共查询到18条相似文献,搜索用时 156 毫秒
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正一、引言计量标准的不确定度是衡量计量检定/校准工作可靠性的重要指标,也是衡量被检器具溯源结果的主要依据。凝胶流量计标准装置采用凝胶水基模拟液作为工作介质,主要用于凝胶发动机用质量流量计(以下简称"凝胶流量计")的测试和量值传递。本装置是为了模拟凝胶流量计的实际使用工况,实现凝胶流量计的实流模拟校准建立的一套液体流量标准装置。为了确保流量测量的准确度, 相似文献
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天然气流量计量需要解决复杂工况下流量测量及大口径仪表量值溯源等计量基础问题。基于激光多普勒测速仪对天然气流量进行测量,将传统的流量体积量测量转化为管道截面的速度场测量,通过速度面积法实现了天然气流量的准确测量。研究表明:该方法可实现1. 45MPa、500m3/h的最大流量测量,系统扩展不确定度为1. 42%(k=2);实验结果与超声流量计标准表测得的标准流量相对偏差在-0. 81%~0. 09%范围;所获得的测量结果验证了光学法测量天然气流量的可行性,建立的实验系统可用于更宽广流量范围的高压天然气流量测量的研究。 相似文献
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研究了双柱塞计量缸的流量计校准装置,通过系统控制与计算实现计量缸计量流量与被校流量计测量流量的在线对比,以满足宽量程和高精度的校准要求.分析了该装置的结构特点和设计方法,通过仿真分析对其性能进行初步评估.研究了校准计量柱塞行程和移动速度对涡轮流量计仪表系数的影响,给出了建议的校准实验条件.结果表明,采用该校准装置可满足宽量程液体流量计校准,流量计量稳定性在0.2‰内. 相似文献
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气体流量是能源贸易结算、环境监测等诸多领域中的关键参数,其测量不确定度直接影响贸易公平和环境保护。气体流量基准装置是流量量值的源头,流量计是流量量值传递的载体。本项目自主研制了气体流量基准、标准装置,系统研究了流量计的计量性能,建立了完整的气体流量量值传递体系,显著提升了我国气体流量的计量水平。项目主要成果包括3个方面:将我国气体流量基准装置的测量不确定度水平提升了4倍,首次获得了国际气体流量领域的4项校准测量能力(CMC),测量结果获得国际互认,支撑主导中俄两国间的国际比对,保障能源国际贸易的开展。拓展了气体流量标准装置的测量能力,自主建立高压pVTt法气体流量原级标准装置、临界流音速喷嘴法次级标准装置和环道式涡轮流量计法工作标准装置,满足了高压气体流量量值溯源的迫切需求。综合采用理论、数值模拟及实验等不同研究方法对音速喷嘴流量计开展系统研究,成果显著提升了其测量结果可靠性,支撑相关国际标准的修订,极大提高了我国在该领域的国际学术地位。 相似文献
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Intra-arterial measurements of the velocity and the average flow of red-blood cells were investigated by means of a fiber-coupled laser Doppler velocimeter based on the self-mixing effect. The velocity of the red cells was calculated from the frequency of the signal that occurs when light, scattered back from a moving object in front of a fiber into a laser-diode cavity, interferes with the laser cavity's proper mode. These fluctuations occur at the Doppler frequency. The signal was obtained from the photodiode that is present in the laser diode's housing. Temperature control and stabilization of the diode cavity were introduced to reduce the light-intensity fluctuation that is due to mode hopping of the diode. The velocimeter was calibrated with a rotating disk covered with white paper (nonlinearity of 2.6% for velocities up to 0.4 m/s) and tested in vitro as a fluid velocimeter. The velocimeter was used in in vivo tests on the iliac artery of a 35-kg pig and on the arteria pulmonaris of a healthy calf. The optical fiber was placed in the iliac artery by a basket catheter 4 cm proximal to the bifurcation of the femoral artery. The average arterial blood flow velocity of the red cells were measured upstream and downstream. A special cleaving procedure for the fiber tip in downstream measurement is reported. Blood-velocity measurement is compared with values generated by an ultrasound flowmeter, and a difference of less than 9% is found. 相似文献
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大口径气体超声波流量计广泛应用于烟道排放监测和工业控制等领域。超声波流量计的传播时间测量准确度校准是非实流校准的重要环节,通过建立超声波流量计时间测量准确度校准装置,实现对大口径气体超声流量计传播时间的非实流校准。该文首先提出3种不同的超声流量计传播时间校准方法,分析不同方法的影响因素,其次通过改变探头间距离,对不同探头间距时超声波流量计传播时间的测量误差进行校准。试验结果表明:超声波流量计传播时间的测量误差随距离变化,并确定利用标准声速对超声波流量计传播时间进行修正的方法更为准确,测量结果不确定度为0.2%。 相似文献
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G. E. Mattingly 《Journal of research of the National Institute of Standards and Technology》1992,97(5):509-531
Critical measurement performance of fluid flowmeters requires proper and quantified verification data. These data should be generated using calibration and traceability techniques established for these verification purposes. In these calibration techniques, the calibration facility should be well-characterized and its components and performance properly traced to pertinent higher standards. The use of this calibrator to calibrate flowmeters should be appropriately established and the manner in which the calibrated flowmeter is used should be specified in accord with the conditions of the calibration.These three steps: 1) characterizing the calibration facility itself, 2) using the characterized facility to calibrate a flowmeter, and 3) using the calibrated flowmeter to make a measurement are described and the pertinent equations are given for an encoded-stroke, piston displacement-type calibrator and a pulsed output flowmeter. It is concluded that, given these equations and proper instrumentation of this type of calibrator, very high levels of performance can be attained and, in turn, these can be used to achieve high fluid flow rate measurement accuracy with pulsed output flowmeters. 相似文献
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Bubble sizing with high spatial resolution 总被引:1,自引:0,他引:1
Cathignol D Chapelon JY Newhouse VL Shankar PM 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1990,37(1):30-37
The authors propose a technique that allows them to size bubbles with the same accuracy as with the double-frequency method and to locate them with the same range resolution as with the pulsed Doppler velocimeter. They demonstrate that the signal scattered by the bubble insonified by a high-frequency pulsed ultrasonic field and a low-frequency pumping field is a low-frequency signal sampled at the repetition frequency rate and in which the amplitude is maximum when the bubble resonates. However using a conventional Doppler flowmeter, the maximum amplitude is not detectable when the repetition frequency is a multiple of the pump frequency. The modifications of the signal processing needed to overcome this drawback are discussed and implemented in the conventional Doppler flowmeter. Using this modified setup the lateral and the longitudinal range resolution are the same as in conventional Doppler flowmeters. The resonance frequency thus obtained is also compared to the resonance frequency measured by the double Doppler frequency method. Some practical improvements are proposed to make the system easy to use. Using this latest version, the resonant requencies for ten different bubble sizes are measured and compared. The case in which the nonlinearity effect (due to a bubble at resonance) generates out-of-phase upper and lower sidebands is discussed, and it is demonstrated that this effect is so feeble that it is negligible. 相似文献