Consider heat engines, the principle of operation of these mechanisms. In the earth's crust and oceans, the reserves of internal energy can be considered unlimited. In order to solve practical problems, it is clearly not enough. The device and principle of operation of a heat engine must be known in order to set in motion lathes, vehicles. A person needs devices that can do useful work.
Heat engines, the principle of which we will consider, are the main on our planet. It is in them that the conversion of internal energy into a mechanical form occurs.
Features of the heat engine
What is the principle of operation of a heat engine? It can be briefly presented in simple experience. If water is poured into a test tube, closed with a cork, brought to a boil, it will fly out. The reason for the cork popping up is because the steam is doing internal work. The process is accompanied by the conversion of the internal energy of the vapor into a kinetic value for the cork. Thermal engines, the principle of which is similar to the described experiment, differ in structure. Instead of a test tube, a metal cylinder is used. The plug is replaced by a piston that fits snugly against the walls moving along the cylinder.
Action algorithm
What is the principle of operation of a heat engine? Grade 10 considers this issue in physics classes. The guys called heat machines mechanisms where the internal energy of the fuel is converted into a mechanical form.
For the engine to perform useful work, a pressure difference must be created on both sides of the piston or blades of a powerful turbine. To achieve such a pressure difference, the temperature of the working fluid increases by thousands of degrees in comparison with its average in the environment. A similar increase in temperature occurs during the combustion process.
Temperature changes
All modern heat engines emit a working fluid. They are called gas, performing useful work in the process of expansion. The initial temperature, denoted by T1, he acquires in the steam boiler of a machine or turbine. This indicator is called the temperature of the heater. In the process of doing work, a gradual loss of gas energy occurs. This leads to the inevitable cooling of the working fluid to a certain indicator T2. The temperature value must be lower than the ambient indicator, otherwise the gas pressure will have a lower indicator than atmospheric pressure, and the engine will not be completed.
T2 is called the temperature of the refrigerator. In its quality is the atmosphere or a special device necessary for the condensation and cooling of the exhaust steam.
Some facts
So, heat engines, the principle of which is based on the expansion of the working fluid, are not able to give all internal energy to do the work. In any case, part of the heat will be transferred to the atmosphere (refrigerator) along with the exhaust steam or exhaust gases of turbines or internal combustion engines.
Efficiency of heat engines
What is the principle of the heat engine? The efficiency of a heat engine depends on the amount of useful work performed by the gas. Given the fact that it is impossible to completely turn internal energy into a heat engine, one can explain the irreversibility of natural processes and phenomena. In that case, if there were a spontaneous return of heat to the heater from the refrigerator, the internal energy would completely turn into useful work by means of a heat engine.
Efficiency is the ratio of the useful work performed by a heat engine to the amount of heat that is transferred to the refrigerator. In physics, it is customary to express this value in percent. This is the principle of operation of a heat engine. Its outline is clear and simple, accessible even to high school students. The laws of thermodynamics make it possible to calculate the maximum value of the coefficient of performance.
The invention of the heat engine
The first inventor of a machine that uses heat was Sadi Carnot. He developed the ideal machine, in which the ideal gas was the working fluid. In addition, the scientist was able to determine the efficiency indicator for such a device using the temperature values of the refrigerator and heater.
Karno was able to determine the relationship between a real heat engine, which operates on the basis of a heater, and a refrigerator, which is air or a condenser. Thanks to the mathematical formula proposed by Carnot for his first ideal heat engine, the maximum value of the efficiency is determined. There is a direct connection between the temperature of the heater and the refrigerator.
In order for the machine to fully function, the temperature should not be less than its indicator in ambient air. If desired, you can increase the temperature of the heater, not forgetting that each solid has a certain heat resistance. As it warms up, it loses its elasticity, and when it reaches the melting temperature it simply melts.
Thanks to the innovations that have been achieved in the modern engineering industry, there is a gradual increase in the efficiency of the heat engine. For example, friction between its separate parts is reduced, losses resulting from incomplete combustion of fuel are eliminated.
Internal combustion engine
It is a heat engine, where high-temperature gases obtained in the process of combustion of various types of fuel inside the chamber are used as a working fluid. Allocate four cycles in the operation of the automobile engine. Among its components, we will name the inlet and outlet valves, the combustion chamber, the piston, the cylinder, the spark plug, the connecting rod, and also the flywheel.
Conclusion
Currently, various types of automobile engines are used: diesel , carburetor. Despite the differences in the fuel used, they have a similar principle of operation. Due to the thermal energy generated in the process of gasoline combustion, the conversion of thermal energy to another form occurs.
At the first stage, the valve moves smoothly downward, the process occurs due to the filling of the chamber with the working mixture. At the end of the first stroke, the inlet valve closes. Next, the piston moves up, while the compression of the working mixture. The appearance of a spark in a candle leads to ignition of a combustible mixture. The pressure that a pair of air and gasoline exert on the piston leads to its spontaneous movement downward, therefore, the beat is called the “stroke”. The crankshaft is driven. At the fourth stage, the exhaust valve opens, the exhaust gases are pushed into the atmosphere.