發(fā)布時(shí)間：2018-03-07 10:04

  本文選題：U型超聲波熱量表　切入點(diǎn)：k系數(shù)　出處：《山東大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：為應(yīng)對(duì)能源短缺和環(huán)境污染問(wèn)題,除了開發(fā)新能源外還有一項(xiàng)有力措施就是節(jié)能減排,供暖作為耗能和環(huán)境污染的大戶,實(shí)行供熱分戶計(jì)量可以有效的改善現(xiàn)有按平方收費(fèi)的弊端。推行供暖分戶計(jì)量首先要有性能優(yōu)良的熱量表,本文針對(duì)影響超聲波熱量表測(cè)量精度的幾個(gè)問(wèn)題進(jìn)行了研究,并提出相應(yīng)的優(yōu)化意見。 現(xiàn)在超聲波熱量表流量部分的測(cè)量精度是熱量表研制的關(guān)鍵點(diǎn)也是難點(diǎn),影響熱量表流量部分測(cè)量精度原因有三個(gè)方面：一是熱量表電路對(duì)流量測(cè)量信號(hào)的采集；二是熱量表基表內(nèi)水流分布；三是超聲波熱量表檢測(cè)裝置的可靠性。本文采用理論分析和數(shù)值模擬相結(jié)合的方法從這三個(gè)方面對(duì)U型超聲波熱量表基表進(jìn)行了非定常數(shù)值模擬并對(duì)影響其測(cè)量精度的幾個(gè)問(wèn)題進(jìn)行分析,并用實(shí)驗(yàn)驗(yàn)證了所選的數(shù)值模擬方法的正確性。 在測(cè)量原理方面,考慮到熱量表工作環(huán)境溫度變化范圍較大,通過(guò)引進(jìn)相關(guān)修正公式,減小了溫度對(duì)流體粘度和超聲波在流體中傳播速度的影響,從而提高信號(hào)采集的準(zhǔn)確度和流量修正系數(shù)選擇的合理性�；斫Y(jié)構(gòu)方面,利用軟件FLUENT對(duì)戶用DN25型超聲波熱量表基表采用RNGk-ε模型進(jìn)行數(shù)值模擬計(jì)算,根據(jù)模擬計(jì)算結(jié)果分析超聲波熱量表基表內(nèi)線面速度關(guān)系及流場(chǎng)狀況。為減小反射裝置對(duì)基表內(nèi)流場(chǎng)的擾動(dòng),針對(duì)流場(chǎng)質(zhì)量差、壓損偏大的基表,可以通過(guò)加裝整流片進(jìn)行優(yōu)化,加裝整流片后反射裝置中心面上的漩渦減小,基表內(nèi)流場(chǎng)變得均勻,不同流量點(diǎn)下的壓損均有減小。檢測(cè)裝置方面,為提高熱量表的檢測(cè)生產(chǎn)效率,以實(shí)驗(yàn)測(cè)量誤差和k系數(shù)為評(píng)價(jià)依據(jù),發(fā)現(xiàn)超聲波熱量表檢測(cè)裝置試驗(yàn)段的彎管及變截面管段對(duì)測(cè)試管段表位一的熱量表測(cè)量精度影響很大,在彎管處加裝導(dǎo)流片后可以明顯消除彎管二次流,提高測(cè)量精度。在熱量表入口安裝過(guò)濾網(wǎng),可以減小變截面管道對(duì)表位一熱量表測(cè)量誤差的影響。 另外,本文通過(guò)非定常數(shù)值模擬方法,研究了超聲波熱量表管道閥門開啟后流量增大過(guò)程中熱量表基表內(nèi)水流狀態(tài),并與穩(wěn)定流量下的熱量表進(jìn)行對(duì)比,分析了閥門開啟過(guò)程中水流狀態(tài)的變化對(duì)k系數(shù)和基表內(nèi)部流場(chǎng)的影響,對(duì)提高不同工作狀態(tài)下超聲波熱量表的測(cè)量精度提供了理論依據(jù)。 本文研究方法正確,并配有大量的實(shí)驗(yàn)及模擬數(shù)據(jù)和分析圖表,結(jié)果分析清晰正確,對(duì)研究超聲波熱量表流量部分測(cè)量精度和提高熱量表檢測(cè)裝置的可靠性及檢測(cè)效率,具有一定的指導(dǎo)意義和理論價(jià)值。
[Abstract]:In order to deal with the problems of energy shortage and environmental pollution, in addition to the development of new energy sources, there is also a powerful measure to save energy and reduce emissions. Heating, as a major user of energy consumption and environmental pollution, Household heating metering can effectively improve the existing shortcomings of square charge. In order to carry out household heating metering, it is necessary to have a heat meter with good performance. In this paper, several problems affecting the measurement accuracy of ultrasonic heat meter are studied. And put forward the corresponding optimization advice. At present, the measurement accuracy of the flow part of the ultrasonic heat meter is the key point and the difficulty in the development of the heat meter. There are three reasons that affect the measurement accuracy of the heat meter flow part: the first is the acquisition of the flow measurement signal by the heat meter circuit; Second, the distribution of water flow in the heat meter; The third is the reliability of ultrasonic calorimeter. The unsteady numerical simulation of U-type ultrasonic calorimeter is carried out from these three aspects by the combination of theoretical analysis and numerical simulation. Several problems of accuracy are analyzed. The correctness of the numerical simulation method is verified by experiments. In terms of measurement principle, considering the large range of temperature variation in the working environment of the heat meter, the influence of temperature on the viscosity of the fluid and the velocity of ultrasonic wave propagation in the fluid is reduced by introducing the relevant correction formula. In order to improve the accuracy of signal acquisition and the reasonableness of the choice of flow correction coefficient, the software FLUENT is used to simulate and calculate the DN25 type ultrasonic calorimeter with RNGk- 蔚 model. Based on the results of simulation, the velocity relationship and flow field status of ultrasonic heat meter are analyzed. In order to reduce the disturbance of flow field in the base table by the reflector, the base table with poor flow field mass and large pressure loss is used to reduce the disturbance of the flow field in the base table. It can be optimized by adding rectifier. After the rectifier is installed, the vortex on the center surface of the reflector is reduced, the flow field in the base table becomes uniform, and the pressure loss at different flow points is reduced. In order to improve the efficiency of measuring heat meter, based on the error and k coefficient of experimental measurement, it is found that the bend pipe and variable section pipe section of the test section of ultrasonic heat meter test device have great influence on the measuring accuracy of the heat meter. The secondary flow can be eliminated obviously and the measurement accuracy can be improved by installing the guide plate at the bend. The influence of the variable section pipeline on the measurement error of the surface-heat meter can be reduced by installing a filter net at the entrance of the heat meter. In addition, by using unsteady numerical simulation method, the flow state in the heat meter is studied in the process of increasing the flow rate after the valve of the ultrasonic heat meter is opened, and compared with the heat meter under the steady flow rate. The influence of the change of the flow state on the k coefficient and the internal flow field of the base meter during the valve opening is analyzed, which provides a theoretical basis for improving the measuring accuracy of the ultrasonic heat meter under different working conditions. The research method of this paper is correct, with a large number of experimental and simulation data and analysis charts, the results are clear and correct. It can improve the reliability and efficiency of the measuring device for the ultrasonic heat meter. It has certain guiding significance and theoretical value.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TK31;TB559

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