Search Results (84)

A gas turbine engine is a technological system consisting of a compressor, a combustion chamber, and other modules. All these components are subjected to dynamic and cyclic loads, which lead to fatigue cracks and mechanical damage. The aim of this work is to repair the worn surfaces of a series of DR-59L high-pressure turbine blades by laser powder cladding. A number of technological parameters of laser cladding were tested to obtain a defect-free structure on the witness sample. The metal powder of the cobalt alloy Stellite 21 was used as a filler material. By modeling the process of restoring rotor blades, the operating mode of laser powder cladding was determined. No defects were detected during capillary control of the restored surfaces of the rotor blades. The results of the uniaxial tension test of the restored rotor blades showed increased tensile strength and elongation. With the use of laser powder cladding technology, it was possible to restore the worn surfaces of a series of rotor blades of the DR-59L high-pressure turbine, thereby increasing the life cycle of power plant products. Full article

The refined aerodynamic design optimization of multistage compressors is a typical high-dimensional and expensive optimization problem. This study proposes an integrated surrogate model-assisted evolutionary algorithm combined with a Directly Manipulated Free-Form Deformation (DFFD)-based parametric dimensionality reduction method, establishing a high-precision and efficient global parallel aerodynamic optimization platform for multistage axial compressors. The DFFD method achieves a balance between flexibility and low-dimensional characteristics by directly controlling the surface points of blades, which demonstrates a particular suitability for the aerodynamic design optimization of multistage axial compressors. The integrated surrogate model enhances prediction accuracy by simultaneously identifying optimal solutions and the most uncertain solutions, effectively addressing highly nonlinear design space challenges. A three-stage axial compressor in a heavy-duty gas turbine is selected as the optimization object. The results demonstrate that the optimization task takes less than 48 h and achieves an improvement of 0.6% and 4% in the adiabatic efficiency and surge margin, respectively, while maintaining a nearly unchanged flow rate and pressure ratio at the design point. The proposed approach provides an efficient and reliable solution for complex aerodynamic optimization problems. Full article

Mesh adaptation techniques can significantly impact Computational Fluid Dynamics by improving solution accuracy and reducing computational costs. In this review, we begin by defining the concept of mesh adaptation, its core components and the terminology commonly used in the community. We then categorise and evaluate the main adaptation strategies, focusing both on error estimation and mesh modification techniques. In particular, we analyse the two most prominent families of error estimation: feature-based techniques, which target regions of high physical gradients and goal-oriented adjoint methods, which aim to reduce the error in a specific integral quantity of interest. Feature-based methods are advantageous due to their reduced computational cost: they do not require adjoint solvers, and they have a natural ability to introduce anisotropy. A substantial portion of the literature relies on second-order derivatives of scalar flow quantities to construct sensors that can be equidistributed to minimise discretisation error. However, when used carelessly, these methods can lead to over-refinement, and they are generally outperformed by adjoint-based techniques when improving specific target quantities. Goal-oriented methods typically achieve higher accuracy in fewer adaptation steps with coarser meshes. It will be seen that various approaches have been developed to incorporate anisotropy into adjoint-based adaptation, including hybrid error sensors that combine feature-based and goal-oriented indicators, sequential strategies and adjoint weighting of fluxes. After years of limited progress, recent work has demonstrated promising results, including certifiable solutions and applications to increasingly complex cases such as transonic compressor blades and film-cooled turbines. Despite these advances, several critical challenges remain: efficient parallelisation, robust geometry integration, application to unsteady flows and deployment in high-order discretisation frameworks. Finally, examples of the potential role of artificial intelligence in guiding or accelerating mesh adaptation are also discussed. Full article

The compressor blades of the gas turbine continually operate under extreme conditions, including elevated temperature, increased pressure, rapid rotation speed, and high-load environments, and are also subjected to complex vibrations, which inevitably lead to performance degradation and failures. Early fault warning based on historical operation data and real-time working conditions can enhance the safety and economy of gas turbines, preventing severe accidents. However, previous studies often faced challenges, such as a lack of fault data, imbalanced datasets, and low data utilization, which limited the accuracy of the algorithms. This study proposes a fault warning technique for gas turbine compressor blades based on AAKR-ACGAN. First, a digital twin model of the gas turbine is constructed using long-term operation data and simulation data from the mechanism model. Then, an auto-associative kernel regression (AAKR) model is used for the fault warning, monitoring multiple parameters to provide effective early warnings of potential faults. Additionally, an auxiliary classifier generative adversarial network (ACGAN) is employed to fully extract hidden data features of the fault points, balance the dataset, and accurately simulate the process of fault occurrence and development. The proposed approach is utilized for the early detection of faults in the compressor blades of a high-capacity gas turbine, and its precision and applicability are confirmed. The multisource early warning indicator can provide an early warning of a failure up to one year in advance of its occurrence. It was also able to detect a severe surge that occurred six months before the failure, which is speculated to be one of the causes that led to the failure. Full article

In aerospace applications, engine parts, especially those around the rotor blade tips, are coated with an abradable seal, a specific material layer. Its design produces a tighter seal without harming the blades by allowing it to wear down or “abrade” somewhat when the blade tips come into contact. In turbines and compressors, this reduces gas leakage between high- and low-pressure zones, increasing engine efficiency. Abradable seals are crucial to contemporary jet engines because they enhance performance and lower fuel consumption. The materials selected for these seals are designed to balance durability and abrasion resistance under high temperatures and speeds. Metal matrix, oxide particles, and porosity are the three most prevalent phases. An ideal mix of characteristics, such as hardness and erosion resistance, determines how effective a seal is, and this is accomplished by keeping the right proportions of elements in place throughout production. The primary objective of this research is to optimize abradability by utilizing various FEM tools to simulate the rub rig test and modify testing parameters, including Young’s modulus, yield stress, and tangent modulus, to analyze their impact on the wear behavior of the abradable seal and blade. Two microstructure models (CoNiCrAlY–BN–polyester coating) were found to perform optimally at porosity levels of 56% and 46%, corresponding to hardness values of 48 HR15Y and 71 HR15Y, respectively. Changing factors like yield stress and tangent modulus makes the seal more abrasive while keeping its hardness, porosity, and Young’s modulus the same. Furthermore, altering the Young’s modulus of the shroud material achieves optimal abradability when tangent modulus and yield stress remain constant. These findings provide valuable insights for improving material performance in engineering applications. To improve abradability and forecast characteristics, this procedure entails evaluating the effects of every single parameter setting, culminating in the creation of the best abradable materials. This modeling technique seems to provide reliable findings, providing a solid basis for coating design in the future. Full article

The axial compressor is crucial for heavy-duty gas turbines, with its aerodynamic performance directly affecting efficiency. The current trend in the development of these compressors is to increase the stage load and efficiency, thereby achieving a higher pressure ratio with fewer stages. The aerodynamic characteristics of a 1.5-stage axial compressor from a 300 MW F-class heavy gas turbine at three different rotation speeds (100%, 90%, and 80%) were studied. Specifically, the distribution of the inlet Mach number, shock wave structures, isentropic Mach number of blade surface, and blade surface separation flow characteristics under three typical working conditions, at the near stall (NS) point, maximum efficiency (ME) point, and near choke point (NC), were discussed. The results indicate that at 80% rotational speed, 70~100% spanwise of the compressor rotor blade is operated under the transonic zone. Meanwhile, at 100% rotational speed, almost all the spanwise of the compressor rotor blade is operated under the transonic zone. Furthermore, compared to the detached shock wave observed under the NS condition, the normal passage shock wave observed under the NC condition exhibits more significant changes in shock intensity and shock pattern. Full article

Turbomachinery engines face significant failure risks due to the combination of thermal loads and high-amplitude vibrations in turbine and compressor blades. Accurate stress distribution measurements are critical for enhancing the performance and safety of these systems. Blade tip timing (BTT) has emerged as an advanced alternative to traditional measurement methods, capturing blade dynamics by detecting deviations in blade tip arrival times through sensors mounted on the stator casing. This research focuses on developing an analytical model to quantify the uncertainty budget involved in designing a calibration setup for BTT systems, ensuring targeted performance levels. Unlike existing approaches, the proposed model integrates both operational variability and sensor performance characteristics, providing a comprehensive framework for uncertainty quantification. The model incorporates various operating and measurement scenarios to create an accurate and reliable calibration tool for BTT systems. In the broader context, this advancement supports the use of BTT for qualification processes, ultimately extending the lifespan of turbomachinery through condition-based maintenance. This approach enhances performance validation and monitoring in power plants and aircraft engines, contributing to safer and more efficient operations. Full article

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. Full article

In this study, a thorough experimental investigation of the synchronous blade vibrations of a radial turbine is performed for different IGV configurations. First, the blade modes are measured experimentally and calculated numerically. Subsequently, the vibrations are recorded with two redundant measurement systems during real operation. Strain gauges were applied on certain blades, while a commercial blade-tip-timing system is used for the measurement of blade deflections. The experimentally determined vibration properties are compared with numerical estimations. Initially, the vibrations recorded with the “nominal” IGV were presented. This IGV primarily generates nodal diameter (ND) 0 vibrations. Subsequently, the impact of two different IGV configurations is examined. First, a mistuned IGV, which has the same number of vanes as the “nominal” IGV is examined. By intentionally varying the distance between the vanes, additional low engine order excitations are generated. Moreover, an IGV with a higher number of vanes is employed to induce excitations at higher frequency modes and ND6 vibrations. Certain vibrations are consistently measured across all IGV configurations, which cannot be attributed to the spiral turbine casing. In addition, a turbine–compressor interaction has been observed. Full article

Titanium alloys are widely used in the manufacture of gas turbines’ compressor blades. Elucidating their mechanical behavior and strength under damaged conditions is the key to evaluating the equipment’s reliability. However, the conventional Johnson-Cook (J-C) constitutive model has limitations in describing the dynamic response of titanium alloy materials under the impact of a high strain rate. In order to solve this problem, the mechanical behavior of a TC4 titanium alloy under high strain rate and different temperature conditions was analyzed by combining experiments and numerical simulations. In this study, the parameters of the J-C model were analyzed in detail, and an improved J-C constitutive model is proposed, based on the new mechanism of the strain rate strengthening effect and the temperature softening effect, which improves the accuracy of the description of strain sensitivity and temperature dependence. Finally, the VUMAT subroutine of ABAQUS software was used for numerical simulation, and the predictive ability of the improved model was verified. The simulation results showed that the maximum prediction error of the traditional J-C model was 23.6%, while the maximum error of the improved model was reduced to 5.6%. This indicates that the improved J-C constitutive model can more accurately predict the mechanical response of a titanium alloy under an impact load and provides a theoretical basis for the study of the mechanical properties of titanium alloy blades under subsequent conditions of foreign object damage. Full article

According to the characteristics of the rotor system in an aero-engine and the vibrational test requirements of the aero-engine ground test, suitable vibration measurement sensors and test positions were selected. The vibration signals at the casings for the compressor and turbine of a twin-spool turbo-jet engine were collected under the states of maximum power and afterburning respectively, and the power spectrum analysis was carried out to determine the positions and causes of vibration. Furthermore, methods and preventive measures for eliminating vibration have been proposed. The results indicated that the main rotor vibration excited by mass imbalance in the twin-spool turbo-jet engine was significant. Rotor spindle misalignment or rotor radial stiffness unevenness also induced the vibration. The aerodynamic pulse vibration formed by the rotor blades of the first stage of the low pressure compressor was large, and rub induced vibration fault may occur at the turbine rotor seals. Based on the power spectrum analysis technology, the rotor system faults information including the type, position, and the degree can be quickly identified, and useful attempts and explorations have been made to reduce the vibration faults of the twin-spool turbo-jet engine. Full article

A neural network method has been developed for helicopter turboshaft engine residual life determination, the basis of which is a hierarchical system, which is represented in neural network model form, consisting of four layers, which determines the numerical value of the residual life. To implement a hierarchical system, a justified multilayer perceptron is used. A multilayer perceptron training algorithm has been developed, which, by introducing an initial parameter to the output layer, yields a prediction accuracy of up to 99.3%, and the adaptive Adam training rate ensures an accuracy of up to 99.4% in helicopter turboshaft engine residual life determination. A method for constructing a degradation curve has been developed that takes into account both the parameter predictions and similarities with past patterns, allowing you to determine the range of possible values of the residual life estimate, with a probability of up to 95%. The article considers an example of solving the task of determining the thermally stressed state of helicopter turboshaft engine compressor turbine blades and assessing their residual life. A computational experiment was carried out to determine the residual life of helicopter turboshaft engine compressor turbine blades, and the results, with 160 training epochs, recorded an accuracy of 99.3%, with a reduction in losses from 2.5% to 0.5% thanks to training process optimization by applying an adaptive training rate. The comparative analysis results showed that use of the multilayer perceptron as a hierarchical system gives better results than the classical RBF network and the least squares method. The first and second types of error were reduced by 2.23 times compared to the RBF network and by 4.74 times compared to the least squares method. Full article

Precise electrochemical machining (PECM) is being used increasingly to produce turbine blades (high-pressure compressors) from difficult-to-machine materials such as Inconel. However, the challenges associated with PECM are particularly pronounced for filigree workpieces characterized by high aspect ratios and thin-walled geometries. The need for high-pressure flushing within the working gap to renew the electrolyte poses a dilemma because it induces unwanted deflection in these thin-walled structures. This problem is intensified by the mechanical oscillation of the tool applied to promote flushing efficiency. The superposition of mechanical tool oscillation and turbulent flushing, which exacerbate fluid–structure interaction, has been identified as the essential cause of workpiece deflection. The aim of this paper is to present an experimental setup coupled with numerical methods to better investigate the phenomenon of workpiece deflection during PECM. In the first part of this work, a novel tool system for investigating the phenomenon of workpiece deflection in PECM is presented. The tool system combines typical PECM tool–workpiece arrangements for double-sided machining and a unique electrolytic mask that provides optical access to the working gap, allowing in situ measurements. After validating the tool system by experimental tests, the workpiece deflection is investigated using high-speed imaging. In a next step, analytical studies of the flushing conditions during machining operations are carried out. These investigations are followed by a structural investigation of the workpiece to improve the understanding of the deflection behavior of the workpiece. In addition, the effect on the blade tip caused by the continuously decreasing moment of inertia of the blade due to their thinning during machining is analyzed. Full article

Pump–turbine units with high heads are subjected to strong pressure pulsations from the unsteady transient flow in fluid channels, which can produce severe vibrations and high stresses on the pump–turbine structural components. Therefore, reducing transient flow-induced stresses on prototype reversible pump–turbine units is an important measure for ensuring their safe and efficient operation. A high-head prototype reversible pump–turbine with a rated head of 440 m was used to investigate the transient flow characteristics and the flow-induced-stresses in this study. First, the flow passages of the pump–turbine unit and the structure of the reversible pump–turbine runner were constructed with CAD tools. Next, CFD simulations at the full load were performed to investigate the pressure pulsation characteristics of the pump turbine in both the time domain and the frequency domain. After this, the pressure files calculated by the CFD were exported and applied to a finite element model of the pump–turbine runner to calculate the transient flow-induced dynamic stresses. The results show that the pressure pulsations in the flow passage are closely related to the rotational speed, the guide vane number, and the runner blade number of the pump–turbine unit. The maximum flow-induced stresses on the pump–turbine runner at the full load were below 2 MPa and lower than the allowable value, which reveals that the designs of the pump–turbine runner and the flow passage are acceptable. The conclusions can be used as a reference to evaluate the design of high-head pump–turbines units. The approaches used to carry out the transient flow-induced stress calculations can be applied not only to pump–turbines units but also to other types of fluid turbomachinery such as pumps, turbines, fans, compressors, turbochargers, etc. Full article

The compressor serves as a crucial component that influences the performance of the gas turbine engine. Researchers have been endeavoring to explore compressor types that possess a high loading level and high-efficiency characteristics concurrently. In this study, tandem blade technology was applied to a transonic ultra-highly loaded axial compressor, and the Baseline single-blade rotor was replaced by a tandem rotor to take into account the loading level and compressor performance. Detailed investigations were carried out to identify the effects on the aerodynamic performance of the ultra-highly loaded stage and the fundamental flow mechanism within the tandem-rotor stage. This paper presents original design maps for the tandem-rotor stage, and the selection criteria for tandem parameters in tandem-rotor stage are refined. The results indicate that the peak efficiency improved by 0.83%, the stall margin increased by 2.16%, and the choke flow rate rose by 0.30% for the optimal tandem-rotor configuration. The meridional division position of the rotor primarily affects the ratio of loading of the front and rear blades, while the circumferential relative position of the tandem rotor mainly influences the channel types formed by the front and rear blades. Larger values for the meridional division position parameter and smaller values for circumferential relative position parameter should be selected for the tandem rotor design to optimize both the isentropic efficiency and total pressure ratio. This investigation offers the theoretical foundation for the design of a transonic ultra-highly loaded tandem-rotor compressor. Full article