combustion without harmful results. The temperature in the combustion chamber during the burning of the fuel is well above the melting point of iron. Therefore, if nothing is done to cool the engine during operation, valves will burn and warp, lubricating oil will thin and break down, and bearings and pistons will overheat, resulting in engine seizure. (ON #300) Heat is moved from hot spots in the engine in the following ways. (1) Conduction. Heat is a form of energy, and when it comes into contact with matter it makes the atoms and molecules move. Once atoms or molecules are moving, they collide with other atoms or molecules, making them move too. In this way, the heat is transferred through matter. (2) Convection. Convection occurs when a substance that can flow, like water or air is heated. When this medium is heated it becomes less dense (lighter) and rises. As it rises it forces the surrounding medium down and closer to the heat source. This sets up a circular heating and cooling motion of the fluid medium. (3) Radiation. Radiation happens when heat as energy waves, called infrared waves, directly from its source to something else. This is how the heat gets from the Sun to the Earth. All hot things radiate heat to cooler things. When the heat waves hit the cooler material, they make the molecules of the cooler object speed up. When the molecules of that material speed up, the object becomes hotter. (ON SLIDE #301) (4)There are other sources of heat dissipation for the engine in addition to the cooling system. (a) The exhaust system dissipates as much, if not more, heat than the cooling system, although that is not its purpose. (b) The engine oil removes heat from the engine and dissipates it to the air from the sump or oil cooler. (c) A measurable amount of heat is dissipated to the air through radiation from the engine. (ON SLIDE #302) Air Cooled Engines. b.
combustion without harmful results. The temperature in the combustion chamber during the burning of the fuel is well above the melting point of iron. Therefore, if nothing is done to cool the engine during operation, valves will burn and warp, lubricating oil will thin and break down, and bearings and pistons will overheat, resulting in engine seizure. (ON #300) Heat is moved from hot spots in the engine in the following ways. (1) Conduction. Heat is a form of energy, and when it comes into contact with matter it makes the atoms and molecules move. Once atoms or molecules are moving, they collide with other atoms or molecules, making them move too. In this way, the heat is transferred through matter. (2) Convection. Convection occurs when a substance that can flow, like water or air is heated. When this medium is heated it becomes less dense (lighter) and rises. As it rises it forces the surrounding medium down and closer to the heat source. This sets up a circular heating and cooling motion of the fluid medium. (3) Radiation. Radiation happens when heat as energy waves, called infrared waves, directly from its source to something else. This is how the heat gets from the Sun to the Earth. All hot things radiate heat to cooler things. When the heat waves hit the cooler material, they make the molecules of the cooler object speed up. When the molecules of that material speed up, the object becomes hotter. (ON SLIDE #301) (4)There are other sources of heat dissipation for the engine in addition to the cooling system. (a) The exhaust system dissipates as much, if not more, heat than the cooling system, although that is not its purpose. (b) The engine oil removes heat from the engine and dissipates it to the air from the sump or oil cooler. (c) A measurable amount of heat is dissipated to the air through radiation from the engine. (ON SLIDE #302) b. Air Cooled Engines.
Completed%20ENGINES%20DO.docx