JP4982775B2 - Diffuser gas vibration control device and vibration control method using the same - Google Patents

Description

  The present invention relates to a diffuser gas vibration control device and a vibration control method using the same.

  More specifically, the present invention relates to a diffuser gas vibration control device that is used in, for example, a jet engine or a turbine and converts velocity energy of a transonic compressible fluid into pressure energy, and a vibration control method using the same.

  When high-speed air flows in a closed space such as a duct or pipe of a jet engine or a turbine, a supersonic region is locally generated, which causes vibration and noise of the device itself due to the generation of a shock wave.

  This is unstable in principle, and depending on the flow conditions, such vibrations may increase, leading to fatigue or destruction of the equipment.

  Various proposals have been made for an apparatus for reducing engine pressure fluctuation. For example, Japanese Patent Application Laid-Open No. 2004-257311 (Patent Document 1 below) discloses a static device for reducing noise of an aircraft engine. A method is described in which a piezoelectric element is provided on a blade and the piezoelectric element acts so as to cancel pressure fluctuations in the wake of the moving blade.

  In Japanese translation of PCT publication No. 2007-513282 (Patent Document 2 below), the noise of the turbo engine is reduced by providing an actuator on the stationary blade to actuate the pressure fluctuation of the wake of the moving blade. Is described.

  Patent Document 1 and Patent Document 2 are specialized for an engine and control a wake generated when flowing between multistage blades (moving blades and stationary blades) inside the engine.

  That is, the main method is to control the turbulent flow generated from the rear end of the blade with a piezoelectric element or an actuator. In this case, it is assumed that there is an object in the flow and there is a subsequent flow.

  On the other hand, the flow field that is the premise of the present invention is not particularly necessary except that the high-speed fluid is an internal flow, and focuses on the critical state that dominates the flow state. In this position, a high-speed flow with a large energy is controlled using a piezoelectric element, which is completely different from Patent Document 1 and Patent Document 2 from the controlled object and the control philosophy.

  Conventionally, the reduction of vibration and noise caused by the flow has been realized by artificially reducing the vortex present in the flow and promoting the dissipation of energy.

However, such a method cannot cope with any flow field, and the control method using the actuator as described above is used. However, there is a problem that the control becomes difficult when the flow field energy to be controlled increases. .
JP 2004-257311 A Special Table 2007-513282

  The present invention solves the problems of the prior art as described above, and is used in a jet engine, a turbine, etc., and a gas vibration control device in a diffuser for converting the velocity energy of a transonic compressible fluid into pressure energy and the same It is an object to provide a vibration control method used.

The present invention has been made as a result of intensive studies to solve the above-described problems, and the gist of the present invention is the following contents as described in the claims.
(1) A piezoelectric element is installed in a throat portion of a diffuser through which a transonic compressive fluid passes, a pressure gauge is detected using a pressure gauge installed downstream of the throat portion, and the piezoelectric element is detected based on the pressure fluctuation. A gas vibration control device in a diffuser that controls the vibration of a gas in a diffuser by generating a shock wave or driving a shock wave by driving an element.
(2) Pressure diffuser and noise caused by vibration of gas flowing in the diffuser and vibration of the diffuser itself are reduced using the diffuser gas vibration control device according to (1). Gas vibration control method.
(3) A diffuser gas vibration control method, wherein the vibration control device according to (1) is used to amplify vibration of the gas in the diffuser and used as a speaker.
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According to the invention of (1), the piezoelectric element is installed at the throat portion of the diffuser through which the transonic compressive fluid passes, the pressure fluctuation is detected using the pressure gauge installed downstream of the throat portion, and the pressure The piezoelectric element is driven based on the fluctuation, and the pressure fluctuation due to the shock wave is actively utilized by utilizing the property of the compressible fluid, and the pressure fluctuation downstream of the throat is monitored, and this is used as an input signal for driving the piezoelectric element. By doing so, it is possible to control the vibration of the gas in the diffuser by performing arithmetic processing at the time of the feedback.
According to the invention of (2), the pressure fluctuation and noise caused by the vibration of the gas flowing in the diffuser and the vibration of the diffuser itself are reduced by using the gas vibration control device in the diffuser described in (1). be able to.
According to the invention of (3), the gas vibration in the diffuser can be used as a speaker by directly amplifying the control signal hydrodynamically using the vibration control device described in (1).

  By using the vibration control device according to the present invention, a very large energy such as a supersonic flow can be controlled with a very small control amount (maximum displacement of the piezoelectric element is about 1 mm). Furthermore, since the pressure is monitored at the position where the pressure fluctuation is the largest and the control is performed to cancel the pressure, it is possible to construct a noise reduction system very efficiently.

  In addition, if a vibration / noise reduction method is established, there is a possibility that arbitrary vibrations and sounds can be generated. Therefore, the present apparatus can be used as a loudspeaker that produces extremely loud sounds.

  In addition, by taking out the pressure fluctuation from the static pressure hole for pressure measurement and guiding it to the throat of a larger flow path, it is possible to amplify the pressure fluctuation hydrodynamically, and there are significant industrially useful effects. .

  The best mode for carrying out the present invention will be described in detail with reference to FIGS.

  Conventionally, in internal flows through which high-speed gas flows, such as those found in aircraft and high-pressure plants, the gas flowing inside easily reaches the speed of sound, and a supersonic region and shock waves are generated. Such a flow field is unstable in principle and causes noise and vibration of the equipment.

  In the case of the internal flow described above, since a valve, a bent pipe, and the like always exist, a portion where the flow path becomes narrow exists in a part of the flow. Such a narrow channel is called a transonic diffuser in the field of compressive fluid, its narrowest part is called a throat part, and it is known that the above-mentioned supersonic region and shock waves are easily generated downstream thereof. Yes.

  Although such a flow field is unstable and vibrates, a piezoelectric element is installed in the throat part, which is the position that most affects the flow field, and vibration associated with compressible flow and shock waves with extremely small displacement. It is an object of the present invention to control. .

  A basic configuration of the present invention is shown in FIG.

  In FIG. 1, 1 is a flow path upper surface, 2 is a flow path lower surface, 3 is a piezoelectric element, 4 and 5 are pressure gauges, 6 is an amplifier, 7 is an AD converter, 8 is a CPU, 9 is a DA converter, A direct-current amplifier 11 indicates a throat portion.

  In the present invention, a piezoelectric element 3 is installed in a throat portion 11 of a diffuser through which a transonic compressive fluid passes, and pressure fluctuations are detected using pressure gauges 4 and 5 installed downstream of the throat portion 11, The piezoelectric element 3 is driven based on the pressure fluctuation to generate a shock wave or vibrate the shock wave to control the vibration of the gas in the diffuser.

  That is, in the basic configuration of the present invention, the piezoelectric element 3 is installed in the throat portion 11 which is the narrowest position of the internal flow flowing at high speed, and the pressure fluctuation and noise in the flow path through which a large flow rate flows are reduced by the displacement. Is.

  Here, a diffuser is a device that sends a compressive fluid such as high-pressure gas used in jet engines and turbines from a high-pressure region to a low-pressure region to convert velocity energy into pressure energy. Transonic is a subsonic velocity. A flow field where supersonic speeds are mixed.

  When a high-speed compressible fluid (gas) flows in a closed space such as a duct or pipe of a jet engine or a turbine, a supersonic region is locally generated, and the accompanying shock wave is generated to cause vibration and noise of the equipment itself. It becomes.

  This is unstable in principle, and depending on the flow conditions, such vibrations may increase, leading to fatigue or destruction of the equipment.

  In FIG. 1, a metal flow channel surrounded by a flow channel upper surface 1 and a flow channel lower surface 2 is sealed with a transparent acrylic plate for observation. The piezoelectric element 3 is installed in the throat portion 11 with respect to this flow path. The piezoelectric element 3 used in the control device of the present invention is an actuator that can obtain the largest displacement at the tip, with the flat plate being bent in proportion to the voltage, and the displacement is realized in the shape shown by the wavy line.

  Here, a piezoelectric element refers to an element that generates strain (elongation / contraction) when applied with voltage. It generates a large force with a quick response to a voltage change, and can generate a strain approximately proportional to the voltage. Good controllability.

  In such a configuration, as shown in FIG. 1, when a compressive fluid (gas) flows from the left side to the right side of the drawing, a pressure wave or shock wave or the like is generated or vibrated downstream of the throat, resulting in a pressure fluctuation.

  The pressure fluctuation is measured by the pressure gauge 4 and the pressure gauge 5, and the signal is calculated by the CPU 8 through the amplifier 6 and the AD converter 7, so that a signal that reduces the pressure fluctuation is taken into account by considering the time delay. The signal is sent to the converter 9 and converted from a digital signal to an analog signal. The signal is sent to the piezoelectric element driving DC amplifier 10 to give displacement to the piezoelectric element 3 as an actuator, thereby realizing control of the entire flow field. By controlling pressure fluctuations and noise in the flow path in this way, fluctuations downstream thereof can be reduced. Therefore, it is extremely effective to perform control near the cause of vibration.

  The present invention is similar to the operating principle of a transistor. That is, it is similar to controlling a large current flowing from the collector to the emitter by controlling the base voltage, and a basic feedback circuit can be configured. Therefore, by operating the calculation in the CPU 8 shown in FIG. 1 during the feedback process, the voltage for driving the piezoelectric element can be arbitrarily changed, so that the gas flowing through the throat is almost arbitrarily controlled although the frequency is limited. It becomes possible to do. Furthermore, a system capable of flexibly controlling most pressure fluctuations can be constructed by using, for example, a genetic algorithm or a neural network during the calculation process in the CPU 8.

The piezoelectric element 3 has a relatively small displacement compared to the flow scale and does not have a high response frequency. However, it is considered that the piezoelectric element 3 is optimal for control of about several hundreds of Hz, which is a problem for the flow field. The piezoelectric element 3 is installed in the throat section 11 and the pressure fluctuation captured downstream is used as an input to a CPU or DSP (Digital Signal Processor), so that the reverse phase of the pressure fluctuation is used by the driving voltage of the piezoelectric element. The active control can reduce pressure fluctuation and noise. When higher frequency control is required due to noise characteristics, downsizing of the device, or necessity of control over sound waves, a stacked piezoelectric element is effective instead of the bimorph type used in this device. This is because the bimorph type displacement is comparatively large but the response frequency is comparatively small at about 1 kHz, whereas in the case of a laminated piezoelectric element, several hundred kHz can be easily handled. However, the multilayer piezoelectric element has a small displacement, and hydrodynamic amplification is effective as a means for solving this.
FIG. 2 is a diagram illustrating an installation method of a transonic diffuser and a piezoelectric element in the present invention.

  As shown in FIG. 2, for example, the bimorph type piezoelectric element is installed so that the throat portion is located at the portion where the amplitude is the largest.

  FIG. 3 shows the piezoelectric element installed in the throat portion.

  FIG. 3A shows an element in which three wirings are extended, and this is connected to a DC amplifier so that it bends in a direction perpendicular to the paper surface in the figure. FIG. 3 (b) shows the thickness. A thickness of 1 mm can achieve a displacement of about 0.8 mm at the tip.

  FIG. 3 (c) is taken from the downstream side after being installed on a metal, and FIG. 3 (c) is taken from the direction of displacement in the vertical direction. The piezoelectric element used in the present invention is about 0.8 mm even at the portion where the displacement of the tip is the largest, but it is the original idea of the present invention to install this at the throat portion.

FIG. 4 is a diagram illustrating a speaker using the diffuser gas vibration control device of the present invention.
As shown in FIG. 4, the gas vibration in the diffuser can be used as a speaker by directly amplifying a control signal hydrodynamically using the vibration control device of the present invention.

  When a high-speed flow is caused to flow from the left side to the diffuser using the experimental apparatus shown in FIG. 5, a shock wave is generated on the right side from the throat portion.

  In this experiment, in order to control the irregular vibration of the shock wave, a piezo element was installed in the throat part, the piezo element was vibrated, and the throat height was changed periodically.

  First, the air compressed by the compressor was turned into a tank, and after returning to the stagnation point in the collecting cave, it was passed through the diffuser. At this time, the pressure in the collective tunnel is set to p0, and the value obtained by non-dimensionalization at the atmospheric pressure pb is set as the wind tunnel pressure ratio. This wind tunnel pressure ratio is set in advance, and a signal is sent from the computer when the set wind tunnel pressure ratio is reached. The flow field was visualized using the Schlieren method, skipping the spark.

  As a result of this experiment, the remarkable effect of the piezoelectric element on the flow field was confirmed as shown in FIG. That is, in FIG. 6A showing the state of the flow field when the piezoelectric element is not installed, a shock wave is generated at a position where x / h is about 42. On the other hand, in FIG. 6B in which the piezoelectric element was installed, it was confirmed that the shape and generation position of the shock wave were changed, and in particular, the position was changed in conjunction with the displacement of the piezoelectric element.

  In addition, in order to quantitatively evaluate the effect of such a piezoelectric element, a pressure sensor was installed downstream, and the influence of the driving frequency of the piezoelectric element was confirmed. The result is shown in FIG. FIGS. 7A and 7B are frequency analysis results of downstream pressure fluctuations when the driving frequency of the piezoelectric element is set to 100 Hz and 300 Hz as sine waves, respectively.

  As shown in FIG. 7, it shows an excellent frequency distribution in the driving frequency of the piezoelectric element, and it can be seen that the other frequencies are extremely small. If this response is used, the input signal to the piezoelectric element that reduces the downstream pressure fluctuation can be obtained by calculation, and by applying this, the fluctuation reducing effect can be sufficiently expected, and the effect of the present invention has been confirmed. It was.

  8 and 9 show the mean square value (rms) indicating the magnitude of pressure fluctuation at the position of distance x = 20 mm from the throat downstream when the wind tunnel pressure ratio is gradually increased and the position of the shock wave, respectively. Show.

  FIG. 8 shows that the pressure fluctuation at x = 20 mm is the largest when the wind tunnel pressure shown on the horizontal axis is about 1.2. In addition, since it decreases sharply when it becomes larger than this, when constructing the feedback system described above, the position where pressure fluctuation is monitored is 20 mm downstream of the throat if the pressure ratio is operated at 1.2. I understand. It is clear from the shock wave position shown in FIG. 9 that the pressure fluctuation becomes maximum when the wind tunnel pressure ratio is 1.2. That is, it is known that the shock wave moves downstream as the wind tunnel pressure increases, but in the case of the apparatus of the present invention, the shock wave exists at a position of about 20 mm when the wind tunnel pressure ratio is about 1.2 from FIG. I understand. At this time, the shock wave is constantly oscillating, and the pressure measurement position relatively crosses the upstream and downstream of the shock wave, so that a sudden pressure fluctuation occurs due to the pressure before and after the shock wave.

  The pressure before and after the shock wave is known to change discontinuously from the theory of compressible fluid dynamics (Rankyn-Yugonio relationship), and can be theoretically determined from the position where the shock wave is generated. Therefore, the optimal combination of the shock wave generation position, pressure measurement position, and operating pressure ratio is basically to set the operating pressure ratio so that the shock wave is located at the pressure measurement position. Can be set in consideration of any operating condition.

  Therefore, for example, when the pressure is monitored at a position at x = 30 mm, it can be seen from FIG. 9 that the operating condition at which the pressure fluctuation is maximum is 1.4, which is the pressure ratio where the shock wave is located at 30 mm. In the figure, the same experiment as a parameter was performed by changing the frequency, but almost the same result was obtained at any frequency, and the operation state does not depend on the frequency. Therefore, the control device of the present invention has a frequency characteristic. It can be said that it is good.

The possibility of commercialization using the present invention is first to reduce vibration and noise generated in a large flow rate at a very high speed, such as a jet engine. In such a flow field, high-temperature and high-pressure combustion gas is ejected from the injection port of the jet engine, so the flow cannot be directly controlled but must be controlled indirectly. For this purpose, the present invention is extremely effective as a control device, and furthermore, a very light and small component such as a piezoelectric element is added, and it is hardly necessary to consider an increase in weight.

  Next, the vibration control device of the present invention can be miniaturized because the elements themselves are extremely small. When considering application in a high-pressure plant, a noise / vibration reduction device corresponding to any scale is applicable. .

  Furthermore, considering the operating speed of the actuator, it can be applied to a very wide frequency band, so it is also possible to create a large output speaker without cones using compressed air. enable. Alternatively, in consideration of the propagation characteristics of sound waves depending on the direction of flow, it is possible to realize a speaker with high directivity.

It is a figure which illustrates the basic composition of the diffuser gas vibration control device in the present invention. It is a figure which illustrates the installation method of the transonic diffuser and piezoelectric element in this invention. It is a figure which illustrates the piezoelectric element used for this invention. It is a figure which illustrates the speaker using the diffuser gas vibration control apparatus of this invention. It is a figure which shows the experimental apparatus of the gas vibration control apparatus in a diffuser of this invention. It is a figure which shows the pressure fluctuation by the experimental apparatus of the gas vibration control apparatus in a diffuser of this invention. It is a figure which shows the frequency analysis result of the pressure fluctuation in the flow path by the experimental apparatus of the diffuser gas vibration control apparatus of this invention. It is a figure which shows the root mean square value (rms) which shows the magnitude | size of the pressure fluctuation in the position of distance x = 20mm from the throat downstream at the time of performing gradually increasing a wind tunnel pressure ratio in this invention. It is a figure which shows the position of the shock wave at the time of performing gradually increasing a wind tunnel pressure ratio in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow path upper surface 2 Flow path lower surface 3 Piezoelectric element 4 Pressure gauge 5 Pressure gauge 6 Amplifier 7 AD converter 8 CPU
9 DA converter 10 DC amplifier 11 Throat section

Claims (3)

  A piezoelectric element is installed in the throat part of the diffuser through which the transonic compressive fluid passes, pressure fluctuation is detected using a pressure gauge installed downstream of the throat part, and the piezoelectric element is driven based on the pressure fluctuation. A gas vibration control apparatus in a diffuser that controls the vibration of a gas in a diffuser by generating a shock wave or vibrating the shock wave.   A gas vibration control in a diffuser characterized by reducing pressure fluctuation and noise caused by vibration of gas flowing in the diffuser and vibration of the diffuser itself using the gas vibration control device in the diffuser according to claim 1. Method.   2. A diffuser gas vibration control method, wherein the vibration control device according to claim 1 is used as a speaker by amplifying vibration of gas in the diffuser.

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