JPH0434000B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a device for increasing the efficiency of a centrifugal gas compressor, and more particularly, to a device for increasing the efficiency of a centrifugal gas compressor, and more particularly, for direct injection of vaporizable liquids, such as water, into the gas stream of a centrifugal multi-stage compressor. injection)
Regarding assembly for.

BACKGROUND ART Centrifugal gas compressors have been used for many years in a wide variety of applications such as jet engines and heat pumps. Conventionally, in centrifugal gas compressors, it has been particularly advantageous to perform wet compression as opposed to dry compression, i.e. to carry out compression while injecting an evaporable liquid into the gas stream of the compressor and evaporating the liquid. It is known. This is because the evaporation of the liquid injected into the compressor lowers the inlet temperature of the compression stage "upstream" of the liquid injection point, reducing the compression ratio or This is because the ratio of outflow gas pressure to inflow gas pressure becomes considerably high. Direct water injection also effectively reduces the operating temperature of the compressor, thus eliminating the need for expensive external intercoolers.

Although the benefits of injecting vaporizable liquid directly into the gas stream of a centrifugal compressor are widely recognized, there are no known devices and techniques known to those skilled in the art for performing wet compression. The ones that do have some obvious drawbacks. An example of such prior art is described in US Pat. No. 2,786,626.
In this patent, a vaporizable liquid is injected into the compressor inlet and a crossover channel between each of the first few compression stages decelerates the high-velocity gas stream leaving the impeller to bring it to pressure. This is a flow path that communicates between the diff user for conversion and the return flow path that guides the gas flow inward from the outer periphery toward the center of the next stage impeller. A method of compressing gas in a compressor is disclosed. The liquid injected into the communication flow path is injected from a liquid injection port directed upstream of the gas flow of the compressor. Further, only one liquid injection port is provided per stage.

In the compressor described in the above patent, the degree of evaporation of the liquid injected into the compressor gas stream is quite limited. This is because the liquid is injected into the low speed region of the compressor and therefore no atomization or atomization of the liquid is achieved. This is especially true for liquids injected into the compressor inlet. Very small droplets are required to achieve a high degree of evaporation. This is because the surface area of such droplets is large relative to the volume of the droplet, and therefore the droplet can quickly absorb heat and evaporate. As a result of the limited evaporation of the injected liquid in the compressor disclosed in said patent, the reduction in power supplied to the compressor is also limited. Limited evaporation also results in large droplets impinging on compressor internal components such as the impeller, thus resulting in significant erosion and pitting of such components after a relatively short period of operation. There is a risk that this may occur.

The system described in said patent provides a method for injecting liquid into a gas stream at a high velocity when it is desired to inject the liquid from the injection orifice into the compressor gas stream over a distance necessary to achieve appreciable atomization. complex equipment is required. Such high speed is required by
This is because the liquid injection ports described in the patent are oriented in a direction opposite to the flow direction of the gas flow.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to address the problems in the prior art mentioned above, namely the insufficient atomization of the vaporizable liquid injected into the gas stream of the compressor, The object of the present invention is to solve problems such as limited reduction in the power supplied and the risk of erosion and pitting occurring in internal parts of the compressor.

(Structure of the Invention) In order to achieve the above object, the present invention includes a housing, a rotating shaft pivotally supported within the housing, and a plurality of reciprocating shafts disposed along the longitudinal axis of the rotating shaft. In a compressor including a compression stage, at least one stage of the compression stage includes an impeller having a large number of blades that rotates with a rotating shaft, a diff user that receives a gas flow from the impeller, and a diff user that receives the gas flow from the diff user. a communicating channel for receiving and a liquid injection means for injecting an evaporable liquid into the gas stream, the liquid injecting means being arranged to inject the liquid into the diffuser substantially upstream of the communicating channel; . The liquid injection means has a plurality of liquid injection ports, and each injection port is oriented such that the angle between the liquid injection direction and the gas flow is 80 degrees to 100 degrees, and the angle between the liquid injection direction and the gas flow is 80 degrees to 100 degrees. It is arranged at a radius within the range of 1.05 to 1.1 times the maximum radius of the impeller.

(Operations and Effects of the Invention) With the above configuration, the liquid injected from the injection port at a substantially right angle to the gas flow is sheared by the relatively high-speed gas flow exiting the impeller and is subdivided into fine droplets.
In other words, it is atomized. Since the atomized liquid passes through the return flow path from the differential user via the communication flow path, it is transported into the high-temperature gas flow longer in time and distance than conventional methods before reaching the next stage impeller. The liquid remains for a long time so that the liquid can completely evaporate. As a result of complete evaporation of the injected liquid, the gas stream is effectively cooled, reducing the power required to compress it to the target pressure and discharging it as droplets to the next stage of vanes, etc. Since there is no collision, erosion and pitting of the blades etc. due to the injected liquid is prevented. Furthermore, the present invention does not require complex equipment for injecting liquid into a gas stream at high velocity as in the prior art.

(Description of preferred embodiment) The invention will now be described in detail with reference to the accompanying drawings.

In FIG. 1, a conventional centrifugal four-stage compressor is shown generally at 10. However, the present invention can also be effectively used in compressors having more or fewer stages. Compressor 10 is illustrated in a simplified manner, with stationary parts (eg, the compressor housing) being shaded in one direction and rotating parts being shaded in the other direction. Gas to be compressed is at inlet 1
1 enters the compressor 10 , passes through a passage 12 , and then enters a first multi-bladed impeller 14 attached to a rotating shaft 15 . As is well known, the impeller 14
Due to the high rotational speed of the impeller 14, the gas from the impeller 14 is centrifugally introduced into the diffuser 17. The diff user is preferably wingless, as will be explained in more detail below. The gas stream being compressed passes through connecting channel 18 and further through return channel 19.
pass through. This return flow path is usually provided with a direction control vane as shown by the reference numeral 20, and the four-stage compressor 10
The gas flow is directed to another impeller 21 forming the second stage of the gas flow. Similarly, further impellers 22 and 23 are provided to constitute the third and fourth stages of the compressor 10, respectively. The second and third stages of compressor 10 are configured similarly to the first stage. Therefore, by explaining any one of the first to third stages, all of these stages will be understood. Therefore, only the first compression stage including the impeller 14 will be described. According to the invention, a plurality of liquid injection ports 24 are provided. Preferably, these liquid injection ports 24 are water injection ports, and are connected to a liquid supply source via a supply pipe 25. Each supply pipe 25 is, for example, a distribution pipe 2
7, and this distribution pipe is connected to liquid delivery means (not shown). Further, the liquid injection port 24 is arranged to inject the liquid into the diffuser 17 substantially upstream of the communication channel 18 . As used herein, "substantially upstream" means a position closer to the impeller within the differential user, and specifically, the injection port is located at a radius within the range of 1.05 to 1.1 times the maximum radius of the impeller. means to place it in

The importance of injecting liquid into the diffuser 17 substantially upstream of the connecting channel 18 is secondary.
It can be better understood by considering the figure. FIG. 2 is a detailed view of the upper part of the first stage of the multi-stage compressor 10 shown in FIG. As is well known to those skilled in the art, "diffusers" are constructed with the ability to convert dynamic or kinetic energy into static pressure. The broken line 28 represents the maximum radius of the differential user 17 and the connection channel 18 between the differential user 17 and the connecting channel 18.
indicates the boundary between The differential user 17 is a radial differential user. That is, the useful space within the differential user 17 increases with increasing radial distance from the axis of the rotating shaft 15. As shown by arrow 29, the gas flow being compressed in compressor 10 is directed from left to right to impeller 14's vanes 14'.
, and further connects to the differential user 17 and the communication channel 1.
8, the direction limiting vane 2 of the return flow path 19
Pass through 0. Since the diff user 17 is a radial diff user and the impeller 14 discharges the gas flow 29 into the diff user 17 at a high rotational speed, the gas flow 29 (not clearly shown in FIG. 2) actually Inside the differential user 17 and the return flow path 1
9 follows a spiral path. gas flow 2
9 reaches maximum speed when leaving the impeller 14;
Then, due to conservation of angular momentum, the differential user 1
7 and rapidly decelerates while traveling in the radial direction. Significant advantages are obtained by locating the liquid injection ports 24 in the diff user substantially upstream of the communicating channel 18, i.e. close to the impeller, in an area where the gas flow 29 is relatively high velocity. .

For example, the gas flow 29 may be
The liquid stream injected into it is strongly atomized or atomized into fine droplets. As mentioned earlier, the smaller the droplet, the more easily it absorbs heat and evaporates. In fact, the evaporation rate is approximately directly proportional to the droplet size (ie, the inverse of the droplet diameter). The droplet size is related to the relative velocity between the droplet and the gas stream 29. That is, the size of the droplet follows the square of this relative velocity. This relative speed is
Since the velocity of the injected liquid is relatively low, it depends primarily on the velocity of the gas stream 29 and
The velocity decreases as the radial spacing of the liquid jets 24 (i.e., the radial distance from the axis) increases, so the droplet size and therefore its evaporation rate are dependent on the radial spacing of the liquid jets 24. The relationship can be graphed as shown in FIG.

The present invention not only increases the evaporation rate, but also significantly increases the duration of evaporation, thus further ensuring complete evaporation. The increase in the duration of evaporation is due to the long spiral path that the droplets in the gas stream 29 (FIG. 2) have to travel from the point of injection at the nozzle 24 to the next stage of the compressor 10. . Thus, by reducing the radial spacing of liquid jets 24 in accordance with the present invention, two factors work together to significantly improve overall evaporation. Specifically, (1) the evaporation rate of the droplets is significantly increased by atomizing the injected liquid into fine droplets (see Figure 3), and (2) the gas flow 29 (Figure 2). The duration of the droplet in the
The goal is to make it quite long.

The significantly improved evaporation achieved by the present invention has a significant effect on the performance and durability of compressor 10. This significantly facilitates a reduction in the power supplied to the compressor 10 while maintaining the temperature of the gas stream 29 at a desirable low temperature. Furthermore, the risk of pitting and erosion due to the impact of high-velocity unevaporated droplets on internal components of the compressor 10, such as the impellers 21, 22, 23, is virtually eliminated.

Another benefit of radially spacing the liquid jets 24 into the diffuser 17 substantially upstream of the flow path 18 is that the momentum associated with the cooling or temperature reducing effect of rapidly moving droplets is The pressure gain of the compression stage increases due to the change in . This temperature reduction effect increases with increasing liquid evaporation rate and velocity, both of which increase as the liquid jet 2 increases.
4 by shortening the radial spacing. It is believed that the resulting increased pressure gain is at least 2% or 3% of the pressure gain of the compression stage in the absence of temperature reduction effects.

The inventor believes that the radial spacing between the plurality of liquid injection ports 24 should be 1.05 to 1.1 times the maximum radius of the impeller 14;
It has been found that the gas flow coming out of 4 becomes unstable and the efficiency decreases when it is made larger than 1.1 times.

Referring again to FIG. 2, this figure illustrates another feature of the invention. The liquid injection port 24 has a gas flow 2
9 is oriented vertically. This allows the liquid supplied to the nozzle 24 to be injected into the gas stream 29 at a low velocity, for example 50 feet per second (15.3 m/sec). This is because the injected liquid is directed across the gas stream 29. The injected liquid can therefore easily penetrate into the gas stream 29 and be optimally atomized. but,
The injected liquid must be prevented from colliding with the right side wall of the diffuser 17. Otherwise, the atomization of the liquid will be poor. If the liquid jet orifice 24 is oriented perpendicular to the gas flow 29, the flow of liquid injected through the jet orifice 24 may be at a low velocity, so that a liquid delivery means (not shown) for liquid jetting is required.
The structure of can be simplified. This advantage is that the injection port 24
This can be achieved if the direction of liquid injection from the gas flow 29 is within the range of 80 degrees to 100 degrees.

FIG. 4 shows yet another feature of the invention. Fourth
The figure is a view taken along line 4--4 in FIG. 1, partially broken away to show the supply pipe 32 and liquid injection port 30, and with the vanes of the return channel 26 omitted for simplicity. be. The above-described further features of the invention shown in FIG.
(corresponding to No. 4) regarding the number and position of the plurality of liquid jet ports 30. The injection port 30 is connected to the supply pipe 32 and the distribution pipe 3
1 to a liquid supply means (not shown). The preferred number of injection ports 30 is 6 to 1.
In the preferred embodiment of the present invention, eight are used. The injection ports 30 are preferably disposed axially symmetrically about the longitudinal axis of the shaft 15. Multiple injection ports 3
The aforementioned number and location of zeros allows a full range of gas flows to be utilized in the compressor 10 for vaporizing droplets.

The number of liquid jets may be greater or lesser than the preferred number described above. The upper limit of the number of liquid injection ports is determined by the diameter of the inner hole of the injection port, which is made smaller according to the number. This is because if the diameter of the bores is made too small, they will be more likely to become clogged by contaminants in the liquid that is injected through them. Using fewer than the minimum preferred number (i.e., 6) will not allow the full range of gas flow to be utilized within the compressor 10 for droplet evaporation, but will still benefit from the present invention. is obtained.

In the most preferred embodiment of the invention, compressor 10 is an industrial process heat pump, the vaporizable liquid injected into the gas stream within the compressor is water, and the preferred embodiment of liquid injection ports 24 is The radial spacing is in the range of about 1.05 to 1.1 times the maximum radius of impeller 14, with the upper end of this range being particularly preferred.
This range applies to compressors with pressure ratios in the range of about 1.4 to 1.6 per stage and impeller tip speeds of about 900 to 1100 feet per second (274.5 to 335.5 m/s). This is for compressors in the range of . However, the advantageous effects of the present invention are that when the compression stage is operating at a tip speed significantly higher than the impeller tip speed described above, the liquid injection orifice 24
can also be obtained with a radial spacing of

Such heat pumps have a relatively high coefficient of performance. This is not only due to the good evaporation of the water injected into the heat pump, but also due to the increased mass flow rate of water vapor at the heat pump output.

Although some preferred features of the invention have been illustrated above, it is understood that many variations and modifications are possible within the scope of the invention. For example, the centrifugal compressor 10 may be combined with an axial flow compressor.

[Brief explanation of drawings]

FIG. 1 is a simplified cross-sectional view of a portion of an ordinary centrifugal multi-stage compressor incorporating the present invention, FIG. 2 is a cross-sectional view of a portion of the first stage of the multi-stage compressor shown in FIG. 1, and FIG.
The figure is a graph showing the evaporation rate of droplets with respect to the radial spacing of the liquid injection ports of the compressor shown in Figure 1, and the graph shown in Figure 4.
The figure is a cross-sectional view taken along line 4--4 of FIG. 1 showing details of the third stage of the compressor of FIG. 1, with the upper part thereof partially cut away. 10... Centrifugal compressor, 14, 21, 22, 23...
Impeller, 15...shaft, 17... differential user, 18...
Communication channel, 24, 30...Liquid injection port, 25, 32
...Liquid supply pipe.

Claims (1)

What is claimed is: 1 a housing, a rotating shaft pivotally supported within the housing, and a plurality of successive compression stages disposed along the longitudinal axis of the rotating shaft; at least one of the compression stages; an impeller 14 whose stages are rotatable with said rotational shaft, a diff user adapted to receive a gas flow from said impeller, and a connecting channel 18 directing said gas flow from said diff user to a return channel 19; liquid injection means stationary with respect to the impeller, the vaporizable liquid being subdivided into fine droplets by the gas flow from the impeller and evaporated within the diffuser; a liquid injection means 24 for injecting liquid directly into the gas flow in the diffuser upstream of the communication channel and close to the impeller, and at a high relative velocity to the gas flow; 25, 27, the liquid injection means has a plurality of liquid injection ports 24, and each liquid injection port has an angle of 80 between the liquid injection direction and the gas flow in the diff user.
and a maximum radius of the impeller with respect to the axis.
A compressor characterized in that it is arranged at a radius within a range of 1.05 to 1.1 times. 2. Claim 1, wherein the plurality of liquid injection ports are arranged approximately axially symmetrically about the axis.
Compressor as described in section. 3. Claim 1 or 2, wherein the plurality of liquid injection ports are comprised of 6 to 12 liquid injection ports.
Compressor as described in section. 4 the liquid injection ports are spaced relative to the axis such that the liquid injected through them into the gas stream has substantially completely evaporated before reaching the impeller of the next compression stage; , a compressor according to claim 1. 5. The compressor according to claim 2, wherein the plurality of liquid injection ports includes eight liquid injection ports. 6. The compressor according to claim 5, wherein each of the liquid injection ports is arranged at a radius 1.1 times the maximum radius of the impeller with respect to the axis. 7. The compressor according to claim 1, wherein the liquid injection port is configured to allow water to pass through.