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The rotary blade-disk-shaft (RBDS) coupling system is the core part of the aero-engine and gas turbine, and blade crack is one of the most common faults for the RBDS system. First, to analyze the fault mechanism of blade crack and to investigate the effects of blade crack on the three-dimensional blade tip clearance (3D-BTC) of RBDS system, a novel dynamic model of the RBDS system with the blade crack is developed based on the continuum theory. In this model, the blade radial deformation, flap-wise bending, and chordwise bending are comprehensively considered. Then, combining the blade breathing crack model based on the three-dimensional stress state of the blade, the dynamic model of the RBDS system with blade crack is developed so that the 3D-BTC of blade crack can be obtained. The dynamic model is validated by comparing it with the finite element model and experiments. Besides, based on the analysis of the 3D-BTC dynamic response of RBDS system, the 3D-BTC difference vectors of RBDS system are proposed and the effects of blade crack on the 3D-BTC difference vector are investigated. The simulation results show that the largest element of the 3D-BTC difference vectors indicates which blade is cracked. The largest element of the 3D-BTC difference vector increases with the blade crack depth, and it changes non-monotonically as the blade crack location moves from the blade root toward the blade tip. At last, the 3D-BTC of RBDS system with blade crack is obtained based on the optical-fiber-based measurement system, and the 3D-BTC difference vectors are constructed. The experimental results show that the variation trends of the largest elements of the 3D-BTC difference vectors are consistent with the simulation results, which indicates that the 3D-BTC difference vectors can be applied in the blade crack fault diagnosis of the RBDS system.

An improved rotor-blade dynamic model is developed based on our previous works (Ma et al. in J Sound Vib, 337:301–320, 2015 ; J Sound Vib 357:168–194, 2015 ). In the proposed model, the shaft is discretized using a finite element method and the effects of the swing of the rigid disk and stagger angles of the blades are considered. Furthermore, the mode shapes of rotor-blade systems can be obtained based on the proposed model. The proposed model is more accurate than our previous model, and it is also verified by comparing the natural frequencies obtained from the proposed model with those from the finite element model and published literature. By simplifying the casing as a two degrees of freedom model, the single- and four-blade rubbings are studied using numerical simulation and experiment. Results show that for both the single- and four-blade rubbings, amplitude amplification phenomena can be observed when the multiple frequencies of the rotational frequency ( f r ) coincide with the conical and torsional natural frequencies of the rotor-blade system, natural frequencies of the casing and the bending natural frequencies of the blades. In addition, for the four-blade rubbing, the blade passing frequency (BPF, 4 f r ) and its multiple frequency components also have larger amplitudes, especially, when they coincide with the natural frequencies of the rotor-blade system or casing; the four-blade rubbing levels are related to the rotor whirl, and the most severe rubbing happens on the blade located at the right end of the whirl orbit.

Real time and accurate tip clearance measurement and monitoring is one of the effective ways to improve the aero engine’s efficiency and ensure its safety. This paper presents a microwave sensor with a nearly microstrip patch antenna structure for blade tip clearance measurement in engine. To ensure the stability of the sensor under the harsh and high-temperature environment in the engine, some special considerations have been made on its structure and material. The sensor was optimized and calculated by simulation, then manufactured ang measured. The experiment results show excellent measurement resolution, and verifies the sensor is suitable for blade tip measurement in engine.

Purpose This paper aims to offer a simultaneous design approach for helicopter having swept anhedral blade tip shape and helicopter flight control system (HFCS) to minimize controller cost. Design/methodology/approach By considering previously stated offer, control-oriented models and a stochastic optimization method are applied to minimize controller cost of the HFCS. Findings Using simultaneous design approach for helicopters having blade tip swept and blade tip anhedral causes considerably less control effort than the helicopters not benefiting this related design approach. Practical implications Simultaneous design approach for helicopters having blade tip swept and blade tip anhedral is applicable to consider fuel economy. Originality/value One important novelty of this paper is using simultaneous approach for determining optimum shape of blade tip swept and anhedral. Another considerable novelty of this paper is also using a stochastic optimization method called simultaneous perturbation stochastic approximation for previously mentioned purpose. In this paper, it is also reached that using simultaneous design approach for swept anhedral helicopter blade tip shape and HFCS causes less control effort than the helicopters not using this approach. This leads to less fuel consumption and green environment.

In order to improve the flow characteristics of the rotor tip vortex, a jet flow is generated by the tip plasma exiter, which interferes with the formation and evolution and development of the blade tip vortex. To achieve the purpose of improving blade vortex interference noise. In this paper, a numerical method is used to establish a rotor blade tip jet flow calculation method. The characteristics of the tip vortex wake are analyzed in the hovering state which after the jet flow is loaded, and a law of the development and evolution of the tip vortex with different jet flow parameters is given. The result show that the tip vortex vorticity of the loaded tip jet flow is weakened, and the induced vortex generated by the jet flow cracks the baseline wake vortex, reducing The strength of the weak rotor tip vortex is reduced, with the increase of the jet flow hoel diamenter, the tip vortex weakens; the jet flow velocity is deflected downward, and the vertical component of the jet flow will offset the rotational velocity formed by the tip vortex, weakening the tip vortex vorticity, with the increase of jet flow declination angle, the weakening degree of tip vortex vorticity is stronger, with the increse of jet flow velocity, the tip vortex is weakened, the jet flow velocity reaches 100m/s, and the wake angle ψ=45° vorticity peak weakened by 31%, wake angle ψ=90° vorticity peak weakened by 22%.

Digital twin that shows great potential in different fields may serve as the enabling technology for the health monitoring of aero-engine blade. However, due to the harsh conditions inside the aero-engine, one of the most challenging issues for the implementation of digital-twin-based blade health monitoring is the lack of an accurate connection method between the digital-twin model and the physical entity for rotating blade. Wherein, the key is how to measure the blade data accurately. The emerging blade tip timing (BTT), an effective non-contact measurement method for blades, has received extensive attention recently. Whereas, due to the limited probes that are allowed to be installed on the engine casing, the BTT signal is generally incomplete and under-sampling, which makes it very difficult to reconstruct the blade vibration parameters from the measured data. In this study, a novel paradigm for blade vibration parameter reconstruction with super-resolution from the undersampled BTT signal is proposed based on atomic norm soft thresholding (AST), which may offer accurate blade vibration information for the construction and updating of blade digital-twin model. Unlike the conventional reconstruction method that generally needs the interested signal to be sparse under a finite discrete dictionary for successful reconstruction, the proposed AST-based blade vibration parameter reconstruction method can take any continuous value in the frequency domain from the measurement data with fewer sampling numbers and higher under-sampling rate. Both numerical simulation and experimental verification are utilized to verify the validity of the proposed method. The comparative results indicate that the proposed method performs well in resisting “incomplete.” Meanwhile, the proposed method performs better than state-of-the-art methods under conditions with fewer data.

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.

Blade Tip Timing (BTT) is an essential non-contact technique for monitoring vibrations in rotating machinery, but its practical accuracy is often degraded by noise, undersampling, and spectral leakage. This paper proposes a multi-stage robust Bayesian high-resolution identification framework that systematically addresses these challenges. A recursive digital algorithm based on Kalman filtering estimates the rotational speed without requiring once-per-revolution probes, effectively suppressing sensor noise. An attention-enhanced dynamic convolutional autoencoder then generates channel-specific window functions to minimize spectral leakage. The core identification algorithm extracts phases via all-phase FFT and employs sub-bin interpolation to overcome the resolution limitation of conventional FFT. A Tukey-biweight-based robust aggregation strategy is used to suppress the influence of abnormal or unequal-quality sensor channels during multi-channel phase fusion. A Bayesian prior distribution over the vibration order guides the estimation toward physically plausible values under noisy conditions. Finally, a coarse-to-fine multi-stage search strategy drastically reduces computational burden while preserving accuracy. Experiments on a rotor-blade test bench at constant and variable speeds show that the method reduces the noise floor by about 60 dB, achieves a maximum frequency identification error of 7.84%, and accelerates the search by approximately 48.6% compared to exhaustive search. The proposed method provides a reliable and efficient solution for blade health monitoring.

Due to its non-intrusive manner, blade tip timing (BTT) is considered a potential tool for the condition monitoring of turbomachinery. The challenge of BTT relates to significant under-sampled signal processing, which is induced by a lower number of probes. Signal processing assumes that the ability of the hardware system can meet the requirements of the software algorithm. The abilities of the hardware, including the time resolution of the data acquisition system (DAS) and the dynamic characteristics of rigs, are compromised, particularly when the rotating speed increases. This increase in speed causes two problems for BTT: (1) the rig is less stable, due to the reduction of dynamic stiffness; (2) the time resolution of the DAS can be inadequate for identification. To promote the performance of the hardware system, here a BTT rig was designed with high dynamic performance, including a new DAS with a time resolution of 10 ns. A variety of commonly used BTT signal processing methods are used to analyze the experimental data and verify the good reliability and validity of the experimental platform.

Health monitoring is crucial for the safe operation of rotating machinery. As an effective technique for measuring the vibration of rotating blades, blade tip timing (BTT) is widely used since its advantages of non-contact and low intervention. During the operation of high-speed blades, the multi-mode coupled synchronous vibration will occur. However, the existing BTT-based methods cannot identify the multi-mode coupled vibration parameters. To solve the problem, a multi-mode coupled vibration model of the blade based on a slender cantilever beam is established, and the contribution of each mode to the blade vibration response is considered. A new Circumferential Fourier Fit (CFF) method for parameters identification of blade multi-mode coupled synchronous vibration is proposed. According to the proposed method, the reconstruction of multi-mode coupled synchronous vibration signals can be realized. Finally, the accuracy of the proposed method is verified by simulation data.