Patent ID: 7265832
Filing Date: 2007-09-04
Classification: G01F,G01N,G01P

Abstract:
1. An apparatus for measuring the velocity of particles carried by a fluid, flowing through a pipe, comprising: (a) at least one light source and means for generating two separate beams of light; (b) a first transparent optical window in the pipe wall that contains the fluid flow within the pipe and allows the beams of light to enter the inside pipe volume; (c) an optical delivery system, having an optical axis, which directs said two beams of light through said first optical window, so that the beams form two focal spots inside the pipe, aligned approximately at the same position within the pipe cross-section but at different points along the pipe axis with a known separation between them; (d) a second transparent optical window in the pipe wall, disposed approximately on the opposite side of the pipe wall to the first optical window, that contains the fluid flow within the pipe and allows light to exit the inside pipe volume; (e) at least one measuring light detector means for detecting light scattered by particles carried by the fluid, and converting the time varying detected light amplitude to a corresponding measuring electronic signal; (f) an optical collection system, having an optical axis that is approximately collinear with the optical axis of said optical delivery system, that collects light scattered by particles carried in the fluid flow within a first solid angle subtended from said focal spots, and focuses said scattered light on to said measuring light detector means; (g) an opaque obscuration to absorb unscattered light, disposed approximately on the optical axis after said focal spots, said obscuration subtending a second solid angle from said focal spots, which is smaller than said first solid angle so that said scattered light that passes through the unobscured portion of said first solid angle, reaches the measuring light detector means; and (h) an electronic processing means that receives said measuring electronic signals detected by the light detector means, wherein said measuring electronic signals are processed to determine the time of flight delay of particles passing through the two focal spots, and further means for calculating the particle velocity or fluid flow rate.