Bed

As a high gravity(HIGEE)unit,the rotating packed bed(RPB)uses centrifugal force to intensify mass transfer.Zigzag rotating bed(RZB)is a new type of HIGEE unit.The rotor of RZB consists of stationary discs and rotating discs,forming zigzag channels for liquid-gas flow and mass transfer.As in RPBs,some hydrodynamic behavior in RZB is interesting but no satisfactory explanation.In this study,the experiments were carried on in a RZB unit with a rotor of 600 mm in diameter using air-water system.The gas pressure drop and power consumption were measured with two types of rotating baffle for RZB rotors,one with perforations and another with shutter openings. The circumferential velocities of gas were measured with a five-hole Pitot probe.The pressure drop decreased rapidly when the liquid was introduced to the rotor,because the circumferential velocity of the liquid droplets was lower than that of the gas,reducing the circumferential velocity of gas and the centrifugal pressure drop.The power consumption decreased first when the gas entered the RZB rotor,because the gas with higher circumferential velocity facilitates the rotation of baffles.

Effects of groove on behavior of flow between hydro-viscous drive plates

The flow between a grooved and a flat plate was presented to investigate the effects of groove on the behavior of hydro-viscous drive. The flow was solved by using computational fluid dynamics (CFD) code, Fluent. Parameters related to the flow, such as velocity, pressure, temperature, axial force and viscous torque, are obtained. The results show that pressure at the upstream notch is negative, pressure at the downstream notch is positive and pressure along the film thickness is almost the same. Dynamic pressure peak decreases as groove depth or groove number increases, but increases as output rotary speed increases. Consequently, the groove depth is suggested to be around 0.4 mm. Both the groove itself and groove parameters (i.e. groove depth, groove number) have little effect on the flow temperature. Circumferential pressure gradient induced by the groove weakens the viscous torque on the grooved plate (driven plate) greatly. It has little change as the groove depth increases. However, it decreases dramatically as the groove number increases. The experiment results show that the trend of experimental temperature and pressure are the same with numerical results. And the output rotary speed also has relationship with input flow rate and flow temperature.

Numerical Simulation on a Throttle Governing System with Hydraulic Butterfly Valves in a Marine Environment

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.