Abstract:
A system and method for verification of acoustic horn performance is disclosed. This system and method includes a pressure detecting mechanism that converts at least one vibratory sound energy pulse, which is followed by at least one vacuum pulse or at least one negative pressure pulse, into a signal that is proportional to a level of sound energy, and the pressure detecting mechanism is operable to be connected to an acoustic horn. There is a measurement device that measures a value that correlates to the signal that is proportional to a level of sound energy and is electrically connected to the pressure detecting mechanism.

Description:
BACKGROUND OF INVENTION 
     This invention relates to acoustic horns, and more particularly, to an apparatus and method for verification of acoustic horn performance. 
     An acoustic horn is a gas operated device that produces low frequency, e.g., 60 Hertz to 300 Hertz, high-energy sound waves and is used for cleaning in many industrial applications. The sound waves that are emitted from an acoustic horn resonate and dislodge dust or ash deposits from surfaces. A significant advantage of an acoustic horn is that the acoustic horn can be used to remove dust or debris from locations that are difficult to clean by conventional methods. This includes surfaces that are inaccessible or surfaces that are subject to a high temperature or a high voltage. Therefore, there are numerous applications for acoustic horns. For example, in industrial or utility boilers, acoustic horns are used to clean boiler tubes and heat exchangers. In addition, acoustic horns are often used to clean Selective Catalytic Reduction (SCR) equipment. In these two applications, the acoustic horns are used to supplement or replace conventional steam soot blowers. For industrial, gas pollution, control filters, including electrostatic precipitators and bag houses, acoustic horns are utilized to clean the internal components. In these applications, the acoustic horns are utilized to supplement or replace existing conventional mechanical methods. Acoustic horns are also utilized to clean surfaces associated with material handling operations including collecting hoppers, fans, silos and ductwork. 
     The intensity at which an acoustic horn operates and its frequency are related to the cleaning effect. There are a number of factors in real world applications that may affect this intensity. These factors include the supply gas pressure and the gas flow. For example, when the supply gas pressure is reduced or the gas piping is restricted, the intensity of the acoustic horn will be reduced. Moreover, when the driver components for the acoustic horn are worn or the acoustic horn malfunctions, then the intensity of the acoustic horn will also be reduced. 
     There are two common methods for testing the intensity of an acoustic horn. The first method is to measure the supply gas pressure while the acoustic horn is being operated and the second method is to disassemble the driver components associated with the acoustic horn and measure these driver components for wear. Both processes provide a very indirect measurement of intensity. The second process, which involves the disassembly and measurement of the driver components, is very slow and tedious. Also, this second process results in significant downtime for the acoustic horn. 
     One method for measuring the intensity and frequency of an acoustic horn in real time is by using a microphone. The microphone is placed near the area being cleaned. However, this cleaning is typically accomplished with more than one acoustic horn. When an acoustic horn sounds, the microphone can detect the amplitude and the frequency of the sound. However, a significant problem arises when more than one acoustic horn sounds simultaneously since the microphone cannot differentiate between the two acoustic horns. Also, the measured intensity is a function of the position of the microphone and the surrounding acoustics at that particular location. Moreover, an additional problem is the background noise or vibration that may be present where either the acoustic horn or the microphone is mounted. Furthermore, a microphone cannot measure absolute pressure or a pressure pulse followed by a vacuum pulse or a negative pressure pulse. All of these variables can lead to uncertainty in the measurement process. Since the microphones are located in areas being cleaned from dust and debris, these microphones may potentially be in an atmosphere that is corrosive, dust-laden and/or subject to a high temperature or voltage. 
     Another problem that arises when utilizing acoustic horns is that since the acoustic horn operates in a dust-laden environment, some of this debris will enter the bell and driver of the acoustic horn. This can be very detrimental to the operation of the acoustic horn. Therefore, purge gas is sometimes supplied to the acoustic horn to pressurize the bell and prevent the accumulation of this material within the acoustic horn. Consequently, it is necessary to know the ambient positive or the negative pressure of the acoustic horn. 
     The present invention is directed to overcoming one or more of the problems set forth above. 
     SUMMARY OF INVENTION 
     In one aspect of this invention, a system for verification of acoustic horn performance is disclosed. This system includes a pressure detecting mechanism that converts at least one vibratory sound energy pulse, which is followed by at least one vacuum pulse or at least one negative pressure pulse, into a signal that is proportional to a level of sound energy, wherein the pressure detecting mechanism is operable to be connected to an acoustic horn. 
     In another aspect of this invention, a method for verification of acoustic horn performance is disclosed. This method includes operatively connecting an acoustic horn to a pressure detecting mechanism that converts at least one vibratory sound pulse, which is followed by at least one vacuum pulse or at least one negative pressure pulse, to a signal that is proportional to a level of sound energy. 
    
    
     These are merely two illustrative aspects of the present invention and should not be deemed an all-inclusive listing of the innumerable aspects associated with the present invention. These and other aspects will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings. 
     BRIEF DESCRIPTION OF DRAWINGS 
     For a better understanding of the present invention, reference may be made to the accompanying drawings. 
     FIG. 1 is a perspective view of a system of the present invention for verification of acoustic horn performance utilizing a pressure detecting mechanism, e.g., pressure transducer, operable connected to an acoustic horn with an electronic measurement device, e.g., multimeter, for determining a quantity of sound pressure from the pressure detecting mechanism. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, a perspective diagram of a system of the present system for verification of acoustic horn performance is generally indicated by numeral  10 . The acoustic horn  56  includes two main components. The first component is a compressed gas driver  52  and the second component is a bell  50 . The bell  50 , typically but not necessarily, has a diameter that is relatively small near the compressed gas driver  52  and the diameter gradually increases along the length of the bell  50  towards an opening  49  at the end of the bell  50 . 
     The compressed gas driver  52  is attached to the bell  50  with a flange  51 . Contained within the compressed gas driver  52  is a diaphragm plate  53  that is preferably, but not necessarily, made of titanium. Compressed gas is supplied from a compressed gas supply  54 , which can include, but is not limited to, any of a wide variety of compressors. The compressed gas supply  54  is connected in fluid relationship to the diaphragm plate  53  by a hose  48 . The compressed gas is introduced into the compressed gas driver  52  and pressure builds rapidly causing the diaphragm plate  53  to flex. The gas pressure escapes past the diaphragm plate  53  and into the bell  50 , which reduces the gas pressure in the compressed gas driver  52 . This pressure reduction in the compressed gas driver  52  causes the diaphragm plate  53  to snap back quickly thereby creating a pressure pulse in the bell  50  that is followed by a vacuum pulse, or in some cases, a negative pressure pulse if negative pressure is usually present in the acoustic horn  56  prior to the introduction of the compressed gas. This vacuum pulse or negative pulse can be measured within the bell  50  and seems to be the strongest near the compressed gas driver  52  and then seems to dissipate in a direction towards the opening  49  at the end of the bell  50 . These vacuum pulses or negative pulses are virtually undetectable at the opening  49  at the end of the bell  50 . 
     This cycle is repeated for as long as gas is being supplied to the acoustic horn  56 . These pressure pulses travel the length of the bell  50  and emit from the opening  49  of the acoustic horn  56  in the form of strong bursts of acoustic energy capable of dislodging ash or dust deposits. The gas pressure of the pulses near the compressed gas driver  52  is characteristically high where the diameter of the bell  50  is relatively small and the gas pressure of the pulses decreases along the length of the bell  50  as the diameter of the bell  50  increases. Compressed gas is preferably supplied in a range from about 3.51 kilograms per square centimeter gauge (50 p.s.i.g.) to 6.33 kilograms per square centimeter gauge (90 p.s.i.g.) A representative acoustic horn  56  is disclosed in U.S. Pat. No. 5,636,982, which issued to Santschi et al. on Jun. 10, 1997 and is assigned to BHA Group, Inc. and is entitled Method and Apparatus for Acoustically Enhancing Cooling of Clinker, which is incorporated herein by reference. 
     A pressure transducer  38  is operatively connected to the bell  50  of the acoustic horn  56 . This provides a pulse measurement signal when the acoustic horn  56  is being operated to detect high-pressure pulses. There is very little signal that is developed by the concurrent use of more than one acoustic horn  56  in close proximity. This is because the pressure transducer  38  only responds to an absolute pressure pulse followed by either a vacuum pulse or a negative pressure pulse and not the mere presence of ambient sound or vibration so that there is a high signal-to-noise ratio. This high signal-to-noise ratio allows the noise or ambient sound to be filtered out or ignored. Therefore, when the acoustic horn  56  is being operated, the electrical signal generated by the pressure transducer  38  is indicative of the intensity and the frequency of the vibratory sound energy generated by that particular acoustic horn  56 . When the acoustic horn  56  is not being operated, the pressure transducer  38  measures the ambient or negative pressure that may be present within the bell  50  of the acoustic horn  56 . This is when the acoustic horn  56  is pressurized and supplied with purge gas to remove accumulated debris from the bell  50  of the acoustic horn  56 . For this application, a pressure transducer preferably measures pressure pulses between 20 pounds per square inch gauge (−1.41 kilograms per square centimeter gauge) to about +40 pounds per square inch gauge (+2.81 kilograms per square centimeter gauge) and more preferably from about 10 pounds per square inch gauge (−0.703 kilograms per square centimeter gauge) to about +20 pounds per square inch gauge (+1.41 kilograms per square centimeter gauge). 
     In the preferred embodiment of this present invention, an opening is made in the acoustic horn  56  and a first gas pressure port  44  is installed. The location of this first gas pressure port  44  can be located virtually anywhere along the length of the bell  50 , however, a preferred location is 3.81 centimeters (1.5 inches) from the compressed gas driver  52 . The size of the opening (not shown) and the associated first gas pressure port  44  depends on the size of the pressure transducer  38 . Preferred, but nonlimiting, illustrative diameters include 0.874 centimeters (0.344 inches) for the opening and 0.318 centimeters (0.125 inches) for the first gas pressure port  44 . The first gas pressure port  44  is connected in fluid relationship to the pressure transducer  38  through tubing  42 . An illustrative, but nonlimiting example of this type of tubing  42  includes tubing such as that supplied by McMaster Carr®. McMaster Carr® is a federally registered trademark of McMaster-Carr Supply Company, having a place of business at 600 County Line Road, P.O. Box 680, Elmhurst, Ill. 60126. An illustrative, but nonlimiting example, includes Model No. 5235K42, having a diameter of 0.318 centimeters (0.125 inches). The preferred material is rubber, however, any of a wide variety of materials will suffice as a conduit for the transmission of sound energy pressure waves. The length of the tubing  42  can vary, with the preferred length being less than 0.61 meters (two (2) feet). Additional length could dampen the pressure pulses to the point where amplification might be required. The tubing  42  is attached to the pressure transducer  38  through a second gas pressure port  40  that is, preferably but not necessarily, substantially similar to the first gas pressure port  44 . 
     An illustrative, but nonlimiting example of a pressure transducer  38  includes those manufactured by SenSym ICT, having a place of business at 1804 McCarthy Boulevard, Milpitas, Calif. 95035, Model SENSYM SDX 30A4, which is a piezo resisitive-type transducer. There is temperature compensation and a high level of output. 
     A second illustrative, but nonlimiting example of a pressure transducer  38  includes those manufactured by Setra Systems, Inc., e.g., Model Number 2251-ZO6PC-2M-2C-06. Setra Systems, Inc. has a place of business at 159 Swanson Road, Boxborough, Mass. 01719-1304. This pressure transducer  38  preferably has a measurement range from about −1.03 kilogram per square centimeter gauge (14.7 p.s.i.g.) to about +2.48 kilogram per square centimeter gauge (+35.3 p.s.i.g.). 
     A wide variety of other pressure measurement devices may be substituted for the pressure transducer  38  including pressure sensors both resistive-type, piezo-electric, and capactitive-type sensors. This also includes strain-gauge sensor technology, e.g., silicon. 
     Preferably, the first gas pressure port  44  and the pressure transducer  38  is located away from an area that is being cleaned by the acoustic horn  56  so that the potentially high temperature, corrosive, dust laden atmosphere is located away from the acoustic horn performance verification system  10 . 
     One way of measuring the pressure from the pressure transducer  38  is through the use of a meter  12 . This meter  12  can include any of a wide variety of electronic measurement devices. Illustrative, but nonlimiting, examples of these electronic measurement devices include an oscilloscope to measure the wave shape of the vibratory sound energy. A preferred, but nonlimiting example, of a meter  12  includes a voltmeter or a multimeter that measures voltage. These devices may be incorporated into custom measurement circuits. An example would include a FLUKE® Model 189 True RMS multimeter. FLUKE® is a registered trademark of the Fluke Corporation, having a place of business at 6920 Seaway Boulevard, Everett, Wash. 98203. 
     There is a myriad of ways for electrically connecting the pressure transducer  38  to the meter  12 . The preferred method includes a first female banana jack  34  and a second female banana jack  36  located on the pressure transducer  38  and electrically connected thereto. Moreover, there is also a third female banana jack  18  and a fourth female banana jack  20  located on the meter  12  and electrically connected thereto. In addition, there is a first electrical conductor  22  that includes a first male banana jack  30  that is capable of being inserted within the first female banana jack  34  for the pressure transducer  38  and a second electrical conductor  24  that includes a second male banana jack  32  that is capable of being inserted within the second female banana jack  36  for the pressure transducer  38 . The other end of the first electrical conductor  22  includes a third male banana jack  26  that is capable of being inserted within the third female banana jack  18  associated with the meter  12  and other end of the second electrical conductor  24  has a fourth male banana jack  28  that is capable of being inserted within the fourth female banana jack  20  associated with the meter  12 . The meter  12 , if a multimeter, typically includes a function selector that rotates to different functions such as measuring voltage, current, resistance, and so forth. The meter  12  preferably includes an electronic display and preferably a liquid crystal diode display, however a light emitting diode, cathode ray tube and other types of electronic displays will suffice. A simple analog meter or dial will also provide an indication as to the amount of voltage amplitude or frequency. 
     The meter  12  is preferably battery-powered when power is not readily available. When the acoustic horn  56  is operated, the intensity of the sound energy can be measured by the meter  12 . This can preferably include a RMS value, peak value, minimum value and average value. Also, the frequency of the vibratory sound energy can also be measured. This is optimally performed with an oscilloscope. Measurements preferably occur before and after the application of gas from the compressed gas supply  54  to determine the ambient positive or negative pressure. 
     Therefore, the acoustic horn verification system  10  accurately measures the intensity and frequency of the vibratory sound energy generated by the acoustic horn  56 . The intensity and frequency of the vibratory sound energy generated by the acoustic horn  56  is indicative of the level of performance and the proper operation of the acoustic horn. This measure of performance is substantially independent and unaffected by the use of other acoustic horns  56  in the area as well as background noise and vibration. A major advantage of the acoustic horn verification system  10  is that the measurements can be made outside of the areas being cleaned. 
     Another significant advantage of the acoustic horn verification system  10  is the accurate measurement of the ambient pressure or negative pressure that is present in the bell  50  of the acoustic horn  56 . Since sound pressure measurement can be performed both before and after the operation of the acoustic horn  56 , the acoustic horn verification system  10  is not affected by the operation of the acoustic horn  56 . 
     Still another significant advantage of the acoustic horn verification system  10  is that the first gas pressure port  44  can be installed in the field and this system adapts to virtually any type of acoustic horn  56  regardless of the make or manufacturer. 
     Although the preferred embodiment of the present invention and the method of using the same has been described in the foregoing specification with considerable details, it is to be understood that modifications may be made to the invention which do not exceed the scope of the appended claims and modified forms of the present invention done by others skilled in the art to which the invention pertains will be considered infringements of this invention when those modified forms fall within the claimed scope of this invention.