Measuring and testing – Gas analysis – By vibration
Reexamination Certificate
1999-06-29
2001-04-03
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
By vibration
C073S023290, C073S025010, C073S589000, C073S597000
Reexamination Certificate
active
06209387
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
TECHNICAL FIELD
This invention relates to the field of determining the proportional chemical make up of a multi-component gas, and more particularly, to determining the proportional makeup by measuring the thermo-physical properties of multi-component gasses using speed of sound data.
BACKGROUND OF THE INVENTION
Accurate thermodynamic properties of hydrocarbons are essential for analyzing processes related to liquification, transportation, processing and storage of gaseous fuels. Among the properties of interest are the compression factor, heat capacity, entropy, enthalpy and others. These properties must be known about various gas mediums which are made of a mixture of components. Such parameters are used in determining the precise makeup of storage vessels and processing equipment as well as a multitude of other applications.
These properties are generally calculated from an equation of state using so called look up tables for the particular gas medium. However, these lookup tables do not include parameters for gas mediums that are composed of a mixture of elements. Also, the accuracy of properties calculated from an equation of state depends upon the accuracy of the experimental data used in the fitting process.
The state-of-the-art technology used to measure the thermodynamic characteristics of multi-component gas mediums include the use a gas chromatograph to determine the precise chemical makeup of the medium as known to those skilled in the art. Such equipment is quite expensive to produce, thereby raising the cost of determining the thermodynamic characteristics of a multi-component gas medium.
SUMMARY OF THE INVENTION
The present invention entails a system and method for determining the thermodynamic properties of a gas comprised of a mixture of elements by using speed of sound in conjunction with other data, where the precise components are known, but their proportionality is unknown. For purposes of this discussion, a gas that is made up of several elements is termed a multi-component gas. In the preferred embodiment, the density of a multi-component gas medium is ascertained by determining the acoustic impedance of, and the speed of sound though the gas medium and recording the measurements of these parameters.
The acoustic impedance of the gas medium is determined from the voltage loss across the transducer at maximum energy transfer to the gas medium at the transducer resonant frequency.
In the instant invention, the speed of sound through a particular gas medium is determined by timing the propagation of a sonic pulse sent through the gas medium. The sonic pulse is created by an ultrasonic transducer. The return pulse is detected by the transducer and sent back to the transducer interface. The transducer interface is connected to a data bus where a central processing unit will access the pulse timing information and calculate the actual speed of sound.
From the acoustic impedance and the speed of sound, the density of the multi-component gas is determined. Also, the temperature and pressure of the gas medium are measured. The system repeatedly measures these parameters and stores them in memory.
Next, the system examines the data gathered for a convergent temperature range from which a convergent series may be extrapolated. Once this range is found, the values of the measured parameters are extrapolated into a convergence series from which the thermo-physical properties of the multi-component gas are calculated. Thereafter, the thermo-physical properties calculated are employed to determine the precise makeup of the multi-component gas as a percentage of each component.
The present invention also provides for a method for determining the thermodynamic properties of a multi-component gas medium. The method comprises the steps of measuring the pressure, speed of sound, and acoustic impedance of the gas medium for particular temperatures and storing the measurements in memory. Thereafter, a convergent temperature range is identified from the stored measurements.
Once the convergent temperature range is identified, the step of calculating the thermodynamic properties of the gas medium is undertaken by performing several iterations of a convergent series extrapolated from the convergent temperature range. Finally, the step of determining the percentage of a plurality of gas components making up the gas medium is performed.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.
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Gas Research Institute
Pauley Petersen Kinne & Fejer
Wiggins David J.
Williams Hezron
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