Means and method for testing the homogeneity of a solution
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The system and the method of the present invention relates to the testing of the homogeneity of solutions in general and, more particularly, to the optical testing of homogeneity. 
     SUMMARY OF THE INVENTION 
     The system and the method of the present invention tests the homogeneity of a solution utilizing a housing which includes a first chamber for a reference solution and a second chamber for a test solution. The housing also includes a pair of transducers spatially related to the first and second chambers for providing signals in accordance with incident lights. The housing also includes a light source which provides light equally to both chambers in a manner so the light passes through the solutions in both chambers to be incident upon the transducers. Circuitry connected to the transducers provide an output signal related to the quality of the test solution in accordance with the signals provided by the transducers. 
     The objects and advantages of the invention will appear more fully hereinafter, from a consideration of the detailed description which follows, taken together with the accompanying drawings wherin one embodiment is illustrated by way of example. It should be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified block diagram of a system constructed in accordance with the present invention to test the homogeneity of a solution. 
     FIG. 2 is a simplified schematic type drawing of the housing means shown in FIG. 1. 
     FIG. 3 is a simplified block diagram of the test means shown in FIG. 1. 
     FIGS. 4A and 4B are diagrammatic representations of signal E6 for a poor homogeneousness of a test solution and for a good homogeneousness of a test solution, respectively. 
    
    
     DESCRIPTION OF THE INVENTION 
     Polyacrylamide is commonly used as a water viscosifying agent for Enhanced Oil Recovery projects in which mobility control is desired. A technical requirement for the use of some forms of polyacrylamide consists of grinding logs of solid polyacrylamide gel, dissolving this substance in field water such that it is well dispersed and no gel or high concentration micelles exist and finally injection under pressure of this mixture into an oil reservoir, via an injection well. Similar technical requirements of mixing also exist when liquid emulsions of polyacrylamide, kerosene and surfactant such as Nalco&#39;s Nalflo 555 are mixed with water. 
     If the mixing process is incomplete, plugging of the injection face of the well could occur. Field data indicates that undetected incomplete mixing has resulted in much higher injection pressures than desired. Since thousands of gallons of this mixture are injected and since polyacrylamide is known to be difficult to mix, many instances of poorly mixed injection solutions are observed in practice. One answer to the problem is to mix for a sufficient time to insure a homogeneous mixture, however it is difficult to predict this duration or to catch small lumps whose effects are small but cumulative. Operator observation of the injected fluid during the injection process is not practical as it is labor intensive and may also not result in catching lumps or &#34;fish eyes&#34; as inhomogeneous poorly mixed regions are called. 
     The present invention depends on the fact that poorly mixed solutions alter the transmission of light differently than well mixed solutions. The difference in optical transmission is characterized by an ensemble pattern recognition approach and it is this pattern difference which is detected. 
     Referring now to FIG. 1, a housing 1 is divided into two chambers 1A and 1B. The construction and operation of housing 1 will be discussed more fully hereinafter. A reference solution means 6 provides a thoroughly homogeneously mixed solution of the same type as is the solution to be tested, hereinafter referred to as the test solution, by way of a line 8 which is pumped by a pump 10. The reference solution enters chamber 1A through an entrance port 15 and exits chamber 1A of housing 1 by way of an exit port 17. The reference solution returns to reference solution means 6 by way of a line 20. 
     Similarly a test solution source means 25 provides the test solution through a line 27 utilizing a pump 30. The test solution enters chamber 1B of housing 1 by way of an entry port 33 and leaves chamber 1B through an exit port 37. The test solution is provided to an electrically operated two way valve 40 which can either provide the test solution back to test solution source means 25 via a line 42 for more mixing or if the test solution passes the test it is provided to holding means 45 by way of line 47. Holding means 45 provides the test solution to a well head when desired. 
     Housing 1 has a light source and provides light through chambers 1A and 1B, as hereinafter explained, in which the light passing through the reference solution and the test solution result in electrical signals E1 and E2 being provided to test means 50. Test means 50 will be described in greater detail later on. Suffice to say that test means 50 utilizes signal E1 and E2 to determine if the test solution is of the desired quality. Test means 50 provides a control signal E3 to valve 40. When the test solution is acceptable valve 40 is controlled to pass the test solution to holding means 45. When the test solution is not acceptable, signal E3 causes valve 40 to return the test solution to test solution source means 25 for further mixing. Test means 50 provides another signal E4 to alarm means 54. Alarm means 54 may include audio or visual alarms or both. When the test results are unacceptable, signal E4 causes the alarms of alarm means 54 to be activated. Test means 50 provides a signal E5 to recorder means 58 for recording the results of the test. Recorder means 58 may be a strip chart recorder or may be any other type of recording device. 
     Referring now to FIG. 2, housing 1 includes light means 63, which may be a conventional light source, providing light to a defusing filter 66. Defusing filter 66 permits one to use an inexpensive light source, which essentially provides a point of light, and assure the equal distribution of light intensity over the entire field so as not to develop regional errors. The defused light is provided to a movable polarizer 70. Polarizer 70 may be of the type sold by Ray Enterprises Inc. under their part number 241661701. Polarizer 70 is mounted on and supported by an axle (not shown) which passes through housing 1. The external edge of polarizer 70 has teeth so that polarizer 70 may be rotated around the axle (not shown) by a drive gear 73 rotated by a motor 75. The reason for rotating polarizer 70 will be explained hereinafter. 
     Positioned between chambers 1A and 1B and polarizer 70 is an optically clear barrier 80 which may be purchased from Ray Enterprises Inc., as their part number 241665827. Light passing through polarizer 70 and barrier 80 enters chambers 1A and 1B through which the solutions are flowing as previously explained. The light passing through chambers 1A and 1B passes through another optically clear barrier 84 and thence through a stationary polarizer 88. Polarizer 88 may be the same type of polarizer as polarizer 70. A light tight cover means 92 has photoelectric cells 94 and 96 mounted on it which provide signals E1 and E2, respectively in accordance with the light incident upon them. 
     Referring now to FIG. 3, test means 50 includes a difference signal means 100 receiving signals E1, E2 and provides a signal E6 corresponding to the difference between signals E1 and E2. Difference signal means 100 may be a differential operational amplifier with associated circuitry. Signal E6 is provided to a root mean square signal means 105 which in turn provides a signal E7 representative of the root mean square of signal E6. Signal E7 is provided to logic means 110 which utilizes signal E7 to provide signals E3, E4 and E5. It should be noted that logic means 110 is not novel in itself and the details of which are not needed to understand the present invention. Suffice to say that logic means 110 would include circuitry to provide signals E3 and E4 when signal E7 exceeds certain predetermined criteria. Signal E5 would be provided in accordance with signal E7 so that a record of the test may be made. 
     In operation, reference solution means 6 and test solution source means 25 simultaneously provide their solutions to chamber 1A and 1B, respectively, of housing 1. Light means 63 provides light which is diffused by diffusing element 66. The diffused light is provided to rotating polarizer 70. Whenever polarizer 70 and polarizer 80 are in phase with each other there will be full light transmission from light means 63 through chambers 1A, 1B to cells 94 and 96, respectively, except for the attenuation of the light by the solutions in chambers 1A and 1B. Whenever polarizers 70, 88 are at right angles to each other, that is 90 degrees out of phase with each other, light will pass through chambers 1A and 1B. However, due to the polarization effects of polarizers 70 and 88 being out of phase, substantially no light will reach photo cells 94 and 96. Thus it can be seen that during each revolution of polarizer 70 the intensity of light passing through chambers 1A and 1B and incident upon photo cells 94 and 96, respectively, will be sinusoidal in form. Accordingly, signals E1 and E2 will have peaks of one polarity when polarizers 70 and 88 are in phase and peaks of another polarity when polarizers 70 and 80 are 90 degrees out of phase. For every complete revolution of polarizer 70 there will be four peaks to each signal E1 or E2. 
     With reference to FIGS. 4A and 4B, FIG. 4A shows signal E6 when there has been poor mixing of the test solution. As a result the difference between signals E1 and E2 is great and shows up as a large peak-to-peak swing of signal E6. On the other hand, when there is good mixing of the test solution, the difference between signals E1 and E2 is small and signal E6 would appear similar to that what is shown in FIG. 4B. 
     Although the present invention has heretofore been described in a testing of polyacrylamide in a solution used in an enhanced oil recovery project, it may also be utilized to test for poorly mixed solutions of polysaccharides, such as Xanthan, or any other type of solution in other industrial fields.