(1) The four-stroke gasoline engine mixes air and gasoline in a certain proportion to form a good mixture for the automobile engine. During the intake stroke, the mixed gas is sucked into the cylinder, and the mixed gas is compressed, ignited, and burned to generate heat energy. The high-temperature and high-pressure gas acts on the top of the piston, pushing the piston to perform linear reciprocating motion, and the mechanical energy is output outward through the connecting rod, crankshaft, and flywheel mechanisms. The four-stroke gasoline engine completes a working cycle in the intake stroke, compression stroke, power stroke and exhaust stroke. (2) The intake stroke piston is driven by the crankshaft and moves from top dead center to bottom dead center. At this time, the intake valve opens, the exhaust valve closes, and the crankshaft rotates 180°. During the movement of the piston, the volume of the cylinder gradually increases, the gas pressure in the cylinder gradually decreases from pr to pa, and a certain degree of vacuum is formed in the cylinder. The mixture of air and gasoline is sucked into the cylinder through the intake valve and further mixed in the cylinder to form a combustible mixture. Due to the resistance of the air intake system, at the end of the air intake, the gas pressure in the cylinder is less than the atmospheric pressure p0, that is, Pa=(0.80~0.90)P0. The temperature of the combustible mixture entering the cylinder rises to 340~400K due to the heating of high-temperature components such as the intake pipe, cylinder wall, piston top, valve, and combustion chamber wall, as well as the mixing with the residual exhaust gas. (3) Compression stroke During the compression stroke, the intake valve and exhaust valve close at the same time. The piston moves from bottom dead center to top dead center and the crankshaft rotates 180°. When the piston moves upward, the working volume gradually decreases, and the pressure and temperature of the mixture in the cylinder continue to rise after being compressed. When the compression ends, the pressure pc can reach 800~2000kpa and the temperature can reach 600~750k (4) During the power stroke, when the piston approaches the top dead center, the spark plug ignites the combustible mixture, and the combustion of the mixture releases a large amount of heat energy, causing the gas in the cylinder to The pressure and temperature rise rapidly. The maximum combustion pressure pZ is 3000~6000kPa, and the temperature TZ is 2200~2800k·k. The high-pressure gas pushes the piston from top dead center to bottom dead center, and outputs mechanical energy through the crank connecting rod mechanism. As the piston moves downward, the volume of the cylinder increases and the gas pressure and temperature gradually decrease. When reaching point B, the pressure drops to 300~500kPa and the temperature drops to 1200~1500KK. During the power stroke, the intake valve and exhaust valve close and the crankshaft rotates 180°. (5) Exhaust stroke During the exhaust stroke, the exhaust valve opens, the intake valve remains closed, the piston moves from bottom dead center to top dead center, and the crankshaft rotates 180°. When the exhaust valve is opened, the burned exhaust gas is discharged out of the cylinder under the pressure difference between the inside and outside of the cylinder, and on the other hand, it is discharged out of the cylinder through the extrusion of the piston. Due to the resistance of the exhaust system, the pressure at the exhaust end R is slightly higher than the atmospheric pressure, that is, PR=(1.05~1.20)P0. Exhaust temperature TR=900~1100K. When the piston moves to top dead center, there is still a certain volume of exhaust gas in the combustion chamber that cannot be discharged. This part of exhaust gas is called residual exhaust gas.