Measuring and testing – Gas analysis – By vibration
Reexamination Certificate
1998-01-05
2001-09-11
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
By vibration
C073S024060, C073S030020, C073S030040, C073S031050, C073S03200R, C073S054260, C073S054380, C073S054410, C073S061790, C073S064530
Reexamination Certificate
active
06286361
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the detection of pressure or temperature, and in particular to the remote detection of pressure, force, temperature, density, vibration, viscosity and speed of sound in a fluid in hollow articles.
BACKGROUND OF THE INVENTION
The failure of mechanical articles, or components, by fatigue cracking can occur if the article, or components, are exposed to cyclic loading or vibrations. The failure of a fan blade of a turbofan gas turbine engine by fatigue cracking is unacceptable and cracks must be detected before they reach a size at which they could cause the fan blade failure. The fan blades of some turbofan gas turbine engines are hollow, and the cracks are most likely to form through the walls defining the hollow chamber in the fan blades. These hollow fan blades are evacuated during the manufacturing process.
A known method of detecting cracks in hollow fan blades is to place a piezoelectric transducer on the surface of the hollow fan blade such that it is acoustically coupled to the hollow fan blade. The piezoelectric transducer is electrically excited to generate ultrasound at a particular frequency, for example 150 kHz, in the hollow fan blade. The piezoelectric transducer is then used to detect the ultrasound in the hollow fan blade and an analyser is used to monitor the decay rate of the amplitude of the ultrasound at the particular frequency. It has been found that the decay rate of the amplitude of the ultrasound at the particular frequency is proportional to the pressure in the hollow fan blade. Thus if there is a crack in the hollow fan blade the pressure is greater in the hollow fan blade than for an uncracked fan blade and therefore the decay rate for the cracked hollow fan blade has a higher decay rate than for an uncracked hollow fan blade.
The inspection of a full set of hollow fan blades on a turbofan gas turbine engine is extremely time consuming. The inspection of the hollow fan blades requires an inspector to couple the piezoelectric transducer to, and to test, each hollow fan blade in turn.
The prior art method and apparatus for detecting these pressure within the hollow fan blade is not automatic, is time consuming and requires contact between the detection apparatus and the hollow fan blade.
SUMMARY OF THE INVENTION
The present invention seeks to provide a method and apparatus for detecting the pressure, force, temperature, density, vibration, viscosity and speed of sound in a fluid in an article which overcomes the above mentioned problems.
Accordingly the present invention provides a method of remotely detecting pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid, the method comprising:
providing at least one magnetostriction transducer,
providing means to produce a varying magnetic field in spaced apart relationship with the magnetostriction transducer,
producing a varying magnetic field such that the varying magnetic field acts upon the at least one magnetostriction transducer to generate vibrations in the at least one magnetostriction transducer,
providing means to detect the vibrations in spaced apart relationship with the magnetostriction transducer,
detecting the vibrations generated in the at least one magnetostriction transducer by the varying magnetic field,
and analysing the detected vibrations to determine the pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid.
The magnetostriction transducer may be located in an article. The article may be a hollow article.
The analysing of the detected vibrations may be by analysing the amplitude and/or the frequency and/or these damping and/or the phase.
The analysing of the damping may be by detecting the decay rate of the amplitude of the vibrations in the at least one magnetostriction transducer or the article at a particular frequency.
The analysing of the frequency may be by detecting changes in the resonant frequency of the vibrations in the at least one magnetostriction transducer or the article.
The analysing of the frequency may be by detecting changes in the amplitude of the vibrations in the at least one magnetostriction transducer or the article at or around the resonant frequency.
The analysing of the frequency may be by detecting changes in the magnetic flux.
There may be two magnetostriction transducers in the hollow article, a first one of the magnetostriction transducers is in communication with the hollow interior of the hollow article and the second one of the magnetostriction transducers is not in communication with the hollow interior of the hollow article, the magnetostriction transducers having different resonant frequencies.
The vibrations may be ultrasounds.
The analysing may comprise displaying the pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid. The analysing may comprise produce a warning that the pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid is at a predetermined level.
The present invention also provides an apparatus for remotely detecting pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid comprising, at least one magnetostriction transducer, means to produce a varying magnetic field arranged in spaced apart relationship with the magnetostriction transducer such that a varying magnetic field acts upon the at least one magnetostriction transducer to generate vibrations in the at least one magnetostriction transducer, means to detect the vibrations generated in the at least one magnetostriction transducer, the means to detect the vibrations is arranged in spaced apart relationship with the magnetostriction transducer, and analysing means to analyse the detected vibrations to determine the pressure, force, temperature, density, vibration, viscosity or speed of sound in a fluid.
The magnetostriction transducer may be located in an article. The article may be a hollow article.
The means to analyse the detected vibrations may be means to analyse the amplitude and/or the frequency and/or the damping and/or the phase.
The means to analyse the damping may be means to detect the decay rate of the amplitude of the vibrations in the at least one magnetostriction transducer or the article at a particular frequency.
The means to analyse the frequency may be means to detect changes in the resonant frequency of the vibrations in the at least one magnetostriction transducer or the article.
The means to analyse the frequency may be means to detect changes in the amplitude of the vibrations in the at least one magnetostriction transducer or the article at or around the resonant frequency.
There may be two magnetostriction transducers in the hollow article, a first one of the magnetostriction transducers is in communication with the hollow interior of the hollow article and the second one of the magnetostrictior transducers is not in communication with the hollow interior of the hollow article, the magnetostriction transducers having different resonant frequencies.
The at least one magnetostriction transducer may comprise a magnetostrictive member and a damping member secured to the magnetostrictive member, the damping member having a large surface area.
The at least one magnetostriction transducer may comprise a magnetostrictive plate and a damping plate secured to one face of the magnetostrictive plate.
The at least one magnetostriction transducer may comprise a magnetostrictive member arranged in a sealed chamber, the sealed chamber is evacuated.
The sealed chamber may be defined by at least one flexible wall, the flexible wall may be arranged permanently in contact with the magnetostrictive member or may be arranged to move into and out of contact with the magnetostrictive member. The magnetostriction transducer may comprise a rigid cylindrical wall having a rigid end wall and a flexible end wall defining the sealed chamber and a magnetostrictive member extending between and contacting the rigid end wall and the flexible end wall. There may he m
Brown Ian D
Greenough Rodney D
Jones Alan R
Pollard Duncan
Webster John R
Manelli Denison & Selter PLLC
Miller Rose M.
Rolls-Royce plc
Taltavull W. Warren
Williams Hezron
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