Principle of gasoline generator
Let's analyze this process:
A working cycle consists of four piston strokes. The so-called piston stroke refers to the distance between the top end point and the bottom dead center of a piston, namely, intake stroke, compression stroke, expansion stroke (work stroke) and exhaust stroke.
In this process, the inlet valve of the engine is opened and the exhaust valve is closed. As the piston from TDC down the only point to move above the piston cylinder volume increases, so that the cylinder pressure below atmospheric pressure, which is caused by vacuum suction in the cylinder, so that air through the intake pipe and the intake valve is sucked into the cylinder, while gasoline and air mixed nozzle spray atomization. In the air at the end of the gas pressure inside the cylinder is about 0.0750.09MPa. At this point the temperature of the combustible mixture in the cylinder has risen to 370-400K.
In order to make the combustible mixture of the inhalation cylinder burn quickly and generate a greater pressure, so that the engine can generate large power, it is necessary to compress the combustible mixture before burning, so as to reduce its volume, increase its density and raise its temperature, that is, the compression process is needed. In this process, the inlet and exhaust valves are all closed, and the crankshaft pushes the piston to move a stroke from the lower stop point to the top stop, that is, the compression stroke. At this point the pressure of the mixture increases to 0.6-1.2MPa, and the temperature is up to 600-700K.
One of the most important concepts in this trip is the compression ratio. The so-called compression ratio is the ratio of the maximum volume of the gas in the cylinder before compression and the minimum volume after compression. Generally, the greater the compression ratio, the mixed gas at the end of the compression pressure and temperature is higher, the combustion speed faster, and thus a greater engine power, economy better. In general, the compression ratio of the car is between 8-10, but the latest Polo has reached a high compression ratio of 10.5, so its torque performance is relatively good. However, when the compression ratio is too large, it can not further improve the combustion situation, instead of abnormal combustion, such as burst combustion and surface ignition.
Burst ignition is an abnormal combustion caused by the high gas pressure and temperature, and the spontaneous combustion of the combustible mixture at the far end of the combustion chamber in the combustion chamber. When burning, the flame propagates outward at a very high speed. Even when the gas is not enough to expand, the temperature and pressure increase sharply, forming pressure waves and advancing with the speed of sound. When this pressure wave strikes the wall of the combustion chamber, it sends out a sharp knock on the cylinder. At the same time, it will also cause a series of bad consequences, such as the engine overheating, the power decline, the increase of fuel consumption. Serious bursting is even caused by the destruction of the valve, the rupture of the axle bush, the breakdown of the spark plug insulator and so on.
In addition to bursts, an engine with high compression ratio may also have to face another problem: surface ignition. This is because the cylinder surface hot and hot place (such as the exhaust valve head, spark plug electrode, carbon deposition at) ignites the mixture produced another abnormal combustion (also called hot ignition or preignition). When the surface ignition occurs, it is accompanied by a strong knock (rather dull). The high pressure produced will increase the load of the engine and reduce the life of the engine.
In this process, the inlet and exhaust doors are still closed. When the piston approaches the top stop, the spark plug emits an electric spark and ignites the compressed combustible mixture. After combustible mixture is burned, a large amount of heat energy is released, and the pressure and temperature of the gas increase rapidly. The maximum pressure can reach 3-5MPa, and the corresponding temperature is up to 2200-2800K. The high temperature and high pressure gas drive the piston to move from the top stop point to the downward stop point, and rotate the crank through the connecting rod to output the mechanical energy. In addition to maintaining the engine itself running, the rest is used for external work. During the movement of piston, the volume of cylinder increases, and the pressure and temperature of gas decrease rapidly. At the end of this journey, the pressure drops to 0.3-0.5MPa and the temperature is 1300-1600K.
When the expansion stroke is close to the end, the exhaust valve opens, and the exhaust is exhausted by the exhaust gas pressure. When the piston moves to the top stop point and moves towards the upper stop point, the exhaust gas is forced to exhaust into the atmosphere, which is the exhaust stroke. In this trip, the pressure in the cylinder is slightly higher than the atmospheric pressure, about 0.105-0.115MPa. When the piston reaches the top stop point, the exhaust stroke ends, and the exhaust temperature is about 900-1200K at this time.
Therefore, we have introduced a working cycle of the engine. During this period, the piston moved back and forth between the upper and the lower stop points for four trips, and correspondingly the crankshaft rotated for two weeks.
The alternator in the gasoline engine is made up of a gasoline generator.