Energy and the EnvironmentFall2013
Energy and the Environment Fall 2013
Flashbacks of Last LectureThe development of the internal combustionengine (icE)(内燃机) and its supply of liquid fossil fuel transformed bothurban（城市)andrural（农村)communitiesinthetwentiethcenturyThemost commonenginein roadvehicles is the gasolinefueled sparkignition(Sl)reciprocatingengine（火花点火往复式汽油发动机)andthediesel-fueledcompressionignition(Cl)reciprocatingengineengine（压缩点火往复式柴油发动机)islesscommonWorking principles of iE: two-stroke cycle and four-strokecycle
Flashbacks of Last Lecture • The development of the internal combustion engine (ICE) (内 燃机) and its supply of liquid fossil fuel transformed both urban (城市) and rural (农村) communities in the twentieth century • The most common engine in road vehicles is the gasolinefueled spark ignition (SI) reciprocating engine (火花点火往复 式汽油发动机) and the diesel-fueled compression ignition (CI) reciprocating engine engine (压缩点火往复式柴油发动 机) is less common • Working principles of ICE: two-stroke cycle and four-stroke cycle
Flashbacks of Last LectureThe burning of fuel in the cylinder of a reciprocating internalcombustionengine produces mechanical power by exerting aforceonthemovingpistondW = pdvThe total work done by the gas in one cycle of the engine isW= pdV = pVThepowerinputtothepistonPVNNP=Wnn
Flashbacks of Last Lecture • The burning of fuel in the cylinder of a reciprocating internal combustion engine produces mechanical power by exerting a force on the moving piston • The total work done by the gas in one cycle of the engine is • The power input to the piston dW pdV = W pdV pV = c c N pV N P W n n = =
Flashbacks of Last LectureBrakepower（制动功率）Brakemeaneffectivepressure（制动平均有效压力）Brakespecificfuelconsumption（bsfc)（制动油耗率，燃油消耗率，制动单位油耗量）
Flashbacks of Last Lecture • Brake power (制动功率) • Brake mean effective pressure (制动平均有效压力) • Brake specific fuel consumption (bsfc) (制动油耗率, 燃油消 耗率, 制动单位油耗量)
Transportation: Vehicle Power andPerformanceMovingavehicle alongahighwayrequirestheexpenditureofmechanical powertoturnthe wheels一Partofthispowerisneededtoovercomethedragforce(气动阻力)exerted by the air on the moving vehicleAnother part is needed to counter the resistance of thetires movingovertheground,calledtherollingresistance（滚动阻力）-Ifthevehicle is climbingahill,additional powerisneededtoliftitverticallyintheearth'sgravitational field(地球重力场）Whenthevehicleacceleratestoa higher speed,power is needed toincrease the kinetic energy (动能)of the vehicle
Transportation: Vehicle Power and Performance • Moving a vehicle along a highway requires the expenditure of mechanical power to turn the wheels – Part of this power is needed to overcome the drag force (气动阻力) exerted by the air on the moving vehicle – Another part is needed to counter the resistance of the tires moving over the ground, called the rolling resistance (滚动阻力) – If the vehicle is climbing a hill, additional power is needed to lift it vertically in the earth’s gravitational field (地球重力场) – When the vehicle accelerates to a higher speed, power is needed to increase the kinetic energy (动能) of the vehicle