Numerical and Experimental Investigation of Secondary Flows and Influence of Air System Design on Heavy-Duty Gas Turbine Performance

Bozzi, Luca; D’Angelo, Enrico

doi:10.1115/gt2012-68392

Cited by 3 publications

(8 citation statements)

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“…The DP definition has been derived from several sources and checked for consistency. The final outcome is combined from [2], [12], [13]. Regarding the compressor and turbine characteristics, generic maps published in [14] have been applied.…”

Section: Performance Synthesis Model Definitionmentioning

confidence: 99%

“…The relative secondary air flows w SAS,rel are derived from air flow charts, tables and diagrams presented in [2], [12], [13]. Each individual flow's relative participation on rotor work is respected according to the already introduced work split assessed from [7], [9].…”

Section: Performance Synthesis Model Definitionmentioning

confidence: 99%

“…The geometry of the SAS network model has been derived from various drawings of the Ansaldo F-class AEx4.3A turbine published in [2], [16], [17], scaled to the overall Siemens SGT5-4000F layout originally accessed in [18]. All depicted SAS flow elements have been measured with a graph data extraction tool.…”

Section: Sas Network Model Definitionmentioning

confidence: 99%

“…The transformation of static bleed pressures is based on the compressor interstage characteristic presented in [2], which also includes a correction for cold and warm day conditions. For bleed temperatures, a compressor interstage characteristic has been generated, derived from the assumption of a constant stage enthalpy ∆h t,st over the compressor.…”

Section: Transformation Of Sas Boundary Conditionsmentioning

confidence: 99%

“…Despite of that, gas turbines will remain vital in the future to cover energy spikes. This implies changed requirements for gas turbines regarding part load operation: high flexibility in ramp-up and turndown process, increased cycle amount at part load at sufficient thermal efficiency η th and matching of legal requirements in terms of CO and NOx emissions [1], [2]. The design of the SAS providing cooling air to the combustor and turbine blades has an impact on all Figure 1.…”

Section: Introduction and Objectivementioning

confidence: 99%

See 4 more Smart Citations

Studies on Part Load Controlled Cooling Air Supplies in Stationary Gas Turbines

Woelki¹,

Peitsch²,

Foret³

et al. 2019

Proceedings of Global Power &Amp; Propulsion Society

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The design of new stationary gas turbines and development of upgrades for existing respectively is facing challenges regarding part load operation. The demands for high overall efficiency and compliance with legal requirements depend on the design of cooling air circuits among others. The design of an optimized secondary air distribution at both base load and part load as well as the consideration of different ambient conditions requires conceptual studies and hence appropriate models. This paper introduces the holistic model of a literature based generic stationary gas turbine, which essentially couples a gas turbine performance synthesis model with a more detailed secondary air system (SAS) network model. Extended with additional models such as evaluation of blade and vane material temperatures T mat , it allows for comparative off design studies with uncontrolled and controlled turbine cooling air circuits. The presented studies here first focus on margins of T mat with base load condition as benchmark. The subsequent exploitation of these margins is limited by the fundamental requirements of hot gas ingestion at common rim seal configurations. Either way, the reduction of cooling air at part load is beneficial in terms of fuel flow reduction: vane cooling air control results in up to 0.12% of fuel flow reduction at part load operation.

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Section: Performance Synthesis Model Definitionmentioning

confidence: 99%

Section: Performance Synthesis Model Definitionmentioning

confidence: 99%

Section: Sas Network Model Definitionmentioning

confidence: 99%

Section: Transformation Of Sas Boundary Conditionsmentioning

confidence: 99%

Section: Introduction and Objectivementioning

confidence: 99%

See 3 more Smart Citations

Studies on Part Load Controlled Cooling Air Supplies in Stationary Gas Turbines

Woelki¹,

Peitsch²,

Foret³

et al. 2019

Proceedings of Global Power &Amp; Propulsion Society

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An Integrated Approach to Simulate Gas Turbine Secondary Air System

Izadi¹,

Hosseini²,

Madani³

et al. 2021

Preprint

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One of the most critical parts of a modern gas turbine that its reliability and performance has a great influence on cycle efficiency is the secondary air system (SAS). Modern systems functions to supply not only cooling airflow for turbine blades and vanes but sealing flow for bearing chambers and turbine segments as well as turbine disks' purge flow in order to eliminate hot gas ingestion. Due to the various interactions between SAS and main gas, consideration of the former is substantially crucial in design and analysis of the whole engine. Geometrical complexities and centrifugal effects of rotating blades and disks, however, make the flow field and heat transfer of the problem so complicated AND too computationally costly to be simulated utilizing full 3-D CFD methods. Therefore, developing 1-D and 0-D tools applying network methods are of great interests.The present article describes a modular SAS analysis tool that is consisted of a network of elements and nodes. Each flow branch of a whole engine SAS network is substituted with an element and then, various branches (elements) intersect with each other just at their end nodes. These elements which might include some typical components such as labyrinth seals, orifices, stationary/rotating pipes, pre-swirls, and rim-seals, are generally articulated with characteristic curves that are extracted from high fidelity CFD modeling using commercial software such as Flowmaster or ANSYS-CFX. Having these curves, an algorithm is developed to calculate flow parameters at nodes with the aid of iterative methods.The procedure is based on three main innovative ideas. The first one is related to the network construction by defining a connectivity matrix which could be applied to any arbitrary network such as hydraulic or lubrication networks. In the second one, off-design SAS calculation will be proposed by introducing some SAS elements that their characteristic non-dimensional curves are influenced by their inlet total pressure. The last novelty is the integration of the blades coolant calculation process that incorporates external heat transfer calculation, structural conduction and coolant side modelling with SAS network simulation. Finally, SAS simulation of an industrial gas turbine is presented to illustrate the capabilities of the presented tool in design point and off-design conditions. NOMENCLATURE𝐶𝐶 𝑝𝑝 Specific heat capacity at constant pressure [kJ/kg℃] 𝐻𝐻 Specific Enthalpy [kJ/kg] ℎ 𝑐𝑐 Coolant heat transfer coefficient [W/m 2 K] 𝐾𝐾 Flow function = ṁ/Δp, Thermal conductivity ṁ Mass Flow Rate [kg/s] 𝑁𝑁 Gas turbine rotational speed [𝑟𝑟𝑟𝑟𝑟𝑟] 𝑃𝑃 Pressure [Pa] 𝑃𝑃𝑟𝑟 Pressure Ratio = P o, Out /P o, In Q ̇ Heat Flux [W/m^2] 𝑇𝑇 Temperature [K] 𝜂𝜂 Cooling efficiency 𝜀𝜀 Cooling effectiveness 𝛽𝛽 Non-dimensional coolant mass flow parameter Subscripts: 𝑏𝑏 Blade, vane or metal 𝑐𝑐, 𝑐𝑐𝑐𝑐 Coolant, Coolant side 𝐶𝐶𝐶𝐶/ 𝐶𝐶𝐶𝐶 Coolant Inlet/ Coolant Outlet 𝐺𝐺 Gas side

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Trade-Off Assessments for Part Load Controlled Cooling Air in Stationary Gas Turbines

Woelki

Peitsch

2020

Volume 5: Controls, Diagnostics, and Instrumentation; Cycle Innovations; Cycle Innovations: Energy Storage

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The demand for flexible operation of stationary gas turbines, especially at part load, requires the simultaneous design for sufficient efficiency and life time. Both can be addressed by the secondary air system. The here applied concept modulates cooling air supply in off-design. Typically, a reduction of cooling air leads to higher efficiency but shorter turbine life time. This paper presents investigations on such concepts, aiming for trade-offs between fuel burn and turbine blade life. The considered life time mechanisms are creep, which is dominant in rotor blades, and oxidation. In addition, the effects on emissions from the combustion are outlined. The reference gas turbine is a literature-based, generic gas turbine in the 300 MWpower output segment. Regarding cooling air control, the focus is on the first two stages of the four-stage turbine. All simulations are performed by application of component zooming with an appropriate in-house tool: a previously introduced coupled model of the reference gas turbine that essentially connects gas turbine performance with a secondary air system network model. This coupled model is now extended with blade life evaluation and emission models. The results contain trade-offs for different operating points at base and part load. For example, the combined cooling air control of stage 1 rotor blade and stage 2 vane offers several benefits regarding fuel consumption: saving up to Δwfuel,rel = 0.5% in the heat recovery’s kink point operation at 60 % of base load of a combined cycle application. This saving is at the expense of creep life. However, some operating points could even operate at higher blade temperatures in order to improve life regarding hot corrosion. Furthermore, generic sensitivities of controlled secondary air supply to cooling layers and hot gas ingestion at rim seals are discussed. Overall, the presented trades mark promising potentials of modulated secondary air system concepts from a technical point of view.

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Numerical and Experimental Investigation of Secondary Flows and Influence of Air System Design on Heavy-Duty Gas Turbine Performance

Cited by 3 publications

References 0 publications

Studies on Part Load Controlled Cooling Air Supplies in Stationary Gas Turbines

Studies on Part Load Controlled Cooling Air Supplies in Stationary Gas Turbines

An Integrated Approach to Simulate Gas Turbine Secondary Air System

Trade-Off Assessments for Part Load Controlled Cooling Air in Stationary Gas Turbines

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