July 09 2023
Popular Science: How a Car Engine Works
Speaking of a car engine, I think everyone knows that it belongs to heart of a car, mainly to provide enough power for normal driving. Although everyone knows that a car engine is a very important part, understanding of how it works is not very deep. Today I will introduce you~
1. Working stroke
At end of compression stroke, spark plug generates electrical sparks to ignite gas mixture and burns quickly, so that temperature and pressure of gas rise rapidly, thereby pushing piston to move from top dead center. at BDC, and crankshaft rotates through connecting rod. Work until piston reaches BDC and work ends.
When work starts, gas pressure and temperature in cylinder increase sharply, instantaneous pressure can reach 3MPa~5MPa, and instantaneous temperature can reach 2200K~2800K.
2. Intake stroke
The crankshaft drives piston from top dead center to bottom dead center, opening intake valve and closing exhaust valve. As piston moves, internal volume of cylinder gradually increases with formation of a vacuum, so combustible mixture is sucked into cylinder through intake valve until piston reaches bottom dead center and ends when intake valve closes.
Due to intake resistance of intake system, gas pressure in cylinder is lower than atmospheric pressure at intake end, which is about 0.075Mpa ~ 0.09Mpa. Due to heating of high temperature components such as cylinder walls and pistons and high temperature residual exhaust gases from previous cycle, temperature of gases rises to 370-440K.
3. Release beat
As power stroke nears end, exhaust valve opens, intake valve closes, and crankshaft pushes piston from bottom dead center to top dead center through connecting rod. The exhaust gas is expelled from cylinder under its own residual pressure and is driven by piston, when piston reaches top dead center, exhaust valve closes and exhaust stops. Due to exhaust drag in exhaust system, when exhaust stroke ends, cylinder pressure is slightly higher than atmospheric pressure, about 0.105Mpa ~ 0.115Mpa, and temperature is about 900K ~ 1200K.
Did you understand all this?
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