Two-stage piston air compressor

Contents

INTRODUCTION

1 Description of design features of the compressor and purpose of its individual parts and assemblies

2 Thermodynamic calculation

2.1 Determination of compressor stages number

2.2 Determination of dimensions of the working cylinder

2.3 Determination of stage drive operation, drive motor power

2. 3. 1 Short description of the piston compressor cycle

2. 3. 2 Calculation of piston compressor cycle

2. 3. 3 Calculation of thermodynamic processes

2.4 Calculation of compressor volumetric, isothermal and total efficiency

3 Dynamic calculation

3.1 Determination of speeds, accelerations and forces in crank mechanism

3.2 Determination of crankshaft crankshaft load, torque diagram

4 Compressor lubrication system design and features

5 Strength calculations of individual compressor parts

5.1 Cylinder calculation

5.2 Rod calculation

5.3 Calculation of connecting rod

CONCLUSION

LIST OF SOURCES USED

Introduction

Some types of work are simply impossible without the use of compressed air. A compressor is a device for compressing and supplying air or other gas under pressure and supplying them with various mechanisms and pneumatic tools. Compared to electricity, pneumatic energy is much safer, it allows you to use tools and equipment more economically. Air compressors are widely used in many industries - from oil refining to medicine.

Such compressors are used, for example, in oil and gas drilling units, in engineering enterprises, in petrochemical, gas, metallurgical, electrochemical, mining and other industries.

The disadvantages of piston compressors are the absence of an idle mode and a much smaller range of productivity, a high level of noise and vibration in operation.

The main advantages of piston compressors are: low price, simplicity of construction, maintenance and repair. They can compress almost all technical gases.

One of the most important advantages of a piston compressor is that it can act as a peak load compressor in complex compressor networks. With normal consumption of compressed air, only screw compressors will work in the network, but if for some reason the consumption increases and the screw compressors cease to cope with such a load, the piston compressor will determine this by pressure drop and briefly switch on.

The world compressor market is constantly growing. Faster growth is observed in Europe, Asia and North America. In general, according to statistics, the volume of the local compressor market is directly proportional to the industrialization of the country or region.

2.3 Determination of stage drive operation, drive motor power

2. 3. 1 Short description of the piston compressor cycle

Piston compressors are widely used in the art to compress gases. pV diagram of the actual compressor cycle is shown in Figure. Here, process 1-2 is the polytropic compression of the gas from the pressure of Pinl to the pressure of Pinl. 2-3 is a process of pushing gas into a second stage through an opened exhaust valve. Process 3-4 - reverse expansion of compressed gas during piston movement from upper dead center to lower one. In this case, the outlet valve closes and polytropic expansion of the gas occurs until the pressure in the cylinder reaches the value of moat. Then the suction valve opens and the process 4-1 begins - suction of a new portion of gas. The process is then repeated .

The cycle of the second stage is similar.

4 Compressor lubrication system design and features

Friction units shall be lubricated in piston compressors for normal operation. Lubrication reduces the operation of mechanical friction and wear of parts. The oils cool the surfaces of the parts, protect them from corrosion, improve the tightness of the seals, filling the slots. In piston compressors there are two lubrication systems: 1) cylinders and rod glands; 2) friction units of the movement mechanism.

Lubrication of the cylinders of piston compressors is carried out in one of three ways: by spraying oil poured into the crankcase; injecting the spray oil into the intake gas stream; under pressure from a special oil pump.

Lubrication of cylinders and glands by supply of oil under pressure is used most often in cross-type compressors. Oil is supplied to cylinders of horizontal compressors in the middle of piston stroke in upper point. At cylinder diameters more than 500 mm, supply is performed from above and from below, and at cylinder diameters more than 1000 mm, side supply is additionally performed.

The rubbing surfaces of the movement mechanism are lubricated in two ways: by spraying and supplying lubricant under pressure.

Lubrication of the mechanism of movement under pressure is carried out circulating: oil is taken by the pump (most often gear) from the oil collector and supplied through oil pipelines under pressure of 0.2-0.4 MPa to the places of lubrication, then oil flows from friction units through gaps and flows into the crankcase and oil collector.

Circulating lubrication under pressure makes it possible to constantly clean oil from mechanical impurities.

The pump is driven either from the crankshaft or from an individual motor (for large compressors).

In small and medium compressors, a crankcase serves as an oil collector. For large compressors oil collector is performed independently.

Monitoring of the circulation lubrication system of the movement mechanism involves measuring the oil pressure and sometimes the oil temperature in the oil collector.

Conclusion

In operation, a two-stage air piston compressor with intermediate cooling between the stages and driven by an electric motor with a reduction gear with parameters: cylinder diameters of the first and second stages 0.7 m and 0.42 m, respectively; piston stroke 0.78 m; volumetric capacity of suction air 100.8 m3/min; volumetric efficiency 0.92; isothermal efficiency 0.98; feed coefficient 0.86.

Comparing the designed compressor with the prototype, it should be noted a slightly higher value of volume productivity: 100 m3/min for the prototype and 100.8 m3/min for the designed one.

For this compressor, cycle calculation and thermodynamic processes, kinematic and dynamic analysis of the crank gear mechanism were carried out, operation on the stage drive and power of the drive motor were determined.

According to calculations, p - V and T - S diagrams are built.

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