Flow Evolution Through a Turning Mid Turbine Frame With Embedded Design

Abstract

The paper discusses the time-averaged flow of a new concept turbine transition duct placed in a two-stage counter-rotating test turbine located at the Institute for Thermal Turbomachinery and Machine Dynamics of Graz University of Technology. As a possible architecture for the turbine transition duct of future engines, the structural vanes carrying the bearing loadings can be integrated with the first low pressure vane row in one aerodynamically optimized wide-chord vane. Such architecture is also called Turning Mid Turbine Frame (TMTF). In order to increase the flow uniformity and to decrease the unsteady content of the flow at the inlet of the LP rotor, a baseline TMTF was redesigned embedding two splitter vanes into the strut passage. The discussion on the flow field is based on numerical results obtained by a CFD code and validated by aerodynamic measurements. The flow structures moving from the outlet of the transonic high pressure stage are observed propagating towards the low pressure stage. In particular the splitter vanes are seen playing a major role in suppressing the big structures generated by the struts. On the other hand new losses are introduced by the splitter structures. Such structures play a decisive role in the overall component performance and therefore their effect should be properly understood in the design phase. This work provides a deep insight into the flow physics of TMTF designed with an embedded concept for next generation aero-engines. This configuration is seen to be a promising architecture in order to compact the engine size while keeping the components performance high.

Flow Evolution Through a Turning Midturbine Frame with Embedded Design

“…The verification of the simulation has been done with a comparison with the measurement results, as was shown by Bader et al [13].…”

“…Five-hole probe measurements performed downstream of this stage were presented by Spataro et al [11]. Bader et al [13] discussed the appearance of the rotor tip leakage vortex (TLV) and the rotor lower passage vortex (LPV) and upper passage vortex (UPV) (see Fig. 3).…”

“…Detailed information on the design of the two-spool test rig was given by Hubinka et al [15,16]. The main parameters of the HP stage and the LP stage (TMTF LP rotor) as well as the operating conditions can be found in [11,13].…”

“…Spataro et al already showed in steady [11] and unsteady [12] measurements the reduction of the nonuniformity of pressure fluctuations (reduced strut wakes and secondary vortices) of the embedded design. In addition to the measurements, steady [13] and unsteady [14] computational fluid dynamics (CFD) simulations have been performed at the Institute for Thermal Turbomachinery and Machine Dynamics to analyze the flow structures within the TMTF with the embedded design.…”

Influence of Wake Intensity on the Unsteady Flow Characteristics of the Integrated Aggressive Interturbine Duct

“…Therefore, Spataro [26] arranged two zero-loading splitter blades between adjacent wide-chord struts, effectively improving the uniformity of ITD outlet flow. Bader [27] and Faustmann [28] further indicated that a small splitter blade could break the large passage vortices in the passage of wide-chord struts into small passage vortices, thereby improving the outlet flow uniformity at the expense of increasing flow losses. Du [29], Wang [30], Liu [31], Xu [32] and Liu [33] carried out design and flow mechanism research of the integrated AITD and noted that the convergence passage of a wide-chord strut can effectively inhibit the threedimensional separation on the shroud and suppress the passage vortices around the blade tip by improving the radial and circumferential pressure gradient, which is conducive to reducing the flow loss in the AITD.…”