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

2020 ◽  
Author(s):  
Dominik Woelki ◽  
Dieter Peitsch
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Coupled Model ◽  
Life Time ◽  
Part Load ◽  
Trade Offs ◽  
Air Supply ◽  
Air System ◽  
Secondary Air ◽  
Cooling Air

Abstract 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.

Tradeoff Assessments for Part Load Controlled Cooling Air in Stationary Gas Turbines

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Dominik Woelki ◽  
Dieter Peitsch
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Coupled Model ◽  
Combined Cycle ◽  
Controlled Cooling ◽  
Part Load ◽  
Air System ◽  
Secondary Air ◽  
Cooling Air ◽  
Operating Points

Abstract The demand for flexible part load operation of stationary gas turbines requires the simultaneous design for sufficient efficiency and lifetime. Both can be addressed by the secondary air system. This paper presents investigations on the concepts of cooling air reduction in off-design, aiming for tradeoffs between fuel burn and turbine blade life. The considered lifetime mechanisms are creep and oxidation. In addition, the effects on emissions from the combustion are outlined. The reference gas turbine is a generic gas turbine in the 300 MW power output segment. The focus is on the first two stages of the four-stage turbine. All simulations are performed by application of a coupled model 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 tradeoffs for operating points at base and part load. For example, the combined cooling air control of stage 1 rotor blade and stage 2 vane offers savings up to 0.5% fuel flow at 60% of base load in 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 are discussed. Overall, the presented trades mark promising potentials of modulated secondary air system concepts from a technical point of view.

scholarly journals Cooling and Sealing Air System in Industrial Gas Turbine Engines

1996 ◽  
Author(s):  
A. W. Reichert ◽  
M. Janssen
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Gas Turbines ◽  
State Of The Art ◽  
Cooling System ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Air System ◽  
Calculation System ◽  
Cooling Air

Siemens heavy duty Gas Turbines have been well known for their high power output combined with high efficiency and reliability for more than 3 decades. Offering state of the art technology at all times, the requirements concerning the cooling and sealing air system have increased with technological development over the years. In particular the increase of the turbine inlet temperature and reduced NOx requirements demand a highly efficient cooling and sealing air system. The new Vx4.3A family of Siemens gas turbines with ISO turbine inlet temperatures of 1190°C in the power range of 70 to 240 MW uses an effective film cooling technique for the turbine stages 1 and 2 to ensure the minimum cooling air requirement possible. In addition, the application of film cooling enables the cooling system to be simplified. For example, in the new gas turbine family no intercooler and no cooling air booster for the first turbine vane are needed. This paper deals with the internal air system of Siemens gas turbines which supplies cooling and sealing air. A general overview is given and some problems and their technical solutions are discussed. Furthermore a state of the art calculation system for the prediction of the thermodynamic states of the cooling and sealing air is introduced. The calculation system is based on the flow calculation package Flowmaster (Flowmaster International Ltd.), which has been modified for the requirements of the internal air system. The comparison of computational results with measurements give a good impression of the high accuracy of the calculation method used.

Managing Fuel Oil Nozzle Coking to Improve Gas Turbine Availability

2000 ◽  
Author(s):  
Leo R. Burgett ◽  
Tim Mercer
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Fuel Oil ◽  
Power Company ◽  
Ac Motor ◽  
Air System ◽  
Oil Residue ◽  
Cooling Air ◽  
Fuel Burner

Fuel oil nozzle coking has been a continuing problem for operators of gas turbine power plants. Over the years, several “solutions” to eliminate the coking of the fuel oil have been implemented to improve plant reliability and availability. When the fuel oil nozzle is “coked”, the startup and operation of the gas turbine are impaired and an unscheduled outage is needed to clean the fuel oil nozzle. In 1997, a project was initiated to investigate the coking problem as it affects the operation of the dual fuel burner of the ABB ALSTOM POWER Inc. GT11N1 single burner (SBK) gas turbine. The GT11N1 SBK fuel oil nozzle (see FIGURE 1) was failing to operate properly because of “coked” fuel oil residue on its internal components (stationary and moveable). ABB ALSTOM POWER Inc. teamed with Savannah Electric & Power Company and collected data that indicated adequate nozzle cooling air could reduce the rate of fuel oil coking. A nozzle cooling air system modification was installed on one of the ABB ALSTOM POWER Inc. 11N1 gas turbines at the Savannah Electric & Power Company McIntosh Power Plant. The modification included an AC motor driven air blower to provide cooling air to the fuel oil nozzle after shutdown of the gas turbine. Inspection of the components inside the fuel oil nozzle showed that very little fuel oil oxidation had occurred inside the nozzle during the three-month test period. By improving the fuel oil nozzle cooling air system, the coking problem can be better managed.

Analysis of Gas Turbine Rotating Cavities by an One-Dimensional Model

2009 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Luca Innocenti ◽  
Mirko Micio
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Design Tool ◽  
Operating Conditions ◽  
Outer Flow ◽  
One Dimensional ◽  
Wide Range ◽  
Air System ◽  
Secondary Air ◽  
Radial Outflow

Reliable design of secondary air system is one of the main tasks for the safety, unfailing and performance of gas turbine engines. To meet the increasing demands of gas turbines design, improved tools in prediction of the secondary air system behavior over a wide range of operating conditions are needed. A real gas turbine secondary air system includes several components, therefore its analysis is not carried out through a complete CFD approach. Usually, that predictions are performed using codes, based on simplified approach which allows to evaluate the flow characteristics in each branch of the air system requiring very poor computational resources and few calculation time. Generally the available simplified commercial packages allow to correctly solve only some of the components of a real air system and often the elements with a more complex flow structure cannot be studied; among such elements, the analysis of rotating cavities is very hard. This paper deals with a design-tool developed at the University of Florence for the simulation of rotating cavities. This simplified in-house code solves the governing equations for steady one-dimensional axysimmetric flow using experimental correlations both to incorporate flow phenomena caused by multidimensional effects, like heat transfer and flow field losses, and to evaluate the circumferential component of velocity. Although this calculation approach does not enable a correct modeling of the turbulent flow within a wheel space cavity, the authors tried to create an accurate model taking into account the effects of inner and outer flow extraction, rotor and stator drag, leakages, injection momentum and, finally, the shroud/rim seal effects on cavity ingestion. The simplified calculation tool was designed to simulate the flow in a rotating cavity with radial outflow both with a Batchelor and/or Stewartson flow structures. A primary 1D-code testing campaign is available in the literature [1]. In the present paper the authors develop, using CFD tools, reliable correlations for both stator and rotor friction coefficients and provide a full 1D-code validation comparing, due to lack of experimental data, the in house design-code predictions with those evaluated by CFD.

Heavy Duty Gas Turbine Simulation: Global Performances Estimation and Secondary Air System Modifications

2006 ◽  
Author(s):  
Carlo Carcasci ◽  
Bruno Facchini ◽  
Stefano Gori ◽  
Luca Bozzi ◽  
Stefano Traverso
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Energy System ◽  
Operating Conditions ◽  
Coupled Analysis ◽  
Ambient Conditions ◽  
Air System ◽  
Secondary Air ◽  
And Performance

This paper reviews a modular-structured program ESMS (Energy System Modular Simulation) for the simulation of air-cooled gas turbines cycles, including the calculation of the secondary air system. The program has been tested for the Ansaldo Energia gas turbine V94.3A, which is one of the more advanced models in the family Vx4.3A with a rated power of 270 MW. V94.3A cooling system has been modeled with SASAC (Secondary Air System Ansaldo Code), the Ansaldo code used to predict the structure of the flow through the internal air system. The objective of the work was to investigate the tuning of the analytical program on the basis of the data from design and performance codes in use at Ansaldo Energy Gas Turbine Department. The results, both at base load over different ambient conditions and in critical off-design operating points (full-speed-no-load and minimum-load), have been compared with APC (Ansaldo Performance Code) and confirmed by field data. The coupled analysis of cycle and cooling network shows interesting evaluations for components life estimation and reliability during off-design operating conditions.

Experimental and Numerical Analysis of the Flow Structure and Dust Separation Inside a Pre-Swirl Cooling Air System

2003 ◽  
Author(s):  
O. Schneider ◽  
H. J. Dohmen ◽  
F.-K. Benra ◽  
D. Brillert
Keyword(s):  
Numerical Analysis ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Flow Conditions ◽  
Test Rig ◽  
Complex Flow ◽  
Air System ◽  
Cooling Air

Improvements in efficiency and performance of gas turbines require a better understanding of the internal cooling air system which provides the turbine blades with cooling air. With the increase of cooling air passing through the internal air system, a greater amount of air borne particles is transported to the film cooling holes at the turbine blade surface. In spite of their small size, these holes are critical for blockage. Blockage of only a few holes could have harmful effects on the cooling film surrounding the blade. As a result, a reduced mean time between maintenance or even unexpected operation faults of the gas turbine during operation could occur. Experience showed a complex interaction of cooling air under different flow conditions and its particle load. To get more familiar with all these influences and the system itself, a test rig has been built. With this test rig, the behavior of particles in the internal cooling air system can be studied at realistic flow conditions compared to a modern, heavy duty gas turbine. It is possible to simulate different particle sizes and dust concentrations in the coolant air. The test rig has been designed to give information about the quantity of separated particles at various critical areas of the internal air system [1]. The operation of the test rig as well as analysis of particles in such a complex flow system bear many problems, addressed in previous papers [1,2,3]. New theoretical studies give new and more accurate results, compared to the measurements. Furthermore the inspection of the test rig showed dust deposits at unexpected positions of the flow path, which will be discussed by numerical analysis.

Particulate Monitor for Gas Turbine Cooling Air

2008 ◽  
Author(s):  
Richard H. Bunce ◽  
Francisco Dovali-Solis ◽  
Robert W. Baxter
Keyword(s):  
Gas Turbine ◽  
Monitoring System ◽  
Cooling System ◽  
Gas Turbine Engine ◽  
Minimum Size ◽  
Turbine Engine ◽  
Air System ◽  
Air Cooler ◽  
Secondary Air ◽  
Cooling Air

It is important to monitor the quality of the air used in the cooling system of a gas turbine engine. There can be many reasons that particulates smaller than the minimum size removed by typical engine air filters can enter the secondary air system piping in a gas turbine engine system. Siemens has developed a system that provide real time monitoring of particulate concentrations by adapting a commercial electrodynamic devise for use within the confines of the gas turbine secondary air system with provision for a grab sample option to collect samples for laboratory analysis. This on-line monitoring system is functional at typical engine cooling system piping operating pressure and temperature. The system is calibrated for detection of iron oxide particles in the 1 to 100 micrometer range at concentration of from 1 to 50 parts per million mass wet (ppmmw) The electro dynamic device is nominally operable at 800°C. The particulate monitoring system requires special mounting and antenna. This system may be adjusted for other materials, sizes and concentrations. The system and its developmental application are described. The system has been tested and test results are reviewed. The test application was the cooling air piping of a Siemens gas turbine engine. Multiple locations were monitored. The cooling system in this engine incorporates an air cooler and the particulate monitoring system was tested upstream and downstream of the air cooler for temperature contrast. The monitor itself is limited to the piping system and not the engine gas-path.

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

2012 ◽  
Author(s):  
Luca Bozzi ◽  
Enrico D’angelo
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Engine Performance ◽  
Combined Cycle ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Heavy Duty ◽  
Turbine Performance ◽  
Air System ◽  
Secondary Air

High turn-down operating of heavy-duty gas turbines in modern Combined Cycle Plants requires a highly efficient secondary air system to ensure the proper supply of cooling and sealing air. Thus, accurate performance prediction of secondary flows in the complete range of operating conditions is crucial. The paper gives an overview of the secondary air system of Ansaldo F-class AEx4.3A gas turbines. Focus of the work is a procedure to calculate the cooling flows, which allows investigating both the interaction between cooled rows and additional secondary flows (sealing and leakage air) and the influence on gas turbine performance. The procedure is based on a fluid-network solver modelling the engine secondary air system. Parametric curves implemented into the network model give the consumption of cooling air of blades and vanes. Performances of blade cooling systems based on different cooling technology are presented. Variations of secondary air flows in function of load and/or ambient conditions are discussed and justified. The effect of secondary air reduction is investigated in details showing the relationship between the position, along the gas path, of the upgrade and the increasing of engine performance. In particular, a section of the paper describes the application of a consistent and straightforward technique, based on an exergy analysis, to estimate the effect of major modifications to the air system on overall engine performance. A set of models for the different factors of cooling loss is presented and sample calculations are used to illustrate the splitting and magnitude of losses. Field data, referred to AE64.3A gas turbine, are used to calibrate the correlation method and to enhance the structure of the lumped-parameters network models.

A Contribution to the Abrasive Effect of Particles in a Gas Turbine Pre-Swirl Cooling Air System

2005 ◽  
Author(s):  
O. Schneider ◽  
F.-K. Benra ◽  
H. J. Dohmen ◽  
K. Jarzombek
Keyword(s):  
Gas Turbine ◽  
Flow Structure ◽  
Film Cooling ◽  
Gas Turbines ◽  
Test Rig ◽  
Critical Areas ◽  
Air System ◽  
Quantitative Results ◽  
Film Cooling Holes ◽  
Cooling Air

With the increase of cooling air passing through the internal air system of modern gas turbines, a greater number of airborne particles is transported to the film cooling holes in the turbine blade surface. In spite of their small size, these holes are critical for airflow and must be free of blockage. A test rig has been designed to study the quantity of separated particles at various critical areas of the internal air system. Former publications for this conference gave detailed insight into the test rig, the flow structure and the particle motion during separation. The process of separation generates abrasion on the rotating and stationary parts of the system. When considering service and maintenance or even unexpected operation faults of the gas turbine, it is important to know the location and abrasion rate of these critical areas. The flow structure within the pre-swirl cooling air system results in locally focused abrasion regions, which are investigated in this paper. New simulations, taking additional physical effects into account, are discussed in the paper. The simulation results are compared to results obtained by measurements and observations within the test rig. Qualitative and quantitative results show the ability to predict the quantity of abrasion during operation on various critical areas of the system.

An Efficient Procedure for the Analysis of Heavy Duty Gas Turbine Secondary Flows in Different Operating Conditions

2010 ◽  
Author(s):  
Matteo Cerutti ◽  
Luca Bozzi ◽  
Federico Bonzani ◽  
Carlo Carcasci
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Heavy Duty ◽  
Efficient Procedure ◽  
Air System ◽  
Secondary Air ◽  
Flow Functions

Combined cycle and partial load operating of modern heavy-duty gas turbines require highly efficient secondary air systems to supply both cooling and sealing air. Accurate performance predictions are then a fundamental demand over a wide range of operability. The paper describes the development of an efficient procedure for the investigation of gas turbine secondary flows, based on an in-house made fluid network solver, written in Matlab® environment. Fast network generation and debugging are achieved thanks to Simulink® graphical interface and modular structure, allowing predictions of the whole secondary air system. A crucial aspect of such an analysis is the calculation of blade and vane cooling flows, taking into account the interaction between inner and outer extraction lines. The problem is closed thanks to ad-hoc calculated transfer functions: cooling system performances and flow functions are solved in a pre-processing phase and results correlated to influencing parameters using Response Surface Methodology (RSM) and Design of Experiments (DOE) techniques. The procedure has been proved on the secondary air system of the AE94.3A2 Ansaldo Energia gas turbine. Flow functions for the cooling system of the first stage blade, calculated by RSM and DOE techniques, are presented. Flow functions based calculation of film cooling, tip cooling and trailing edge cooling air flows is described in details.

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