The Investigation of Axial Compressor With Aggressive Flow Path Near Stall Condition

2020 ◽  
Author(s):  
Lele Ming ◽  
Yadong Wu ◽  
Hua Ouyang
Keyword(s):  
Axial Compressor ◽  
Flow Path ◽  
Rotating Stall ◽  
Frequency Characteristics ◽  
Test Facility ◽  
Frequency Method ◽  
Transition Processes ◽  
Fluctuating Pressure ◽  
Time Frequency ◽  
Multistage Compressor

Abstract Rotating stall is an unsteady flow phenomenon in flow rate reduction process of axial compressor. Single or multiple stall cells can be found in blade passage, rotating circumferentially at frequency ranging from 20% to 80% of compressor rotating frequency. Rotating stall may further lead to surge, then mass flow and pressure ratio of the compressor decrease rapidly while vibration amplitude of bearing fulcrum increases significantly, which would affect safety operation of the aero-engine. This paper reports the study on a multistage compressor with special-shaped aggressive flow path, which is significantly different from the conventional compressor with its meridian flow path midline parallel or nearly parallel to the rotating shaft axis. To study rotating stall and surge characteristics of multistage compressor with inlet distortion, this paper takes a 4.5-stage axial compressor as research object which has special S-shaped meridian flow path. On SJTU compressor test facility, the author carries out multidisciplinary tests on compressor dynamic performance (stator LE/TE and inter-stage fluctuating pressure measured by fluctuating pressure transducers, vibration measured by acceleration transducers, and dynamic stress measured by pasting strain transducers on the surface of stator blade). And in subsequent surge experiment, stall and surge signals at different rotating speeds are successfully captured. With above test data, axial, radial and circumferential instability development characteristics are studied by time domain correlation analysis, frequency domain power spectrum and coherence analysis, which preliminarily reveals the generation, development, propagation and elimination characteristics of rotating stall and surge. Meanwhile, in view of time-frequency characteristics of two instability transition processes, time-frequency analysis method based on Choi-Williams distribution model is adopted to capture instantaneous frequency characteristics. The results show that instability phenomenon exhibits quasi-exponential change in instability transition processes. Compared with traditional methods, time-frequency method is more effective in characterizing strong time-varying instability signals such as rotating stall and surge.

scholarly journals МЕТОД РАСЧЁТА ТЕРМОГАЗОДИНАМИЧЕСКИХ ПАРАМЕТРОВ ТУРБОВАЛЬНОГО ГАЗОТУРБИННОГО ДВИГАТЕЛЯ НА ОСНОВЕ ПОВЕНЦОВОГО ОПИСАНИЯ ЛОПАТОЧНЫХ МАШИН. ЧАСТЬ II. ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ СТУПЕНЕЙ И МНОГОСТУПЕНЧАТЫХ КОМПРЕССОРОВ

2019 ◽  
pp. 18-28 ◽  
Author(s):  
Людмила Георгиевна Бойко ◽  
Александр Евгеньевич Демин ◽  
Наталия Владимировна Пижанкова
Keyword(s):  
Gas Turbine ◽  
Calculation Method ◽  
Axial Compressor ◽  
Flow Path ◽  
Dynamic Parameters ◽  
Operating Characteristics ◽  
Program Complex ◽  
Gas Dynamic ◽  
Multistage Compressor ◽  
Multistage Axial Compressor

Gas Turbine Engine (GTE) operating characteristics such as thrust (or power), specific fuel consumption and other cycle parameters on different regimes, can be determined by engine modeling and applying correspondent calculation method. Its accuracy is the function of the engine’s element maps definition precision. So these maps representations influence for engines investigation results significantly. Main points and equation system for engine performances calculation method were represented in Part I of this article. The method gives an opportunity for the flow path thermodynamical parameters and engine integral values analyzing by using multistage axial blade machines blade-to-blade descriptions. The compressor and gas turbine and parameters are getting by special program modules, adding to the engine operating characteristics investigation program complex. These modules use the flow path and cascade middle radius geometrical parameters as the data for calculation. The goal of this article is the representation of the method for axial stages and multistage compressors performances definition. The calculation technique is based on one-dimensional (1D) multistage axial compressor flow description. Proposed 1D flow analysis method allows to get the multistage axial compressor maps taking into account the blade-to-blade gaps flow bleeding and by-pass. The method including is founded on the thermal and gas dynamic equations and turbomachinery theoretical dependences and empirical functions for losses and deviation angles determination. Besides, the representing method allows to calculate gas dynamic parameters, velocity triangles, angles of attack, evaluate their deviations from optimal values, hydraulic losses. Also, it can show accordance of stages working on different regimes, find the stage, which is a reason for compressor instability, and stall margin. This method can be used in GTE mathematic simulation, founded on blade-to-blade description multistage blade machines or also in multistage compressor designing. The proposed method gives the opportunity to control the stator variable vanes stagger angles control and to analyze its influence for stage and multistage compressor gas dynamic parameters and maps.

scholarly journals Time-frequency energy analysis of deepwater explosion shock wave signals based on HHT

2021 ◽  
Vol 336 ◽  
pp. 01017
Author(s):  
Linna Li ◽  
Yue You
Keyword(s):  
Shock Wave ◽  
Deep Water ◽  
Signal Analysis ◽  
Three Dimensional ◽  
Frequency Characteristics ◽  
Water Medium ◽  
Frequency Method ◽  
Time Frequency ◽  
Marginal Spectrum ◽  
Explosion Load

In order to study the time-frequency characteristics of shock wave signals under deep water explosion conditions, experiments are performed using water medium explosion containers to simulate different water depth conditions, and signal analysis is performed on the shock wave data obtained in the experiments. Traditional time-frequency analysis methods such as Fourier transform and wavelet transform have many limitations on deep-water explosion shock wave signal analysis, the HHT method is used to analyse the experimental data from the three-dimensional Hilbert spectrum, marginal spectrum and instantaneous energy spectrum. The results show that the time-frequency method can effectively extract the frequency components of the deep-water explosion load signal in different periods. It provides a reference for people to understand the time frequency characteristics of shock wave signals in deep water.

Effects of Co- and Counter-Rotating Inlet Distortions on a 5-Stage HP-Compressor

2002 ◽  
Author(s):  
Thomas Peters ◽  
Leonhard Fottner
Keyword(s):  
Axial Compressor ◽  
Rotating Stall ◽  
Sensor Data ◽  
Test Facility ◽  
Stall Inception ◽  
Rotation Direction ◽  
Inlet Distortion ◽  
Surge Margin ◽  
Counter Rotation ◽  
First Results

The HP-compressor of a twin-spool aero-engine experiences a rotating inlet distortion if a rotating stall in the upstream LP-compressor occurs. This may lead to HP-compressor instability like rotating stall or surge and has even more serious effects on the performance and behavior of the engine than rotating stall in the LP-compressor alone. Studies on compressor flow instabilities are carried out at the 5-stage HP-compressor Rig212, developed in the TurboUnion RB199 jet engine programme. In order to investigate rotating inlet distortions, the axial compressor test facility is equipped with a distortion generator rotating at high speeds in the compressor inlet duct. A disk with a sectorial total pressure loss screen simulates an upstream rotating stall. It produces a rotating inlet distortion with up to 65% of the compressor’s design speed in co- or counter-rotation direction. This paper extends the presentation of first results by Peters et al. [1] and covers both, co- and counter-rotating inlet distortions and their influence on the compressor surge margin. Hot-wire sensor data are analysed to investigate the stall inception process and the response of the compressor flow field to the excitation by the rotating inlet distortion. The experimental detection of aerodynamic eigenfrequencies of the compressor is compared with numerical results from a compressor model developed by Hu and Fottner [2].

scholarly journals Time–Frequency-Analysis-Based Blind Modulation Classification for Multiple-Antenna Systems

Sensors ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 231
Author(s):  
Weiheng Jiang ◽  
Xiaogang Wu ◽  
Yimou Wang ◽  
Bolin Chen ◽  
Wenjiang Feng ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Classification Accuracy ◽  
Communication Systems ◽  
Mimo Systems ◽  
Decision Fusion ◽  
Frequency Characteristics ◽  
Modulation Classification ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Average Classification Accuracy

Blind modulation classification is an important step in implementing cognitive radio networks. The multiple-input multiple-output (MIMO) technique is widely used in military and civil communication systems. Due to the lack of prior information about channel parameters and the overlapping of signals in MIMO systems, the traditional likelihood-based and feature-based approaches cannot be applied in these scenarios directly. Hence, in this paper, to resolve the problem of blind modulation classification in MIMO systems, the time–frequency analysis method based on the windowed short-time Fourier transform was used to analyze the time–frequency characteristics of time-domain modulated signals. Then, the extracted time–frequency characteristics are converted into red–green–blue (RGB) spectrogram images, and the convolutional neural network based on transfer learning was applied to classify the modulation types according to the RGB spectrogram images. Finally, a decision fusion module was used to fuse the classification results of all the receiving antennas. Through simulations, we analyzed the classification performance at different signal-to-noise ratios (SNRs); the results indicate that, for the single-input single-output (SISO) network, our proposed scheme can achieve 92.37% and 99.12% average classification accuracy at SNRs of −4 and 10 dB, respectively. For the MIMO network, our scheme achieves 80.42% and 87.92% average classification accuracy at −4 and 10 dB, respectively. The proposed method greatly improves the accuracy of modulation classification in MIMO networks.

Fuzzified time-frequency method for identification and localization of power system faults

2021 ◽  
pp. 1-13
Author(s):  
Pullabhatla Srikanth ◽  
Chiranjib Koley
Keyword(s):  
Power System ◽  
High Accuracy ◽  
Fuzzy Decision ◽  
Frequency Method ◽  
Time Frequency ◽  
Novel Approach ◽  
S Transform ◽  
Different Types ◽  
Power System Faults ◽  
Frequency Magnitude

In this work, different types of power system faults at various distances have been identified using a novel approach based on Discrete S-Transform clubbed with a Fuzzy decision box. The area under the maximum values of the dilated Gaussian windows in the time-frequency domain has been used as the critical input values to the fuzzy machine. In this work, IEEE-9 and IEEE-14 bus systems have been considered as the test systems for validating the proposed methodology for identification and localization of Power System Faults. The proposed algorithm can identify different power system faults like Asymmetrical Phase Faults, Asymmetrical Ground Faults, and Symmetrical Phase faults, occurring at 20% to 80% of the transmission line. The study reveals that the variation in distance and type of fault creates a change in time-frequency magnitude in a unique pattern. The method can identify and locate the faulted bus with high accuracy in comparison to SVM.

Modeling of Discrete Tip Injection in a Two-Dimensional Streamline Curvature Method

2012 ◽  
Author(s):  
Roland Matzgeller ◽  
Richard Pichler
Keyword(s):  
Rotating Stall ◽  
Streamline Curvature ◽  
Measurement Results ◽  
Compressor Design ◽  
Multistage Compressor ◽  
Physical Effects ◽  
Tip Injection ◽  
Stability Enhancement ◽  
Good Agreement ◽  
Streamline Curvature Method

Fluid injection at the tip of highly loaded compressor rotors is known to be effective in suppressing the onset of rotating stall and eventually compressor instability. However, using such stability enhancement methods in a multistage compressor might not only stabilize certain stages but has also an impact on radial and axial matching. In order to account for tip injection during the early stages of compressor design, this paper focuses on the development of a method to model the physical effects underlying tip injection within a streamline curvature method. With the help of system identification it could be shown that a rotor subject to the discrete jets of tip injection adapts to the varying flow conditions according to a first order model. This information was used to generate a time-dependent input for the steady equations used with a streamline curvature method and eventually to model the unsteady response of the rotor to tip injection. Comparing the results obtained with the enhanced streamline curvature model to measurement results, good agreement could be shown which raised confidence that the influence of tip injection on axial and radial matching was sufficiently captured.

scholarly journals Frequency Characteristics of Fluctuating Pressure on Rotor Blade in a Propeller Fan.

2003 ◽  
Vol 46 (1) ◽  
pp. 163-172 ◽  
Author(s):  
Choon-Man JANG ◽  
Masato FURUKAWA ◽  
Masahiro INOUE
Keyword(s):  
Rotor Blade ◽  
Frequency Characteristics ◽  
Fluctuating Pressure

INVESTIGATION ON MODE CHARACTERISTICS OF ROTATING INSTABILITY AND ROTATING STALL IN AN AXIAL COMPRESSOR

2021 ◽  
pp. 1-24
Author(s):  
Zeyuan Yang ◽  
Yadong Wu ◽  
Hua Ouyang
Keyword(s):  
Axial Compressor ◽  
Calibration Method ◽  
Acoustic Mode ◽  
Rotating Stall ◽  
Frequency Spectra ◽  
Compressor Rotor ◽  
Mode Decomposition ◽  
Aerodynamic Instability ◽  
Rotating Instability ◽  
Mode Order

Abstract Rotating instability (RI) and rotating stall (RS) are two types of aerodynamic instability in axial compressors. The former features the side-by-side peaks below the blade passing frequency (BPF) in frequency spectra, and the latter represents one or more stall cells rotating in the compressor. This paper presents an experimental on the nearfield pressure and farfield acoustic characteristics of RI phenomenon in a low-speed axial compressor rotor, which endures both RI and RS at several working conditions. In order to obtain the high-order modes of RI and other aerodynamic instability, a total of 9 or 20 Kulites are circumferentially mounted on the casing wall to measure the nearfield pressure fluctuation using a mode order calibration method. Meantime in the farfield 16 microphones are planted to measure the acoustic mode order using the compressive sensing method. Through calibration the experiments acquire the mode orders generated by RI and the interaction between RI and BPF, which is higher than the number of transducers. As for RS, the mode decomposition shows a mode order of 1, indicating one single stall cell rotating in the compressor. This experiment also shows that amplitude of RI modes is decreased when RS occurs, but RS modes and RI modes will both be enhanced if the flow rate is further reduced. This experiment reveals that RI experiences three stages of “strengthen-weaken-strengthen”, and hence RI may not be regarded only as “prestall” disturbance.

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