An investigation into the effects of installation on the performance of insertion flowmeters

An electromagnetic and a turbine insertion flowmeter were tested in three different flow conditions inside a 0.590-m bore pipe inserted in the National Engineering Laboratory (NEL) large water flow measurement facility. The results were compared with velocity measurements obtained from a laser Doppler velocimeter (LDV). The advantage of using such a reference measurement is that LDV is non-intrusive and does not affect the velocity profile itself.Of the meters tested, one was supplied with a whole meter calibration factor and the other was supplied with a calibration factor for the D/2 position.For both meters, application of the respective manufacturer's blockage correction improved the velocity measurements, reducing the differences between the LDV and corrected insertion meter measurements and the difference between the integrated insertion meter measurements and the gravimetric measurements.Swirling and skew flow profiles were generated by the installation of the NEL designed swirl generator and flow disturber, respectively. Neither of these disturbed profiles affected the performance of either of the meters in terms of accuracy of measurement compared with the LDV readings. The profiles themselves, however, changed the velocities at the D/8 and 7D/8 points, making single point estimates of the mean velocity inappropriate. A complete 13-point traverse, integrated using the method of cubics as described in BS 1042 [1] (Section 2.3: Measurement of fluid flow in closed conduits, 1992), gave acceptable estimates of mean velocity in both swirling and skew flow for both probes.     

动平衡机气体驱动研究

设计了一种动平衡机驱动装置,采用气体作为动力源驱动涡轮叶片转子,为测量提供稳定的转速,来确保动平衡测量的精度。阐明驱动原理和相应的结构,分析了流量与转速的关系,建立了流量与转速的数学模型,并对比分析了气体驱动与带圈驱动的转速波动和两种驱动在不同试重下不平衡量的误差。根据实验数据得出,在一定流量的范围内,气体驱动的转速波动更小;且在涡轮转子具有相同试重的情况下,气体驱动在一定范围内相较带圈驱动具有更高的测量精度。     

定桨距变转速风力机气动性能测试与流场测量

针对非并网风电系统,搭建了风力机性能测试平台,设计了流场测量系统。利用该平台和测试系统,通过改变磁粉制动器的励磁电流实现对风轮转速的高精度控制。通过测量分析发现了风轮后气流旋转方向与风轮旋转方向相反的规律,得到了输出功率越大,其尾迹内气流的轴向速度越小的结论。该实验结果为定桨距变转速风力机的转速控制策略制定提供了依据,也为非并网风电系统风力机的优化和设计提供了参考。     

核反应堆堆芯冷却剂流量测量用涡轮流量计的研制及应用

为适应核反应堆堆芯冷却剂流量测量的需要,开发研制了新型低速涡轮流量变送器,按流量信号输出不同,分别为磁感应模拟信号输出和数字开关量输出低速涡轮流量变送器。实际标定和应用表明,低速涡轮流量变送器的精度和重复性是好的,相对误差的均方根为1．0％,使用寿命长,阻力小,线性范围宽。     

发动机叶片电解加工夹具结构设计与密封性能分析

探讨了叶片全方位电解加工时,夹具的总体结构设计、电解液流道布局、夹具体防腐蚀、导电和绝缘等影响叶片成型精度的若干关键问题;分析了夹具的密封性能对电解液压力、流速和加工稳定性的影响;通过叶片加工试验验证了所设计夹具的精度和可靠性。试验结果表明所设计的夹具定位准确,能加工出符合精度要求的发动机叶片;夹具的密封性能得到极大改善,在相同的进口压力下,加工腔及流道内的压力损失急剧减小,出口压力提高。     

燃气轮机流动大涡模拟的进展与挑战（英文）

Gas turbine flows are complex and very difficult to be predicted accurately not only due to that they are inherently unsteady but also because the presence of many complex flow phenomena such as transition,separation,substantial secondary flow,combustion and so on.Those complex flow phenomena cannot be captured accurately by the traditional Reynolds-Averaged Navier-Stokes(RANS)and Unsteady RANS(URANS)methods although they have been the main numerical tools for computing gas turbine flows in the past decades due to their computational efficiency and reasonable accuracy.Therefore,the desire for greater accuracy has led to the development and application of high fidelity numerical simulation tools for gas turbine flows.Two such tools available are Direct Numerical Simulation(DNS)which captures directly all details of turbulent flow in space and time,and Large Eddy Simulation(LES)which computes large scale motions of turbulent flow directly in space and time while the small scale motions are modelled.DNS is computationally very expensive and even with the available most powerful supercomputers today or in the foreseeable future it is still prohibitive to apply DNS for gas turbine flows.LES is the most promising simulation tool which has already reasonably widely used for gas turbine flows.This paper will very briefly review first the applications of LES in turbomachinery flows and then focus on two gas turbine combustor related flow cases,summarizing the current status of LES applications in gas turbines and pointing out the challenges that we are facing.     

随钻测井用井下发电机系统的涡轮设计

对随钻测井系统中井下涡轮发电机的关键部件进行了研究.首先,建立了一种水力性能较高的涡轮模型;然后,基于计算流体力学(CFD)理论,采用Fluent软件对不同叶片参数的涡轮模型进行了紊流流场研究,并分析了流量、转速对涡轮流场的影响;最后,通过涡轮发电机地面单向水利实验验证了流量、转速、负载与涡轮发电机输出电压的关系.仿真结果表明:15叶片、叶片进口角30°以上、出口角45°以下、中弧线圆弧半径40mm以内对应的涡轮模型水力性能较好,但水力效率过高也会降低涡轮的工作寿命,因此,在一定范围内增大流量、转速对提高涡轮水力效率具有积极影响.所建立的涡轮模型能够提高涡轮的输出功率并保证其工作寿命.     

Effects of water in oil and oil in water on single-phase flowmeters

The effect of two-phase flow on the performance of a range of single-phase flowmeters has been investigated experimentally using the National Standard Multiphase Flow facilities at NEL. The flowmeters tested were 2-inch and 4-inch positive displacement meters, venturi meters, helicoidal and flat-bladed turbine meters, 2-inch U-tube, 3-inch and 1.5-inch straight tube Coriolis meters and a 4-inch vortex shedding meter. The flowmeters were tested in oil flow with water and water flow with oil. The second component fractions were varied from 3% up to 15% by volume. The aim of the project was to quantify the effect of second-phase fluid components on the basic uncertainty of a range of single-phase. These tests have provided evidence of the suitability of particular flowmeters for two-component flow applications. Comparisons have been made between generic type and size of flowmeter. The oil-in-water and water-in-oil tests indicated that the uncertainty in the outputs of the flowmeters tested were generally within ±1% relative to the reference flowrates, although some errors as high as 5–10% were also observed. Most of the measurements from the turbine flowmeters and the positive displacement flowmeters were within ±0.4% of the reference flowrates.     

Development of a turbine meter for two-phase flow measurement in vertical pipes

The performance of a turbine meter in two-phase (water/air) flow in a vertical pipe is assessed. If the single phase (water) meter factor is used in two-phase flow, the total (water and air) flowrate is found to be underpredicted. The error can be as much as 12.5% at a void fraction of 25%. A technique for using measurements of the fluctuations in the turbine meter rotor velocity to determine void fraction (= air flowrate/total flowrate) is described. A single meter is then used to measure, using this technique, both the water flowrate to an accuracy of ± 2% and void fraction to an accuracy of ±0.02.     

正压法气体流量标定系统的设计与实现

随着非标准流量仪表种类和数量的日益增加,为了保证仪表的测量精度。非标流量仪表的标定要求显得日益迫切。系统采用了国际标准文丘利作为标准表。应用标准流量计“比较法”原理,配合计算机程序控制,建立气体流量标定系统。进行流量计的检定和测试。依据有关的国家检定规程。该装置可对多孔孔板、V锥、楔形、巴类等差压式仪表以及涡轮、涡街、旋进旋涡等流量计进行检定、工业现场流量模拟实验以及风洞实验。通过运行实践证明,该系统测量精度高,稳定性好,标定流量范围宽。     

叶轮进口宽度对液力透平性能的影响

针对叶轮进口宽度对液力透平性能影响规律的认识不足问题,建设了一开式液力透平实验台,对一单级液力透平进行了实验研究,得到了该比转速液力透平的外特性曲线。采用结构化网格技术对液力透平进行了全流场数值计算与分析,数值与实验相结合,验证了数值计算的准确性。对不同进口宽度透平叶轮的数值计算结果分析表明,随着透平叶轮进口宽度的增加最高效率点向大流量偏移,大流量时的效率逐渐增加;对于一定几何参数组合的液力透平,存在最佳叶轮进口宽度使液力透平最优工况点效率最高;透平的流量扬程曲线随叶轮进口宽度的增加变得更加平坦;透平的轴功率变化相对较小。     

采用冷气射流调节对转涡轮高压部件流量的数值研究

针对先进发动机对涡轮变工况流量调节的需求,以某对转涡轮高压部件为研究对象,采用源项法模拟冷气射流,对导叶压力面、吸力面射流孔位置、射流角及射流流量对涡轮流量调节效果的影响进行了数值研究.结果表明:射流轨迹通过堵塞流道能实现减小涡轮进口流量的需求;从流量调节效果而言,不存在最佳压力面射流位置,而最佳吸力面射流位置位于喉道...     

不均匀来流作用下汽轮机动叶片的动态特性分析——非定常欧拉解法

通过三维欧拉非定常流场与弹性叶片动态响应的迭代计算,研究汽轮机叶片—流场系统的稳定性及其动态特性。对某一蒸汽轮机动叶片排,有一定的流量范围内,根据各自工况下静叶出口的不均匀流场,求得动叶片—流场系统的动态特性,判别其运行的稳定性范围。     

Evaluation of flowmeters for heat metering

Heat flowmeters are expected to be reasonably priced, be very reliable, and have high measurement accuracy. Various types of heat flowmeters have been developed and they are widely used in large residential and industrial buildings. In this study, three types of heat flowmeters (turbine, electromagnetic and ultrasonic) were tested for accuracy, effect of installation position and vibration, durability and performance in the field for several installation positions and in the presence of vibration. We used a liquid flow standard system and a customized durability test system in accordance with the International Organization of Legal Metrology (OIML) R 75-2 heat meter testing method. The field test was conducted in eight different locations from winter to summer. All flowmeters were calibrated before and after the field test, and the measurement deviation and the relative expanded uncertainty were calculated. The mean deviations obtained were–0.21%,–0.07%, and 0.11%, with the relative expanded uncertainties 0.48%, 0.17%, and 0.40% for turbine, electromagnetic, and ultrasonic flowmeters, respectively. The results of position and rotation tests, mean deviations by rotation angles at 90°, 180°and 270°relative to 0°(horizontal position) were–1.24%,–1.07% and–0.80%, respectively. For the vibration tests at 1 m/s² and 5 m/s² vibration acceleration, the turbine flowmeter, the electromagnetic flowmeter and the ultrasonic flowmeter showed deviations that ranged from −0.2% to −0.5%, −0.6% (2.6 m³/h), and 0.0% (negligible), respectively. In the durability tests, the accuracy of all three types of heat flowmeters remained at ±1% or less, showing sufficient durability. In the field test, the deviation of the turbine flowmeter and the ultrasonic flowmeter showed ±2.5% or less deviation. However, the electromagnetic flowmeter seems to be inaccurate below 6.9% of the maximum flow rate.     

磁轴承涡轮流量传感器的探讨

对不同结构的磁轴承涡轮流量传感器进行了比较综合,发现采用被动磁轴承结合机械约束,实现传感器内部可动部件叶轮的部分悬浮,是减小轴与轴承之间机械摩擦阻力、降低轴和轴承的磨损,从而提高传感器的灵敏度,增加传感器使用寿命的一条思路。提出了采用两个轴向磁化的径向磁轴承结合两个球头轴尖支撑的涡轮流量传感器结构,并进行了理论分析和参数计算。对研制磁轴承涡轮流量传感器过程中遇到的问题,进行了初步探讨。     

Performance studies on cavitation-resistance turbine flow sensor based on experiment and CFD simulation

Under the technical requirements of expanding measurement range and suppressing cavitation of flow sensors, the performance of a novel cavitation-resistance turbine flow sensor is taken as the research objective in this article. Based on theoretical analysis, a three-dimensional flow field CFD model of the turbine flow sensor with Realizable k-ε turbulence model and Schnerr&Sauer cavitation model is established. The cavitation tunnel experiment is performed to obtain the sensor characteristics. Finally, simulation and experiment results is analyzed and the feasibility of the CFD simulation of the sensor flow field is proved. The results show that this novel turbine flow sensor has the ability to resist cavitation, and the critical cavitation number σ_cr of the turbine flow sensor is below 0.4. Under a wide range of cavitation number (0.33~ σ ~1.6), Reynolds number(5 × 10⁴~ Re ~8 × 10⁵)and inflow angle α(−5°~ α~ 5°), the measurement meets the requirements.     

节流配汽超超临界汽轮机调门特性与经济运行

汽轮机主蒸汽流量是机组性能指标计算的关键参数之一,采用现有调门模型对其计算面临建模繁琐、模型复杂和计算过程参数难以获取等问题。针对有效面积变化的汽轮机高压调门,提出用椭圆公式对其建模,并用公开文献试验数据对其进行验证。结合阀门模型,以某660 MW节流配汽型超超临界汽轮机组为研究对象,对该机组进行变工况计算,研究不同负荷的不同运行策略下,高压缸效率和机组经济性的变化情况。结果表明,椭圆公式能够表现调门变工况特性,该方法建模过程简单,计算方便,在调门工作区域内计算精度高。机组高压缸效率随着高压调门开度的减小而减小,纯滑压运行方式下热耗率最低,但考虑到电网调频要求,建议机组变工况运行时调门开度控制在30%～45%为宜。所推荐的宽范围变工况运行策略在调门调节裕量满足电网调频的要求下,能够提高机组的经济性和深度调峰能力。研究结果可为同类型机组的运行优化策略提供参考。     

Analysis of viscosity effect on turbine flowmeter performance based on experiments and CFD simulations

Viscosity effect is one important factor that affects the performance of turbine flowmeter. The fluid dynamics mechanism of the viscosity effect on turbine flowmeter performance is still not fully understood. In this study, the curves of meter factor and linearity error of the turbine flowmeter changing with fluid viscosity variations were obtained from multi-viscosity experiments (the viscosity range covered is 1.0×10^–6 m²/s–112×10^–6 m²/s). The results indicate that the average meter factor of turbine flowmeter decreases with viscosity increases, while the linearity error increases. Furthermore, Computational Fluid Dynamics (CFD) simulation was carried out to analyze three-dimensional internal flow fields of turbine flowmeter. It was demonstrated that viscosity changes lead to changes of the wake flow behind the upstream flow conditioner blade and the flow velocity profile before fluid entering turbine rotor blade, which affect the distribution of pressure on the rotor blades, so impact the turbine flowmeter performance.     

Selecting the best ultralow-power turbine at the conceptual-design stage

A method is proposed for selecting the best ultralow-power turbine by means of structural and parametric optimization. The method is tested in the conceptual design of the turbine in the pneumatic starter of a diesel engine. The results are compared with optimization and numerical modeling of the flow in the turbine.     

Study of the nozzle flow in a cross-flow turbine

An investigation of the flow inside the nozzle of a Cross-Flow turbine, which is a hydraulic turbine where the rectangular water jet issuing from the nozzle crosses the rotor blades twice, is presented here. Part of the investigation consisted in the experimental measurement of the static pressure distribution on the inside walls of two different nozzle configurations, both with the nozzle mounted alone and in the presence of a rotor. The tests performed in the presence of a rotor included the measurement of efficiency and covered a wide range of working conditions around the best efficiency point. The analysis of the results obtained in this way give us an indication of the influence of the turbine non-dimensional volume flow rate on the flow inside the nozzle and the way it affects the reaction degree of the machine and its efficiency level. Although most of the tests were carried out with a 25-blade rotor, one of the analysed nozzle configurations (that with an inside vane) was also tested with a 10-blade rotor, permitting the assessment of the effect the number of blades has on the flow in the nozzle.The flow inside the nozzle with no inside vane was numerically analysed using a method based on a Schwarz-Christoffel conformal transformation of variables. The numerical results show a fair agreement with the experimental data collected when the rotor was not present. A qualitative discussion of some of the losses occurring in the nozzle is advanced based on the computer results, and its conclusions are used for explaining the poor performance of the nozzle with no inside vane.