1、Chapter Two-Fuel Economy of Vehicle What is aim of fuel economy?To finish the unit transportation load with minimum fuel consumption. 2.1 Evaluation Index（评价指标）:1. Fuel consumption quantity per unit distance Q （ ） 单位行程燃油消耗量2. Fuel consumption quantity per unit distance and unit work load- （ ） 单位运输工作
2、燃油消耗量Note : In USA MPG（miles per gallon）1 mile1.8 km ; 1gallon=3.758l(liter) American cars 2030 MPG 8.310.4l/100km Japanese cars 2840 MPG 5.27.5l/100km (Prius:33km/l)2.2 Calculation of Fuel Consumption of Vehicle1. The Equation of Fuel Consumptionkml 100/tQkmtl100/ Clue: unit: Pe (kw);Ttq(Nm);ge(g/k
3、wh) GT(kg/h); (N/l);Q(l/100km);Note: Q is always concerned with ge ; : for gasoline = 7.2 (N/l) for diesel = 8.2 (N/l) )100/(02. 1)()100/(02. 1)100/(1081. 9)100/(10)/(1000)/()/();100/(:)/(1000)/(9549kmlgupgQfuelofdensitykmNupgkmNupgkmkgupgkmkgupgkmkguGhkmukmlQvehiclehkgpgGhkwggnTpaeeaeeaeeaeeaeeaTae
4、eTetqe2. Fuel Consumption Performance of Engine2.1 Fuel consumption performance-needed output power characteristics of engine （负荷特性）To describe how the performance of engine develops with the change of load of the vehicle that is the needed output power of engine Definition: output-power ratio(负荷率）负
5、荷率）= (needed output power of engine)/(maximum power available of the engine) = u2/u0Note: For Q ( ） Pe is the corresponding Y-coordinate value of (Pf +Pw)/T curve in the Graph of Power Equilibrium; ge could be available from the right graph with given n;Conclusion : （under given n) Pe increases with
6、 the decrease of ge under the given n (in most instance); output-power ratio always increases with the decrease of ge (in most instance); ge meets its minimum value when the output-power ratio come close to 80%; aupegeQ02. 1/2.2 Universal Characteristics of Engine （万有特性）3. Power Equilibrium When lev
7、el road & constant speedNote: Pe is the power needed by the vehicle to maintain the constant speed drive on the level road; For calculating the fuel consumption Pe that exist in the formula of Q (Q=ge.Pe/1.02ua)must result from the calculation of Pe that is the needed power to maintain the constant
8、speed drive on the level road)15.21(3600)(36002aDTawfTaeAuCGfuFFuP)(3600jwifTaeFFFFuPQ-UaFuel consumption performance-needed output power characteristics of engine（负荷特性图）Vehicle Power Equilibrium Graph（功率平衡图） 4.Fule consumption calculation of vehicle with constant speed drive on level road (Stable M
9、ode)（稳定行驶） (Q-Ua) 4.1 Method One: Step: ),(),(02.1/.11111111377.011)15.21(36001102nanuuaaeeeMethodInsertLinealiinruaeAuCGfuPaQuQuupgQgnuPunaagaaDTaeQ-UaUniversal Characteristic Graph of Engine Power Equilibrium Graph 4.2 Method Two：Step: ),(),(02.1/.11111111377.011)15.21(36001102nanuuaaeeeMethodInse
10、rtLinealiinruaeAuCGfuPaQuQuupgQgnuPunaagaaDTae5.Fuel consumption caculation of the vehicle under the drive cycle（循环行驶工况的油耗计算）Basic drive cycle comprises of four parts: acceleration constant speed decelerationparking5.1 The total fuel consumption of deceleration: based on the fuel consumption of idle
11、 condition Two ways for deceleration :correspondingly Losing the pedal and slipping the gears into neutral（空档、怠速） Losing the pedal and keeping the gears at their drive places （挂档、怠速） Two sorts of idle（怠速） fuel consumption: Idle fuel consumption （怠速油耗） Forced idle fuel consumption （强制怠速油耗） 0.28 ml/sU
12、sually the idle fuel consumption caused by the first way is quite similar with the forced idle fuel consumption caused by the second way.So smlwheremlstsmlQQidleondeceleratiidleidlelondeceleratil/28. 0)()()/()()(5.2 The total fuel consumption of constant speed :known quantity: So5.3 The total fuel c
13、onsumption of acceleration: )()100/()/(hTkmlQhkmua)tan(speedtconslQ 11111112111121111211)(3600)15.21(3600)(3600)(36002gepnnuFFudtdugGAuCGfuFFFuFFFFuptuuutuudtdutmethodinsertlinealeawTaverageaaverageaverageaDTaverageajwTaverageajiwfTaverageaeaaaverageaaaaverage)()(.02.1022111111111lQQlQtQtQutsrupgQto
14、nacceleratilnlnlnllaverageaaverageaee So2.3 Influence Factors of Fuel Economy 1.Vehicle usage aspect1.1 Ua （given ig）To analyze the reason of why Q changes according to the trend of high-low-high with the change of Ua high-low-high)100/()100()()(tan)()()tan()()(kmlSQQkmSSSSlQQQQQcycledrivecycledrive
15、lcycledriveondeceleratispeedtconsonacceleraticycledriveidlelondeceleratilspeedtconslonacceleratilcycledrivelg02. 1/aupegeQConclusion: The increase of ge caused by much lower output-power ratio is the main factor causing the increase of Q when the vehicle is driven with low speed;Although ge decrease
16、s greatly for the increase of output-power ratio, the tremendous increase of needed power-pe is the main factor causing the increase of Q when vehicle is driven with high speed; Because of the above two conclusions ,Q could possibly meet its lowest value when the vehicle is driven with the medium ra
17、nge of speed where ge and pe would escape from getting their high value, and we call this range as Economy-Range of Speed （经济车速区间）。QgeratiopoweroutputpuruapegeQpowerneededea02. 1geratiopoweroutputQpuruapegeQpowerneededea02. 1pe1.2 Gear Choice （given Ua） To analyze the reason of why Q is different wi
18、th the change of gear under a given UaConclusion: Q increases with choosing lower gear ;Q decreases with choosing higher gear.It is an evidence to prove that traditional vehicles could not win in both acceleration performance and economy performance.（负荷率）：）（QQQQPfixedugivenggggthDFEFrdCFEFndBFEFstAF
19、EFratiopoweroutputupoweroutputneededEFPeeaeeeea)4()3()2()1 (peUa1.3 MaintenanceHere maintenance mainly refer to the lubrication conditions of all the moving parts of the driveline.We usually use coasting performance （滑行性能）of the vehicle to judge its lubrication conditions and we called this as Coast
20、ing Test (滑行实验检查）.Usually the coasting distance is more than 230 meters with the initial vehicle speed of 50km/h or 30km/h,otherwise the vehicle is considered as the one with bad maintenance. 1.4 The Application of Trailer1）2）Definition Mass Utilization Coefficient（质量利用系数）QT means the fuel consumpti
21、on of each untie mass ;it is the evaluation index of Transportation Efficiency. petraileretrailernoetrailertrailernoggADBDratiopoweroutputADCDratiopoweroutputmassvehiclecapacitycarrying)100/()100/(kmtlQkmlQPetrailerTtrailertrailertrailernotrailer2.Vehicle Structure Aspect 2.1 Engine Engine is an imp
22、ortant determinant of fuel economy performance of the vehicle because it is the place where ge comes from.2.2 Drivelinea)Transmission efficiency-Tb) Gear ratio- igFor making the engine works according to the ideal curve there should be lots of gear ratios to match the ratio of the calculation behind
23、: )02. 1(gupegeQQPePeaneededlossTpe.101377. 01gnnagiurniaiuiuagConclusions: The optimal curve of engine is the place where the output-power ratio gets their minimum value under the corresponding n;Large quantity of gear ratios is the precondition for making the engine work according to its ideal cur
24、ve.Because of the vicious loss of transmission system, Q even increases for the much bigger demand of output power of the engine-Pe 2.3 The gear ratio of final drive gearThe curves of power move rightward with the decrease of i03 The weigh of vehicle itselfAim : TO reduce the weight of vehicle as mu
25、ch as possible Methods: 1. optimization design of structure2. materials 3. craftworkgeratiopoweroutputi04.The shape of bodyAim : To make the CD -Aerodynamic drag coefficient（空气阻力系数） as low as possible. Method : drop-like body or streamlined body 5. TiresRadial-ply tires（子午线轮胎）usually have a better fuel economy than Bias-ply tires (斜交轮胎）for the vehicle.
