Ch. 10 Heat Transfer in Engines Contents 10.1 Energy distribution 10.2 Engine temperatures 10.3 Heat transfer in intake & exhaust system, combustion chamber 10.6 Engine operating variables on heat transfer 10.7 Cooled engines and modern trends

10.1 Energy distribution 1. For any engines  

10.2 Engine temperatures 1. a typical temperature distribution   Temperatures of a typical SI engine as s function of time after cold start-up Typical temperature in an SI engine

10.3 Heat transfer in intake system 1. a typical temperature distribution   Steady state temperature of intake valves : 200-300˚C Hot spot in intake manifold to accelerate fuel evaporation

10.4 Heat transfer in combustion chamber 1. heat transfer through a cylinder wall  

10.4 Heat transfer in combustion chamber Cooling of piston Convection to the oil Conduction by the piston rings Conduction down the connecting rod to the oil

10.5 Heat transfer in exhaust system Exhaust temperatures of SI engine : 400-600 ˚C with extremes of 300-900 ˚C Exhaust temperatures of CI engine : 200-500 ˚C

10.6 Engine operating variables on heat transfer Engine size: larger engine more efficient Engine speed: as engine speed is increased, heat transfer increases Load: as load is increased mass flow rate of air and fuel goes up and heat transfer goes up. Spark timing Equivalence ratio Evaporative cooling-water injection Inlet air temperature Coolant temperature Engine materials Compression ratio Knock Swirl and squish

10.7 Cooled engine Cooling system of water-cooled engine Air cooled aircraft engine

Radiator of a water-cooled engine