Abstract
The unsteady flow field downstream of axial‐flow turbine rotors at low Reynolds numbers was investigated experimentally using hot‐wire probes. Reynolds number, based on rotor exit velocity and rotor chord length Reout,RT, was varied from 3.2 × 104 to 12.8 × 104 at intervals of 1.0 × 104 by changing the flow velocity of the wind tunnel. The time‐averaged and time‐dependent distributions of velocity and turbulence intensity were analyzed to determine the effect of Reynolds number. The reduction of Reynolds number had a marked influence on the turbine flow field. The regions of high turbulence intensity due to the wake and the secondary vortices were increased dramatically with the decreasing Reynolds number. The periodic fluctuation of the flow due to rotor‐stator interaction also increased with the decreasing Reynolds number. The energy‐dissipation thickness of the rotor midspan wake at the low Reynolds number Reout,RT = 3.2 × 104 was 1.5 times larger than that at the high Reynolds number Reout,RT = 12.8 × 104. The curve of the −0.2 power of the Reynolds number agreed with the measured energy‐dissipation thickness at higher Reynolds numbers. However, the curve of the −0.4 power law fitted more closely than the curve of the −0.2 power law at lower Reynolds numbers below 6.4 × 104.
Highlights
With the new generation of small gas-turbine engines, low Reynolds number flows have become increasingly important
The Reynolds numbers of the turbine cascades of 300 kW industrial ceramic gas turbines (Arakawa et al [1]) are approximately 6 × 104 because of the increased viscosity caused by high turbine-inlet temperatures and the miniaturization of the cascade, considerably smaller than the Reynolds numbers of conventional gas turbines
At these low Reynolds numbers, the boundary layer is dominated by laminar flow and is susceptible to flow separation and strong secondary vortices that develop into increased loss, leading to reduced performance
Summary
With the new generation of small gas-turbine engines, low Reynolds number flows have become increasingly important. The Reynolds numbers of the turbine cascades of 300 kW industrial ceramic gas turbines (Arakawa et al [1]) are approximately 6 × 104 because of the increased viscosity caused by high turbine-inlet temperatures and the miniaturization of the cascade, considerably smaller than the Reynolds numbers of conventional gas turbines At these low Reynolds numbers, the boundary layer is dominated by laminar flow and is susceptible to flow separation and strong secondary vortices that develop into increased loss, leading to reduced performance. Small gas turbines for aircraft propulsion encounter the low Reynolds number problem at high altitudes where the air. Since there have been few reports on unsteady rotor flow at low Reynolds numbers, and no reliable computational analyses are available to compute low Reynolds number turbine flows (Halstead et al [18]), detailed experimental data will make a major important contribution to establishing theoretical studies
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
