BACKGROUND OF THE INVENTION

&null;0001&null; 1. Field of the Invention

&null;0002&null; The present invention relates to a device for detecting operational instability during an operation of turbo compressors and, more particularly, to an instability detecting device used for easily and simply detecting a rotating stall and/or a surge frequently occurring during an operation of a turbo compressor.

&null;0003&null; 2. Description of the Prior Art

&null;0004&null; As well known to those skilled in the art, when a turbo compressor is operated in a stall region or a surge region having an insufficient amount of working fluid caused by a gradual reduction in the amount of working fluid during an operation and being lower than a predetermined reference level, the compressor undesirably experiences a rotating stall or a surge. Such a rotating stall or a surge deteriorates the operational performance of the turbo compressors, and sometimes causes serious mechanical damage or breakage of the compressors. Therefore, it is necessary to quickly and precisely detect an occurrence of such a rotating stall or a surge during an operation of the turbo compressors.

&null;0005&null; In the prior art, high-frequency pressure sensors, vibration sensors, or signal analyzing systems have been used for detecting such a stall or a surge during an operation of turbo compressors. However, the above-mentioned detecting equipments, such as high-frequency pressure sensors, vibration sensors, or signal analyzing systems typically used for detecting the rotating stall or the surge in the prior art, undesirably require the use of a complex and difficult analyzing process. Furthermore, such conventional detecting equipments are very expensive, thus undesirably increasing the installation cost, maintenance cost and repairing cost of the turbo compressors. In addition, the complex detecting equipments force operators to be highly skilled in the manipulation of the equipments. It has been thus necessary to provide a simple equipment designed to easily and reliably detect such a rotating stall and/or a surge during an operation of the turbo compressors at low cost.

SUMMARY OF THE INVENTION

&null;0006&null; Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an instability detecting device for turbo compressors, which easily, simply and reliably detects a rotating stall and/or a surge during an operation of such compressors while reducing the installation cost, maintenance cost and repairing cost of the compressors, different from the conventional detecting equipments, such as high-frequency pressure sensors, vibration sensors, or signal analyzing systems.

&null;0007&null; In order to accomplish the above object, the present invention provides an instability detecting device for turbo compressors, comprising: a detector consisting of: a body; first and second pressure tubes axially set in the body while parallely extending on the same plane, with first and second pressure discharge ports of the first and second pressure tubes exposed to the outside of the body at an end surface of the body; and a partition wall arranged on the end surface of the body while crossing the end surface and separating the first and second pressure discharge ports of the pressure tubes from each other, whereby the detector is attached to the inlet suction port of a compressor's impeller such that the partition wall extends in parallel to a rotation axis of the impeller, and/or to an outlet discharge port of a compressor's impeller such that said partition wall extends in parallel to a discharge flow from impeller, the detector thus sensing a pressure difference between the first and second pressure discharge ports of the pressure tubes and detecting an operation of the compressor within an unstable operational region.

&null;0008&null; In the instability detecting device, the detector may be connected to a monitor allowing an operator to know operational conditions of the compressor so as to detect an operation of the compressor within the unstable operational region.

&null;0009&null; In addition, the detector may be provided with a means for alerting the operator of an operation of the compressor within the unstable operational region.

&null;0010&null; When the turbo compressor is operated within a stable operational region, the working fluid flows along the partition wall prior to being introduced into the suction port of the impeller and/or into the discharge port, and so any pressure difference between the first and second pressure discharge ports of the pressure tubes is not detected. However, when the compressor is operated within an unstable operational region to form a rotating stall and/or a surge, the working fluid flows in a direction perpendicular to the partition wall prior to being introduced into the suction port of the impeller, and so a pressure difference between the first and second pressure discharge ports of the pressure tubes is detected. It occurs also if the detector is introduced into the discharge port of the impeller.

&null;0011&null; The detected pressure difference is applied to a U-shaped pressure tube, or is converted into an electric signal prior to being displayed on the monitor, thus allowing an operator to be informed of an operation of the compressor within the unstable operational region. The detecting device of this invention also alerts the operator of the operation of the compressor within the unstable operational region through a visual signal or a voice signal.

BRIEF DESCRIPTION OF THE DRAWINGS

&null;0012&null; The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

&null;0013&null; FIG. 1 shows an instability detector included in the detecting device for turbo compressors in accordance with the preferred embodiment of the present invention, in a front view and a sectional view;

&null;0014&null; FIG. 2 is a view, showing the instability detector of this invention attached to a turbo compressor;

&null;0015&null; FIG. 3 is a graph showing a standard pressure difference as a function of a rotating angle of the instability detector of this invention;

&null;0016&null; FIG. 4 is a graph showing a static pressure rise coefficient as a function of a flow coefficient of the instability detecting device of this invention;

&null;0017&null; FIG. 5a is a graph showing a standard pressure difference as a function of a rotating angle of the instability detecting device of this invention within a stable operational region;

&null;0018&null; FIG. 5b is a view, showing a flow of the working fluid of the instability detecting device of this invention within the stable operational region;

&null;0019&null; FIG. 6a is a graph showing a standard pressure difference as a function of a rotating angle of the instability detecting device of this invention within an unstable operational region; and

&null;0020&null; FIG. 6b is a view, showing a flow of the working fluid of the instability detecting device of this invention within the unstable operational region.

DETAILED DESCRIPTION OF THE INVENTION

&null;0021&null; Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components.

&null;0022&null; FIG. 1 shows an instability detector 20 included in the detecting device for turbo compressors in accordance with the preferred embodiment of the present invention, in a front view and a sectional view. FIG. 2 is a view, showing the instability detector 20 attached to a turbo compressor.

&null;0023&null; As shown in the drawings, the instability detecting device for turbo compressors of this invention includes a detector 20, which is attached to the inlet suction port 14 of a turbo compressor's impeller 12. This detector 20 is used for detecting a pressure difference formed at the inlet suction ports 14 of the impeller 12 in accordance with the flowing direction of working fluid introduced into the inlet suction port 14.

&null;0024&null; In order to accomplish the desired operational performance, the instability detector 20 has a longitudinal cylindrical body 22, with first and second pressure tubes 25 and 26 axially set in the body 22 while being spaced apart from each other. The first and second pressure tubes 25 and 26 extend in parallel to each other, with a first pressure discharge port 25a of the first pressure tube 25 and a second pressure discharge port 26a of the second pressure tube 26 exposed to the outside of the body 22 at an end surface of the body 22. In the body 22 of the detector 20, the two pressure tubes 25 and 26 are arranged on the same plane. A partition wall 28 is diametrically arranged on the end surface of the body 22 while crossing the end surface and separating the two pressure discharge ports 25a and 26a of the pressure tubes 25 and 26 from each other.

&null;0025&null; Each of the two pressure tubes 25 and 26 has a pressure sensor (not shown) or a U-shaped pressure tube (not shown), which is used for sensing pressures of the tubes 25 and 26 and outputs electric signals or visual signals indicating the sensed pressures.

&null;0026&null; As shown in FIG. 2, the instability detector 20 of this invention is attached to the inlet suction port 14 of the impeller 12 such that the partition wall 28 extends in parallel to the rotation axis of the impeller 12.

&null;0027&null; During an operation of the impeller 12, the flow rate of the working fluid at the outlet port of the turbo compressor is cyclically changed while measuring the pressures P1 and P2 at the two pressure discharge ports 25a and 26a of the pressure tubes 25 and 26. The measured pressures P1 and P2 are shown in the graph of FIG. 3. During such a pressure measurement, the detector 20 is rotatable at an angle of 360&null; in response to the outlet flow velocities of the working fluid at the two pressure discharge ports 25a and 26a. In addition, a plurality of calibration curves according to the outlet flow velocities of the working fluid are formed prior to making the calibration curves dimensionless using both a total pressure Pt and a static pressure Ps.

&null;0028&null; As shown in the graph of FIG. 3 showing the dimensionless calibration curves, the calibration curves are similar to each other regardless of the outlet flow velocities. This means that the detector 20 of this invention is usable regardless of the capacity or the size of the turbo compressor or the rpm of the impeller 12.

&null;0029&null; FIG. 4 is a graph showing a static pressure rise coefficient as a function of a flow coefficient of the instability detector 20 of this invention. This graph thus shows the operational performance of the turbo compressor within both a stable operational region 9 and an unstable operational region 10.

&null;0030&null; FIG. 5a is a graph showing the standard pressure difference as a function of the rotating angle of the instability detector 20 of this invention within the stable operational region 9. In the graph of FIG. 5a, the reference characters &null;A&null;, &null;B&null; and &null;C&null; denote the operating points &null;A&null;, &null;B&null; and &null;C&null; of the turbo compressor of FIG. 4. As shown in the graph of FIG. 5a, the turbo compressor accomplishes the same operational tendency regardless of the operating points within the stable operational region 9.

&null;0031&null; As shown in FIG. 5b, showing a flow of the working fluid of the instability detector 20 within the stable operational region 9, the pressures at the two pressure discharge ports 25a and 26a within the stable operational region 9 are less likely to be different from each other when the instability detector 20 is attached to the inlet suction port 14 of the impeller 12 such that the partition wall 28 extends in parallel to the rotation axis of the impeller 12 so as to make a zero rotating angle of the detector 20. That is, when the detector 20 is attached to the inlet suction port 14 of the impeller 12 as described above, the working fluid flows along the partition wall 28, and applies the same pressure to the two pressure discharge ports 25a and 26a.

&null;0032&null; FIG. 6a is a graph showing the standard pressure difference as a function of the rotating angle of the detector 20 of this invention within the unstable operation region 10. In the graph of FIG. 6a, the reference characters &null;D&null; and &null;E&null; denote the operating points &null;D&null; and &null;E&null; of the turbo compressor of FIG. 4. As shown in the graph of FIG. 6a, the turbo compressor accomplishes the same operational tendency regardless of the operating points within the unstable operational region 10. On the other hand, it is noted that the operational tendency of the turbo compressor within the unstable operational region 10 is completely different from that of the compressor within the stable operational region 9. As shown in FIG. 6b, showing a flow of the working fluid of the instability detector 20 within the unstable operational region 10, the pressure difference between the two pressure discharge ports 25a and 26a within the unstable operational region 10 is maximized when the detector 20 is attached to the inlet suction port 14 of the impeller 12 such that the partition wall 28 extends in parallel to the rotation axis of the impeller 12 so as to make a zero rotating angle of the detector 20. That is, when the detector 20 is attached to the inlet suction port 14 of the impeller 12 as described above, the working fluid flows in a direction perpendicular to the partition wall 28, thus maximizing the pressure difference between the two pressure discharge ports 25a and 26a.

&null;0033&null; The instability detecting device of this invention detects the pressure difference between the two pressure discharge ports 25a and 26a of the detector 20, and displays the pressure difference on a monitor during an operation of a turbo compressor as shown in FIGS. 5a and 6a. Therefore, it is possible for an operator of the turbo compressor to easily check the operational conditions of the compressor.

&null;0034&null; In addition, the detector 20 of the present invention may be connected to a means for informing an operator of the turbo compressor of an unstable operation of the compressor through a visual alarm means, such as an alarm lamp, or a voice alarm means, such as a speaker. That is, during an operation of the turbo compressor, the instability detecting device logically compares the pressure difference between the two pressure discharge ports 25a and 26a of the detector 20, and outputs an electric signal to the alarm means so as to allow the alarm means to inform the operator of an unstable operation of the compressor through a visual signal or a voice signal. In response to the visual or voice signal of the alarm means, the operator easily and quickly controls the compressor to change the operational region of the compressor from the unstable region to the stable region.

&null;0035&null; In the preferred embodiment of this invention, the instability detector 20 is installed at the inlet port of the turbo compressor. However, it should be understood that the instability detector 20 may be installed at the outlet discharge port of the turbo compressor without affecting the functioning of the present invention.

&null;0036&null; As described above, the present invention provides an instability detecting device for turbo compressors. This detecting device has a simple construction, thus being easily and simply produced at low cost. The detecting device of this invention is not an electric or electronic equipment having a complex construction, and so it is easily and simply operated, maintained and repaired at low cost, thus being convenient to an operator. Furthermore, this detecting device has a high operational reliability.

&null;0037&null; The detecting device of this invention is easily operated even by an unskilled operator, and is usable with a conventional turbo compressor regardless of the capacity, size and rotational speed of the compressor. The detecting device does not have any ill-effect on the operational performance of the turbo compressors.

&null;0038&null; The instability detecting device of this invention allows an operator of a turbo compressor to easily monitor the operational conditions of the compressor, thus allowing the operator to effectively control the operation of the compressor.

&null;0039&null; When the instability detecting device of this invention is used with a conventional operation control system for turbo compressors, it is possible for the detecting device to quickly inform an operator of an unstable operation of the compressor, thus allowing the operator to quickly control the operation of the compressor to restore a stable operation. Therefore, the detecting device of this invention almost completely prevents a reduction in the operational performance of the turbo compressors, and protects the compressors from severe damage or breakage during an operation.

&null;0040&null; Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.