AER100 Lecture Notes - Lecture 5: Reciprocating Engine, Connecting Rod, Mechanical Advantage
Document Summary
Four stroke cycle: intake: drawing in of fuel/air mixture. Fuel is only combustible in gaseous state: combustion: burning of the fuel air charge, valves remain closed, spark plug fires to ignite fuel/air mixture. Fuel/air mixture burns and expands instead of exploding: heat is converted into mechanical energy as piston moves down. At tdc, the connecting rod has little mechanical advantage on crankshaft and pressure inside cylinder is relatively low so little energy is converted into movement. Shortly after tdc, the connecting rod still has little mechanical advantage, but the burning fuel has increased pressure so more energy is converted into movement. Increases stress on components: combustion produces maximum energy 15-20 degrees after tdc, when crankshaft arm is horizontal, connecting rod has most mechanical advantage, but pressure in cylinder has decreased. Maximum energy transfer occurs between 15-20 degrees and horizontal. Near bdc, connecting rod has less mechanical advantage, and little energy is converted into movement.
