0.8m³.min渦旋式空氣壓縮機設(shè)計

0.8m3.min渦旋式空氣壓縮機設(shè)計,0.8,min,渦旋式,空氣壓縮機,設(shè)計 三維滾動渦旋壓縮機的發(fā)展 摘要：渦旋壓縮機因為其高效率，低振動的優(yōu)勢已被廣泛應(yīng)用于各種場合。為了進一步提高渦旋壓縮機性能，作者發(fā)展了一個新的三維壓縮機制（立體滾動），即通過添加一個軸向壓縮，到傳統(tǒng)的徑向壓縮。三維壓縮的實現(xiàn)，使得傳統(tǒng)壓縮機不可能實現(xiàn)的更高效率，更高的可靠性，體積小得以實現(xiàn)。由于立體滾動從滾動頂端到端板有步驟，使得三維壓縮效率提高的關(guān)鍵點是要盡量減少氣體在端板出的泄漏。通過氣缸壓力測量及可視化試驗，可獲得端板泄漏特性，得到了最佳間隙范圍。在此基礎(chǔ)上，作者開發(fā)了高效率，體積小，重量輕的立體滾動商用空調(diào)壓縮機。所研發(fā)的三維滾動與傳統(tǒng)的壓縮機相比，壓縮機體積減小35%，重量減輕26%，效率提高5.5%。 關(guān)鍵詞：壓縮機，設(shè)計，制冷，控制，性能，開發(fā)，仿真 1引言 從環(huán)境保護和應(yīng)對全球變暖的角度出發(fā)，節(jié)約能源的要求越來越緊迫。由于大多數(shù)的制冷和空調(diào)電器是由壓縮機轉(zhuǎn)化的能源，因此它的效率的提高是節(jié)能不可缺少的。同時，這些設(shè)備往往在其安裝空間受到限制。因此，每個組件，包括壓縮機都應(yīng)小型化，從而提高了安裝的靈活性。今天，渦旋壓縮機，它具有高效率，低振動的優(yōu)勢，已為各種電器使用，以滿足對節(jié)約能源的需求和它的更廣泛的使用。為了進一步提高渦旋壓縮機性能，作者發(fā)展了一個新的三維壓縮機制（立體滾動），即通過添加一個軸向壓縮，到傳統(tǒng)的徑向壓縮。本文介紹了三維滾動的效率改進技術(shù)和立體滾動商業(yè)空調(diào)壓縮機的發(fā)展。 2三維結(jié)構(gòu)渦旋 2.1三維滾動的立體特征 圖1 三維滾動渦旋壓縮機 圖1展示了商用立體滾動壓縮機和其立體滾動渦旋型線。從圖中看出氣體達到了壓縮室正從外側(cè)壓縮到內(nèi)側(cè)。壓縮機的制冷劑是從固定渦旋的中心流出。 圖 2 傳統(tǒng)壓縮和三維滾動的剖視圖 圖2從剖視結(jié)構(gòu)揭示了常規(guī)壓縮和立體滾動的原理。傳統(tǒng)渦旋齒的高度在整個壓縮過程為常數(shù)，壓縮制冷劑從外側(cè)到壓縮腔內(nèi)側(cè)數(shù)量不斷變小。對于立體滾動，相反，在頂端和末端通過安裝使得外側(cè)端板比內(nèi)側(cè)端板高。從而使得三維壓縮，即徑向和軸向方向成為可能。 三維滾動具有以下特點。 1) 通過徑向和軸向壓縮得到了更高的壓縮比。 2)由于降低了內(nèi)側(cè)齒的重量，渦旋齒的強度得到提高，獲得了高的可靠性，這樣便減輕了一個沉重的負擔。 3)由于增加了外齒的高度，滾動外徑?jīng)]有擴展，使得壓縮空間更大，因此三維壓縮的積小，重量更輕。 2.2壓縮機制和立體滾動間隙泄漏 在圖3 中展示了三維滾動的壓縮機制。從滾動頂端到端板，三維壓縮是有步驟進行的。當不符合這些壓縮步驟時（見圖3（b）到（d）項）切線看，壓縮腔具有相同的壓力因此，在這一過程中沒有泄露。另一方面，當符合這一壓縮步驟時（見圖3（a）到（c）項），密封線是由兩個步驟結(jié)合而來的。 圖3也顯示了第一步的局部放大圖和在軌道縱向方向滾動剖面圖。每兩步的間隙（以下簡稱步間隙），大致可分為末端間隙和側(cè)面間隙，氣體從高壓腔到低壓腔的泄露是從這些間隙發(fā)生的。因此，立體滾動壓縮效率提高的關(guān)鍵點是通過優(yōu)化步間隙來減少氣體在步間隙的泄露。 圖3三維滾動的壓縮機制 SPECIAL ISSUE PAPER193Development of a three-dimensional scroll compressorH Sato1,M Fujitani2,H Kobayashi2,H Mizuno2,andT Itoh11Nagoya Research and Development Center, Mitsubishi Heavy Industries, Ltd, Nagoya, Japan2Air-Conditioning and Refrigeration Systems Headquarters, Mitsubishi Heavy Industries, Ltd,3-1 Asahi Nishibiwajima-cho Kiyosu, Aichi 452-8561, JapanThe manuscript was received on 6 December 2007 and was accepted after revision for publication on 16 September 2008.DOI: 10.1243/09544089JPME189Abstract: Scrollcompressorhasbeenemployedinvariousappliancesduetoitsadvantagessuchas high efficiency and low vibration. For the purpose of further performance improvement inscroll compressor, the authors have developed a new conceptual three-dimensional compres-sion mechanism (three-dimensional scroll) by adding an axial compression to the conventionalradial compression. By realizing three-dimensional compression, which has been impossible forthe conventional scroll, higher efficiency, higher reliability, and smaller size are achieved. Sincethe three-dimensional scroll has steps in scroll tip and end plate, the key point of efficiencyimprovementinthethree-dimensionalscrollistominimizethegasleakageinthesteps.Throughcylinder pressure measurements and visualization tests, characteristics of the leakage in thestepsareobtainedandtheoptimumclearancerangesaredetermined.Basedonthis,theauthorshave developed high efficiency, small size, and lightweight three-dimensional scroll compressorfor commercial air-conditioner. The developed three-dimensional scroll compressor archived35 per cent smaller size, 26 per cent lighter weight, and 5.5 per cent improvement of efficiencycompared with the conventional one.Keywords: compressors, design, refrigeration, control, performance, development, simulation1INTRODUCTIONAdemand for saving energy has been extensivelyincreasing from the viewpoint of environmental con-servation against global warming. Since most energyin refrigerating and air-conditioning appliances isconsumed by the compressor, its efficiency improve-ment is indispensable for saving energy. Meanwhile,these appliances are often restricted in their installa-tionspace.Therefore,miniaturizationofeachcompo-nent including the compressor is required to enhancethe flexibility of installation.Today, scroll compressor, which has advantagessuch as high efficiency and low vibration, has beenused for various appliances to meet the demandfor saving energy and its use is expected to spreadincreasingly. For the purpose of further performanceCorrespondingauthor:NagoyaResearchandDevelop-ment Center, Mitsubishi Heavy Industries, Ltd, 1-TakamichiIwatsuka-cho Nakamura-ku, Nagoya 453-8515, Japan. email:hajime_satomhi.co.jpimprovement in scroll compressor, the authors havedeveloped a new conceptual three-dimensional com-pression mechanism (three-dimensional scroll) thatadds an axial compression to the conventional radialcompression.This article describes the efficiency improvementtechnology in the three-dimensional scroll and thedevelopment of the three-dimensional scroll com-pressor for commercial air-conditioner.2STRUCTURE OFTHETHREE-DIMENSIONALSCROLL2.1Features of the three-dimensional scrollFigure1showsthedevelopedthree-dimensionalscrollcompressorforcommercialair-conditionerandapho-tographoftheorbitingscroll.Refrigerantgasflowsintothecompressorthroughthesuctionpipeplacedontheside body. Then, it reaches the compression chambergetting compressed from the outer side to the innerside. The compressed refrigerant is discharged fromthe centre of the fixed scroll.JPME189IMechE 2008Proc. IMechE Vol. 222 Part E: J. Process Mechanical Engineering194H Sato,M Fujitani,H Kobayashi,H Mizuno,andT ItohFig.1Three-dimensional scroll compressorFig.2Sectional view of the conventional and the three-dimensional scrollFigure 2 shows a schematic diagram of the sectionalview of the conventional and the three-dimensionalscroll. The wrap height of the conventional scroll isconstant throughout the compression process, andtherefrigerantiscompressedtwo-dimensionallyfromthe outer side to the inner side as the compressionchamber continuously becomes smaller in volume.Forthethree-dimensionalscroll,incontrast,theouterwrap is higher than the inner one by installing stepsin the scroll tip and the end plate. Therefore, three-dimensional compression, radial and axial direction,becomes possible.The three-dimensional scroll has the following fea-tures.1. Higher compression ratio is obtained by radial andaxial compression.2. The strength of scroll wrap is improved and higherreliability is obtained by decreasing the height ofinner wrap, which receives a heavy load.3. Largercapacityisobtainedwithoutextensionoftheouter diameter of scroll by increasing the height ofouter wrap, and thus the three-dimensional scrollhas smaller size and lighter weight.2.2Compression mechanism and leakageclearances in the three-dimensional scrollThecompressionmechanismofthethree-dimensionalscroll is shown in Fig. 3. The three-dimensional scrollhas steps in the scroll tip (tip step) and the end plate(bottom step).When these steps are not engaged (seeFigs 3(b) and (d), compression chambers across thestep have the same pressure. Therefore, no leakageProc. IMechE Vol. 222 Part E: J. Process Mechanical EngineeringJPME189IMechE 2008Development of a three-dimensional scroll compressor195Fig.3Compression mechanism of the three-dimensional scrolloccurs in the steps. On the other hand, when these areengaged (see Figs 3(a) and (c), seal lines are formedby the engagement of both steps.Figure 3 also shows the enlarged view of the stepand the sectional view in the longitudinal directionof the orbiting scroll. Leakage clearances in the step(hereafter called step clearances) can be broadly clas-sified into tip clearance and side clearance, and thegas leakage occurs from the high-pressure chamber tothe low-pressure chamber through these clearances.Therefore, the key point of efficiency improvement inthe three-dimensional scroll is to minimize the gasleakageinthestepsbyoptimizationofstepclearances.3EFFICIENCY IMPROVEMENT OFTHREE-DIMENSIONAL SCROLL3.1Optimization of clearances in the stepsAs mentioned above, it is important for three-dimensional scroll to reduce the gas leakage in thesteps. To investigate leakage characteristics in thestepclearances,cylinderpressuremeasurementswereconducted and indicative efficiencies were obtainedfromPV diagram.Figure4showsanexampleofmea-suredPV diagram.Thisshowsthatthepressurecurvefollows about the same line as the ideal one when thestep clearance is small. However, when it becomeslarge the pressure curve moves in a direction awayfrom the ideal curve due to increase in gas leakage.Figure 5 shows the variation of indicative efficiencyiobtained from the PV diagrams against step clear-ances where Fig. 5(a) is the result when the sideclearance is fixed and the tip clearance is varied andFig.4PV diagramFig. 5(b) is when the tip clearance is fixed and theside clearance is varied.The indicative efficiency ratiois defined as the proportion of the result at /0= 1.From Fig. 5(a), it can be seen that the indicativeefficiency is improved with decreasing tip clearance.However,itplateauedintheregionwherethetipclear-ance is small because the clearance is filled with oilwhen it is sufficiently small, and thus the gas leak-age is decreased. As can be seen in Fig. 5(b), it hasthe same tendency when the side clearance is varied.Theseresultsindicatethatthereductionofleakagelosscan be obtained by setting the step clearances withinthe range between the minimum value determinedfrom the tolerance of profile, thermal deformation,and pressure deformation, and the maximum valuedetermined from the permitted limit of efficiency.JPME189IMechE 2008Proc. IMechE Vol. 222 Part E: J. Process Mechanical Engineering196H Sato,M Fujitani,H Kobayashi,H Mizuno,andT ItohFig.5Variation of indicative efficiency against step clearances3.2Sensitivity of leakage in the step clearancesInthenextstep,sensitivityofleakageinthestepclear-ances is considered. Quantities of leakage flow in thetip clearance and the side clearance are examinedbyexperimentalandanalyticalapproach,respectively.Thesensitivityofleakageineachclearanceisobtainedby the following processes.1. PV diagrams are drawn by cylinder pressure mea-surementsvaryingtipandsideclearancesindepen-dently.2. Considering mass and heat balance, leakage analy-sesareconducted.Here,leakageflowG issupposedto be governed by the equation of nozzle flow asfollowsG = C A ?2 1P11?P2P1?2/?P2P1?+1/?whereC istheflowcoefficient,A istheareaofclear-ance, P1and P2are the pressure at inlet and outlet,respectively, 1is the density of fluid at inlet, and is the specific heat ratio.3. Flow coefficients Ctipand Csideare determined bycomparing analytical results with PV diagramsfrom cylinder pressure measurements.In this study, 45 cases of cylinder pressure measure-ments(tipclearance:threecases,sideclearance:threecases, and operating condition: five cases) and corre-spondinganalysesweremade.Asaresult,itwasfoundthat flow coefficients Ctipand Csidehave a relationshipas followsCside= 1.7 CtipThis indicates that the quantity of leakage flow parsectionalareainthesideclearanceislargerthanthatinthetipclearance.Thedifferenceisattributedtothedif-ference of longitudinal shapes of each clearance. Theside clearance is composed of two circular walls (tipstep and bottom step). Therefore, the length of sideclearance in the direction of leakage flow is shorterthan the wrap thickness, whereas the length of tipclearance is equal to the wrap thickness.3.3Visualization of leakage flow in the stepclearanceVisualization tests were performed to examine thebehaviour of leakage flow in the step clearance. A pro-totype compressor that can observe the behaviour ofleakageflowinthestepclearancewasmade.Thiscom-pressor equipped a sight glass in the end plate of fixedscroll, and the orbiting motion of the orbiting scrollandthebehaviourofleakageflowwerevisualizedwitha high-speed video camera.Photographs of leakage flow are shown in Fig. 6. Ineachphotograph,thehigh-pressurechamberisontheright side and the low-pressure chamber is on the leftside. Figures 6(a), (b), and (c) show the variation withthe oil circulation ratio (OCR). Focusing on the sideclearance marked with circles, it is found that thereis no oil in the clearance and the gas leakage occursthrough the clearance when the OCR is small (seeFig. 6(a). On the other hand, when the OCR increasesas shown in Figs 6(b) and (c), the clearance is filledwith oil and an oil-flow along the bottom step is alsoobserved. Figures 6(d) and (e) show the variation withthe magnitude of clearance setting the OCR at a con-stant value. The clearance is filled with oil when itis small as in Fig. 6(d). However, when the clearanceis large as in Fig. 6(e), it is no longer filled with oiland the gas leakage occurs. This indicates that therequired OCR to seal the step clearances depends onProc. IMechE Vol. 222 Part E: J. Process Mechanical EngineeringJPME189IMechE 2008Development of a three-dimensional scroll compressor197Fig.6Visualization of leakage flow in step clearancethe magnitude of clearance, and it is also important toset the oil content in the cylinder at a proper value.Bytheabove-mentionedapproaches,thestepclear-ances in the developed three-dimensional scroll com-pressor were optimized keeping the OCR in the samelevel as the conventional one.3.4Reduction of thrust bearing lossThe coefficient of friction in the thrust bearing is con-sidered rather higher than that in the journal bearingsin scroll compressor due to the difference of lubrica-tion condition 1. Therefore, the thrust bearing lossoccupies a large part of the total mechanical lossand it is necessary for performance improvement todecrease the thrust bearing loss.The thrust bearing loss Wthrustis given as followsWthrust= thrustFthrust(2 N)where thrustis the coefficient of friction of the thrustbearing, Fthrustis the thrust gas force, is the orbit-ing radius, and N is the rotation speed. Assuming thatthelubricationconditionofthethrustbearingandtheoperating condition are constant, the thrust bearingloss depends only on the thrust gas force and orbitingradius.Figure 7 shows a schematic diagram of thrust bear-ing in the conventional and the three-dimensionalscroll. By introducing three-dimensional scroll, thewrap height can be set at a higher value, and the outerdiameter can be decreased compared with the con-ventional scroll, which has the same capacity. Accord-ingly, the area of end plate which receives cylinderpressure can be decreased and thus the thrust gasforce is reduced. Moreover, the orbiting radius can bealso set at a smaller value and the sliding distance isdecreased.For the developed three-dimensional scroll com-pressor described in the next section, the scroll diam-eter and the orbiting radius are decreased by 9 and 20percentrespectively,comparedwiththeconventionalscroll. As a result, a substantial reduction of thrustbearing loss is archived.4FEATURES OFTHE DEVELOPEDTHREE-DIMENSIONAL SCROLL COMPRESSORThe main changes from the conventional compressorto the developed one are listed below.1. The newly developed three-dimensional scroll wasemployed.2. Bypass ports are installed to avoid over compres-sion.3. A higher efficiency motor was adopted.The main dimensional data of the developed three-dimensional scroll compressor for 10PS commercialair-conditioner and the conventional one, which hasthe same capacity, are shown in Table 1 and theoutlines of both compressors are shown in Fig. 8.The developed three-dimensional scroll compressorJPME189IMechE 2008Proc. IMechE Vol. 222 Part E: J. Process Mechanical Engineering198H Sato,M Fujitani,H Kobayashi,H Mizuno,andT ItohFig.7Schematic diagram of thrust bearingTable 1Dimension comparisons between the conven-tional and the three-dimensional scrollDevelopedthree-dimensionalConventionalscrollscrollCooling capacity28kW28kWRatio of orbiting radius3D/conv0.801Ratio of wrap heightL3D/Lconv1.241Ratio of scroll diameterD3D/Dconv0.911Fig.8Outlineofthedevelopedthree-dimensionalscrollcompressor and the conventional onearchived 35 per cent reduction of volume and 26per cent reduction of weight by introducing three-dimensional scroll.Figure 9 shows the efficiency improvement ofthe developed three-dimensional scroll compressor.Figure 9(a) shows the variation of efficiency againstoperating pressure ratio. In this figure, the motor effi-ciency was eliminated from the total efficiency tofocus on the performance of the mechanical part.The compression ratio of the three-dimensional scrollcan be set at a higher value than the conventionalscrollandare-compressionlossduetotheshortageofcompression ratio is decreased. As a result, substan-tial improvement of efficiency on high-pressure-ratiocondition is obtained. This indicates that the three-dimensional scroll has a special advantage for appli-ances operating under high compression ratio such asheat pump for cold area and refrigeration in additionto air-conditioning. On the other hand, an over com-pression loss on the low-pressure-ratio condition canbeavoidedbyinstallationofbypassports.TheworkingmechanismofthebypassportsisshowninFig.9(b).Incase the operating pressure ratio is below the built-inpressure ratio, the pressure of intermediate compres-sionchambersexceedsdischargepressureandanovercompression loss occurs. By installing bypass portson intermediate compression chambers, the refrig-erant that reaches discharge pressure is released tothe discharge chamber through the bypass ports, andthe pressure of intermediate compression chambers,which is communicated with the bypass ports, is keptat discharge pressure.Figure 10 shows loss classifications based on thecylinder pressure measurements on rated condi-tion (Pd/Ps= 3.4) and high-pressure-ratio condition(Pd/Ps= 6.3). Loss ratio is defined as the percent-age of total loss of the conventional compressor. Thefollowing improvements are made for the developedthree-dimensional scroll compressor.Proc. IMechE Vol. 222 Part E: J. Process Mechanical EngineeringJPME189IMechE 2008Development of a three-dimensional scroll compressor199Fig.9Efficiency improvement of the developed three-dimensional scroll compressorFig.10Loss classifications1. Reduction of indicative loss by the optimizationof compression ratio with the three-dimensionalscroll and the minimization of the leakage loss inthesteps(12percentonratedconditionand26percent on high-pressure-ratio condition).2. Reduction of mechanical loss by miniaturization ofmechanicalpartswiththethree-dimensionalscroll(15 per cent on rated condition and 12 per cent onhigh-pressure-ratio condition).3. Reduction of motor loss by introducing a highefficiency motor (15 per cent).Bytheimprovementsmentionedabove,5.5percentimprovementoftotalefficiencyonratedconditionand12.5 per cent on high-pressure-ratio condition werearchived.5CONCLUSIONSTheefficiencyimprovementtechnologiesinthethree-dimensionalscrollwereinvestigatedandthefollowingconclusions were obtained.1. The indicative efficiency plateaus in the regionwherethestepclearanceissmallduetotheoilseal.2. Theflowcoefficientinthesideclearanceis1.7timeslarger than that in the tip clearance.3. Visualizationtestsgavetheconfirmationthatfillingthe step clearance with oil decreases the leakage.4. Thethrustbearinglossisreducedbydecreasingtheouter diameter and the orbiting radius of scroll.Based on the above conclusions, the authors havedeveloped high efficiency, small size, and lightweightthree-dimensional scroll compressor for commercialair-conditioner, featuring the following, comparedwith the conventional scroll compressor.1. Thirty-five per cent smaller volume and 26 per centlighter weight.2. A 5.5 per cent improvement of efficiency on ratedcondition and 12.5 per cent on high-pressure-ratiocondition.As stated in this article, the authors have producedthree-dimensional scroll compressors for commercialair-conditioner, gas heat pump 2, and refrigerationunitforreefertruck3,4,andplantoexpanditsusageinrefrigerationunits,heatpumps,andautomotiveair-conditioners.JPME189IMechE 2008Proc. IMechE Vol. 222 Part E: J. Process Mechanical Engineering200H Sato,M Fujitani,H Kobayashi,H Mizuno,andT ItohREFERENCES1 Sato,H.,Itoh,T.,and Kobayashi,H.Frictionalcharacter-isticsofthrustbearinginscrollcompressor.SeventeenthInternational Compressor Engineering Conference atPurdue, Purdue University, Indiana, USA, 1115 July2004, paper C027/2004.2 Kimata, Y., Fujitani, M., Kobayashi, H., Miyamoto, Y.,Matsuda,S.,andYamazaki,H.Developmentofhighper-formance R410A scroll compressor for gas engine heatpump.SeventeenthInternationalCompressorEngineer-ing Conference at Purdue, Purdue University, Indiana,USA, 1115 July 2004, paper C027/2004.3 Fujitani, M., Kobayashi, H., Mizuno, H., Itoh, T.,Maruiwa, Y., Shikanai, T., Gotoh, T., and Matsuoka, S.Developmentofenvironment-friendlyscrollcompressorfor truck refrigerator. JSRAE Annual Conference, Tokyo,Japan, 2225 October 2007, paper E315/2007.4 Tanaka, T., Sudoh, M., Kai, M., Osada, K., and Watan-abe, Y. Development of a low environmental loaddirect driven refrigeration unit for transportation. JSRAEAnnual Conference, Tokyo, Japan, 2225 October 2007,paper B313/2007.APPENDIXNotationAareaCflow coefficientCTcondensing temperatureDdiameter of orbiting scrollETevaporating temperatureFforceGmass flowLscroll wrap heightNrotation speedOCRoil circulation ratioPpressureVvolumeWlossclearance at steporbiting radiusadadiabatic efficiencyiindicative efficiencymomotor efficiency?ad/mospecific heat ratiocoefficient of frictiondensitySubscripts0set value of clearance1value at inlet2value at outlet3Ddeveloped three-dimensional scrollcompressorconvconventional scroll compressordvalue at dischargethrustthrust bearingtiptip clearancesvalue at suctionsideside clearanceProc. IMechE Vol. 222 Part E: J. Process Mechanical EngineeringJPME189IMechE 2008