管路中液體的壓力損失：因為實際液體具有粘性，所以流動中必有阻力，為克服阻力，須消耗能量，造成能量損失（即壓力損失） 分類：沿途壓力損失，局部壓力損失液流動狀態(tài) 層流：液體的流動是分層的，層與層之間互不干擾。
湍流(湍流):液體不分層流動，混合紊流 圓形管道雷諾數(shù)：Re=dv/ν 非圓管道截面雷諾數(shù)：Re=dHv/ν 過流斷面水力直徑：dH=4A/χ 水力直徑大，液流阻力小，通流能力大ReRec為紊流 沿途壓力損失的原因 1.內(nèi)摩擦—因粘性，液體分子間摩擦 2.外摩擦—液體與管壁間 流速分布規(guī)律 液體在等徑水平直管中作層流運動，沿管軸線取一半徑為r，長度為l的小圓柱體兩端面壓力為p1、p2，側(cè)面的內(nèi)摩擦力為F，勻速運動時，其受力平衡方程為：(p1-p2)πr2=F ∵F=-2πrlμdu/dr△p=p1-p2∴du=-rdr△p/2μl，對上式積分，并應(yīng)用邊界條件r=R時，u=0,得u=(R2-r2)△p/4μl結(jié)論：液體在圓管中作層流運動時，速度對稱于圓管中心線并按拋物線規(guī)律分布。
umin=0(r=R)umē=R2△p/4μl=d2△p/16μl(r=0) 圓管層流的流量：∵dA=2πrdr ∴dq=udA=2πurdr =2π(R2-r2)△p/4μl，故q=∫0R2π△p/4μl·(R2-r2)rdr =△pπR4/8μl=△pπd4/128μl圓管的平均流速：v=q/A=pπd4/128μl)πd2/4=△pd2/32μl v=umax/2圓管沿程壓力損失 △pf=128μlq/πd4=8μlq/πR4 將q=πR2v，μ=ρν代入上式并簡化：△pf=△p=32μlv/d結(jié)論：當(dāng)液流沿圓管層流時，其壓力損失與管長、流速、粘度成正比，與管徑平方成正比。
∵μ=ρνRe=dv/νλ=64/Re ∴△pf=64ν/dv·l/d·ρv2/2=64/Re··l/d·ρv2/2 故△pf=λ·l/d·ρv2/2λ理論值64/Re，實際值75/Re △pλ=λ·l/d·ρv2/2 λ=0、032+0.221Re-0.237（3*106>Re>105） λ=[1、74+2lg（d/△）]-2（Re>3*106或Re>900d/△）∵紊流運動時，△pλ比層流大 ∴液壓系統(tǒng)中液體在管道內(nèi)應(yīng)盡量作層流運動 局部壓力損失的定義：當(dāng)液體通過彎頭、接頭、突變截面、閥門濾網(wǎng)等局部裝置時，液體流動會產(chǎn)生旋渦，產(chǎn)生強烈的紊亂 動現(xiàn)象，由此而產(chǎn)生的損失稱為局部損失。
產(chǎn)生原因：碰撞、旋渦（突變管、彎管）產(chǎn)生附加摩擦 附加摩擦—只有紊流時才有，是由于分子作橫向運動時產(chǎn)生的 摩擦，即速度分布規(guī)律改變，造成液體的附加摩擦局部壓力損失公式 ：△pv=ζ·ρv2/2 標(biāo)準(zhǔn)閥類元件局部壓力損失 ：△pv=△pn(qv/qvn)2管路系統(tǒng)的總壓力損失：∑△p=∑△pλ+∑△pv=∑λ·l/d·ρv/2+∑ζρv2/2△p→熱能→T↑→△q↑→η↓ 減小△p的措施1盡量↓L，↓突變 2↑加工質(zhì)量，力求光滑，ν合適3↑A，↓v 其中v的影響最大，過高△p↑∵△p∝v2；過低尺寸↑成本↑，所以一般有推薦流速可供參考，見有關(guān)手冊。
一般在液壓傳動中，可將壓力損失寫成如下形式：∑△p=p1-p2 90-L-075-HF-1-AB-60-R-3-S1-D-04-GBA-38-38-24 90L075HF1AB60R3S1D04GBA383824 90-L-075-HF-1-AB-60-R-3-S1-E-04-GBA-35-35-24 90L075HF1AB60R3S1E04GBA353524 90-L-075-HF-1-AB-61-R-3-S1-D-00-GBA-35-35-20 90L075HF1AB61R3S1D00GBA353520 90-L-075-HF-1-AB-80-R-3-S1-C-03-GBA-35-35-24 90L075HF1AB80R3S1C03GBA353524 90-L-075-HF-1-AB-80-R-3-S1-D-00-GBA-35-35-24 90L075HF1AB80R3S1D00GBA353524 90-L-075-HF-1-AB-80-R-3-S1-D-02-GBA-35-35-24 90L075HF1AB80R3S1D02GBA353524 90-L-075-HF-1-AB-80-R-4-T2-D-03-GBA-35-35-24 90L075HF1AB80R4T2D03GBA353524 90-L-075-HF-1-AB-80-S-3-S1-D-00-GBA-23-23-20 90L075HF1AB80S3S1D00GBA232320 90-L-075-HF-1-AB-80-S-3-S1-D-03-GBA-42-42-24 90L075HF1AB80S3S1D03GBA424224 90-L-075-HF-1-AB-80-S-3-S1-E-03-GBA-42-42-24 90L075HF1AB80S3S1E03GBA424224 90-L-075-HF-1-AB-80-S-3-S1-E-03-GBA-42-42-32 90L075HF1AB80S3S1E03GBA424232 90-L-075-HF-1-AC-60-D-3-S1-L-04-GBA-35-35-24 90L075HF1AC60D3S1L04GBA353524 90-L-075-HF-1-AC-60-D-3-S1-L-04-GBA-38-38-24 90L075HF1AC60D3S1L04GBA383824 90-L-075-HF-1-AC-60-R-3-S1-E-04-GBA-35-35-24 90L075HF1AC60R3S1E04GBA353524 90-L-075-HF-1-AC-60-R-3-S1-E-04-GBA-38-38-24 90L075HF1AC60R3S1E04GBA383824 90-L-075-HF-1-AC-60-R-3-S1-E-06-GBA-35-35-24 90L075HF1AC60R3S1E06GBA353524 90-L-075-HF-1-BB-80-P-3-S1-D-03-GBA-35-35-24 90L075HF1BB80P3S1D03GBA353524 90-L-075-HF-1-BB-80-P-4-S1-D-03-GBA-35-35-24 90L075HF1BB80P4S1D03GBA353524 90-L-075-HF-1-BC-60-D-3-S1-L-04-GBA-35-35-24 90L075HF1BC60D3S1L04GBA353524 90-L-075-HF-1-BC-60-D-3-S1-L-04-GBA-38-38-24 90L075HF1BC60D3S1L04GBA383824 90-L-075-HF-1-BC-60-R-3-S1-D-03-GBA-26-26-24 90L075HF1BC60R3S1D03GBA262624 90-L-075-HF-1-BC-60-R-3-S1-D-03-GBA-32-32-24 90L075HF1BC60R3S1D03GBA323224 90-L-075-HF-1-BC-60-R-3-S1-E-04-GBA-35-35-24 90L075HF1BC60R3S1E04GBA353524 90-L-075-HF-1-BC-60-R-3-S1-E-04-GBA-38-38-24 90L075HF1BC60R3S1E04GBA383824 90-L-075-HF-1-BC-80-P-3-S1-C-02-GBA-38-38-24 90L075HF1BC80P3S1C02GBA383824 90-L-075-HF-1-BC-80-P-3-S1-D-02-GBA-38-38-24 90L075HF1BC80P3S1D02GBA383824 90-L-075-HF-1-BC-80-P-3-S1-D-03-GBA-32-32-22 90L075HF1BC80P3S1D03GBA323222 90-L-075-HF-1-BC-80-P-3-S1-D-03-GBA-35-35-24 90L075HF1BC80P3S1D03GBA353524 90-L-075-HF-1-BC-80-P-3-S1-D-03-GBA-38-38-24 90L075HF1BC80P3S1D03GBA383824 90-L-075-HF-1-BC-80-R-3-S1-D-00-GBA-35-35-24 90L075HF1BC80R3S1D00GBA353524 90-L-075-HF-1-BC-80-R-3-S1-D-03-GBA-35-35-20 90L075HF1BC80R3S1D03GBA353520 90-L-075-HF-1-BC-80-R-3-S1-E-00-GBA-38-38-24 90L075HF1BC80R3S1E00GBA383824 90-L-075-HF-1-BC-80-R-4-S1-D-03-GBA-20-20-24 90L075HF1BC80R4S1D03GBA202024 90-L-075-HF-1-BC-80-R-4-S1-D-03-GBA-35-35-24 90L075HF1BC80R4S1D03GBA353524 90-L-075-HF-1-BC-80-R-4-S1-E-09-GBA-35-35-24 90L075HF1BC80R4S1E09GBA353524 90-L-075-HF-1-BC-80-S-3-S1-D-03-GBA-35-35-24 90L075HF1BC80S3S1D03GBA353524 90-L-075-HF-1-BC-80-S-4-S1-D-03-GBA-20-20-20 90L075HF1BC80S4S1D03GBA202020 90L075-HF-1-BC-80-S-4-S1-D-03-GBA-26-26-20 90L075HF1BC80S4S1D03GBA262620 90-L-075-HF-1-BC-80-S-4-S1-D-03-GBA-26-26-20 90L075HF1BC80S4S1D03GBA262620 90-L-075-HF-1-CD-60-P-3-S1-D-03-GBA-42-42-24 90L075HF1CD60P3S1D03GBA424224 90-L-075-HF-1-CD-60-P-3-S1-E-00-GBA-17-17-24 90L075HF1CD60P3S1E00GBA171724 90-L-075-HF-1-CD-80-P-3-S1-E-03-GBA-42-42-24 90L075HF1CD80P3S1E03GBA424224 90-L-075-HF-1-CD-80-P-4-S1-D-03-GBA-32-32-24 90L075HF1CD80P4S1D03GBA323224 90-L-075-HF-1-CD-80-R-3-C7-E-03-GBA-35-35-24 90L075HF1CD80R3C7E03GBA353524 90-L-075-HF-1-CD-80-R-4-S1-D-03-GBA-32-32-24 90L075HF1CD80R4S1D03GBA323224 90-L-075-HF-1-CD-80-S-4-S1-D-03-GBA-35-35-20 90L075HF1CD80S4S1D03GBA353520 90-L-075-HF-1-NN-60-L-3-S1-E-03-GBA-32-32-24 90L075HF1NN60L3S1E03GBA323224 90-L-075-HF-1-NN-60-P-3-C6-D-03-GBA-38-38-24 90L075HF1NN60P3C6D03GBA383824 90-L-075-HF-1-NN-60-P-3-S1-E-00-GBA-26-32-24 90L075HF1NN60P3S1E00GBA263224 90-L-075-HF-1-NN-60-P-4-S1-D-03-GBA-42-42-20 90L075HF1NN60P4S1D03GBA424220 90-L-075-HF-1-NN-60-R-3-S1-D-03-GBA-35-35-24 90L075HF1NN60R3S1D03GBA353524 90-L-075-HF-1-NN-60-S-3-S1-D-03-GBA-38-38-24 90L075HF1NN60S3S1D03GBA383824 90-L-075-HF-1-NN-80-P-3-S1-E-03-GBA-35-35-24 90L075HF1NN80P3S1E03GBA353524 90-L-075-HF-1-NN-80-P-3-S1-E-03-GBA-42-42-24 90L075HF1NN80P3S1E03GBA424224 90-L-075-HF-1-NN-80-P-3-S1-E-03-GBA-42-42-32 90L075HF1NN80P3S1E03GBA424232 90-L-075-HF-1-NN-80-P-4-S1-D-00-GBA-17-17-24 90L075HF1NN80P4S1D00GBA171724 90-L-075-HF-1-NN-80-P-4-S1-D-03-GBA-35-35-24 90L075HF1NN80P4S1D03GBA353524 90-L-075-HF-1-NN-80-R-3-S1-D-00-GBA-42-42-24 90L075HF1NN80R3S1D00GBA424224 90-L-075-HF-1-NN-80-R-3-S1-D-03-GBA-26-26-24 90L075HF1NN80R3S1D03GBA262624 90-L-075-HF-1-NN-80-R-3-S1-D-03-GBA-35-35-24 90L075HF1NN80R3S1D03GBA353524 90-L-075-HF-1-NN-80-R-3-S1-E-03-GBA-42-42-24 90L075HF1NN80R3S1E03GBA424224 90-L-075-HF-1-NN-80-R-4-S1-D-03-GBA-32-32-24 90L075HF1NN80R4S1D03GBA323224 90-L-075-HF-1-NN-80-R-4-S1-E-03-GBA-35-35-24 90L075HF1NN80R4S1E03GBA353524 90-L-075-HF-1-NN-80-S-3-S1-D-03-GBA-42-42-20 90L075HF1NN80S3S1D03GBA424220 90-L-075-HF-1-NN-80-S-3-S1-E-03-GBA-32-32-24 90L075HF1NN80S3S1E03GBA323224 90-L-075-HF-1-NN-80-S-3-S1-E-03-GBA-42-42-24 90L075HF1NN80S3S1E03GBA424224 90-L-075-HF-1-NN-80-S-4-S1-C-00-GBA-42-42-28 90L075HF1NN80S4S1C00GBA424228 90-L-075-HF-1-NN-80-S-4-S1-D-00-GBA-38-38-24 90L075HF1NN80S4S1D00GBA383824。
