《汽车理论》课程教学课件（英文讲稿）第2章 汽车燃油经济性 Fuel Economy 2.3 Influence Factors of Fuel Economy

2.1/2.2内容回顾1.EvaluationIndex（评价指标）L/100km , L/t100km, MPG,km/L;等速行驶工况，循环行驶工况2.Calculation of Fuel Consumption（燃油经济性计算）P,b(L / 100km)O1.02u.pg等速工况：两种方法2加速工况：a-averagel(F+Fw +F)Per3600nrDAu?SGduUa-averagela-averagel(Gf+dt3600nt21.15gaveragel

2.1/2.2内容回顾 1.Evaluation Index(评价指标) L/100km ，L/t·100km，MPG，km/L； 等速行驶工况，循环行驶工况 2. Calculation of Fuel Consumption （燃油经济性计算） 等速工况：两种方法 加速工况： ( /100 ) 1.02 e s a P b Q L km u g   2 1 1 1 1 1 ( ) 3600 ( ) 21. 360 15 0 a averag a average e f W j e D a average average T T u C Au G du Gf g dt u p F F F             

2.3 Influence Factors of Fuel Economy1.AnalyzingBasis（分析依据）（使用因素）2. Vehicle usage aspect3.VehicleStructureAspect（结构因素）

2.3 Influence Factors of Fuel Economy 1. Analyzing Basis(分析依据) 2. Vehicle usage aspect（使用因素） 3. Vehicle Structure Aspect（结构因素）

P..bAnalyzing BasisQs[L/100km]1.02u.pgUaP(F, + Fw)[kW]3600 nlb,[g/kW - h][km/h]uabCFbQF.+F[L / 100km]3672nrpgnr1CpAu.?F=GfC = const, C21.153672pgCFbO[L/100km]nroutput－powerratio(负荷率）=b个Q,α F、b、V.nr

[L/100km] 1.02 e s a P b Q u g      a P [kW] 3600 , [g/kW h] u [km/h] a e f W T u F F b     [ /100 ]   3672 s f W T T b CFb Q F F L km    g     2 1 , 3672 21.15 C Au D a C const C F Gf g     ， [L/100km] s T CFb Q   1 , s T Q F b    、 、 output power ratio( ) b     负荷率 Analyzing Basis

P.increases with theb(g / kW .h)n,decrease of b under thegiven n. (in most instance);houtput-power ratio alwaysWincreases with the decreaseof b(in mostinstance);b meets its minimum valuewhen the output-powerratio come close to 80%Pe2output- power ratio :PeoP6elminPeoP(kW)Fuel consumption performance-neededoutput power characteristics of engine

b g kW h ( / )  Fuel consumption performance-needed output power characteristics of engine ( ) P kW e 1 n 2 n 3 n min b P e1 P e0 P e2 • Pe increases with the decrease of b under the given n. (in most instance); • output-power ratio always increases with the decrease of b. (in most instance); • b meets its minimum value when the output-power ratio come close to 80%. 2 0 - e e P output power ratio P 

Energy Balance of a car with drive cycle(City or High-way)IdleParkingAccessories(A/Cetc.)Air Resistance17.2%(3.6%)2.2%(1.5%)2.6%(10.9%)18.2%(25.6%)12.6%EnergyRolling Resistance(20.2%)EngineofFuel4.2%(7.1%100%BrakingWaste ofWaste of engine5.8%(2.2%Cincluding heatwastetransmissionand mechanism waste5.6%(5.4%)62.4%(69.2%)(High-way)Drive Cycle:City

Energy Balance of a car with drive cycle (City or High-way） Engine Idle Parking 17.2%(3.6%) Accessories(A/C etc.) 2.2%(1.5%) Waste of engine （including heat waste and mechanism waste 62.4%(69.2%) Waste of transmission 5.6%(5.4%) Braking 5.8%(2.2%) Rolling Resistance 4.2%(7.1%) Air Resistance 2.6%(10.9%) Energy of Fuel 100％ 12.6% (20.2%) 18.2% (25.6%) Drive Cycle：City（High-way）

Vehicle usage aspect1. ua (given ig)Curve of Q~u,-→ug(EconomyRangeofSpeed)

 Curve of Qs~ua →ug（Economy￾Range of Speed） 1. ua （given ig） Vehicle usage aspect

Curve of Q~u,（high gear),(L / 100km)Kua=F1u. 小= Pamedd= output power ratio = b个个CFbOsAnT>0. 个Vhigh-low-highug(Economy Range of Speed) u.(km/ h)

Curve of Qs~ua（high gear） /100 ) Q L km （S u (k m/ h) a V ( ) g u Economy Range of Speed b s T a a e needed CFb Q s u F u P Q             output power ratio high low high  

Curve of Q-u,（high gear)0,(L /100km)ua个=Pe-neded个个,F个个O-CFbH01output power ratio个L6+或个Vug(Economy Range of Speed) u.(km/ h)

/100 ) Q L km （S u (k m/ h) a V , T a e needed CFb Q s u P F Q b              output power ratio 或 Curve of Qs~ua（high gear） ( ) g u Economy Range of Speed

ConclusionThe increase of b caused by much lower output-powerratio is the main factor causing the increase of Q, whenthe vehicle is driven with lowspeed;Although b decreases greatly for the increase of output-power ratio, the tremendous increase of needed power-peis the main factor causing the increase of Q. when vehicleis drivenwithhighspeed;Because of the abovetwo conclusions,Q,could possiblymeet its lowest value when the vehicle is driven with themedium range of speed where b and pe would escapefrom getting theirhigh value, and we call this range asEconomy-RangeofSpeed（经济车速区间）

• The increase of b caused by much lower output-power ratio is the main factor causing the increase of Qs when the vehicle is driven with low speed; • Although b decreases greatly for the increase of output￾power ratio, the tremendous increase of needed power-pe is the main factor causing the increase of Qs when vehicle is driven with high speed; • Because of the above two conclusions, Qs could possibly meet its lowest value when the vehicle is driven with the medium range of speed where b 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）。 Conclusion

Fuel consumption curve of a carQs(/100km)II'III/IVVVI1ua(km/h)50709011030

Fuel consumption curve of a car