On Performance of a Two Stage Rotary Snow Blower

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Abel Little
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1 On Performnce of Two Stge Rotry Snow Blower?Utsuru Shibuy, Niigt Eugineering Co., Ltd, Jpn Hiroshi Kuriyin, Institute of Snow nd Ice Studies Ntionl Reserch Center for Disster Prevention Science nd Technology Agency, Jpn We mnufctured two types of ugers, screw nd rke type uger nd ribbon screw type uger to further improve the performnce of the two stge rotry snow blower tht is now considered s the most effective remover in view of the diversified nture of snow in Jpn. After instlling ech of them on bse mchine ctully used, we exmined the performnce chrcteristics while chnging revolutions nd snow nture. We lso prepred two blowers (four-blde blower nd five-' blde blower) to exmine their difference. The results of the test re summrized s follows: (1) 3-element ribbon screw type uger ws superior. to 2-element screw nd rke type uger in generl performnce. (2) Snow removing performnce considerbly depends on the combintion between blower nd uger circumferentil speed.. Mximum snow removing cpcity (t/h) is got t such combintion s the blower speed is low, while the uger speed is high in order to increse the cpcity of snow gthering.. Blower high speed is provided to get the distnce of snow ejection. In this cse, low uger speed produces better result. (3) The 4-blde blower ws' superior in performnce to the 5-blde blower. This, however, depends on the volumetric cpcity mrgin of the blower housing. Circumstnces of Snow Removl from Rods in Jpn Jpn is world-fmous for its hevy snowfll. As compred with other snowy countries in Europe nd Americ, it is locted in low ltitudes lying from north to south. The nture of snow, therefore, is diverse becuse the wether condition vries from one region to nother. In Jpn, cold nd snowy provinces ccount for 6 of the whole country where bout one fourth of the totl popultion live. it is, therefore, very importnt to provide proper policy to protect rods from snow nd ice nd to remove snow from rods to ensure smooth trffic in the winter seson in such provinces for industril promotion nd stbiliztion of the people's livelihood. Mechniztion of snow removl from rods in Jpn first strted in In those dys, however, only few mchines were used nd method ws immture. As the demnd for snow removl grew yer fter yer, studies of methods, improvement of domestic mchines, nd proto-type mnufcturing nd reserch were grdully promoted. Thnks to the Jpnese Government's finncil id strted from 1957, vrious projects ginst snow hve been ctively promoted in snowy provinces. As consequence, socil nd economic ctivities in the winter seson hve been remrkbly progressed. However, we will not be fully stisfied until we ttin socil nd economic ctivities in the sme level throughout yer by constructing ALL WEATHERED ROADS in the entire re. The nture of snow is vrious s it.flls, nd chnges in complexity s it lies on the ground under influence of locl wether nd trffic conditions. Therefore, we must remove snow with the nture vrying in fresh snow, lying snow, removed snow, nd snowdrift under vrious rod conditions requiring different methods, such s the rod structure nd trffic volume. So tht mny kinds of mchines re necessry to cope with ny circumstnce conceivble. Clssifiction of Snow Removing Mchines Snow removing mchines re vrious in their structure, pplictions, nd sizes. They re ctegorized into four types below. Snow plough Rotry snow blower Snow loder Others A snow plough is used to remove fresh snow with rpidity, rotry snow blower to remove snow pushed side to rod shoulder s well s in ir fields nd rilrods, nd snow loder to lod snow to dump truck in nrrow rods. These mchines hve been continuously improved in structure nd performnce. Menwhile, rpid expnsionof trffic volume in recent yers brings bout demnd for high efficiency in snow removl. Lrge-sized high-speed snow removing mchines (mx. 800 HP clss) hve been developped to stisfy the demnd. Also pressed snow removers to improve the removed snow qulity nd smllsized mchines (100 HP clss) for sidewlks 185

2 186 hve been developed nd successfully utilized. In Jpn in such bckground, the typicl snow removing mchine in use is two-stge rotry snow blower with 200 to 300 HP engine. It hs only one engine nd the snow removing mechnism is mechniclly driven. Generl Description of Test Specifictions of Test Mchine Model NR652S rotry snow blower ws selected s the bse mchine for the test. The mchine is driven by one engine nd dopts 2-wy system in which the vehicle is driven hydrostticlly during snow removl opertion requiring constnt low speed nd bcking. During trvelling, it is mechniclly driven s generl vehicles. The snow removing system consists of two stges; 'the uger nd blower. Figure 1 shows the ppernce of the test mchine. Model Rotry Snow Blower model NR652S Performnce Mx. snow removing cpcity (bsed on JIS D6509 Test Code of Vehicles with Rotry Snow Blower) 1700 t/h Mx. snow removing width 2600 mm Mx. snow removing height 1800 mm Snow ejection distnce; Snow ejection distnce (m) Running speed; For opertion Forwrd & bckwrd (Km/h) , 0-17 For trvelling Forwrd (Km/h) Bckwrd (Km/h) Figure 1. Appernce of the test mchine. Figure 2. Power trnsmission flowchrt of the test mchine. I- Working system Slowe L ver Auger Reduction Cho Propeller shft J I Clutch Rubber I Power divider I Power is iwy, trnsmitted > During trvelling During snow removing opertion Shift or control lever Byd.rottic trnsmission ---1 Vrible displcement I I 'fl) L_J 1 j Sub - 1ixe displcement ' trnsmission I trnsmission motor I I-- - Propeller shft pe l er Di erentil Shf t gefrf wheelis H_

3 187 Min dimensions Overll length 6,975 mm Overll width 2,600 mm Overll height 3,525 mm Minimum ground clernce 300 mm Weight Overll weight (including 2 crew-members) 12,600 kg Front xle 6,450 kg Rer xle 6,150 kg Weight of vehicle 9,540 kg Weight of snow removing 2,950 kg unit Crew 2, members Power trnsmission Power trnsmission flowchrt is shown in Figure 2. Vehicle Type Front wheel steering, one rer engine Engine Nissn Diesel Engine model RD8T Rted number of revolutions 2200 rpm Rted output 260 HP Mx. torque kgm t 1400 rpm Drive system All wheel drive (4x4) Snow removing system Type Two stge type Auger; Type Number of screw element Screw led (mm) Screw nd rke type Ribbon screw type Blower; Type Figure 4. Tested blowers. Outside dimeter (mm) Depth (mm) 4-blde blower blde blower Blower revolution speed (with engine revolving t 2200 rpm) Speed rnge rpm (circumferentil (14.5) (19.4) (25.7) speed m/s Two types of tested blower re shown in Figure 4. Auger revolution speed (with engine revolving t 2200 rpm) For the test, two uger revolution speeds (High nd Low) were provided by chnging uger driving chin sprokets. 4-blde blower Test Method Tble 1. Test period, nd site 5-blde blower rpm H (circumferentil (6.56) (8.79) (11.7) speed m/s) L (8.75) (11.7) (15.6) Two types of tested uger re shown in Figure 3. Figure 3. Tested ugers. Period Snow Test site Nture of snow density Snow removing I height (Ce) L&Lcs)I. Jn , '77 Nsgok Corse snow - settled 0.36 snow Jn , '77 Ymto Settled snow Feb. 9-16, '77 Spporo New snow Mr , 77 Ymto Corse snow Tble 2. Mesuring items nd instruments. 2 element screw nd 3 elemcnt ribbon scr No. Mesuring items - Instruments 1 Overll torque for Torque meter 1--Dynmic working system (Strin guge I strin guge type) 2 Auger torque Torque meter 3 Number of revolution 1 (Strin guge Grphic of propeller shft for type) meter working system Non contct switch. 4 Oil pressure of hydr-. Pressure guge sttic trnsmission (Strin guge type) 5 Snow density 500 cc Snler, Spring blncer 6 Snow temperture Thermometer 7 Snow hrdness KINOSHITA'S hrdness guge 8 Time Stop wtch 9 Snow ejection destnc Tpe mesure 10 Snow removing height Tpe mesure, Pole

4 188 Test Items. Blower Performnce Test. For ech of 4-blde nd 5-blde blowers, observed the snow suction nd dischrge sttus while mesuring the removed snow quntity. Auger Performnce Test. For ech of 2-element screw nd rke type uger nd 3-element ribbon screw type uger, mesured the removed snow quntities t H-rnge nd L-rnge uger speeds. Horsepower Mesurement. Blower horsepower, uger horsepower, nd running horsepower were mesured with respect to ech test. Snow Qulity Mesurement (Hrdness nd Density). Hrdness of snow ws mesured with Kinoshit's' Hrdness Guge which is outlined below2 A thin circulr metl C (re 5 cm ) is put on the surfce of snow, the hrdness of which is to be mesured. Rod A with cylinder B t its bottom end is set verticlly on the plte C nd cylindricl weight W (m kg) with hole through the center, is dropped from height (h.cm) onto B long rod A. n impulsive force is pplied to snow producing depression of the snow surfce (d cm). The verge resistnce F (kg) which the snow exerts to C Figure 5. Kinoshit's is given by hrdness guge p = m(l + h/d) + M where M is the sum of the weight of A nd C. A 2 The hrdness of snow(hkg/cm ) cn be defined by w c LB H=F/S H = 1 / S(m(l+h/d) + M) Circulr pltes of different dimeters re prepred to h pply wide rnge of snow hrdness, nd to pply to hrd pcked snow, slender cylindricl pieces (bsl re S cm2) re ttched to the cylinder B insted of, plte C. Mesurement of Close Section Are of Snow in front of The Mchine. Combintions. Sites with nturl snow cover were selected for the test. Ech test item ws repeted for following combintions. Tble 3. Combintions. Auger speed Blower Snow remo- Auger type rnge type ving width 2-element Screw nd rke type 3-element Ribbon screw type High Low Test Results nd Comments 4-blde Full (2.6m) 5-blde Qurter (0.65m) The totl number of mesurements throughout the test dded up to 290. The results nd ôoinments re given below. Blower Performnce Rte LB (t/hp. h) LB is the gross weight of snow ejected by the blower in n hour per one horsepower. Theoreticl LB is given by the following formul. 54Qg LB = g: grvittionl ccelertion 2 x B VB: blower circumferentil speed blower volumetric efficiency Fig. 6 shows the reltionships between blower performnce rte LB nd blower circumferentil speed Vi,. The vlue of in the bove formul, therefore, i estimted to be Figure 6. Reltion between blower performnce rte nd blower circumferentil speed. 15 \ \,iest_mdiine o 3H IL 2H A 2L A %A O eqretici curve 'ZOo AI 1St 2nd 3rd BLOWER CIRCUMFERENTIAL SPEED (m/s) Overll Snow Removing Performnce Rte Lo (t/hp.h) Lo is the gross weight of snow removed by the working system (blower nd uger) in n hour per one horsepower. Figure 7 shows the reltionships between Lo nd As generl tendency, in the let speed rnge where V is low, Lo is in proportion to the uger speed wlile -in the 3rd speed rnge where is high, Lo is in reverse proportion to the uger speed. In the 2nd speed rnge, the difference cused by uger speed-difference is minimum. The work efficiencies of different combintions re s follows: 3H> Pe 2H-21, (descending order) Snow removing performnce rte Lo in qurter width s compred with the sme in full width opertion. Blower Qurter width/full width speed rnge 3H - 2H

5 189 The bove tble shows tht under high-speed revolution the snow removing performnce of the 5-element ribbon screw uger drops only 2-8% in qurter width snow removing opertion s compred with full width opertion. Figure 7. Reltion between overll snow removing performnce rte nd blower circumferentil speed. of snow removed. Figure 8 shows the reltionships between R nd U. The generl tendency of the test mchine is different from tht of SR-300 (one stge BEILHACK type rotry snow blower, 800HP). It resembles tht of R500B (two stge rotry snow blower, 500HP) except tht snow removing resistnce tends to stylower. The resistnce R is lrgest in 5H followed with 5L nd 2L in this order. It decreses s the number of screw elements nd uger speed increse. R in two stge type increses s the working speed increses while in BEILHACK type it decreses nd reches the minimum t the working speed of 12 km/h. 0 Figure 8. Reltion between snow removing resistnce nd working speed. De N / [I] Snow. density 022'-'030(g/crT) Test site Snooro U 0. Full Qurte width width ID 0.4.3H 0 1, Snow Iou h I / piqu8l L nge 70 ) 2L A A/I 03 U (One stge /// /// A,/<N \ BEILHACK type rotry w.ei.8hel Q2 --- cr Uj,/, AD U 0.1 oo WORKING SPEED (Km/h) Mximum Snow Removing Cpcity BLOWER CIRCUMFERENTIAL SPEED (m/s) Reltionship between Blower Performnce Rte LB nd Overll Snow Removing Performnce Rte Lo Lo shows similr tendency for different snow density. LB/Lo clculted from the dt in Fig. 7 (for 3H in full width opertion) re s follows: 1st blower speed rnge LB/Lo = = nd blower speed rnge LB/Lo = 5-30 = rd blower speed rnge LB/Lo = 3*25 = LB/Lo for vlues of LB given by theoreticl formul L- BvB2 x7 (7= ) decreses s blower circumferentil speed increses Tble 4 shows such vlues mong the mesured dt tht re considered to be obtined in resonble opertion sttus. The specified mximujl snow removing cpcity of the mchine is 1700 t/h t snow density of P= 0.3. As the result of our test, the mchine recorded over 1700 t/h in full width opertion with 4-blde blower nd 5-element ribbon screw type uger t high speed revolution nd over 1500 t/h in qurter width opertion under the sme conditions. (Snow density P ws ) Comprison between 4-blde Blower nd 5-blde Blower Visul observtionof flying snow t the blower housing outlet told tht the 5-blde blower performnce is slightly more continuous. As to the snow removing cpcity, however the 5-blde blower ws little inferior. In 3H opertion, the snow removing cpcity with the 4-blde blower s ginst the sme with the 5-blde blower is s shown below. Blower speed rnge Full width Qurter width Snow Removing Resistnce R (kg/cm2) nd Working Speed = U (Km/h) 1523 = = Snow removing resistnce R is given s rection force (tyre tngentil force) per cross section re 814 = 1.07 = 1.34

6 190 The 4-blde blower increses the snow removing cpcity by bout 16% inàverge. The rtio of totl blde volumes is: 5-bldes m3 4-bldes = Figure 9. Reltion between blower circumferentil speed nd blower volumetric efficiency., H 2H, A2L The rtio of totl voids in blower housing is: Voids of 5-blde blower (m Voids of 4-blde blower = 0.98 The totl voids in the 5-blde blower re only 2% less. The increse of blde volume of 12.59/6 in the 5-blde blower is considered to be the cuse of reduction of the snow removing cpcity. Tble 4. Dt of mximum snow removing cpcity of the test mchine. Blower type Combintion of uger type nd uger speed rnge Snow deneit (g/cm3) Test site Snow removing cpcity (t/h) FuU width (2.6m Qurter width 1t 2nd 3rd let 2nd 3rd I I I I Full width Snow density, O28($/thi3) "i w Test site Ymto I I I I I I- L.J L.J Spporo , 0.28 Tomto Ngmok blde Ngok Spporo Yto Spporo Tomto Full width Snow density 021'-0304nf) Test Site Spporo 5-blde Tomto Spporo Tomto Running Horsepower Pr (HP) BLOWER VOLUMETRIC EFFICIENCY(%) Blower Volumetric Efficiency 77B l B refers to the rtio of ctul snow removing cpcity to the full blower displcement for unit hour. Figure 9 shows the reltionships between blower volumetric efficiency 71B nd blower circumferentil speed VB. Slower VB produces higher?'jb As VB increses, B decreses becuse the snow drwn into the blower is ccelerted before it reches the depth of the blower. High circumferentil speed, however, is necessry in ctul opertion. As generl tendency, 11B is higher in high uger speed rnge (H rnge) thn in low rnge (L rnge). The rtio of blower circumferentil speed VB to uger circumferentil speed VA is 1.66 in high uger speed rnge, nd is 2.21 in low uger speed rnge. Thus, mtching of VB nd VA is better in high uger speed rnge. Figure 10 shows the reltionships between running horsepower. Pr is smller in high uger speed rnge thn in low rnge. 3-element ribbon screw type uger results in less Pr thn 2-element screw rke type uger. The following sequence shows the descending order of Pr for different combintions. 2L> %2H >3H Reltionships between Pr nd U re s follows: 2L 2H 3H HP7.OU HP=6.2U HP5.5U HP4.5U Rtio between different ugers re: 2L.OU.2U in verge 5H - 4.5U - Rtio between different speedsre: 2H - 5.5U in verge

7 191 = H U Therefore, Psr is more ffected by uger speed thn -J ejr'- - Figure 11. Horsepower distribution between blower nd uger. - - I. Snow site. density Spporo 02200(9,/cm') Figure 10. Reltion between running horsepower nd working speed. 03H 50! 2H A21- AA -" 0 0 C rm I 211 I_ 2L Al Snow density 28m') Test site Ymto SnOW 41jKsS 00. SO Snow density (g/') Test se Spporo,Ngok i 30 OL Full width WORKING SPEED (km/h). 20 Jl I 1st 2n prd ' T, 60 S5C Distribution of Working Horsepower... BLOWER CIRcUMFERENTIAL SPEED (m/s) Figure 11 shows the horsepower distribution bet ween the blower nd uger. Although the fresh snow (P= ) t Spporo nd settled snbw(j'= 0.28) t Ymto re lmost equl in density, power consump Reference tion t Ymto is lrger thn t Sppôro. The rtio - Se±ich KiLnoshjt. The Hrdness of of uger power consumption to overll power comsump Snow(1 ) - Institute of Low Temperture tion is lso lrger t Ymto. These re considered Science,Flokkldo IJnivers±ty,Jpn. to be cused by the difference in the nture 'of Snow S thn by the uger type or speed. en s A , pp

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