Stage Blade Research Articles

Targeting Full-Hydrogen Operation on Industrial-Scale Gas Turbines: Impact of Unconventional Fuels on Turbine Module Performance and Aeromechanics

Abstract With the trend to full decarbonization, a full hydrogen economy development is a key industrial objective. Gas turbines, currently one of the cleanest fossil fuel-based power generation solutions, provide reliable and on-demand power. The introduction of hydrogen into the fuel mix of existing gas turbines represents a solution with great potential to provide low-carbon or even carbon-free energy. High-hydrogen content fuels, however, challenge the efficient operation of the gas turbine expander, as crucial aspects such as increased flow rate, different gas properties and temperature operating range may affect performance and structural integrity. To evaluate the impact of this conversion, a numerical investigation of five cases with increasing percentages of hydrogen in the fuel was carried out for an industrial four stages gas turbine module. The variation of turbine inlet temperature distribution from combustion chamber was considered, to assess the impact of the unconventional fuel on the well-known aeromechanical behavior of the last stage blades. Variations in capacity, efficiency, power and potential limits due to aeroelasticity were evaluated, identifying the most relevant differences with respect to the full methane case. All these analyses confirm the possibility to employ high-hydrogen fuel operation in a current gas turbine without the need of a further redesign, while maintaining acceptable performance levels.

Development and Assessment of a Miniaturized Test Rig for Evaluating Noise Reduction in Serrated Blades Under Turbulent Flow Conditions

The implementation of serrated stator blades in axial compressor and fan stages offers significant advantages, such as enhanced performance and reduced noise levels, making it a practical and cost-effective solution. This study explores the impact of serrated blade design on noise reduction under specific engine operating conditions. A small-scale experimental test setup with a turbulence-inducing grid was designed for testing multiple grid sizes in order to identify the most promising configuration which replicates rotor–stator interaction. Numerical simulations and early experimental tests in an anechoic chamber using a four-blade cascade configuration at an airflow speed of 50 m/s revealed a small but notable noise reduction in the 1–6 kHz range for a partially matched grid–blade geometry. Serrated blades demonstrated an overall sound pressure level reduction of 1.5 dB and up to 12 dB in tonal noise, highlighting the potential of cascade configurations to improve acoustic performance in gas turbine applications.

Effect of Blade Material of Steam Turbine Rotor on Aeroelastic Characteristics

Elements of powerful steam turbines are subjected to significant unsteady loads, in particular the rotor blades of the last stages. These loads, in some cases, can cause self-excited oscillations, which are extremely dangerous and have a negative impact on the efficiency and service life of the blade cascade. Therefore, when designing new or modernizing existing steam turbine stages, it is recommended to study the aeroelastic characteristics of the blades. The conditions for the occurrence of self-excited oscillations are influenced by both the geometric characteristics and the alloy from which the blade is made. To determine the effect of the blade material on the aeroelastic behaviour, a numerical analysis of the aeroelastic characteristics of the last stage blades made of steel and titanium alloy was performed. For the analysis, the method of simultaneous modeling of unsteady gas flow through the blade cascades and elastic vibrations of the blades (coupled problem) was used, which allows obtaining the amplitude-frequency spectrum of the interaction of unsteady loads and blade vibrations. The paper presents the results of numerical analysis for harmonic oscillations with a given amplitude and a given inter-blade phase angle, as well as for the regime of coupled vibration of blades under the action of unsteady aerodynamic forces. The dependences of the aerodamping coefficient on the inter-blade phase angle and the distribution of the coefficient along the blade are presented. The results of modeling the coupled vibration of the blades for the first six natural forms are presented in the form of a time-evolving displacement of the blade peripheral section, as well as forces and moments acting on the peripheral section. The corresponding amplitude-frequency spectra of displacements and loads in the peripheral section are also presented. The analysis of the results showed an insignificant difference in the characteristics of the proposed blade materials. For the first natural form of blade oscillations, the possibility of self-excited oscillations was found, and for the second form, there are conditions for the appearance of stable self-oscillations.

Sensitivity analysis of turbine stage aerothermal characteristics and blade cooling performance considering combustor swirl and hot spot

This paper investigates the global sensitivity of high-pressure-turbine (HPT) first stage cascades aerothermal characteristics and blade cooling performance under the influence of combustor swirl and hot spot. The combustor outflow conditions impact on turbine working performance and robustness. This paper is focused on the influence of uncertain combustor swirling flow and hot spot, rather than deterministic working conditions. A simplified combustor outflow simulation method is firstly proposed, and the effects of combustor outflow are quantified by combining chaos polynomial expansion with Sobol’ decomposition method. The results show that different rotating directions of the swirl lead to restricted influences on the averaged aerothermal performance of the turbine stage, but significantly affects its robustness. The positive swirl increases the total pressure loss generated by the lower passage vortex of the stator cascade, and the high uncertainty region of the stator cascade total pressure loss profile is the combined products of the residual swirl and the interaction between the passage vortex and mainstream. The total pressure loss of the rotor cascade due to leakage vortex has low sensitivity to the hot spot and swirl strength, while the total pressure loss generated by the passage vortex is affected by hot spot temperature. Temperature distribution affected by the passage vortex is sensitive to swirl strength. Generally, uncertainty variance of stage aerothermal parameters with positive swirl is about 30% larger than that of the negative case, since the positive swirl has stronger interactions with the blades, leading to more significant uncertainty. However, the averaged heat transfer coefficients with positive swirl are 37% less sensitive, compared to the negative swirl case. The results give better understanding on the influence mechanisms of turbine inflow conditions, emphasize the meaning of investigating uncertain characteristics of the turbine cascades. Investigations of this article provide reference for robust turbine blade cooling design.

Structural Analysis & Effect of Impingement Cooling Flow in the Internal Surface on Temperature Distribution of a Vane in Gas Turbine Using Taguchi Technique

Abstract: Gas turbine always consider one of the most important systems in the modern engineering applications, because it has continuous ability to generate electric power. In gas turbines the major portion of performance dependency lies upon turbine blade design ,the blades are considered one of the important and expensive parts in the gas turbines , where the blades of first stage from failure .The blades of the gas turbine suffer from tensile stresses due to centrifugal forces resulting from the high rotational speed and because of the loading of densegasses at a high temperature and speed ,as the centrifugal force is one of the problems that thedesigner of the turbine blades faces , as the designer aims to reduce stresses within the permissible limit. CFD study was carried out for evaluating the performance of a utility Steam Turbine. The flow in a turbine blade passage is complex and involves understanding of energy conversion in three dimensional geometries. The performance of turbine depends on efficient energy conversion and analyzing the flow path behavior in the various componentsof Steam Turbine. This study seeks the optimization of an axial turbine from a small gas turbine engine developed by ITA using Computational Fluid Dynamics (CFD) and Multi- Objective Optimization techniques focused on geometry changes to maximize the turbine performance. The simulation process will be done through the use of the commercial software SolidWorks.

Fracture Analysis and Repair of Last Stage Blade Reinforcement Boss for Low Pressure Cylinder Rotor of 330 MW Unit

The lace convex table of the final stage blade of a 330 MW turbine fractured. The reason was analyzed by fracture analysis, chemical composition analysis and metallographic analysis. It showed that the overload was the main reason for the fracture. Deformation of guide ring caused by fracture of guide ring bolt was the main reason of the overload. The analysis of the guide ring bolt showed that the brittleness of the guide ring bolt was the main reason for its fracture. It was suggested to strengthen the supervision of the manufacturing process of the guide ring bolt. The lace convex table was repaired by surfacing welding. A reasonable welding process was developed and the repair was successful.
 Abstract, Final stage blade, Lace convex table, Surfacing welding, Welding repair

Unsteady Flows and Component Interaction in Turbomachinery

Unsteady component interaction represents a crucial topic in turbomachinery design and analysis. Combustor/turbine interaction is one of the most widely studied topics both using experimental and numerical methods due to the risk of failure of high-pressure turbine blades by unexpected deviation of hot flow trajectory and local heat transfer characteristics. Compressor/combustor interaction is also of interest since it has been demonstrated that, under certain conditions, a non-uniform flow field feeds the primary zone of the combustor where the high-pressure compressor blade passing frequency can be clearly individuated. At the integral scale, the relative motion between vanes and blades in compressor and turbine stages governs the aerothermal performance of the gas turbine, especially in the presence of shocks. At the inertial scale, high turbulence levels generated in the combustion chamber govern wall heat transfer in the high-pressure turbine stage, and wakes generated by low-pressure turbine vanes interact with separation bubbles at low-Reynolds conditions by suppressing them. The necessity to correctly analyze these phenomena obliges the scientific community, the industry, and public funding bodies to cooperate and continuously build new test rigs equipped with highly accurate instrumentation to account for real machine effects. In computational fluid dynamics, researchers developed fast and reliable methods to analyze unsteady blade-row interaction in the case of uneven blade count conditions as well as component interaction by using different closures for turbulence in each domain using high-performance computing. This research effort results in countless publications that contribute to unveiling the actual behavior of turbomachinery flow. However, the great number of publications also results in fragmented information that risks being useless in a practical situation. Therefore, it is useful to collect the most relevant outcomes and derive general conclusions that may help the design of next-gen turbomachines. In fact, the necessity to meet the emission limits defined by the Paris agreement in 2015 obliges the turbomachinery community to consider revolutionary cycles in which component interaction plays a crucial role. In the present paper, the authors try to summarize almost 40 years of experimental and numerical research in the component interaction field, aiming at both providing a comprehensive overview and defining the most relevant conclusions obtained in this demanding research field.

Cooling Efficiency of a NACA4412 airfoil: Numerical application

The temperatures imposed on the blades of the first stages of turbines are generally very high; these expose the latter to harmful thermal effects, pushing manufacturers to continually improve techniques for cooling the blades. It is true that by increasing the temperature of the gases at the inlet of the turbines, we increase the efficiency, the performance of the machines, and we improve the power and fuel consumption with a significant reduction in polluting gases. Thus, the current general trend among manufacturers is to design machines that operate at increasingly high inlet temperatures. This has led, therefore, to the constant search for new materials with high thermal resistance and to constantly improve cooling techniques. This task is conditioned by a good and deep understanding of the phenomenon of heat transfer in turbine blades. This study examines the three dimension numerical simulation of the flow and heat exchange inside an internal cooling channel of a gas turbine blade with the profile of NACA 4412. This channel plays an important role in increasing heat exchange between the cooling air and the walls of the blade. In the turbulent regime, we have investigated the cooling of a profile blade NACA 4412 using forced convection (V = 200, 250, 300, 350, and 400 m / s). determined that the value of the cold air's speed increases with the intensity of the secondary flow inside the morning. Results found that, The flow dynamics and kinematics of fluid particles alter significantly when the cooling air speed is increased, and the cooling level is enhanced.

Prolongation of Safe Operation of the K-1000-60/3000 Turbine Power Unit after Damage to the HPC Rotor

Currently, when large-scale military actions are taking place on the territory of Ukraine, the inclusion of the domestic energy system in the European one is a reliable component of providing electricity to the country's energy market. However, according to experts, uninterrupted and safe operation of nuclear power plants is still considered a prerequisite for the stable operation of the energy sector of Ukraine. The purpose of the paper is to assess the damageability and individual resource of the rotor of high-pressure cylinder (HPC) of the K-1000-60/3000 turbine power unit of the LMZ after damage to the blades in order to prolong the operation of the power unit in the conditions of a stressed state of the power system. One of the most effective ways to partially solve the problem of replacement of generating capacities is to extend the operating periods of NPP power units after the end of the project operating period, provided that nuclear and radiation safety standards are met. The review of the previously established service life of the energy equipment of NPP power units involves the assessment of the residual resource of the energy equipment in accordance with the regulatory documents. After the accidental damage of the blades of the last stage of the HPC rotor of the K-1000-60/3000 turbine power unit of the LMZ, there was a need to study the cyclic and static damage, the individual residual resource of the HPC rotor. In the process of achieving the goal, studies were carried out for three design options: the original option (five stages of the HPC rotor), the option without the blades of the last stage and the option without the fifth stage (with four first stages). The calculation of the resource indicators of the rotor in the execution of the HPC without blades of the 5th stage shows that the static damage accumulated in the main metal is 52%, the cyclic damage is 5% when applying the standard strength reserves for the number of cycles and for deformations at the level of nN=10 and nε=1.5 according to the recommendations of SOU-N MEV 40.1-21677681-52:2011. Thus, the total damage to the base metal is 57%, which sets the residual resource of the HPC rotor at the level of 88.4 thousand hours. The calculation of the resource indicators of the rotor in the execution of the HPC without entire 5th stage shows that the static damage accumulated in the base metal is 52%, the cyclic damage is 6% when applying the standard strength reserves for the number of cycles and deformations at the above-mentioned level. The total damage to the base metal is 58%, which determines the residual resource of the HPC rotor at the level of 85.6 thousand hours.

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Low cycle fatigue behavior and life prediction of a directionally solidified alloy

Investigations on affinity law under gas–liquid conditions in multistage radial and mixed-flow multiphase pumps

Affinity laws have been widely used in pump design and simulation under high-temperature and corrosive conditions. By applying such laws, it is possible to shorten development cycles and reduce test costs. However, current applications of affinity laws are still limited to liquid conditions. In this paper, expressions for affinity laws and their applicability are investigated for multistage radial and mixed-flow multiphase pumps under gas–liquid conditions. A high-pressure (30 MPa) gas–liquid experimental platform is constructed, and three-stage and 25-stage radial pumps and a 15-stage mixed-flow pump are investigated, with specific speeds of 107 and 216. With gas compressibility taken into account, the gas–liquid two-phase flow rate, head, and power, and the corresponding dimensionless hydraulic coefficients, are defined for multiphase pumps. The deterioration of gas–liquid pressurization performance is found to be divided into three processes with different dynamic mechanisms, corresponding to three flow patterns. The inlet gas volume fraction of pump is used to judge dynamic similarity. At the same inlet gas volume fractions λ1 = λ2, when the gas–liquid flows in two pumps have the same flow pattern, dynamic similarity will be satisfied. The affinity law that is established shows good applicability to the three-stage radial multiphase pump, with goodness of fit R2 larger than 0.9 for the two-phase Ψm–Φm and Πm–Φm performance curves. Finally, experimental results indicate that the affinity law also has good applicability to multiphase pumps with different stage numbers and blade structures under gas–liquid conditions.

Analysis of the thermal insulation performance of turbine blade thermal barrier coatings considering inlet non-uniformity

The gases discharged from the new generation of lean-burn combustors usually have hot streaks (HS) and swirls. The thermal performance of rotor thermal barrier coatings (TBCs) exhibits significant non-constant behavior due to inlet non-uniformity and blade row interaction. To investigate the non-constant thermal insulation performance of the blade TBCs, non-constant numerical simulations were carried out for the first stage vane and blade of the High-pressure turbine of the GE-E3 engine. The normalized temperature results for the HS and the combination of HS and swirl cases were compared with the uniform inlet case to investigate the effect of inlet non-uniformity on the surface temperature and thermal insulation effect of the blade TBCs. The results show that a credible investigation of rotor TBCs should consider the unsteady blade row interaction. HS causes high-temperature hot spots on the surface of the TBCs and redistributes them with the change in the direction of the swirl. HS and swirl significantly reduce the turbine blade cooling effectiveness and thermal insulation effectiveness of TBCs. The lowest overall cooling performance of the blades was observed during the 1/4 T stator period. The added swirl reduces the insulation effectiveness's fluctuation value by reducing positive swirl (PSW) by 52.6 % and negative swirl (NSW) by 57.8 %. Therefore, applications and designs of TBCs should consider the effects of HS and swirl.

Development of last stage blade of 13K215 turbine intermediate pressure module

Development of last stage blade of 13K215 turbine intermediate pressure module

Changes in the Thermal and Stress-Strain State of the HPC Rotor of a Powerful NPP Turbine after the Blades Damage

In practice, during the operation of steam turbines, accidental damage to the blades of the rotors and stators of powerful steam turbines occurs. The main causes of emergency stops of steam turbines were vibration fatigue of the blades material, erosive damage to the blades body, and resonance problems during the power equipment operation. Based on this study, the assessment of changes in the thermal and stress-strain state of power equipment elements, which at nuclear power plants significantly affect the continued operation of the turbine after its damage, are quite relevant. Changes in the thermal and stress-strain state, which may occur after damage to the rotor of high-pressure cylinder (HPC rotor) of the K-1000-60/3000 turbine power unit of the LMZ in the station conditions, have been considered and analyzed and will provide an opportunity to assess the individual resource and continue the power unit operation. In the calculated assessment of changes in the thermal and stress-strain state of the HPC rotor, taking into account the data of the technical audit regarding damage, a geometric model of the rotor was created. Studies were conducted for three options of designs: the original option (five stages of the HPC rotor), the option without the blades of the last stage and the option without the fifth stage (with four first stages). For the project design, when working at the nominal parameters of the steam, the most stressed areas are the unloading holes of the 5th stage (σi=202.8 MPa), axial hole of the rotor in the area of the 5th stage (σi=195.2 MPa), as well as the 5th-degree welding fillet from the side of the end seals (σi=200.3 MPa) and unloading holes of the 4th and 3rd stages with a stress intensity of about 170–185 MPa. The high values of the stress intensity in the area of the 5th stage can be explained by the significant concentration of the mass of both the stage itself and its blades, which provoke significant centrifugal forces when working at the nominal rotation frequency. For a HPC rotor without blades of the 5th stage, there is a shift of the maximum stress intensity to the area of the unloading holes of the 4th and 3rd stages, as well as the axial hole of the shaft under the same stages. The maximum stress value is σi max=184.8 MPa. At the same time, the intensity of stresses in the area of unloading holes of the 5th degree decreased almost by half, to the level of 124 MPa.

Использование мультифазных коэффициентов для анализа и совершенствования конструкций лопастных машин, работающих на газожидкостных, парожидкостных смесях, смесях из жидкости и твердых частиц

To increase the oil recovery factor, the bottom-hole pressure is reduced, which is accompanied by an increase in the free gas and mechanical impurities content at the pump inlet. As a rule, the serial equipment is not providing reliable and efficient operation in such conditions. In oil producing wells with the high free gas content, efficiency of the multiphase modules blade stages could be increased by correct selection of the serial equipment and introduction of the new design solutions. The paper analyzes specifics of the gas-liquid mixture flow in the flow path of the blade multiphase stages pumping the gas-liquid mixtures. Recommendations are provided for improving the flow path taking into account the multiphase specific speed coefficient formula. It is proposed to use the multiphase coefficient along with the cavitation specific speed coefficient in development of the blade pumps operating under the steam cavitation conditions.

Finite Element Simulation and Stress Analysis of Gas Turbine Blade Due to Centrifugal Force

Gas turbine always consider one of the most important system in the modern engineering applications, because it has continuous ability to generate electric power. In gas turbines the major portion of performance dependency lies upon turbine blade design ,the blades are considered one of the important and expensive parts in the gas turbines , where the blades of first stage from failure . Most studies indicate that 50% of failure and breakage accidents cannot be accurately determined due to the large number of variables .The blades of the gas turbine suffer from tensile stresses due to centrifugal forces resulting from the high rotational speed and because of the loading of dense gasses at a high temperature and speed ,as the centrifugal force is one of the problems that the designer of the turbine blades faces , as the designer aims to reduce stresses within the permissible limit . The current work is concerns with study and analysis of the stresses at the first stage blades in Al Mosul power station at Mosul city, AUTOCAD which is computer program has been an efficient software to draw and specify blade dimensions at the exact measurement, as well as the ANSYS 21 software program was also used as an effective tool in determining the stresses and deformation under the influence of centrifugal force. As the blade was considered root bound in all direction (X, Y and Z) and adding the special mechanical properties of (INCONEL738 alloy), After conducting a stress analysis in the program, it was found that the stress values of the posterior and anterior edge of the blade root region were high and these results were validated with the results carried out by some studies that dealing with study and analysis of the blades at the first stages in turbine stations. The static and modal analysis of the turbine blade is being considered. To analyze these aspects, the blade is represented using the 3D-Solid Brick element. The blade's geometric model is created by generating and then extruding them to form a solid model. An analytical approach is utilized to estimate the centrifugal forces. The objective of this presented work is to investigate the impact of mechanical analysis on the structure of gas turbine blades. The findings indicate lower levels of mechanical stress.

Investigation of structural-phase transformations in a foundry structural alloy based on Ni3Al intermetallic compound after high-temperature exposures and during the operation of the alloy as a nozzle blade

The paper presents studies of structural and phase transformations in intermetallic compositions based on the Ni3Al compound depending on alloying and high-temperature treatments, carried out in the process of creating a cast structural alloy for operation in the temperature range of 900–1200°C. Experimentally, when testing the developed intermetallic alloy as nozzle blades of the 1st stage of a high-pressure turbine, it was confirmed that the alloy is thermally stable at temperatures up to 1200°C.

Searching for Possible Design Solutions to Extend the Service Life of the HPC of a Powerful NPP Turbine after Damage to the Rotor Blades

The aim of this research was to analyze and evaluate possible design solutions for the flow path of the high-pressure cylinder (HPC) of the K-1000-60/3000 turbine and the possibility of their short-term implementation in a nuclear power plant after an accidental destruction of the working blades of the last stage of the HPC in conditions of the shortage of generating capacities and a tense operation state of the power system. To achieve the set goals, an appropriate methodology was developed; a mathematical model of thermo-and gas dynamic processes in the flow path of a steam turbine was improved. To make appropriate decisions on changing the design of the turbine, the necessary computational studies of the HPC of the K-1000-60/3000 turbine of the designed structure, the structure without rotor blades of the 5th stage and the structure with four first stages (without the fifth stage) were carried out for both turbine steam flows. The results of the study of thermo- and gas dynamic parameters of the flow showed the presence of differences in the operating conditions of all turbine stages, and these are the most significant for the 4th and 5th stages. A significant redistribution of thermal differences in the stages, and a decrease in the internal power of the HPC of the turbine by 35.5 MW and 6.6 MW respectively, as well as a decrease in their internal efficiency by 11.8 % and 2.1 %, respectively, were noted. Taking into account all the aspects related to the operation of the power unit, the most successful solution for the rapid resumption of operation of a powerful turbine plant used by a nuclear power plant after an accidental damage to the working blades is a HPC design without the working blades of the fifth stage. It is planned to carry out additional studies of the HPC design by replacing the nozzle apparatus of the fifth stage with an appropriate simulator.

Study on Fracture Mechanism of Low-Pressure Blades of Steam Turbines in Power Plants

With the continuous improvement of steam turbine design technology and production level, steam turbine blade fracture accidents have dropped significantly, and blade fracture accidents are no longer the main reason for the forced shutdown of thermal power generation units. Due to the bad working conditions of turbine blades, blade designers still need help to accurately analyze their dynamic stress and evaluate their high cycle fatigue life. Up to now, blade fracture accidents still occur frequently. In this paper, a comprehensive analysis is made of the causes of the fracture of the low-pressure 16th stage blade of a 25 MW steam turbine in a thermal power plant. The fracture property of turbine moving blades is that small corrosion pits are formed first, and then the fatigue propagation fracture occurs. The main cause of corrosion is poor steam quality.

Corrosion of Potential First Stage Blade Materials in Simulated Supercritical CO2

ABSTRACT Global power consumption is predicted to double by 2050, notably driven by the transportation and energy sectors necessitating limitations of emissions. Due to its compact turbomachinery, better thermal efficiency, and simpler layout, supercritical-CO2 cycles have received attention, with numerous variations proposed (either indirect-fired/closed cycles or direct-fired-open cycles). One technical challenge is degradation pathway quantification of turbine materials in sCO2 as selection is crucial to successfully and economically operate new plants. This requires degradation assessment in representative environments simulating the Allam cycle. Laboratory tests were conducted on a first stage turbine blade alloy, CM247, with either an environmentally resistant coating or bond coat/thermal barrier coat at one atmosphere and 800°C, with potential exposure including (O2, H2O, N2, SO2) for up to 1000 h. Weight change and metallographic measurements tracked scale development. Scanning electron microscopy/energy dispersive X-ray spectroscopy studied scales and internal precipitates. Locations of contaminant element in the CO2-rich environment were investigated.