Heavy Duty Gas Turbine Research Articles

Fretting Fatigue Cracking of an Arresting Feature in a Turbine Disk of a Heavy-Duty Gas Turbine Engine

Abstract A check for surface cracks under application of the magnetic flux leakage method (MT testing) was performed on the turbine wheel disk of a heavy-duty turbine gas turbine engine for energy generation. It revealed unacceptable findings on the bearing surface of the sealing plate groove. In order to identify the damage-causing mechanism of the material, a metallographic examination was performed. The findings during non-destructive material testing were caused by a gaping material separation which was also easily detectable to the naked eye. The material separation is a high-cycle fatigue crack induced by fretting. Hence, the damage causing mechanism was fretting fatigue cracking.

The effects of internal leakage on the performance of a micro gas turbine

Micro gas turbines are manufactured to have a compact structure and small volume, which makes them more vulnerable to internal leakages compared to heavy-duty gas turbines. Accordingly, precise diagnosis of the performance degradation in a micro gas turbine is important. This study investigates the characteristics of degradation. Performance maps were used for the compressor and turbine, and a multi-segment counter-flow heat exchanger model was used for the recuperator. The component models were refined using actual operation data, resulting in precise simulation of the reference operation without leakage. A performance analysis was carried out, and the results were analyzed for three types of leakage with the following paths: from the compressor outlet to the recuperator’s cold-side outlet, from the compressor outlet to the combustor outlet, and from the combustor inlet to the turbine outlet. The third path produced the largest reduction in engine efficiency. The degradations were also compared with those related to compressor fouling and turbine erosion, which are the most common causes of degradation in a gas turbine. Even when qualitatively similar performance changes were observed, the root cause could be determined by analyzing differences in performance parameters such as the fuel flow.

Pressure gain combustion advantage in land-based electric power generation

AbstractThis article evaluates the improvement in gas turbine combined cycle power plant efficiency and output via pressure gain combustion (PGC). Ideal and real cycle calculations are provided for a rigorous assessment of PGC variants (e.g., detonation and deflagration) in a realistic power plant framework with advanced heavy-duty industrial gas turbines. It is shown that PGC is the single-most potent knob available to the designers for a quantum leap in combined cycle performance.

Research on Creep Relaxation Non-uniformity and Effect on Performance of Combined Rotor

The combined rotor of gas turbine is connected by a certain number of rod bolts. It works in the high temperature environment for a long time, and the rod bolts will creep and relax. Under the influence of elastic interaction, the loss of pretightening force of rod bolts at different positions is non-uniform, which will cause the connection of the combined rotor to be out of tune. In this paper, the creep relaxation non-uniformity model for a class F heavy duty gas turbine is established. On the basis of this, the performance degradation and structural strength change of combined rotor resulting from creep relaxation non-uniformity of rod bolts are studied. The results show that the ratio of preload mistuning increases with time and then converges, and there is a threshold inflection point in about seven thousand hours.

Heavy duty gas turbine monitoring based on adaptive neuro-fuzzy inference system: speed and exhaust temperature control

Gas turbines are currently a popular power generation technology in countries with access to natural gas resources. However they are very complex systems the operation of which at peak performance is challenging. This paper proposes the use of a hybrid approach based on an Adaptive Neuro-Fuzzy Inference System (ANFIS) for the control of the speed and the exhaust temperature of a gas turbine. The main aim is to maintain turbine operation at optimum performance. The results obtained, based on the use of the Rowen model, clearly show the effectiveness of the proposed hybrid speed/exhaust temperature control approach for the gas turbine.

Multi-objective optimization of IGV position in a heavy-duty gas turbine on part-load performance

More than 60% of the power generated in Iran depends on the technical characteristics of heavy-duty gas turbine power plants. The ability to make changes in the amount of compressor air flow via positioning Inlet Guide Vanes (IGV) has been considered to improve the techno-economic quality of the mentioned gas turbine power in different operational conditions. In this study, system modeling was conducted based on operational data, using the outputs of the industrial code developed in various conditions. This model was derived via thermodynamic equations and linear regression functions. Subsequently, multi-objective genetic algorithm optimization of IGV position was employed to optimize the objective functions in the power generation range of 40%–100% (nominal) load. Thermal efficiency and electricity generation cost, which cover the main decision factors in energy management systems in Iran, were selected as the objective functions.

Analysis of the natural acoustic modes of a gas turbine combustor using isothermal CFD simulations

Thermoacoustic instabilities usually result from the coupling between the oscillatory heat release and one or more natural acoustic modes of the combustion system. When the shifting of system frequencies caused by the unsteady heat release is limited, the calculation of natural modes allows to identify which of them are excited by the flame once changes in flow temperature and composition due to combustion are considered.In this paper, isothermal computational fluid dynamics simulations are performed to predict the natural modes of a heavy-duty gas turbine combustor in reactive conditions. Combustion and heat transfer are neglected in the numerical analysis to simplify the model and limit the computational effort. The natural frequencies resulting from isothermal simulations are then corrected using a rather basic post-processing approach to account for temperature and gas composition changes due to combustion process. Frequency and amplitude of the calculated modes are finally compared to experimental measurements to evaluate the ability of the acoustic analysis to capture frequency and spatial shape of the combustor natural modes excited by the flame.

Full annulus numerical study of hot streaks propagation in a hydrogen-rich syngas-fired heavy duty axial turbine

This paper presents a study of the effect of fuel composition on hot streaks propagation in a high-pressure turbine using a full annulus unsteady computational fluid dynamics analysis of the first two stages. Hot streaks result from the inherent non-uniformities of temperature profiles at the exit of the combustion chamber. Variations in composition arise from current challenges requiring gas turbines to adapt to fuel variations driven by the need to reduce CO2 emissions through the use of synthetic hydrogen-rich fuels (syngas) typically generated from the gasification of coal or solid waste. Syngas containing 80% hydrogen has been used in this study in a heavy duty gas turbine modified to accommodate the low calorific value fuel. Calculations were conducted on the baseline gas turbine originally designed for natural gas for the comparative study. Applying combustor representative hot streak profiles, analyses were performed for different hot streak distributions and locations. Analysis of results focused on the segregation of cold and hot fluid patterns and the effects of hot streaks on secondary flows and temperature re-distributions up to the second turbine stage. The hot flow pattern is affected by the fuel composition, resulting in more concentrated thermal wake shapes for syngas when compared to the reference natural gas fuel. In effect, the interaction with the secondary flow leads to more intense flow turning of the pressure side leg of the horseshoe vortex in the first rotor passage. The higher temperature levels in the case of syngas, in combination with the effect of the enhanced secondary flow, result in higher radial spread of the hot fluid that tends to migrate towards the blade hub and tip with the effects being obvious further downstream the first turbine stage.

Influence of the upstream slot geometry on the endwall cooling and phantom cooling of vane suction side surface

Modern gas turbines always operate at a high level of inlet temperature. The current inlet temperature in the aircraft and heavy duty gas turbines is higher than the melting point of the guide vane material. Consequently, advanced cooling schemes must be developed to ensure the safe operation of gas turbines. In the current study, numerical simulations were conducted to investigate the influence of the upstream slot geometry on the endwall cooling and phantom cooling of the vane suction side surface. Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations combined with the shear stress transport (SST) k-ω turbulence model were solved to conduct the simulations based on the validated turbulence model. The results indicate that the adiabatic cooling effectiveness in the upstream region of the stagnation is significantly increased by introducing the contoured upstream slot. However, the normal upstream slot obtains a relatively high adiabatic cooling effectiveness level in the downstream region of the stagnation. In the present research, the case with normalized amplitude A‾=0.75, initial phase angle φ=45° achieves the largest overall adiabatic cooling effectiveness near the vane leading edge. In contrast, the case with A‾=0.75, φ=30° attains the smallest overall adiabatic cooling effectiveness on the endwall surface. Moreover, the phantom cooling effectiveness on the vane suction side surface is relatively small relative to the adiabatic cooling effectiveness on the endwall. The case with the normal upstream slot achieves the largest phantom cooling effectiveness on the vane suction side surface compared with the contoured upstream slot. Overall, the contoured upstream slot significantly enhances the endwall cooling effectiveness by rearranging the distribution of the coolant mass flowrate at the slot outlet.

Development of Advanced Thermal Barrier Coatings With Improved Temperature Capability

Continuously increasing hot gas temperatures in heavy duty gas turbines lead to increased thermal loadings of the hot gas path materials. Thermal barrier coatings (TBCs) are used to reduce the superalloys temperature and cooling air needs. Until now 6–8 wt. % yttria stabilized zirconia (YSZ) is the first choice material for such coatings, but it is slowly reaching its maximum temperature capability due to the phase transformation at high temperature and sintering. New thermal barrier coating material with increased temperature capability enables the next generation of gas turbine with >60% combined cycle efficiency. Such material solutions have been developed through a multistage selection process. In a first step, critical material performance requirements for thermal barrier coating performance have been defined based on the understanding of standard TBC degradation mechanisms. Based on these requirements, more than 30 materials were a preselected and evaluated as potential coating materials. After carefully reviewing their properties both from literature data and laboratory test results on raw materials, five materials were selected for coating manufacturing and laboratory testing. Based on the coating manufacturing trials and laboratory test results, two materials have been selected for engine testing, in a first step in GT26 Birr Test Power Plant and afterward in customer engines. For such tests, the original coating thickness has been increased such to achieve coating surface temperature ∼100 K higher than with a standard thermal barrier coating. Both coatings performed as predicted in both GT26 Birr Test Power Plant and customer engines.

Investigation of a pure hydrogen fueled gas turbine burner

Hydrogen can represent an option for a low emission gas turbine if low NOx combustion systems are developed. This paper describes the design and the investigations carried out on a lean premixed burner 100% hydrogen supplied. An existing heavy-duty gas turbine burner was modified with a new axial swirler and a co-flow injection system. The designed prototype presents the interesting feature where the variable premixing level permits a wide-ranging case studying. The burner prototype was investigated during a test campaign performed on an atmospheric test rig. Flame control on burner prototype, fired by pure hydrogen, was achieved by managing the premixing degree and the flow velocity. NOx emissions, flash-back limit, and burner pressure drop were measured over a wide range of the main operating parameters: equivalence ratio, premixer discharge velocity and thermal input. Results of the measurements outline as higher velocity flow (depending on the burner arrangements and operating conditions) is necessary to avoid flame positioning inside the premixer duct when hydrogen is used. The best arrangement can limit the NOx emissions to 17 ppm but with an outlet velocity about 120 m/s. The numerical activity integrates the information on the flame shape, and it improves the knowledge of the NOx emissions and their chemical path. Anyway, the study confirmed the operability of the system and great perspective regarding NOx emission containment.

Temperature Calculation in an Uncooled Low-pressure Stage of a Heavy-duty Gas Turbine Using Conjugate Heat Transfer Analysis

Temperature Calculation in an Uncooled Low-pressure Stage of a Heavy-duty Gas Turbine Using Conjugate Heat Transfer Analysis

A neuro-fuzzy controller for grid-connected heavy-duty gas turbine power plants

A neuro-fuzzy controller for grid-connected heavy-duty gas turbine power plants

Development of a program for transient behavior simulation of heavy-duty gas turbines

In this study, a program for analyzing the transient behaviors of heavy-duty gas turbines was developed. Focus was given to simulating a practical load-following operation. A distinct feature of our work is that all of the gas turbine components are modularized to enhance the expandability of the program. We used object-oriented programing for this purpose. Mass and energy balances and performance maps for the compressor and turbine were used for the modeling, and a multivariable numerical solving technique was used to enhance the numerical stability. The fundamental thermodynamic modeling of the program was validated by comparison of the transient response of a simulated gas turbine with that of a commercial program. PID control was adopted for simultaneous control of the rotational shaft speed and turbine exhaust temperature by the modulations of the fuel flow and the opening of the compressor inlet guide vane at the same time. The influence of the magnitude of load change and ramp rate was investigated. Stable control of the gas turbine was possible, even for a very rapid change of load.

Aerothermal Performance of a Nozzle Vane Cascade With a Generic Nonuniform Inlet Flow Condition—Part I: Influence of Nonuniformity Location

In this paper, the modifications induced by the presence of an inlet flow nonuniformity on the aerodynamic performance of a nozzle vane cascade are experimentally assessed. Tests were carried out in a six vane linear cascade whose profile is typical of a first stage nozzle guide vane of a modern heavy-duty gas turbine. An obstruction was located in the wind tunnel inlet section to produce a nonuniform flow upstream of the leading edge plane. The cascade was tested in an atmospheric wind tunnel at an inlet Mach number Ma1 = 0.12, with a high turbulence intensity (Tu1 = 9%) and variable obstruction tangential and axial positions, as well as tangential extension. The presented results show that an inlet flow nonuniformity influences the stagnation point position when it faces the vane leading edge from the suction side. A relevant increase of both 2D and secondary losses is observed when the nonuniformity is aligned to the vane leading edge. When it is instead located in between the passage, it does not affect the stagnation point location, in the meanwhile allowing a reduction in the secondary loss.

Techno-Economic Analysis of CAES Systems Integrated into Gas-Steam Combined Plants

In the present paper, an energy storage concept based on the integration of a Compressed Air Energy Storage system into a Gas Steam Combined Cycle plants is investigated. The integration of CAES results in a noticeable power augmentation in respect to normal GSCC plant operations. Being such a power increase obtained without using additional fuel, the storage system can be compared to PHS, BES and A-CAES. Two CAES integrated into medium size GSCC plants arranged with Aero Derivative and Heavy Duty Gas Turbines have been investigated. A techno economic analysis aimed at assessing plant performance and investment costs has been performed. Despite the relatively high investment costs and the storage efficiency lesser than those featuring alternative storage approaches, the proposed system may be considered of interest due to the long life duration and the established technologies available for the key plant components.

Effects of Upgraded Cooling System and New Blade Materials on a Real Gas Turbine Performance

Abstract The aim of this paper is to study the effects on the performance of a real heavy-duty gas turbine of two different solutions for enhancing turbine blades thermal resistance. An upgrade of the first stator cooling system and the adoption of improved blade materials are simulated exploiting an in-house simulation tool (ESMS). The changes are studied separately in order to point out the positive effects as well as the related risks, such as the side effect of temperature increase on downstream blade rows, to be considered in service operations.

Enhancing Turbine Performance Degradation Prediction with Atmospheric Factors

Heavy duty gas turbine engines are not only ingesting the air, but also eating a myriad of aerosol particles, which may have various negative effects on the turbine operation efficiency as well as the component failure. This paper attempts to develop predictive degradation models for gas turbines by integrating satellite collected atmospheric factors, on-site monitoring data, and physics-based calculated performance results. Multiple variables are analyzed and employed for predictive modeling. The vital variables are identified by using data exploratory correlation analysis and stepwise regression analysis. The performance degradation calculation is obtained from physics based thermodynamic heat balance of gas turbine. It requires balancing mass and energy of gas turbine to match measurement data through thermodynamic cycle matching. The performance degradation prior to the offline water wash is used as the predictor. Artificial neural network modeling is employed to establish the predictive models. A procedure is presented to explain the proposed methodology, and results are discussed. This paper provides an effective methodology and procedure to apply big data for the performance degradation prediction of gas turbines.

Mathematical Model and Control Design of Micro Turbine Generation System

In this modern era power generation seems to be a very demanding factor. New models and methods have been proposed to derive from various natural and man made resources. In such instances this paper gives a detailed report on the power generation from micro turbines. To enlist the microturbines as a prime source of energy utility restructuring, technology evolution, public environmental policy and expanding power demand are some of the most notable factors. Gas turbines plays a very important role in electric power generation. Especially they are used in the Combined cycle process power Plants. The parameters of Rowen’s model 265-MW single shaft heavy duty gas turbines which are used in dynamic studies are estimated in this paper using the operational and performance data. These data are also used to briefly explain the extraction of parameters of the used model. Gas turbine parameters are approximated using simple thermodynamics assumptions. Though micro turbine power generation seems to be an uprising and a promising source, the exact design with a perfect model is only capable of producing the highest efficiency. Thus this paper is proposed on the aspects of social awareness to elaborate a mathematical model and a control design of the Micro Turbine Power Generation System.

Film Cooling Modeling for Gas Turbine Nozzles and Blades: Validation and Application

The design of modern gas turbines cooling systems cannot be separated from the use of computational fluid dynamics (CFD) and the accurate estimation of the effect of film cooling. Nevertheless, a complete modeling of film cooling holes within the computational domain requires an effort both from the point of view of the mesh creation and from computational time. It is here proposed a new way to model the film cooling (FCM), capable of representing the effect of the coolant at hole exit. This is possible due to the introduction of local source terms near the hole exit in a delimited portion of the domain, avoiding the meshing process of perforations. The goal is to provide a reliable and accurate tool to simulate film-cooled turbine blades and nozzles without having to explicitly mesh the holes. The model was subjected to an intensive validation campaign, composed of two phases. During the first one, FCM results are compared to experimental data and numerical results (obtained with complete cooling holes meshing) on a series of test cases reproducing flat plate cooling configurations for different coolant conditions (in terms of blowing and density ratio). In the second phase, a film-cooled vane test case has been studied, in order to consider a real injection system and flow conditions: FCM predictions are compared to an in-house developed correlative approach and full conjugate heat transfer (CHT) results. Finally, a comparison between FCM predictions and experimental data was performed on an actual nozzle of a GE Oil & Gas heavy-duty gas turbine, in order to prove the feasibility of the procedure. The presented film cooling model (FCM) proved to be a feasible and reliable tool, able to evaluate adiabatic effectiveness, simplifying the design phase avoiding the meshing process of perforations.