Gas Turbine System Research Articles

Fault-tolerant control for T-S fuzzy systems with an aperiodic adaptive event-triggered sampling

This article investigates the exponential stabilization problem for Takagi-Sugeno (T-S) fuzzy systems with actuator faults and aperiodic sampling. First, the fault-tolerant control is designed for T-S fuzzy systems under the given actuator fault model. Second, unlike the existing periodic mechanisms, an improved aperiodic adaptive event-triggered (AET) control scheme is established. The threshold is updated adaptively during the sampling process, which greatly reduces the amount of information transmitted. Then, based on Lyapunov-Krasovskii functional (LKF) method, two sufficient exponential stability conditions are derived. In order to derive the less conservative result, a two-sided looped-functional is constructed. In addition, according to stability conditions and fault-tolerant mechanism, the corresponding sampled-data controller is designed. Finally, a numerical example and a simplified gas turbine system are employed to demonstrate the virtue and effectiveness of application of the proposed scheme.

Effect of LR-type trapezoidal fuzzy numbers on profit analysis of gas turbine system

Effect of LR-type trapezoidal fuzzy numbers on profit analysis of gas turbine system

Techno-economic investigations of supercritical CO2-based partial heating cycle as bottoming system of a small gas turbine

Supercritical CO2 (sCO2) cycles represent an innovative technology especially if applied for waste heat recovery from gas turbines. This work investigates the performance of the partial heating sCO2 cycle as the bottoming cycle of a 5 MW-class gas turbine. Particular attention is paid to the selection of both minimum CO2 pressure and temperature and use of the non-dimensional criterion named Acceleration Margin to Condensation is made to prevent the formation of liquid CO2 droplets at the inlet of the compressor. Moreover, in order to avoid heavily loaded turbomachinery, considerations about the machine Mach numbers result in possible limits for the maximum cycle pressure. Single-stage radial turbomachines are selected and their efficiency calculated according to Aungier's correlations by taking actual size and running conditions into account. Focusing on the net electric power produced by the bottoming cycle and on the corresponding specific cost, a number of investigations has been carried out. After setting a limit for the compressor Mach number, around 1600 kW can be recovered by the sCO2 bottoming cycle, though a techno-economic optimization would guide towards an optimum point with slightly more than 1500 kW of power output and a specific cost for the technology of around 2000 $/kW.

Integrated weld preparation designs for the joining of L-PBF and conventional components via TIG welding

Laser powder bed fusion (L-PBF) of entire assemblies is not typically practical for technical and economic reasons. The build size limitations and high production costs of L-PBF make it competitive for smaller, highly complex components, while the less complex elements of an assembly are manufactured conventionally. This leads to scenarios that use L-PBF only where it’s beneficial, and it require an integration and joining to form the final product. For example, L-PBF combustion swirlers are welded onto cast parts to produce combustion systems for stationary gas turbines. Today, the welding process requires complex welding fixtures and tack welds to ensure the correct alignment and positioning of the parts for repeatable weld results. In this paper, L-PBF and milled weld preparations are presented as a way to simplify the Tungsten inert gas (TIG) welding of rotationally symmetrical geometries using integrated features for alignment and fixation. Pipe specimens with the proposed designs are manufactured in Inconel 625 using L-PBF and milling. The pipe assembly is tested and TIG welding is performed for validation. 3D scans of the pipes before and after welding are evaluated, and the weld quality is examined via metallography and computed tomography (CT) scans. All welds produced in this study passed the highest evaluation group B according to DIN 5817. Thanks to good component alignment, safe handling, and a stable welding process, the developed designs eliminate the need for part-specific fixtures, simplify the process chain, and increase the process reliability. The results are applicable to a wide range of components with similar requirements.

Rapid load transition for integrated solid oxide fuel cell – Gas turbine (SOFC-GT) energy systems: A demonstration of the potential for grid response

Rapid load transition is an essential requirement for integrated energy systems to maintain grid resilience as more renewable resources are added to the grid. Integrated solid oxide fuel cell – gas turbine (SOFC-GT) systems can provide high efficiency and low carbon emissions over a broad range of turndown. These hybrids also have the potential to enable rapid grid response. The challenge has been to demonstrate effective control strategies to manage load transitions. In the present study, a load transition of ∼50% was achieved in 10 s using a novel but simple strategy. Power demand on the SOFC and the GT were ramped down concurrently. During this transition, the SOFC anode fuel was manipulated to maintain SOFC fuel utilization while the cathode inlet air flow and temperature were also manipulated to thermally protect the SOFC. This study was conducted using the Hybrid Performance (Hyper) facility at the National Energy Technology Laboratory (NETL) in a co-simulation environment with the Idaho National Laboratory (INL)’s grid-simulation. The load ramping strategy was tested using a hardware-based cyber-physical simulation methodology. The results demonstrate a high-fidelity representation of SOFC-GT hybrid dynamics and validation of the control strategy. Thermal and electrochemical transients indicated that the SOFC was well protected during rapid load turndown without violating operability constraints. This demonstration revealed the non-linear nature of tightly coupled SOFC-GT system components, especially the non-linear response of SOFC cathode air flow and inlet temperature controls. These results highlight the needs and challenges in developing adaptive automatic controls for autonomous rapid load transitions. This work demonstrates that SOFC-GT hybrids are a viable option to provide the fast-ramping characteristics essential to accommodate high levels of variable renewable power while maintaining grid resilience, reliability, and environmental performance. The results also demonstrate the utility of co-simulation in advancing the tightly-coupled integrated energy systems needed to meet goals for zero-carbon power generation.

Controlling the flow distribution characteristics in the secondary air system of a gas turbine

Increased gas turbine system efficiency is accompanied by increases in turbine inlet temperature, mass flow rate, and pressure. Because the turbine blade is exposed to high temperatures and high pressure, the secondary air system (SAS) should be designed to optimize operating conditions and blade life. The cooling air discharged from the compressor flows into the rotating disk through the pre-swirl system, then into the receiver holes during the respective stage of the turbine. In this study, the flow distribution characteristics of the secondary cooling air, which flows into the first-stage turbine blade and the second-stage cavity, were analyzed using validated computational fluid dynamics (CFD) methodology. CFD techniques were validated by comparative analysis of various CFD techniques on the experimental data of Bath University and Hanyang University in the previous studies. To apply the k-ω SST turbulence model, which was the most effective technique, the grids near the wall was constructed with y+ one or less. The frozen rotor method was applied to the stationary-rotating interface to satisfy the change in pitch ratio for each components. As a result, methodologies had been devised to control each flow properties while maintaining SAS efficiency through a change in system outlet area. When the swirl ratio was maintained at one, it was possible to change the mass flow rate for the outlet area without reducing the system efficiency. On the other hand, the outlet static pressure could be changed for the outlet area regardless of the swirl ratio, but the choked flow occurred below a specific pressure ratio. Finally, mass flow rate and static pressure at the receiver hole outlet could be controlled respectively, and the performance curves of the SAS within the designable range were also presented.

Market Opportunities of Water Treatments Powered by Solar Micro Gas Turbines: Chile and Ecuador Case Studies

Throughout the last decades the developments on desalination field have been focused on energy consumption and costs reduction. However, water recovery and brine disposal are becoming a matter of concern to desalination industry. In this work, a Zero Liquid Discharge (ZLD) unit coupled with a Solar Micro Gas Turbine (SMGT) system is presented to address, among others, the challenges of mining industry in remote areas, in particular, fossil fuel dependence, water availability and pollution derived from effluents disposal. As a way to assess the feasibility of the proposal, a techno-economic analysis of the application in two Southern American regions (Chile and Ecuador) of photovoltaic modules, wind turbines and Solar Micro Gas Turbines is performed. Afterwards, the main novel feature of the new system—i.e., the ZLD unit—is described and a sensitivity analysis on its functioning whilst coupled with the SMGT is carried out. The aim is to propose a preliminary design of the ZLD process. The selection of the optimal ratio between exhaust gases and brine mass flow rates is analyzed, as well as variation in inlet salinity and temperatures. Furthermore, the water which could be recovered from effluents, at the same time that the heat of exhaust gases from SMGT is harvested, is quantified. Lastly, according to the results obtained, a preliminary design of a 10 kWe rated power SMGT system, coupled to Reverse Osmosis (RO) and ZLD units, is proposed.

Resilient Event-Triggered Control for Networked Cascade Control Systems Under Denial-of-Service Attacks and Actuator Saturation

This article addresses the issues of exponential stabilization and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_2$</tex-math></inline-formula> -gain analysis for networked cascade control systems with aperiodic denial-of-service (DoS) jamming attacks, time delay, actuator saturation, and external disturbances. A resilient event-triggered communication mechanism based on the adaptive threshold technique is proposed to reduce transmission frequency and combat aperiodic DoS attacks. An event-driven cascade control strategy is developed to schedule control process updates and strengthen resistance to DoS attacks. Then, the system is modeled as a switched system closely related to the bounds of DoS frequency and duration. By using Lyapunov stability theory, conditions for the resultant system to be exponentially stable with a desired <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L_2$</tex-math></inline-formula> -gain performance level are established. A solution to the joint-design problem of controller gains and event-triggered parameters is also provided. A gas-turbine system of a power plant is employed to illustrate the effectiveness of the proposed approach.

Techno-Environmental Evaluation of a Liquefied Natural Gas-Fuelled Combined Gas Turbine with Steam Cycles for Large Container Ship Propulsion Systems

Restrictions on emissions are being imposed by regional and international shipping organisations, which raise the question of which marine fuel and technology can most effectively replace heavy fuel oil and diesel engines. The aim of this study is to find appropriate advanced combined gas and steam turbine cycles for marine propulsion systems in a large container ship with respect to the evolving maritime environmental regulations. The selection criteria are the thermodynamic performance, emissions, size, and weight of advanced combined gas and steam turbine cycles in a large container ship. Two baselines are used: a diesel engine using marine diesel oil and a combined gas and steam turbine system using liquefied natural gas and marine diesel oil. Then, liquefied natural gas cycles are examined based on fuel replacement and enhanced to assess the benefits of liquefied natural gas over marine diesel oil. The results show that the enhanced liquefied natural gas combined gas and steam turbine cycles are the most efficient, at up to 1.6% higher than the other cycles. Regarding the size and weight, the combined gas and steam turbine propulsion system is approximately 24.7% lighter than the original diesel engine propulsion system.

Efficiency Enhancement of Gas Turbine Power Output by Cooling Inlet Air

Electrical power generation can be achieved through many means, one of which includes using a gas turbine. Gas turbine performance is highly dependent on ambient temperature; as temperature increases gas turbine power output is lessened. This can be a huge problem in warmer regions like Nigeria. Gas turbines use the surrounding air to generate electricity and this gives rise to a method or curbing the effect of high ambient temperatures. Once the volumetric rate is constant as is the case in a gas turbine system, air density and ambient temperature are inversely proportional; this allows mass flow rate to be inversely proportional to temperature. To fully take advantage of this, there are many methods that can be implemented to achieve this cooling effect. A few of these methods were investigated in this study to determine their strengths and susceptibilities. The performance characteristics were scrutinised for a range of operational values including ambient temperature, humidity and air density. The results showed that air cooling significantly improved the power output of the gas turbine. At standard temperature of 32oc, the base case was 37.87 MW while evaporative cooler, mechanical and absorption chillers were 37.70 MW, 40.39 MW and 41.07 MW respectively.

Techno-economic assessment for a pumped thermal energy storage integrated with open cycle gas turbine and chemical looping technology

Pumped thermal energy storage offers a high energy density, potentially resulting in a relatively low cost per unit of energy stored. In this study, two novel energy storage systems were developed. The first system was developed by integrating pumped thermal energy storage and chemical looping technologies, whereas the second was formed by merging the first system with an open cycle gas turbine. Both systems used an oxygen depleted stream as a working fluid and iron-based oxygen carriers from a chemical looping water splitting process storage material for the pumped thermal energy storage system. In addition, hydrogen from the chemical looping process was employed for the gas turbine in the second system. Both systems were evaluated thermodynamically via the determination of the roundtrip efficiency. The results presented here indicate that the roundtrip efficiency of both systems developed was 77%. Furthermore, the capital requirements, operating costs, and daily profits from electricity generation were calculated for both systems over several days within the year. The capital and operating costs for the several days that were simulated for the integrated pumped thermal energy storage system were lower than that of a gas turbine based system. Consequently, the daily profit was estimated and found to be between 4.9% and 72.9% higher for the integrated pumped storage relative to the gas turbine based system. Moreover, an economic sensitivity analysis was performed to identify the factors that strongly affect the daily profits of the gas turbine system relative to the pumped storage system. Based on the analysis, the optimal hydrogen fuel percentage fed to the open cycle gas turbine was calculated for the days simulated. Finally, the impact of % error on the estimated capital and fuel production costs on daily profits were investigated. The outcome revealed a higher impact of computational errors on the fuel costs relative to the costs of the capital.

Suppression of thermoacoustic instability and NOx emissions of unsteady swirl premixed flame with upstream microjets

AbstractPassive control methods are widely used in unsteady combustion systems due to their robustness and convenience. This paper used the upstream microjets method for the first time to control thermoacoustic instability and pollutant NOx emissions in unsteady swirl premixed flame. Three variables of CO2 microjets flow rate, upstream microjets distance, and microjets number are investigated. Results demonstrate the upstream microjets distance plays a significant role in restraining the thermoacoustic instability and NOx emissions. The smaller the upstream microjets distance, the more completely the thermoacoustic instability is suppressed while the NOx emissions are the opposite, which means a compromise choice needs to be made between them. The damping ratio of pressure amplitude in the chamber can reach the maximum of 81.3%, and the damping ratio of CH* intensity can reach the maximum of 80.2%. Besides, the frequency of pressure and CH* will transit to a lower mode. NOx emissions can realize a maximum reduction of 12.2 ppm. Meanwhile, the flame mode switches from an enlarged Mode‐A flame to a shrunk Mode‐B flame, and the flame length shows a maximum reduction of 14 mm at the largest upstream distance. However, the specific control mechanism under upstream microjets still needs further study to clarify. This research proved the feasibility of suppressing combustion instability and NOx emissions with upstream microjets in unsteady swirl premixed flame, promoting its practical application in gas turbine systems.

Thermoeconomic Diagnosis of the Sequential Combustion Gas Turbine ABB/Alstom GT24

In this study, we used the thermoeconomic theory to evaluate the impact of residue cost formation on the cost of electricity generated from natural gas burned in a gas turbine that applied sequential combustion; we also analyzed the impact of the combustion process on the additional fuel consumption to compensate for a malfunction component. We used the Alstom GT24 gas turbine, which applied sequential combustion and generated 235 MW of power. Thermoeconomic analysis indicated that the exergy cost of power generation was 626.33 MW (30.42% corresponded to irreversibility costs, and 29.22% and 2.84% corresponded to the formation costs of physical and chemical residues, respectively). The exergoeconomic production cost of gas turbine was 10,098.71 USD/h, 34.76% from external resources and 65.24% from capital and operating costs. Thermoeconomic diagnosis revealed that a compressor deterioration (of 1-% drop in the isentropic efficiency) resulted in an additional fuel consumption of 4.05 MW to compensate for an increase in irreversibilities (1.97 MW) and residues (2.08 MW); the compressor generated the highest cost (49.9% of additional requirement). Thus, our study can identify the origin of anomalies in a gas-turbine system and explain their effects on the rest of the components.

Impact of fuel type on the performance of a solid oxide fuel cell integrated with a gas turbine

This study investigates the performance of a flame-assisted fuel cell integrated with a gas turbine operating with six fuels (CH4, C3H8, JP-4, JP-5, JP-10, and H2). A thermodynamic model is developed for the fuel-rich combustion, fuel-lean combustion and each step of the gas turbine including the compressor, turbine and recuperator in order to analyze the overall hybrid gas turbine cycle. As the fuel/air equivalence ratio increases, the hybrid system efficiency increases initially then decreases despite increasing hydrogen concentration in the exhaust. The peak efficiency occurs around an equivalence ratio of 2 for all fuels. The optimal performance of the hybrid system utilizes H2 as the fuel. The peak electrical efficiency of the hybrid setup is 64.7% with H2 fuel, 60.3% with CH4 fuel, 60.9% with C3H8 fuel, 61.7% with JP-4 fuel, 61.0% with JP-5 fuel and 61.2% with JP-10 fuel, representing a significant increase over the standard gas turbine cycle. With H2 fuel, the overall integrated system is predicted to be 24.5% more efficient than the standard gas turbine system. These results show promise for a fuel flexible hybrid gas turbine which could benefit the growing aircraft industry as the desire for a more electric airplane increases.

Thermal calculations and NOx emission analysis of a micro gas turbine system without a recuperator

A thermal calculation based on a table of thermal properties of gas was carried out for a micro gas turbine system without a recuperator. The performance parameters of the micro gas turbine system were obtained. The results of the thermal calculations were verified using ASPEN PLUS, and it shows that the thermal calculations fit well with the ASPEN simulation results. Based on this thermal calculation method, the variation of the performance parameters of the micro gas turbine system under different pressure and temperature ratios was analyzed. The results show that there is no optimum pressure ratio within the general design parameters of micro gas turbines, which leads to extreme values of thermal efficiency. The NOx generation in the combustion chamber of the micro gas turbine based on the Zeldovich mechanism was modeled and analyzed by coupling the 1-D thermal calculation model with the NOx emission model. The relationship between NOx generation rate, molar fuel factor, the characteristic pressure, and the characteristic temperature was obtained. The results of the analysis show that, in terms of controlling NOx emissions from a gas turbine, the use of an increased pressure ratio has a significant advantage over an increased temperature ratio to improve the thermal efficiency of the micro gas turbine.

Application of the Theory of Constraints to Unveil the Root Causes of the Limited Market Penetration of Micro Gas Turbine Systems

Application of the Theory of Constraints to Unveil the Root Causes of the Limited Market Penetration of Micro Gas Turbine Systems

Fault‐Tolerant Resolvability in Some Classes of Subdivision Graphs

The concept of resolving sets (RSs) and metric dimension (MD) invariants have a wide range of applications in robot navigation, computer networks, and chemical structure. RS has been used as a sensor in an indoor positioning system to find an interrupter. Many terminologies in machine learning have also been used to diagnose the interrupter in the systems of marine and gas turbines using sensory data. We proposed a fault‐tolerant self‐stable system that allows for the detection of an interrupter even if one of the sensors in the chain fails. If the elimination of any element from a RS is still a RS, then the RS is considered as a fault‐tolerant resolving set (FTRS), and the fault‐tolerant metric dimension (FTMD) is its minimum cardinality. In this paper, we calculated the FTMD of the subdivision graphs of the necklace and prism graphs. We also found that this invariant has constant values for both graphs.

Transient Simulation and Optimization of Regional Integrated Energy System

A modeling method of regional integrated energy system based on bus method and transient simulation is proposed, and the system optimization is based on the dynamic balance of supply and demand in the whole year energy supply cycle. A CCHP system of gas turbine coupled with ground source heat pump and electric refrigeration unit is constructed. The energy relationship of the system is described by bus structure, and the transient calculation model is built on TRNSYS platform. The weighted sum of annual total cost saving rate, primary energy saving rate and environmental pollutant shadow cost saving rate is taken as the optimized objective function, and on the basis of annual dynamic balance, the Hooke-Jeeves algorithm is used for optimization of the system configuration. A complex commercial area in Beijing is taken as an example, and different weighting coefficients are set for optimization of the system configuration. The results show that, from the perspective of economy, environmental benefit and primary energy consumption, performance of the system increases and then decreases with rise of gas turbine power; under the simulated cooling/heating load, the maximum number of optimum configuration is seen in the combination of 35 kW gas turbine + 723 kW GSHP and 1178 kW electric chiller; in comparison with traditional distributed system, the annual cost saving rate, primary energy saving rate and environmental pollutant shadow cost saving rate of the system are 29.4%, 49.6% and 58.2%, respectively.

On-board Fault Diagnosis of a Laboratory Mini SR-30 Gas Turbine Engine

Inspired by recent progress in machine learning, a data-driven fault diagnosis and isolation (FDI) scheme is explicitly developed for failure in the fuel supply system and sensor measurements of the laboratory gas turbine system. A passive approach to fault diagnosis is implemented where a model is trained using machine learning classifiers to detect a given set of faults in real-time on which it is trained. Towards the end, a comparative study is presented using well-known classification techniques, namely Support Vector Machine, Linear Discriminant Analysis, K-Neighbors, and Decision Trees. Several simulation studies were carried out to demonstrate the proposed fault diagnosis scheme's advantages, capabilities, and performance.

A comparative study of single-loop control and multi-loop control of gas turbine

Gas turbine is widely used for generation in power plants and propulsion of ships. The gas turbine is required to operate at different conditions on request. However, its complex dynamics such as multivariable coupling, unknown disturbance and strong nonlinearity, makes it a challenging task to control the gas turbine system. In this paper, a linear offset-free model predictive control algorithm is designed for the gas turbine. Two control modes including single-loop and multi-loop are investigated under the designed control method. Simulations are used to compare the two control mode. From the significant differences, multi-loop mode is preferred because of better performance of reference tracking and disturbance rejection.