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Types of Thermal Machine

2021-08-27

The internal combustion engine is a kind of power machine. It is a heat engine that burns fuel inside the machine and directly converts the heat energy it emits into power. In a broad sense, internal combustion engines include not only reciprocating piston internal combustion engines, rotary piston engines and free piston engines, but also gas turbines and jet engines of rotary vane type, but generally referred to as internal combustion engines refer to piston internal combustion engines. The reciprocating piston type internal combustion engine is the most common. Piston-type internal combustion engines mix fuel and air, burn them in the cylinder, and release the heat energy to produce high-temperature and high-pressure gas in the cylinder. The gas expansion pushes the piston to do work, and then the mechanical work is output through the crank connecting rod mechanism or other mechanisms to drive the driven machinery to work.
The common ones are diesel engines and gasoline engines, which convert internal energy into mechanical energy and change internal energy by doing work.
Four strokes of internal combustion engine
1. Gasoline engine
Internal combustion engine using gasoline as fuel
1. Structure
Intake valve, exhaust valve, spark plug, cylinder, piston, connecting rod, crankshaft.
2. Movement process
One working cycle of a gasoline engine has to go through four strokes, which is a four-stroke internal combustion engine. In one of its working cycles, the piston reciprocates twice each, and only the third stroke internal combustion engine pushes the piston to do work.
Stroke: The piston moves up or down in the cylinder at a time called a stroke of the internal combustion engine.
During the work stroke, the gas does work on the piston, and the internal energy is converted into mechanical energy. The remaining three strokes are completed by the inertia of the flywheel mounted on the crankshaft (the compression stroke is the upward movement of the piston, compressing the fuel mixture, and converting mechanical energy into internal energy).
Inhalation stroke: the intake valve opens, the exhaust valve closes, the piston moves downward, and the mixture of gasoline and air enters the cylinder.
Compression stroke: The intake and exhaust valves are closed, the piston moves upward, and the fuel mixture is compressed.
Work stroke: Both the intake valve and exhaust valve are closed, and the spark plug ignites with the generated electric spark to make the mixture burn vigorously, produce high-temperature and high-pressure gas, push the piston down, drive the crankshaft to rotate, and do work externally.
Exhaust stroke: The intake valve remains closed, the exhaust valve opens, and the piston moves upward, expelling the exhaust gas from the cylinder.
2. Diesel engine
The difference between an internal combustion engine using diesel fuel and a gasoline engine is that the spark plug of the gasoline engine is changed to a fuel injector and the ignition of the gasoline engine is changed to the compression ignition method of the diesel engine. A diesel engine is different from a gasoline engine in that it sucks in air instead of mixed gas, and the fuel is not ignited by electric spark but by compression ignition.
Structure: intake valve, exhaust valve, fuel injector, cylinder, piston, connecting rod, crankshaft
Working process: suction, compression, work, exhaust.

The external combustion engine is a closed-cycle reciprocating piston heat engine with external combustion. Because it was invented by R Stirling of Scotland in 1816, it is also called the Stirling engine. The new type of external combustion engine uses hydrogen as a working medium, and a certain volume of working medium is filled in four closed cylinders. One end of the cylinder is a hot cavity, and the other end is a cold cavity. The working fluid is compressed in the low-temperature cold cavity, and then flows to the high-temperature hot cavity to be rapidly heated and expand to perform work. The fuel is continuously burned in the combustion chamber outside the cylinder, and is transferred to the working fluid through the heater. The working fluid does not directly participate in the combustion and is not replaced.
Because the external combustion engine avoids the shock and explosion problems of traditional internal combustion engines, it achieves high efficiency, low noise, low pollution and low operating costs. The external combustion engine can burn various combustible gases, such as natural gas, biogas, petroleum gas, hydrogen, coal gas, etc., as well as liquid fuels such as diesel and liquefied petroleum gas, as well as wood and solar energy. As long as the thermal chamber reaches 700°C, the equipment can perform work. The lower the ambient temperature, the higher the power generation efficiency. The power generation efficiency of the STM4-120 25kW-class unit provided by the company is 29.6%, which is much higher than that of an internal combustion engine of the same capacity. The biggest advantage of the external combustion engine is that the output and efficiency are not affected by altitude, and it is very suitable for use in high altitude areas.

The equipment currently has three models to choose from, the "cogeneration" type, the "solar-external combustion hybrid power generation" type, the "waste heat utilization" type, and the vehicle type and mobile on-site power supply.

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