A New Experimental Facility to Investigate Combustor-Turbine Interactions in Gas Turbines With Multiple Can Combustors

The flow at the combustor turbine interface of power generation gas turbines with can combustors is characterized by high and nonuniform turbulence levels, lengthscales, and residual swirl. These complexities have a significant impact on the first vanes aerothermal performance and lead to challenges for an effective turbine design. To date, this design philosophy mostly assumed steady flow and thus largely disregards the intrinsic unsteadiness. This paper investigates the steady and unsteady effects of the combustor flow with swirl on the turbines first vanes. Experimental measurements are conducted on a high-speed linear cascade that comprises two can combustors and four nozzle guide vanes (NGVs). The experimental results are supported by a large eddy simulation (LES) performed with the inhouse computational fluid dynamics (CFD) flow solver TBLOCK. The study reveals the highly unsteady nature of the flow in the first vane and its effect on the heat transfer. A persistent flow structure of concentrated vorticity is observed. It wraps around the unshielded vane's leading edge (LE) at midspan and periodically oscillates in spanwise direction due to the interaction of the residual low-pressure swirl core and the vane's potential field. Moreover, the transient behavior of the horseshoe-vortex system due to large fluctuations in incidence is demonstrated.

Section: Experimental Facilitymentioning

confidence: 99%

Section: Experimental Facilitymentioning

confidence: 99%

Section: Experimental Facilitymentioning

confidence: 99%

See 1 more Smart Citation

Investigation of Unsteady Flow Phenomena in First Vane Caused by Combustor Flow With Swirl

Jacobi

Mazzoni

Rosic

et al. 2017

Development and Aerothermal Investigation of Integrated Combustor Vane Concept

Jacobi

Rosic

2015

This paper presents the development and aerothermal investigation of the integrated combustor vane concept for power generation gas turbines with individual can combustors. In this novel concept, first introduced in 2010, the conventional nozzle guide vanes (NGVs) are removed and flow turning is achieved by vanes that extend the combustor walls. The concept was developed using the in-house computational fluid dyanamics (CFD) code TBLOCK. Aerothermal experiments were conducted using a modular high-speed linear cascade, designed to model the flow at the combustor–vane interface. The facility is comprised of two can combustor transition ducts and either four conventional vanes (CVs) or two integrated vanes (IVs). The experimental study validates the linear CFD simulations of the IV development. Annular full-stage CFD simulations, used to evaluate aerodynamics, heat transfer, and stage efficiency, confirm the trends of the linear numerical and experimental results, and thus demonstrate the concept's potential for real gas turbine applications. Results show a reduction of the total pressure loss coefficient at the exit of the stator vanes by more than 25% due to a reduction in profile and endwall loss. Combined with an improved rotor performance demonstrated by unsteady stage simulations, these aerodynamic benefits result in a gain in stage efficiency of above 1%. A distinct reduction in heat transfer coefficient (HTC) levels on vane surfaces, on the order of 25–50%, and endwalls is observed and attributed to an altered state of boundary layer (BL) thickness. The development of IV's endwall- and leading edge (LE)-cooling geometry shows a superior surface coverage of cooling effectiveness, and the cooling requirements for the first vane are expected to be halved. Moreover, by halving the number of vanes, simplifying the design and eliminating the need for vane LE film cooling, manufacturing and development costs can be significantly reduced.

Development and Application of a Concentration Probe for Mixing Flows Tracking in Turbomachinery Applications

Babazzi

Bacci

Picchi

et al. 2021

Modern gas turbines present important temperature distortions in the core-engine flowpath, mainly in the form of hot and cold streaks. As they highly influence turbines performance and lifetime, the precise knowledge of the thermal field evolution through the combustor and the high-pressure turbine is fundamental. The majority of past studies investigated streaks migrations directly examining the thermal field, while a limited amount of experimental work employed approaches based on the detection of tracer gases. The latter approach provides a more detailed evaluation of the evolution and mixing of the different flows. However, the slow time response due to the employment of sampling probes and gas analysers make the investigation extremely time consuming. In this study a commercial oxygen sensor element and its excitation/detection unit were integrated into a newly developed probe to carry out local tracer gas concentration measurements exploiting the fluorescence behaviour. The paper summarizes the probe development and calibration activities, with the characterization of its accuracy for different flow conditions. Finally, two probe applications are described: firstly the probe was used to detect tracer gas concentrations on a jet flow; afterwards it was traversed on the interface plane between a non-reactive, lean combustor simulator and the NGV cascade. The probe has proven to provide accurate and reliable measurements both from a quantitative and qualitative point of view even in highly 3D flow fields typical of gas turbines conditions.