Elasto-plastic analysis of the rotor and wedges supercritical turbo generator

Transcription

1 3rd Iteratioal Coferece o Mechatroics ad Iformatio Techology (ICMIT 06) Elasto-plastic aalysis of the rotor ad wedges supercritical turbo geerator Xigtia Qu,a, Yogbig Zhao,b, Jiabig Cheg3, c,shegyu Wu4, d ad Chaopeg Zhag5,e,,3,4,5 College of Mechaical Sciece ad Egieerig, Jili Uiversity, Chagchu, Chia a quxt@jlu.edu.c, b39585@qq.com, cbglz @63.com, d @qq.com, e 09993@qq.com Keywords: ABAQUS; turbo geerator rotor; wedges; Fiite elemet method; Stregth aalysis; Elasto-plastic aalysis; Stress gradiet. Abstract. Uder the coditio of over speed, the rotor ad wedges of the supercritical 000MW turbo geerator are plastically deformed. By usig the software ABAQUS for rotor ad wedges stregth aalysis, The results showed that the stregth of chamfer at the tooth root of alumium wedges i rotor, chamfer at the ed of alumium wedge shoulder ad chamfer at the sub-groove of ati-maget part i rotor does ot satisfy the requiremets of the positio. The actual stress distributio, plastic deformatio regio ad maximum plastic strai of the rotor ad the wedges ca be obtaied through elasto-plastic aalysis of the rotor ad the wedges. Establish several wedges ad rotor fiite elemet models with differet parameters to those dagerous poits that do ot meet the stregth requiremets respectively, from which we ca fid the effect of each parameter o the stress of the dagerous poit by compariso aalysis. Differet stress gradiets of alumium wedges i rotors result i a larger maximum stress value ad a smaller plastic deformatio regio. The maximum stress value of the rotor decreased with the icrease the chamfer radius. The average pressure at wedge shoulder is ot related to the wedge agle. The maximum stress value of the wedge is sigificatly icreased with the decrease of the radius of curvature at the corer, from which we ca get the best desig. Itroductio The establishmet of electric power idustry has already had a history of more tha oe hudred years, ad the fossil fuel-based steam thermal power geeratio still has more tha 50%, ad this state will ot chage over a period of time[]. I Chia, the productio of the same amout of electricity cosumes 5% coal tha the iteratioal level[]. To solve the problem of power supply coal cosumptio, fudametally speakig, is to optimize the thermal power structure[3,4]. The performace supercritical geeratig uit is reliable, the techology is mature, ad it ca be adapted to the requiremets of coal, so it is importat to develop supercritical geeratig uit i Chia. But the large supercritical turbo geerator rotor is usually about several tes or eve hudreds of tos, the structure are complex, ad rotate at a speed of rpm i the supercritical state of high temperature, high pressure ad superheated steam eviromet. High pressure rotor is maily uder high temperature ad high stress, low pressure rotor ad the geerator rotor are maily uder tremedous cetrifugal force geerated by high-speed rotatio, trasmittig torque ad bedig stresses geerated by its weight. Thus, the workig coditio of the supercritical uit is very poor, ad the safety ad reliability of the power plat is the most critical compoets i all parts of the power plat equipmet. The rotor holds a large proportio of the geerator. The structural desig of the rotor is oe of the keys to the developmet ad desig of the uit. At the same time, its maufacturig cost is high, difficult to retrofit. Oce the rotor failure, the etire uit will be scrapped or paralysis[5,6,7]. Therefore, the fiite elemet method is used to aalyze the structure of the rotor at the begiig of the desig. The stregth aalysis ad the elasto-plastic aalysis of the rotor ad the wedges of the supercritical 000MW turbo geerator are especially importat. 06. The authors - Published by Atlatis Press 573

2 Stregth aalyses Establish the fiite elemet model. I order to facilitate the study, the fiite elemet model is simplified. Superimpose the cetrifugal force of all coils ad the apply a uiformly distributed load at the bottom of the wedges i cotact with the coils. Establish a model oly cosistig of the rotor ad wedges. The structure ca be hadled by plae, so we ca select a cross-sectio of the rotor ad the wedges for aalysis ad calculatio. Establish a cross-sectioal diagram of the rotor ad the wedges show i Fig.. Fig.. Cross-sectioal diagram of the rotor ad the wedges Treatmet of fiite elemet model. Firstly create the properties of materials ad cross sectios,ad the eter the Property Module. Iput the desity, the elastic modulus ad Poisso's ratio of material accordig to the data i Table ad defie material properties of rotor ad wedges respectively. Table. Material properties Parts Elastic Modulus Poisso's Desity Yield limit (N/mm ) ratio (t/mm 3 ) (MPa) Rotor E =.E5 µ = 0. 9 ρ = 7.85E 9 σ = 690 Alumium wedge E = 7.0E4 µ = ρ =.76E 9 σ = 35 Ati-magetic steel wedge E =.E5 µ = 0. 9 ρ = 7.85E 9 σ s = 385 Secodly mesh ito Mesh fuctioal modules, set uit seed size of the rotor (or wedge) i each area ad complete meshig set of rotor ad wedge. Thirdly set the aalysis step, eter the Step fuctio module, the load is divided ito 5 steps, so that the model ca smooth trasitio. The defie cotact, eter the Iteractio fuctio module, defie the cotact surface of the rotor ad the slot wedge, select the two faces of the cotact pair, set the relevat parameters, ad complete the defiitio of cotact. Last defie the boudary ad load, eter the Load fuctio module, defie the symmetry costraits i the X ad Y directios for the rotor respectively, ad apply load to the rotor ad the wedge followig the relevat steps, as show i Fig.. s s 574

3 a) Alumium wedge b) Ati-magetic steel wedge Fig.. Load applicatio of the rotor ad wedge Results of fiite elemet aalysis. Eter ito the Job fuctio module, the stress distributio uder differet workig coditios of the rotor ad the wedge ca be obtaied through the stregth aalysis ad calculatio. From the results after calculatio ad aalysis, there are three poits of the structure do ot meet the stregth desig requiremets, which are located i WAL chamfer ad RAL3 chamfer of the alumium wedge, ad RST4 chamfer of the ati-magetic steel wedge respectively. Elasto-plastic aalysis The elastic ad plastic aalysis of the rotor ad the wedge do ot eed to rebuild the model of the rotor ad the wedge, ad the origial model ca be modified. The mai is to set the rotor ad wedge of the elastic plastic properties ad model load step. Rotor ad wedge material property settigs. Eter ito the Property fuctio module, set the stress at the begiig of the plastic deformatio of the rotor is 640MPa. Iput data to complete the settigs of the rotor material performace. Rotor ad wedge load step settigs. Eter ito the Load fuctio module, select the Load Create, ad apply load to the model as the followig steps: ) Iput the rotatig speedω = 0rad/s. Apply a small cetrifugal force to the rotor ad the wedge to make the model coect smoothly. ) Chage the rotatig speedω = 00rad/s. 3) Apply pressure of coil to ormal ad abormal wedge: P = P = 5N/mm 4) Modify the coil pressure o the wedge: P = 30N/mm P = 0N/mm 5) Modify the coil pressure o the wedge: P = 46N/mm P = 9N/mm Chage the rotatig speed: ω = 39rad/s Apply all the elastic loads. 6) Elasto-plastic aalysis of the rotor ad the wedge model. Modify the pressure of the coil to the wedge: P = 6.N/mm P = 38.N/mm Chage the rotatig speed: ω = 377rad/s Apply all loads. Load icremet is set to 0.. Achieve icremetal loadig, ad the geometric oliearity is set to ON. Aalysis results.after modifyig the alumium wedge portio of the rotor ad the wedge model, eter ito Job fuctio module, ad the stress distributio ad plastic deformatio zoe of the rotor ad wedge ca be obtaied after elasto-plastic aalysis. Fig. 3 shows the results of the elasto-plastic aalysis about alumium rotor. We ca fid that the maximum stress value of the rotor is MPa from Fig. 3(a). The plastic deformatio area of the rotor is show i Fig. 3 (b), with a area of about 0.5mm. The maximum plastic strai is

4 a) The stress distributio of the rotor b) The plastic deformatio area of the rotor Fig. 3.The elasto-plastic aalysis results of alumium wedges of the rotor Fig. 4 shows the results of the elasto-plastic aalysis about alumium wedge of the rotor. From Fig.4 (a) we ca fid that the maximum stress value of the wedge is MPa which does ot reach the admissible stress value MPa obtaied by stregth aalysis. The plastic deformatio area of the rotor is show i Fig. 4 (b), with a area of about 0.00mm. The maximum plastic strai is a) The stress distributio of alumium wedges b) The plastic deformatio area of the rotor Fig. 4. The results of the elasto-plastic aalysis of the alumium wedges Fig. 5 shows the results of the elasto-plastic aalysis about ati-magetic steel wedge of the rotor. From Fig. 5(a) we ca fid that the maximum stress value of the wedge is MPa which does ot reach the admissible stress value744.95mpa obtaied by stregth aalysis. The plastic deformatio area of the rotor is show i Fig. 5 (b), with a area of about 0.66mm. The maximum plastic strai is a) The stress distributio of the rotor b) The plastic deformatio area of the rotor Fig. 5.The elasto-plastic aalysis results of ati-magetic steel wedge of the rotor 576

5 Best desig Whe uder ormal workig speed coditios, the safety factor at RAL3 chamfered of the alumium wedges rotor is less tha., the desig does ot meet the stregth requiremets. Whe uder over speed coditio, the RAL3 chamfered positio of the alumium wedge rotor, the WAL chamfer positio of the alumium wedge rotor ad the RST4 chamfer positio of the ati-magetic steel wedge of the rotor occur yield, the desig does ot meet the stregth requiremets ad eeds to improve the structure Alumium wedge portio of the rotor structural improvemets. Fillet radius at the RAL3 chamfer positio of the alumium wedge portio of the rotor is 4mm, the stress gradiets is large. I order to slow dow the stress cocetratio, the chamfers radius are set to 5mm, 6mm, 7mm, 8mm ad 9mm respectively, the establish a fiite elemet model ad stregth aalysis: The rotor maximum stress value decreases with the icrease of chamfer radius, icreasig the fillet radius could sigificatly decrease the stress cocetratio. Whe the fillet radius icreases to 8mm, the maximal rotor stress is 68.5MPa that is less tha the yield stregth of 690MPa, which meets the desig stregth requiremets. I additio, whe the fillet radius is set to 8mm, the rotor stress maximum value uder work speed coditios is 437.5Mpa. The safety factor is.58, which ca meet the requiremets of the desig stregth. Improvemet of alumium slot wedge structure. The improvemet of alumium slot wedge structure has two ways without chagig the wedge width: chagig the alumium wedge agle or chagig the chamfer radius of the alumium wedge at WAL chamfer positio. Ifluece of wedge agle o maximum stress value. The wedge agle of the slot wedge is set to35, 40 ad 50. Establish the fiite elemet model ad stregth aalysis. At differet values of the wedge agle, the maximum stress value is.96mpa which accouts for 0.86% of total stress, ad ca be eglected. Therefore, the maximum stress values of the slot wedge are ot sigificatly related to the wedge agle of the slot. Ifluece of wedge fillet radius o the maximum stress value. Fillet radius of alumium wedge at Wal chamfered positio is set to.mm.6mm ad.0mm respectively. Establish the fiite elemet model ad stregth aalysis. Wedges maximum stress decreases with icreasig radius of the chamfer. Whe the fillet radius icreased to 3mm, the maximum stress wedge reach MPa that is less tha the yield limit 35MPa, which meet the stregth requiremets. Improved structure of ati-magetic steel wedge of the rotor. Fillet radius of ati-magetic steel wedge at RAL3 chamfered positio is set to 7.mm,8.0mm ad 8.8mm respectively. Establish the fiite elemet model ad stregth aalysis. Rotor maximum stress value decreases with the icrease of the radius of chamfer. Whe the fillet radius icreased to 8.0 mm, the maximum rotor stress reach MPa that is less tha the yield limit 690MPa, which meet the stregth requiremets. Coclusios I this paper, we extracted ad simplified physical model of the rotor ad the wedge. Establish the fiite elemet model ad aalysis the stregth of the rotor ad the wedge by software ABAQUS, the obtai the stress distributios of the rotor ad the wedge uder two differet coditios. The plastic deformatio area ad plastic strai of the rotor ad the slot wedge uder the over speed coditio were obtaied through the model elastoplastic aalysis. By comparig the maximum stress values of the rotor ad slot wedge with differet structural parameters uder the same workig coditio, the optimum desig of the rotor ad slot wedge ad several coclusios were obtaied as follows:. Establish the fiite elemet model ad aalysis the stregth of the rotor ad the wedge by software ABAQUS, the obtai the stress distributios of the rotor ad the wedge uder two differet coditios. The chamfer stregth at tooth root ad shoulder ed of the alumium wedge ad sub slot chamfer of ati-magetic steel did ot meet the desig stregth requiremets.. The actual stress distributio, plastic deformatio area ad maximum plastic strai of the rotor ad the slot wedge uder the over speed workig coditios were obtaied by the elastic plastic 577

6 aalysis. The maximum stress value of alumium wedge is MPa, ad plastic deformatio area is 0.5mm ; the maximum stress value of ati-magetic wedge is MPa, plastic deformatio area is 0.66 mm.i cotrast, the maximum stress value of the alumium wedge is large, but the plastic deformatio area is small, which is caused by the differet stress gradiet. The fillet radius at the dagerous poit of the alumium wedge rotor is 4 mm; the stress gradiet is large. The fillet radius at the dagerous poit of the ati-maget rotor is 6.4mm; the stress gradiet is small. 3. For the dagerous poit of the rotor, chose several groups of differet parameters for stregth aalysis. Comparig the results, a coclusio ca be draw that the maximum stress value of the rotor decreases with icrease of the chamfer radius ad icreasig the fillet radius ca mitigate the stress cocetratio sigificatly. 4. The average pressure of the slot wedge is ot related to the wedge agle of the slot. The maximum stress value of the slot wedge is ot sigificatly related to the wedge agle through the aalysis ad calculatio to the model with differet slot wedge agle. 5. Select ad aalysis differet radius of curvature at the corer of the slot. The maximum stress value is sigificatly icreased with the decrease of the radius of curvature at the corer of the slot wedge by comparig the results of fiite elemet aalysis. I summary, the fiite elemet aalysis of the large turbo geerator rotor ad slot wedge usig ABAQUS software is feasible, ad the aalysis results are basically cosistet with the actual situatio. The fiite elemet method ca also be used i the static aalysis ad dyamic aalysis of other large ad complex parts. Refereces [] K Wag. Research o the life of large steam turbie rotor [D]. Wu Ha: Huazhog Uiversity of Sciece ad Techology, 004. [] Z.P. Sog. Chia Egieerig Sciece00,:-44. [3] G Wag, Ximig Li. Desig, maufacture ad operatio of large steam turbie geerator[m]. Shaghai: Shaghai sciece ad Techology Publishig House, 000. [4] N.S. Hu. Steam turbie equipmet ad systems[m].beijig: Chia Electric Power Press,006. [5] S.H. Huag. Joural of Power ad Eergy, 993, 07(49): [6] V N Shlyaikov, B.V. Iltcheko, N.V. Stepaov. Egieerig Failure Aalysis, 00, 8: [7] W.T. Fu, B.Z. Zhag, B.Z. Wag. Heavy Castigs ad Forgigs, 008(5):