流體流動阻力的測的定

1、流體流動阻力的測定、實驗?zāi)康牧私鉁y定流體流經(jīng)直和管件時的阻力損失的實驗組織方法及測定摩擦系數(shù)的工程意義；學(xué)會用因次分析法解決工程實際問題；學(xué)會壓差計、流量計的使用方法以及了解管路中各個管件、閥門的作用。二、實驗原理由于流體粘性的存在，流體在流動過程中會產(chǎn)生流體間的摩擦，從而導(dǎo)致阻力損失。層流時的阻力損失的計算式是由理論推導(dǎo)得到的;湍流時由于情況復(fù)雜得多，未能得出理論式,但可以通過實驗研究，獲得經(jīng)驗的計算式。p-d2即入二f（二三）典d2、因次分析法規(guī)劃實驗各種管件或閥門處都會產(chǎn)生局部阻力損失。局部阻力損失的計算有兩種近似的方法：阻力系數(shù)法及當(dāng)量長度法。阻力系數(shù)法近似認(rèn)為流體通過某一管件或閥門的

2、局部阻力損失服從平方定律，用流體在管路中的動能系數(shù)來表示，即三、實驗流程圖實驗裝置如圖3-1,壓差的測量采用壓差傳感器或U型壓差計，流量的測量采用渦輪流量計。直管兩測壓點之間的距離為3m,光滑管內(nèi)徑為28mm，粗糙管內(nèi)徑為26.6mm，局部阻力管段內(nèi)徑為32mm。圖3-1四、實驗內(nèi)容測定流體在不同材質(zhì)和丁的直管中流動時的阻力摩擦系數(shù)入，在雙對數(shù)坐d標(biāo)紙繪出入和Re之間的關(guān)系；測定流體通過閥門或90彎頭時的局部阻力系數(shù)。五、實驗步驟關(guān)閉控制閥，打開光滑管管路上2個壓差變送器的平衡閥，打開光滑管引壓閥、光滑管切換閥、彎頭引壓閥，關(guān)閉其它所有閥，打開引水閥，灌泵，放氣，然后關(guān)閉。啟動泵，系統(tǒng)排氣?？?/p>

3、管排氣：先將控制閥開至最大然后再關(guān)閉，重復(fù)三次，目的為了使總管中的大部分氣體被排走，然后打開總管排氣閥，開至最大后再關(guān)閉，重復(fù)三遍。引壓管排氣：依次對4個放氣閥進(jìn)行排氣，將閥門開、關(guān)重復(fù)三次。壓差計排氣：關(guān)閉2個平衡閥，重復(fù)上述(2)步驟。將控制閥開至最大，讀取流量顯示儀讀數(shù)Qmax，然后關(guān)至壓差顯示值約為0.2Kpa0.3Kpa時，再讀取流量顯示儀讀數(shù)Qmin，在Qmin和Qmax二個讀數(shù)之間布15個點，讀取數(shù)據(jù)。關(guān)閉光滑管切換閥。打開粗糙管管路上2個壓差變送器的平衡閥，打開粗糙管引壓閥、粗糙管切換閥、閥門引壓閥。粗糙管系統(tǒng)排氣步驟同2的(2)、(3)。粗糙管系統(tǒng)流動阻力的測定同光滑管，重復(fù)

4、步驟3。實驗結(jié)束后，關(guān)閉控制閥。六、實驗原始數(shù)據(jù)記錄及處理1一次性原始數(shù)據(jù)記錄l=2m，d=21mm，dB=32mm，T=26.80CP水=994.79kg/m3局卩=76.3078*13Pa/S如果試驗中溫度變化，相應(yīng)參數(shù)應(yīng)有體現(xiàn)2實驗數(shù)據(jù)記錄及處理表光滑管（彎頭）實驗原始數(shù)據(jù)實驗次數(shù)流量L/S光滑管壓差KPa彎頭壓差KPa溫度C1(max)3.1017.536.2026.82(min)0.240.240.0432.932.8815.485.3732.942.6413.214.5032.952.4011.223.7933.062.239.853.3133.072.028.222.7133.1

5、81.847.052.3133.191.655.781.8532.9101.394.251.3532.9111.233.531.0933.0120.992.450.7233.0130.781.600.4533.0140.540.860.2433.0150.350.440.1133.0160.280.330.0733.2平均溫度。C32.6給出公式，及使用參數(shù)流速二流量/（nd2/4）Re二阻力系數(shù)入=Re二阻力系數(shù)入=pAlu2阻力J/Kg=P局部阻力J/CP水=994.79kg/m3口=75.854*10-Pa/S光滑管（彎頭）實驗數(shù)據(jù)處理實驗次數(shù)流速m/sRe阻力J/Kg阻力系數(shù)入局部阻力

6、J/K阻力系數(shù)Z1(max)5.0346184875.5617.62180.01306.232471170.49176粗糙管（閘閥）實驗原始數(shù)據(jù)實驗次數(shù)流量L/S粗糙管壓差KPa閘閥壓差KPa溫度。C1(max)2.5184.241.9533.52(min)0.050.250.0334.132.4084.361.8133.842.2276.321.5534.052.0162.741.2834.161.8352.121.0834.171.5838.820.8434.281.4231.920.6934.2101112131415164.67734.28763.89783.62173.28062.9

7、8832.67972.25751.99761.60781.26680.87700.56840.45470.38985171755.363157442.416143129.469132991.132120467.303109732.59398401.510282895.817773353.853159040.906146517.077632204.130620873.047616698.438114312.946915.561113.279211.27889.90168.26317.08695.81034.27233.54852.46281.60840.86450.44230.33170.241

8、30.01330.01350.01390.01410.01430.0148101112131415164.67734.28763.89783.62173.28062.98832.67972.25751.99761.60781.26680.87700.56840.45470.38985171755.363157442.416143129.469132991.132120467.303109732.59398401.510282895.817773353.853159040.906146517.077632204.130620873.047616698.438114312.946915.56111

9、3.279211.27889.90168.26317.08695.81034.27233.54852.46281.60840.86450.44230.33170.24130.01330.01350.01390.01410.01430.01480.01510.01560.01660.01780.01870.02100.02560.02990.029655.3981242274.5235677883.8098493153.3273354182.7241930462.3220981311.859688981.3570703361.0957086420.7237708460.4523567790.24

10、12569490.1105761010.070366610.0402094910.493490.492140.501540.507340.506230.520070.517950.532590.549160.559950.563780.627350.684450.680560.52932P水=994.244kg/m3口=73.418*10-Pa/S光滑管（彎頭）實驗數(shù)據(jù)處理實驗次數(shù)流速m/sRe阻力J/Kg阻力系數(shù)入局部阻力J/K阻力系數(shù)Z1（max）4.0764143530.55584.72770.09041.96130.2360523.8978137240.37184.84840.0990

11、1.82050.2396533.6055126947.34376.76180.10471.55900.2398643.2644114938.81163.10320.10501.28740.2416252.9721104645.78352.42170.10521.08630.2459562.566090349.910939.04470.10520.84490.2566272.306281200.552932.10480.10700.69400.2609782.013970907.52524.28980.10620.55320.2728091.624157183.487916.11270.1083

12、0.42240.32031101.364248034.129911.48610.10940.28160.30264111.055737169.26727.19140.11440.18100.32491120.649622873.39523.26880.13740.10060.47665130.487217155.04642.14230.16000.07040.59317140.14625146.513910.64370.53430.03022.82462150.08122859.17440.25140.67620.03029.151761.2410111.000.8424.1516.0211.

13、42120.657.15130.403.251.2410111.000.8424.1516.0211.42120.657.15130.403.250.3007092.130.640.5500.28互0.070.03平均溫度。C34.234.334.434.3五34.16光滑管0.0100粗糙管1、思考題對實驗結(jié)果進(jìn)行討論和分析1）由以上實驗數(shù)據(jù)處理的圖形可知，光滑管和粗糙管的入隨Re的增大而減小，且Re增大到一定數(shù)值時，入降低的速度變小2）由光滑管的Re先曲線可以看出實驗數(shù)據(jù)和符合Blasuis關(guān)系式3）局部阻力系數(shù)隨Re的增大而減小，當(dāng)Re增大到一定數(shù)值后局部組阻力系數(shù)變化率減小2如何檢驗實

14、驗裝置中的空氣是否已經(jīng)排凈？反復(fù)多次打開排氣管，通過觀察排氣管中有無氣泡來判斷為了取得較好的實驗結(jié)果，如何確定實驗點和測量次數(shù)？實驗點可以取的密集一些，測量次數(shù)可以取的多一點方便畫圖在不同設(shè)備（包括相對粗糙度相同而管徑不同）、不同溫下測定的A-Re數(shù)據(jù)能否關(guān)聯(lián)在一條曲線上？可以，因為摩擦阻力系數(shù)是Re、入、/d的函數(shù)，可以關(guān)聯(lián)到一條函數(shù)、不一定，因為入和Re與流體的密度和粘度有關(guān)。密度與粘度與溫度有關(guān)。所以不一定呢能關(guān)聯(lián)到同一條曲線上測出的直管阻力摩擦與設(shè)備的放置狀態(tài)有關(guān)么？無關(guān)如果要增加雷諾數(shù)的范圍，可采取那些措施？更改管徑，更改流體溫度，從而更改流體的粘度和密度。7.離心泵特性曲線的測定圖

15、3二、實驗內(nèi)容用作圖法處理實驗數(shù)據(jù)，繪制離心泵特性曲線三、實驗步驟打開壓差傳感器平衡閥，關(guān)閉離心泵調(diào)節(jié)閥，打開引水閥，反復(fù)開、關(guān)放氣閥，氣體被排盡后，關(guān)閉放氣閥和引水閥。啟動泵，將閥門開至最大，確定實驗范圍，依次減小流量進(jìn)行實驗，采集實驗數(shù)據(jù)（包括流量為零時的各有關(guān)參數(shù)），共16組數(shù)據(jù)。實驗結(jié)束后，先關(guān)控制閥，再關(guān)閉電機(jī)電源和總電源。四實驗數(shù)據(jù)處理揚程H=H二p2ppg效率耳效率耳的計算二耳二Ne/N二HVpg/N實驗次數(shù)流量L/S流量V(m3/h)P真空表MPdP壓力表MP揚程H/(m)功率N(W)效率n/%溫度。C13.6313.068-0.03400.080011.6944145428.

16、460834.723.4412.384-0.03150.100013.4896145531.090035.033.2411.664-0.02830.122515.4694145433.603335.143.0310.908-0.02550.145017.4903147035.143935.152.8210.152-0.02240.165019.2240146736.023735.362.619.396-0.01980.185021.0089146136.586435.372.418.676-0.01700.202522.5169144036.735835.482.157.740-0.01400

17、.217523.7479142934.830335.591.967.056-0.01290.230024.9173141433.669335.6101.726.192-0.00950.243025.9021137931.493835.7111.495.364-0.00750.255026.9279133629.275835.8121.254.500-0.00600.268528.1589128826.640135.8131.003.600-0.00340.275028.5590123822.487936.0140.812.916-0.00230.290029.9849113020.952536.2150.481.728-0.00100.305031.3903102014.400036.3160.150.5400.00000.312532.05708435.560536.5170.000.0000.00000.322533.08297280.000036.9平均溫度35.7P=993.705kg/m3水不合理。容易產(chǎn)生節(jié)流損