# US 2022/0034696 A1 · Method and device for measuring a flow velocity of a gas stream > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0034696 A1 - Document ID: US20220034696A1 - Status: Published application - Kind: A1 - Application number: 17/278,937 - Filed: 2019-09-24 - Published: 2022-02-03 - Earliest claimed: 2018-09-24 - Assignees: PROMECON process measurement control GmbH - Applicants: Promecon Process Measurement Control GmbH - Inventors: Hans-Georg CONRADS - Web page: https://patentgrep.com/patent/US20220034696A1 ## CPC - G01F 1/7086: using optical detecting arrangements - G01F 1/704: using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter (G01F1/76, G01F25/00 take precedence) - G01F 1/7044: {using thermal tracers} - G01P 5/22: using auto-correlation or cross-correlation detection means - G01F 1/712: using auto-correlation or cross-correlation detection means - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) ## Abstract The invention relates to a method for measuring a flow velocity (v) of a gas stream (14) featuring the steps: (a) time-resolved measurement of an IR radiation parameter (E) of IR radiation of the gas stream (14) at a first measurement point (P1) outside of the gas stream (14), thereby obtaining a first IR radiation parameter curve (Eg1,1(t)), (b)time-resolved measurement of an IR radiation parameter (E) at a second measurement point (P2) outside of the gas stream (14), thereby obtaining a second IR radiation parameter curve (Eg1,2(t)), (c) calculation of a transit time (τ1) from the first IR radiation parameter curve (Eg1,1(t)) and the second IR radiation parameter curve (Eg1,2(t)), in particular by means of cross-correlation, and (d) calculation of the flow velocity (vG) from the transit time (τ1), (e) wherein the IR radiation parameter (Eg1) is measured photoelectrically at a wavelength (g1) of at least 780 nm, and (f) a measurement frequency (f) is at least 1 kilohertz. ## Claims ### Claim 1 A method for measuring a flow velocity of a gas stream, comprising: (a) time-resolved measurement of an IR radiation parameter of IR radiation of the gas stream at a first measurement point outside of the gas stream, thereby obtaining a first IR radiation parameter curve, (b) time-resolved measurement of the IR radiation parameter at a second measurement point outside of the gas stream, thereby obtaining a second IR radiation parameter curve, (c) calculation of a transit time from the first IR radiation parameter curve and the second IR radiation parameter curve, and (d) calculation of a the flow velocity from the transit time, (e) wherein the IR radiation parameter is measured photoelectrically at a wavelength of at least 780 nm, and (f) a measurement frequency is at least 1 kilohertz. ### Claim 2 (depends on 1) The method according to claim 1, wherein characterised in that (i) the gas stream is a stream of a gas mixture that contains a first gas and at least a second gas, (ii) the first gas has a first gas excitation wavelength and (iii) the IR radiation parameter is an irradiance at the first gas excitation wavelength. ### Claim 3 (depends on 2) The method according to claim 2, wherein (i) the second gas has a second gas excitation wavelength and (ii) the method further comprises the following steps: (a) time-resolved detection of a second IR radiation parameter in a form of an irradiance at the second gas excitation wavelength at the first measurement point, thereby obtaining a first irradiance curve, (b) time-resolved detection of the second IR radiation parameter at the second measurement point, thereby obtaining a second irradiance curve, (c) calculation of a second transit time between the first and second irradiance curves, and (d) calculation of the flow velocity from the first transit time and the second transit time. ### Claim 4 (depends on 3) The method according to claim 3Error! Reference source not found., further comprising: filtering out of IR radiation of the gas stream that does not lie within a predetermined first measurement interval of 0.3 μm around the first gas excitation wavelength or a predetermined second measurement interval of 0.3 μm around the second gas excitation wavelength. ### Claim 5 (depends on 1) The method according to claim 1 wherein the IR radiation parameter is measured at a wavelength of at most 15 μm. ### Claim 6 (depends on 1) The method according to claim 1 wherein a temperature of the gas stream is at least 200° C. ### Claim 7 A device for measuring a flow velocity of a gas stream, comprising: (a) a first IR radiation sensor for the time-resolved measurement of a first IR radiation parameter of IR radiation of the gas stream to obtain a first IR radiation parameter curve, (b) a second IR radiation sensor for the time-resolved measurement of the first IR radiation parameter of IR radiation of the gas stream to obtain a second IR radiation parameter curve, and (c) an evaluation unit designed to automatically calculate a transit time between the first IR radiation parameter curve and the second IR radiation parameter curve, and calculate a flow velocity from the transit time, (d) wherein the IR radiation sensors are photoelectric IR radiation sensors and have a measurement range with a lower cut-off wavelength that is at least 0.78 μm and have a measurement frequency of at least 1 kilohertz. ### Claim 8 (depends on 7) The device according to claim 7, wherein the measurement range has an upper cut-off wavelength that is at most 15 μm. ### Claim 9 (depends on 1, 7) The device according to claim 7, wherein the evaluation unit is configured to automatically conduct a method according to claim 1. ### Claim 10 (depends on 7) The device according to claim 7, further comprising (a) a pipe for conducting the gas stream, wherein the first IR radiation sensor and the second IR radiation sensor are arranged to detect IR radiation from the pipe, or (b) an outflow or through-flow opening, wherein the first IR radiation sensor and the second IR radiation sensor are arranged to detect IR radiation of the gas stream flowing out of the outflow opening.