Interferometric JFTOT tube deposit measuring device
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsRobert E. Morris, Robert Wagner
Life of this patent
Estimating the term…
Abstract
Jet fuels are tested for thermal stability by passing the fuel over a hea metal tube and measuring the amount of residue deposited as a film on the tube as a result of chemical changes to the fuel. The thickness distribution and volume of a deposited film on a tube are calculated by scanning the length of the tube with an optical probe, shining light onto the tube, measuring the intensity of reflected light of a preselected wavelength from the tube, and correlating the reflected light intensity with positions on the tube. The tube is then partially rotated, and the process is repeated until the entire surface of the tube is scanned. The volumes of each longitudinal slice of the tube are summed to give the total deposit volume on the tube.
Claims20
A device for measuring the thickness and volume of a deposit on a heater tube having a long axis and a circumference, comprising:
- (a) an optical probe wherein said probe is aimed at the tube;
- (b) a light source, optically coupled to said probe;
- (c) a detector of reflected light, for detecting reflected light of a predetermined wavelength, optically coupled to said probe;
- (d) means for longitudinally translating said optical probe, parallel to the long axis of the tube, thereby longitudinally traversing the tube;
- (e) means for axially rotating the tube about its long axis;
- (f) means for computing the thickness and volume of the deposit on the tube in accordance with the equations:
- ##EQU5## where t is the thickness of the deposit at a point on the tube, m is the thickness multiplier, .lambda. is the wavelength of the detected light, n is the refractive index of the deposit, and .theta. is the angle at which the source optics are oriented with respect to the heater tube, and ##EQU6## where V.sub.slice is the volume of the deposit on a longitudinal traversal of the tube, A is the area under the thickness profile along the tube, L is the length of the tube, r is the radius of the tube, and d is the number of longitudinal traversals around the tube circumference.
A method for measuring the thickness and volume of a deposit on a heater tube comprising:
- (a) producing light;
- (b) transmitting said light to an optical probe for transmission onto and from the tube, wherein said probe is optically coupled to a light detector and wherein said probe is aimed at the tube;
- (c) measuring the intensity of light of a predetermined wavelength reflected from said tube;
- (d) concurrently with measuring reflected light, translating said optical probe along the length of the tube from a starting position to an ending position, returning the probe to its original position, rotating the tube by a predetermined distance, and repeating this translation and rotation cycle until the tube has been rotated at least 360.degree.;
- (e) identifying peaks in the measured intensity of reflected light, and correlating these peaks to their longitudinal position on the tube, so that there is a first peak and a last peak on each longitudinal traversal of the tube;
- (f) computing the thickness of the deposit at each of said peaks in a longitudinal traversal of the tube, thereby generating the deposit thickness profile for a longitudinal traversal of the tube;
- (g) computing from said deposit thickness profile the deposit volume for a longitudinal traversal of the tube;
- (h) summing the deposit volumes for the longitudinal traversals of tube, thereby calculating the total deposit volume on the tube.
Dependencies are inferred from the claim text.