KR20040098787A - Micro Turbo Compressor - Google Patents

Abstract

PURPOSE: A micro turbo compressor is provided to supply pure compressed air, which does not contain oil while the micro turbo compressor is being moved. CONSTITUTION: A micro turbo compressor includes a front compression section(21), a rear compression section(22), and a power source. An axial flow compressor having a variable-type fixing wing is installed at the front compression section(21) and a centrifugal compressor is installed at the rear compression section(22) in order to vary a direction of air flowing into the rear compression section. The axial flow compressor having the variable-type fixing is installed at the front compression section(21) and a mixed flow compressor is installed at the rear compression section(22) in order to vary the direction of air flowing into the rear compression section.

Description

Mini Turbo Compressor

Air compressor is a device for supplying air of high pressure (relative pressure of about 3-10 bar) used for various purposes in various industrial sites. Currently, air compressors mainly used are reciprocating / scrolling / screw type and turbo type using centrifugal compressors. As can be seen in Figure 4 of the various compressors reciprocating and scroll type is mainly used for small capacity of less than 10 horsepower and conventional screw type is mainly used for small and medium compressors of less than 300 horsepower. The turbo type centrifugal compressor is mainly used for large compressors of 500 hp or more, which requires very high rotational speed to realize low capacity due to the design characteristics of the centrifugal compressor, and has a small capacity compared to other compressors. In compressors, it is difficult to achieve high efficiency due to the problem of too small size.

The place that needs compressed air varies widely from hospital to general factory, and it can be said that compressed air is used in all around us. In the case of the screw compressor, which is widely used, the operating area is narrow, and its structure Compressed air and oil are mixed together, the disadvantage is that it is very difficult to remove the mixed oil completely. Therefore, some oils are allowed to flow in, and if the oil is completely removed, the price will be more than 30-50%. On the other hand, in the case of the turbo type, a wide operating area can be obtained, and thus, there is an advantage of saving power by appropriately adjusting the flow rate according to the required compressed air demand, and having the advantages of high efficiency and excellent durability / maintenance. . However, even in the turbo type, the oil problem is less serious than the screw type, but the manufacturing cost increases as a very sophisticated sealing technique is required to completely remove the oil. In the case of the turbo type, the large-capacity compressor of 500 hp or more has great advantages in consideration of the flow rate and efficiency, but the centrifugal compressor used for the turbo compressor is small at the low capacity of 300 hp or less. It is difficult to expect high efficiency and competitiveness compared to the screw type because it becomes difficult to design and manufacture because the efficiency is lowered and high rotational speed is required. However, due to the recent environmental problems and increasing demand for compact and lightweight compressors and clean compressed air free of oil and moisture, many efforts have been made to develop compact turbo compressors that can replace screw compressors.

The method mainly used in the existing small two-stage turbo compressor is to use a two-stage centrifugal compressor (51, 53) by rotating the high speed gear 54 and the general motor (55) as shown in FIG. The water-cooled intermediate cooler 52 is installed between the stages. There are two main roles of the intermediate cooler 52. One is to reduce the work of air compression for the same compression ratio by lowering the temperature of the air flowing into the compressor 53 connected to the rear of the intermediate cooler 52. The second effect is to maintain the specific speed of the compressor 53 at an appropriate level so that the compressor 53 can be designed with high efficiency. Table 1 shows the air required to supply compressed air at the same flow rate for the case of the intermediate cooler 52 with and without the 170 hp (including shaft loss) grade two-stage turbo compressor developed by IHI of Japan. Comparing the aerodynamic power (Aerodynamic Power), it can be seen that the required power is increased by 26.8% without using the intermediate cooler (52).

On the other hand, there are several problems caused by using the intermediate cooler 52. First, the intermediate cooler 52 increases the density of the air flowing into the rear stage compressor 53, which causes the compressors 51 and 53 to increase. The design requires a small flow area. This reduces the efficiency of the compressor by increasing the ratio of the end interval to the exit height of the impeller blades of the rear stage compressor 53. Therefore, as the present invention suggests, a turbo compressor design of 300 hp or less requiring a compact compressor is an obstacle. do. In addition, in the case of the intermediate cooler 52, the size of the intermediate cooler 52 is very large compared to the compressors 51 and 53, and a separate cooling water supply line has to be installed, which makes it difficult to move the turbo compressor and installs the intermediate cooler 52. Water generated by condensation during the inflow into the rear compression stage 53 degrades the performance of the compressor 53 and requires periodic maintenance due to wear of impeller material and formation of water scale inside the intermediate cooler. It may cause. In addition, a separate device 56 for treating condensate generated in the intermediate cooler 52 is required, and additional accessories such as a cooling tower and a cooling pump for supplying the cooling water are required to complicate the system configuration and increase manufacturing and operating costs. There is a disadvantage.

In order to achieve the same efficiency as the conventional turbocompressor without using the intermediate cooler 52, the efficiency of the centrifugal compressors 51 and 53 that compresses air and consumes actual power should be very good. However, since most centrifugal compressors have maximum efficiency at similar specific speeds, if the same centrifugal compressors are used in multiple stages and do not have intermediate cooling, the specific speed of the centrifugal compressors decreases toward the rear stage and thus the maximum efficiency is low. And eventually consume more power.

The present invention has a first technical problem to configure a portable small high-efficiency turbocompressor capable of supplying pure compressed air that is not mixed with oil while being difficult to implement with a conventional compressor. In order to solve this problem, the present invention uses an axial compressor 18 that requires a high specific speed (about 200 to 400) in the front compression stages 21 and 31 as shown in FIG. In (22, 32), a turbocompressor using a centrifugal compressor 19 having a maximum efficiency at a lower specific speed (about 60 to 100) is designed.

In this case, since the number of rotations must be increased in order to operate the front end axial compressor 18 at a high specific speed, it is possible to obtain the maximum efficiency of the specific speed of the rear end centrifugal compressor 19 without using the intermediate cooler 52. There is an advantage to increase the area.

However, in the existing turbocompressor using the same centrifugal compressor in both the front ends 21 and 31 and the rear ends 22 and 32 in order to increase the specific speed of the rear ends 22 and 32 without using the intermediate cooler 52. When the rotation speed is increased, the specific speed of the front ends 21 and 31 becomes too large, which causes a problem that the efficiency of the front ends 21 and 31 decreases.

For reference, the specific speed is the best way to describe the shape of the compressor and is a dimensionless number defined by Equation 1 below.

As can be seen in Fig. 6, in general, the centrifugal compressor has a specific speed of 60-100, a quadrifugal compressor (see Fig. 10) has a specific speed of 100-200, and an axial compressor has a specific speed of 200-400. Has the highest efficiency at. 7 shows a change in the shape of the compressor according to the specific speed. As the specific speed increases, the shape of the compressor changes from the centrifugal type to the axial flow type. For reference, in FIG. 7, the unit of the flow rate was used as the unit of the flow rate in the United States using GPM (Gallon Per Minute), so the value of the specific velocity multiplied by 51.65 in FIG. 6 is represented by the specific velocity value in FIG. 7.

Table 2 calculates the performance of the turbocompressor of the method proposed by the present invention and compares it with a 170 hp turbocompressor sold in Japan.

In order to obtain the performance of the turbo compressor shown in Table 2, there is a difficulty in increasing the compression ratio and efficiency per unit of the front axial compressor 18 and the rear centrifugal compressor 19. Currently, the compression ratio per unit of general axial compressors is 1.2-1.4, the efficiency is about 88%, and in the case of centrifugal compressors, the compression ratio is 2-5 and efficiency is 70-80%. Since the absolute pressure is around 8-9 bar, the compression ratio of the front compression stage (21, 31) should be about 2 and the efficiency should be more than 86%. If the compression ratio of the front compression stage is lower than this, the compression ratio of the rear compression stages 22 and 32 becomes too large, so that the efficiency of the rear stage is lowered and the efficiency of the entire system is lowered. Therefore, when a general axial compressor is used for the front compression stages 21 and 31, two stages should be used, and there is a disadvantage in that the operating area is not wider than the centrifugal compressor due to the performance characteristics of the axial compressor. In the present invention, in order to solve this problem, the supersonic axial compressor (see FIG. 9) having a high compression ratio per unit ratio of 2: 1 or more and high performance and similar in performance to that of a centrifugal compressor is designed in the front compression stages 21 and 31. Applied. In addition, in the case of the rear compression stages 22 and 32, a turbo compressor that supplies air having an absolute pressure of 9 bar may have a compression ratio of about 5, and the possible adiabatic efficiency is about 80%. . In the case of using an intermediate cooler, the density of air flowing into the rear compressor is increased, which requires a small flow path area in the design of the compressor. As a result, the ratio of the end spacing to the height of the exit of the compressor impeller blade increases, resulting in lower efficiency. Falls short of On the other hand, in the case of the turbocompressor proposed in the present invention, since the intermediate cooler is not used, the density of the inlet air is reduced, and the flow path area can be increased in the design, thereby enabling the design of the rear stage compressor with higher efficiency.

In the case of the conventional turbo compressor, the compression ratio per unit of the centrifugal compressors used in each stage is around 2-3, which is why the efficiency decreases as the compression ratio increases, but the biggest problem is that the operating area becomes narrower. In the case of a turbo compressor, when the required amount of compressed air is small, it should be possible to operate with a reduction of 30% or more of the maximum supply flow rate in order to reduce power consumption, because this area decreases as the compression ratio per unit increases. As proposed in the present invention, when the centrifugal compressor having a compression ratio of about 5 per stage in the rear compression stages 22 and 32 is used as the rear compressor of the present application, the operating area that can be obtained is about 15-20%. In the case of the rear compression stage of the conventional turbo compressor, the method for increasing the operating area is to change the installation angle of the diffuser 16 used in the centrifugal compressor 19 to a variable type (see FIG. 12), but it is proposed in the present invention. In the case of the turbocompressor configuration, as shown in FIG. 11, the installation angle of the fixed blade 13 of the front axial compressor 18 is varied by using the apparatus used in the compressor of the engine used as the power unit for the aircraft. An increase is possible. As such, the method of changing the inflow angle of the air flowing into the rear stage centrifugal compressor 19 is not possible with a conventional turbocompressor using only a centrifugal compressor, and is possible only when the axial / centrifugal compressor is mixed as in the present invention.

In addition, by introducing an axial compressor that rotates at a high speed in the front end, the second technical problem is to implement an oilless system by introducing an air-floating bearing by reducing the size of the compressor rotating body to the same compressed air capacity.

When the intermediate cooler 52 is not used as proposed in the present invention, since the air temperature at the final outlet of the turbo compressor is very high, it is higher than 95% in order to lower it to a temperature of inlet temperature + 15 ° C. which is a general turbo compressor design standard. The third technical problem is to install rear coolers 24 and 35 having temperature efficiency.

In order to operate the compressor proposed in the present invention, a motor or an increase gear having a very high rotation speed of 70,000 RPM or more is required. Therefore, a high-speed motor having a rotation speed of 70,000 RPM or more can be directly implemented or a general electric motor of 3,600 RPM or 7,200 RPM. The fourth technical task is to implement a speed increase gearbox that increases the rotational speed of the motor to 70,000 RPM or more.

1 shows a general configuration of a turbocompressor according to the present invention.

* Explanation of the sign of FIG.

11: Inlet Guide Vane for controlling the air flow entering the front end

12: rotor blade of axial compressor as forward compression stage

13: fixed wing of axial compressor as forward compression stage

14: flow path connecting the front and rear ends

15: Impeller which is a rotor blade of centrifugal compressor which is a rear compression stage

16: Diffuser fixed wing of centrifugal compressor that is a rear compression stage

17: Scroll to collect and supply compressed air

18: forward axial compression stage consisting of a rotor blade and a fixed blade

19: rear centrifugal compression stage consisting of impeller and diffuser

2 shows a method of driving a turbocompressor using a high speed motor according to the present invention.

* Explanation of the sign of FIG.

21: forward compression stage

22: rear compression stage

23: High speed electric motor with more than 70,000 RPM

24: After Cooler

25: moisture remover

3 shows a method of driving a turbocompressor using a speed increase gear and a general motor according to the present invention.

* Explanation of the sign of FIG.

31: Forward compression end

32: rear compression end

33: Gearbox with a final speed of 70,000 RPM or more

34: General electric motor with 3,600 RPM or 7,200 RPM

35: After Cooler

36: moisture remover

4 shows the type of compressor suitable for use depending on the compressed air capacity and compression ratio.

5 shows a general configuration of a conventional centrifugal compressor.

* Explanation of the sign of FIG.

51: centrifugal compressor as the front compression stage

52: water-cooled intermediate cooler

53: centrifugal compressor as a rear compression stage

54: Gearbox

55: general electric motor

56: condensate treatment unit

57: rear air cooler

58: moisture remover

6 shows the type and maximum possible efficiency of the compressor according to specific speed.

7 shows the general shape of a compressor according to specific speed.

8 shows a general form of an air bearing.

Fig. 9 shows the shape of the supersonic axial compressor used in the present invention.

Fig. 10 shows the shape of a general mixed flow compressor.

Figure 11 shows a fixed wing variable system commonly used in axial compressors of aircraft engines.

12 shows the shape of a centrifugal compressor using a variable diffuser.

The present invention excludes the compression ratio of the front compression stage (21, 31) from the front compression stage (21, 31) consisting of a single stage axial compressor (18), which has a compression ratio per stage of about 2 and can have high adiabatic efficiency. Rear compression stages 22 and 32 composed of centrifugal compressors 19 for providing the remaining necessary compression ratios, and high speed electric motors 23 or geared gears 33 and general electric motors 34 which are driven by connecting them in one axis. Consists of. Between the front compression stage (21, 31) and the rear compression stage (22, 32) is connected by a simple duct 14 to minimize the pressure loss generated in the complex flow path of the conventional turbocompressor. Since the turbo compressor proposed in the present invention has a configuration in which the intermediate cooler 52 does not exist, the front axial flow in order to maintain the specific velocity of the rear centrifugal stage 19 at an optimum (about 60 to 100 degrees) to have high efficiency. Stage 18 is characterized by a very high optimum specific speed (about 200 to 400). To this end, a general electric motor 34 having a rotational speed of 3,600 RPM or 7,200 RPM and a speed increase gear 33 capable of increasing its rotation speed to 70,000 RPM or more, or a high speed electric motor capable of maintaining rotational speed of 70,000 RPM or more per minute ( 23) the compressor must be driven. For reference, the Tx-mini series, a 100-150 horsepower turbo compressor developed by IHI of Japan, drives the compressor by increasing the speed of a 7,200 RPM motor to 109,000 RPM using a gearbox. The compressed air finally discharged from the rear compression stage 19 is used after cooling by using separate rear coolers 24 and 35 of air cooling or water cooling. When the air flow required for the operation of the device is small, the inlet guide vane 11 at the inlet of the front compression stage 18, the fixed blade 13 of the front compression stage 18 and the diffuser 16 of the rear compression stage 19 By adjusting the installation angle, the air inflow can be reduced to reduce power consumption.

Since the axial compressor can obtain a higher efficiency than the centrifugal compressor, when the axial compressor 18 and the centrifugal compressor 19 are mixed and used as shown in the present invention, the front end of the axial compressor is the same as a conventional turbo compressor. Compared to the case where both the 51 and the rear end 53 are centrifuged, a high overall efficiency can be obtained and there is no problem of an increase in loss due to leakage flow in the rear of the impeller. In addition, the axial compressor requires a higher rotational speed than the centrifugal type because the optimum specific velocity is high, and thus the optimum specific velocity of the rear compression stages 22 and 32 constituted by the centrifugal compressor 19 without the intermediate cooler 52 is required. Can be maintained. Recently, due to the development of technology, the design risk for the high-speed rotating body is greatly lowered, and the size and weight of the same compressed air flow rate can be reduced due to the high rotational speed.

Such high speeds allow the design of rotors of reduced size and weight, so that air-floating bearings, which were not available in conventional turbocompressors of similar capacity, can be used, in which case the design of oil-free turbo compressors is possible. In addition, since the intermediate cooler is not used, the density of the air supplied to the rear end is lowered, and the compressor flow path area can be largely designed for the same flow rate, thereby enabling a higher efficiency rear stage compressor design.

In the case of using the axial / centrifugal mixing type as proposed in the present invention, the operating area of the inlet guide vane 11 in front of the axial compression stage and the fixed blade 13 of the axial compression stage can be used together to maximize the operating area. have. In addition, when the centrifugal compressor is used at the front stage of the two-stage turbo compressor, it is very difficult to vary the installation angle of the inlet guide vane and the fixed wing of the front compression stage together, but in the case of axial flow, this can be easily implemented. More than 10% additional operating area is available.

The present invention can be effectively widely applied in the field of the compressor using the turbo method of the reciprocating, screw, rotary, scroll, turbo compressor that is a mechanical device for supplying high-pressure compressed air and is not limited to the above embodiments It will be apparent to those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention.

Claims (4)

In a turbocompressor comprising a front compression stage, a rear compression stage and a power source, An axial compressor having an optimum specific speed of about 200 to 400 and a fixed wing having a variable blade shape is installed at the front compression stage, and a centrifugal compressor having an optimum specific speed of about 60 to 100 is installed at the rear compression stage, thereby entering the rear compression stage. Turbo compressor characterized in that to change the inlet angle of the air. In a turbocompressor comprising a front compression stage, a rear compression stage and a power source, An axial compressor having an optimum specific speed of about 200 to 400 and a fixed wing having a variable blade shape is installed at the front compression stage, and a vortex compressor having an optimal specific speed of about 100 to 200 is installed at the rear compression stage, thereby entering the rear compression stage. Turbo compressor characterized in that to change the inlet angle of the air. The method of claim 1, Turbo compressor characterized by increasing the operating area of the entire compressor by changing the fixed blades of the front compression stage and the diffuser installation angle of the rear compression stage together The method of claim 2, Turbo compressor characterized by increasing the operating area of the entire compressor by changing the fixed blades of the front compression stage and the diffuser installation angle of the rear compression stage together