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[管段编号][节点编号]节点流量(L/s)管长(m),管径(mm)Q1(1)(2)(3)(6)(10)(4)(5)(7)(8)(9)[1][2][5][9][6][7][8][4][3]600,4005.3716.11300,400450,300650,150250,100150,150230,200190,150205,10030.7411.267.527.074.103.887.16单定压节点树状管网水力分析某城市树状给水管网系统如图所示,节点(1)处为水厂清水池,向整个管网供水,管段[1]上设有泵站,其水力特性为:sp1=311.1(流量单位:m3/S,水头单位:m),he1=42.6,n=1.852。根据清水池高程设计,节点(1)水头为H1=7.80m,各节点流量、各管段长度与直径如图中所示,各节点地面标高见表,试进行水力分析,计算各管段流量与流速、各节点水头与自由水压。各节点地面标高节点编号(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)地面标高(m)9.8011.5011.8015.2017.4013.3012.8013.7012.5015.00解:第一步:逆推法求管段流量以定压节点(1)为树根,则从离树根较远的节点逆推到离树根较近的节点的顺序是:(10),(9),(8),(7),(6),(5),(4),(3),(2);或(9),(8),(7),(10),(6),(5),(4),(3),(2);或(5),(4),(10),(9),(8),(7),(6),(3),(2)等,按此逆推顺序求解各管段流量的过程见下表。逆推法求解管段流量步骤节点号节点流量连续性方程管段流量求解管段流量(L/s)1(10)-q9+Q10=0q9=Q10q9=11.262(9)-q8+Q9=0q8=Q9q8=4.103(8)-q7+q8+Q8=0q7=q8+Q8q7=11.174(7)-q6+q7+Q7=0q6=q7+Q7q6=18.695(6)-q5+q6+q9+Q6=0q5=q6+q9+Q6q5=60.696(5)-q4+Q5=0q4=Q5q4=3.887(4)-q3+q4+Q4=0q3=q4+Q4q3=11.048(3)-q2+q3+q5+Q3=0q2=q3+q5+Q3q2=87.849(2)-q1+q2+Q3=0q1=q2+Q3q1=93.21在求出管段流量后,利用最后一个节点(即定压节点)的流量连续性方程,可以求出定压节点流量,即:q1+Q1=0,所以,Q1=-q1=-93.21(L/s)根据管段流量计算结果,计算管段流速及压降见表。计算公式与算例如下:采用海曾威廉-公式计算(粗糙系数按旧铸铁管取Cw=100)管道摩阻系数管段水头损失泵站扬程按水力特性公式计算:管段流速及降压计算管段编号[1][2][3][4][5][6][7][8][9]管段长度(m)600300150250450230190205650管段直径(mm)400400150100300200150100150管段流量(L/s)93.2187.8411.043.8860.6918.6911.174.111.26管段流速(m/s)0.740.700.630.490.860.600.630.520.64管段摩阻系数109.7254.863256.0539093.49334.041229.924124.3332056.6614109.56水头损失(m)1.350.610.771.341.860.771.001.223.48泵站扬程(m)38.7600000000管段压降(m)-37.410.610.771.341.860.771.001.223.48第二步:求节点水头以定压节点(1)为树根,则从离树根较近的管段顺推到离树根较远的节点的顺序是:[1],[2],[3],[4],[5],[6],[7],[8],[9];或[1],[2],[3],[4],[5],[9],[6],[7],[8];或[1],[2],[5],[6],[7],[8],[9],[3],[4]等,按此顺推顺序求解各定流节点节点水头的过程见下表。顺推法求解节点水头步骤树枝管段号管段能量方程节点水头求解节点水头(m)1[1]H1-H2=h1H2=H1-h1H2=45.212[2]H2-H3=h2H3=H2-h2H3=44.603[3]H3-H4=h3H4=H3-h3H4=43.834[4]H4-H5=h4H5=H4-h4H5=42.495[5]H3-H6=h5H6=H3-h5H6=40.636[6]H6-H7=h6H7=H6-h6H7=39.867[7]H7-H8=h7H8=H7-h7H8=38.868[8]H8-H9=h8H9=H8-h8H9=37.649[9]H6-H10=h9H10=H6-h9H10=34.16最后计算各节点自由水压,见下表。节点自由水压计算节点编号i12345678910地面标高(m)9.8011.5011.8015.2017.4013.3012.8013.7012.5015.00节点水头(m)7.8045.2144.6043.8342.4940.6339.8638.8637.6434.16自由水头(m)—33.7132.8028.6325.0927.3327.0625.1625.1419.16为了便于使用,水力分析结果应标示在管网图上,如图所示[管段编号][节点编号]节点流量(L/s)管长(m),管径(mm)Q1(1)(2)(3)(6)(10)(4)(5)(7)(8)(9)[1][2][5][9][6][7][8][4][3]600,4005.3716.11300,400450,300650,150250,100150,150230,200190,150205,10030.7411.267.527.074.103.887.16单定压节点树状管网水力分析结果节点水头(m)自由水压(m)地面标高(m)9.807.80—45.2133.7111.5044.6032.8011.8043.8328.6315.2042.4925.0917.4040.6327.3313.3034.1619.1615.0039.8627.0612.8038.8625.1613.7037.6425.1412.50
本文标题:给排水管网系统作业
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