Details
| Original language | English |
|---|---|
| Title of host publication | Turbomachinery |
| Publisher | American Society of Mechanical Engineers(ASME) |
| ISBN (electronic) | 9780791856635, 9780791856635 |
| Publication status | Published - 12 Aug 2015 |
| Event | ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, GT 2015 - Montreal, Canada Duration: 15 Jun 2015 → 19 Jun 2015 |
Publication series
| Name | Proceedings of the ASME Turbo Expo |
|---|---|
| Volume | 2A |
Abstract
Exhaust diffusers downstream of turbines are used to transform the kinetic energy of the flow into static pressure. The static pressure at the turbine outlet is thus decreased by the diffuser, which in turn increases the technical work as well as the efficiency of the turbine significantly. Consequently, diffuser designs aim to achieve high pressure recovery at a wide range of operating points. Current diffuser design is based on conservative design charts, developed for laminar, uniform, axial flow. However, several previous investigations have shown that the aerodynamic loading and the pressure recovery of diffusers can be increased significantly if the turbine outflow is taken into consideration. Although it is known that the turbine outflow can reduce boundary layer separations in the diffuser, less information is available regarding the physical mechanisms that are responsible for the stabilization of the diffuser flow. An analysis using the Lumley invariance charts shows that high pressure recovery is only achieved for those operating points in which the near-shroud turbulence structure is axi-symmetric with a major radial turbulent transport component. This turbulent transport originates mainly from the wake and the tip vortices of the upstream rotor. These structures energize the boundary layer and thus suppress separation. A logarithmic function is shown that correlates empirically the pressure recovery vs. the relevant Reynolds stresses. The present results suggest that an improved prediction of diffuser performance requires modeling approaches that account for the anisotropy of turbulence.
Keywords
- Boundary layer, Correlation, Diffuser, Hot-wire, Rotating wakes, Separation, Vortex
ASJC Scopus subject areas
- Engineering(all)
- General Engineering
Cite this
- Standard
- Harvard
- Apa
- Vancouver
- BibTeX
- RIS
Turbomachinery. American Society of Mechanical Engineers(ASME), 2015. (Proceedings of the ASME Turbo Expo; Vol. 2A).
Research output: Chapter in book/report/conference proceeding › Conference contribution › Research › peer review
}
TY - GEN
T1 - Influence of Turbulent Flow Characteristics and Coherent Vortices on the Pressure Recovery of Annular Diffusers: Part A
T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition, GT 2015
AU - Kuschel, Marcus
AU - Drechsel, Bastian
AU - Kluß, David
AU - Seume, Joerg R.
PY - 2015/8/12
Y1 - 2015/8/12
N2 - Exhaust diffusers downstream of turbines are used to transform the kinetic energy of the flow into static pressure. The static pressure at the turbine outlet is thus decreased by the diffuser, which in turn increases the technical work as well as the efficiency of the turbine significantly. Consequently, diffuser designs aim to achieve high pressure recovery at a wide range of operating points. Current diffuser design is based on conservative design charts, developed for laminar, uniform, axial flow. However, several previous investigations have shown that the aerodynamic loading and the pressure recovery of diffusers can be increased significantly if the turbine outflow is taken into consideration. Although it is known that the turbine outflow can reduce boundary layer separations in the diffuser, less information is available regarding the physical mechanisms that are responsible for the stabilization of the diffuser flow. An analysis using the Lumley invariance charts shows that high pressure recovery is only achieved for those operating points in which the near-shroud turbulence structure is axi-symmetric with a major radial turbulent transport component. This turbulent transport originates mainly from the wake and the tip vortices of the upstream rotor. These structures energize the boundary layer and thus suppress separation. A logarithmic function is shown that correlates empirically the pressure recovery vs. the relevant Reynolds stresses. The present results suggest that an improved prediction of diffuser performance requires modeling approaches that account for the anisotropy of turbulence.
AB - Exhaust diffusers downstream of turbines are used to transform the kinetic energy of the flow into static pressure. The static pressure at the turbine outlet is thus decreased by the diffuser, which in turn increases the technical work as well as the efficiency of the turbine significantly. Consequently, diffuser designs aim to achieve high pressure recovery at a wide range of operating points. Current diffuser design is based on conservative design charts, developed for laminar, uniform, axial flow. However, several previous investigations have shown that the aerodynamic loading and the pressure recovery of diffusers can be increased significantly if the turbine outflow is taken into consideration. Although it is known that the turbine outflow can reduce boundary layer separations in the diffuser, less information is available regarding the physical mechanisms that are responsible for the stabilization of the diffuser flow. An analysis using the Lumley invariance charts shows that high pressure recovery is only achieved for those operating points in which the near-shroud turbulence structure is axi-symmetric with a major radial turbulent transport component. This turbulent transport originates mainly from the wake and the tip vortices of the upstream rotor. These structures energize the boundary layer and thus suppress separation. A logarithmic function is shown that correlates empirically the pressure recovery vs. the relevant Reynolds stresses. The present results suggest that an improved prediction of diffuser performance requires modeling approaches that account for the anisotropy of turbulence.
KW - Boundary layer
KW - Correlation
KW - Diffuser
KW - Hot-wire
KW - Rotating wakes
KW - Separation
KW - Vortex
UR - http://www.scopus.com/inward/record.url?scp=84954349182&partnerID=8YFLogxK
U2 - 10.1115/gt2015-42476
DO - 10.1115/gt2015-42476
M3 - Conference contribution
AN - SCOPUS:84954349182
T3 - Proceedings of the ASME Turbo Expo
BT - Turbomachinery
PB - American Society of Mechanical Engineers(ASME)
Y2 - 15 June 2015 through 19 June 2015
ER -