Cơ sở tính toán quạt gió của máy chữa cháy rừng

- TfS^'^ K H O A H Q C - CONG N G H E CO sdTINM T0(1N QU6T GIO COA MAY CHQA CHAY RLTNG Duang Van Tdi' ) Rimg Id ngudn ldi nguyen qui gid doi vdi ddi song ngudi, song hdng ndm a nuac ta cd hdng n^dn S^^ ^' chdy, nhung thiet bi chUa chdy rimg chit yeu Id thit cong, nen hieu qud chua chdy thdp Do vgy cdn thiet '""y^hdi nghien ciru tgo thiet bi chUa chdy rimg ggn nhe, phii hgp vdi dia hinh rung vd chdt chUa chdy tgi cho De tdi trgng diem cdp nhd nuac KC07.13/06-10 dd xdy dyng dugc nguyen lytinh todn qugt gio cao dp bao gdm: cong thuc tinh todn dudng kinh ciia qugt gio, sd lugng cdnh qugt gio, goc ldp rdp ddu vdo vd ddu cua (jugt, va xqy dyng dudng dgc tinh cua qugt gio Tren ca sd ly thuyet tinh todn qugt gio cao dp ndy, di tdi da thiit ke che^ tgo mdy ehifa chdy rimg bdng site gid, ngt^en ly hogt dgng cOa thiet bi Id: sir d^mg he thong qugt gio cao dp di tgo vgn toe vd luu lugng lan thoi vdo ddm chdy de gidm nong dg chdy, hg nhiit dg cua qud trinh chdy xuong dudi diem chdy thi dam chdy dugc ddp tdt Kit qud khdo nghiim mdy chua chdy rimg bdng sire gio cho hieu qud chiea chdy rimg rdt tot, hi^n thiit bf dd dugc dp dung cdng tdc chira chdy f^g ^ nhiiu d\a phuang cho luu lupng khong Idn, ap lye cao, tidu hao cdng suit nhd, trpng Iupng nho, loai qugt hoan I DAT VAN DE ^ todn cd thd dp dyng vao thilt kl chd tgo may chffa Theo thdng kd cCia eye Kiem ldm hang ndm d chdy riitig bdng sdc gid Vidt Nam co hang tram vy chdy rimg thidu trui hang H D I TirgfNG VA PHirONG PHAP n ^ i n riing, gdy thi?t hgi hang tram ty ding, Idm NGHIEN CUtJ dnh hudng nghidm trgng den mdi trudng sinh thai, 2.1 Dii tu^ng nghien cihi gay tam ly lo nggi cho cdc nhd ddu tu sdn xuit kinh Dii tupng nguyen cuoi la qugt gid cao dp su doanh lam nghidpdyng cho vide thiet ke ehe tgo mdy chiia chdy rimg Vi^c chua chdy rung hi?n d Vi?t Nam chu bdng sue gio yeu bdng thii cong (dimg cdnh cdy dgp) ndn hieu 2.2 Phmmg phap nghien cuu qua chiia chdy rat thap, cdc thidt bj chua chdy nhu - Ap dyng 1^ thuylt tinh todn qugt gid cao dp dd otd cuu hod, binh xit hda chat rat kho th\rc hidn, mgt thiet Igp mo hinh tinh toan, td thiet lap cdng thiie s6 mdy thoi gid nhgp ciia nudc ngodi vd su dyng tinh todn cdc tham so hpp ly ciia qugt gid va xay thi hi$u qua chira chdy thip, kho dgp tdt ddm chdy dyng dudng dgc tinh ciia qugt Xuit phdt td nhu cau bdc thilt hifn cin -Nghidn ciiu thuc ngbi|m dd xde dinh chieu ddi phdi nghidn cuu cai tien, thilt kd che tgo cdc thilt ong thii hpp Vj bj chiia chdyrijmgvdi hi^u qua dgp lira Idn, thiet bi m KET QUA N G H I E N ^ ggn nhp, chat chOa chdy tgi chd, de sd dyng, phii De cho may dgp lira sue gio dat dupc tinh nang hpp vdi dieu kidn dja hinh, didu ki?n kinh tl, de dap lira theo ydu cau, thi vi^c tinh todn thilt ke qugt trang bj rpng rai cho cdc co sd san xuat ^dm nghiep, gid cdn giai quyet hai van dd sau: thiir nhdt, lyra chpn huy dpng nhieu dii tupng tham gia chiia chdy rimg tham so kit cau ciia ban than qugt gid; thd hai, sy dl gdp phan hgn chl di^n tich rung bj chdy phdi hpp giiia qugt gid vd dpng co Do vgy, thilt Vdi I;^ tren.de tai cip nhd nudc; " Nghien kd qugt gio liy Iuu lupng gio d cua va toe dp gio cuu cdng ngh$ va thiet kl chl tgo cdc thidt bi tgi vj tri each trung tam qugt 2,5m (toe dp gid hiiu " chuyen,.(jyng chfta chay rfrng", md so KC07.13/06- hieu), dp tyc gid lam tham s6 dl ddnh gid, can cir " T o T ^ ^ / H d nghien cuu xay di^ng dupc nguyen ly vao cdc nguyen tdc sau dl tiln hanh phdi hpp va toi tinh toan qugt gid cao ap phye vy cho viec tinh todn im boa thdng so cua qugt gid: thiet ke che tgo may chffa chay rimg bdng sire - Lim lupng gid d cira tuong ddi Idn, tic dp gio, kit qua tinh todn thilt kl chl tgo vd khao gio tuong doi cao, hidu suat ciia qugt gid tuong doi nghi$m qugt gid cao dp cho thay logi qugt gid n d y ^ l cao, dp lpc gid Idn; ' TS Truimg D^i hoc Lflm nghi^ c TAP CHf CONG NGHIEP NONG THON • SO - 2012 11 KHOA HOC - CONG NGH$ - Cdng suat tieu hao trdn tryc qugt gid va cdng suat tidu chuan hda (hi^u dung) cua dpng ca tuang doi gan nhau, dong didi nhd ban cdng suit tieu chuin hda cua dgng co, de bdo ddm cho mdy d^ip lira sdc gid Idm vi^c dn djnh ddng tin cay; - Trgng Iupng qugt tuang ddi nhe 3.1 Cac tham s6 ket cau ea ban ciia quat gio Cdc tham sd kit cau chu ylu quyet djnh tinh ndng cua quat gid, gom: Dudng kinh ngoai canh qugt D2, dudng kinh canh qugt Di, gdc cda vao cdnh quat pi, gdc cua cdnh qugt P2, so canh qugt Z, rpng cdnh qugt b|, bj, dg rpng xodn de, dg md rgng A va didn tich vdo gid ciia long bdo ve (hinh 1) K - H e s d , K =3,25-4 Tu thj hinh ta cd nh§n xet sau: - Dudng kinh ngoai cdnh quat D2 cdng Idn thi lim lupng vd dp suat tdng, cdng sudt tryc qugt gid tang, trpng lupng cdnh qugt tdng len; - Ty so D1/D2 Idn thi Iuu tupng, dp lyc vd cdng suit nhd, ty so D1/D2 tang Idn thi Iuu lupng, dp lyc vd cdng sudt dpng ca tang Idn Ty so BifDi liy bdng 0,76 ddn 0,74 la hpp ly nhit Hmh I Cdc tham so kit cdu cua qugt gio 3.2 Tinh toan cdc thong so co ban ciia quat Hmh Cdc tham so kit cdu ciia qugt gio b) Tinh todn goc cua vdo fi/ vd goc cira ^2 cua cdnh qugt a) Tinh dudng kinh ngodi cdnh qugt D2, dudng Tir hinh ta thiy, quat li tdm ddng kinh cdnh qugt D, dupc hiit vao qua ciia hiit di vao tryc chinh Theo kit qua thyc nghidm cho thay, tang qugt li tdm sau dupc canh qugt nen Igi vd gia toe D2 thi keo theo s\f tdng Idn rd ret ciia dp suit dpng den phia ngodi ciing ciia canh quat don nen qua ciJta lyc hgc H e ,Iuu lupng gid d cua va tieu hao eong thoat Do vay, chiing ta gpi phia ddu canh qugt suit trdn tryc quat gio, hi^u suat qugt gid cung dupc phan tilp xuc vdi chit Id dau hut Nhu vgy ndng cao, xac djnh Dj Idn hay nhd, ngoai vide goc ednh qugt d dau hiit dupc gpi la gdc lap rdp can xem xet din tinh ndng ciia qugt gid ra, can diu vdo Tuang tir, diu dupc ggi la dau thoat phdi xem xet din sy phii hpp giira qugt gid vd dgng khi, goc canh qugt d ddu thodt dupc gpi la g6c CO Dudng kinh ciia cdnh qugt Di dnh hudng lap rap dau den Iim lirpng va dp lye gid Nlu giir nguyen D2 Gdc ldp rdp ddu vao Id chi gdc k?p bdi giiia tdng D, thi Iuu lupng tdng Ien, dp luc gidm di, canh qugt ddu vdo vdi dudng tiep tuyen tgi ducmg ngupe Igi nlu gidm Di thi luu Iupng gidm, dp lyc kinh ciia qugt, gpi tdt la gdc vdo ky hi?u Pi tdng len.Quan h^ giira D2 va ty so giiia D1/D2 dupc (hinh 3) the hi?n trdn dd thj (hinh 2) Gdc lap rap dau Id chi gdc kpp bdi giDa cdnh Dudng kinh ngoai D2 dupc tinh theo cdng thuc qugt dau vai dudng tilp tuyln tgi dudng kinh thye nghi?m nhu sau: » ciia quat, ggi tdt Id gdc ra, ky hi?u P2 D2 = ( l , - 1,35 )D, (1)\ Ddi vdi quat li tdm, gdc lap rdp dau vdo pi vd T\\(-f\ p j dudng kinh ciia eanh qugt Dj gdc lap rap ddu p2 Id chi tieu quan trgng quyet dupc tinh theo cong thurc sau: djnh hinh dgng co ban cua cdnh quat Can cu vdo hinh dgng, can cd vao trj so Idn, nhd ciia gdc Pz md (cm) D| = (2) phan cdnh qugt li tam thdnh dgng: - p2 > 900 : canh cong vd phia trudc (hinh 3a); Trong dd: - v§n tic gdc cua cdnh qugt - p2 < 900 : cdnh cong vl phia sau (hinh 3b); (Radian/gidy) - p2 = 900 : canh huang kinh (hinh 3c); Q - Iuu Iupng cua qugt, mVs gio [ ie 12 TAP CHf CONG NGHIEP NONG THON - SO - 2012 KHOA HQC - CONG NGHE Hinh Tham so gdc idp rdp ddu vdo vd gdc lap rdp ddu cdnh qugt a C^h cong trudc; b Canh cong sau; c Cinh hir6ng kfnh Cl, C2: Toe dp myet doi cua ddng tgi ddu vdo vd ddu ra; Ul, U2: Toe dp ddi ciia dudng kinh va dudng kinh ngodi cdnh qugt; Wi, W2: Toe dp tuong doi ciia ddng tgi ddu vao va dau ciia cdnh qugt; C2u: Toe dg ddi tgi diu * Xet dnh hudng cUa hmh dgng cdnh qugt doi vdi tinh nang qugt - Cdnh cong trudc (hinh 3a): cd gdc cda gio j32 > 90", do md tgo ndn toe dp ddng tgi dau cua cdnh qugt C2U Idn han toe dO ddi dudng kinh ngodi cdnh qugt U2 tgo nen, tdc C^u > Uj Nhu v§y, ta thu dupc luu lupng vd dp lyc cua chit kht tuang doi cao Nhung t6c dp tuydt ddi dong tgi diu eiia canh qugt C2 rit Idn, ddn ddn ddng thdi manh li^ tgo nen ddng xody, cho ndn hidu xuat tuong doi thap, dong thdi gay ndn tilng on tdn - Cdnh cong sau (hinh 3b): gdc cura gid p2 < 90", ndn hi$u suit cao, tilng on bd nhung tic dp dai Cju tgi diu ciia ddng nhd han tie dp dai dudng kinh ngodi canh qugt uj tgo ndn, tuc Cia < U2 Do dd tgo ndn toe dg tuy?t dii cOa ddng tai dau C2 tuang doi be, vgy muon dgt dupc ap lyc va luu Iupng nhu qugt cdnh cong trudc thi yeu cau dudng kInh cdnh qugt phdi tuong dii Idn, nhu vgy kich thude ciia nd phdi Icm hon logi qugt cdnh cong trudc - Cdnh hudng kinh (hinh 3c): Id eanh co gdc p2 = 90", ma ldm cho toe dg ddi ciia ddng tai dau C2U bdng tic dg ddi dudng kinh ngoai cdnh qugt U2 tgo ndn, ti>c Id C2U = U2 Vdi logi canh qugt ndy tgi dudng vdo khdng gdy nen ton that va dgp, tinh ndng ciia nd la tmng gian cua hai logi tren ?V (Dl Chieu cao dp lyc cda qugt ly tdm dupc tinh theo I cdng thuc sau; / H, _U^.Sin/3 if^,;;.yt(mmH20)(1^ g.Sinia-\-f72^7 ) Tii cdng thiirc tinh dp lyc quat gio (4) ta thdy gdc pi vd gdc p2 anh hudng Idn din vdn toe eiia ddng khi, kit qud nghien cii^ thyc nghign cho thiy ^f^ gia trj toi uu ciia gdc pi= 60° va gdc P2= 130° cho vgn tic ddng Id Idn nhit * £fra chpn dpng cdnh qugt Nhu phan tich d trdn qugt co cdnh cong trudc cd nhieu uu diem nhung nhupc Idn nhit la hi^u suit thdp, nhung vdi logi qugt dung chOa chay cd cdng suit nhd nen nhupc dilm khong dnh hudng Idn din tinh ndng ciia mdy D I khdc phye nhupc dilm ta thiet kd cdnh qugt hdn hpp (canh chii S) c) Tinh todn sd lugng cdnh qugt So Iupng cdnh qugt cd anh hudng rdt Idn den cac chi tidu ve dp lyc, luu lupng, hif u suit cda quat Sd Iupng qud it, thudng lam cho goc khuyech dp md rpng de lam cho su phdn tang d dau ngodi ciia ddng khi, liic dp lyc, Iuu lupng vd hieu suat deu giam di Sd Iupng cdnh cang tang, cdc chi tidu tren deu tang, nhung sau so lupng cdnh da vupt qua so Iupng nhdt djnh Igi Idm cho cac chi tieu bj giam di Bdi vi so canh tdng Idn Idm cho dp ddi tuang doi cdnh tang theo, lam giam di dp nghieng cua ddng tgi dau ciia cdnh quat, lam tdng co hgi truyen tdi ndng Iupng ciia canh qugt doi vdi ddng Do md ldm tang dp l\rc vd luu lupng cua may qugt Mgt khac so canh qud nhilu se lam cho ma sat giira cdnh qugt va ddng tang Idn Nhu vgy, trd lyc tdng dan den dp lyc va luu lupng gidm di Cho nen so Iupng canh qugt cd mpt gia tri TAP CHf CONG NGHIEP NONG THON - SO - 2012 13 KHOA HQC - C N G NGHE tdi uu Gia tri tdi uu ciia sd canh qugt cd thi thdng qua mat dp cdnh qugt (ao) ^ bieu didn: ^.=J (5) Trong do: /;- Dp dai eung cua cdnh, mm; U = — g ^ t - Budc canh trung binh, mm; (6) 12 Trong do: D|- Dudng kinh diu vao canh qugt, mm; D2- Dudng kinh diu cdnh qugt, mm; Z - So cdnh qugt Thay cdng thdc (6) vao (5) ta dupc: ;r(A+A) hay 2/, Mat dp cdnh qugt (ao) cd the lay gjd tri tu 1,2 d) Tinh todn hi rgng (ddu vdo) hi vd be rgng (ddu ra) bj cua cdnh qugt Trong dilu ki^n khdng thay dii cdc tham sl cua cdnh qugt Id (Du D2, Pi, P2, Z, ), ndu bi qud Idn thi didn tich dudng cira vao va cira qud Idn, ton that ddng xoay tdng len, dan den hi^u suat se gidm xuong Ngupe Igi, neu bi qud nhd, thi luu Iupng tuong doi nhd, idm hgn chl vi$c tdng luu lupng gid dau Be rpng diu vao b| ciia qugt gio tinh theo cdng thurc sau: b, ^ (m) (8) Trong do: S - Chilu ddy ciia cdnh (mm); C - Vdn tic is mi?ng cita (m/s); U - Vgn toe vdng; (m/s); Q - Luu lupng khong khi; ni3/s Z - So cdnh quat ^ - HI so xody cua ddng ( ^ = 0,2 - 0,4) Vgn toe (C) tgi ciia dupc tinh theo cdng thuc C= 2-^^w (m/s) hd - Ap lye dpng hpe tgi ciia ra; kg/cm^ p Khoi Iupng ri^g ciia khdng khi, p=l,02 Vgn toe vong (U) dupc tinh theo cong thijrc sau: (9) (m/s) (10) D I khdng khdng bj tin that d dau be rgng diu ciia qugt gio phai tinh todn eho tuang thieh Be rgng dau b2 dupc tinh nhu sau: 71 Dl b | = JT D2 b2 hay bj= -^—^ D2 (11) e) Chieu ddi ong thoi Chieu dai ong thdi dnh hudng den luu Iupng, vgn toe va dp lyc khdng d mi^ng ong thoi Ong thii cdng ngdn thi tdn that cang it, nhung ydu cau ve eong ngh^ chiia chayriJmgthi ong thii phdi cd dp ddi dii Idn de ngudi chiia chdy tilp cgn ddm chdy Do v^y vi^c xde djnh chilu ddi Ing thii hpp ly dupc chiing tdi nghidn ciru bdng thyc nghidm Cong thuc tinh tdc dp gid tgi vi tri each tdm qugt gid 2,5m la: 0,967-K, ^^.^"^T^ ^ + 0,29 ti2) ^0 Trong dd: Vo - Tdc dp gio tgi ciia ong gid (m/s); s - Khodng each tur cua ong thoi den chd cdeh tdm quat gid 2,Sm (m); e - H? so nhilu logn: e = 0,05 ~ 0,06; ^ Tir cdng thuc (12) co the tinh dupe chieu ddi ong thoi, dudng kinh mieng ong thii dl vgn toe cu'a dgt ydu cau 3 Dudng ddc tinh cua mdy quat gid de chiia cbay rung Tham so tinh ndng chCi yeu cua qugt H tam bao gom: luu lupng Q, ap lyc P, hi^u suit TJ vd cdng suit N, giiia chiing cd thi dung thj bieu diln Hmh Id dudng d$c tinh cua qugt cao kp chiia chdy rimg vdi vong quay nhat dinh, ta cd the bieu didn dudng cong quan hp P - Q (dp lyc - luu lupng), y\ Q (hipu suit - luu lupng) va N - Q (cdng suat - luu Iupng) Tii hinh co thi thay, canh cong trudc cd dudng bieu diln P - Q Id hinh ydn ngua; Dudng cong q - Q hai thap hon so vdi canh cong sau, hifu Trong do: 14 TAP CHI CONG NGHlgP NONG T H O N - SO - 2012 KHOA H p e - CONG NGHE suat cao nhat ndn gan vdi luu Iupng thilt ke Khi luu lupng Q qua be ht^c qua Idn s\r gia tdng tin that xung kich, tdn thit rd ri diu Idm cho hipu suat gidm xuong, dudng cong N - Q thi tdng len Dudng cong P - Q ciia canh cong sau cd dgng Parabol, TI - Q dudng cong cd dgng tuong ty nhu cdnh cong trudc, chi vd trj so hoi Idn hon cdnh cong trudc, cdng suit N cd quan h? vdi P, Q va T^ Khi Iuu lupng Q bdt diu tang, cdng suit cung se tang theo, md Iuu Iupng Q khdng ngimg gia tdng, sy hg xudng cua hidu suit TI va sv gidm bdt ciia dp lyc P, cdng suat N ciing gidm theo gio tot chua chdc da tgo nen mpt chile mdy dap lira sue gid tot, ma can thilt phai gidi quylt vi^c phoi hop giua quat gid vd dpng co, bao gdm lya chpn dung dilu kien lam viec cua mdy dap lii-a bang siie gio Nguyen tdc cua su phii hpp la chpn dieu ki$n lam vide thod man ydu cdu sau: - Bdo ddm dp idm vifc tin egy ciia cd mdy, dgc bidt Id sy Idm vi^c tin c^y vd on djnh ciia dpng co, vay khong dupc nang cao so vdng quay cua canh qugt; - Chi tidu vl Iuu Iupng gid vd toe dp gid tit; - Cdng suit cua dpng ca cdng nhd cdng tit; - Trpng lupng ciia dpng ca cdng nhd cang tot Hiai>uit>i /l' IV KET LUAN AplucP Cinh eong Uwic s^:^^Z -^^-~