	US 12,442,763 B2
	Method for detecting primary gas flows in flow chambers, use of a gas mixture therefor and gas mixture
Thomas Berg, Goettingen (DE)
Assigned to La Vision GmbH, Goettingen (DE)
Appl. No. 17/777,473
Filed by LaVision GmbH, Goettingen (DE)
PCT Filed Nov. 19, 2020, PCT No. PCT/EP2020/082737 § 371(c)(1), (2) Date May 17, 2022, PCT Pub. No. WO2021/099494, PCT Pub. Date May 27, 2021.
Claims priority of application No. 10 2019 131 328.7 (DE), filed on Nov. 20, 2019.
Prior Publication US 2022/0404277 A1, Dec. 22, 2022
Int. Cl. G01N 21/45 (2006.01); G02B 27/48 (2006.01); G02B 27/54 (2006.01); G01N 21/15 (2006.01)

CPC G01N 21/455 (2013.01) [G02B 27/48 (2013.01); G02B 27/54 (2013.01); G01N 2021/151 (2013.01)]

12 Claims

1. A method for detecting primary gas flows (18) in a flow chamber (10), the method comprising:

causing a primary gas (18) to flow in the flow chamber (10);

locally seeding the primary gas (18) with a gas mixture (34) including a seed gas that moves with the primary gas (18) and has a refractive index that can be distinguished from the primary gas (18);

carrying out an imaging detection using an image detector (28) and imaging optics (30) arranged in front of the image detector (28) for performing a background schlieren measurement method to detect a movement of the gas mix re (34) that e of the flow of the primary gas (18); and

the gas mixture (34) being composed in such a way that:

|m_P−Σ_i=1^Na_im_i|<2 g/mol,

and

|n′_P−Σ_i=1^Na_in′_i|>70,

where m_Pis the molar mass and n′_Pis the refractive index of the primary gas, m_iis the molar mass and n′_iis the refractive index of the i-th gas component of the seed gas, N is the number of gas components of the seed gas, and a_iis their respective relative mole fraction in the seed gas,

so that a co-movement of the gas mixture (34) with the primary gas (18) flowing at a flow velocity of 0.1 to 1.0 m/s takes place without relative movement.