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Cơ bản Các đơn vị , thông số , ký hiệu trong tính toán động cơ đốt trong!

Thảo luận trong 'Động cơ' bắt đầu bởi otohui, 22/10/11.

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  1. otohui
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    Tài xế O-H
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    Tham gia ngày:
    24/3/09
    Số km:
    2,567
    Được đổ xăng:
    74
    Mã lực:
    381
    Xăng dự trữ:
    350 lít xăng

    Cylinder Swept Volume (Vc):
    where:
    Vc= cylinder swept volume [cm3 (cc) or L]
    Ac = cylinder area [cm2 or cm2/100]
    dc = cylinder diameter [cm or cm/10]
    L = stroke length (the distance between the TDC and BDC) [cm or cm/10]
    BDC = Bottom Dead Center
    TDC = Top Dead Center
    * Increase the diameter or the stroke length will increase the cylinder volume, the ratio between the cylinder diameter/cylinder stroke called “bore/stroke” ratio.

    - “bore/stroke” >1 is called over square engine, and is used in automotive engines

    - “bore/stroke” =1 is called square engine

    - “bore/stoke” <1 is called= under square engine, and is used in tractor engine

    Engine Swept Volume (Ve):
    where:
    Ve = engine swept volume [cm3 (cc) or L]
    n = number of cylinders
    Vc = cylinder swept volume [cm3 (cc) or L]
    Ac = cylinder area [cm2 or cm2/100]
    dc = cylinder diameter [cm or cm/10]

    * The units of cylinder swept volume is measured in (cm3, cubic centimeter (cc), or liter)

    - Ve for small engines, 4 cylinder engines is (750 cc:1300 cc)

    - Ve for big engine, 8 cylinder engines is (1600 cc:2500 cc)

    Compression Ratio (r):

    where:

    r = compression ratio

    Vs = cylinder swept volume (combustion chamber volume) [cc, L, or m3]

    Vc = cylinder volume [cc, L, or m3]

    * Increase the compression ratio increase engine power

    - r (gasoline engine) = 7:12, the upper limit is engine pre ignition

    - r (diesel engine) = 10:18, the upper limit is the stresses on engine parts

    Engine Volumetric Efficiency (hv):

    where:

    hV = volumetric efficiency

    Vair = volume of air taken into cylinder [cc, L, or m3]

    Vc = cylinder swept volume [cc, L, or m3]

    * Increase the engine volumetric efficiency increase engine power

    - Engine of normal aspiration has a volumetric efficiency of 80% to 90%

    - Engine volumetric efficiency can be increased by using:

    (turbo and supper charger can increase the volumetric efficiency by 50%)

    Engine Indicated Torque (Ti):

    where:

    Ti = engine indicated torque [Nm]

    imep = indicated mean effective pressure [N/m2]

    Ac = cylinder area [m2]

    L = stroke length [m]

    z = 1 (for 2 stroke engines), 2 (for 4 stroke engines)

    n = number of cylinders

    θ = crank shaft angle [1/s]

    Engine Indicated Power (Pi):

    where:

    imep = is the indicated mean effective pressure [N/m2]

    Ac = cylinder area [m2]

    L = stroke length [m]

    n = number of cylinders

    N = engine speed [rpm]

    z = 1 (for 2 stroke engines), 2 (for 4 stroke engines)

    Vc = cylinder swept volume [m3]

    Ve = engine swept volume [m3]

    Ti = engine indicated torque [Nm]

    ω = engine angular speed [1/s]

    Engine Mechanical Efficiency (hm):

    where:

    hm = mechanical efficiency

    Pb = engine brake power [kW]

    Pi = engine indicated power [kW]

    Pf = engine friction power [kW]

    Engine Specific Fuel Consumption (SFC):
    where:
    SFC = specific fuel consumption [(kg/h)/kW, kg/(3600 s x kW), kg/(3600 kJ)]

    FC = fuel consumption [kg/h]

    Pb = brake power [kW]

    Engine Thermal Efficiency (hth):

    where:

    hth = thermal efficiency

    Pb = brake power [kW]

    FC = fuel consumption [kg/h = (fuel consumption in L/h) x (ρ in kg/L)]

    CV = calorific value of kilogram fuel [kJ/kg]

    ρ = relative density of fuel [kg/L]
     

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