Aero-engine Fan Research Articles

Experimental Study on Ice Shedding Behaviors for Aero-Engine Fan Blade Icing during Ground Idle

Fan blade icing can affect efficiency and aerodynamic stability, and the shed ice may be sucked into the core of the engine, causing adverse effects or even damage to the compressor components. Ice accretion and shedding are among the key issues in engine design and tests. But they have not been clearly understood. In this work, ice shedding from rotating aero-engine fan blades during continuous icing is experimentally investigated under the relevant airworthiness requirements. The phenomena of icing and ice shedding under different ambient temperatures and engine speeds are recorded to obtain the ice-shedding time and the characteristic length of the residual ice. Force analysis is used to understand the corresponding behavior. The degree of ice-shedding balance Db is defined to explore the symmetry of ice shedding. The results show that the shedding time is significantly affected by the rotational speed, and the characteristic length will first shorten and then grow as the ambient temperature decreases. When the ice shedding is completed instantaneously, Db will show a violent shock. There is a critical ambient temperature, below which the ice accretion will worsen significantly as temperature decreases. For aero-engine fan blade icing tests during ground idle, the critical ambient temperature ranges from −5 ∘C to −9 ∘C. In order for the ice to shed faster, the engine speed has to reach a threshold. This study can shed light on the preliminary characteristics of ice shedding from rotating components and provide guidance and a data basis for the numerical simulation of fan blade icing and the design of an aero-engine.

Experimental and numerical analysis of mechanics and fracture characteristics of engine compressor

Abstract Investigating the fatigue failure behavior of compressor fan blades and their materials in aero-engines is a crucial research area. This paper focuses on the compressor fan blades and their constituent materials of aero-engines. Firstly, fluid-structure interaction (FSI) numerical simulations under various rotational speeds are conducted to determine the stress distribution and identify the maximum stress. Secondly, based on the FSI results, fatigue tests on fan blade materials under different stress amplitudes are performed to explore the relationship between load and life, so as to analyze the fracture characteristics under various stress amplitudes. This research has significant implications for ensuring the stable operation of aero-engine fan blades.

Numerical simulation and experimental analysis of foreign object impact on aero-engine fan rotor blade

The detection and identification of fan rotor foreign object impact events during the working process of aero-engines are crucial to the safety and security of aircraft flight. Through the numerical simulation method based on finite element and the foreign object impact test platform to simulate the process of real engine impact by foreign objects, the rule of fan rotor blade foreign object impact and the monitoring and identification method were studied. Meanwhile, aiming at the problems of high difficulty and low accuracy in identifying the impact of foreign objects on the fan by the airborne parameters and added vibration parameters, the non-contact vibration measurement method based on blade tip timing was used to obtain the blade vibration displacement under different fan speed, foreign matter mass and impact velocity. The numerical simulation and experimental results show that the change trend of the vibration displacement of the rotor tip of the fan is consistent with that of the numerical simulation. And with the increase of the foreign object projectile mass, the vibration displacement of the blade tip caused by the impact of the foreign object on the fan blade increases. In addition, the impact velocity of the foreign object has little effect on the vibration displacement of the blade tips after impact. Furthermore, the vibration displacement of the blade tip caused by the impact of foreign objects first increases and then decreases with increasing speed.

3D Shape Measurement of Aeroengine Blade Based on Fringe Projection Profilometer Improved by Multi-Layer Concentric Ring Calibration.

The precision requirements for aeroengine blade machining are exceedingly stringent. This study aims to improve the accuracy of existing aeroengine blade measurement methods while achieving comprehensive measurement. Therefore, this study proposes a new concentric ring calibration method and designs a multi-layer concentric ring calibration plate. The effectiveness of this calibration method was verified through actual testing of standard ball gauges. Compared with the checkerboard-grid calibration method, the average deviation of the multilayer concentric ring calibration method for measuring the center distance of the standard sphere is 0.02352, which improves the measurement accuracy by 3-4 times. On the basis of multi-layer concentric ring calibration, this study builds a fringe projection profiler based on the three-frequency twelve-step phase shift method. Compared with the CMM, the average deviation of the blade chord length measured by this solution is 0.064, which meets the measurement index requirements of aeroengine fan blades.

Ice accretion characteristics on rotating aeroengine fan blades

An experimental study was conducted to characterize the dynamic ice accretion process on rotating aero-engine fan blades to evaluate the icing-induced detrimental effects on the fan rotor performance. A scaled spinner-fan model was installed in an Icing Research Tunnel and exposed to typical rime and glaze icing conditions. It was found that, while ice structures accreted on both the suction and pressure surfaces of the fan blades, more ice accumulated in the region near the blade roots than those near the blade tips. The ice structures accreted on the fan blades not only deteriorated the shapes of the deliberately designed blades greatly but also blocked the airflow passages through the fan rotor substantially, regardless of the icing type. More specifically, the thickness of the fan blades was found to increase up to 40 % after undergoing 480 s of the rime icing experiment, the airflow passages were blocked by up to 14 % due to the rime ice accretion near the blade roots, resulting in about 70 % reduction of the air pressure increment across the fan rotor. Due to the combined effects of the aerodynamic shear forces and centrifugal forces associated with the rotating motion, substantial water runback was observed over the rotating blade surfaces under the glaze icing condition, resulting in the rapid growth of more complex “needle-like” icicles along the blade leading edges. Glaze ice accretion was found to cause more serious and faster performance degradation to the fan rotor than the rime icing scenario. While the airflow passages between the neighbouring blades were blocked by up to 18 % after undergoing 120 s of the glaze icing experiment, the airflow was found to be depressurized, instead of pressurized, after passing the iced fan rotor.

Retracted: Research on Optimizing Selection and Optimizing Matching Technologies of Aeroengine Fan Rotor Blades

Retracted: Research on Optimizing Selection and Optimizing Matching Technologies of Aeroengine Fan Rotor Blades

Aeroacoustic Effects on the Forcing of Fan and Compressor Blades Due to Distortion

Abstract A distorted air stream entering an aeroengine fan or compressor leads to harmonic forces on the rotating blades. These aerodynamically induced forces are well-known causes of blade vibration and associated fatigue problems. Significant levels of distortion arise from different sources like side wind and high angles of attack that occur at specific operating conditions. For aircraft with the engine closely integrated with the fuselage, the engine will be exposed to distortion during the entire flight cycle. With a focus on understanding the aeroacoustic interaction the computational fluid dynamics (CFD) analyses used here consider harmonics of the distortion. Harmonic responses are calculated from low to transonic speeds for a range of cases. Major phenomena and driving parameters affecting the forcing strength and pressure amplitudes in the blade passage are identified from the analyses. It is demonstrated that the forcing strength is strongly affected by the cut-on/cutoff conditions upstream and downstream of the blades. Also, depending on design parameters of the blade, the aeroacoustics of the blade passage is important for the resulting forcing. All analyses are made in two-dimensional over a wide range of flow conditions as well as geometric variations. The results of the study provide an increased understanding of the harmonic forcing of blades. A simple model is proposed that can identify conditions where increased pressure amplitudes in the blade passage may be expected. The sensitivities to parameters may also give some guidance in how design and operation can be adapted to reduce the aerodynamic forcing.

Mirror-based multimodal straightforward method for impedance eduction using a zigzag array

The Mirror-based Multimodal StraightForward Method (MM-SFM) is proposed herein to realize accurate and reliable liner impedance eduction covering the wide frequency range of aeroengine fan noises. It adopts a novel zigzag array in the flow duct, and unfolds them by a coordinate transformation into a mapping diagonal array in an extended duct, which can increase the array transverse spacing Δz considerably. Then, it invokes the M-SFM incorporating the trust-region and extended Prony's algorithms, to decompose the three-dimensional multimodal aeroacoustic field and educe the impedance. A parametric study based on the Monte-Carlo uncertainty analysis is conducted through finite-element numerical experiments on a 51 × 51 mm2 flow duct, to survey the method performance under random perturbations. It indicates that, the educing accuracy and reliability are promoted by increasing Δz or the axial spacing Δx properly, and the decomposed-mode number M×N=10 is appropriate herein. In our studied cases, using the recommended array of Δz=25.5mm and Δx=22mm locating at the nodes of transverse mode m = 2, the MM-SFM generally produces accurate averaged educed impedances in a considerably extended frequency range from 100 Hz up to nearly 10 kHz, and has small educing uncertainties at most absorptive frequencies and thus a good reliability.

Evaluation Of Foreign Object Damage On The Fan Blades with Microscopic Techniques

Foreign object damage (FOD) is a common problem in gas turbine engines, particularly in the fan and compressor blades. FOD generally occurs when hard body particles are ingested into an aero-engine fan and compressor blade. High-speed impact on fan titanium alloy blades leads to foreign object damage, which weakens the fatigue performance of the blades. It is important to note that FOD can also cause damage that is not visible to the naked eye, such as internal cracks or fatigue damage. Therefore, regular inspections and maintenance are crucial to detect and prevent FOD damage in gas turbine engines. Also using a microscope for the inspection of blades is important. Proper examination of blades damaged by foreign or domestic object can shed light on blade status and prevent further damage in the future. Here are some of the benefits of using a microscope for blade inspection:
 Microscopes can provide high magnification and resolution, allowing for detailed inspection of the blade surface and any defects or damage.
 Microscopes can help detect and identify small cracks, chips, or other forms of damage that may not be visible to the naked eye.
 Microscopes can provide accurate measurements of the blade's dimensions, which can be important for quality control and maintenance purposes.
 Microscopes can help identify the root cause of any damage or wear on the blade, which can inform future design and manufacturing decisions.
 Microscopes can provide visual documentation of the blade's condition, which can be useful for tracking changes over time and for communicating with other stakeholders.
 Overall, using a microscope for blade inspection can help ensure the safety, reliability, and performance of gas turbine engines and other equipment that relies on blades.
 In this study, a comparison was made between visual inspection, borescope control, stereo microscope and SEM-EDX microscope methods used in the detection and removal of foreign material damage. The advantages and disadvantages of these 4 methods are comparatively examined and presented to the attention of the reader.

Triple Decomposition of Unsteady Flow in a Low-Speed Mixed-Flow Fan

Numerous studies (including theoretical modeling, numerical simulation, and experimental measurement) have confirmed that wake interaction is a primary factor affecting tonal and broadband noise emitted by aeroengine fans. The knowledge and techniques derived from these studies have often been applied to analyze and control the aerodynamic noise of low-speed axial/mixed-flow fans used in ventilation and cooling applications. Despite the structural similarity between aeroengine fans and axial-flow fans for ventilation and cooling, the differences in their rotor–stator spacing and operating parameters raise the question of whether or not they share completely identical or approximately similar unsteady flow and noise generation mechanisms. In this paper, we employ a large-eddy simulation to investigate the low-speed unsteady flow inside a mixed-flow fan. The triple decomposition method is used to analyze the spatiotemporal characteristics of the time-averaged, ensemble-averaged, and stochastic fluctuation velocities and pressures in both stationary and rotating coordinate systems. The results show that the unsteady flow and noise generation mechanisms inside the fan investigated in this paper are significantly different from those of aeroengine fans, mainly due to two aspects. First, the wake effect on the velocity field of the fan studied in this paper is almost negligible, and the potential interaction is the primary source of the nonuniform spatial distribution of the time-averaged velocity field and the periodic velocity disturbance. Second, the turbulent energy spectrum of the stochastic fluctuation velocity is greatly distinct from the classic turbulence spectra in the low-frequency bands.

Temperature Resistance Properties of Unidirectional Laminated Cf/SiC-Al Prepared by PIP and Vacuum Pressure Infiltration.

Material used for aero-engine fan blade requires excellent mechanical properties at high temperature (300 °C). Continuous carbon-fiber-reinforced silicon carbide ceramic matrix composites (Cf/SiC) are necessary candidates in this field, possessing low density, high strength, high modulus, and excellent high-temperature resistance. However, during the preparation process of Cf/SiC, there were inevitably residual pores and defects inside, resulting in insufficient compressive strength and reliability. The vacuum pressure melting infiltration process was used to infiltrate low melting point and high wettability aluminum alloys into the porous Cf/SiC composite material prepared by the precursor impregnation cracking process, repairing the residual pore defects inside the body. The porosity of porous Cf/SiC decreased from 49.65% to 5.1% after aluminum alloy repair and strengthening. The mechanical properties of Cf/SiC-Al composite materials strengthened by aluminum alloy repair after heat treatment were studied. The tensile strength of the as-prepared Cf/SiC-Al was 166 ± 10 MPa, which were degraded by 13~22% after heat treatment. The nonlinear sections of stress-displacement curve of as-treated samples were shorter than that of as-prepared sample. The hardness of aluminum alloy matrix after 300 °C 1 h heat treatment was 58 Hv, which was not obviously reduced compared with the sample without heat treatment. The vacuum infiltration of aluminum alloy is expected to have guiding significance for repairing and strengthening internal defects in ceramic matrix composites.

How to Reach 100% Inspection Coverage of Aeroengine Fan Blades with a High Probability of Detection

In aviation, quality is paramount to determine an aircraft’s airworthiness and keep personnel and passengers safe. Non-destructive testing (NDT) methods are largely used throughout an aircraft’s lifetime, including raw material selection, manufacturing, assembly, and in-service maintenance. As a key component of aircraft, engines are governed under strictly scheduled maintenance programs where they are dismantled and thoroughly inspected. Part of this global inspection concerns the individual verification of fan blades to assess the absence of flaws, such as surface cracks. Due to the complex geometry of fan blades, established methods such as penetrant testing (PT) and magnetic particle inspection (MPI) have been successfully used in past decades to detect surface-breaking flaws in fan blades. However, these techniques are complex to deploy and do not permit results traceability. As an alternative, eddy current (EC) technologies proved to be a good candidate to discriminate flaws as small as 1 mm long. Combining both conventional and eddy current array technology provides valuable information on the integrity of the component. Powered with the development of dedicated signal processing methods, the proposed solution helped to increase signal-tonoise ratio, avoiding any false calls. Once this was achieved, a careful study of the probe’s deployment and compliance with the various changes of geometries—from the blade’s surface to its edges and root, helped ensure optimal crack detection. Finally, recent advances in robotics enabled an automated inspection strategy to perform 100% coverage with high reproducibility and repeatability. This greatly improved the probability of detection of sub-millimeter surface-breaking cracks. This paper describes the study performed to assess the capability of eddy current solutions (conventional and advanced) to replace traditional methods of inspecting titanium fan blades. It also shows how dedicated signal processing enables increased probability of detection. The proposed approach to provide full coverage of the complex geometry and the associated developments are detailed. Finally, the paper presents an integration of the complete inspection technique in an automated system.

Allowance Extraction Considering of Inner and Outer Contour and Experimental Research on Belt Grinding of Hollow Blade

Aero-engine fan blades often use a cavity structure to improve the thrust-to-weight ratio of the aircraft. However, the use of the cavity structure brings a series of difficulties to the manufacturing and processing of the blades. Due to the limitation of blade manufacturing technology, it is difficult for the internal cavity structure to achieve the designed contour shape, so the blade has uneven wall thickness and poor consistency, which affects the fatigue performance and airflow dynamic performance of the blade. In order to reduce the influence of uneven wall thickness, this paper proposes a grinding allowance extraction method considering the double dimension constraints (DDC) of the inner and outer contours of the hollow blade. Constrain the two dimensions of the inner and outer contours of the hollow blade. On the premise of satisfying the outer contour constraints, the machining model of the blade is modified according to the distribution of the inwall contour to obtain a more reasonable distribution of the grinding allowance. On the premise of satisfying the contour constraints, according to the distribution of the inwall contour, the machining model of the blade is modified to obtain a more reasonable distribution of the grinding allowance. Through the grinding experiment of the hollow blade, the surface roughness is below Ra0.4 μm, and the contour accuracy is between − 0.05~0.14 mm, which meets the processing requirements. Compared with the allowance extraction method that only considers the contour, the problem of poor wall thickness consistency can be effectively improved. It can be used to extract the allowance of aero-engine blades with hollow features, which lays a foundation for the study of hollow blade grinding methods with high service performance.

An investigation of aerodynamic performance of aeroengine fan and booster under non-uniform inlet conditions

An investigation of aerodynamic performance of aeroengine fan and booster under non-uniform inlet conditions

Experimental investigations into delamination behavior of curved composite laminates reinforced by a pre-hole z-pinning (PHZ) method

In this paper, an experimental study is conducted on the resistance of delamination in curved carbon fiber/epoxy composite laminates reinforced by z-pins. The curvature of the specimens is designed according to that of the aero-engine fan blade roots. A cost-effective pre-hole z-pinning (PHZ) technique is employed to mitigate initial in-plane damage, and the impact of z-pin volume fraction and diameter on interlaminar fracture toughness and bridging behavior is determined through double cantilever beam (DCB) testing. The mode-mixity of z-pin is determined, and the fracture toughness of curved specimens is calculated based on Timoshenko curved beam theory. The results indicate that the mode-mixity varies depending on the location of z-pins. Z-pins are subjected to a mix of crack opening and crack sliding loads during the tests. The primary failure mode of z-pins is pull-out, with a minor portion of the pins experiencing fracture. Specimens with 0.8 vol% z-pins exhibit a fracture toughness that is approximately 567% higher than that of unpinned specimens. The delamination resistance capacity of z-pins is dependent on the mixed-mode ratio, due to the transition in delamination resistance mechanism and failure behavior of the z-pins.

A Review on Leading-Edge Erosion Morphology and Performance Degradation of Aero-Engine Fan and Compressor Blades

The leading edges of aero-engine fan and compressor blades suffer from severe erosion due to the inhalation of suspended particulates in the low-altitude atmosphere during long-term transport. A small deformation of the leading edge can significantly change the aerodynamic performance under a strong non-linear effect, leading to increased operation and maintenance costs for engines. This review first focuses on leading-edge erosion morphology during service, and models of these damages. Secondly, the performance degradation caused by eroded leading edges on different classes of engine components, including airfoils, blades, compression systems, and the whole engine, are reviewed. Finally, optimization methods for eroded blade leading edges and their effects on performance recovery are summarized. This paper contributes to an in-depth understanding of the erosion mechanism of blade leading edges in terms of status and its effect, and is a good reference for establishing erosion leading edge repair methods and improving the level of automated repair.

Impedance eduction experiments covering higher frequencies based on the multimodal straightforward method

The multimodal straightforward method is developed further, validated and applied experimentally. The trust-region algorithm is introduced to reduce the eduction time, a flow duct setup with a cross section of 51 × 51 mm2 is built for the impedance eduction, and several single- and multi-layer perforated liners are tested from 0.5 kHz up to 6.0 kHz at two average Mach numbers under several types of modal sound sources. It is validated that, this method, by utilizing a diagonal microphone array and improving Prony’s algorithm, enables the automatic match between axial and transverse wavenumbers, and thus realizes the full decomposition to three-dimension multimodal sound fields. By introducing the trust-region algorithm, it can educe the impedance with a good consistency and a higher time efficiency. Generally, this method is applicable to the practical impedance eduction in multimodal aeroacoustic environments on a real flow duct, with the upper frequency extended from 3.0 to 6.0 kHz covering the main frequency range of aeroengine fan noises. For multilayer liners, the educed impedance spectrum is considerably flatter than the prediction by an existing impedance model in some cases especially near the antiresonance, and the grazing flow magnifies such a flatting trend accompanied by more evident predicting deviations. The spectra of educed impedance and transmission loss show that the multilayer liner possesses more resonant frequencies within the concerned range and broadband absorption potentials if well designed.

Effect of Heat Treatment on Fracture Behavior of AISI 630 Alloy Manufactured by Directed Energy Deposition

AISI 630 alloy is widely used in the manufacture of CFM56 series aeroengine fan casing because of its high strength and excellent ductility. Herein, AISI 630 alloy is directly manufactured by directed energy deposition. The microstructural evolution, mechanical properties, and fracture behavior of AISI 630 alloy in as‐deposition, solution, and aging conditions are analyzed. Scanning electron microscopy, X‐ray diffraction, and electron backscattering diffraction are used to characterize the microstructure and phase characteristics. Mechanical tensile and Vickers hardness tests are performed. The results show that the samples as‐deposited, solution, and solution and aging samples are all composed of α phase and small amount γ phase, where γ phase proportions are 10.6%, 0.2%, and 10.8%, respectively. Due to transformation‐induced plasticity effect, the as‐deposited specimens have the highest strain hardening coefficient (0.410–0.432), which results in the tensile strength of 1121–1143 MPa, the yield strength of 279–293 MPa, and the fracture elongation of 14.9%. After solution and aging treatment, the tensile strength is increased by about 8% (1206–1239 MPa), the elongation at break is decreased by about 30% (9.6–11.4%), and the yield strength is increased by more than one time (740–907 MPa).

Machine learning augmented multi-sensor data fusion to detect aero engine fan rotor blade flutter

Abstract Flutter-induced fatigue failure investigation of the fan blades of aero-engines necessitates extensive testing. During engine ground testing, strain gauges on rotor fan blades and casing vibration sensors were employed to investigate structural dynamic aspects. The correlation between strain sensor signals and fan casing vibration signals allowed the diagnosis of fluttering fan blades. For automated flutter detection during engine development testing, a machine learning-augmented information fusion methodology was developed. The method analyses casing vibration signals by extracting time-domain statistical features, intrinsic mode function characteristics through empirical mode decomposition, and recurrence quantification features. Feature vectors obtained from a relatively large set of engine tests were subjected to dimension reduction by applying machine learning techniques to rank them. Reduced feature vector space was labelled as “flutter” or “normal” based on the correlation of rotor strain gauge signals. In addition, the labelled feature vectors were employed to train classifier models using supervised learning-based algorithms such as Support Vector Machines, Linear Discriminant Analysis, K-means Clustering, and Artificial Neural Networks. Using only vibration signals from the casing, the trained and validated classifiers were able to detect flutter in fan baldes with a 99% probability during subsequent testing.

The Methodological and Experimental Research on the Identification and Localization of Turbomachinery Rotating Sound Source

The localization and quantification of turbomachinery rotating sound sources is an important challenge in the field of aeroacoustics. In order to compensate the motion of a rotating sound source, a rotating beamforming technique is developed and applied in a flow duct, which uses a wall-mounted microphone array placed circularly parallel to the fan, to detect the broadband noise source of the aeroengine fan. A simulation of three discrete rotating sound sources with a non-constant rotational speed is pursued to verify the effectiveness in reconstruction of the correct source positions and quantitative prediction of the source amplitudes. The technique is ulteriorly experimentally implemented at an axial low-speed fan test rig facility. The fan test rig has 19 rotor blades and 18 stator vanes, with a design speed up to 3000 rpm. The method can accurately identify the radial and circumferential positions of the three rotating sound sources in the simulation case, large side-lobes appear near the main-lobe of the sound source due to the geometric influence of the microphone array. A noticeable feature of beamforming images for axial flow fan is that the sound sources appear to be concentrated in the tip region rather than distributed along the span.