HS code-driven letter of credit checks

Diesel engine structure: basic principle and HS code-driven letter of credit checkselements Diesel engine is a kind of internal combustion engine. Its structure and working principle are similar to gasoline engines, but there are obvious differences in fuel, ignition method and gas compression ratio between the two. Diesel engines use diesel as fuel and use high-pressure fuel injection ignition to realize the process of spontaneous combustion under high compression, thus converting chemical energy into mechanical energy. This article will introduce diesel engines from the perspective of structure and working principle. I. Constructor 1. Cylinder block: The cylinder block of a diesel engine is similar to that of a gasoline engine. It is a kind of casting made of high-strength cast iron or aluminum alloy, with high strength and heat resistance. The cylinder is partly divided into several cylinders, and the cylinders are separated by partitions to prevent cross-interference of gas.Two. Piston: The piston is an important moving part of the cylinder, which is generally made of aluminum alloy or high-strength steel. The upper part of the piston is connected to the flywheel shaft, and the lower part is connected to the connecting rod. In diesel engines, the diameter of the piston and the piston stroke are larger than those of the gasoline engine to meet the higher compression ratio requirements. 3. Crankshaft: The crankshaft is the same as that of a gasoline engine. It is the rotational part of a diesel engine, and the changing heat energy is mechanical energy. In general diesel engines, the crankshaft material requires higher strength, because the compression ratio in diesel engines is higher, and the greater rotational inertia also requires a stronger crankshaft body. Four. Cylinder head: The cylinder head is located at the top of the cylinder block, and the main function is to close the cylinder, fix the valve and injector. Cylinder heads are usually made of aluminum alloy or cast steel, because these materials have good strength, thermal conductivity and weight advantages.5. Connecting rod and crankshaft: The connecting rod is the same as the connecting rod in the gasoline engine, connecting the piston and the crankshaft shaft, so it is also required to bear great pressure. The connecting rod and crank shaft materials are usually made of high-strength steel casting and finishing. 6. Exhaust gas treatment system: The exhaust gas of diesel engines contains a large number of nitrogen oxide compounds, particulate matter and other harmful substances. Therefore, the exhaust gas treatment system is an indispensable part of modern diesel engines, including exhaust pipes, catalysts, particle filters and nitrogen oxide reduction catalysts. 7. Fuel system: The fuel system is an important part of the diesel engine. It is mainly composed of fuel tank, fuel pump, high-pressure nozzle and fuel filter. The fuel system introduces fuel from the fuel tank to the engine and injects it into the oxygen in the cylinder at high pressure to achieve the combustion process.II. Basic working principle The basic working principle of diesel engine can be divided into four stages: intake, compression, combustion and emission. ( 1) Air intake stage: In the air intake stage, the piston moves down to expand the volume of the cylinder. At this time, the intake valve has been opened, and negative pressure is generated inside the cylinder to suck in the outside air. At the same time, the diesel is also sprayed into the incoming air. ( 2) Compression stage: When the piston moves up, the air in the cylinder is compressed, increasing the gas pressure. Diesel fuel is injected into the intake gas and spontaneous combustion occurs after ignition. In the process of combustion, a large amount of heat energy is released. ( 3) Combustion stage: The combustion stage is the most important stage of a diesel engine. When diesel is sprayed into the intake gas, due to the influence of high pressure and gas temperature, the diesel oil mist quickly evaporates and mixes with air, and then ignites to form combustion.During the combustion process, the internal pressure of the gas increases rapidly, and the piston is pushed down to release heat energy. ( 4) Emission stage: The emission stage is the last stage of the diesel engine. The engine treats the exhaust gas through the exhaust gas treatment system, filtering out a large number of nitrogen oxide compounds, particulate matter and other harmful substances, and releasing it to the environmentally friendly exhaust gas. The treated exhaust gas is discharged into the discharge pipe. In a word, diesel engine is a kind of high-efficiency and energy-saving internal combustion engine. The structure and working principle of the engine are similar to those of the gasoline engine, but there are large differences in fuel and ignition methods. With the development of science and technology, diesel engines have become the main power equipment in all walks of life.

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