Sử dụng dòng điện ion điều khiển đánh lửa trong động cơ xăng

SIJ^ DUNG DONG DIEN ION DIEU KHIEN DANH LU^A TRONG DONG CO XANG TS LE HOAI DUC Bd mdn Bpng ca dSt Khoa Ca Tru&ng Bai Giao thdng Van tdi Tom tdt: Trong dpng co xdng thai diim ddnh lira la mpt thdng sd hit sice quan trgng ddi voi hieu qud cua qud trinh chay Thai diim ddnh lira cd dnh huang toi hau hit cdc thdng sd cd ich cua ddng ca Bdi bdo trinh bay phuang phdp diiu khiin hdi tiip thai diim ddnh lira tren ca so cua ddng diin ion Phuang phdp ndy rdt hieu qud kinh ti vl no sic dung bugi nhu mpt cdm biin di phdt hien cdc hien tugng nhu mat lira, tiing go vd ddng thai cung nhu mpt cdm biin de diiu khiin thoi diim ddnh lira Summary: ^" ^^ engines the ignition timing is an important parameter, among others, for the combustion efficiency The ignition timing affects almost every engine output The present paper describes a feedback scheme based on ionization current The method proposed here is very cost-effective, that is used to utilize the spark plug as a sensor to detect misfire, knock and as a sensor ignition control DAT VAN DE Cac bugi CO the dugc sir dung nhu mpt bd cam bien ddng co Dilu dugc thirc hien bang each dat mpt dien ap len cac bugi va dien ap Ddng dien dugc tao la cac ion khe hd cua bugi, cac thdng sd dugc ggi la ddng dien ion boa Cac ion dugc hinh va sau qua trinh chay, loai va sd lugng ciia cac ion phu thupc vao dac tinh chay Ddng dien ion cQng phu thupc vao ap suat, nhiet dp Tin hieu ddng dien ion la rat giau thdng tin, nhung cung phire tap Viec ddng dien ion dugc thuc hien nhanh chong va true tiep d tirng xi-lanh, khdng gidng vdi phep cam bien thai Tiem nang dieu khien phan hdi la rd rang Bai bao dk cap tdi viec dilu khiln danh lira, hay cu the la gdc danh lira sdm Y tirdng la dilu khiln danh lira sdm dk vj tri dat ap suat cue dai d vj tri tdi uu Cdng mat de nen va truyin nhiet tang nlu danh lira qua sdm, cdng gian no se giam nlu danh lira qua mudn Van de quan trgng la xac dinh dugc moi lien he giua su thay ddi cua ddng dien ion vdi cac thdng tin co lien quan rap chi KHOA HOC GIAO THONG VAN TAI So 33 - 03/2011 117 II NOI DUNG 2.1 Dong CO danh lua (spark-ignited engines - SI engines) Trong ddng co SI, xi lanh dugc dien day bdn hgp nhien lieu va khdng sach, sau dd dugc nen va trudc piston len tdi dilm chit tren, hdn hgp dugc ddt chay bdi cac bugi Nggn liia dugc hinh va phat trien bdn hgp Trong qua trinh chay, ap suit thi xi lanh tang giai phdng nang lugng va cac phan tur mdi dugc tao bdi cac phan ung hda hgc Nggn lua lan truyen tdi vach xi lanh va qua trinh chay dugc hoan tat Trong qua trinh nen, cdng dugc truyen cho mdi chat xi lanh, va thoi gian gian no, nhiet nang ciia chay dugc chuyen cdng co hgc 2.2 Ap suat the xi lanh Ap suit the la mgt thdng sd quan trgng qua trinh chay, vi no tao cdng cua qua trinh chay Hinh la hien thj ba dang dudng cong ap suat Dudng thap nhat la dudng cong nen thuan tiiy, khdng cd qua trinh chay Hai dudng cong cdn lai thi hien biln thien ap suit cd qua trinh chay xay Dudng net diit la bien thien ap suit danh lira qua sdm va dudng net lien ling vdi gdc danh lua sdm tdi uu Thoi diem danh liia tdi uu cdn dugc ggi la tbdi dilm dat md men eye dai (MBT - maximum brake torque timing) Hinh lb thi hien bien thien ap suit xi lanh danh liia qua mudn Early ignition tin'ing Late Ignition tin) ng Crank single Crank angle (a) (b) Hinh Anh hu&ng cua thai diim ddnh lira din cong cua chu trinh 2.3 Dieu khien danh lira Trong dgng co SI, thoi dilm danh lua la mgt thdng so quan trgng cd anh hudng tdi hipu qua cua qua trinh chay, qua dd anh hudng tdi hiu hit cac thdng so d diu cua dgng co Tuy nhien cdc dgng co hipn hiu hit khdng cd h? thong dieu khien hoi tilp thdi dilm danh Ilia, gdc ddnh liia sdm dugc djt trudc hp th6ng Cdc thdng so cd dnh hudng din gdc ddnh liia sdm tot nhit cd thi ke din vi dy nhu: t6c dg d$ng CO, tdi, t:^ l| khdng khf/nhi&i lifu, tinh chit 1^ hda ciia nhien lifu, hp th6ng tuin hodn thdi, nhift dg nude lam mdt, nhift vd dg am khdng Hifn hp thong dilu khiln ddnh liia xdc djnh mgt vai thdng so va dilu chinh gdc danh lura sdm Cdc gdc danh lira sdm dugc xdc djnh thdng qua thu nghipm va hieu chuin giai doan thilt kl cua dgng co Neu tat cd cac thdng so dnh hudng tdi thdi dilm ddnh lua da dugc thii nghiem, vd tinh todn ta cd thi 118 Tap chi KHOA HQC GIAO THONG VAN TAI So 33 - 03/2011 xdc djnh thdi diem ddnh lira tot nhit trudc Tuy nhien, khdng thi va tinh toan cho tit ca cac thdng so, vi no se la vd cimg ton kem dl thuc bien cac phep va thiir nghiem cin thilt Viec thfir nghiem va hieu chuin cho kit qua mgt so gdc danh lua sdm danh nghTa So ddm bdo d mure trung binh, vi no phai dam bdo rang tieng go (hoac kich nd) khdng khdng xdy ra, cQng nhu hieu suit tot tren pham vi toan bg cac thdng so khdng dugc Cac he thong chi hieu chuan tbilt kl ciia ddng co va khdng cd phdn hoi dilu khiln danh lua Mgt cdch tiep can co ban la sir dung dp suit xi lanh nhu cdm biln phyc vy cho dilu khiln ddnh Ilia Nhu da neu d trudc, thdi dilm danh liia (IT - ignition timing) tdt nhit se lien quan tdi bien thien dp suat theo mgt sd phuang an tdi uu Nghien ciiu ITnh vuc da chi ring cac vj tri cho cac dp suat cue dai la gan nhu khdng ddi d gdc danh lira toi uu Thuat todn dilu khien ddnh liira lien quan tdi vj tri dat ap suat cue dai (ggi la thuat todn ap dp suat cue dai) cho ket qua tbdi gian ddnh lua tdi uu dd la vong khoang 2° Thuat todn ciing cho thay thdi diem ddnh lura tdi uu chju dnh hudng Idn ciia cdc thdng sd cd tac ddng tdi tdc lan truyen mang lira, ching ban nhu ty le nhien lieu/khdng va am khdng [4, 5] Do am la can thilt vi nd thi hien Idn nhit dnh hudng cua mdi trudng din thdi dilm ddnh lira toi uu Gia trj tdi uu cho vj tri dp suit cue dai thay doi cimg vdi thilt kl ddng co, tir 12 din 20 dg sau dilm chit tren Anh hudng ciia su thay doi giira cac chu ky den vj tri dat dp suat cue dai vdi ciing mgt gdc danh liia sdm la khdng qua l" Do dd, su sai lech theo chu ky khoang 10° se cho kit qua phdn boi tdi tbdi dilm danh lira la mgt hing so AIT = —AG^^ Vdi AIT - su thay doi thdi dilm danh lira [Spp - goc dat ap suit cue dai mong mudn; 9ppj„ - gdc dat dp suit cue dai dugc Viec ling dung thuat toan dp suit cho dilu khiln danh liia cd'thl hoan thien vl mat cdng suit len tdi 10% va tang hieu suit tdi 5% [7] Tuy nhien dl cbl tao mgt bg cam biln dp suat cd thi chju dugc nhiet va dp suit cao la rat khd khan va vay viec ling dyng thuat toan ap suat eye dai se rit ton kem 2.4 Dong dien ion Trong qud trinh chdy ly tudng, cdc phan tir hydrocarbon phan ling vdi oxy va t?o carbon monoxide vd nude Vi dy phdn ling ly tudng cua isooctane hydrocarbon se la: CgH.s + 27/2 O2 ^ 8CO2 + 9H2O Trong qua trinh chay cQng xdy cdc phdn img khac, qua mgt vai budc trudc chiing dugc hoan Mgt so phdn irng cd mat cdc ion qua trinh chay, vi dy: CH + O -> CHO^ + e" CHO" + H2O -> H3O* + CO ^ C H + C2H2 -^ C3H3" + e": Cac ion dugc tao bdi cac phan irng hda hgc nggn lua Sd lugng ion dugc tao se tang nhiet dp va ap suat tang Dl phdt hien cac ion, mgt ddng dien mgt chilu dugc tao tdi bugi, thiet lap mpt truong dien tir Cac trudng dien tu lam cho cdc ion di chuyen va tao mpt ddng dien ion minh hoa theo so dd dugc the hien hinh 2a Ddng dien dugc tai phia dien ap thap ciia cuon day danh lira, va khdng yeu cau bao ve tir xung dien dp cao danh Ilia, (hinh 2b) He thdng ddng dien ion da dugc su dyng san xuat ddng co vdi muc dich: kiem soat tieng go, phat hien danh lira sdm, mat lua, chat lugng chay Ngoai ra, viec phat hien cac Idi danh lira cung bang each sir dyng cac ddng dien ion V Io:u2a:33:: cxurtar Icmzai'.on cuii«:;* ^ Isnitiou timiu? Meastrement dectrahics ' J) loris^i r IoaiZ3t:cu c\nT«u: -:!/ Voltage ^coTirce aiid curreat iiiea^iifeineiit (b) (a) Hinh Sa do ddng diin ion Ddng dien ion la mgt thdng sd ddng co quan trgng nghien ciru ddng co SI vi nd chira rat nhieu thdng tin ve qua trinh chay Mpt vai thdng icnj3iJ;r artT'c* r*in:er • n XK I>T '/ \r sd anh hudng tdi ddng dien ion la: nhiet do, ty le i_ i^i.!.; -.; ; •• ' i: i i ' i ' ' : ! ; khdng khi/nhien lieu, thdi gian tir chay, tuin hoan thai (EGR), phan nhien lieu, tai ddng CO, va mpt sd thdng sd khac ! • ' 1 ! :,' '1 ' ' V : i? • i Ddng dien ion (hinh 3), cd ba giai doan dac ; trung: danh lira, phia trudc nggn lira va sau nggn ] lua Trong giai doan danh liia, ddng dien ion la Idn, vdi dao cue Do ddng dien cao giai doan danh lira, cac tin hieu dugc se bj ban che Mat cao cua cac ion cimg vdi cac phan irng hda hgc nggn lua tao mdt hoac nhieu dinh ap suat • •J ^ , i ' / " ' - i i ux.- •1 rrt -r •••v-;-~ \.x \ \l h:yiy 111 If : r • , | : I li I' ^i