UfNG DUNG CFD TRONG KHI DONG LI/C HOC DE XAC Om LI/C CAN KHONG KHI VA LI/C NANG CUA XE DU LKH TAI TRONG NHE APPLICATIONS OF CFD IN AERODYNAMICTO DETERMINE AIR DRAG AND LIFT OF LIGHT CAR
Trang 1UfNG DUNG CFD TRONG KHI DONG LI/C HOC DE XAC Om
LI/C CAN KHONG KHI VA LI/C NANG CUA XE DU LKH TAI TRONG NHE
APPLICATIONS OF CFD IN AERODYNAMICTO DETERMINE AIR DRAG AND LIFT OF LIGHT CARS
Le Hong Quan, Nguyen Anh Ngoc
Tdm t i t
Bai bao Sli'dung cac cdsdiy thuyet cda khi'dong life hoc nham du'a ra nhung de xuat tot nhat ve hinh dang
khidgng hoc ci^a xe tac dgng tdi h§ sd luc c^n va luc nang than xe nhcf vao iing dung may tinh trang dong
lire hoc chat ldng thong qua phan mem Ansys Fluent 14.0 flieu nay vo ciing hQu ich tmng cac nghien ciiti
v^ sau nay v6i muc dich la gi^m thieu luc can chuyen dgng cung nhif luc nang trong mot so dieu kien ve
dudng x^ hay ngifcii 1^1 Ba mo hinh tiian xe don gian vdi tam chan trudc, sau va khong cd tam chan duoc
thiet kl'v^ duoc dat ben trong ong khi dong phu hcTp de phan tich nhifng anh hucmg cua lu'c can khong kht
t^c dong tdi xe tSI trong nhe tmng cac trudng hop chuyen dpng khac nhau
Cie ke't qui du'Oc dinh gia mot each ky luflng nham de ra nhifng hudng nghien cilu xa han lien quan tdi cac
van de cap thiet hi§n nay nhif ti^t kiem nang luong, can bang than xe, dieu khien trtrgt banh, an toan
Tirkh6a: Khi dong lu'c hocxe hoi, ANSVSICEM CFD, xe tai trong nhe, he so can khong khiva luc nang
Abstract
This paper utilizes aerodynamic theory to indicate the best shape of car's body in drag force and lift force
coefficients relying on simulation of computational fluid dynamics (CFD) by Ansys Fluent 14.0 That is very
meaningful in the future studies which purposes are deceasing in drag force and increasing in lift force in
vary conditions of ether ground environment or driver Three simple models with front paneL rear panel
and v^ithout panel were created and put inside the appmpriated air tunnel to analyze the affects of air
force into light car's body in moving conditions
Results are evaluated carefully to expose new further research trends that relate on the saving energy,
vehicle stability, friction contml, car safety and etc
Keywords: Vehicleaerodynamic, ANSYS ICEM CFD, light car, drag and lift coefficient
TS Li Hong QuSn, ThS IfguySn Anh Ngoc
Khoa CAng ngh^ 0 to, Tnidng fiai hoc Cong nghiep Ha Noi
Emaltquan vsae@haiii edu.vn
1 Gidl THI$U CHUNG
Trong vai chuc nam gan day khi
nginh cong nghiep 6 to phat tnen
manh me, khi dpng life hpc than xe da
duoc nghien cCtu va phat trien nhSm
muc dich nang cao tmh chat dong lac
hpc cua cac loai xe chay tren mat dat
Ngay nhan bai: 14/6/2014 Ngaydiap nhan dang: 20/8/2014
Tinh chat dong luc hoc phu thupc rat nhieu vao hinh dang cua than xe, nhan
to chiu anh hudng chinh cua dong khong khi bao quanh gay ra luc can chuyen dong cung nhu lu'c nang va mo men quay xe quanh true t h i n g difng
Do la nhQng I Uc rat quan trong tac dpng
CACOjNH NGHIA VA CHU THICH
CFD Computational Fluid Dynamics ECUoA Elearonic Control Unit of Aerodynamics ICEM Integrated Computer-aided Engmeenng and Manufacturing R&D Research and Develop
A , A Dien tich can chinh dien [m^]
Cj Hesoc^nkhongkhi
Cj Hesdiucnang Fj^^_^^ Luc keo cua xe f^ LUc nang khi ddng Fjj Luc can khf dong
f Hesd can lan
g Gia toe trang trudng
m Khdi luong xe U,^ Vantocti/Ongddi U,V Van tdc khdng khi
0 Gdc doc mat dudng
p Mat dd khdng khi
[-1 [-1
m
INI
l-l
[m/s'l [Kg] [m/s] [m/s] [radl [kg/m'
i e n k h u n g v o x e k h i c h u y e n d o n g , d a c
b i e t d o i v d l nhCtng x e c o t a i t r p n g n h e , chiing tac dong trUc tiep den he thong phanh, lai, treo va he thong truyen luc cua xe Do do, vdi nhQng hinh dang khi dong hoc khac nhau cua vo xe se dem lai nhQng ket qua khac nhau, dieu dd
vd cung hQu ich cho cac nha nghien cQu va phat tnen (R&D) khdng nhQng trong nghien cQu ma trong ca s i n xuat nhSm dat dJoc nhdng thanh tifu dot pha trong Unh vQc xe hoi
Trang 2Ngay nay, yeu cau cua khach hang
ngay cang cao ddi hdi cac nha san xuat
xe hcJi va cac nha nghien cdu phai no
luc rat nhieu de thda man nhdng yeu
cau cua khach hang nhU: an toan hon,
tien nghi hon, de dang dieu khien, tieu
hao nhien lieu it Ben canh do, gia
cua cac loai nhien lieu hda thach tang
nhanh do khan hiem va khdng the tai
che yeu cau phai tiet kiem nang laong
hoac tim kiem ngudn nhien lieu thay
the phu hop vdi cac loai ddng ccj hien
nay Van de giam daocluc can khi ddng
hpc nhSm ha thap mQc tieu hao nhien
lieu hay giam lac nang khi dpng lac hpc
nham nang cao tai trong bam cua banh
xe vdi mat dadng giup cho xe chuyen
ddng an toan la nhQng y tudng tdt
Thdng thudng, md hinh xe taong
duong se dapc thiet ke va dat vao ben
trong mdi tradng gia lap (mdt ong
khi ao vdl khdng khi chuyen dong
ben trong) va daoc mo phdng bang
may tinh Cac ket qua se daoc phan
tich trade khi thiet lap mdt he thdng
thQ nghiem thUc te trong phong thf
nghiem vdi cac cam bien va cac trang
thiet bl de do dac cac thdng sd can
thiet Cudi cung, de an tot nhat vdi cac
ket qua kha thi nhat se daoc laa chpn
de tiep tuc nghien cdu va phat tnen
1.1 He so can khong khi va he so
luc nang
Lac keo cua xe giup xe chuyen
ddng tren dadng phy thuoc vao lac
can khdng khi, \iic can quan tfnh, luc
can lan va lac can ddc theo cdng thdc
sau[l]:
F - - n U C A + m — +
dnver 2 ^ ' D P ^ t
+ mgfcos a+mgsina
Oe gtam mQc tieu hao nhien lieu,
mdt trong cac yeu td d ve phai cua
phaong trinh tren phai dat cac tieu
nhang ba trong sd chung lai chda khdi
laong m cua xe, yeu td cdn lai chQa kich
thadc, hinh dang va van tdc cho nen
chung ta cd the tac ddng vao dd mdt
each de dang de lam giam C^
Hinhl Canhkhiddng Vao nhQng nam 1920, he so can khdng khitrung binh cua xe du hch vao khoang 0,7 Ngay nay, he so nay dQOc giam xudng thap hon 0,3 [2] He sd iQc nang C|^ cd the dapc tfnh toan theo cdng thQc sau [3]:
• Scaled residuals: 10"^
-1726831 phan tif va 307788 nut
• Actual car and CAD design (for CFD analysis) size ratio:1:1
2 THIET KE M 6 HJNH WlO PH6NG
Md hinh xe dOn gian dQOc tao ta sau khi cac dadng bao 2D cCia than xe
daoc hoan thanh nhd vao geometry
subsystem trong Fluid Flow system v6i
chieu cao 1,42 m va chieu dai 5,10 m
(hinh 2)
C
- p V ' A Vdi nhQng xe chd khach hang nhe, C|^ thQdng nam trong khoang t d 0,106 den 0,143 [4] NhQng trong mpt so loai
xe dac biet nhuxe dua, he so nay cd the
ha xudng t d - l ,602 tdi -0,048 [3]
Oe do dupc chinh xac he sd can khdng khf va he sd lUc nang cua xe t<hi chay tren dQdng la khdng dOn gian, tieu tdn khdng it thdi gian va tien bac
1.2.Dieu kien bien
Nhd vao phan mem ANSYS ICEM CFD Fluid Flow/ (FLUENT), md hinh
xe tai trpng nhe duac thiet ke de md phdng nham myc dich tim kiem nhQng thanh qua mong muon theo cac dieu kien ban dau nhQ sau:
• Mo hinh md phdng- k-epsilon (standard wall function model)
•Van toe khi hut vao: 30 m/s
• Inlet: Velocity inlet
• Outlet: Pressure outlet
• Top, side and ground walls:
Stationary walls
• Car wheels: No rotational walls
• Car Body: Stationary wall
• Symmetry line: Symmetry plane
•Gauge pressure: 0 Pa
•Mat dp khdng khi' 1.225 Kg/m^
• Dynamic viscosity: 1.7894 x 10"^
kg/m^s
• Reynolds number: 2.62 x 10*
•Nhiet do 288.16 K
Hinh 2 Thiet ke md hinh 2D than xe
Sau do, md hinh 3D diroc tao
ra bang lenh extrude va diroc dat trong ong khi dpng cd kich thu'dc LxWxH-12lx6hx4h [5] nha trong hinh
3 Name selection cua cac mat cila ong khi ddng daoc chpn de thiet lap
cac dieu kien bien: velocity inlet il mat trade, pressure outlet d mat sau, cdn lai
la top and side walls, and grounci.TatcS cac dieu kien deu dQOc nhac tdi 6 phan tren va cd the thay ddi phu thuoc vao cac gia thiet cua cac thiet bi thi nghiem
Hinh 3 Thiet ke va chia lUdi vdi ANSYS ICEMCB Ladi phan t d daoc tao ra vcii
1726831 phan t d va 307788 niit Si phan tQ va nut dd khdng ph3i la tot
Trang 3nhat nhQng phu hpp vdi tdc do xQ ly
dd lieu cua may tinh
Hinh 4 Tam panel trifdc va sau trong 2D CAD
design
Vdi ba md hinh khac biet, khdng
CO panel; panel trQdc va panel sau, da
dapc hoan thien qua nhang bade phan
tich de danh gia tac ddng cua hinh
dang khung vd tdi sa anh hudng cua
khi ddng luc hoc len than xe khi nd di
chuyen vdi tdc dp 30 m/s Qua trinh md
phdng dQOc cai dat vdi 1500 phep tfnh,
mat thdi gian t d 3 den 32 gid de tinh
toan phu thudc vao tQng trQdng hop
3 CAC KET QUA VA PHAN TICH
Sau khi chay Ansys, tinh nang CFD post daoc tien hanh de du doan van tdc ddng khdng khi bao quanh than xe
va ap suat khdng khi trong tdng tradng hop md phdng IVlat phang tam doi xQng daoc laa chpn de thiet lap tradng
ap suat va van tdc ddng khdng khi Cac ket qua daoc xuat ra trong cac hinh 5;
6; 7 de d^ dang danh gia sQanh hQdng cua khi dpng iQc hoc len vd xe vdi cac tam can d vi tri khac nhau
Quan sat bieu do velocity streamlines, ddng chay cua khdng khi qua bien dang cua vd xe se thay ddi hudng chuyen ddng khi thay ddi bien dang vd xe Md hinh xe khdng cd tam panel chan secan khdng khi ft hOn nen ddng khi kha dn dinh nhu hinh 5 Cdn
xe vdi tam panel phia trade va phia sau se thay doi ddng khi chuyen ddng kha nhieu nen ddng khf se khdng on dinh Ddng khi xoay xung quanh than
xe dupc tao ra phia sau cac tam panel
la nhan td chinh gay ra can chuyen dpng cua xe va nd se cang Idn khi tdc
I
Hmh /.Velocity streamliner cua md hinh vdi Iam panel sau
a ground pressure
i
v , ) (i i'=
i _
Hmh S Velocity Streamlines Hmh 6 Pressure contours
Hmh 8 Cat vong tinh cua he so can va he sd lu'c nangiCjVaC)
Trang 4dp chuyen ddng taong doi giQa khdng
khi va xe tang cao Vdi van toe chuyen
dong tuong ddi giQa khdng khf va xe
gia dinh [a 30 m/s, van tdc ddng khf
xung quanh vd xe nam trong khoang
tQO tdi 44,55 m/s,
Od thi phan bo ap suat, pressure
contours trong hinh 6, chi ra dQpc ap
suat phan bo xung quanh vd xe theo
mau sac Chfnh su chenh lech ap suat
d cac diem khac nhau xung quanh
than xe gay nen lac can chuyen dpng
(Drag force F,^) va lUc nang (Lift force F|^)
tac dung len xe khi chay tren dudng
Chung chi phu thudc vao hinh dang
khi ddng, toe do xe va tdc dp gid ben
ngoai moi trUdng
Ap suat khdng khidnhdng vung cd
tdc dp cham iudn ludn cao va ngupc lai
d nhQng vung cdtdc do eao thi ap sua't
xudng thap va nd nam trong khoang
-1,249e03 tdi 5,620e02 Pa Oieu dd giai
thieh cho sQ khac biet ve iQc can va iQc
nang trong cae trQdng hop khac nhau
ve hinh dang hay toe do ehuyen dpng
cua khong khi,
Trong hinh 7, hinh anh phan tich
eua md hinh thQ 3 vdi tam panel dat d
phia sau daoc tao ra De dang nhan ra
dac tinh khi ddng cua nd la rat tdt vdi
he sd lUc nang cd gia tri am C^- -0,3385
nhang he sd lUe can chinh dien lai hoi
cao Cp=0,6997
Neu he sd nay cd the giam xuong
duoc tdi 0,35 thi md hinh nay la hoan
hao, ed the dUa vao Qng dung de san
xuat trong thQc tien
Hinh 8 la do thi cua he so C,^ va C
trong ba tradng hop 6uac md phdng
vdi dieu kien dau la 1500 phep tinh
toan Trong tradng hop thQ nhat, mat
hon 1000 phep tinh thi dat dong nhat
Cdn trong trQdng hop tam panel dat
phia trade thi mat tren 350 va tren 500
trong trUdng hop thd ba
So sanh cac he so can khong khi
va he so liTc nang trong ba tru'dng
hcrp
Cudi cung, cac ket qua tdt nhat cua
he so can khdng khf va he sd lUc nang trong mdi trUdng hop daoc so sanh trong bang 1
Bangl Sosanhcachesd
Panel Khong Trifdc Sau
V(iTi/s) 30 30 30
CB 0,3282 0,5352 0,699/
C, 0,4378 0,2852 -0,3385
Theo bang 1:
-I- He sd can khdng khi tang dan t d tradng hpp 1 tdi tradng hop 3 -I- Hesd luc nang giam dan tQ trudng
hop 1 tdi trQdng hop 3
+ C|^ trong trQdng hop thd 3 cd gia tri am, nghTa la iUc nang khi do lai bien thanh lUc tac dung nhan than xe xudng mat dudng giong nhutrpng lUccua xe vay
4 KET LUAN
Cac ket qua thu dUpc t d Qng dung CFD da md ra rat nhieu y tQdng mdi, kha thi, hQu hieu trong viec thiet ke khf ddng hoc vd xe lam tang them cac tinh nang hQu ich cua xe hoi, dap Qng dQpc nhu cau ngay cang eao cua ngadi sd dung:
Khai thac ti'nh nang khi dong hoc
de nang cao he so bam cua lop xe vdi
mat dadng cho xe du Ijch tai trong nhe khi chay vdi toe do cao
Mdt vai bai bao da de cap den van
de Qng dung khf dpng lUc hpc vao xe hoi nhung mdi ehl tap trung vao van
de giam thieu iuccan khdng khi de tiet kiem nhien lieu Tuy nhien, khi chay tren dudng cao tdc toe dd xe rat ldn nen van de an toan dupc Uu tien hang
dau Khi do, rat de b; mat dieu khien
hadng hay luc phanh thap do luc bam nhd, dac biet ddi vdi nhQng loai xe tai trpng nhe Hau qua se la rat ldn mdt khi tai nan xayra,
Thdng thadng, neu muon giam iQc
nang thi lac can se tang theo Dieu nay
la cd loi trong trUdng hop xe dang chay nhanh can phanh khan cap Mat kha^
nd dem lai sU dieu khien hudng chfnh xac vi luc bam cao giup nang cao tinh nang an toan khi dieu khien xe Tuy nhien, lUc can chinh dien tang caose lam giam tfnh nang chuyen dong ci3a
xe cung nhu mQc tieu hao nhien lieu tang
Giai phap dUa ra la khai thac dac tinh khi dpng lUc hoc than xe bSng each lap vao than xe cac tam panel giong nhu canh may bay de lam tang tai trpng bam cua xe khi can thiet NhQng tam panel nay cdn cd the dieu khien daoc gdc quay cung nhu chieu cao bdi he thdng dieu khien ECUoA khi phanh hoac khi danh lai Bang ccf che nha trinh bay dtren, ngUdi lai cdthe dieu khien giam toe do
xe nhanh hon cung nhuthay doi hUdng chuyen ddng eua xe d§ dang hOn ngay
ca khi chay vdi tdc dd cao
Nang cao tinh nang on dinh cii
xe bang each khai thac siJrc gio
Khi xe ehuyen ddng tren dUdng, than xesebj mat on dmh trong mdt vai trUdng hop do dieu kien chuyen dpng gay ra Dieu do gay nen nhdng vin ^ khdng tot cho xe nhU dao ddng manh, rung lac than xe, mat dieu khien hadng, giam hieu qua phanh
De ban che nhQng hien taong do, chung ta cd the thiet ke cac ranh khc^ khi nhd doc hai ben vd xe de dieu khien ddng chay khdng khi hai ben trai va phai cua than xe Nhd vao cac ong khong khi dd, mdt lUc dang ke ttie ddng tQ hai ben thanh xe se giOptang tinh nang can bang than xe khi ehuyfti ddng CJ hai dau cua cac dng khi d6, thiet ke eae canh cQa cd the dong hoac
md theo cac tin hieu dieu khien tif hi thdng ECUoA SU ddng md ldn hoac nhd; nhanh hoac cham se dUOC ph&i tich va tinh toan t d cac tin hieii nhan
ve t d cae cam bien va thiet bi do.Them nQa, ed the ket hop cung vdi cac cinh
Trang 5nhu tradng hop dau de tang tinh nang
on djnh
So sanh vdi cac he thong trudc kia
• nha he thong phanh can bSng "ESP hay
' VSC", phuong phap nay cd nhieu uu
diem bdi vi nd cd the dieu khien mpt
' each rat linh hoatva chinh xac, Cac cam
• bien duoc sd dung d day la cam bien
1 iSc doc va 15c ngang than xe, cam bien
gio, cam bien gdc quay tam panel va
"' gdc mdcac ctfa thdng gid
Thu nang lu'ang gio de trtf lu'c cho
'' he thong lai
Mdt y tudng nda la sQ dung nang
; iQpng gid detang eudng cho he thdng
'i lai Trong trUdng hop nay, can thiet ke
i hai he thdng canh Idn d hai ben cQa
t than xe nh^m muc dich loi dung luc
can khdng khi d hai ben trai va phai de chuyen hudng chuyen dpng ket hpp cung vdi lac ben dadi mat dUdng tac ddng len banh xe dan hudng Hoac
cd the dung chi mdt he thdng eanh d giQa xe nhUng ed the thay doi dapc gdc quay trai va phai de giup xe doi hudng dedang hon
Cac cam bien daoc diJng trong trudng hop nay la cam bien gid, cam bien toe dp xe, cam bien gdc quay vd Iang
Phan bien khoa hoc: TS Le Van Anh
TAI UEU THAM KHAO
[1], L L L J a I W Chnstoffer Landstrom,
"Aerodynamic Effects of Different Tire Models on a
Sedan Type Passenger Car," SAE Intemetional, vol 5, no.l (may2012),pp 136-151,2012
[2] I B Ilhan Bayraktar, "Guidelines for CFD Simulations of Ground Vehide Aerodynamics," SAE Paper 2006-01-3544,2006
[3] 0 Ehirim, "Optimal Diffuser Design for Formula SAE Race Car Using an Innovative Geometry Buildup and CFD SimulatJon Setup with OnTrack Testing Correlation," SAE Teachnical paper 2012-01-1169,2012
[4! T K E M a J W Oliver Fischer, "CFD Approach to Evaluate Wind-Tunnel and Model Setup Effects on Aerodynamic Drag and Lift for Detailed Vehicies/'SAETechnical Paper 2010-01-0760,2010 [5] S.K.a K N.AshishSingh,"HighPerformance CFD Computations for Ground Vehicle Aerodynamics," SAE InternetionalSlAT India, 2011
TdNG K^T CdNG T A C KHUYDN HOC N A M HOC 2 0 1 3 - 2 0 1 4
V A T R A O H O C BdNG N G U Y I N THANH BlNH N A M HOC 2012 - 2013
Thifchienk^ho?ch dio tao nam hoc 2013-2014, chieu ngay 18/6/2014tri/cfng
f)^l hpc Cdng nghiep Ma Noi to chii'c bu6i tong ket cdng tac khuyen hoc nam hoc
2013-2014va trao hoc bfing Nguyen Thanh Binh nam hoc 2012-2013
Tdi di( bu6i Ih tSng kft e6 TS, Trln Mc Qu;? - Hieu trudng NhS trudng, TS Ha
Xuan (Juang - Phd Hieu trudng, TrUdng Ban van dong quy khuyen hoc, cac dong
chi lanh dao cac phdng, khoa, don vj trong trudng; dai dten gla dinh ddng chi
Nguyiln Thanh Binh, dcii di^n c^c c(f quan, dan vi, doanh nghiip tai tro va cac em
sinh vi^n ti€u bleu nhan hoc bong
sinh Nha trudng, ngudi da cd nhieu ddng gdp cho sU nghiep xay difng, phat trien Nha trifdng va khcA xUdng thanh lap quy
Thay mat cho Ban van ddng quy khuyen hoc, TS Ha Xuan Quang da tdng ket cac hoat ddng khuyen hoc trong nam hoc qua Nam hoc 2012 - 2013, hoc bdng nhutig tam guong tieu bieu trong phong trao hoc tap, nghien cijti khoa hoc va nghi life vUOn len trong cudc sdng
Dai dien Ban Lanh dao Nha tru'dng, TS Tran Ddc Quy - Hieu irudng Nha trUdng ghi nhan va cam on gia dinh bac Nguyen Thanh Binh, cac td ehdc va ca nhan da
ddng gop xay dUng quy Day thuc su la nguon khich le cho cac hoc sinh, sinh
vien, cac can bd vien ehdc Nha trirdng dang tham gia cong tac van dpng xay dung va phat tnen quy
Trong nhu'ng nam ttep theo Ban van ddng quy se tiep tuc van dong cac dOn vi, doanh nghiep, ca nhan tiep tuc ddng gop, ung hd de xay dung quy khuyen hpc ngay cang Idn manh Qua do, se cd nhieu suat hpc bong dUoc trao cho cac em sinh vien hon nu'a
Quy khuyen hoc Nguyen Thanh Binh truong Dai hoc Cdng nghiep Ha Noi thanh
l<lp nam 2003, Quy khuyen hoc vmh duduttc mang ten nguyen Oy vien Bg Chinh
tri,Thudng true Ban BithuTrung i/angDSng, BithuThanh uy Ha Ndi, cUU hoc