HS code-driven import quality checks

List of the catalogue of this article:

• 1,HS code-driven import quality checks Why should high-horsepower diesel engines (such as marine diesel engines) use two-stroke design?
• 2、What is the difference between four-stroke and two-stroke diesel engine

Why should high-horsepower diesel engines (such as marine diesel engines) use two-stroke design?

1. The compression ratio of two-stroke diesel engines is greatly improved compared with that of four-stroke diesel engines, and the efficiency of diesel engines is improved with the increase of the compression ratio. 4. Most of the two-stroke diesel engines are DC air sweeping, and the air sweeping is sufficient.

2. The form of two strokes is more efficient, and the output torque will be much larger than that of four strokes.Heavy oil should be used as fuel. The combustion efficiency of heavy oil will be higher than that of ordinary diesel. Less pollution waste is excluded during combustion, and the calorific value of combustion is also very high, and marine diesel engines just need these properties.

3. The working principle of a two-stroke diesel engine. A diesel engine that completes a working cycle through the two-stroke piston is called a two-stroke diesel engine. The oil engine completes a working cycle and the crankshaft only rotates once. Compared with the four-stroke diesel engine, it improves the working ability. In terms of specific structure and working principle There is also a big difference.

4. Due to the loss of mixed gas in the two-stroke gasoline engine, the economy is poor, and the application on large and medium-sized cars is limited. However, due to its advantages such as simple structure, light weight and low manufacturing cost, small-displacement engines for mopeds and mini cars are widely used.

5. The diesel engine with air hole-type DC air exchange is shown on the left in the figure below. Its air exchange is completed by the upper and lower intake and exhaust, so it is called a two-stroke diesel engine with air hole-type DC air exchange. The opening and closing of the inlet and exhaust holes are controlled by the upper and lower pistons respectively.

6. Complete two actions to turn off all intake and exhaust air and compress the mixed gas. Every two strokes complete the work, so it is called the second stroke. Advantages: simple structure, small size, light weight and low cost; stable operation and small vibration; fast speed up for short distances. Disadvantages: high fuel consumption (lubricating oil, gasoline); high temperature, high pollution; loud exhaust noise.

The difference between a two-stroke engine and a four-stroke engine

The difference in working principle Whether it is a two-stroke engine or a four-stroke engine, it must go through the four working processes of intake (sweeping), compression, combustion and expansion, and exhaust to complete Become a working cycle.

The difference between the lubrication method: the piston connecting rod mechanism of the four-stroke engine adopts the crankshaft splash lubrication method; the camshaft, rocker arm, valve, etc. adopt the pump pressure lubrication method.Two-stroke engines generally adopt mixed lubrication or separation lubrication.

In theory, the power of a two-stroke engine should be twice that of a four-stroke engine (but in fact it is only 5~7 times). The engine has higher power, better power, and the vibration of the engine is relatively small.

The structure is different. The thermal part of the two-stroke is mainly composed of cylinder head, cylinder, piston, piston ring and other parts, and the thermal part of the four-stroke is mainly composed of cylinder head, cylinder head head, cylinder head, piston, piston ring and gas distribution mechanism.

Difference: Every two weeks of rotation of the four-stroke engine crankshaft, the upper and lower piston complete a work cycle. Every week of rotation of the two-stroke engine crankshaft, the piston completes a work cycle.

What are the characteristics of the two-stroke internal combustion engine and the role of each stroke internal combustion engine

1. The structure of the stroke engine is simple and the weight is light, but the efficiency is low, the noise is loud and the pollution is serious; the four-stroke engine is high efficiency , the noise is low and the discharge is clean, but the structure is relatively complex and the weight is large. At present, most cars and machinery use 4-stroke engines.

2. Every time the two-stroke engine and the four-stroke engine complete a working cycle, their inlet and exhaust valves or inlet, exhaust and sweep ports are only opened and closed once, but the time period of opening and closing is different. Features of engine performance: Every time the two-stroke engine crankshaft rotates around, there is a working stroke.

3. Therefore, the air exchange quality of the two-stroke internal combustion engine is poor, the fuel efficiency is not high, and the fuel consumption of the whole vehicle is relatively high. Four-stroke engine: Advantages: Because the intake and exhaust of the four-stroke engine is independent, the intake and exhaust efficiency is high, the combustion is sufficient, and it is economical and fuel-efficient.

4. Different structures: the second stroke is mainly composed of cylinder head, cylinder, piston, piston ring and other components, while the four stroke is mainly composed of cylinder head, cylinder head, piston, piston ring and air distribution mechanism.

5. The so-called four-stroke engine refers to the engine crankshaft every two weeks of rotation through the four strokes of intake, compression, work and exhaust to complete a working cycle, while the two-stroke engine only needs the crankshaft to rotate for a week and go through two strokes to complete a working cycle.

6. Four-stroke deliveryAdvantages of motivation: The processes of air intake, compression, expansion (explosion) and exhaust are carried out separately, so the work is reliable, efficient, stable, and has a large speed range from low speed to high speed. There is no airflow loss like a two-stroke engine, and the fuel consumption rate is low.

What is the difference between four-stroke and two-stroke diesel engine

The difference between two-stroke diesel engine and four-stroke diesel engine is that the crankshaft of the two-stroke diesel engine rotates once, and the four-stroke diesel engine rotates the crankshaft twice and does it once. Work. The diesel engine has a gas distribution mechanism from top to bottom. Cylinder head. Fuel system. Cylinder block. Cooling system. Crankshaft connecting rod mechanism. Lubrication system. Oil sall.

The working principle is different, whether it is two kinds of processThe motive is still a four-stroke engine, which needs to go through the four working processes of intake (sweeping), compression, combustion and expansion, and exhaust to complete a working cycle.

Compared with a four-stroke engine, the power is greater when the speed is the same. Compared with the four-stroke, it has twice the explosive power. Therefore, at the same volume, if the average effective pressure is the same, the power is 2 times (actually 7). B. Disadvantages: The time of the intake and exhaust process is short, so the fuel loss is large.