Heavy Duty Gas Turbine Research Articles

A technical-economic analysis of turbine inlet air cooling for a heavy duty gas turbine operating with blast-furnace gas

The study was developed inside an integrated steel mill, located in Rio de Janeiro city, aiming to analyse the technical-economic feasibility of installing a new inlet air refrigeration system for the gas turbines. The technologies applied for such purpose are named Turbine Inlet Air Cooling (TIAC) technologies. The power plant utilizes High Fogging and Evaporative Cooling methods for reducing the compressor’s inlet air temperature, however, the ambient climate condition hampers the turbine’s power output when considering its design operation values. Hence, this study was proposed to analyse the installation of an additional cooling system. The abovementioned power plant has two heavy-duty gas turbines and one steam turbine, connected in a combined cycle configuration. The cycle nominal power generation capacity is 450 MW with each of the gas turbines responsible for 90 MW. The gas turbines operate with steelwork gases, mainly blast furnace gas (BFG), and natural gas. The plant has its own weather station, which provided significant and precise data regarding the local climate conditions over the year of 2017. An in-house computer model was created to simulate the gas turbine power generation and fuel consumption considering both cases: with the proposed TIAC system and without it, allowing the evaluation of the power output increase due to the new refrigeration system. The results point out for improvements of 4.22% on the power output, corresponding to the electricity demand of approximately 32960 Brazilian homes per month or yearly earnings of 3.92 million USD.

Predicting length of fatigue cracks by means of machine learning algorithms in the small-data regime

In this paper several statistical learning algorithms are used to predict the maximal length of fatigue cracks based on a sample composed of 31 observations. The small-data regime is still a problem for many professionals, especially in the areas where failures occur rarely. The analyzed object is a high-pressure Nozzle of a heavy-duty gas turbine. Operating parameters of the engines are used for the regression analysis. The following algorithms are used in this work: multiple linear and polynomial regression, random forest, kernel-based methods, AdaBoost and extreme gradient boosting and artificial neural networks. A substantial part of the paper provides advice on the effective selection of features. The paper explains how to process the dataset in order to reduce uncertainty; thus, simplifying the analysis of the results. The proposed loss and cost functions are custom and promote solutions accurately predicting the longest cracks. The obtained results confirm that some of the algorithms can accurately predict maximal lengths of the fatigue cracks, even if the sample is small.

Study of biodiesel specifications for heavy-duty gas turbine application

Implementing a 20% biodiesel blend in diesel fuel (B20) has been launched since January 1th, 2016, and it was increased to 30% (B30) on January 1th, 2020, implemented in all sectors, including power generators. Gas turbines utilized as power generators designed to use natural gas or diesel fuel as fuel. Therefore, a study to use biodiesel blend as fuel in gas turbines was required. A comparative study was conducted to analyze the fuel requirements of General Electric’s (GE) Heavy Duty (HD) Gas Turbine specification compared to either of SNI 7182: 2015 and EN 14214 specifications. An assessment was conducted on samples of two biodiesel quality levels called biodiesel and distilled biodiesel to meet the GE HD Gas Turbine’s requirements. This study indicates that the biodiesel quality standards, both SNI 7182: 2015 and EN 14214, are insufficient to meet the gas turbine fuel specifications of the GE HD gas turbine. It is required a more specific quality standard dedicated to gas turbines. On the other hand, among the two samples, distilled biodiesel fulfills the fuel requirements of GE HD gas turbines and might be utilized as fuel for this type of gas turbine. According to the result of this study, a test run of 100% biodiesel (B100) as gas turbine fuel can be proposed to be implemented immediately.

Experimental investigation of combustion dynamics and NOx/CO emissions from densely distributed lean-premixed multinozzle CH4/C3H8/H2/air flames

Lean-premixed fuel-flexible combustion technology capable of operating on a wide range of fuels, including high or pure hydrogen, is expected to play a crucial role in reducing nitrogen oxides and carbon dioxide emissions from heavy-duty gas turbine engines, ultimately in achieving energy system decarbonization. However, fuel-flexible operations, particularly with high hydrogen content fuels, require a fundamental, drastic change from conventional nozzle architecture. The use of a number of small-scale multitube injectors – also referred to as micromix nozzles – is indispensable to reduce the likelihood of flashback events in ultra-fast premixed hydrogen flames. At present, the vast majority of what is known about the fundamental mechanisms of combustion dynamics and emissions stem from intensive research in large-scale swirl-stabilized flames. The behavior of small-scale multinozzle flames governed by isolated or collective movements of constituent flames remains, however, largely unexplored. To address these questions, we use densely distributed sixty-injector mesoscale flames as a platform to explore the influence of a full range of CH4/C3H8/H2 fuel blends – including all possible combinations of a blend of two different fuels (CH4 + C3H8, CH4 + H2, C3H8 + H2) and three different fuels (CH4 + C3H8 + H2), as well as single-component fuels (CH4, C3H8, H2) – on combustion dynamics and exhaust emissions under a constant adiabatic flame temperature condition. Here, we show that while the nitrogen oxide emissions are almost unaffected by the fuel compositions considered here, the variation of fuel composition has a significant impact on self-excited instabilities, which tend toward higher frequency oscillations with increasing hydrogen concentration. From phase-resolved OH PLIF measurements for a 50/50 mixture of CH4 and H2, we identify the creation, evolution, and annihilation of an array of coherent vortical structures as the mechanism responsible for sound generation and flame surface modulations without strong interactions between adjacent flames. In contrast, the behavior of the 50% C3H8 + 50% H2 case is dictated primarily by periodic merging and separation of neighboring reactant jets, leading to large-scale asymmetric oscillations in the transverse direction. Given the substantial change in transport properties, effective Lewis number-related interpretation provides a reasonable explanation for the different behaviors of a cluster of small-scale flames.

Fault detection and isolation of gas turbine using series–parallel NARX model

This paper describes the design and implementation of intelligent dynamic models for fault detection and isolation of V94.2(5)/MGT-70(2) single-axis heavy-duty gas turbine system. The series–parallel structure of nonlinear autoregressive exogenous (NARX) models are used for fault detection, which initiate greater robustness and stability against uncertainties and perturbations. Moreover, to improve the fault detection robustness against uncertainties, the Monte Carlo technique is used in the proposed fault detection structure to select the best threshold. The analysis of fault detectability and fault detection sensitivity are accomplished to analyze the performance of the suggested technique. The fault isolation process is also achieved by using the residual classification approach. The results show the feasibly, robustness, and performance of the presented approach for fault diagnosis of nonlinear systems in the presence of uncertainties.

Modeling of Natural Gas Composition Effect on Low NOx Burners Operation in Heavy Duty Gas Turbine

Abstract This paper addresses the impact of natural gas composition on both the operability and emissions of lean premixed gas turbine combustion system. This is an issue of growing interest due to the challenge for gas turbine manufacturers in developing fuel-flexible combustors capable of operating with variable fuel gases while producing very low emissions at the same time. Natural gas contains primarily methane (CH4) but also notable quantities of higher order hydrocarbons such as ethane (C2H6) can also be present. A deep understanding of natural gas combustion is important to obtain the highest combustion efficiency with minimal environmental impact. For this purpose, Large Eddy Simulations of an annular combustor sector equipped with a partially premixed burner are carried out for two different natural gas compositions with and without including the effect of flame strain rate and heat loss resulting in a more adequate description of flame shape, thermal field, and extinction phenomena. Promising results, in terms of NOx, compared against available experimental data, are obtained including these effects on the flame brush modeling, enhancing the fuel-dependency under nonadiabatic condition.

Gamma Prime Solutioning Tests of Alloy 247 Specimens

Abstract Strictly speaking, this contribution is not about a case study in failure analysis. However, the investigation described herein was inspired by a failure case. A heavyduty gas turbine engine used in a power and desalination plant in the Middle East experienced creep damage and cracking in some of its row 4 turbine blades after only some 15,000 operating hours. Microstructural alterations detrimental to the creep strength of the alloy were determined to be the metallurgical root cause of the failure. It was believed that said microstructural alterations were brought about by unusual transient operating conditions in engine service. Heat treatment tests were ordered to verify or disprove this hypothesis. It was established that the peculiar gamma prime morphology found in the failed blades can be produced by very high solutioning temperatures and subsequent rapid cooling. Such conditions in engine service are conceivable if sufficient unburnt fuel enters the turbine and ignites downstream of the combustion chamber (high temperature), and if water used in fuel line purging is injected into the turbine section immediately thereafter (rapid cooling). Solutioning above 1240 °C, followed by a water quench, produced said mono-modal fine γ' morphology.

A new correlation for estimating the gas turbine cost

The recent changes in energy scenario with rising attention to decarbonization, introduction of new technology and renewable source have led to design power plant with the lowest values of cost of energy, investment payback period, CO2 emission, especially in cogeneration and combined cycle plants. The cost of a gas turbine, an industrial key intellectual property value, represents a large portion of total plant capital cost. In fact, the correlations used to determine this cost, represent an important part in the optimization of power plant studied. In this work, a new cost correlation has been determined using gas turbine data presents into GTW handbook. The overall correlation, dependently only on gas turbine output power, used in a lot of scientific studies is here actualized, calculating new split-power and new coefficients for Heavy Duty and Aeroderivative gas turbine. Therefore, a more complete and detailed correlation is developed, introducing additional parameters, such as thermodynamic efficiency, pressure ratio, exhaust temperature and exhaust mass flow rate, whose values are available on gas turbine datasheet. The new correlation here proposed reflects better real gas turbine configurations and costs.

Numerical Analysis of stress evolution in thermal barrier coating system during two-stage growth of heterogeneous oxide

The mechanical stability of the thermal barrier coating (TBC) systems is important for the heavy-duty gas turbine during operation and maintenance. The growth of thermally grown oxide (TGO), which controls the mechanical stability of TBC systems, usually consists of two stages. In the first stage, the outer mixed oxide (MO) and alumina grow simultaneously. In the second stage, the intact alumina protective layer is gradually replaced by the porous inner MO. The MO deteriorates the interface integrity and exhibits a higher growth rate, which should be investigated. In this study, a numerical method was developed to simulate the stress evolution of two-stage TGO growth. The results show that the inner MO growth can significantly change the stress evolution during high-temperature oxidation and induce higher thermal mismatch stress after cooling down. This adverse effect enhances the risk of TC failure and should be taken seriously in the heavy-duty gas turbine's operation and maintenance.

Estimation of NOx emissions from the combustion chamber of heavy-duty gas turbines

In order to study the estimation of NOx emission, numerical optimization and data fitting methods are used to study the NOx emission law of the combustion chamber of heavy-duty gas turbines. The inlet pressure Pin, air mass flow ma, and average temperature in the combustion zone Tpz are used for the fitting of NOx emission estimation formula under the multi-parameter impact. The results show that this is a fast and effective research method for the estimation of NOx emissions in the combustion chamber under the condition of ensuring the accuracy, which can obtain the NOx emission far below the average level under the condition of optimal inlet pressure.

Improving load changing rate of heavy duty gas turbine applied with overground Compressed Air Energy Storage (CAES) system

Improving load changing rate of heavy duty gas turbine applied with overground Compressed Air Energy Storage (CAES) system

Impact of Compressor Flexibility Improvements on Heavy-Duty Gas Turbine for Minimum and Base Load Conditions

Impact of Compressor Flexibility Improvements on Heavy-Duty Gas Turbine for Minimum and Base Load Conditions

An LSTM-BINN Approach for Built-In Test Analog Signal State Recognition of Heavy-Duty Gas Turbine Controllers

Built-in test (BIT) is widely employed in equipment state detection. However, the high false alarm rate (FAR) of conventional BIT leads to troubles for manufacturers and users. To solve this problem, a novel BIT analog signal recognition algorithm that integrates long short-term memory (LSTM) and biologically inspired neural network (BINN) is proposed in this article. The effects of signal noise and intermittent faults on BIT results are effectively reduced. The proposed algorithm is mainly used for the BIT analog signal of heavy-duty gas turbine controllers, LSTM is used for preliminary modeling of analog signals, and the BINN is introduced into the extra signal state recognition, serving as a classifier based on stimulation transmission among neurons. Furthermore, the gravitational search algorithm (GSA) is employed to optimize the parameters of the proposed algorithm to improve its performance. By employing BIT temperature signal data from heavy-duty gas turbine controllers, extensive experimental results were given to show that the proposed approach was reasonable and accurate by comparison with conventional BIT. By comparing with other common neural network algorithms, the developed approach can provide lower FAR and more accurate recognition results.

A Study on solid oxide fuel cell hybrid system combined with an existing heavy-duty gas turbine to promote the use of hydrogen

A Study on solid oxide fuel cell hybrid system combined with an existing heavy-duty gas turbine to promote the use of hydrogen

A guideline to link the off-design performance of a micro-gas turbine to a heavy-duty gas turbine in a test rig that aim to investigate flexibility of GTCC

In the era of coal power station phase-out, natural gas fired combined cycle will drive the energy transition towards sustainable power generation. In a panorama of strong requirement for grid flexibility and non-dispatchable renewable penetration, the survival of a thermal power plant is strictly linked with operating successfully in compensating the renewable fluctuating production through flexible generation. The Italian case is taken as reference, considering that energy transition and renewable energy penetration may have similar effects also in different countries. In this direction, a test rig to investigate gas turbine compressor inlet conditioning techniques has been developed at the Tirreno Power laboratory of the University of Genoa, Italy. This is based on a Turbec T100 micro gas turbine (or microturbine), a Mayekawa heat pump and a phase-change material energy storage. The whole test-rig is virtually scaled up, through a cyber-physical system, to emulate a real 400MW combined cycle, with the heat pump governing the inlet conditions at the compressor. The microturbine is therefore used as the physical feedback for the system, whilst the steam bottoming cycle is simulated in real-time according to microturbine operation. The scope is to present the test rig and the procedure adopted to virtually scaleup a microturbine to a heavy-duty GT. the advantage of using microturbine for testing combined cycle flexibility options lays also on the possibility to make accelerated tests and to simulate multiple situations in compressed time windows.

Conceptual Approach to Combustor Nozzle and Reformer Characteristics for Micro-Gas Turbine with an On-Board Reforming System: A Novel Thermal and Low Emission Cycle

In order to implement moderate or intensive low oxygen dilution (MILD) combustion, it is necessary to extend the flame stability and operating range. In the present study, the conceptual designs of a combustor single nozzle and reformer were numerically suggested for a micro-gas turbine with an on-board reformer. The target micro-gas turbine achieved a thermal power of 150 kW and a turbine inlet temperature (TIT) of 1200 K. Studies on a nozzle and reformer applying an open-loop concept have been separately conducted. For the nozzle concept, a single down-scaled nozzle was applied based on a reference nozzle for a heavy-duty gas turbine. The nozzle can achieve a good mixture with a high swirl with a splined swirl curve lower NOx emissions and smaller pressure drop in the combustor. The concept of the non-catalytic partial-oxidation reforming reformate was designed using the combustor outlet temperature (COT) of the exhaust gas. Feasible hydrogen yields were mapped through the reformer. Based on the hydrogen yields from the reformer, hydrogen was added to the nozzle to investigate its combustion behavior. By increasing the hydrogen addition and decreasing the O2 fraction, the OH concentrations were decreased and widely distributed similar to the fundamental characteristics of MILD combustion.

An innovative sliding mode load controller for gas turbine power generators: Design and experimental validation via real-time simulation

This paper deals with the design of an innovative load controller for heavy-duty gas turbine (GT) power generators and with its practical implementation on real industrial power plants. A robust controller based on the Sliding Mode control technique is designed, in order to improve the performance of the GT system with respect to the traditional Proportional-Integral-Derivative regulation.The main aim of this paper is to fill the gap between theoretical studies and the real deployment of the advanced GT controller based on the Adaptive Sliding Mode control, an improved variant of the traditional Sliding Mode. The main focus of this work is to solve the main limitations of previous works for an effective deployment of the proposed controller on real industrial devices.This work is developed in collaboration with Ansaldo Energia S.p.A., the interaction with the industrial partner is one of the key points of this paper allowing the implementation of the proposed controller on real industrial microprocessors and the validation in a Real Time Simulation environment at the Ansaldo Energia S.p.A. R&D laboratories. The controller validation, performed in a Hardware-In-the-Loop set-up, showed highly satisfactory results and important improvements in comparison with the traditional regulation of the GT power generator.

Long-Term Failure Mechanisms of Thermal Barrier Coatings in Heavy-Duty Gas Turbines

Thermal barrier coatings serve as thermal insulation and antioxidants on the surfaces of hot components. Different from the frequent thermal cycles of aero-engines, a heavy-duty gas turbine experiences few thermal cycles and continuously operates with high-temperature gas over 8000 h. Correspondingly, their failure mechanisms are different. The long-term failure mechanisms of the thermal barrier coatings in heavy-duty gas turbines are much more important. In this work, two long-term failure mechanisms are reviewed, i.e., oxidation and diffusion. It is illustrated that the growth of a uniform mixed oxide layer and element diffusion in thermal barrier coatings are responsible for the changes in mechanical performance and failures. Moreover, the oxidation of bond coat and the interdiffusion of alloy elements can affect the distribution of elements in thermal barrier coatings and then change the phase component. In addition, according to the results, it is suggested that suppressing the growth rate of uniform mixed oxide and oxygen diffusion can further prolong the service life of thermal barrier coatings.

Optimal Reduced Order Model of Single- Shaft Heavy Duty Gas Turbine Power Plants

Design of controller and analyzing the response of higher order system in real time environment would be very complex and expensive. Therefore, an attempt has been made in this paper to obtain the reduced order model of single-shaft Heavy duty gas turbine plants ranging from 18.2 to 106.7 MW by using various model order reduction techniques. The step response of Heavy duty gas turbine model using the reduced order models are compared with that of the original MATLAB/ Simulink model. Various time domain specifications and performance index criteria have been considered for analyzing the responses. The simulation results show that the response obtained by Routh approximation-Pade approximation technique based reduced order model mimics the original, higher order Heavy Duty gas turbine response. It is also proposed in this paper to improve the response by optimizing the co-efficients of reduced order model using Particle Swarm Optimization technique. On comparing the simulation results, Particle Swarm Optimization technique based reduced order model yield better transient and steady state response as close to original higher order system and hence it is identified as an optimal reduced order model for all Heavy Duty gas turbine plants in grid connected operation

TGSim Plus™—Real-Time Dynamic Simulation Suite of Gas Turbine Systems for the MATLAB®/Simulink® Environment

Dynamic simulation of turbomachinery by Hardware in the Loop (HIL) real-time systems has become an essential practice, due to the high cost of real equipment testing and the need to verify the control and diagnostic systems’ reaction to emergency situations. The authors developed a full model of a power generation Gas Turbine Plant, including liquid and gaseous auxiliaries, and the electrical generator and starter motor, integrated in a MATLAB®/Simulink® simulation suite: TGSim Plus™. This allows assembling models of various gas turbine (GT) architectures by customised Simulink® library blocks and simulating steady state and transient conditions, such as complete start-up and shutdown operations as well as emergency, contingent operations and artificially injected fault scenarios. The model solver runs real-time steps at milliseconds scale. The paper describes the main modelling characteristics and typical results of steady state and transient simulations of a heavy-duty gas turbine under development by Doosan Heavy Industries and Construction (Changwon, South Korea). Comparison with benchmark design simulations obtained by a reference non real-time software shows a good match between the two environments, duly taking into account some differences in the GT models setting affecting parts of the sequence. The paper discusses also the bleed streams warm-up influence on GT performance and the start-up states trajectories dependency on control logic and on the starter helper motor torque envelope.