Heat Transfer in IC Engine

Prof. Engr. Dr. Mohammad Javed HyderChief Engineer, PIEAS, PAEC

Energy distribution in an

IC engine as a function of engine

speed

Total Power (energy) available in engine

Brake thermal efficiency: (percentage/ fraction of total energy available at crankshaft)

Distribution of energy in an IC engine

Engine

temperatur

es

Piston temperature 4 cylinder, 2.5 liters, SI engine, running at 4600 rpm, WOT

(temperature in oC)

Piston temperature 4 cylinder, 2.5 liters, SI engine, running at 4600 rpm, WOT(temperature in oC)

Piston temperature distribution as a function of engine speed The engine is operating at full load

Engine Warm-up

Variation of engine temperature during the startup of the engine

Heat transfer in Intake system• Walls of the intake manifold are hotter than the flowing gases.

• Gases are heated

• Manifold is hot – By design (exhaust gas, hot coolant, electrical)– By location

• Some systems have hot spot in optimum location• Earlier vaporization => homogeneous mixture• Increased temperature => reduced volumetric efficiency• Supercharging/ Turbocharging => over heating

=> aftercooling

Gas Temperature Variation in side cylinder

Heat transfer in Engine• Heat transfer per unit area

• Heat transfer on the inside surface of the cylinder

• Radiation heat transfer between combustion chamber and cylinder wall

CylinderCombustion Chamber

• In addition to good thermal properties coolant should posses