煤礦抽放瓦斯利用孔板流量計

煤礦抽放瓦斯利用孔板流量計計算抽放方法及參考系數(shù)孔板流量計由抽采瓦斯管路中增加的一個中心開孔的節(jié)流板、孔板兩側(cè)的垂直管段和取壓管等組成，如下圖。當氣體流經(jīng)管路內(nèi)的孔板時，流束將形成局部收縮，在全壓不變的條件下，收縮使流速增加、靜壓下降，在節(jié)流板前后便會產(chǎn)生靜壓差。在同一管路截面條件下，氣體的流量越大，產(chǎn)生的壓差也越大，因而可以通過測量壓差來確定氣體流量。瓦斯混合氣體流量由下式計算：TOC\o"1-5"\h\zQ=Kb^h1/28PST ⑴該公式系數(shù)計算如下：K=189.76a0mD2 (2)b=(1/(1-0.00446x))1/2 (3)3P=(PT/760)l/2 (4)3T=(293/(273+t))l/2 (5)式中：Q—瓦斯混合流量，米3/秒；K—孔板流量計系數(shù)，由實驗室確定見表-4實際孔板流量特性系數(shù)Kb—瓦斯?jié)舛刃Ｕ禂?shù)，由有關(guān)手冊查表-3瓦斯?jié)舛刃Ｕ禂?shù)b值表△h—孔板兩側(cè)的靜壓差，mmH20，由現(xiàn)場實際測定獲取；3P—壓力校正系數(shù)；ST—溫度校正系數(shù)；x--混合氣體中瓦斯?jié)舛龋?；t--同點溫度，°C；a0--標準孔板流量系數(shù)；(在相關(guān)手冊中查出)m--孔板截面與管道截面比；D--管道直徑，米；PT--孔板上風端測得的絕對壓力，毫米水銀柱；pT=測定當?shù)貧鈮?毫米水銀柱)+該點管內(nèi)正壓(正)或負壓(負)(毫米水柱)寧13.6為了計算方便，將ST、SP、b、K值分別列入表1、表2、表3、表4中。抽采的純瓦斯流量，采用下式計算：Qw=x?Q (6)式中x—抽采瓦斯管路中的實際瓦斯?jié)舛龋??？装辶髁坑嬙诎惭b時要注意孔板與瓦斯管的同心度，不能裝偏。在鉆場內(nèi)安裝流量計時，應(yīng)保證孔板前后各1m段應(yīng)平直，不要有閥門和變徑管。在抽采巷瓦斯管末端安裝流量計應(yīng)保證孔板前后各5m段應(yīng)平直，不要有閥門和變徑管。各礦井應(yīng)根據(jù)不同的管路條件和具體位置安設(shè)相應(yīng)的流量計，準確推敲計算公式，按規(guī)定定期維護校正，以便為瓦斯抽采提供可靠數(shù)據(jù)。例：某礦井瓦斯抽采支管直徑為D=100毫米，擬定安設(shè)開口直徑d=50毫米的孔板，試建立其流量方程式？解：m=(d/D)2=(0.05/0.1)2=0.25計算瓦斯流量特性系數(shù)值，應(yīng)用公式(2)得K=189.76a0mD2=189.76X0.6327X0.25X0.12=0.3001也可根據(jù)aO、m值查表4求得K值，根據(jù)瓦斯?jié)舛炔楸?可得瓦斯?jié)舛刃Ｕ禂?shù)b值。則應(yīng)用公式(1)可求得混合瓦斯流量為：

Q混=0.3001bAhl/23P3T應(yīng)用公式（6）計算純瓦斯流量得QW=Q混X=0.3001b^h1/28P8TX注：精度要求不高的計算，§P3T近似為1,公式（1）變?yōu)镼=KbAh1/2，本題Q混=0.3001bAh1/2QW=Q混X=0.3001bAh1/2x表-1溫度校正系數(shù)3T值溫度°C0123456789400.9680.9660.9640.9630.9610.9600.9580.9570.9550.954300.9830.9820.9800.9790.9770.9750.9740.9720.9710.696201.0000.9980.9970.9950.9930.9920.9900.9880.9870.985101.0171.0161.0141.0121.0101.0081.0071.0051.0031.00101.0351.0341.0331.0321.0291.0271.0251.0231.0211.019-01.0351.0371.0391.0411.0431.0451.0471.0491.0521.054-101.0561.0581.0591.0611.0631.0661.0681.0701.0721.074-201.0761.0781.0801.0831.0851.0861.0891.0911.0941.095-301.0981.0991.1031.1051.1081.1091.1121.1151.1171.119-401.1221.1231.1261.1291.1311.1331.1361.1391.1471.143表-2氣壓校正系數(shù)3p值壓力T（P毫3p壓力PT（毫米水3p壓力P3p壓PT(力毫3pT(毫米水銀柱）銀柱）米水銀柱）米水柱）銀1500.4443400.6695300.8357200.9731550.4523450.6745350.8397250.9771600.4583500.6785400.8437300.9801650.4663550.6835450.8477350.9841700.4723600.6895500.8507400.9871750.4803650.6935550.8547450.9901800.4883700.6985600.8587500.9931850.4933750.7025650.8627550.9971900.5003800.7075700.8667601.0001950.5063850.7125750.8707651.0032000.5133900.7165800.8747701.0062050.5193950.7205850.8787751.0092100.5254000.7245900.8817801.0132150.5324050.7295950.8867851.0162200.5384100.7346000.8897901.0192250.5444150.7396050.8927951.023

2300.5504200.7436100.8968001.0262350.5564250.7486150.9008051.0292400.5624300.7526200.9038101.0312450.5684350.7566250.9078151.0342500.5744400.7616300.9108201.0372550.5794450.7656350.9148251.0402600.5854500.7696400.9188301.0432650.5904550.7746450.9228351.0472700.5964600.7786500.9258401.0502750.6014650.7826550.9288451.0532800.6074700.7866600.9328501.0562850.6124750.7916650.9358551.0592900.6174800.7946700.9398601.0622950.6234850.7996750.9428651.0653000.6294900.8036800.9468701.0683050.6334950.8076850.9498751.0713100.6395000.8116900.9538801.0743150.6435050.8156950.9568851.0773200.6495100.8197000.9608901.0803250.6545150.8237050.9638951.0833300.6595200.8277100.9673350.6635250.8317150.970表-3瓦斯?jié)舛刃Ｕ禂?shù)b值表沼氣濃度X（%）012345678901.0001.0021.0041.0071.0091.0111.0141.0161.0191.021101.0241.0261.0281.0311.0321.0351.0381.0401.0431.045201.0481.0501.0531.0561.0581.0601.0631.0661.0681.071301.0741.0771.0801.0821.0851.0881.0911.0951.0971.100401.1031.1061.1091.1131.1161.1191.1221.1251.1281.131501.1341.1371.1411.1441.1481.1511.1541.1581.1621.164601.1681.1721.1761.1791.1821.1861.1901.1941.1981.202701.2061.2101.2141.2201.2221.2251.2291.2341