Abstract
Flow field in the inter-stage is of great importance to jet engine turbine performance and efficiency. Investigation of flow fields is limited by the complex geometrical structure. Traditional measurement techniques, such as hot wire, pressure probe and laser Doppler velocimetry (LDV) can hardly obtain a planar information of the flow field simultaneously. To overcome this difficulty, an instantaneous planar velocimetry technique, the particle image velocimetry (PIV) technique is widely employed. However, there is no publication that studied the detailed flow field by PIV in a turbine inter-stage with the consideration of the influence of rotor blade and purge flow. This paper presents a quasi-three dimensional perspective of flow field between inlet guide vane (IGV) and rotor blade in a research turbine inter-stage by using a 2D PIV system. Coherent structures in the flow field are extracted by the proper orthogonal decomposition (POD) method. Time-averaged results show the ellipsoid structures caused by secondary flow in the inter-stage. Rotor blade influence to axial and radial flow is evaluated by time-averaged data and the first order POD mode. Egress of purge flow (9.4% of main annulus flow rate) leads to a domain with 60% axial velocity loss near hub and a growth over three times in radial velocity. POD analysis of purge flow shows detailed flow migration in the whole measurement plane.
Highlights
The need for increasing turbine performance and efficiency has motivated the study of flow fields in turbomachinery
A detailed understanding of the complex flow field influenced by guide vane, rotor blade and purge flow is necessary
Combining the particle image velocimetry (PIV) measurement and proper orthogonal decomposition (POD) method, Lengani et al [39,40] characterized the dynamics of coherent structures on a turbine blade suction side boundary layer
Summary
The need for increasing turbine performance and efficiency has motivated the study of flow fields in turbomachinery. Combining the PIV measurement and POD method, Lengani et al [39,40] characterized the dynamics of coherent structures (the generation, propagation and breakdown of coherent structures) on a turbine blade suction side boundary layer. A further investigation of turbine inter-stage flow structure is necessary, especially with detailed information of the flow field. To the best of the present author’s knowledge, no publication studies the detailed flow structure by PIV in a main annulus of turbine inter-stage with the consideration of the impact of rotor blade and purge flow. A quasi-three dimensional perspective of time-averaged velocity field in the inter-stage and detailed coherent structure in the measurement plane downstream of vane trailing edge are presented and analyzed. Time-averaged velocity fields show the flow structures in the inter-stage and evaluate the blade influence and purge flow impact. Results in the investigation show detailed flow structure in the turbine inter-stage, which could promote a better understanding of the flow mechanism in the turbine inter-stage and help to improve the design of turbomachinery and the CFD verification
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