Heavy Duty Gas Turbine Research Articles

IFCN-BIASN Based Built-In Test Signal State Recognition for Heavy-Duty Gas Turbine Controller

IFCN-BIASN Based Built-In Test Signal State Recognition for Heavy-Duty Gas Turbine Controller

Transformation of film cooling performance with evolution of vortex structure for coolant jet with various swirl intensities

Advanced H/J series heavy-duty gas turbines are widely equipped with film cooling to protect turbine blades. Previous studies have shown that coolant swirl has an important influence on film cooling performance. However, there are few studies on the quantitative analysis of the coolant swirl intensity because of the swirl generated by the specific structure, and most of the research was carried out at relatively low temperatures. In this paper, a new method of defining the velocity field in the coolant inlet is used to quantitatively investigate the coolant swirl intensity. A numerical study of the film cooling performance for the coolant jet with various swirl intensities is conducted in the operating conditions of H series turbine vanes. The effects of the blowing ratio and coolant vorticity on the vortex structure and mixing process of the flow field are investigated emphatically, and the mechanisms for the variation of the film cooling effectiveness are analyzed. The results show that the film cooling effectiveness is greatly improved with the swirling coolant jet at high blowing ratios. When Ωn=40,000 /s, the area-averaged (L = 5D) film cooling effectiveness is 54 % higher than the non-swirling case. Ωn=20,000 /s is a critical value of the coolant vorticity. When Ωn>20,000 /s, the film coverage transforms significantly. Furthermore, the main vortical structures in a typical SJICF flow field with high blowing ratios and large vorticities are proposed. Compared with the non-swirling JICF, the additional coolant vortex and induced vortex appear in the SJICF. Under the influence of the two vortices, the coolant momentum is sacrificed for enhanced attachment to the wall resulting in the momentum advantage gradually transforming into the effectiveness advantage with the increase of the vorticity.

Turn-Down Capability of Ansaldo Energia's AE94.3A

Abstract At an ever-faster pace, market's requirements for operational flexibility and turn-down capabilities are fundamental for heavy-duty gas turbines. Gas turbine energy plants require the lowest minimum environmental load (MEL) for times when the power request is mainly covered by renewable sources and, however, need to promptly respond to green energy shortages. Ansaldo Energia has addressed such requirements overall its gas turbine portfolio, recently including GT26, as discussed in GT2021-59457. This paper addresses the MEL reduction for AE94.3A via a modular upgrade package intended for the 110+ units Service fleet. To accomplish that, several features were designed and tested including variable inlet guide vanes (VIGV) extra-closure, air bypass through compressor blow-off lines, and extended use of anti-ice air recirculation. None of these require major hardware changes but only upgrades within a normal service outage, together with minor control system adaptations. The wide-ranging technical challenges attached to the MEL reduction features are discussed. Validation on field via special instrumentation focused on compressor, secondary air system (SAS), and turbine for several engines is also presented. The achieved minimum environmental load reduction is shown and its potential discussed together with some features already in place, such as the use of CO catalyzer or the regulation of control valves put on external cooling lines. The readiness and performance level of this MEL upgrade package, already in operation on several power plants, is here demonstrated. This makes the AE94.3A gas turbine more flexible toward current and future market requirements.

Influence of the turbulence model on the numerical predictions of cold turbulent flow in a heavy-duty gas turbine DLN combustor

The influence of different turbulence models on the numerical predictions of cold turbulent flow in a 300 MW F-class DLN combustor was investigated in this study. PIV and PLIF test data were obtained and used for comparison. The simulation results obtained using the LES method exhibited a high level of agreement with the experimental results regarding the velocity distribution and recirculation zone scale. Of the RANS models, only the results from the RNG k-ε and Realizable k-ε are comparable to the experimental data and are suitable for rapid simulation of the combustor flow field. Conversely, the Standard k-ε, SST k-ω, and RSM model results display notable differences from the experiment. Regarding the mixing simulation in the combustor, the LES method was the closest to the experiment. The RANS models roughly reflect the same mixing trend as the experiment, despite the tracer gas diffusing much slower than in the experiment.

Evaluation of Nox Emissions Associated to Non-Premixed Combustion of H2/Natural Gas Blends in a 40 MW Heavy-Duty Gas Turbine

Abstract The tightening in the international regulations is leading the energy production sector toward the usage of hydrogen, which is a zero-carbon energy carrier. In the field of gas turbine lifetime extension, a nonpremixed approach including hydrogen blending with conventional fuels is the most promising. However, high-temperature spots might occur, thus increasing thermo-mechanical stresses and NOx emissions. Therefore, a reliable evaluation of the impact of hydrogen blends in combustors characterized by nonpremixed flames is necessary. In the present work, a 40 MW heavy-duty multican combustor belonging to EthosEnergy is investigated by means of steady, reactive simulations by using the ANSYS® FLUENT® solver. The combustor geometry is simplified by removing the casing volume, being the flow split among the holes already available. Such simplification allows for paying major attention to the chemical kinetics thanks to the use of the extended reaction mechanism for natural gas developed by National University of Ireland Galway. Simulations include the assessment of the natural gas base load configuration together with hydrogen blends up to 50% in volume, while maintaining unaltered the turbine inlet temperature (TIT). The obtained data provide some retrofitting guidelines in the field of hydrogen usage in nonpremixed combustion and prove for a modified temperature field in the combustor core and close to the basket. A linear increase in NOx emission is also associated with hydrogen addition, thus suggesting the need for NOx abatement technologies (e.g., water injection).

Dynamic process simulation of a 780 MW combined cycle power plant during shutdown procedure

The share of variable renewables in power generation is increasing due to the push to reduce emissions, and the flexibility of conventional power plants has become a major concern. There are many ways to increase the flexibility of existing power plants and implement a more flexible system for the future, such as a fast start-up procedure and higher load change rates. In this study, a 2D dynamic process simulation model of a reference combined cycle power plant is presented to increase the flexibility of cyclic operation by investigating, for the first time in the literature, the shutdown procedure using APROS software. The 780 MWel Tambak Lorok reference combined cycle power plant consists of the GE 9HA.02 heavy-duty gas turbine and a three-stage horizontal heat recovery steam generator with reheat. Several steps were considered to improve the accuracy of the developed dynamic process simulation model, including varying the steam leakage to the atmosphere to control how much thermal energy remains in the heat recovery steam generator, changing the shape loss coefficients of the tubes to achieve higher or lower recirculation, and decoupling the reheater and the intermediate pressure drum. The developed model is validated with real data from three different combined cycle power plants in different countries with various capacities. The comparison shows that the developed dynamic simulation model can accurately represent the real behaviour of natural convection in the heat recovery steam generator. The main outcome was to provide detailed information on the shutdown procedure of large-scale combined cycle power plants, addressing the aspect of the development of new start-up strategies to reduce the time required for the start-up procedure.

High precision thickness evaluation of thermal barrier coating with high frequency eddy current testing method

Consisting of a top ceramic coating (TC) and a bond coating (BC) layer, thermal barrier coating (TBC) is a key component of the heavy duty gas turbine blade to protect the substrate material from high working temperature. Thinning of the top coating and the thermally grown oxide (TGO) layer formed between TC and BC cause TBC thickness reduction, and may significantly affect the in-service performance of TBC. High frequency eddy current testing (HF ECT) is considered as an efficient technique for nondestructive evaluation (NDE) of the TBC thickness, but its measurement accuracy is not satisfied up to now. Aiming to realize a high precision TBC thickness evaluation with HF ECT signals, a numerical method for simulating HF ECT of TBC was developed and implemented with consideration of the dielectric properties of TC and TGO material. Through numerical simulations with the developed code, an ECT probe of optimized configuration and robust against lift-off variation was designed and fabricated for the TBC thickness evaluation. A HF ECT measurement system is then setup to investigate the validity of the prototype ECT probe and sizing method experimentally. It was found that the thickness of the TC layer can be evaluated within 10 μm accuracy for the plate TBC specimens, which reveals the HF ECT method and new ECT probe are efficient for NDE of the TBC thickness.

Comparison of model-driven soft measurement methods for compressor air flow in gas-steam combined cycle power units

The determination of the air flowrate at the compressor inlet is meaningful for the performance diagnosis of heavy-duty gas turbine combined cycle (GTCC) power units, whereas the compressor air flow generally cannot be directly obtained from the field data. In this paper, the procedures of three model-driven methods for soft measurement of compressor air flow were presented, including energy balance of the coupled HRSG (M1), static pressure at the compressor manifold (M2) and gas turbine joint operation line method (M3). In the case of a M701F4 GTCC power unit, the methods M1 and M3 were validated by the field and testing data; while the method M2 was calibrated and the effective area at the air manifold was decided as 12.606 m2 using M1 at the full load of gas turbine. The compressor air mass flow at overall loads was computed with the various methods. The comparative investigation to these methods shows that, the compressor inlet air flow is determined as 682.75 kg/s by M1 and 664.07 kg/s by M3, respectively, at the full load and at the ambient temperature 29.912 °C. The air flow obtained by M1 and M2 appears relatively higher than that by M3 at typical various loads of gas turbine; however, the method M3 shows a good accordance with the actual value of the air flow for turbine rotor cooling. Both M2 and M3 agree in the theoretical demonstration that compressor air flow is strongly related to the gas turbine load at certain conditions. The method M1 can be deemed as a reference for another two methods in the case of the steady operating state at full load; whereas it is not recommendable for the real-time measurement of compressor air flow, because of the large amounts of required input variables and the fluctuation in the flow meters.

Physics Informed Machine Learning Approach for Performance Degradation Monitoring of Gas Turbine

The heavy-duty gas turbine is playing an increasingly significant role on power generation due to its lower-emission, higher flexibility and thermo-efficiency. Main subsystems of the gas turbine like compressor, combustor and turbine degrade over the operating time under the harsh environmental conditions, which largely impacts the efficiency and productivity of the system. Therefore, it is critical to develop effective approaches to monitor performance degradation of a heavy-duty gas turbine for system predictive maintenance thus improving the efficiency and productivity of the machine. This paper presents a new physics informed machine learning methodology to predict the degradation of gas turbine by seamlessly integrating thermodynamic heat balancing mechanism, component characteristics, multi-source data and artificial neural network model. The mechanism-based thermodynamic model is established for multiple subsystems considering the balance of flow, mass and energy, and then integrated to a system level for performance simulation of the gas turbine under different conditions. The system model is able to effectively simulate values for those parameters that are not measurable (e.g. GT exhaust flow) or inaccurately measured (e.g. fuel flow). Machine learning based data cleaning approach is employed to preprocess the multivariate raw data of the gas turbine. The difference between design performance data and corrected value obtained from the physics-informed model under ISO conditions is utilized to assess the performance degradation. A Long Short-Term Memory (LSTM) model is established from the fusion of the actual and simulation data to predict the performance degradation of the gas turbine. A comparison study with the classical Nonlinear Autoregressive Network with External Input (NARX) neural network is conducted to demonstrate the advantage of the proposed method. Key Word: Gas Turbine, Thermodynamic Balance, Performance Degradation Predict, Machine Learning, LSTM

Natural gas-hydrogen hybrid combustion retrofit method and practice for F-class heavy-duty combustion engines

In order to reduce carbon emissions, enhance the operational flexibility of gas turbine power plants, and fill the gap in practical engineering transformation of natural gas-hydrogen blended combustion in heavy-duty gas turbines, a hydrogen blending retrofit was conducted on an F-class heavy-duty gas turbine combined heat and power unit. This served to examine the problems of combustion chamber tempering, combustion pulsation, and NOx emission increase caused by direct hydrogen-doped combustion in the combustion chamber. In this paper, the gas turbine body and hydrogen mixing system were reformed respectively. Retrofit schemes were proposed that were suitable for two operating conditions: 5%–15% and 15%–30% hydrogen blending. Experimental tests were conducted as a means of evaluating the performance of the retrofitted gas turbine and its compatibility with the boiler and steam turbine. The results of the retrofit showed there to be stable combustion, and there was no significant increase in average burner temperatures or occurrence of flashback. The gas turbine power output mostly remained unchanged and NOx emissions met the regulatory standards. The waste heat boiler flue gas temperature was controlled within the range of 84.9–88.2 °C, meaning that the safe operation of the steam turbine was not affected. The hydrogen blending rate was 0.2 Vol%/s, which indicates a smooth and precise control of the hydrogen blending process. It was estimated that the annual reduction in CO2 emissions would be 11,000 tons and 28,400 tons following respective hydrogen blending at 15% and 30%. A reliable retrofit scheme for hydrogen blending in gas turbines based on practical engineering transformation is presented in this study, which has significant reference value.

Prediction model of NOx emissions in the heavy-duty gas turbine combustor based on MILD combustion

A prediction model of NOx emissions in heavy-duty gas turbine combustors based on the moderate and intense low-oxygen dilution (MILD) combustion was proposed, and the inlet parameter sensitivity analysis was also investigated to identify the impact weight for the practical operation of heavy-duty gas turbines. The optimal space-filling (OSF) design was first adopted to determine the optimal combination of gas temperature (Tgas), primary air temperature (Tfirst), secondary air temperature (Tsecondary), gas mass flow (mgas), primary air mass flow (mfirst), and secondary air mass flow (msecondary) for minimum NOx emissions. Based on the results of the OSF design, the minimum NOx emissions of 24.11 mg/m3 were obtained, and the corresponding Tgas, Tfirst, Tsecondary, mgas, mfirst, and msecondary were 769.67 K, 825.10 K, 722.61 K, 1.71 kg/s, 4.29 kg/s, and 7.69 kg/s within the range of 10% fluctuation of rated input parameters. The sensitivity ranking of the six inlet parameters was secondly achieved as mfirst > Tfirst > Tsecondary > msecondary > mgas > Tgas with the base of NOx emissions. Finally, a novel prediction model with six inlet parameters was established to quickly and accurately calculate the NOx emissions influenced by complicated boundary conditions in MILD combustion of heavy-duty gas turbines.

Dynamic scaling design strategy of discontinuous bolted rotor systems based on bidirectional parameter mapping

Rods fastened rotor system are widely used in heavy-duty gas turbines. The contact nonlinearity and discontinuity induced by bolted rotor structures, make it difficult to design a scaled rotor system accurately. Thus, a dynamic scaling design strategy for discontinuous bolted rotor systems is proposed in this paper. An improved continuous modeling method considering rods deformation based on equivalent material layer (EML) is introduced to reflect the weakening effect of the rotor stiffness with bolted structure, and the parameter mapping relationships between the continuous and the discontinuous structure are constructed. The scaling factors of each element of the rotor system are derived by the similarity theory. Through this approach, a discontinuous rotor system can be scaled, demonstrating a high level of consistency with the prototype in terms of natural frequencies, critical speeds as well as frequency response. In addition, modal experiments under different preloads and dynamic acceleration experiment are carried out to verify of the proposed modeling method for discontinuous rotor structures. The testing and simulation results prove that the introduced equivalent material layer reflects the contact effect of prototype accurately. Compared with the experimental results, the maximum deviation of the first two natural frequencies is 4.06%, and the maximum deviation of the critical speeds is 1.36%, demonstrating the potential of small size, low-cost scaled models for predicting the complex dynamic characteristics of the prototype rotor system. Overall, the proposed scaling design strategy provides practical guidance for the design and manufacture of the discontinuous scaled rotor systems, which has broad application in testing, fault prediction and dynamic design of prototypes.

Multidimensional analysis and performance prediction of heavy-duty gas turbine based on actual operational data

This study aims to analyze and predict the degradation, safety and operational performance of a heavy-duty gas turbine based on actual operational data after running for a long time. The dataset consists of 288,039 operational records from the Ban Shan Power Plant. The data is screened using Pearson correlation coefficients and 2-means clustering. Then, efficiency degradation of compressor and gas turbine is conducted by decoupling operation state from degradation. Next, Long short-term memory(LSTM) is employed to build data-driven T-model based on algorithm structure similarity. Meanwhile, the safety requirements containing the compressor surge and turbine inlet temperature boundary are determined, which are considered in operational performance analysis. Results show that abnormal operation data is identified during operational times 37, 38, 39, 40, 41, 42, and 248. After 254,341 minutes, the compressor efficiency degrades nearly 1%. The surge margin of a compressor is a binary function of the corrected air mass flow and inlet guide vane (IGV). The pressure ratio of the working margin moves downward by 0.11 for each 1° increase in IGV. What’s more, the T-model demonstrates high accuracy and can predict operational performance at high environmental temperatures, with the accuracy of turbine outlet temperature within 0.995. The unit is particularly sensitive to IGV, natural gas flow mass, compressor inlet temperature, and turbine outlet gauge pressure. When the relative humidity is 68%, the electrical power is the highest and overall efficiency is the best. Overall, this study's approach has significant potential for multidimensional analysis and performance prediction.

Intelligent fuzzy modeling of heavy-duty gas turbine for smart power generation

Intelligent fuzzy modeling of heavy-duty gas turbine for smart power generation

Mode shape-dependent thermoacoustic interactions between a lean-premixed primary flame and an axially-staged transverse reacting jet

Axial fuel staging enables elevation of the turbine inlet temperature in advanced heavy-duty gas turbine combustors to ∼2000 K, ultimately to achieve more than 65% combined cycle efficiency, while limiting excessive nitrogen oxide production. While previous investigations have identified transverse jet-flow-dependent nitrogen oxides emission trends and the topological properties of reacting shear layers in vitiated crossflow environments, there exists a critical gap in the understanding of axial-fuel-staging-induced combustion instabilities. The present study therefore investigates the link between first- and second-stage flame dynamics in a lean-premixed combustor. We demonstrate that the second-stage jet-in-vitiated-crossflow flame is preferentially coupled to higher order acoustic modes than the upstream primary flame with the same characteristic nozzle dimension. The first- and second-stage-driven acoustic modes (two different timescales) are mutually incompatible, and the ensuing selective excitation is critically dependent on the position of the secondary injector relative to the mode shape. When the second-stage flame is located near a pressure node, or a velocity antinode, the transverse jet-stabilized flame is influenced by the primary flame-driven crossflow velocity oscillations, and exhibits conspicuous flapping motions in the crossflow direction accompanied by periodic partial extinction at the windward and leeward-side flame elements. If the second-stage flame is situated near a pressure antinode, on the other hand, the secondary jet flame's dynamics are governed by a combination of jet merging-induced flame surface destruction and the growth of non-axisymmetric coherent structures. In this case, high-intensity pressure oscillations are sustained by the local heat release fluctuations generated solely from the transverse reacting jets, whereas the upstream primary flame remains nearly unperturbed, or decoupled from the underlying feedback processes. This experimental observation is remarkable, and reflects previously unknown properties originating from the complex interactions between the two axially-staged lean-premixed flames.

Numerical Study on Vibration Response of Compressor Stator Blade Considering Contact Friction of Holding Ring

There are many kinds of assembly structures in heavy-duty gas turbine compressor stator blades which have significant influence on the complex damping vibration characteristics. At present, compressor design is becoming more and more compact, so it is very meaningful to accurately obtain stator blade vibration characteristics of structures with contact damping. Firstly, a fretting slip friction dynamic model was introduced, and then a vibration analysis model of the compressor stator blade with outer ring structure was established based on the slip friction theory. Then, the vibration response of the compressor stator blade was obtained according to various working conditions, and the main factors affecting the vibration characteristics of the stator blade were revealed. Finally, the vibration response of the blade under a particular exciting force condition was simulated. The results show that the damping vibration characteristics of the compressor stator blades were affected by the excitation force and the normal load of the contact surface. The vibration response curve of the stator blade and the equivalent stiffness coefficient of the contact surface were analyzed, and the friction motion of the contact surface changed with the change of the working condition. The model can simulate the nonlinear vibration characteristics of stator blades. This method provides a reference for the vibration safety analysis of compressor stator blades.

The Fuel Flexibility of Gas Turbines: A Review and Retrospective Outlook

Land-based gas turbines (GTs) are continuous-flow engines that run with permanent flames once started and at stationary pressure, temperature, and flows at stabilized load. Combustors operate without any moving parts and their substantial air excess enables complete combustion. These features provide significant space for designing efficient and versatile combustion systems. In particular, as heavy-duty gas turbines have moderate compression ratios and ample stall margins, they can burn not only high- and medium-BTU fuels but also low-BTU ones. As a result, these machines have gained remarkable fuel flexibility. Dry Low Emissions combustors, which were initially confined to burning standard natural gas, have been gradually adapted to an increasing number of alternative gaseous fuels. The paper first delivers essential technical considerations that underlie this important fuel portfolio. It then reviews the spectrum of alternative GT fuels which currently extends from lean gases (coal bed, coke oven, blast furnace gases…) to rich refinery streams (LPG, olefins) and from volatile liquids (naphtha) to heavy hydrocarbons. This “fuel diet” also includes biogenic products (biogas, biodiesel, and ethanol) and especially blended and pure hydrogen, the fuel of the future. The paper also outlines how, historically, land-based GTs have gradually gained new fuel territories thanks to continuous engineering work, lab testing, experience extrapolation, and validation on the field.

Liquation Cracking in Row 3 Twin Turbine Vane Segment Caused by Malfunctioning Plasma Coating Gun

Abstract Transverse through-wall airfoil cracking was found in a row 3 twin turbine vane segment of a type used in heavy-duty gas turbine engines for power generation. A laboratory investigation determined liquation cracking (LC), a hot cracking mechanism, as the metallurgical cause of failure. As became apparent only after the investigation, the root cause of failure was a malfunctioning plasma gun used for thermal spraying the thermal barrier ceramic top coat onto the subject part.

Study on the acoustic characteristics of a heavy-duty gas turbine combustor

The acoustic characteristics of combustor are an important theoretical basis for determining whether a gas turbine will undergo thermoacoustic coupled oscillatory combustion. In this paper, the acoustic numerical model of a heavy-duty gas turbine combustor is established and its acoustic characteristics are studied using ANSYS simulation software. The results show that: 1) the acoustic pressure oscillation in the chamber primarily appears as the longitudinal mode below 705 Hz, while above 870 Hz, the transverse mode appears. 2) the effect of temperature on the acoustic natural frequency of the chamber enhances with the order of the acoustic mode. 3) the acoustic frequency of each order of the combustor varies considerably at low load conditions, and no longer varies when the gas turbine load is higher than 80 % rated power. 4) the variation of acoustic frequency with gas turbine load can be fitted by a third-order polynomial, and the acoustic frequency is proportional to the first and third orders.

Effects of Hydrogen/Methane on the Thermal Environment of Heavy-Duty Gas Turbine Combustor

Hydrogen is the most promising fuel for reducing carbon emissions, but hydrogen combustion produces higher temperature compared to hydrocarbon fuel. In this paper, a three-dimensional compressible combustion–flow–heat transfer model of combustor was established, and a dry-low-emission combustor was examined by using the realizable model, transported probability density function, and discrete ordinates model combining weighted sum of gray gas model, analyzing the effects of hydrogen/methane blended fuel and thermal boundaries on the combustor thermal environment. The results show that when the fuel hydrogen volume percentage increases from 0 to 75%, the maximum gas temperature and concentration on the central axis of the combustor increase by about 160.8 and 662.9%, respectively; the maximum incident radiant heat flux of the combustor wall increases by about 150%; and the local maximum ratio of the radiant heat transfer to the total heat transfer through the wall increases from about 34 to about 49%. The effect of the boundary conditions varies depending on the hydrogen percentage. At the hydrogen percentage of 75%, the maximum wall-incident radiant heat flux under the adiabatic condition is nearly 180.3 and 77.4% higher than the values at 1370 and 1920 K isothermal boundaries, respectively.