An experimental study is described to investigate the negative effects of the tip clearance gap on the aerodynamic and acoustic performance of axial turbomachines. In addition to the increased broadband levels reported in the literature when the tip clearance is enlarged, significant level increases were observed within narrow frequency bands below the blade passing frequency. Measurements of the pressure and velocity fluctuations in the vicinity of the blade tips reveal that the tip clearance noise is associated with a rotating flow instability at the blade tip, which in turn is only present under reversed flow conditions in the tip clearance gap. A turbulence generator inserted into the tip clearance gap is found to be effective in eliminating the tip clearance noise and in improving the aerodynamic performance.

Experimental Study of Tip Clearance Losses and Noise in Axial Turbomachines

Aeroelastic analysis and structural parametric design of composite rotor blade

Lock-in phenomenon of tip clearance flow and its influence on aerodynamic damping under specified vibration on an axial transonic compressor rotor

Physical model for acoustic resonance in annular cavity structure

The noise control of a compressor has always been a hot spot in the field of industrial application. In this paper, the air inlet structure of the sound insulation hood of an air compressor unit was studied and improved. Acoustic finite element numerical simulation analysis of the sound insulation hood model was carried out using the acoustic software LMS Virtual Lab Acoustics. The simulation results were compared with the experimental data to verify the correctness of the model, and the theoretical results showed a good agreement with the experiment data. The sound insulation performance of the sound insulation hood under different structures was also investigated in this paper. The results show that the main source of unit noise leakage is outward radiation through the air inlet. In addition, the noise at the air inlet of the unit and the overall noise were significantly reduced compared with the traditional sound insulation hood upon installing 120° and 90° diaphragm structures on the inner wall of the air inlet. The optimization results show that the noise reduction effect of the sound insulation hood with a 90° diaphragm structure was better than that with a 120° diaphragm structure.

Performance Research and Optimization of Sound Insulation Hood of Air Compressor Unit

Experimental study of rotor blades vibration and noise in multistage high pressure compressor and their relevance

The invention provides a method for estimating thermo-acoustic fatigue lives of thin-walled structures on the basis of improved rain-flow counting processes. The method includes acquiring stress response time courses in response durations T of the aerospace thin-walled structures under the effect of thermo-acoustic load to obtain extreme value sequences of the stress response time courses of the thin-walled structures; pairing maximum values and minimum values of the stress response time courses of the thin-walled structures by the aid of the rain-flow cycle counting processes to obtain all rain-flow cycle counting pairs of the stress response time courses of the thin-walled structures; building rain-flow cycle matrixes of stress response of the thin-walled structures according to the rain-flow cycle counting pairs of the stress response time courses of the thin-walled structures; determining fatigue lives T of the thin-walled structures according to the rain-flow cycle matrixes of the stress response of the thin-walled structures on the basis of Morrow average stress models. The method has the advantages that the shortcoming of data missing due to divergent waves formed by left points in stress cycle counting procedures of the traditional rain-flow counting processes can be overcome by the aid of the method, and the correctness of computation results can be guaranteed.

Method for estimating thermo-acoustic fatigue lives of thin-walled structures on basis of improved rain-flow counting processes

In the design of advanced aircraft turbofan engine, applying the continuous fiber reinforced metal matrix composites(MMC), which have excellent properties of good mechanics, resistance to high temperatures and light mass, to manufacture some of the key components is the effective way to realize thrust increase and weight decrease. In order to realize the design and analysis to the structural integrity of this sort of composite components, with the continuous fiber reinforced metal matrix composites low pressure turbine(LPT) shaft structure as the object of study, mesoscopic mechanics method is applied to calculate mechanics properties of continuous fiber reinforced MMC; On this basis, applying composite mechanics parameters calculated by representative volume element (RVE) model as input value, meanwhile, from the point of mesoscopic mechanics method like the specific arrangement mode of fiber and matrix and the mechanics properties of MMC shaft to analyse response regularities of MMC shaft modal frequency that caused by variation of fiber volume content, layer angle, layer amount and boundary conditions of the shaft structure.

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Vibration Modal Analysis of Continuous Fiber Reinforced Metal Matrix Composites Low Pressure Turbine Shaft

The invention provides a method for predicting noise of aero-engines on the basis of multi-regression. The method includes acquiring time-domain signals of the internal noise of the aero-engines and working state parameter matrixes of the aero-engines; preprocessing the time-domain signals of the internal noise of the aero-engines to obtain 1/3 octave spectra and total sound pressure levels of the internal noise of the aero-engines; establishing multi-regression equations of sounds pressure levels of the internal noise of the aero-engines by the aid of least square processes according to the 1/3 octave spectra of the internal noise of the aero-engines and the working state parameter matrixes of the aero-engines; collecting working state parameters of the aero-engines in real time; inputting the corresponding working state parameters of the aero-engines in certain working states into the multi-regression equations of the sound pressure levels of the internal noise of the aero-engines to obtain linear analysis 1/3 octave spectra and total sound pressure levels of the internal noise of the aero-engines. The linear analysis 1/3 octave spectra and total sound pressure levels of the internal noise of the aero-engines correspond to the working states. The method has the advantages that residual errors are controlled, and accordingly the accuracy of load forecast results can be guaranteed.

Luan Xiaochi

Papers

Experimental study of rotor blades vibration and noise in multistage high pressure compressor and their relevance

Method for estimating thermo-acoustic fatigue lives of thin-walled structures on basis of improved rain-flow counting processes

Vibration Modal Analysis of Continuous Fiber Reinforced Metal Matrix Composites Low Pressure Turbine Shaft

Method for predicting noise of aero-engines on basis of multi-regression