The Stirling engine

1. The Stirling engine Explanations of its function

2. 1 Displacement of gas A large volume of gas is expelled towards the bottom of the container (beaker). Variation in temperature Since the base of the container is at a high temperature, this volume of gas heats up. Variation in pressure The increase in temperature of the displaced gas creates an increase in the global pressure of the system. (The volume is almost constant) p1 p2 ----- = ------- T1 T2 Labour carried out The increase in volume of the gas causes upward displacement of the engine piston rod. At that moment, the crankshaft is in the ideal position to receive the force that causes the rotation of the engine. Applied force The pressure of the gas is captured by the engine piston (membrane). This in turn applies an upwards force on the crankshaft by means of the line out and the rod. Force = Pressure · Surface Labour = Force · Displacement Variation in volume The volume of gas in the system increases and creates a decrease in the pressure. (The temperature is almost constant). p1 · V1 = p2 · V2

3. Displacement of gas A large volume of gas is expelled towards the bottom of the container (beaker). Variation in temperature Since the base of the container is at a high temperature, this volume of gas heats up. Variation in pressure The increase in temperature of the displaced gas creates an increase in the global pressure of the system. (The volume is almost constant) p1 p2 ----- = ------- T1 T2 Labour carried out The increase in volume of the gas causes upward displacement of the engine piston rod. At that moment, the crankshaft is in the ideal position to receive the force that causes the rotation of the engine. Applied force The pressure of the gas is captured by the engine piston (membrane). This in turn applies an upwards force on the crankshaft by means of the line out and the rod. 1 Force = Pressure · Surface Labour = Force · Displacement Variation in volume The volume of gas in the system increases and creates a decrease in the pressure. (The temperature is almost constant). p1 · V1 = p2 · V2

4. 2 Labour carried out At this precise moment, the force applied on the piston does not cause any displacement. The crankshaft is in a position where transformation of movement is impossible. The engine now turns on its momentum thanks to its flywheel. Labour = Force · Displacement Labour = Force · 0 m Labour = 0 N·m

5. 3 Displacement of gas A large volume of gas is expelled towards the top of the container (beaker). Variation in temperature Since the top of the container is at a low temperature, this volume of gas cools down. Variation in pressure The decrease in temperature of the displaced gas creates an decrease in the global pressure of the system. (The volume is almost constant) p1 p2 ----- = ------- T1 T2 Labour carried out The decrease in volume of the gas causes downward displacement of the engine piston rod. At that moment, the crankshaft is in the ideal position to receive the force that causes the rotation of the engine. Applied force The vacuum of the gas is captured by the engine piston (membrane). This in turn applies an downwards force on the crankshaft by means of the line out and the rod. Force = Pressure · Surface Labour = Force · Displacement Variation in volume The volume of gas in the system decreases and creates a increase in the pressure. (The temperature is almost constant). p1 · V1 = p2 · V2

6. 3 Displacement of gas A large volume of gas is expelled towards the top of the container (beaker). Variation in temperature Since the top of the container is at a low temperature, this volume of gas cools down. Variation in pressure The decrease in temperature of the displaced gas creates an decrease in the global pressure of the system. (The volume is almost constant) p1 p2 ----- = ------- T1 T2 Labour carried out The decrease in volume of the gas causes downward displacement of the engine piston rod. At that moment, the crankshaft is in the ideal position to receive the force that causes the rotation of the engine. Applied force The vacuum of the gas is captured by the engine piston (membrane). This in turn applies an downwards force on the crankshaft by means of the line out and the rod. Force = Pressure · Surface Labour = Force · Displacement Variation in volume The volume of gas in the system decreases and creates a increase in the pressure. (The temperature is almost constant). p1 · V1 = p2 · V2

7. 4 Labour carried out At this precise moment, the force applied on the piston does not cause any displacement. The crankshaft is in a position where transformation of movement is impossible. The engine now turns on its momentum thanks to its flywheel. Labour = Force · Displacement Labour = Force · 0 m Labour = 0 N·m

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28. N.B. Charles’ Law (the effect of temperature on the volume of a gas) can be used during an explanation. It creates a shortcut, however, that means that the explanation is less complete. Indeed, since pressure is not present, there is a risk that applied force will not be tackled. Charles’ Law V1 V2 ----- = ------- T1 T2