JPH0443899A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To enhance the efficiency of a compressor in almost the whole operating area of the compressor by controlling the passage width of a diffuser portion according to the amount of air flow and the pressure ratio of air around an inlet opening to that around a discharge opening. CONSTITUTION:A centrifugal compressor is provided with a moving wall portion 28 located on one wall portion of a diffuser portion 25 and capable of being brought near to and separated from the other wall portion 27, an actuator 32 for moving the moving wall portion 28, and a control means 34 for driving the actuator 32 according to the amount of discharged air and the pressure ratio of air around the inlet opening 24 of housing 22 to that around the discharge opening 31 of the housing 22 so as to control the width of the passage between the moving wall 28 and the other wall portion 27. The passage width of the diffuser portion 25 is thus controlled according to the amount of air flow and the pressure ratio of air around the inlet opening 24 to that around the discharge opening 31 and the efficiency of the compressor is enhanced in almost the whole operating area of the compressor and also operation outside a surge region is made possible even during operation of an engine brake etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a centrifugal compressor equipped with an impeller and a diffuser.

(Prior Art) A conventional centrifugal compressor of this type is shown in FIG. 3. (For example, see Utility Model Application Publication No. 60-15933, etc.). Note that this conventional example is a centrifugal compressor for a turbocharger installed in an automobile engine, etc., and the compressor will be explained based on FIG. 3.

In FIG. 3, reference numeral 1 denotes the centrifugal compressor of the above-mentioned turbocharger 2, and the centrifugal compressor 1 includes a compressor housing 3, an impeller 4 housed in the compressor housing 3, and one end of the impeller 4 that penetrates through the impeller 4. 4
The drive shaft 5 is coupled to the drive shaft 5. And the drive shaft 5
The other end is connected to a turbine rotor 7 of an exhaust gas turbine 6, and although not shown, exhaust gas from an automobile engine is introduced into a turbine housing 8 that houses the turbine rotor 7, and the turbine rotor 7 moves at high speed. Accordingly, the impeller 4 is rotationally driven via the drive shaft 5.

On the other hand, in the compressor housing 3 of the centrifugal compressor 1,
An inlet 9 that introduces air into the impeller 4 from the axial direction, an annular diffuser section 10 that decelerates and pressurizes the air accelerated by the centrifugal force of the impeller 4, and the pressurized air that has passed through the diffuser section 10 and has been decelerated is collected. A spiral scroll portion 11 is formed. The pressurized air compressed by the centrifugal compressor 1 configured as described above is supplied to the intake pipe of the engine through a discharge port of the compressor housing 3 (not shown). Note that, as described above, in the turbocharger 2 that is driven using the exhaust gas of the automobile engine, the rotational speed of the impeller 4 of the centrifugal compressor 1 fluctuates as the load of the automobile engine changes. Therefore, for the purpose of ensuring compressor efficiency of the centrifugal compressor 1 in a wide air flow range from low speed to high speed of the impeller 4, the diffuser section 10 is not provided with vanes. The distance between the pair of opposing walls 10a and 10b forming the diffuser section 10, that is, the passage width of the diffuser section 100, is configured to be constant in the radial direction.

(Problem to be Solved by the Invention) However, in such conventional centrifugal compressors, although the passage width of the diffuser section is kept constant to cover the compressor efficiency over a wide range of air flow rates, ,
There is a limit to the maximum value of the compressor efficiency (for example, about 70b), and the compressor efficiency is low especially in the low-speed, small-flow range and the high-speed, large-flow range, so the engine load is low. And when the centrifugal compressor is under high load, that is, when the centrifugal compressor is running at low speed and a small flow rate, or at high speed and a large flow rate, there is a problem in that the compressor efficiency decreases, resulting in poor fuel efficiency or the engine not being able to obtain sufficient output. .

Furthermore, when the air flow rate is extremely low, such as during engine braking, a surge phenomenon occurs in the centrifugal compressor, causing a problem in that the compressor generates a large amount of noise.

Here, FIG. 4 shows an experiment in which the relationship between the air flow rate and the pressure ratio of the air pressure at the suction port and the discharge port in the conventional centrifugal compressor shown in FIG. 3 was measured in response to changes in the rotational speed of the impeller. The graph showing the results shows the equal efficiency line of the compressor shown as a broken line and the engine operating line shown as a double line,
That is, the required air flow rate and pressure ratio are plotted in response to the engine load. In Figure 4, when the compressor is running at low speed and a small flow rate, and when the compressor is running at high speed and a large flow rate, the compressor efficiency decreases.Moreover, when the engine operating line is in the small flow range, the compressor's surge line , it is clear that surging will occur if the air flow rate is extremely low as described above. In addition, in FIG. 4, the double dashed-dotted line indicates the operating line of the engine during a transient period.

(Objective of the Invention) The present invention has been made against the background of the problems of the prior art as described above, and it is an object of the present invention to control the passage width of a diffuser portion based on the air flow rate and the pressure ratio of air at the intake and outlet ports. This improves compressor efficiency over almost the entire operating range, and enables operation outside the surge range even during engine braking, improving engine output and fuel efficiency.Furthermore, noiseless centrifugal compression based on surging The purpose is to provide an opportunity.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a centrifugal compressor according to the present invention is housed in a housing, rotates and sucks air from an inlet of the housing, and uses centrifugal force to compress an impeller that reaches the and an annular diffuser part provided on the outer periphery of the impeller of the housing and formed by a passage between a pair of mutually opposing wall parts, and converts the kinetic energy given to the air by the impeller into pressure energy. In a centrifugal compressor that converts pressurized air into compressed air and discharges pressurized air from a discharge port of a housing, a movable wall portion provided on one wall of the diffuser portion and capable of approaching and separating from the other wall portion; An actuator that moves the wall, and a control means that controls the passage width between the moving wall and the other wall by driving the actuator based on the discharged air flow rate and the pressure ratio of the air at the inlet and outlet of the housing. It is characterized by having the following.

(Function) In the present invention, the passage width of the diffuser section is controlled based on the air flow rate and the pressure ratio of the air at the suction and discharge ports, so the compressor efficiency is improved over almost the entire operating range, and also during engine braking. etc., it is possible to operate outside the surge area. Therefore, engine output and fuel efficiency are improved, and noise caused by surging is eliminated.

(Example) Hereinafter, the present invention will be explained based on the drawings.

FIGS. 1 and 2 are diagrams showing an embodiment of a centrifugal compressor according to the present invention.

First, the configuration will be explained.

In FIG. 1, reference numeral 21 is an impeller housed in a housing 22. The impeller 21 is driven by a coaxially fixed drive shaft 23 to rotate, sucks air through an inlet 24 of the housing 22, and centrifuges the impeller 21. Accelerate by force. Note that, like the drive shaft 5 shown in FIG. 3 as a conventional example, the drive shaft 23 is connected to a turbine rotor of an exhaust gas turbine that rotates when exhaust gas from an automobile engine is introduced, although not shown. and is configured to rotationally drive the impeller 21 as described above. on the other hand,
Reference numeral 25 denotes a diffuser portion provided on the outer periphery of the impeller 21 of the housing 22, and the diffuser portion 25 includes a pair of mutually opposing wall portions 26 formed in the housing 22.
．． In this embodiment, a movable wall part 28 is provided on one wall part 26 on the suction port 24 side, and a parallel passageway is formed between the movable wall part 28 and the other wall part 27. A passage 29 is formed to constitute the diffuser section 25. Furthermore, the diffuser part 25 is formed in an annular shape along the outer periphery of the impeller 21, and the radially outward side communicates with a scroll part 30 formed in a spiral shape on the outer periphery of the housing 22. As described above, the air taken in from the suction port 24 is accelerated by the centrifugal force of the impeller 21 and given a large amount of kinetic energy.
When passing through the air, the air is decelerated and the kinetic energy is converted into pressure energy, which collects in the scroll portion 30 as pressurized air, and is further discharged from the outlet 31 of the housing 22 to the intake pipe of the engine (not shown).

As mentioned above, in FIG. 1, the movable wall section 28 is provided on one wall section 27 of the diffuser section 25. a stepped engagement surface 28a parallel to the drive shaft 23 formed in the
28b are similarly stepped guide surfaces 26 parallel to the drive shaft 23 formed radially inwardly and outwardly of the wall portion 26;
a, 26b, the movable wall portion 28 engages with the guide surfaces 26a,
It is possible to approach and separate from the other wall portion 27 along the line 26b. Furthermore, the reference numeral 32 indicates the scroll portion 3 of the housing 22.
The movable iron 32a of the electromagnetic solenoid 32 penetrates the wall 26 and engages with the movable wall 28, and the amount of current supplied to the electromagnetic solenoid 32 causes the electromagnetic solenoid 32 to move. The amount of protrusion changes to move the movable wall portion 28 along the guide surfaces 26a and 26b and move the wall portion 27 along the guide surfaces 26a and 26b.
move it closer to. That is, the electromagnetic solenoid 32 has a function as an actuator that moves the movable wall section 28, and furthermore, the electromagnetic solenoid 32 has a function as an actuator that moves the movable wall section 28 and the housing 2.
The movable wall portion 28 is urged to move away from the wall portion 27 against the electromagnetic solenoid 32 by the elastic force of the elastic member 33 interposed between the 74M solenoid 32. Depending on the amount, the moving wall part 28 and wall part 2
7, that is, the passage width B of the diffuser section 25 is set. Note that the elastic member 33 is attached to the movable wall portion 2 so as not to cause a short bus to the air cast scroll portion 30 accelerated by the impeller 21.
It also functions as a sealing member that seals between the housing 220 and the housing 220.

On the other hand, reference numeral 34 denotes a control unit, into which signals from a suction pressure sensor 35 and a discharge pressure sensor 36, which respectively detect the pressure of air at the suction port 24 and discharge port 31 of the housing 22, are input. A signal from an air flow meter 37 that detects the flow rate of air discharged from the outlet 31 is input. Then, the control unit 34 calculates the pressure ratio of the air at the suction port 24 and the discharge port 31 based on the signals of the suction pressure sensor 35 and the discharge pressure sensor 36,
Furthermore, based on the pressure ratio and the air flow rate output by the air flow meter 37, the amount of current to be energized to the electromagnetic solenoid 32 is set, and the i11! As a result, the passage width B of the diffuser section 25 is controlled.

That is, the control unit 34 drives the movable rod 32a of the electromagnetic solenoid 32 based on the discharged air flow rate and the pressure ratio of the air at the intake port 24 and the discharge port 31 of the housing 22, and moves the movable rod 32a between the movable wall portion 28 and the wall portion 27. It has a function as a control means for controlling the passage width B of.

Next, the effect will be explained.

In FIG. 1, exhaust gas from an automobile engine is introduced into an exhaust gas turbine (not shown), and a drive shaft 23 connected to a rotating turbine rotor is driven to rotate together with an impeller 21. The intake air taken in from the intake port 24 of the housing 22 is accelerated by the centrifugal force of the impeller 4, decelerated through the diffuser section 25, and then collected in the scroll section 30. At this time, the operating energy of the intake air accelerated by the impeller 4 is transferred to the diffuser section 2.
5, it is converted into pressure energy and is discharged as pressurized air from the scroll portion 30 through the discharge port 31 into the intake pipe of the engine. On the other hand, the control unit 34 receives signals from the suction pressure sensor 35 and the discharge pressure sensor 36, calculates the pressure ratio of air at the suction port 24 and the discharge port 31 of the housing 22, and further inputs the pressure ratio and the air flow rate meter 37. The amount of current to be energized to the electromagnetic solenoid 32 is set based on the air flow rate at the discharge port 31, and the electromagnetic solenoid 32 is energized. Then, the movable rod 32a of the electromagnetic solenoid 32 protrudes against the biasing cam of the elastic member 33, and stops at a position with a passage width B corresponding to the amount of current of the electromagnetic solenoid 32. As a result, the passage width B of the diffuser section 250 is controlled based on the above-mentioned air amount and pressure ratio.

Here, FIG. 2 is a characteristic diagram similar to FIG. 4 shown as a conventional example, and as shown in FIG. It is possible to move the characteristic curve including the surge line and the region of high compressor efficiency, for example, 70% or more, in response to a change in the width B. That is,
In FIG. 1, when the movable wall section 28 is brought closer to the wall section 27 and the passage width B of the diffuser section 25 is made smaller, the characteristic curve including the surge line and the region of high compressor efficiency become S, , E in the figure. As shown in the figure, if the air flow rate is smaller, the moving wall part 28 is separated from the wall part 27, and the passage width B is set to an intermediate position, the characteristic curve including the surge line and the region of high compressor efficiency are S in the figure. ,,E.

Move to the middle position of air flow rate as shown in .

Further, the movable wall portion 28 is separated from the wall portion 27 and the passage width B
As becomes even larger, the characteristic curve including the above-mentioned surge line and the region of high compressor efficiency move toward the side where the air flow rate is large, as shown by S2 and E3.

Therefore, by changing the passage width B of the diffuser section 25 in accordance with the operating conditions, the compressor efficiency can be maintained high over almost the entire operating range, and furthermore, it is possible to always operate in an area away from the surge line. It is possible to operate outside the surge range even during engine braking. In this embodiment, the control unit 34 stores the amount of current applied to the electromagnetic solenoid 32 that optimizes the passage width B of the diffuser section 25 using the air flow rate and pressure ratio as parameters. The control unit 34 controls the diffuser section 2 according to the engine operating condition.
5 i! It is possible to control the road width B to an optimum value.

As described above, in this embodiment, the control unit 34 controls the passage width B of the diffuser section 25 via the electromagnetic solenoid 32 based on the air flow rate and the pressure ratio of the air at the inlet 24 and the outlet 31. Therefore, compressor efficiency can be improved over almost the entire operating range, and operation outside the surge range is possible even during engine braking. Therefore, engine output and fuel efficiency can be improved, and noise caused by surging can be eliminated.

Note that the present invention is not limited to simply controlling the passage width B of the diffuser section 250, but is also applicable to a centrifugal compressor equipped with a vane-equipped diffuser section. That is, the compressor characteristics shown in FIG. 2 can also be obtained by controlling the mounting angle of the vanes by the control unit 34 via the electromagnetic solenoid 32. It goes without saying that similar effects can be obtained in this case as well.

(Effects) According to the present invention, the passage width of the diffuser section is controlled based on the air flow rate and the pressure ratio of the air at the suction and discharge ports, so it is possible to improve the compressor efficiency over almost the entire operating range. This also makes it possible to operate outside the surge region even during engine braking. Therefore, it is possible to provide a centrifugal compressor that is capable of improving engine output and fuel efficiency and is free from noise caused by surging, which is the object of the present invention.

[Brief explanation of drawings]

1 and 2 are diagrams showing an embodiment of a centrifugal compressor according to the present invention. FIG. 1 is a cross-sectional view of main parts showing its configuration, FIG. 2 is a diagram showing its characteristics, and FIG. 3 and 4 are diagrams showing a conventional example, and FIG. 3 is a front sectional view thereof, and FIG.
The figure is a diagram showing its characteristics. 21... Impeller, 22... Housing, 24... Inlet, 25... Diffuser part, 26.27... Wall part ( a pair of walls), 28...
...Moving wall portion, 29...Passage, 31...Discharge port, 32...Electromagnetic solenoid (actuator),
34...Control unit 7 (control? I1 means), B...Aisle width.

Claims (1)

[Claims] It is formed by an impeller that is housed in a housing and rotates to draw in air from the intake port of the housing and accelerates due to centrifugal force, and a passage between a pair of opposing walls that are provided around the outer periphery of the impeller in the housing. a centrifugal compressor that converts kinetic energy imparted to the air by the impeller into pressure energy and discharges pressurized air from a discharge port of the housing; A movable wall portion provided on a wall portion and capable of approaching and separating from another wall portion, an actuator for moving the movable wall portion, a discharged air flow rate, and a pressure ratio of air at an inlet port and a discharge port of the housing. 1. A centrifugal compressor comprising: control means for controlling a passage width between a moving wall and the other wall by driving an actuator based on the above.