Turbine Applications Research Articles

The performances and applications of gas turbines in the aviation industry

This paper focuses on using gas turbines in various industries, particularly aviation, due to their unique power-to-weight ratio. It provides a detailed description of how gas turbines operate based on the thermodynamic Brayton cycle, which includes compressors, combustors, and power turbines. Additionally, the paper analyses both ideal and realistic cycles of gas turbines. Despite numerous advantages, gas turbines have limitations, such as high fuel consumption. However, technological advancements have led to the development of more efficient and quieter gas turbines. The paper explains the classification of jet engines, including turbojets, turboprops, and turbofans, each with specific applications. Moreover, the paper discusses the efforts to reduce the use of fossil fuels in aviation due to the increasing awareness of the impact of climate change. Scientists and engineers are exploring substitute fuels and materials and developing gas turbine systems that maximize work generated with minimal combustion; thus, this paper also highlights the importance of developing more efficient and environmentally friendly gas turbines to reduce the industry's carbon footprint while maintaining their productivity.

Small-scale power generation using stationary gas turbine with renewable energy

This article mainly discusses one of the most important applications of stationary gas turbinesthe small-scale power generation. Micro/Small-scale gas turbines have immense hidden potential due to fuel flexibility, low emissions and maintenance. In recent years, the substantial pressure to address environmental issues has led people to focus more on green technologies, so most of the related applications of micro gas turbines use renewable energy like wind energy or biomass. Small-scale power generation can be applied in commercial and residential areas and areas with worse living conditions, such as rural or remote ones. And it is usually designed to exploit more waste heat for cooling/heating purposes. Anyway, there are still drawbacks exist. These turbines require high angular velocity and advanced electronics that can convert high-frequency electricity. The author surveyed distributed energy generation, biomass power plants and mini/micro gas turbines, some typical examples of small-scale power generation that are also stationary and have combustion processes. This application of stationary gas turbines is relatively more innovative and updated than others, so there are not many reliable researches posted online in recent years. This paper will reference all the researchers who want to work in this field.

Data-augmented modeling for yield strength of refractory high entropy alloys: A Bayesian approach

Refractory high entropy alloys (RHEAs) have gained significant attention in recent years as potential replacements for Ni-based superalloys in gas turbine applications. Improving their properties, such as their high-temperature yield strength, is crucial to their success. Unfortunately, exploring this vast chemical space using exclusively experimental approaches is impractical due to the considerable cost of the synthesis, processing, and testing of candidate alloys, particularly at operation-relevant temperatures. On the other hand, the lack of reasonably accurate predictive property models, especially for high-temperature properties, makes traditional Integrated Computational Materials Engineering (ICME) methods inadequate. In this paper, we address this challenge by combining machine-learning models, easy-to-implement physics-based models, and inexpensive proxy experimental data to develop robust and fast-acting models using the concept of Bayesian updating. The framework combines data from one of the most comprehensive databases on RHEAs (Borg et al., 2020) with one of the most widely used physics-based strength models for BCC-based RHEAs (Maresca and Curtin, 2020) into a compact predictive model that is significantly more accurate than the state-of-the-art. This model is cross-validated, tested for physics-informed extrapolation, and rigorously benchmarked against standard Gaussian process regressors (GPRs) in a toy Bayesian optimization problem. Such a model can be used as a tool within ICME frameworks to screen for RHEAs with superior high-temperature properties. The code associated with this work is available at: https://codeocean.com/capsule/7849853/tree/v2.

Design and optimization of fatigue life studies on induction hardened IN718 alloy for gas turbine applications

ABSTRACT The Inconel 718 (IN718) superalloy is commonly used as a component in industrial gas turbines due to its excellent corrosion resistance and high-temperature properties. Generally, gas turbines experience failure in their service on account of high thermal fatigue. In the present research, specimens of Inconel 718 superalloy are treated at two different temperatures 850℃ and 1000℃ (IHT1 & IHT2) with oil quenching, respectively. The specimens are studied with controlled strain amplitudes for different values 0.6%, 0.7% & 0.8% at room temperature and 800°C. It is noticed that the fatigue lifetimes of induction-hardened specimens are greater than those of untreated specimens at the above-mentioned strain amplitude values at room and elevated temperature, whereas the fatigue life of all the specimens reduces as strain amplitudes increase. Interestingly, the stress difference among the three strain amplitudes gradually decreases as the fatigue test progresses and induction-hardened specimens have cyclic softening behaviour as compared to untreated specimens’ cyclic hardening behaviour. Additionally, the mode of fracture for IN718 superalloys in the current study is entirely transgranular, as shown by the fracture surface observation using a scanning electron microscope (SEM).

The Effect of Leading-Edge Wavy Shape on the Performance of Small-Scale HAWT Rotors

The purpose of this experimental work was to investigate the role of the leading-edge wavy shape technique on the performance of small-scale HAWT fixed-pitch rotor blades operating under off-design conditions. Geometric parameters such as amplitude and wavelength were considered design variables to generate five different wavy shape blade models in order to increase the aerodynamic performance of the rotor with a diameter of 280 mm. A dedicated airfoil type S822 for small wind turbine application from the NREL Airfoil Family was chosen to fulfil both the aerodynamic and structural aspects of the blades. Rotor models were tested in a wind tunnel for different wind speeds while maintaining constant rotational speed to provide the blade-tip chord Reynolds number of 4.7 × 104. The corrected tunnel data, in terms of power coefficients and tip-speed ratios, were compared first with the literature to validate the experimental approach, and then among themselves. It was observed that for minimal sizes of tubercles, the performance of the rotor increases by about 40% compared to the RB1 baseline rotor model for a low tip-speed ratio. Conversely, for the maximum size of the tubercles, there is a marked decrease of about 51% of the rotor performance for a moderate tip-speed ratio compared to the RB1 rotor model. Among these models, specifically, the RB2 rotor model with the smallest values of amplitude and wavelength provides a 2.8% higher peak power coefficient compared to the RB1 rotor model, and at the same time preserves higher performance values for a broad range of tip-speed ratios.

Digital Twin as a Virtual Sensor for Wind Turbine Applications

Digital twins (DTs) have been implemented in various applications, including wind turbine generators (WTGs). They are used to create virtual replicas of physical turbines, which can be used to monitor and optimize their performance. By simulating the behavior of physical turbines in real time, DTs enable operators to predict potential failures and optimize maintenance schedules, resulting in increased reliability, safety, and efficiency. WTGs rely on accurate wind speed measurements for safe and efficient operation. However, physical wind speed sensors are prone to inaccuracies and failures due to environmental factors or inherent issues, resulting in partial or missing measurements that can affect the turbine’s performance. This paper proposes a DT-based sensing methodology to overcome these limitations by augmenting the physical sensor platform with virtual sensor arrays. A test bench of a direct drive WTG based on a permanent magnet synchronous generator (PMSG) was prepared, and its mathematical model was derived. MATLAB/Simulink was used to develop the WTG virtual model based on its mathematical model. A data acquisition system (DAS) equipped with an ActiveX server was used to facilitate real-time data exchange between the virtual and physical models. The virtual sensor was then validated and tuned using real sensory data from the physical turbine model. The results from the developed DT model showed the power of the DT as a virtual sensor in estimating wind speed according to the generated power.

Economic competitiveness of pultruded fiber composites for wind turbine applications

Pultrusion manufacturing of fiber reinforced polymers has been shown to yield some of the highest mechanical properties for unidirectional composites, having a high degree of fiber alignment with consistent performance. Pultrusions offer a low-cost manufacturing approach for producing unidirectional composites with a constant cross-section and are used in many applications, including spar caps of wind turbine blades. However, as an intermediate processing step for wind blades, the additional cost of manufacturing pultrusions must be accompanied by sufficient increases in mechanical performance and system benefits. Wind turbine blades are manufactured using vacuum-assisted resin transfer molding with infused unidirectional fiberglass or carbon pultrusions for the spar cap. Infused fiberglass composites are among the most cost-effective structural materials available and replacing this material in the cost-driven wind industry has proven challenging, where infused fiberglass spar caps are still the predominant material system in use. To evaluate alternative material systems in a pultruded composite form, it is necessary to understand the costs for this additional manufacturing step which are shown to add 33%–55% on top of the material costs. A pultrusion cost model has been developed and used to quantify cost sensitivities to various processing parameters. The mechanical performance for pultruded composites is improved versus resin-infusion manufacturing with a 17% increase in design strength at a constant fiber volume fraction, but also enables higher achievable fiber volume fractions. The cost-specific mechanical performance is compared as a function of processing parameters for pultruded composites to identify the opportunities for alternative material and manufacturing approaches for wind turbine spar caps. Four materials are compared in a representative wind turbine blade model to assess the performance of pultruded carbon fiber systems and pultruded fiberglass relative to infused fiberglass, where the pultruded systems produce lower weight blades with various cost distinctions.

Efficient Fault Detection of Rotor Minor Inter-Turn Short Circuit in Induction Machines Using Wavelet Transform and Empirical Mode Decomposition.

This paper introduces a novel approach for detecting inter-turn short-circuit faults in rotor windings using wavelet transformation and empirical mode decomposition. A MATLAB/Simulink model is developed based on electrical parameters to simulate the inter-turn short circuit by adding a resistor parallel to phase "a" of the rotor. The resulting high current in the new phase indicates the presence of the short circuit. By measuring the rotor and stator three-phase currents, the fault can be detected as the currents exhibit asymmetric behavior. Fluctuations in the electromagnetic torque also occur during the fault. The wavelet transform is applied to the rotor current, revealing an effective analysis of sideband frequency components. Specifically, changes in amplitude and frequency, particularly in d7 and a7, indicate the presence of harmonics generated by the inter-turn short circuit. The simulation results demonstrate the effectiveness of wavelet transformation in analyzing these frequency components. Additionally, this study explores the use of empirical mode decomposition to detect faults in their early stages, observing substantial changes in the instantaneous amplitudes of the first three intrinsic mode functions during fault onset. The proposed technique is straightforward and reliable, making it suitable for application in wind turbines with simple electrical inputs.

Laminar burning velocities and Markstein numbers for pure hydrogen and methane/hydrogen/air mixtures at elevated pressures

Spherically expanding flame propagations have been employed to measure flame speeds for H2/CH4/air mixtures over a wide range of H2 fractions (30 %, 50 %, 70 and 100 % hydrogen by volume), at initial temperatures of 303 K and 360 K, and pressures of 0.1, 0.5 and 1.0 MPa. The equivalence ratio (ϕ) was varied from 0.5 to 2.5 for pure hydrogen and from 0.8 to 1.2 for methane/hydrogen mixtures. Experimental laminar burning velocities and Markstein numbers for methane/hydrogen/air mixtures at high pressures, which are crucial for gas turbine applications, are very rare in the literature. Moreover, simulations using three recent chemical kinetic mechanisms (Konnov-2018 detailed reaction, Aramco-2.0-2016 and San Diego Methane detailed mechanism (version 20161214)) were compared against the experimentally derived laminar burning velocities. The maximum laminar burning velocity for 30 % and 50 % H2 occurs at ϕ = 1.1. However, it shifts to ϕ = 1.2 for 70 % H2 and to ϕ = 1.7 for a pure H2 flame. The laminar burning velocities increased with hydrogen fraction and temperature, and decreased with pressure. Unexpected behaviour was recorded for pure H2 flames at low temperature and ϕ = 1.5, 1.7 wherein ul did not decrease when the pressure increased from 0.1 to 0.5 MPa. Although, the measurement uncertainty is large at these conditions, the flame structure analysis showed a minimum decline in the mass fractions of the active species (H, O, and OH) with the rise in the initial pressure. Markstein length (Lb) and Markstein number (Mab and Masr) varied non-monotonically with hydrogen volume fraction, pressure and temperature. There was generally good agreement between simulations and experimentally derived laminar burning velocities, however, for experiments of rich-pure hydrogen at high initial pressures, the level of agreement decreased but remained within the limits of experimental uncertainty.

Concentric-Coil Distributed Winding Design for Large Direct-Drive Fully Superconducting Machines

Fully superconducting generators (FSCGs) use superconducting wires for both the field and armature windings to reach a high torque density for wind turbine applications. The AC armature winding of an FSCG design mostly employed racetrack tooth-coils to form fractional-slot concentrated windings. This winding type has high leakage flux and excessive harmonics, especially when used in superconducting machines. Other attempts like applying full-pitch racetrack coils can only be with one slot per pole per phase which also has significant slotting harmonics. This paper proposes an innovative concept of double-layer concentric coils to enable distributed windings with a larger integral number of slots per pole per phase. The concept successfully breaks the limitation that racetrack coils cannot be built with such integral slots. This paper then assesses the performance of the proposed winding concept within a context 20 MW FSCG design. The assessment finds out that the proposed concept has balanced three phases but reduces inductance compared to single-layer windings. The force on each concentric coil can significantly be different, thereby complicating the mechanical design of these superconducting coils.

Potential Performance of Fully Superconducting Generators for Large Direct-Drive Wind Turbines

Fully superconducting generators (FSCGs) for wind turbine applications are usually synchronous machines. A high torque density should be obtained by increasing both the main field and the armature current loading. However, there are tendencies that the main field can be low but the armature current loading can be high, such as permanent magnet superconducting generators. Despite <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$J_\mathrm{{c}}(B,T)$</tex-math></inline-formula> characteristics and AC loss issues, simply using superconducting armature may not lead to a desired design result but deteriorate the performance with high armature reaction. This paper implements the vector-phasor diagram of non-salient synchronous generators for revealing the potential performance of only increasing the armature current loading. Three commonly used control strategies are compared. The results show that increasing the armature-field flux to a certain level will deteriorate the generator performance with all three control strategies. Comparatively, the voltage control for equaling EMF and voltage amplitudes provides the best overall performance: high torque production capability, high power factor, small power angle and a wide range of armature current loading. The results obtained from the vector-phasor diagrams are verified by finite element models with an FSCG design.

Experimental Analysis on the Operating Line of Two Gas Turbine Engines by Testing with Different Exhaust Nozzle Geometries

This paper presents a special analysis study about the gas turbine operating line, and an overall description of a gas turbines project, based on experimental data from two particular applications, in order to convert two different types of aero engines into the same engine configuration. The experimental works were carried out with the aim of converting an Ivchenko AI-20K turboprop and a Rolls-Royce Viper 632-41 turbojet into free turbine turboshaft engines, to be used in marine propulsion, and also to obtain an experimental database to be used in other gas turbine applications. In order to carry out the experimental work, the engines were tested in turbojet configuration, to simulate the free turbine load by using jet nozzles with different geometries of the outlet cross-section. Following the engines’ tests, a series of measured data were obtained, through which it was possible to experimentally determine the operating line of some engine components such as the compressor, turbine, and exhaust jet nozzle. This paper is comprehensive and useful through its scientific and technical guidelines, the operation curves coming in handy in the thermodynamic analysis and testing methodology for researchers dealing with similar applications.

Understanding the Sintering Behavior and its Effect on the Thermal Conductivity of YSZ Coatings for Gas Turbine Applications

Thermal barrier coatings are essential coatings to protect the combustion chamber liner material from harsh environments in modern gas turbines that are used in aerospace and land-based power generation facilities. As there are several different materials to produce thermal barrier coatings, the conventional thermal barrier coating is yttria stabilized zirconia (YSZ). The most common method to manufacture YSZ coating is plasma spraying method due to its flexibility and rapid production capacity. Using plasma spraying, often requires understanding the process parameters effect on the coating structure. As there are many parameters to control coating process the main outcome of all parameters is the particle temperature and velocity during the spraying process hence the coating properties such as hardness, porosity ratio and deposition rates. Furthermore, not only produced microstructure but also during the service conditions sintering behaviour also be considered. Sintering behaviour of thermal barrier coatings results declining of their thermal insulation properties. Therefore, in this study we have evaluated sintering effect of on the thermal conductivity of the plasma sprayed yttria stabilized zirconia coatings. To achieve this objective, we produced free-standing coatings and subjected them to heat treatment, followed by measurements of their thermal conductivities. The results of this study will contribute to a better understanding of the sintering behaviour and its impact on the thermal performance of thermal barrier coatings.

A Counter-Rotating Double-Rotor Axial Flux Permanent Magnet Generator for Wind Turbine Applications: Design, Simulation, and Prototyping

A Counter-Rotating Double-Rotor Axial Flux Permanent Magnet Generator for Wind Turbine Applications: Design, Simulation, and Prototyping

Design and numerical analysis of tensile deformation and fracture properties of induction hardened inconel 718 superalloy for gas turbine applications

Design and numerical analysis of tensile deformation and fracture properties of induction hardened inconel 718 superalloy for gas turbine applications

Experimental and Numerical Investigation of Channeling Effects on Noise and Aerodynamic Performance of NACA 0012 Aerofoil in Wind Turbine Applications

Wind power is considered one of the main sources of renewable energy in the market today. In this study, different sizes and directions of channels were created inside the NACA 0012 aerofoil, and the effect of these channels were investigated on aerodynamic noise and aerodynamic performance, experimentally and numerically. The results have shown several factors that could affect the aerodynamic noise such as flow velocity, angle of attack, and trailing edge blowing injection. The study also concluded an increase in drag coefficients and a decrease in lift coefficients for all channeled samples compared to the regular aerofoil. In contrast to the studies that showed improvements in the aerodynamic performance of supersonic channeled aerofoils, this study done under subsonic flow showed an increase in drag and decrease in lift.

Investigating horizontal-axis wind turbine aerodynamics using cascade flows

The simplest aerodynamic model of horizontal-axis wind turbines is the blade element momentum theory, which assumes that the blades behave as airfoils, but a correct two-dimensional representation is an infinite cascade of lifting bodies. This study analyzes the conventional and impulse forms of the forces on cascades of airfoils at spacings and pitch angles typical of wind turbine applications. OpenFOAM software was used to simulate steady, incompressible flow at a Reynolds number of 6×106 through cascades of NACA 0012 airfoils. The force equations agree well (less than 1% error) with the forces determined directly from OpenFOAM for four spacing ratios. We concentrate on the “wake vorticity” term, which is ignored in blade element momentum analysis. At a pitch angle of 90°, this term balances the viscous drag when the angle of attack is zero. At zero pitch, which models the outer region of a wind turbine blade at a high tip speed ratio, the term can account for 27% of the axial thrust when the angle of attack is about 4°. The normal force equation, like the angular momentum equation for wind turbines, has no viscous term, which forces the body drag to contribute to the circulation in the wake. It is shown that the airfoil assumption is conservative in that cascade elements have higher lift-to-drag ratios than airfoils at the same angle of attack. An associated result is that separation occurs at higher angles of attack on a cascade element compared to an airfoil.

Automated Identification of Failures in Doubly-Fed Induction Generators for Wind Turbine Applications

Remote, automated monitoring of wind generators is crucial considering that wind turbines are prone to failure due to the harsh operating environment, and difficult to access or test due to the remote location of wind turbines. The demand for condition monitoring of wind generators is increasing with the rapid growth in wind power generation. In this work, a new inverter-embedded off-line test concept for automated testing of doubly-fed induction generators (DFIG) is proposed for detection and classification of defects in the 1) slip ring-brush contact, 2) rotor winding turn insulation, and 3) stator core inter-laminar insulation. The main idea is to use the rotor side inverter for injecting test signals into the rotor winding for detecting asymmetry in the machine, whenever the DFIG is at standstill. The pattern of asymmetry in the equivalent impedance as a function of angle is analyzed for identifying the presence and type of DFIG fault at an early stage for efficient scheduling of maintenance. Experimental verification is given to show that the proposed test provides a simple means of identifying DFIG faults with high sensitivity and reliability without additional hardware.

A Comparison of Vacuum Infusion, Vacuum Bagging, and Hand Lay-Up Process on The Compressive and Shear Properties of GFRP Materials

Fiber-reinforced plastics are widely used in aerospace, marine, military, automotive, wind turbine, sports, and civil engineering applications. GFRP is a common material used in engineering applications such as for UAV structural material. Several techniques that can be used in the composite structure manufacturing process are HLU, VB, and, VARI. This paper studies the influence of the three manufacturing processes on the compressive and shear properties of GFRP composites. This study uses e-glass fiber as reinforcement material and a clear epoxy polymer called lycal as matrix material. The composites were manufactured by using HLU, VB, and VARI processes. The specimen dimensions, compressive, and shear tests are following ASTM standards. The microstructural characteristics were observed using a scanning electron microscope. The compressive strength of VARI composite is higher than HLU and VB composites up to 71% and 53%, respectively. The shear strength of the VARI composite is higher than HLU and VB composites up to 71% and 53%, respectively.

Epoxidized Malaysian Elaeis guineensis palm kernel oil trimethylolpropane polyol ester as green renewable biolubricants

Green renewable biolubricants base stock based on polyol triester of epoxidized Malaysian Elaeis guineensis palm kernel oil and trimethylolpropane was produced and optimized by D-optimal design of response surface methodology. The in-situ generated performic acid catalyst was used to epoxidize the palm kernel oil polyol triester (PKO-TMPE). The epoxidation process was improved and the subsequent epoxidized palm kernel oil-polyol triester (EPKO-TMPE) was assessed for its lubrication possessions. The optimal condition for the epoxidation process was attained at the unsaturation, hydrogen peroxide and formic acid molar ratios of 1.00: 7.67: 5.00, temperature of 51.85 °C with 1.62 h reaction time, respectively. High epoxide yield of 92.5% and 100.0% relative conversion oxirane with low iodine value of 0.40 g/100 g I2 of EPKO-TMPE was produced at the optimal condition. The resultant epoxidized polyol ester displayed respectable lubrication properties with high flash point at 335 °C and oxidative stability temperature at 278 °C, decent viscosity index of 187 and pour point at −19 °C. Tribological assessments exhibited that EPKO-TMPE has revealed small coefficient friction of 0.16 at 40 °C and 0.18 at 100 °C in the hydrodynamic region and equivalent with some marketable lubricants. The rheological investigations showed EPKO-TMPE can be classified as ISO VG 46 lubricant grade with decent lubrication possessions of Newtonian fluids. This renewable green industrial biolubricant is likely to be applicable for turbine, compressor fluids and hydraulic oil applications.