The C-axis-oriented AlN thin films were fabricated on Ni-based alloy substrates using medium-frequency reactive magnetron sputtering.Hydrogen was introduced during the sputtering process to induce lattice defects,followed by high-temperature annealing to repair these defects.The crystal structures of the films were characterized by X-ray diffraction and transmission electron microscopy.The results indicate that the(0002)diffraction angle of hydrogen-doped AlN films increased linearly with rising annealing temperatures between 400 and 800℃.Annealing at 800℃for 15 min significantly reduced the number of edge-type and screw-type dislocations in the grain regions,with a lattice spacing contraction rate of 6.64%.However,at temperatures above 800℃,thermal stress from the Ni-based alloy substrate caused lattice expansion,which impaired the defect-repairing effect.The(0002)diffraction angle decreased as the annealing temperature increased beyond 800℃.These findings demonstrate that hydrogen-doped AlN films on Ni-based alloy substrates are suitable for temperature sensing in the range of 400～800℃.
To optimize the starting procedures for a civil turbofan engine,an analysis of influencing factors during the subsequent two phases(accelerating from ignition success to idle,and maintaining steady state at idle)of the starting process was conducted.Research was conducted on adjusting starter air supply pressure,matching start fuel scheduling with variable geometry components,and exploring the stable operating boundary at idle.The results indicate that increasing the start fuel flow by 10%reduces the engine starting time by 6.30 s.Increasing the variable stator vane opening by 1.5° results in a 5.10%increase in compressor pressure ratio,a 4.99%rise in airflow,and a 9.25%improvement in rotor acceleration rate,and the starting time shorten by approximately 6.00 s.Additionally,coordinating the transient bleed valve at the compressor outlet to bleed air can effectively reduce the operating line of the high-pressure compressor,increase compressor surge margin,and resolve longstanding issues such as prolonged starting time,high risk of overheating and surge,and instability at idle.This research provides essential support for the airworthiness certification of turbofan engine starting capabilities.
For abnormal leakage of liquid film seals in the aviation field caused by whirling conditions,considering factors such as seal dynamics,whirling characteristics,and radial relative motion of the faces,the influence of whirling conditions on the evolution of seal leakage and leakage characteristic values was analyzed by solving the dynamics equations and the Reynolds equation with the radial velocity effect.The results indicate that under synchronous whirling motions,an elliptical whirling motion only causes minor changes in the fluid film thickness and load-bearing capacity,but it leads to shear flow leakage at the sealing faces.As the long axis to short axis ratio of the whirling trajectory increases from 1,the shear flow leakage starts to increase significantly from 0 and then tends to a certain value.The radial shear flow effect under elliptical whirling conditions is a potential cause of abnormal leakage in liquid film seals.
For the suppression of rotor-stator interaction tonal noise,a combined configuration of porous material and wavy leading edge was proposed.A hybrid acoustic/flow field method was employed for tonal noise prediction.The aerodynamic performance and tonal noise of the baseline fan,the wavy leading edge fan and the local porous wavy leading edge fan were compared.The results show that the local porous wavy leading edge has a greater impact on the fan aerodynamic performance than that of the wavy leading edge.The local porous wavy leading edge resulted in a decrease of 0.007 0 in the total pressure ratio and a reduction of 3.67%in efficiency.Compared to the wavy leading edge,the local porous wavy leading edge demonstrates a significant improvement in noise reduction performance.Specifically,it reduces the tonal noise by 8.6 dB at the first blade passing frequency.The local porous wavy leading edge effectively suppresses the strong pressure fluctuations at the wavy trough,while maintaining the alteration in the phase of pressure fluctuations,thus further reducing the tonal noise.
To meet the performance and structural requirements of modern aero-engine combustors,including low pollutant emissions,low total pressure loss,and structural compactness,the effects of key design and operating parameters on the performance of a multi-channel diffuser were analyzed using CFD.The effects of area ratio,relative expansion gap,and inlet Mach number on the total pressure loss were examined,and the results were compared with relevant data in the literature.It is shown that the area ratio and the relative sudden expansion gap significantly affect the aerodynamic performance of diffuser.When the relative sudden expansion gap is 1.5,as the area ratio increases from 1.4 to 1.8,significant vortex-like changes occur at the outlet section of the diffuser,resulting in an increase in flow loss,with the total pressure loss change rate being approximately 30%.As the Mach number increases,the total pressure loss keeps rising,from 1.20%under the condition of 0.15 Mach number to 13.85%under the condition of 0.50 Mach number,and the total pressure loss increases linearly with the square of the inlet Mach number.
Local blade damage such as corner loss and edge curling may occur in compressor rotors of aero-engines during service,which can significantly affect the acoustic characteristics of the ducted flow.An experimental investigation was conducted on the acoustic characteristics of a compressor with local blade damage based on duct circumferential mode analysis.A 3.5-stage axial compressor was taken as the research object.A circumferentially arranged ring microphone array was employed to measure the in-duct flow-induced acoustic signals under different rotational speed conditions,and the measured data were decomposed into circumferential acoustic modes.Combined with duct acoustic propagation theory,the influence mechanism of local blade damage on the order,amplitude,and energy distribution of acoustic modes was analyzed from the perspective of circumferential non-uniform disturbances.The results show that local blade damage introduces a finite-scale non-uniform disturbance in the circumferential direction of the rotor,which tends to excite low-order circumferential acoustic modes,leading to a significant enhancement of low-order mode energy that is relatively weak under normal conditions.In the circumferential mode spectra,this feature appears as oblique ridge-like structures associated with the rotational frequency.These results reveal the variation characteristics of circumferential acoustic mode structures under local blade damage conditions and provide experimental evidence for the understanding and analysis of the acoustic characteristics of local blade damage.
Using CFD simulation methods,the effects of rotor front sealing cooling air and casing cooling air on the tip clearance flow field of a typical turbine engine were investigated.The results show that by mixing into the low-temperature boundary layer of the outer ring wall,the rotor front sealing cooling air hinders the intrusion of high-temperature gas from the pressure side into the tip clearance,to decrease the surface heat load by approximately 20%along the chordwise direction of the blade tip.The injection of casing cooling air into the low-temperature boundary layer of the outer ring wall causes local boundary layer separation,leading to the mixing of high-temperature mainstream gas into the boundary layer.At specific positions,the casing jet also suppresses the relatively low-temperature gas into the tip clearance,ultimately resulting in the intrusion of high-temperature gas into the tip clearance and increasing the surface heat load of the blade tip.When both cooling airs are applied simultaneously,their effects within the tip clearance interfere with each other,leading to the intrusion of high-temperature gas into part of the tip clearance and increasing the local surface heat load at the blade tip.The addition of cooling air increases the total pressure loss at the outlet,with the relative loss caused by casing cooling air being the highest at 7.03%.The impact of the outer ring cooling air on the flow within the tip clearance is significant,and the influence of the outer ring cooling air should not be neglected when designing the cooling system for turbine rotors.
DD32 superalloy is widely used in the fabrication of complex single-crystal turbine blades.The sophisticated heat treatment encountered during blade preparation can lead to variations in the microstructure and mechanical properties of the alloy.The standard heat treatment and the full heat treatment which the blade receives have been applied to DD32 alloy,and their microstructure,900℃tensile property,and 1 000℃/280 MPa stress rupture property were also investigated.Optical microscopy and electron microscopy were utilized to characterize the microstructures and the fracture morphologies of the alloy under the two distinct conditions.The results show that there is a more pronounced difference in the microstructure in the dendrite core than that in the interdendritic regions.Compared with the standard heat-treated alloy,the fully heat-treated alloy exhibits a slight reduction in tensile strength at 900℃,whereas its elongation and reduction of area show no obvious variations.Meanwhile,the stress-rupture life at 1 000℃/280 MPa of the fully heat-treated alloy is moderately decreased,accompanied by an increase in elongation and reduction of area.The findings obtained in the present work offer significant references for the design and preparation of complex turbine blades.
Fan noise control in aero-engines represents a key challenge for green aviation,and acoustic mode identification method is critical for analyzing its propagation mechanism.Three types of mainstream acoustic mode identification methods are scrutinized,and their development history over the past 60 years is reviewed.Analytical models,based on Bessel function orthogonal decomposition,are characterized by strong physical interpretability and low-frequency stability,supporting real-time applications like health monitoring;yet they are limited by high-frequency sensor demands and ideal flow field assumptions.Sampling bottlenecks are overcome by compressed sensing via modal sparsity,with sensor usage reduced by 46.9%to 75.0%and noise robustness enhanced;however,it is reliant on sparsity assumptions and lacks adaptability to complex flow fields.Complex scenarios(e.g.,non-uniform flows)are addressed by machine learning through data-driven and physical constraint integration,achieving 87.2%cross-geometry transfer accuracy;yet it has high data dependency and low interpretability.The feasibility of these methods has been verified on international and domestic test rigs,supporting applications like acoustic liner optimization and blade design.Current main challenges include high-frequency errors,poor complex flow adaptability,and limited data generalization.Future breakthroughs are expected via multi-physics coupling modeling,machine learning interpretability enhancement,and algorithm-hardware co-design.
To address the issue of inadequate performance in traditional PID control caused by the nonlinearity and time-varying characteristics of the electro-hydraulic servo valve in the mechanical-hydraulic fuel system of gas turbines,a control strategy based on adaptive fuzzy PID was proposed.Through establishing a high-precision simulation model of the fuel system,its reliability was verified with experimental data,and an adaptive fuzzy PID controller for online parameter optimization was designed.The simulation results indicate that for valve displacement,flow metering and angle of the vane,the error between the model and test data is less than 3.5%,confirming the model's accuracy.Compared to traditional PID control,the adaptive fuzzy PID control reduces overshoot by 16.4%in step response,shortens the setting time by 20.5%,and maintains robust performance even under fault conditions of the electro-hydraulic servo valve.This strategy provides a theoretical foundation and engineering reference for the intelligent control of gas turbine fuel systems.
With the development of civil low-pollution combustion technology and military high-temperature combustion technology,the problem of combustion instability is becoming more and more prominent.The perforated sound lining structure is designed in the main combustion chamber flame cylinder,afterburner anti-vibration screen,center cone,and other structures,which has important application prospects for absorbing the sound waves generated by unstable combustion.In order to improve the absorption bandwidth of the perforated acoustic lining with traditional single configuration,a multi-order resonant sound-absorbing metamaterial was proposed to extend the effective bandwidth of sound absorbing structures,and a composite structure model was established combining the traditional micro-perforated sound-absorbing structure with the micro-perforated sound-absorbing structure with curved channels.Its sound absorption performance was studied by finite element method.The results demonstrate that,compared to conventional single-layer micro-perforated absorbers,this model significantly improves sound absorption performance across the 300～700 Hz frequency range.
Based on the axial flow compressor test bench,performance tests on a two-stage compressor with adjustable inlet guide vanes were conducted under different inlet guide vane angles and different rotational speeds,and the stable working range and stall boundary of the compressor were obtained.Considering that the traditional empirical mode decomposition(EMD)method is prone to frequency aliasing of modal components,the variational mode decomposition(VMD)method has been s adopted to conduct feature recognition and extraction of the compressor stall signal.In response to the phenomenon that VMD overly relies on the number of modes K and the penalty factor α in the extraction of compressor stall characteristics,an improved algorithm based on bionics optimization was adopted.By introducing the leapfrog algorithm to construct an adaptive parameter optimization mechanism,the dynamic optimization of K and α was achieved with the average envelope entropy as the optimization objective,and the advantages of the simulation signal verification parameter optimization VMD method were constructed.Finally,the improved algorithm was applied to the signal analysis of the compressor stall working condition.The results show that compared with the EMD method,the parameter-optimized VMD method can separate the dominant modal components representing the stall characteristics more accurately.
To address the issues of low image quality of birds,difficulty in accurately testing the velocity and trajectory of birds flocks,and low accuracy of test results in traditional birds ingestion experiments,a method for measuring key parameters of aero-engine birds ingestion tests based on deep learning was proposed.Firstly,an image segmentation network based on U-Net was built to automatically segment the contour of the birds,achieving precise positioning of the edge area of the birds to be detected.Then,a key frame merging algorithm was developed,which used similar pixels in the images before and after the segmented flying object area to realize automatic annotation of feature points of the birds in continuous frame images.Finally,based on Kalman filtering and cubic spline interpolation methods,an automatic fitting model for the movement trajectory of the birds was developed to achieve high-precision measurement of the flight trajectory and velocity.The experimental results show that,compared with manual precise calibration,the centroid coordinates obtained by the designed centroid discrimination algorithm have an average error of less than 1.00%;compared with manual measurement,the velocity obtained by the velocity measurement algorithm has an error of less than 2.00%.
Because of excellent corrosion resistance,high temperature resistance,and low thermal conductivity,ceramic coating can play a protective role on the surface of hot end parts of aero-engines.The most representative ones are thermal barrier coatings(TBCs)and environmental barrier coatings(EBCs).The TBCs are used for thermal insulation protection of high-temperature alloy hot-end components(mainly turbine blades),while EBCs are used for protection against ceramic matrix composites.The differences between traditional thermal barrier ceramic coatings and high entropy and nano-sized thermal barrier ceramic coatings were compared in the aspects of the mechanical,thermophysical,and corrosion resistance properties,and two rare earth silicates in EBC and their common failure modes were reviewed;the future development direction of high entropy and nano-ceramic coatings in aero-engines was prospected.
Analysis and experimental verification of a disk strength test failure for an aero-engine were carried out.Starting from the fault phenomenon,fracture analysis of the test piece and main fixtures was carried out.The basic events that may cause the failure were analyzed and investigated one by one,and the causes of the fault were explored after investigation.Based on this,measures were improved and experimentally verified.The results showed that after taking improvement measures,the disk successfully completed the strength test and experienced stable vibration throughout the entire test process,verifying the effectiveness of the improvement measures.The research improves the design of experimental fixtures and provides reliable experimental data for the development of an aero-engine.
