实验注意事项 - 华北水利水电学院.pdf

ExperimentalExperimentalExperimentalExperimental GuideGuideGuideGuide ofof ofof HydraulicHydraulicHydraulicHydraulic TransmissionTransmissionTransmissionTransmission North China Institute of Water Conservancy and Hydro electric Power March 2005 1 HydraulicHydraulicHydraulicHydraulic ExperimentExperimentExperimentExperiment OverviewOverviewOverviewOverview Laboratory exercises are important training links They can make engineering students directly tie analytical classroom theories with truly practical experiments and obtain the solid understanding of fluid power theories Most students miss a vital link between theory presented in the classroom and actual industrial problems Furthermore many graduates who start in the area of Force or Motion control are not able to make a design choice between Electromechanical Pneumatic or Hydraulic devices as a method of system actuation for a given problem Although they obtain a high degree of analytical expertise they are not as advanced in applying these analytical techniques to real world problems Therefore the objective of experiment teaching aims at giving engineering students a unique hands on experience with classes of off the shelf industrial devices This fluid power laboratory facility will allow students to directly tie theoretical classroom concepts with practical hands on experiments The laboratory exercises will give them the opportunity to gain a more thorough understanding and appreciation for their textbook and reading materials The fluid power laboratoryishoused in the Mechanical Engineering Laboratory andis enable engineering students to gain educational experience with off the shelf commercial devices that are crucial to modern industry The use of Fluid Power as an actuation device occurs in construction machinery vehicle aircraft manufacturing presses etc The driving motivation behind the laboratory was the fact that few engineering students ever come in contact with these devices although they stand a good chance of working with them after they leave the university The laboratory exercises give students the opportunity to tie theoretical classroom concepts with practical hands on experiments and to gain a more thorough understanding and appreciation for their textbook and reading materials The laboratory exercise items include Reynoldsflowregime demonstration hydraulic Resistance Characteristic Experiment pump performance experiment and speed control experiment These items completely agree with the specification of the course outline Besides these items a student can design his her own experiment according to his her willingbyusing the modular experimental bench of the laboratory Keep in mind that it is self evident for a laboratory to have potential hazards for injury It is everyone s goal to preventallaccidents and minimize hazard potential in this experiment course Therefore SAFETY ofallstudents and faculty will be an integral part of this course 2 ExperimentExperimentExperimentExperiment OneOneOneOneReynoldsReynoldsReynoldsReynolds FlowFlowFlowFlow R R R Regimeegimeegimeegime E E E Experimentxperimentxperimentxperiment 1 1 1 1 ExperimentalExperimentalExperimentalExperimental objectiveobjectiveobjectiveobjective Watch two kinds of flow regime lamina and turbulent flow and velocity profile of lamina flow By theway understand structure and operation of experiment benches 2 2 2 2 ExperimentExperimentExperimentExperiment principleprincipleprincipleprinciple andandandandexperimentexperimentexperimentexperiment benchbenchbenchbench 2 1 Reynolds numbe Reynolds numberisused to determine wether a flowislamina or turbulent and the expression of Reynolds number takes the form of VdVd Re Where disthe internal diameter of glass pipe for a QCS012 experiment bench the internal diameter of glass pipeisequal to 25 8 mm V represents mean velocity denotes kinetic viscosity of the fluid 2 2 The velocity profile on a cross sectionisa parabola when a flowislamina QCS012 experimental bench L W H 1555mm 420mm 1450mm isshown as figure 1 1 Figure 1 1 QCS012 Reynolds experimental bench 1 return line 2 large tank 3 small red tank 4 thin tube 5 circular glass pipe 6 contral valve 7 measure tank whichis made of organicglass withscale each gird represent 0 16 L 3 3 3 3 ExperimentExperimentExperimentExperiment stepsstepsstepssteps 3 1 Watchflow regime 3 1 1Fillwater fully to the large tank until the water surfaceissteady 3 1 2 Turn on control valve 6 slowly and then turn on the control valve situated on the thin tube Thus a red line can be watched which expresses the flowislaminar 3 1 3 Gradually turn on control valve 6 itisseen that the red line fluctuates then the red line 3 disappears which expresses that the red water mixes with other water and the flowisturbulent 3 2 Watchthe velocity profile of laminarflow Turn on the red water valve it can befound that the red water moves fast while the water near the pipe wall moves slowly which presents the velocity profile on the cross sectionisa parabola 4 4 4 4 NotNotNotNoticic ic iceseseses 4 1 It should be noted that itisnecessary to turn onthe two control valve slowly 4 2 In the course of regulation the two valves should berotated in one direction rather than rotated reversely 4 3 In order to avoid the thin tube blocked the red water should be pure After completing the experiment alltanks and pipes tubes should bewashed fully ExperimentExperimentExperimentExperiment TwoTwoTwoTwoHydraulicHydraulicHydraulicHydraulic R R R Resistanceesistanceesistanceesistance C C C Characteristicharacteristicharacteristicharacteristic E E E Experimentxperimentxperimentxperiment 1 1 1 1 ExperimentalExperimentalExperimentalExperimental objectiveobjectiveobjectiveobjective Understand deeply hydraulic resistance characteristics also called flow rate versus pressure drop characteristics of orifice 2 2 2 2 ExperimentExperimentExperimentExperimentalalalal contentscontentscontentscontents Measure the hydraulic resistance characteristics of thin wall orifice long orifice and so on In a hydraulic system a fluid flows through an orifice will result in energy loss The interrelationship between flow rate and pressure drop takes the form of m T QCAp Whereisthe flow rate factor isthe flow area of the orifice representsC T Ap pressure drop of the orifice isa exponent which depends on the orifice shape For a thinm wall orificeisequal to 0 5 whereas for a long orificeisequal to 1 approximately mm Under other conditions unchanged and via varying the relative resistant forces of two branch circuits of the system we can measure different pressure drops and corresponding flow rates of the orifice Then fill readings in the table After that draw flow rate versus pressure drop characteristic curve Next estimate the exponent Finally analyze the obtained data m 3 3 3 3 IntroductionIntroductionIntroductionIntroduction totototo thethethethe QSC002QSC002QSC002QSC002 experimentalexperimentalexperimentalexperimental benchbenchbenchbench 3 1 Main components Electric motor JO 22 4 1 5kw 1410r min Pump YB 6 6mL r 6 3MPa Oil No 30 hydraulicoil 3 2 Systematic diagram The systematic diagram of QSC002 experimental benchisshown as in Fig 2 1 4 Fig 2 1 Systematic diagram of QSC002 experimental bench 4 4 4 4 E E E Experimentalxperimentalxperimentalxperimental stepsstepsstepssteps 4 1 Measure of the hydraulic resistance characteristics of thin wall orifice First of all loose the handle of the pressure relief valve so as to make the system unload then shift the handles 22 23 of allocation valve to corresponding positions Press the start button of the pump After the pump runs for 3 minutes under no load set the systematic pressure less than 1 0 MPa The pressureisdisplayed on pressure gauge P1 The total resistanceisequal to the sum of the hydraulic resistance of thin wall orifice and that of the flow regulating valve Regulating the hydraulic resistance of the flow regulating valve can varythe total resistance of the circuit hence varying the flow rate of the circuit Entrance pressureP2and exit pressureP3are measuredbyoperating pressure gauge switch They are indicatedbythe accurate pressure gauge measure rangeisless than 1MPa Varying the hydraulic resistance measure the corresponding pressure drop of the orifice Measure time and volume simultaneouslybyusing a stopwatch and a volumenometer respectively Allthe measured data are filled in table 2 1 Table 2 1 records of flow rate versus pressure dropcharacteristics Orifice type Systematic pressure p1 MPa Temperat ure T oC P2i MPa P3i MPa Pi MPa Volume Vi L Time ti S Flow rate Qi L min Thin wall orifice Long orifice 5 5 5 5 5 DatumDatumDatumDatum processprocessprocessprocess The experimentisa test in nature The relationship of flow rate versus pressure dropis known The parameters of the expression need to be determinedbythese data Itisreasonable to utilize the error theory to process the data Taking the Logarithm of we have m pKaQ lg lglgKapmQ Let then calculating erroris lg lg lg iiii yQ bmp cKa n i ii cmbyE 1 2 Taking the partial derivatives ofmand letting the partial derivative expressionisequal to zero we have n i iii bcmby m E 1 0 2 Simplifying and rewriting the above expression yields 1 n i n i ii n i ii ybcbmb 111 2 In similarly reasoning we can obtain 2 n i n i ii yncmb 11 Solving the above equations formandc we obtain c Ka10 For example assumem 0 505 andKa 1 37 then we can obtain hydraulic resistance formula 0 505 1 37Qp 6 6 6 6 DrawingDrawingDrawingDrawing ofofofof thethethethe characteristiccharacteristiccharacteristiccharacteristic curvecurvecurvecurve The symbol isused to represent an experimental point Apply the data in the table whilethe above characteristic equationisused to draw the characteristic curve The flow rate versus pressure dropcharacteristic curveisshown as Fig 2 2 Fig 2 Flow rate versus pressure drop characteristic Fig 2 2Flow rateversus pressuredrop characteristic 7 7 7 7 AnalyAnalyAnalyAnalysissississis ofofofof experimentalexperimentalexperimentalexperimental resultsresultsresultsresults 6 ExperimentExperimentExperimentExperiment ThreeThreeThreeThreePumpPumpPumpPump P P P Performanceerformanceerformanceerformance E E E Experimentxperimentxperimentxperiment 1 1 1 1 ExperimentalExperimentalExperimentalExperimental objectiveobjectiveobjectiveobjective This experiment aims at making students understand vane pump efficiency performance 2 2 2 2 MainMainMainMain performanceperformanceperformanceperformance parametersparametersparametersparameters ofofofof QCS003BQCS003BQCS003BQCS003B experimentalexperimentalexperimentalexperimental benchbenchbenchbench Electric motor type J O2 2 4 revolving speed 1410r min Pump type YB 6 rated flow rate 8 46L min Rated pressure 6 3Mpa No 30 hydraulicoil 3 3 3 3 SystematicSystematicSystematicSystematic diagramdiagramdiagramdiagram The systematic diagramof QCS003B experimental benchisshown as in Fig 3 1 Fig 3 1 Systematic diagram of QCS003B experimental bench 4 4 4 4 ExperimentalExperimentalExperimentalExperimental contentscontentscontentscontents 4 1 Flow rate characteristic Pump leakage will result in energy loss The higher the pump pressureisthe greater the energy loss Via the experiment the experimental data obtained can be used to plot the relationship curve of the actual flow rate versus pressure 4 2Volumetric efficiency The Volumetric efficiencyisdefined as the ratio of the actual flow rate to the theoretical flow rate The volumetric efficiency expressionis T Q Q Whereisthe actual flow rate isthe theoretical flow rate which depends on the pumpQQT speed and geometry In practice the actual flow rateisfrequently replaced with the flow rate under no load 7 condition 4 3Overall efficiency The overall efficiency expression takes the form of o i P P whereisthe pump delivery power kw isthe pump input power kw o P i P Sincethe input powerof the electric motor can be determined from the reading of a watt meter we can obtain the delivery power of the electric motor according to the efficiency curve of the electric motor The pump input powerisequal to the output power of the electric motor Theoverall efficiency of the pumpis 1000 o iee PpQ PP Wherepisthe operation pressure Qisthe actual flow rate represents the input 3 s m e P power of the electric motor denotes the efficiency of the electric motor e 5 5 5 5 ExperimentalExperimentalExperimentalExperimental methodsmethodsmethodsmethods andandandand stepsstepsstepssteps 5 1 Make solenoid directional control valve 11 12 and16return to their normal position close throttle valve 10 in this manner we can obtain the circuit of the pump performances experiment 5 2Loose pressure relief valve 9 press the start button of the pump 5 3 Close throttle valve 10 set the systematic pressure 6 3Mpa bymeans of pressure relief valve 9 5 4 Measure theoretical flow rate Make throttle valve 10 open fully and then measure fluid volume and time so as to estimate the actual flow rate under no load condition the flow rate can be used to replace the theoretical flow rate 5 5 Measure actual flow rate Close throttle valve 10 gradually and measure fluid volume time and motor input powerwhen operation pressure ranges from 1 to 5Mpa Allthe datum e P recorders are filled in table 3 1 Table 3 1 Data ofpump performance experiment 5 6 After completing the experiment makeallbuttons and handles return to their original positions turn off the power source switch 5 7 Process data then plot p Q curve p curve p curve respectively No p MPa kw e P e kw i Pt sec V L Q 1 2 3 4 5 6 7 8 ExperimentExperimentExperimentExperiment FourFourFourFourS S S SpeedpeedpeedpeedC C C Controlontrolontrolontrol E E E Experimentxperimentxperimentxperiment 1 1 1 1 ExperimentalExperimentalExperimentalExperimental objectiveobjectiveobjectiveobjective Understand the principle and performance of various throttle speed control and be familiar with the structure and utilization of experimental benches 2 2 2 2 ExperimentalExperimentalExperimentalExperimental contentscontentscontentscontents 2 1 Require students themselves connect speed control circuits 2 2 Of meter in circuit meter out circuit by pass circuit and speed control circuitbyusing a flow regulating valve each student should select two circuits at least 3 3 3 3 ExperimentalExperimentalExperimentalExperimental benchbenchbenchbencheseseses There are3QCS003 experimental benches and a QCS014 experimental bench in our laboratory 4 4 4 4 MainMainMainMain performanceperformanceperformanceperformance parametersparametersparametersparameters andandandand systematicsystematicsystematicsystematic diagramdiagramdiagramdiagram ofofofof thethethethe benchesbenchesbenchesbenches The mainperformance parameters of the experimental benches are as follows Electric motor Y90L 4 83 1 5kw 1410 r min pump YB1 6 displacement 4ml r rated pressure 6 3MPa oilNo 30 hydraulicoil cylinder stroke L 250mm piston diameter D 40mm piston rod diameter d 30mm The systematic diagramof the experimental benchesisshown as in Fig 1 Fig 1 Systematic diagram of experimental benches 9 5 5 5 5 ExperimentalExperimentalExperimentalExperimental stepsstepsstepssteps 5 1 Pressure setting of load applied cylinder 18 Close throttle valve 10 and11and then loose pressure relief valve9 Press the start button of the pump 8 and set pressure relief valve 9 In this manner the output force of load exerting cylinder 18isdetermined Energize the solenoid of directional control valve12so as to make the cylinder move to the left As a result cylinder17isin the situation under a load 5 2Meter in speed control circuit Close by pass throttle valve 7 and flow regulating valve 4 and the open meter out throttle valve6fully Open meter in throttle valve 5 partially and the pressu