JPS5930240Y2 - centrifugal refrigerator - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a centrifugal refrigerator that uses a centrifugal multi-stage compressor and employs an economizer cycle.

It is generally known that an economizer cycle is used in refrigerators using centrifugal multi-stage compressors to increase cycle efficiency.

In other words, an economizer cycle is a system used in a multi-stage compression refrigeration cycle, and is used to increase the cycle efficiency of the entire compressor by allowing economizer gas to flow into the flow path after the first stage impeller outlet. Conventionally, gas is introduced into this intermediate stage by introducing it immediately before the impeller in the latter stage, near the exit of the return guide vane, or before the inlet of the return guide vane.

Among these, in the case where gas from an economizer or the like is guided to just before the impeller or near the exit of the return guide vane, the flow path from the confluence point to the impeller population 1 downstream is short.

On the other hand, the economizer gas flow rate is as much as 10 to 15 times the mainstream gas, so if the flow path is short, mixing with the mainstream gas will be incomplete, and the gas will be sucked into the impeller with uneven temperature and velocity. This reduces the efficiency of the impeller.

On the other hand, in the case where the economizer gas is introduced before the return guide vane inlet, it is difficult to determine the direction of the flow path.

In other words, the direction of the mainstream gas upstream from the guide vane has an angle (hereinafter referred to as the flow angle) with respect to the plane containing the rotation axis, resulting in a screw-like flow, but this flow angle depends on the operation of the compressor. Since it changes depending on the state, if the direction of the economizer gas flow path is fixed, the economizer gas does not always smoothly merge into the mainstream.

In general, compressors are operated infrequently at the design point, so for example, if the direction of the economizer gas flow is determined according to the direction of the mainstream gas at the design point, if the compressor is operated at a point other than the design point, Since the direction changes, it does not match the main flow direction, and the merging cannot be performed smoothly, which increases mixing loss, which not only reduces compression efficiency but also causes problems.

The inventors conducted repeated research to improve the shortcomings of the conventional system, and confirmed that the shortcomings of the conventional system were due to the causes mentioned above.In order to improve the efficiency drop, when the two gases merged, (i ) When merging, align the direction of the mainstream with the direction of economizer gas.

(11) Immediately after merging, the mixture will not be very good, so the next stage impeller population should be 1 to keep a sufficient distance.

Ideally, (iii) both vehicles should have the same speed just before merging.

I came up with this idea and came up with this idea.

The present invention is an attempt to accurately eliminate the above-mentioned conventional drawbacks, and is to install an economizer on the back side of the return guide vane and immediately after the return guide vane inlet along the flow direction of the mainstream gas. By providing a gas inlet, the economizer gas is mixed in an area where the direction of the mainstream gas is almost constant regardless of the operating state, and at a location that is a sufficient distance from the impeller inlet of the next stage. It is an object of the present invention to provide a centrifugal refrigerator which has a small mixing loss, can easily and smoothly equalize the speed, and can improve the efficiency of the compressor regardless of changes in operating conditions.

The present invention comprises a centrifugal multi-stage compressor, a condenser, an evaporator, and an economizer to form a refrigeration system, and the economizer gas led from the economizer is transferred to the first stage of the multi-stage compressor.
In a centrifugal refrigerator in which the economizer gas is mixed into the mainstream gas through an economizer gas inlet provided on the wall of the mainstream gas flow path after the outlet of the stage impeller, the inlet is located on the back side of the return guide vane. This centrifugal refrigerator is characterized in that the centrifugal refrigerator is provided in the vicinity and immediately after the return guide vane inlet, oriented in a predetermined direction along the flow direction of mainstream gas.

An embodiment of the present invention will be described with reference to a two-stage compression centrifugal refrigerator shown in FIGS. 1 to 4.

This centrifugal compressor performs two-stage compression, so
A front stage impeller 2 and a rear stage impeller 5 provided on the rotating shaft 1 are provided in the compressor main body 3, and the flow from the outlet of the front stage impeller 2 is transferred to the rear stage impeller 50 inlet by the middle body 3.3□. A gas passage 8 for suction 1 is formed between the front stage impeller 2 and the rear stage impeller 5, and a return guide bay 77 is provided in the middle of this gas passage 8.

This centrifugal compressor, condenser 12, economizer 11, and evaporator 13 form a refrigeration cycle.

A gas inlet 9 is provided at an intermediate stage of the centrifugal compressor to introduce gas from an economizer 11 or a medium-high temperature evaporator (not shown). Economizer 11 has been contacted.

However, the lever gas inlet 9 is provided on the back side (convex surface) of the return guide vane 7 at a position immediately after the return guide vane inlet and is oriented in a predetermined direction along the flow direction of the mainstream gas. .

In addition, in order to smoothly guide the economizer gas to the gas inlet 9, as shown by the two-dot chain line in FIG. 1, a wall surface partially or entirely formed of a conical surface 33 is added to improve the flow rectification effect. It is also possible.

The gas inlet 9 is at least downstream of the input lower □ of the return guide vane 7 and immediately after approaching the guide vane lower □, with the guide vane root edge T2 as the gas inlet edge, and the economizer facing the mainstream. This is to allow the gas to smoothly merge into the main stream and mix.

That is, the flow of the mainstream gas introduced into the return guide vane 7 to recover the swirling energy from the front stage impeller 2 is rectified at the inlet of the return guide vane 77, and after this inlet, the direction of the flow of the mainstream gas is , remains almost constant regardless of changes in the operating state of the compressor, so if the direction of the economizer gas inlet 9 is set at a predetermined angle in accordance with the direction of this mainstream gas, regardless of changes in the operating state of the compressor. Smooth merging can be achieved.

Moreover, since the inlet 1 of the rear impeller 5 can be sufficiently far away, a uniform gas obtained by sufficiently mixing two flows with different quantities, temperatures, and speeds can be sucked in and the suction conditions is improved, and efficiency is improved.

In particular, in order to smoothly merge the economizer gas into the main stream, the direction of the economizer gas passage is not only inclined in the radial direction as shown in FIG. 1, but also in the circumferential direction as shown in FIG.

If the exit of the economizer passage is located near the back side (convex surface) of the return guide valve as shown in FIG. 2, the merging will occur near the center of the mainstream gas flow path, and the velocity will be evened out even more smoothly.

Although the economizer flow path 10 is connected to the economizer 11 through a pipe 10 by utilizing a vacant space in the compressor main body 3, it is also possible to connect the gas inlet 9 directly to the pipe 10. .

Furthermore, since the economizer gas flows only due to the pressure difference, the economizer gas velocity before the economizer gas inlet 9 is considerably smaller than the mainstream gas velocity.

Therefore, the opening area of the gas inlet 9 is gradually narrowed down to increase the speed, and the opening area is used to match the velocity with the mainstream gas velocity, so that the economizer gas always joins smoothly and the mixing loss is minimized. .

In the figure, 4 is a slinger, 6 is a liner ring, 14 is a driver, 15, 16 are expansion valves, 17, 18, 1920 are cycle system piping, and 21 is a variable vane.

According to the present invention, it is possible to provide a centrifugal refrigerator that has the following particularly remarkable effects.

(1) Regardless of changes in compressor operating conditions, the inflow direction of the economizer gas can always be aligned with the direction of the mainstream gas, allowing for smooth merging, no generation of vortices, and low mixing loss. .

(2) Since the merging takes place almost near the center of the mainstream gas flow path, the velocity can be equalized smoothly and in a short time. (3) The distance from the merging point to the next stage impeller population 1 is Since sufficient amount of gas can be obtained, the two flows having different properties are mixed well, resulting in a uniform gas, and the suction conditions for the impeller of the next stage are favorable.

(4) As a result of the above, the efficiency of the compressor can be improved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a longitudinal sectional view and FIG.
The figures are a sectional view taken along the line AA in FIG. 1, FIG. 3 is a sectional view taken along the line BB in FIG. 1, and FIG. 4 is an explanatory diagram of the system in use. 1...Rotating shaft, 2...Pre-stage impeller, 3
...Compressor main body, 3□, 32...Middle body, 33...Conical surface, 4...Slinger, 5...Late stage Impeller, 6... Liner ring, 7... Return guide vane, 7...
... Guide vane inlet, 72 ... Guide vane root edge, 8 ... Gas flow path, 9 ...
Gas inlet, 10...Economizer flow path, 10
□・・・Piping, 11・・・Economizer,
12... Condenser, 13... Evaporator, 1
4... Drive machine, 15, 16... Expansion valve, 17° 18. 19, 20... Cycle system piping, 21... Variable vane.

Claims (1)

[Claims for Utility Model Registration] 1. A refrigeration system is formed by comprising a centrifugal multi-stage compressor, a condenser, an evaporator, and an economizer, and the economizer gas led from the economizer is transferred to the first stage of the multi-stage compressor. In a centrifugal refrigerator in which the economizer gas is mixed into the mainstream gas through an economizer gas inlet provided on the flow path wall of the mainstream gas flow path after the impeller outlet, the inlet is located near the back side of the return guide vane. What is claimed is: 1. A centrifugal refrigerating machine, characterized in that the refrigerating machine is provided at a position immediately after the return guide vane inlet and oriented in a predetermined direction along the flow direction of mainstream gas. 2. The centrifugal refrigerator according to claim 1, wherein the gas inlet has an opening area that matches the mainstream gas velocity of the compressor.