管路中液体的压力损失：因为实际液体具有粘性，所以流动中必有阻力，为克服阻力，须消耗能量，造成能量损失（即压力损失） 分类：沿途压力损失，局部压力损失液流动状态 层流：液体的流动是分层的，层与层之间互不干扰。
湍流(湍流):液体不分层流动，混合紊流 圆形管道雷诺数：Re=dv/ν 非圆管道截面雷诺数：Re=dHv/ν 过流断面水力直径：dH=4A/χ 水力直径大，液流阻力小，通流能力大ReRec为紊流 沿途压力损失的原因 1.内摩擦—因粘性，液体分子间摩擦 2.外摩擦—液体与管壁间 流速分布规律 液体在等径水平直管中作层流运动，沿管轴线取一半径为r，长度为l的小圆柱体两端面压力为p1、p2，侧面的内摩擦力为F，匀速运动时，其受力平衡方程为：(p1-p2)πr2=F ∵F=-2πrlμdu/dr△p=p1-p2∴du=-rdr△p/2μl，对上式积分，并应用边界条件r=R时，u=0,得u=(R2-r2)△p/4μl结论：液体在圆管中作层流运动时，速度对称于圆管中心线并按抛物线规律分布。
umin=0(r=R)umē=R2△p/4μl=d2△p/16μl(r=0) 圆管层流的流量：∵dA=2πrdr ∴dq=udA=2πurdr =2π(R2-r2)△p/4μl，故q=∫0R2π△p/4μl·(R2-r2)rdr =△pπR4/8μl=△pπd4/128μl圆管的平均流速：v=q/A=pπd4/128μl)πd2/4=△pd2/32μl v=umax/2圆管沿程压力损失 △pf=128μlq/πd4=8μlq/πR4 将q=πR2v，μ=ρν代入上式并简化：△pf=△p=32μlv/d结论：当液流沿圆管层流时，其压力损失与管长、流速、粘度成正比，与管径平方成正比。
∵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理论值64/Re，实际值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/△）∵紊流运动时，△pλ比层流大 ∴液压系统中液体在管道内应尽量作层流运动 局部压力损失的定义：当液体通过弯头、接头、突变截面、阀门滤网等局部装置时，液体流动会产生旋涡，产生强烈的紊乱 动现象，由此而产生的损失称为局部损失。
产生原因：碰撞、旋涡（突变管、弯管）产生附加摩擦 附加摩擦—只有紊流时才有，是由于分子作横向运动时产生的 摩擦，即速度分布规律改变，造成液体的附加摩擦局部压力损失公式 ：△pv=ζ·ρv2/2 标准阀类元件局部压力损失 ：△pv=△pn(qv/qvn)2管路系统的总压力损失：∑△p=∑△pλ+∑△pv=∑λ·l/d·ρv/2+∑ζρv2/2△p→热能→T↑→△q↑→η↓ 减小△p的措施1尽量↓L，↓突变 2↑加工质量，力求光滑，ν合适3↑A，↓v 其中v的影响最大，过高△p↑∵△p∝v2；过低尺寸↑成本↑，所以一般有推荐流速可供参考，见有关手册。
一般在液压传动中，可将压力损失写成如下形式：∑△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。
