涡轮流量计前导流器的结构与性能

对DN100气体涡轮流量计的关键部件之一前导流器引起的流量计压力损失进行试验测量和数值计算.对比分析两种不同结构前导流器对压力损失的影响,发现前导流器的结构变化不仅影响该部位的气流速度分布,使当地压力损失发生变化,更重要的是对后面各部件内的气体流动速度梯度和压力恢复也有明显影响,使总压损失进一步放大或减小.数值计算通过分析流动参数的变化从流动机理上解释了结构与压损间的关系.     

气体涡轮流量计后导流体结构优化设计

通过数值模拟和实验测试相结合的方法,研究了LWQ80气体涡轮流量计后导流体的结构优化及其计量性能的变化规律。基于流量计内部流场特征及其流动机理的探究,分析得出造成后导流体压损的主要原因是后导流体区域的壁面边界层分离和流体流向偏转。由此提出了缩小分离区和提升导流片导流效果的优化思路,通过延长后导流体的长度和延后导流片的位置,设计了一种改进型的后导流体结构。研究结果表明：后导流体结构经过改进后,气体涡轮流量计的计量性能得到了明显提升。在流量为250 m~3/h时流量计的压损降低了20.5%左右,仪表系数的恒定性显著提高,最大示值误差降低了近2.5倍,且能有效延长流量计的使用寿命。研究结果有助于为气体涡轮流量计的结构与性能优化提供理论指导和技术支持。     

气体涡轮流量计性能优化的模拟与实验研究

以TRZ80气体涡轮流量计为研究对象,采用数值模拟与实验测试相结合的方法,提出了前整流器和后导流体的结构优化方案。通过对结构优化前后流量内部流场特征的分析,揭示了流量计结构与性能优化背后确切的流体力学机制。研究结果表明：前整流器和后导流体区域的压降突变与后导流体尾部的涡旋结构和回流现象是影响流量计计量性能的主要机制。优化的流量计结构可以明显减弱压降突变、涡旋结构与回流现象。优化的流量计结构既可以显著降低流量计的压力损失,又可以明显提高流量计的测量精度与稳定性,其压力损失和线性度误差分别降低了约48.58%和32.43%。研究结果有助于为今后开发与量产计量性能更好的气体涡轮流量计提供理论指导和技术支持。     

气体涡轮流量计结构优化研究

以TM80气体涡轮流量计为研究对象,采用数值模拟与实验测试相结合的方法对其进行结构优化研究。数值结果表明压力梯度骤变和边界层分离的出现主要由流量计的表芯支座和后导流体引起。由此提出了关于表芯支座坡度和后导流体直径的结构优化方法,将表芯支座的坡度设计为15°,将表芯支座侧面的台阶流转变成渐缩流;将后导流体直径缩减为62 mm,将后导流体侧面的台阶流转变成等直径的管道流。数值模拟和实验测试证实,当表芯支座坡度设计为15°、后导流体直径设计为62 mm时,流量计的压力损失显著降低,仪表系数变得更加稳定,线性度误差明显变小,说明该结构优化方法可以明显提升流量计的计量性能。研究结论有助于为今后开发性能更好的气体涡轮流量计提供有力的理论指导和技术支持。     

新型内外管差压流量计特性研究

针对现有各种流量计机械结构较复杂、节流方式对流体的扰动大、差压信号稳定性不足的缺点,设计了一种新型内外管差压流量计.运用三维CFD模拟仿真软件对其结构进行优化设计,通过实验验证了内外管差压流量计三维CFD仿真分析结果的可靠性.以内锥流量计作为参照对象,对内外管差压流量计的特性进行了对比分析,对比分析的结果表明,内外管差压流量计较内锥流量计压力损失小、压损比小、差压信号稳定性高.为了得到本装置的其他特性参数,又进行了大量的标定试验,实验结果表明测量精度、量程比等参数均满足技术标准的要求.     

关键因素对内锥流量计压损的影响

为提高对内锥流量计压力损失的认识,获得高准确度的压损计算公式,开展了关键因素对内锥流量计压损影响的实流实验研究。实验介质为常温水,雷诺数范围0.14×105～4.2×105。设计等效直径比分别为0.45、0.55、0.65、0.75、0.85的实验样机一套,从永久压损与相对压损2个角度进行分析。研究表明,一方面等效直径比相同而雷诺数不同时,内锥流量计的永久压损随雷诺数的增大而增大,在对数坐标系下成线性关系;雷诺数相同而等效直径比不同时,永久压损随等效直径比的增大而减小;另一方面,内锥流量计的相对压损与雷诺数无关,与等效直径比相关,随等效直径比的增大而减小。将本研究给出的内锥流量计相对压损计算公式与国外公式预测结果进行了比较,最大偏差为21%;同时,与国外测试的不同流量计相对压损曲线进行了比较,得出本套样机相对压损曲线介于孔板和喷嘴之间,且更靠近孔板的结论。     

车用催化器流场的数值模拟与结构优化设计

为了改善载体内速度分布,同时减小催化器内的压力损失,建立了基于一种新型导流装置的催化器内部流动的数学模型,并对其流场进行了二维稳态数值模拟。根据仿真结果,分析影响载体内流动特性的主要因素,为导流装置的改进确定方案。具体研究了导流装置结构参数d1:d2的改变对流动特性的影响,分析了速度分布和压力损失的变化规律,得出了一种较优的结构。加装导流装置后,流动在进入扩张管时提前分流,从而使载体前端流速分布更均匀,提高了载体的通过能力,减小了排气背压。     

压力位差式层流流量传感技术研究

层流流量计适用于气体小流量测量,但传统层流流量传感元件不可避免存在毛细管束进出口压损和毛细管层流起始段压损等非线性部分,导致输出差压不是流量的理想线性关系。基于此,提出了压力位差式层流流量传感技术,该项技术采用层流组件交叉对称的双流道结构,可以将毛细管束进出口局部损失和毛细管层流起始段非线性压力损失部分予以抵消,差压输出有更好的线性。分析了压力位差式层流传感技术原理和传感元件压降特性,设计了压力位差式层流流量传感元件实验模型,基于音速喷嘴气体流量标准装置进行实验测试,流量测量范围为0.015 8～6.350 1 m~3/h,在大于0.075 Q_(max)范围,流量测量误差小于±0.8%,小流量范围内测量误差在±3%以内。     

一种适用高压、低压损、宽量程的旋进旋涡技术

文章主要介绍了一种新式的高压力、低压损、宽量程的旋进旋涡技术。并针对扩宽量程范围、降低压力损失,适应高压。对旋进漩涡流量计的壳体、起旋器、文丘里管道、扩大管、压电晶体传感器及电路模块改进优化做了详细分析。对以上参数的改进优化。该产品是适应油田等特种工况使用。以下简要描述所适应的工况条件。     

导流器结构对气体涡轮流量计曲线影响的试验研究

本文针对于丹东东发集团有限公司开发的DN100气体涡轮流量计研发初期曲线不好的问题,从分析导流器的结构入手,通过试验证明导流器尾端的混合室的大小与曲线形状有着规律性的关系,确定了最佳的混合室尺寸,进而使得DN100气体涡轮流量计的性能曲线得到了优化。     

Pressure drop of wet gas flow with ultra-low liquid loading through DP meters

The most common method to predict the gas and liquid flow rates in a wet gas flow simultaneously is to use dual pressure drops (dual-DPs) from two or even one single DP meter. In this paper, the metering mechanism of applying dual-DPs were overviewed. To fully understand the response of DP meters to wet gas flows, the pressure drops of wet gas flow with ultra-low liquid loading through three typical DP meters were experimentally investigated, including an orifice plate meter, a cone meter and a Venturi meter. The equivalent diameter ratio is 0.45. The experimental fluids are air and tap water. The pressure is in the range of 0.1–0.3 MPa and the Lockhart-Martinelli parameter (X_LM) is less than approximately 0.02. The results show that the upstream-throat pressure drop, the downstream-throat pressure drop and the permanent pressure loss of individual DP meters have unique response to liquid loading. The upstream-throat pressure drop of the orifice plate meter decreases at first and then increases as the liquid loading increases, while that of the cone meter and the Venturi meter increase monotonically. The non-monotonicity of the pressure drop for the orifice plate meter can be attributed to the flow modulation of trace liquid. The downstream-throat pressure drops of all the three test sections decrease at first and then increase. The reason is that the liquid presence in a gas flow increases the downstream friction and vortex dissipation. The permanent pressure loss of the orifice plate meter also shows non-monotonicity. To avoid non-monotonicity, the pressure loss ratio is introduced, which is defined as the ratio of the permanent pressure loss to the upstream-throat pressure drop. Results show that the pressure loss ratio of the Venturi meter has the highest sensitivity to the liquid loading.     

Development of the T-ring vortex meter

A new type of vortex-shedding meter has been developed, in which the bluff body is in the form of an annular ring with a T-shaped cross-section. Because this is axi-symmetric it disturbs the flow much less than a transverse bluff body. This leads to a meter which is considerably more repeatable, and hence potentially more accurate, than a conventional vortex meter. It also has excellent linearity, and an exceptionally low pressure drop. The paper describes the design and performance as well as the current problems with development of a vortex detector.     

A comparative study of flow rate characteristics of an averaging Pitot tube type flow meter according to H parameters based on two kinds of differential pressure measured at the flow meter with varying air temperature

A new averaging Pitot tube flow meter that has a shape similar to an Annubar® type flow meter was designed and its flow rate characteristic was evaluated. The air temperature supplied to the developed flow meter was maintained at a constant by controlling electric power supply to an electric heater during the calibration. Two kinds of differential pressure measured at the flow meter were used in calculating the H parameters, which represent characteristics of the developed flow meter. One H parameter (H_ΔP1) which was newly proposed in this research was calculated based on the difference between upstream pressure (stagnation pressure) at the flow meter and static pressure of the measured flow. The differential pressure is equivalent to the dynamic pressure of the flow. The other H parameter (H_ΔP2) which is used in a typical Annubar® type flow meter was calculated based on the difference between upstream and downstream pressure at the developed flow meters. Relationship curves between the two H parameters and the mass flow rate at the developed flow meter were obtained. The curves based on the H_ΔP2 parameter, which uses the difference between up and down stream pressure, show different gradients for varying the controlled air temperature. However, the other curve, based on the other H_ΔP1 parameter, which uses the dynamic pressure, can be represented by one linear curve even with varying air temperature.     

Experimental investigation of an oscillating circular piston positive displacement flowmeter: I – Piston movement and pressure losses

Tests of an oscillating circular piston positive displacement flowmeter are described which focused on the effect on pressure drop across the meter of variation in key parameters. These included flow rate, liquid density and viscosity, mass of piston and length of connecting pipes. In addition to the average pressure loss, the pressure loss variation during the oscillation cycle was measured and found to vary with an amplitude dependent on the various parameters. A companion paper reviews data on leakage and wear.     

Design method for flow tube structure of electromagnetic water meter with shrunk measurement tube based on pressure loss-flow restriction

Due to the low flow rate measurement demand for battery-powered electromagnetic water meter, shrunk measurement tubes (such as circular section transition to square section) are often used to enhance flow velocity and measurement performance at small flow rate. However, this will also result in an increase in sensor pressure loss, even exceeding the pressure loss limit. Therefore, it is necessary to study a flow tube structure design method based on pressure loss-flow restriction, and design a flow tube structure which can not only maximize the induced voltage, but also meet the actual pressure loss requirement. Because there are many unknown variables in the formula of pressure loss mechanism, it cannot be directly used in structural design. Therefore, taking DN100 sensor as an example, based on finite element software, the variation of pressure loss with the length, width and height of rectangular section is obtained by orthogonal test method, and the numerical model of pressure loss is established. According to the requirements of industry and induced voltage enhancement, the optimal rectangular section size is found with the established pressure loss numerical model, and the structure of flow tube transition section is further optimized to reduce pressure loss. Finally, the prototype is made according to the optimized structure. Pressure loss experiment shows that the error between simulated value and measured value is within ±2.68% (±0.4 KPa). It means the pressure loss-flow restriction based design method for flow tube structure of electromagnetic water meter with shrunk measurement tube is effective and reliable.     

The smart-orifice meter: a mini head meter for volume flow measurement

Differential pressure based flow meters generally consist of a flow restriction element which generates a differential pressure and a pressure transducer, externally piped to the restriction, which measures the flow related differential pressure. The smart-orifice mini head meter presented takes advantage of silicon technology by incorporating a differential pressure microsensor. In contrast to conventional head meters, it represents a single compact and economic device for general flow meter applications, in particular where small size is of concern. Computational fluid dynamics analyses were applied to develop a non-standard orifice design and prototypes of the smart-orifice were fabricated. The performance of the mini head meter in water flow measurement was determined in a computer supported test bench facility. It was compared to the results predicted by the simulation, as well as to a conventional head meter arrangement with externally mounted pressure transducer, including measurements with water at elevated temperature and different absolute line pressures. The results are very promising and verify the competitiveness of the smart-orifice as a mini head meter.     

Experimental research of single-hole and multi-hole orifice gas flow meters

As energy efficiency is becoming more important today due to limited energy resources as well as their rising prices and environment issues, it is crucial to have reliable measurement data of different fluids in production processes. Because of its simplicity, affordability and reliability, orifice flow meters are again becoming subject of numerous researches. Conventional single-hole orifice (SHO) flow meter has many advantages but also some disadvantages like higher pressure drop, slower pressure recovery, lower discharge coefficient etc. Some of these disadvantages can be overcame by multi-hole orifice (MHO) flow meter while still maintaining advantages of conventional SHO meter. Both SHO and MHO flow meters with same β ratios were experimentally tested and compared. Results showed better (lower) singular pressure loss coefficient and lower pressure drop in favour of the MHO flow meter. Experimental data indicates that MHO flow meter is superior to the conventional orifice flow meter, but further research is necessary to make the MHO a drop-in replacement for a SHO flow meter.     

Optimization study on the isolator length of dual-mode scramjet

The dual-mode scramjet is a prime candidate for air-breathing propulsion engines given its broad speed range and high efficiency. The detailed structure of the pseudo-shock wave in the isolator is worth investigating. Therefore, the present study investigates the effect of isolator length on the pseudo-shock wave. We replicate the experimental work of the reference paper with a two-dimensional numerical model. Pressure distribution on the body surface is applied in the numerical validation. The numerical result is in good agreement with that of the existing experimental work. We simulate the thermal choking condition with a throttling device. As the throat area of throttling device decreases, the back pressure continues increasing and the pseudo-shock wave moves upstream. Avoiding unstart phenomenon is a key objective in the operation of dual-mode scramjet. Therefore, we investigate the critical condition shortly before unstart phenomenon occurs. The pseudo-shock wave structure is described by pressure distribution. Our main objective is to explore the effect of isolator length on the dual-mode scramjet. The optimal isolator length depends on the maximum back pressure and total pressure loss in the critical condition shortly before the unstart phenomenon occurs. The maximum back pressure in the critical condition is higher when the isolator length ranges from 8.7 to 20.7. The total pressure loss in the critical condition decreases at the beginning and then increases when the isolator length ranges from 8.7 to 20.7.

     

一种梭式流量计

本文提出了一种梭式流量计，用于测量井下或其它地下管道中的工质流量。流量计的外形象一把梭子，与被测管道内壁之间所形成的狭小通道构成了一种节流装置。通过在管内穿梭移动完成不同位置上的流量检测和记录，最后移出管外回放结果。在室内用单相水对这种流量计进行了实验研究。实验管道内径Ｄ＝３０ｍｍ，流量计外径ｄ＝２２．５ｍｍ，雷诺数Ｒｅ＝８×１０３～１×１０５。实验表明，这种梭式流量计的差压信号灵敏稳定，流量系数值介于标准孔板和文丘利管之间。     

Numerical simulations for multi-hole orifice flow meter

The measurement of flow rate is important in many industrial applications including rocket propellant stages. The orifice flow meter has the advantages of compact size and weight. However, the conventional single-hole orifice flow meter suffers from higher pressure drop due to lower discharge coefficient (Cd). This can be overcome by the use of multi-hole orifice flow meter. Flow characteristics of multi-hole orifice flow meters are determined both numerically and experimentally over a wide range of Reynolds numbers. Computational fluid dynamics (CFD) is used to simulate the flow in the single- and multi-hole orifice flow meters. Experiments are carried out to validate the CFD predictions. The discharge coefficients for the different orifice configurations are determined from the CFD simulations. It is observed that the pressure loss in the multi-hole orifice flow meter is significantly lower than that of single-hole orifice flow meter of identical flow area due to the early reattachment of flow in the case of the multi-hole orifice meter. The influence of different geometrical and flow parameters on discharge coefficient is also determined.