JPH0353032Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a multistage rotary positive displacement compressor (hereinafter simply referred to as a multistage compressor) such as a multistage screw compressor.

(Prior Art) Conventionally, in this type of multi-stage compressor, a combination of either a non-lubricated type or an oil-filled type of multi-stage compressor has been used.

That is, a multi-stage compressor that is a combination of only oil-free compressors is, for example, as shown in FIG.
c, and intercoolers 2a and 2b provided on the discharge side thereof.
(rear cooler 3 in the case of the final stage), and the discharge gas from the previous stage is transferred to intercoolers 2a and 2b.
After being cooled and guided to the suction side of the next stage, and cooled to a predetermined consumption temperature through the rear cooler 3 from the final stage,
It is designed to be sent to a consumption point (not shown).

For example, as shown in FIG. 3, a multi-stage compressor that is a combination of only oil-fed compressors includes oil-fed compressors 4a and 4b having a common drive M, and oil separators 5a and 5b provided on the discharge side thereof. and intercooler 2c
(In the case of the final stage, a rear cooler 3). Then, the discharged gas from the previous stage is separated from the lubricating oil in an oil separator 5a, cooled in an intercooler 2c, and guided to the suction side of the next stage, and the discharged gas from the final stage is passed to an oil separator 5b. After being separated from the lubricating oil and cooled to a predetermined consumption temperature through a rear cooler 3, it is sent to a consumption point (not shown).

Furthermore, the lubricating oil separated by the oil separators 5a and 5b is returned to the immediately preceding oil-supplied compressors 4a and 4b for circulation.

(Problems to be solved by the invention) By the way, both types of compressor main bodies (hereinafter simply referred to as main bodies) have their own advantages and disadvantages.
They are used in fields suited to their respective characteristics.

Among these, the advantage of the oilless cord press is that impurities caused by oiling do not get mixed into the compressed gas. However, on the other hand, in this type of compressor, for example, there is a certain gap between the male and female rotors, so gas backflows from the high-pressure part to the low-pressure part during the gas compression process, which reduces the compression efficiency. It has the disadvantage that it decreases.

On the other hand, the advantage of an oil-filled compressor is that, for example, in a screw compressor, lubricating oil is filled between the teeth and between the teeth and the wall of the rotor chamber during the gas compression process, so the amount of gas leakage is small. It is efficient. Also, by lowering the temperature of the lubricating oil,
By using it as a coolant, it is possible to lower the temperature of the compressed gas and improve compression efficiency.

On the other hand, the disadvantage of this oil-fed compressor is that the lubricating oil is mixed into the gas discharged from the main body, so a separation device such as an oil separator is required to separate this lubricating oil. Additionally, lubricating oil may have the following adverse effects on the gas compression process.

The first is that when the suction pressure of the main body is relatively low, the amount of lubricating oil that evaporates increases, which actually mixes into the compressed suction gas and substantially reduces the suction amount of this suction gas. , leading to a decrease in the performance of the main unit. Further, the amount of evaporation of lubricating oil also increases due to the temperature rise during gas compression, and this also causes the performance of the main body to deteriorate in the same manner as described above.

Second, since the temperature of the suction gas to the main body is usually lower than the lubricating oil temperature, the lubricating oil causes the suction gas to heat and expand before it is sucked into the main body, reducing the amount of suction gas and deteriorating the performance of the main body. do.

Thirdly, in the oil supply type, the lubricating oil and suction gas are compressed in the main body and then discharged, the lubricating oil is separated from the compressed gas in the separator, and the lubricating oil is transferred to the low pressure part of the compressor, that is, the suction port. Alternatively, it can be resupplied to nearby areas for cyclical use. However, the amount of gas dissolved in lubricating oil tends to increase as the pressure and temperature decrease, so when lubricating oil separated under high pressure is supplied to a low pressure section as described above, Boil-off of dissolved gas occurs, reducing the amount of suction gas and reducing the performance of the main body.

Furthermore, in a multi-stage compressor that is a combination of oil-free type only, the number of stages is large, making the system complex and expensive, especially when the pressure ratio is relatively high (pressure ratio 10 or more), and the power consumption at the high stages is also high. This has the problem of poor performance.

On the other hand, in a multi-stage compressor that is a combination of only oil-fed compressors, the number of stages is reduced, but the low-stage oil-fed compressor 4a, oil separator 5a, etc. are very large and expensive, and in some cases However, there is a problem in that the low-stage power performance is worse than that of a combination of only non-lubricated types.

The present invention was developed in view of these problems, and by combining a non-lubricated type compressor and a lubricated type compressor, it is possible to reduce the influence of the deterioration of compression performance due to the disadvantages of both, and to take advantage of the advantages of both. The purpose is to provide a multi-stage compressor with the following functions.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the multi-stage compressor according to the present invention is provided with an oil-free compressor on the lower stage side and an oil-filled compressor on the higher stage side. It is.

(Example) Next, an example of the present invention will be described based on FIG.

FIG. 1 shows a two-stage screw compressor, including a first-stage oil-free screw compressor 1 and a second-stage oil-filled screw compressor 4 having a common drive machine M, and a first-stage discharge side. It consists of an intercooler 2 provided on the second stage, an oil separator 5 and a back cooler 3 provided on the discharge side of the second stage. Then, the oil-free discharge gas from the first stage is cooled by an intercooler 2 and guided to the suction side of the second stage, and the discharge gas from the second stage is separated from lubricating oil by an oil separator 5. After being cooled to a predetermined consumption temperature through the rear cooler 3, it is sent to a consumption location (not shown). Furthermore, the lubricating oil separated by the oil separator 5 is returned to the second stage oil supply type screw compressor 4 so that it can be used for circulation.

In this way, by employing the oilless compressor 1 in the first stage, performance degradation in the compression process caused by lubricating oil is eliminated. In addition, since the pressure difference in the first stage is small, there is little performance deterioration due to gas leakage from the gap between tooth profiles, which is a disadvantage of non-lubricated types.Furthermore, since the suction gas temperature in the first stage is usually low, the discharge gas temperature The rise in the temperature is small, which is a favorable condition for the second stage.

In addition, by employing the oil-fed compressor 4 in the second stage, the suction pressure and temperature in the lubricant-fed compressor 4 are higher than those in the first stage, and the negative effects of lubricating oil are reduced. High performance is maintained due to the sealing effect of lubricating oil against large pressure differences. Furthermore, although the second stage is supplied with higher temperature suction gas than the first stage, the cooling effect of the lubricating oil makes it possible to suppress the rise in gas temperature during the compression process, making the best use of the advantages of the oil supply type.

In addition, in the above embodiment, a common drive machine M was used for the first and second stage screw compressors, but the invention is not limited to this, and various methods as shown in FIGS. 4 to 7 may be used. may also be used. In other words, the one shown in Fig. 4 uses an independent drive machine for each compressor 1, 4, and the one shown in Fig. 5 uses an independent drive machine for each compressor 1, 4, and Fig. 5 shows one in which the low-pressure side of the first stage and the high-pressure side of the second stage are connected. Fig. 6 shows a double-shaft drive machine M that drives the high pressure side of each of the first and second stages, and Fig. 7 shows a common drive machine M. The high-pressure side of the first stage and the second stage are driven by a drive machine M via a three-axis gear 6.

(Effects of the invention) As is clear from the above explanation, according to the invention, by making the lower stage side of the multistage compressor non-lubricated, performance can be improved in the lower stage, and large oil A separator is no longer required, making the device more compact. Also,
By making the high stage side oil-supplied, high performance can be achieved at the high stage, the number of stages can be reduced, and the device can be simplified. This has the effect of comprehensively improving power performance and reducing equipment costs.

[Brief explanation of the drawing]

FIG. 1 shows a system diagram of a multi-stage screw compressor according to the present invention, FIGS. 2 and 3 show system diagrams of a conventional multi-stage screw compressor, and FIGS.
The figure is a diagram showing an example of a combination of a compressor and a drive machine. 1...Oil-free screw compressor, 4...Oil-filled screw compressor.

Claims (1)

[Scope of utility model registration request] A multi-stage rotary positive displacement compressor, characterized in that an oil-free rotary positive displacement compressor is provided on the low stage side and an oil-filled rotary positive displacement compressor is provided on the high stage side.