LEAKLAB · TECHNICAL INSIGHTS
A sealed recirculating tunnel combines independent circulation and evacuation with optical particle tracking.
RU2861230C1 · National Research University MPEI · published 29 April 2026 · granted patent.
Separate circulation from evacuation
A fan circulates air around a closed tunnel, while a vacuum pump removes gas from the sealed volume. The test section, curved sections, return ducts and fan chamber form a loop. A sealed loading cover and removable flanges provide specimen access. A valve connects the pump and an electronic pressure instrument monitors the operating conditions.
Optical diagnostics
Aerosol tracer particles are illuminated in a plane formed by a continuous laser and cylindrical lens. A high-speed camera records successive images through a window. Cross-correlation processing estimates motion from particle displacement over a known interval. In the authors’ tests, averaging across image series helped compensate for limited particle counts.
A honeycomb upstream of the test section reduces transverse motion, but does not guarantee laminar flow for every specimen and operating condition.
Published parameters and their limits
The description gives observed-particle velocities of 0.1–20 m/s and an example laser wavelength of 450–480 nm. Its wording “vacuum from 0 to 60 kPa” must not be converted into an absolute-pressure range of 0–60 kPa or a claim of high vacuum. Absolute pressure and the indication convention need separate definition.
Quantitative work also requires image calibration, frame timing, optical-distortion assessment, sufficient tracers and pressure stability. Particle inertia and time averaging can affect the measured field.