RU2617035C1 - Single-stage piston compressor of double action - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: compression process is carried out in two stages: at the first stage due to the compressed gas power, at the second stage due to the mechanical drive power. The windows are made in the cylinder in order to communicate the compression cylinder cavities in the outermost positions with the interstage intermediate tank of high pressure, and the drilled holes with gas bypass valves from the harmful space under / over the piston cavity are made.

EFFECT: pressure ratio increase.

3 dwg

Description

The invention relates to a compressor technique, namely to double-acting compressors.

The closest in technical essence (prototype) to the proposed device is a single-stage double-acting reciprocating compressor containing a cylinder with compression cavities located on both sides of the piston, in which channels with locking elements located in them, suction and discharge valves [1] are made. The disadvantage of the prototype is the low degree of pressure increase.

The objective of the invention is to increase the degree of pressure increase. This is achieved by the fact that in the cylinder there are windows for communication of the compression cavities of the cylinder in the extreme positions of the piston with an interstage intermediate high-pressure tank, and in the piston there are drills with valves for transferring gas from the harmful space into the under / above the piston cavity.

The proposed single-stage reciprocating double-acting compressor relates to gas-mechanical devices in which the compression process is carried out in two stages: in the first stage due to the energy of compressed gas, in the second stage due to the energy of a mechanical drive [2].

In FIG. 1 schematically shows the proposed single-stage reciprocating double-acting compressor, FIG. 2 is an indicator diagram of compressor operation.

The compressor comprises a cylinder 1 with compression cavities 2 and 3 located above and below the piston 4, connected by means of windows to a high (final) pressure manifold 6 and an interstage intermediate high pressure reservoir 7.

Consider the operation of the proposed device on the example of processes occurring in the supra-piston cavity 2, which are schematically represented in the indicator diagram (Fig. 2).

When the piston 4 reaches the top dead center (TDC), valve B opens and the harmful space (the space above the piston when the piston is in the TDC) is connected to the under-piston cavity and the pressure in it decreases (process 4-5). Then the piston moves downward and the pressure in the supra-piston cavity decreases and becomes equal to the pressure in the suction line p _sun (process 5-6), the suction valve C opens and the piston cavity is filled with a fresh portion of compressible low-pressure gas (process 6-1). When the piston reaches the bottom dead center (BDC), with a small preliminary, the windows 5 open through which the gas of high (final) pressure p _k is supplied to the cylinder from the collector of high (final) pressure 6 and compresses the gas there (with pressure p _sun ) to a certain intermediate pressure p _ol (process 1-2).

The intermediate pressure is determined by the ratio

,

,

where p _CR - intermediate pressure;

p _{to the} final pressure (discharge pressure);

p _sun - pressure in the suction line;

V _p - the volume of the intermediate cavity;

V _h is the working volume of the cylinder (the volume described by the piston when moving from TDC to BDC);

a is the relative amount of harmful space.

After that, the piston 4 begins to move to the TDC and the process (2-3) of gas compression to a pressure p _k occurs due to the mechanical energy of the drive. When pressure p _{k is reached} , valve A opens and gas enters the interstage intermediate high-pressure tank 7 (process 3-4) and then to the consumer.

The total degree of pressure increase is determined by the ratio

,

,

where π _gas is the degree of pressure increase due to the energy of the compressed gas;

π _fur - the degree of pressure increase due to drive energy.

Thus, the discharge pressure of the proposed compressor will be π _gas times greater than that of the prototype.

In addition, compressor performance can be increased by reducing pressure in the hazardous area.

The stage of gas compression has a beneficial effect on the temperature regime of the air compressor, since the gas will be cooled during throttling.

The advantages of a single-stage double-acting reciprocating compressor include the fact that it can replace any multi-stage compressor.

Define the specific energy consumption spent on gas compression in the compressor in question [2].

. Температуру газа перед сжатием обозначим Т₁, при этом λ=λ₀. С учетом принятых допущений определим массу газа, поступающего в цилиндр в процессе всасывания (в точке 1 по индикаторной диаграмме на фиг. 2)We assume that the gas pressure in the intermediate cavity is equal to the discharge pressure p _n , and its volume is V _ave . The processes of compression (1-2) and expansion (3-4) of the gas proceed with the same rates of polytropes n _p -n _sr = n. The overall degree of pressure increase will be

. The gas temperature before compression is denoted by T ₁ , with λ = λ ₀ . Based on the assumptions made, we determine the mass of gas entering the cylinder during the suction process (at point 1 from the indicator diagram in Fig. 2)

The mass of gas in the cylinder immediately before compression (at point 2) can be determined from the equation of state

Knowing the mass of gas in the intermediate cavity and the cylinder cavity, it is possible to determine the pressure p _CR , the pressure in the intermediate cavity and the cylinder cavity after they are reported

where B is the relative intermediate space.

In view of (3), relation (2) takes the form

Denote the degree of preliminary increase in pressure - π _CR , and the degree of increase in pressure during compression - π ' _to . Then you can write:

Taking into account relations (4), (5), (6), the work spent on gas compression in the compressor can be written as

or

Accordingly, the specific work required to obtain 1 kg of gas supplied to the consumer with a pressure of p _n will be determined by the expression

or

In a dimensionless form, it is written as follows:

могут быть использованы для сравнительной оценки удельных затрат энергии при получении сжатого газа в одноступенчатом поршневом компрессоре двойного действия и многоступенчатом компрессоре. Положив, что V_пр=0 (В=0), а=0 (С=1), уравнение (8) преобразуем к выражению удельного расхода энергии при политропном сжатии газа:The values of l _to and

can be used for a comparative assessment of the specific energy consumption in the production of compressed gas in a single-stage double-acting reciprocating compressor and a multi-stage compressor. Assuming that V _CR = 0 (B = 0), and = 0 (C = 1), we transform equation (8) to the expression of the specific energy consumption during polytropic gas compression:

An analysis of expression (9) reveals the effect of the volume of the intermediate cavity (B) on the specific energy consumption in a single-stage double-acting piston compressor.

The actual specific work spent on compressing a fresh portion of the gas in the cylinder will be less than the work in (8) by the magnitude of the expansion work of the high-pressure gas coming from the interstage intermediate high-pressure tank to the compressor cylinder. This work will be equal to the work required to compress a fresh portion of the gas in the cylinder from pressure p _sun to pressure p _pr

Consider the process of compressing a fresh portion of gas in a gas stage, the circuit diagram of which is shown in FIG. 3 a, b.

At the beginning of the process, the cavity of the interstage intermediate high-pressure vessel p _n is separated (disconnected) from the cylinder cavity with pressure P _{sun by the} piston A with the clamp B (Fig. 3a). Next, the piston is released and under the action of the pressure force of the expanding gas moves in the cylinder until the pressures in the interstage intermediate pressure vessel and the cylinder become equal and become equal to R _pr .

The change in gas temperature in the cylinder will be insignificant; therefore, the compression process can be considered isothermal.

The work performed by the high-pressure gas during expansion will be equal to the work of isothermal compression of the gas in the cylinder, i.e.

Given the notation adopted above, we write

Thus, the actual specific work expended on gas compression in a double-acting single-stage reciprocating compressor will be equal to

The proposed single-stage reciprocating double-acting compressor provides an increase in the degree of pressure increase. The considered approaches have shown their effectiveness and can be used to create a single-stage double-acting reciprocating compressor.

List of sources used

1. Kabakov A.N., Starikov V.I., Shcherba V.E. Double acting piston compressor. Copyright certificate No. 681211. Bull. 1979. No. 31.

2. Dzitoev M.S., Penkov M.M. et al. Gas supply systems and vacuum equipment: a textbook. - SPb .: VKA them. A.F. Mozhaysky, 2010 .-- 530 s.

Claims (1)

A single-stage double-acting piston compressor containing a cylinder with compression cavities located above and below the piston, suction and discharge valves, characterized in that the cylinder has windows for communication of the compression cavities of the cylinder in the extreme positions of the piston with an interstage intermediate pressure tank, and in the piston drilling with valves for bypassing gas from the harmful space into the under / above the piston cavity.

Images