Vehicle Propulsion Systems Lecture 2. Energy System Overview. W2M Energy Paths. Evaluating the integral. Mechanical Energy Demand of a Cycle

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1 Vehcle Propulson Systems Lecture 2 Fuel Consumpton Estmaton & ICE Powertrans Lars Erksson Professor Vehcular Systems Lnköpng Unversty March 21, / 51 3 / 51 W2M Energy Paths Energy System Overvew Prmary sources Dfferent optons for onboard energy storage Powertran energy converson durng drvng Cut at the wheel! Drvng msson has a mnmum energy requrement. 4 / 51 5 / 51 Mechancal Energy Demand of a Cycle Only the demand from the cycle The mean tractve force durng a cycle F trac = 1 xtot where = t max 0 v(t)dt. Note t trac n defnton. Only tracton. 0 Idlng not a demand from the cycle. max(f (x), 0) dx = 1 F (t)v(t)dt t trac Evaluatng the ntegral Tractve force from The Vehcle Moton Equaton F trac = 1 2 ρ a A f c d v 2 (t) + m v g c r + m v a(t) Resultng n these sums F trac = F trac,a + F trac,r + F trac,m F trac,a = ρ a A f c d h F trac,r = 1 m v g c r v h F trac,m = 1 m v ā v h 6 / 51 7 / 51 Values for cycles Numercal values for the cycles: X trac,a = 1 X trac,r = 1 X trac,m = 1 {MVEG-95, ECE, EUDC} h = {319, 82.9, 455} v h = {0.856, 0.81, 0.88} ā v h = {0.101, 0.126, 0.086} Ē MVEG-95 A f c d m v c r m v 10 Tasks n Hand-n assgnment kj/100km 8 / 51 9 / 51

2 Energy demand agan Recuperaton Perfect recuperaton Prevously: Consdered energy demand from the cycle. Now: The cycle can gve energy to the vehcle. Mean requred force Sum over all ponts F = F a + F r F a = ρ a A f c d N =1 h Recover the vehcle s knetc energy durng drvng. F r = 1 m v g c r N v h =1 10 / / 51 Perfect recuperaton Numercal values for cycles Numercal values for MVEG-95, ECE, EUDC X a = 1 v 3 h = {363, 100, 515} X r = 1 v h = {1, 1, 1} Ē MVEG-95 A f c d m v c r kj/100km Comparson of numercal values for cycles Wthout recuperaton. X trac,a = 1 X trac,r = 1 X trac,m = 1 h = {319, 82.9, 455} v h = {0.856, 0.81, 0.88} ā v h = {0.101, 0.126, 0.086} Wth perfect recuperaton X a = 1 v 3 h = {363, 100, 515} X r = 1 v h = {1, 1, 1} 12 / / 51 Perfect and no recuperaton Cycle energy reqrement (no recuperaton) Ē MVEG-95 A f c d m v c r m v 10 kj/100km Senstvty analyss Mean force represented as lter Desel / 100 km. S p = lm δp 0 S p = lm δp 0 Vehcle parameters: Af c d c r m v [ĒMVEG-95 (p + δp) Ē MVEG-95 (p) ] /Ē MVEG-95 (p) δp/p [ĒMVEG-95 (p + δp) Ē MVEG-95 (p) ] δp p Ē MVEG-95 (p) 14 / / 51 Vehcle mass and fuel consumpton Vehcle mass s the most mportant parameter. 16 / / 51

3 Realstc Recuperaton Devces Vehcle Mass and Cycle-Avearged Effcency 18 / / 51 Two Approaches for Powertran Smulaton Dynamc smulaton (forward smulaton) Cycle Drver Engne Transm. Wheel Normal system modelng drecton Requres drver model Quasstatc smulaton (nverse smulaton) Cycle Vehcle Wheel Reverse system modelng drecton Follows drvng cycle exactly Model causalty Transm. Engne Vehcle 20 / / 51 Dynamc approach Quasstatc approach Drvers nput u propagates to the vehcle and the cycle Drvers nput... Drvng force Losses Vehcle velocty Feedback to drver model Avalable tools (= Standard smulaton) can deal wth arbtrary powertran complexty. Backward smulaton Drvng cycle Losses Drvng force Wheel torque Engne (powertran) torque... Fuel consumton. Avalable tools are lmted wth respect to the powertran components that they can handle. Consderng new tools such as Modelca opens up new possbltes. See also: Effcent Drve Cycle Smulaton, Anders Fröberg and Lars Nelsen (2008) / / 51 Causalty and Basc Equatons Hgh level modelng Inputs and outputs Causaltes for Engne Models Pc Quasstatc Approach ICE Engne effcency η e = ω e T e P c Enthalpy flow of fuel (Power H fuel = P c ) ωe Te P c = ṁ f q LHV Pc Dynamc Approach ICE ωe Te 24 / / 51

4 Maps Measured engne effcency map Used very often Engne Geometry Defntons TDC BDC l a theta B L Vc Cylnder, Pston, Connectng rod, Crank shaft Bore, B Stroke, S = 2 a Number of cylnders z Cylnder swept volume, V d = π B2 S 4 Engne swept volume, V d = z π B2 S 4 Compresson rato r c = Vmax Vd +Vc V mn = V c What to do when map-data sn t avalable? 26 / / 51 Defnton of MEP Mean Pston Speed (S p = mps = c m ): See whteboard. c m = ω e S π Mean Effectve Pressure (MEP=p me (N = n r 2)): p me = N π T e V d Used to: Compare performance for engnes of dfferent sze Desgn rules for engne szng. At max engne power: c m 17 m/s, p me 1e6 Pa (no turbo) engne sze Connecton: P e = z π 16 B2 p me c m 28 / / 51 Torque modelng through Wllans Lne Map Representaton Measurement data: x: p mf y: p me = BMEP 15 Torque and fuel connecton (λ=1) Engne BMEP [bar] Fuel MEP [bar] Lnear (affne) relatonshp Wllans lne Engne effcency: p me = e(ω e ) p mf p me,0 (ω e ) η e = pme p mf Wllans lne parameters: e(ω e ) p me,0 (ω e ) 30 / / 51 Causalty and Basc Equatons Causaltes for Gear-Box Models Quasstatc Approach ω1 T1 γ GB Power balance Loss free model ω2 T2 ω 1 = γω 2, T 1 = T 2 γ Dynamc Approach ω1 T1 γ GB ω2 T2 32 / / 51

5 Dfferent Types of Gearboxes Connectons of Importance for Gear Rato Selecton Vehcle moton equaton: Manual Gear Box Automatc Gear Box, wth torque converter Automatc Gear Box, wth automated clutch Automatc Gear Box, wth dual clutches (DCT) Contnuously varable transmsson m v d dt v(t) = F t 1 2 ρ a A f c d v 2 (t) m v g c r m v g sn(α) Constant speed d dt v(t) = 0: F t = 1 2 ρ a A f c d v 2 (t) + m v g c r + m v g sn(α) A gven speed v wll requre power F t v from the powertran. Ths translates to power at the engne T e ω e. Changng/selectng gears decouples ω e and v. Requred tractve force ncreases wth speed. For a fxed gear rato there s also an ncrease n requred engne torque. 34 / / 51 Gear rato selecton connected to the engne map. Optmzng gear rato for a certan cycle. Potental to save fuel. Case study 8.1 (we ll look at t later). Addtonally: Also geometrc rato between gears. g,1 g,2 g,2 g,3 g,3 g,4 g,4 g,5 36 / / 51 Gear-box Effcency Clutch and Torque Converter Effcency In tracton mode T 2 ω w = e gb T 1 ω e P 0,gb (ω e ), T 1 ω e > 0 In engne brakng mode (fuel cut) Frcton clutch torque: T 1,e (t) = T 1,gb (t) = T 1 (t) t Acton and reacton torque n the clutch, no mass. T 1 ω e = e gb T 2 ω w P 0,gb (ω e ),, T 1 ω e < 0 38 / / 51 Torque Characterstcs of a Frcton Clutch Man parameters n a Torque Converter Input torque at the converter: T 1,e (t) = ξ(φ(t)) ρ h d 5 p ω 2 e(t) Converter output torque T 1,gb (t) = ψ(φ(t)) T 1,e (t) Graph for the speed rato φ(t) = ωgb ω e, and the expermentally determned ψ(φ(t)) Approxmaton of the maxmum torque n a frcton clutch ) T 1,max = sgn( ω) (T b (T b T a ) e ω / ω0 The effcency n tracton mode becomes η tc = ω gb T 1,gb ω e T 1,e = ψ(φ) φ 40 / / 51

6 Method Average operatng pont method Good agreement for conventonal powertrans. Hand-n assgnment. 42 / / 51 Quasstatc analyss Layout Quasstatc analyss IC Engne Structure More detals and better agreement (depends on model qualty) Good agreement for general powertrans Hand-n assgnment. 44 / / 51 Quasstatc analyss Engne Operatng Ponts Dfferent tools for studyng energy consumpton n vehcle propulson systems Quas statc Dynamc QSS (ETH) X Advsor, AVL X (X) PSAT X CAPSm (VSm) X Inhouse tools (X) (X) 46 / / 51 PSAT Advsor Argonne natonal laboratory 48 / / 51

7 Advsor Informaton from AVL: The U.S. Department of Energy s Natonal Renewable Energy Laboratory (NREL) frst developed ADVISOR n Between 1998 and 2003 t was downloaded by more than 7,000 ndvduals, corporatons, and unverstes world-wde. In early 2003 NREL ntated the commercalsaton of ADVISOR through a publc solctaton. AVL responded and was awarded the exclusve rghts to lcense and dstrbute ADVISOR world-wde. 50 / 51