Preliminary Design Guidelines for Considering the Vibration and Noise of Low-Speed Axial Fans Due to Profile Vortex Shedding

This paper presents a critical overview on worst-case design scenarios for which low-speed axial flow fans may exhibit an increased risk of blade resonance due to profile vortex shedding. To set up a design example, a circular-arc-cambered plate of 8% relative curvature is investigated in twofold approaches of blade mechanics and aerodynamics. For these purposes, the frequency of the first bending mode of a plate of arbitrary circular camber is expressed by modeling the fan blade as a cantilever beam. Furthermore, an iterative blade design method is developed for checking the risky scenarios for which spanwise and spatially coherent shed vortices, stimulating pronounced vibration and noise, may occur. Coupling these two approaches, cases for vortex-induced blade resonance are set up. Opposing this basis, design guidelines are elaborated upon for avoiding such resonance. Based on the approach presented herein, guidelines are also developed for moderating the annoyance due to the vortex shedding noise.

Comprehensive assessment of the strength of the composite fan blade of the main ventilation of the mine

The work is devoted to the development and calculation of the strength of a new composite fan blade of the main ventilation of the mine, including the static and modal analyzes, as well as the stability analysis. The studies took into account the pre-determined aerodynamic loads on the lateral surface of the blade airfoil. The research was carried out by means of the finite element analysis of the thin-walled airfoil structure using the theory of thick multilayer shells. Estimation of the static strength was performed using the Hashin strength criterion. Analysis of the airfoil shell buckling resistance under the action of bending aerodynamic loads was performed using the methods of the linear stability theory. The modal analysis was performed taking into account the prestressed state from the action of static loads. The analysis of the research results testifies to the sufficient static and dynamic strength of the composite airfoil and the possibility of its implementation in a real rotary machine with the correct design of the fastening between the metal part of the blade root and the composite airfoil. The method of designing and analyzing the strength of the fan blade composite airfoil can be used to create new composite elements of turbomachines: the correct selection of thicknesses of different parts of the airfoil allows obtaining a uniform design with rational use of material; the optimal location of the stiffeners inside the airfoil shell avoids its excessive displacement and stress and the buckling effects, as well as achieving the maximal detuning level from the bending natural frequencies of vibrations; the proposed integrated approach to the strength assessment, which takes into account the effect of aerodynamic loads on the blade airfoil in the static analysis and the prestressed state during the modal analysis can significantly improve the accuracy and correctness of calculations. The approach described in the paper is new for low-speed rotary machines, as at present there are no comprehensive methods for designing composite blades of fans and compressors, and there is no mention of specific examples of their implementation in the projects implemented by manufacturers.

Design of a soft sensing technique for measuring pitch and yaw angular positions for a Twin Rotor MIMO System

Background: This paper presents a soft sensor design technique for the estimation of pitch and yaw angular positions of a Twin Rotor MIMO System (TRMS). The objective of the proposed work was to calculate the value of pitch and yaw angular positions using a stochastic estimation technique. Methods: Measurements from optical sensors were used to measure fan blade rotations per minute (RPM). The Kalman filter, which is a stochastic estimator, was used in the proposed system and its results were compared with those of the Luenberger observer and neural network. The Twin Rotor MIMO System is a nonlinear system with significant cross-coupling between its rotors. Results: The estimators were designed for the decoupled system and were applied in real life to the coupled TRMS. The convergence of estimation to the actual values was checked on a practical setup. The Kalman filter estimators were evaluated for various inputs and disturbances, and the results were corroborated in real-time. Conclusion: From the proposed work it was seen that the Kalman filter had at least Integral Absolute Error (IAE), Integral Square Error (ISE), Integral Time Absolute Error (ITAE) as compared to the neural network and the Luenberger based observer.

New Ultrasensitive Sandwich-Type Immunoassay of Dendritic Tri-Fan Blade-like PdAuCu Nanoparticles/Amine-Functionalized Graphene Oxide for Label-Free Detection of Carcinoembryonic Antigen

The early detection of tumor markers has an effective role in the treatment of cancer. Here, a new sandwich-type electrochemical immunosensor for early label-free detection of the cancer biomarker carcinoembryonic antigen (CEA) was developed. Dendritic tri-fan blade-like PdAuCu nanoparticles (PdAuCu NPs)/amine functionalized graphene oxide (NH2-GO) were the label of secondary antibodies (Ab2), and Au nanoparticle-decorated polydopamines (Au/PDA) were immobilized on a screen-printed carbon electrode (SPCE) as the substrate materials. Dendritic tri-fan blade-like PdAuCu NPs/NH2-GO was synthesized according to a simple hydrothermal procedure and used to immobilize antibodies (Ab2) with large surfaces areas, increased catalytic properties and good adsorption to amplify the current signals. Subsequently, Ab2/PdAuCu NPs/NH2-GO catalyzed the reduction of H2O2 in the sandwich-type immunoreactions. Under optimal conditions, the immunosensor exhibited a satisfactory response to CEA with a limit detection of 0.07 pg mL−1 and a linear detection range from 0.1 pg mL−1 to 200 ng mL−1. The proposed immunosensor could be suitable enough for a real sample analysis of CEA, and has clinical value in the early diagnosis of cancer.

Unsteady Flow Characteristics of an Oscillating Piezoelectric Fan Blade at High Reynolds Numbers

Piezoelectric fans have started to play an essential role in small-scale heat removal applications in recent years due to their high reliability and efficiency. In this study, an experimental study on the flow field characteristics produced by an oscillating piezoelectric fan at various Reynolds numbers (140 < Re < 550) in a quiescent air environment is investigated. Time resolved particle image velocimetry (PIV) measurements are performed for the flow field visualization. The flow pattern generated by the oscillating fan blade in the longitudinal plane changes as the Reynolds number increases. The ratio between the trailing edge velocity and side edge velocity increases as the Reynolds number increases. As a result, the trailing edge plays a more important role in driving fluid at a higher Reynolds number. Multiple vortexes are shed from the trailing edge during one oscillation cycle and is observed only at a high Reynolds number. This vortex shedding increases the unsteadiness of velocity field significantly, resulting in a turbulence intensity level beyond 100%. This result implies that turbulence models used in numerical studies need to be carefully validated as some might struggle at this highly turbulent flow regime.

Transient Response of a Simulated Aeroengine with a Fusing Structure during a Fan-Blade Out Event

A fan-blade out (FBO) event may cause complex vibrations in an aeroengine. A fusing structure protects the structural integrity of the whole aeroengine after an extreme accident, such as a blade-loss event. In this paper, we investigate not only the transient and steady responses of a simulated aeroengine model with a fusing structure after an FBO event but also the changes made to the model because of the fusing structure. Our simulated model of an aeroengine includes two rotors, bearings, and a casing. The results for the dynamic response of the simulated model show that the fusing structure can reduce the steady-state response and the impact load on the support bearings in the rotor system. The rubbing impact between the blades and casing was accounted for. A fast method for calculating the response of fused structures was developed, which may be useful when designing the stiffness of the fusing structure.