【作者】 齐利晓；

【导师】 张涛；

【作者基本信息】 天津大学 ， 检测技术与自动化装置， 2010， 博士

【摘要】 均速管流量传感器具有压损小,结构简单,可靠性高等诸多优点,被广泛应用于冶金、石油、化工等行业中。但是,自从均速管流量传感器问世以来,其测量性能就一直受截面形状及前后直管段影响,因此,本文通过CFD仿真与实流实验相结合的方法,对均速管截面形状进行优化设计,以提高其测量精度和对不同流场的适应能力。本文主要完成以下工作:提出了整流翼型均速管流量传感器检测杆截面形状。计算流体力学(CFD)仿真与理论分析相结合,从流场发展机理角度对以下问题进行了详细研究。截面形状对均速管总压、静压的影响;阻塞比与均速管仪表系数的关系;分离角大小、分离点位置与均速管线性度的关系;尾迹区大小与均速管重复性的关系。研究表明:与圆形、菱形、子弹头形等形状相比,由于整流翼的整流作用,整流翼型均速管检测杆后方的流体漩涡尺度变大、频率变低、中心位置离静压孔更远,对静压的影响变小,输出差压信号稳定性增强,提高了均速管流量计的线性度和测量重复性;同样由于整流翼的阻塞比及阻塞比变化率作用,流体在流过均速管时,平均流速增大,静压降低,从而提高了输出差压。在直管段长度不足,流体流动不稳定、速度分布紊乱的情况下,整流翼的整流作用明显,可以保证较高的测量精度。通过CFD仿真,对整流翼型均速管及圆形、菱形、子弹头形截面均速管测量性能进行的定量分析表明:DN50口径整流翼Ⅱ型、Ⅲ型均速管的线性度分别为0.45%和1.54%,优于圆形、菱形、子弹头形截面均速管。流场发展机理及性能定量分析均表明,整流翼型均速管具有更好的性能。均速管流量传感器二维CFD仿真方法研究。以均速管工作原理、取压孔位置选取方法等理论为基础,通过分析及计算,研究了将均速管流量测量系统三维流场简化为二维流场方法,得到5种二维模型。理论分析表明,过平均流速点的二维简化模型最具代表性,能够反映均速管内部及其所在管道流场特点。采用这5种模型对菱形均速管进行仿真与实验对比研究,发现过平均流速点的管道截面二维仿真,所得差压与实验结果的误差优于其它4种模型。通过理论分析及仿真与实验对比,找到了均速管仿真过程中,将三维模型简化为二维模型的最优方法。在保证CFD仿真精度的前提下,简化了研究过程,提高了研究效率,节约了研究成本。整流翼型均速管流量传感器测量性能实验研究。对DN50、DN200口径整流翼Ⅱ型均速管的测量性能进行了实验研究,并与目前流行的圆形、菱形、Delta形均速管进行了对比。结果表明:整流翼型均速管测量性能明显优于其它截面形状的均速管。从实验角度验证了整流翼的设计达到了理论与仿真分析的整流作用,提高了均速管的测量性能。整流翼型均速管流量传感器安装影响实验研究与流场分析。实验研究了圆形、菱形、整流翼型截面均速管,在90°弯头下游不同安装方式(与弯头垂直、与弯头在同一平面)及不同前直管段长度等情况下的测量性能。实验结果表明:由于整流翼的整流作用,相同安装条件下,整流翼型均速管对弯头下游紊乱流场的适应能力优于圆形、菱形截面均速管;相同均速管在垂直于弯头平面安装时测量性能优于与弯头在同一平面内安装。通过流场仿真,研究了弯头后均速管流场变化特点,从流场变化特点角度揭示了均速管在不同安装方式下性能不同的原因。更多还原

【Abstract】 Averaging Pitot tube(APT) is a kind of sampling flowmeter with advantages of low pressure loss, simple construction and good reliability. It is widely used in petroleum, metallurgy, chemical industry, light industry, food industry and other flow industry. But its performances are usually influenced seriously by its cross-section and the harsh industry field conditions. So, the paper deals with the APT’s cross-section optimization to improve its performances.The main researches of the dissertation are as the following:Three kinds of APT with flow conditioning wing(APTFCW) are designed. Through numerical computation and theoretic analysis,the following problems are discussed: the influence of the APT cross-section to the total pressure and static pressure; the relation between the blockage ratio and the coefficient; the relation of the separating angle, the separating position and the linearity of the APT; the relation between the wake region and the repeatability of the APT. Research shows that the scale of the swirl, after the APTFCW, is larger than that of the other cross-section APTs, and its frequency is lower, the distance between its center and the static pressure hole is larger. So, the swirl’s influence to the static pressure is lower and the output difference pressure is more stable. The linearity and repeatability of the APTFCW are better than those of the other cross-section APTs. The fluid velocity is larger than that of other cross-section APT when it flows through the APT, so the static pressure is lower and its difference pressure is larger. At the conditions of straight pipe not enough, the effect of the flow conditioning wing are obvious. So, its accuracy is better than other cross-section APTs. Through numerical computation, the performances of APTs in DN50 pipe are reasearched in quantitative. The linearity of the APTFCWⅡandⅢare 0.45% and 1.54% respectively, better than that of the others. The qualitative and quantitative researches show that the performances of the APTFCWⅡandⅢare better than the others.The method how to simplize three-dimensional entity into two-dimensional model in CFD is researched. Through theoretical anlysis, five two-dimensional models are acquired. Theoretical analysis shows that the model at the position of averaging velocity(MPAV) is the most representative. It could reflect the flow field characters. Numerical computation is done using the five models. It shows that the deviation between the data of numerical computation using the MPAV and the experiment data is least. Thtrough theoretical analysis and numerical computation, the optimal two-dimensional numerical computation model is accquired.Based on numerical computation, the APTFCWⅡ, circle and dianmond cross-section APT are chosed to process prototype of DN50 and DN200. Then, the prototypes are tested in gas flow standard facilities. Experimental researches indicate that the perfoemances of the APTFCW are better than the others. Through experiment, it’s proved that the flow conditioning wing works better.Experiments are done to test the performances of the APT when they are installed after the 90°elbow in different type(vertical to the elbow or in the same plane with the elbow) and in different straight pipe length(2D, 4D, 7D, 12D) before the APT. The performances and the adaptability of the three kinds of cross-section APTs are acquired in those conditions. It shows that at the same conditions, the adaptability of the APTFCW is better than the others, because of the effect of the flow conditioning wing. The performances, when the APTFCW are installed vertical to the elbow, are better than those when they are installed in the same plane with the elbow. Through numerical computation, the flow field characters after the 90°elbow is reasearched. The reason why the performances are different when the APT is installed in different type is explained from the point of flow field changing.更多还原