KHOA H O C - C O N G NGHE Tap Chf GTVT 7/2012
ID
NGHIEN cufu PHAT TRIEN HE THONG DIEU KHIEN CUNG CAP KHI HOA LONG (LPG) CHO DONG CQf DIESEL 1 XI LANH SUf DUNG LITONG NHIEN LIEU LPG/DIESEL
Tdm t i t : Bii bdo trinh biy kit qui nghien cffu phit then hi thd'ng diSu khien phun LPG trin dUdng nap cOa ddng ca diesel 1 xi lanh A VL 5402 sU dung ludng nhiin liiu LPG/diesel. Vdi viec phat triin bp dieu khiin cung cap LPG (ELC) va phin mem dieu khien kit nd'i vdl may tinh, cd the tinh toan xay dffng bp thdng sd tdi Uu dieu khien phun LPG mdt each di ding theo tdc dd vi tii trgng, tU dd xac dinh dffdc ty li LPG tot ffu d cac che dp lim viic cua ddng cd. Vdi ip suit phun LPG bing 1,5 bar, kit qui thff nghiem trin dffdng dac tinh ngoit (100% tai) cho thiy od thi sU dung LPG trin dpng CO diesel vdi ty le thay the len tdi 30%>, d tdc dd thip fjj li thay thi cd the cao hdn Vdi ty le thay thi LPG ndy, tdng IUdng tieu thtj nhien lieu dtesel-i-LPG nho hdn so vdi sff dung ddn nhiin lieu diesel, dong thdi do rung ddng cua dong cO cung tang lin khi tang ty Ip LPG.
Abstract: This paper presents the results of study and development of an electronically controlled LPG injection system on the A VL 5402 one-cylinder diesel engine fueled with dual fuel LPG/diesel. V\/ith the devel- opped electronic LPG control unit (ELC) and control software, it is easy to determine and establish a set of optimum control parameters of LPG injection under dif- ferent engine loads and speeds. This helps to deter- mine the appropnate proportion of LPG in total dual fuel LPG/diesel consumption under different engine op- erating conditions. The LPG injection pressure is 1.5 bars. Under the engine full load performance, the ap- plicable proportion of LPG can be 30%; under low en- gine speeds this proportion can be even higher. The study also indicated that the total dual fuel consumption IS less than fuel consumtion in the case of using single fuel of diesel; the engine vibration increase with in- creasing LPG proprtion.
Keywords. Diesel engine, LPG/diesel dual fuel.
Electronic LPG control, conversion to LPG/diesel.
1. Gidi thieu
De giam fi n h i l m mdi trufing do cac phuong lien giao thdng gay ra, cd the ap dung cac giai phap nhu tdiuu hda t h i l t k l ddng cd, nang cao chat IQdng nhien lieu truyen thdng hogc dung nhien thay t h i (LPG, CNG, cdn, dau thuc vat, biodiesel, hydrd, DME ...) [1].
Trong dfi vide nghien cQu sd dyng LPG lam nhien lieu thay f h l cho dfing cP fi td dang rat dugc quan tam, LPG la hfin hpp cac hydrocarbon nhe, chii y l u la
ThS. NGUYEN TUONG VI Trtfdng Cao dang nghe Cong nghiep Ha Ngi
ThS. NGUYEN THE TRl^C PGS.TS. HOANG DJNH LONG
PGS.TS. LE ANH TUAN Trtfdng Dgi hgc Bdch khoa Hd Npi propan {C^HQ) va butan (C4H1Q) dUpc lay tU thien nhien d cac md dau, mfi khi. LPG cung cfi the dupc san x u l t d cac nha may lpc d i u trong qua trinh chung cat dau thd[2, 3]. LPG la loai nhien lieu it gay fi n h i l m , da dUdc nghien cUu va sQ dyng nhieu tren ddng cO xang d cac nQdc [4] cung nhu fi Viet Nam [5],
Ddl vdi cac phuong tien giao thdng trang bi ddng cd diesel, do sd lupng ngay cang tang va sQ phat t h l i ddc hgt ciia ehitng, viec nghien cdu sQ dyng nhien lieu LPG thay t h i de gtam phat thai cung dang dugc quan tam, dge biet la phuong phap sQ dyng nhien lieu LPG thay t h i mgt p h l n diesel [6, 7, 8]. Vdt phUdng phap nay, LPG dUpc cung d p vao dufing ngp cua ddng cd, cdn nhien lieu diesel van dUdc phun binh thudng vao trong xi lanh dgng eg nhung vfii iQgng cap g i l m dt. Viec dmh iQpng LPG phun vao dudng ngp ddng Cd b i n g each t i l t luu qua giclp da dupe nghien eUu tren ddng cd xe buyt D1146T1 tat Phfing thi nghiem Dfing cd ddt frong - Dgi hoc Bach khoa Ha Ndi [7]. Trong nghien cQu nay, lugng LPG thay the -diesel d cac c h l dp lam viec ciia ddng cd g i n nhu khfing doi vi vay rat khfi dieu chtnh tdi Uu ty le LPG thay t h i diesel fi cac c h l do lam vtec khac nhau cua dgng cd, vi vay, khdng dem lat hieu q u i cao. Do vay, c i n p h l i nghien cQu dieu chtnh IQOng cung d p LPG va ty le LPG/diesel cho phu hpp vfii cac che dfi lam viec ciia ddng cd d l dgt dUdc tinh nang kinh te ky thugt ciia ddng cd.
Bai bao trinh bay k i t q u i nghien cUu phat tnen he thdng d i l u k h i l n cung cap LPG tren ddng cd mdt xi lanh AVL 5402 va danh gia I n h hufing ciia ty le nhien lieu d i n linh nang kinh t l , ky thuat cung nhQ phat t h l i eiia dfing cd. Viec nghien cdu dUde thyc hien bang thyc nghiem tgi Phdng thi nghiem Dong cd dd't trong, trufing Oai hpc Bach khoa Ha Nfii.
2. Thie't ke he thd'ng cung cap LPG 2.1 Sa do lip dat he thdng cung cap LPG He thdng cung cap nhien lieu LPG dUdc gidi thieu trong bai bao ciia tac gia N g u y i n Tufing Vi [13]. LPG dupc tich trong binh chQa chuyen dimg va dugc ban fi ngoai tht trufing, Tren binh cfi van ddng mfi LPG dgng cd khi vfii cP eau van xoay. Viec dieu chinh ap suat LPG trong qua trinh thi nghiem dupc thgc hien b i n g van g i l m ap dang cd khi. LPG dUdc hfia hoi hoan loan qua bd c h u y i n ddi hda hdi trudc kht vao ddng cd. Tren dufing cung cap LPG cho dfing cd cdn
i KHOA HOC - CONG NGHE
co cac cam bien do nhiet dd. ap suat va luu luong LPG. De qua trinh do luu luong LPG dUpc chfnh xac, tren duOng dng cap nhien lieu LPG co lap them binh dn ap phia sau cam bien do luu lugng, LPG duoc phun vao dUdng dng nap cua dfing cP qua vdi phun, Cac tin hieu tu cam bien toe dp, cam bien nhiet do, cam bien luu lupng, d m bien chan ga, d m bien ap suat,,.. dUPc dua ve bo dieu khien he thdng cung cap nhien lieu LPG (ELC - Electronic LPG Control), Tin hieu dieu khien phun LPG dUPc gQi tpi van dien tu dfing ngat nhien lieu dat phia trUdc bfi hfia hOi va tin hieu dieu khien voi phun. Qua trinh dieu khien cung cap LPG dUPc thuc hien thdng qua giao dien cua may tinh ket ndi vfii bo ELC,
2.2 Thiet ke mach dieu khien phun nhien lieu LPG (ELC)
86 dieu khien ELC [10] (Hmh 1) bao gom: Khdi mach ngudn, khdi ghi nhan tin hieu tu cam bien, khdi vi xil ly, khoi dieu khien co cau chap hanh va khdi ket ndi vpl may tinh.
Hinh 1. Bp ELC dieu khien he thdng LPG 2.2.1 Khdi mach ngudn
Khdi mach ngudn co nhiem vu tao ra dien ap 5V cho ELC, IC on ap LM7805 cfi tac dung chuyen ddi dien ap 12V thanh dien ap 5V. Trong mach nguon cdn bd tri cac tu va dien trfi dd san p h I n g nhQng dao dpng dien ap nhd va cac didt bao ve mach.
2 2.2 Khdt ghi nhan tin hieu cam bien Khdi ghi nhan tin hieu cam bien bao gom: Tin hieu cam bidn tdc dp: Luu luong, ap suat va nhiet dp LPG:
luu lupng va nhiet dp khi nap: Tin hieu tu cam bien chan ga va tin hieu khfing tai. Cac tin hieu nay dupc gQi ve vi xil ly thong qua mach chuyen ddi dd xac dinh gia tri dien ap tuong Qng theo dac tinh cam bien.
Ddng thdi, trong qua trinh lam viec co the lUa chpn che dd ddn nhien lieu hay ludng nhien lieu thdng qua cong t i c ON/OFF LPG,
2.2.3 Khdi dieu khiin co ciu chip hinh Khdi dieu khien cO cau chap hanh bao gdm cac tin hieu dieu k h i l n voi phun va van dien tQ, Tin hieu dieu khien tu vi xQ ly thong qua dieu khien ddng mo transitor 1RF540N, khi transitor thdng mach se cho phep ddng dien 12V di qua euon day va sinh ra luc dien tu de mfi voi phun va van dien tu.
2.2.4 Khoi vl xu ly
Khdi vi xu ly tren Hinh 2 bao gdm: 1 vi xu ly loai Atmega32 ciia hang Atmel, mach tao xung nhip dao ddng thach anh ben ngoai va mach reset vi xu ly khi
bat dau lam viec Vi xu ly cho phep lap tnnh cac thuat toan nhan tin hieu tu cam bien va tint" toan dua ra tin hieu dieu khien co cau chap hanh phu hop voi che do lam viec cua dong co
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Htnh 2 Khoi vi xu ly
2.3 Giao dien dieu khien cung cap LPG Giao dien dieu khien he thdng nhien lieu LPG n h i m hien thi cac thdng sd cua cac d m bien va dieu chinh iupng phun nhien lieu, thay ddi thfii diem phun, bat t i t cac cdng tac... Giao dien dieu khien cho phep thay ddi cac chuc nang sau: Dieu chinh luong phun va thfii diem phun LPG; Hien thi cac tin hieu tQ cac d m bien nhQ; Cac chuc nang ON/OFF; Thuc hien qua trinh do va ghi lai ket qua ciia phep do.
2.4 Luu dd thuat toan va chuong trinh dieu khien he thdng cung cip LPG
Trong de tai, nhom tac gia da xay dyng cac thuat toan nhu: Thuat toan doc gia tri tdc dp dpng co. thuat toan doc gia tn cac cim bien tin hieu tuong tU, thuat toan dieu khien hit ndi may tinh. thuat toan dieu khien vdi phun.
Trong thuat toan dieu khien voi phun, lUpng nhien lieu phun trong qua trinh thi nghiem dUPc thay doi bang each thay ddi dp rpng xung phun thdng qua mach dem lap trinh. TQc la khi da xac dinh gia tri so cua iQPng nhien lieu phun va khi cd xung dieu khien phun thi mach dem xung nhjp se d i m cho tfii khi dat dil gia tri so b i n g gia tri dieu khien ra. Khi b i t dau dem cung la khi nang xung dieu khien phun va khi gia trj d i m b i n g gia tn dieu khien ra cung la liic ha muc xung dieu khien phun xudng.
Thuat toan dieu khiin chung
Hinh 3. So do thuat toin dieu khien chung LPG
KHOA HOC - CONG NGHE Tap Chi GTVT 7/2012
K
Thuat toan d i l u khien chung he thdng LPG dupc the hien tren hinh 13 Qua trinh phun LPG chl b i t dau khl nhiet do ddng cd Ifin hdn 50°C d l d i m b i o nhien lieu LPG hfia hoi hoan toan. Mfii che dfi hogt dgng eua ddng cd duge dac trung bdi mdt bien trgng thai. Khi bien dUOc dat len trang thai ON, ELC se tu dgng chuyin xudng chuong trinh didu k h i l n lUpng nhien lieu phun fi c h l dp dd. Khi b i l n trgng thai dat xudng mUc OFF, ELC se tU dong thoat khfii chUdng trinh cu va chuyen d i n chUdng trinh cfi b i l n trang thai ON khac.
Khl khfing cfi b i l n trang thai nao fi mUc ON, ELC se chuyen sang trang thai chd (bat khoa dien nhung khdng phun nhien lieu LPG) cho d i n khi cfi mfit bien trang ttiai O/Vdugc dua ve bfi dieu khien ELC.
Ngoai ra, trong de tai nay nhfim tac gia cdn cd cae thuat loan dieu k h i l n fi cac c h l do khac ciia ddng cd nhQ :Thu&t toan d i l u khien d c h l do khdng tai va cac che dd chuyen tiep khdng t l i - cd t l i ; cd t l i - khdng tai
ChUdng trinh dieu khien
ChUdng trinh d i l u k h i l n trong vi xd ly dQdc viet b i n g ngdn ngd l$p trinh C tren p h l n mem CodeVisionAVRva giao didn k i t noi vi xd ly vfii may tinh dQdc lap trinh tren phan mem Borland Delphi [11,12].
3. T h d n g h i e m va d a n h gia
De danh gia k h l nang hoat ddng cita bd dieu khien cung d p LPG ( ELC) eung nhu sQ phdi hgp cung cap giQa bd ELC va ECU dgng cO theo cac chd do lam viec, nhdm tac gta da thQ nghiem danh gia I n h hufing ciia ap s u i t phun LPG d i n phat thai cua dfing cd, tQ dd IQa chgn ap suat phun tdi Uu la 1.5 bar [13]. Odng thdi, thQ nghiem thay ddi IQpng LPG thay t h i theo cac c h l do lam viec ciia ddng co va danh gta sU I n h hudng ciia nfi d i n tdng lupng nhien lieu tieu thy va dfi rung ddng ddng cd.
3.1 Trang thiet bj va nhien lieu
3.1.1 Nhiin lieu thff nghiem Nhien lidu diesel thi trudng cd ham IQdng luu huynh theo tieu chuan la SOOppm, LPG dupe chUa trong binh chUa vdt ap s u i t 7bar cd ty Id v l f h l tich cua propan/butan la 40,25/59,75,
3.1.2 Thiit bi thff nghiem Trang thilt bi thQ nghiem gdm bang thd dten AMK cd mdmen Ifin nhat la 105 Nm, cdng suat Idn nhat la 45 Kw va td'c dp bang thay ddt tQ 0 d i n 8000 vg/ph; thief bj do tieu thy nhien lieu AVL733S; til phan tich k h i C E B 11. Thanh phan C Q v a CQ2 dugc do bang phUong phap hap thu tia hdng ngoai (NDIR), thanh p h l n NOj^do bang phUOng phap quang hfia (CLD), thanh phan HC xac d j n h ^ b l n g phQdng phap ion hfia nggn IQa (FID). 0 6 khdi ciia khi I h l i dQpc xac dinh qua do den cua giay Ige b i n g t h i l t bi AVL Smoke Meter 415.
3.1.3 Dpng cd thd nghiem Ddng cP nghien cUu AVL5402 s d dung he thong nhien lieu CommonRail vdi cac thdng sd ky thuSt: dufing kinh xylanh 85 mm, hanh trinh 90 mm t h i tich cong tac 510,7 c m ^ ty sd nen 17,3:1, cdng suat dinh mdc 9Kvj 6 tdc do 3200 vg/ph [9].
3.2 Quy trinh thi> nghigm
T h d nghidm theo phUdng phap ddi chQng dd'i vdi dgng cd sd dung hoan toan diesel va ludng nhien lieu LPG/diesel. A p suat phun LPG sau khi nghien cQu, phan tich tdi uu theo thanh phan khi t h l i ndn dUdc
giQ cd d|nh 1,5bar trong sufi't qua trinh thQ nghiem.
D i l u khien ELC d l thay doi ty le LPG thay t h i cho nhien lieu diesel fi cac c h l do thd nghiem ddi vfii dfing CO nghien cUu, Qua trinh thQ nghiem xac dinh ty le nhien lieu LPG khi ddng cP sQ dung lUfing nhien lieu diesel/LPG dUde t i l n hanh theo dufing dgc tinh ngoat (100% t l i ) ciia ddng cO, d i m bao mdmen cua dfing CO fi 2 trQfing hop sd dyng nhien lieu diesel va lUfing nhien lieu diesel/LPG la nhu nhau, ddng thdi khfing gay ra hien tupng kich nd cho ddng cO.
ThQ nghiem danh gia anh hufing ciia ty le LPG thay the d i n den dp rung ddng ciia dfing cd.
3.3 Kit qua thd nghiem
He thdng dieu k h i l n cung cap LPG cho phep thay ddi iupng LPG thay the diesel thong qua viec thay ddi thdl gian mfi vdi phun, ty Id thay the len d i n 54% theo IQng c h l dp lam viec eiia ddng cd,
3.3 1 Anh hudng cua ty li LPG de'n IUdng tieu thu nhien lieu
Ty le LPG dupe tinh thdng qua ty le giam diesel khi sd dyng ludng nhien lieu diesel/LPG fi c h l dp thQ nghiem cung mdmen vdi khi sQ dyng chi nhien lieu diesel va xac djnh theo cfing thQc:
%LPG =
Trong dfi: %LPG - Ty Id LPG fi c h l dp Ihd nghiem;
B H D J M O O % ) - LQpng tieu thy nhien lieu diesel khi sQ dung ddn nhien lieu diesel; B H ^ j p u a i j - Lugng tieu thy nhien lieu diesel khi sQ dyng diesel/LPG,
K i t q u i trdn hinh 4 cho thay, khi ddng cP sQ dyng ty le LPG fU 20% trfi len thi tdng lUPng tieu thu nhien lieu Diesel+LPG it hpn so vfii trUfing hpp sd dyng ddn nhien lieu diesel; vdi ty le LPG 40%, mdc g i l m dat fdi 12,82%, Nhu vay xet ve chi tieu kinh t l , neu gia nhien lieu diesel va LPG nhu nhau thi khi sQ dung lUPng LPG thay the khdng nhd hdn 20% cho phep t i l t kiem dupc chi phi nhien lieu.
Hinh 4. Lugng tieu thg nhien ligu d cac ty lg LPG khac nhau
3.3.2 Anh hUdng cua ty li LPG din do rung dpng cua ddng cd
Vdl ty le LPG 10%, k i t qua hinh 5 cho thay bien dp rung ddng Ifin n h l t ciia ddng cd cao hdn 2 5 % so vfii khfing cfi LPG. Khi ty Id LPG la 2 0 % bien dfi rung ddng Idn nhat ciia ddng cd A KAcc cao hpn 141,67%.
Luc nay ddng co thQ nghiem b i t dau phat ra t i l n g gd.
a
KHOA HOC - CONG NGHEHinh 5. Do rung ddng cua dgng co d toe dg 3000vg/ph, 100% tai, vdi ty le LPG khdc nhau
6 ty le LPG 30%, bien do rung dong Ifin nhat cua ddng cO A KAcc cung g i l m mot it so vfii trQfing hgp thay the 2 0 % diesel va cao hdn so vfii trudng hpp sQ dung dPn nhien lieu diesel la 125%, Tuy nhien trong trQdng hop nay lai x u l t hien cd n h i l u bien dp rung dfing cd t i n sd Ifin hPn so vdi trQdng hop ty le LPG 20%, Tieng gd do kich nd x l y ra manh.
Vfii ty le LPG b i n g 4 0 % bien dp rung ddng ldn nhat cua dpng cP A KAcc cao hPn 183,3%, Dpng cP x l y ra tieng go manh Net, Day cung la ly do ma khdng t h i thpc hien viec tang luong LPG tiep Iheo cho ddnp co.
4. Ket luan va p h u o n g hUdng phat t r i e n He thdng d i l u k h i l n cung cap LPG dUdc t h i l t ke cfi k h l nang dam bao cho dfing cd hogt dfing dn dinh fi tat d cac che dp lam viec Vfii ket qua thQ nghiem tren dUfing dac tinh ngoai cho thay cfi the Qng dung LPG tren dfing cd diesel vfii ty le 30%, fi tde dd thap cfi the thay the tfii 40%, tuy nhien khi t_y le LPG cang tang len thi hien tUPng kich nd cang de xay ra. Vfii ty Id thay the LPG len tfii 3 0 % deu cho lupng tieu thy nhien lieu diesel+LPG nho hPn khi sQ dyng dPn nhien lieu diesel. Ddng thfii dfi rung dfing ciia dfing eP cting tang len khi tang ty le LPG do tdc dp tang ap suat Ifin va hien tUOng kich no
f r o n g nghien cUu nay, bd ELC dUpc d i l u k h i l n thil cdng thdng qua giao dien k i t noi vfii may tinh
trong khi dfing cd IhQ nghiem la ddng cd trang bj he thdng nhien lieu diesel dieu khien dien tQ. Vi vSy, trong tUOng lai can cfi d l tai nghien cQu bg d i l u khien cung cap LPG ( ELC) tu dgng giao t i l p vdi ECU ddng CO theo tUng c h l do lam viec U
Tai lieu t h a m k h i o
[1]. Phain Miitti Tuan (2008), Khi thai dAng cd va fi nhifim mOI tpiTJlng, NXB Khaa hoc va kji thual
[Z]. Tiing cnng ly xang diu Ulfit Nam, LPG - D|c linh LPG, Ha Nfii, 1997.
[ 3 ] , Blackmer Dover Gsmpaiy, liqullled gas handbooli, Buleiiln SOO- 01,2008.
[ 4 ] . Hakan Bayraklar, Drban Durgun. Investlgaiing the ellecis nl LPG nn spark ignition engine cnmbuslinn anit pepfopmance. Enepgy Conversion and Management 4G (ZDD5) Z3I7-Z333.
[ 5 ] . Thdi hao Kinh le Sai Gnn, Cdu Lnng se cd 1.500 taxi chay hing khi LPG, 29/10/2010.
[G]. Nguygn Qiang V i n t Nghien cAu sD fling kbi hda l d m chs xe hiyi vi muc dich hao ve mdi Ipdiino. Cfing ty cd khi Ngd Gta Td, 2008.
[ 7 ] . TS. Pham Huu Tuyen, PGS.TS Le Anh Tnin, KS. Nguydn Tk^ Tpifc, KS. Vu Khdc Thleo (ZD11), Nghien cdu sd dung lUBng nhien lieu LPG/dlesBl tpen ddng cd diesel, Tap chi Giao iltdng van i^t sd 1+2/20it, ISSN 08BB- 7012. •
[8]. Thomas Renald G.J, Sdmasundapam P. Eipepimeital InvestliBllii nn Allenoallnn ot Eialssinn wilh Optimized LPG Jel Inductinn m a Dual Fuel Diesel Engine aod Prediction hy ANN Mndel. Energy Pracedla 14 (2012) 1 4 2 7 - 1 4 3 8
[9]. AUL GmliH, Single cyllndep peseapch engine 5402, AustPia (2091).
[101. PGS. TS. fid Van DOng (2902), Tpang hi dlfin & diin l i Ipdi fi tfi hien dai, NXB Oai hoc Qudc gia TP.HD Gfii Mmh.
[ l i ] . le Phifdng Lan, Hoang BLTC Hal (ZOOO), Giao irinh ly thoydt i hal lip Borland DELPHI, NXB Giao due
[12], Ngd Didn Tdp (2003), Ky thudi vi didu hhlen vdi AVR, NXB Khoa h u c v a h y thuSt
[13]. Nguydn Tifdng Vi, PGS.TS. Le Anh Juin, PGS.TS. Hnang Bilk Long, Nguygn Ttie True, Uu Khic Thien (Sddac hlfit Ibaig 10/2011), Nghiln ctfu i n tinh cda dpog cd dleset miit xilanh khl sfl dung lifDng ntilfin Hlu LPG/diesel, Tap chi Cd k h t .
P H M G PHAP PHAN TiCH...
(Tiip theo trang 29) Bieu 2. Bang phan tich chi phi thue ngodi mdy thi cdng
Tliane
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i j > T r ( \ ) 1,100 1.000 I.SO 'loo 1 5 0 5 0 0 5 , S 0 0
Tfl lit! CP T N A T I Vlii
3 0 0 I O • ' ^ 0 2" ISl.OOO .^3 I B 4 5 0 3<i 7 0 0 8 7 0 3 7 S K , 120
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. i 3 , O I I . 3 B O O O 3O.45O.0CO.O0O 4 * _ 5 M H I 5 7 , 5 0 0 3 4 . i n . 7 3 J O 0 O 26,47!>.1>I4.000 7 . 0 3 5 , 0 0 0 , 0 0 0 1 6 4 ^ ^ 1 . 3 ^ 1 5 0 0
1 . 3 1 0 0 0 0 LOGO. 0 0 0 L 8 2 2 , 5 0 0 8 1 0 0 0 0 9 0 2 5 0 0 2 5 0 BOO 5,y'J.5.(K)0
Ap d y n g phUPng phap hdi quy tuyen tinh d l xac djnh chl phi may thi cdng theo sd ngay cdng lao dpng true t i l p : Y = a +b.X
Vfii Y la tdng chi phi may thi cdng, X sd ngay cdng lao ddng trUc t i l p ,
A p d u n g phuong phap tong binh phUPng sai so nho nhat, tim tham sd a ya IJ thfing qua thiet lap va giai he phuong trinh chuan t&c,
6a + 5.800 b ^ 161,494.690 5.800a + 5.995,000 b - 164.041,329,500 Giai he phUPng trinh tren vfii k i t qua:
a = 7,176 376 (dong) : b = 20 420,08 (ddng/ngay)
PhUdng trinh dy doan chi phi thue ngoai may thi cdng d Cdng ty se la:
Y = 7.176.376 + 20,420,08.X
Gia sQ, quy mfi san xuat ciia doanh nghiep dugc dac trung bfii chf tieu sd ngay cdng lao ddng trUc t i l p frong ky (thang 7) la 1.000 ngay cfing, Nhu vay, ap dyng mfi hinh hoi quy tren, tong chi phi may thi cfing se la:
Y = 7.176,376 + 20.420,08x 1,000 = 27.590.450 3. Ket luan
Phuong phap tdng binh phUPng sai sd nhfi nhal dupc cac nha quan tri DN sd dung nhU mdt cdng cy rat phd b i l n trong viee phan tich chi phi hdn hpp vi tinh Qu Viet ciia nfi dfi la mang lai k i t qua tUOng doi chinh xac, qua dfi se phyc vy cho nha quan trj doanh nghiep xac djnh dung dSn phUPng hUfing d l nang cao hieu qua ciia chi phi. Tuy nhien, phupng phap nay cung tdn tai kho khan nhu: Viec thu thap, xQ ly sd lieu cho viec tinh toan va danh gia mat thdi gian va cdng sUe, Viec phan tich chi phi hdn hdp thanh ydu td b i l n p h i v a dinh phi can sQ dung phUdng phap n^y d e j h u c hien, nd dam bao tinh chinh xac va tinh tdng the cao 3
Tai lieu t h a m k h ^ o
[ 1 ] . PGS. T S V d Van Nhj (2009), Ki toin DN xay lap - Ke toin dan vi chu dau tff, NXB Tai chinh
[2], PGS.TS Doan Xuan Tien (2005), Giao trinh ke toin quan tri DN, NXB Tai chinh
[3] Bang tdng hop chi phi nam 2011 • Cdng ty CP dau t u va xay dQng PML Viet Nam
