Measuring and testing – Gas analysis – By vibration
Reexamination Certificate
2000-02-02
2002-10-08
Kwok, Helen (Department: 2856)
Measuring and testing
Gas analysis
By vibration
C073S861040
Reexamination Certificate
active
06460402
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for the quantitative analysis of a fluid that has known components. More particularly, the present invention relates to a system for measuring acoustic pulses in the multiple-component fluid. In particular, the present invention relates to a velocimeter and a method of applying acoustic transmission delay data to empirical correlations with the multiple-component gases.
2. Relevant Technology
Many fluid flow applications require real-time evaluation for various reasons such as fluid quality evaluation. and process control. Such real-time evaluation is only complicated where the fluid is a mixture of multiple components. For applications such as in the natural gas industry for gas-fired systems, or in the carburation of a fuel mixture for an internal combustion engine, operating parameters may critically depend upon the ratio of fluid components in relation to each other. Where a correlation exists for known ratios between multiple components and a given parameter of a particular mixture, such a correlation may be used to facilitate an optimal process that uses the mixture.
One example of the need for real-time evaluation is with natural gas internal combustion engines. Natural gas may have a methane content in a range from about 75% to about 99% methane. This methane composition range can vary between different sources and also the life of the source and the time of year in which the natural gas is removed from the source. Engine knocking is the phenomenon of a pre-ignition of the fuel in the combustion chamber. Knocking has a detrimental and often destructive effect upon the internal combustion engine combustion chamber. It is important therefore in this example of the need for real-time evaluation, to allow an internal combustion engine to be reconfigured in its combustion cycle depending upon the quality of the natural gas that is being supplied.
A well-understood correlation that can be applied to a given process may have a wide variety of applications. Examples thereof include the above-mentioned applications and others such as in the paper and pulp industry, the textile industry, the petroleum industry, materials and chemical testing, effluent monitoring, environmental discharge monitoring, and fluid commodity delivery. All of these applications could all be greatly affected by such a system.
Various problems and challenges occur depending upon the selected multiple-component fluid. For example, gaseous systems have been limited to conventionally lower frequencies because of the extreme attenuation of a high frequency audio signal in the gaseous system. Another difficulty occurs in a gaseous system where the particular geometry confines the distance between a transmitter and a receiver to close proximity. In such a system, there tends to be capacitative coupling between the transmitter and receiver. A capacitative coupling tends to generate a spurious signal that can be misinterpreted by the system as a response signal from the generated acoustic signal.
Another problem occurs where such systems are used around other equipment and machinery. In such an environment, electromagnetic and acoustic noise may be generated at frequencies that are similar to those designed to be detected in the testing system.
What is needed in the art is a system for quantitatively estimating the make-up of a known multiple-component fluid that overcomes the problems of the prior art. What is needed is a system that overcomes such problems as the unavoidable spurious signal that is generated where capacitative coupling in a gaseous system due to the geometry of the system requires the transmitter and receiver transducers to be in close proximity to each other. What is needed in the art is a system that can operate at high frequencies such that a rapid response and adjustment to the multiple-component fluid can be made for optimal performance of a given process.
Such systems, methods, and apparatuses are disclosed and claimed herein.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention relates to a system for quantitatively determining the components of a known multiple-component fluid.
In one embodiment of the invention, the system uses a “sing-around” circuit that filters out capacitative coupling in a gaseous system. In this embodiment of the present invention, a high-frequency audio signal is generated from a transmitter and detected by a receiver. A high frequency audio signal experiences extreme attenuation in a gaseous system. However, a portion of the audio signal reaches the receiving transducer. The audio signal is converted into an electronic signal that is sent to a triggering system. Due to the extreme attenuation of the audio signal, the electronic signal must be boosted by an amplification circuit sufficient to create a triggering signal.
In the triggering system, the electronic signal is amplified to assist in overcoming the extreme attenuation of the audio signal. Following amplification, the signal is rectified and gathered into a substantially half wave form. Spurious signals that are generated due to capacitative coupling and other causes are filtered out by a gate or digital filter. The digital filter is tuned to anticipate approximately the time period when actual signals should pass therethrough and the digital filter simply eliminates any other signals that come outside the anticipated signal time window. Following digital filtration, the wave form is converted into a square wave and optionally changed in pulse width to optimize it as a triggering signal. The triggering signal is then ultimately sent to a pulser that instructs the transmitter to generate another audio signal.
A “keep-alive” circuit is also provided in the sing-around loop for the occasion where no signal is detected to be cycling within the loop. The keep-alive circuit is configured to look for a pulse coming from upstream in the circuit loop. It looks for a pulse of a particular waveform, namely the square wave, and of a particular pulse width that is characteristic of that which was made of the circuit following digital filtration and conversion into a square wave. Where the anticipated signal is not received within a particular time window, the “keep alive” circuit generates its own signal, directed to the pulser, that instructs the transmitter to generate another audio signal in the direction of the receiver.
In any event, a pulse signal is generated and directed to the transmitter. At this point, a new audio signal is generated from the transmitter and detected by the receiver. After a number of cycles, the “sing-around” circuit settles down to its designed cycling time. The amount of time required to relay the signal from the receiver around to the transmitter is known. The largest time lapse in the circuit is the time required for the audio signal to bridge the distance between the transmitter and the receiver. As such, the speed of sound in the known multiple-component fluid can be extracted from the total cycling time of the circuit.
As the components of the multiple-component fluid are known, a database comprising the speed of sound at various component ratios of the known multiple-component fluid may be referred to and an estimate of the precise composition of the multiple-component fluid may be made. The simplest systems comprise binary, or two-component fluids. Two-component fluids generally have a linear or simple non-linear relationship such as the speed of sound as a function of concentration of the two components in the fluid.
Where the multiple-component fluid is a ternary system, a quaternary system, or greater, additional properties of the multiple-component fluid may need to be tested for determination of the ratios of the individual components. Examples of additional properties may include heat capacity, electrical conductivity, spectroscopic qualities such as nuclear magnetic resonance, infrared, and others, and optical qualities such as fluid color and index of refraction. Where a
Gomm Tyler J.
Kraft Nancy C.
Phelps Larry D.
Taylor Steven C.
Bechtel BWTX Idaho, LLC
Kwok Helen
Workman & Nydegger & Seeley
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