Blade Excitation by Broad-Band Pressure Fluctuations in a Centrifugal Compressor

1988 ◽  
Vol 110 (1) ◽  
pp. 129-137 ◽  
Author(s):  
U. Haupt ◽  
M. Rautenberg ◽  
A. N. Abdel-Hamid
Keyword(s):  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Pressure Fluctuations ◽  
Broad Band ◽  
Rotating Stall ◽  
High Mass ◽  
Blade Vibration ◽  
Flow Angle ◽  
Unsteady Pressure

The mechanism of blade excitation during the operation of a high-mass-flow, high-pressure-ratio centrifugal compressor has been investigated. This was carried out in the compressor operating range below 60 percent of design speed and in the zone of unsteady flow occurrence, where considerable blade vibration has been measured but no periodic unsteady pressure pattern such as rotating stall could be identified. Experiments conducted to study the mechanism of interactions between flow and blades were accomplished using several measuring methods simultaneously, such as measurements of blade vibration, flow angle at impeller inlet, unsteady pressure at different meridional and peripheral locations, as well as flow visualization by means of oil pattern. Analysis of the measurements showed typical broad-band characteristics of the unsteady pressure field and also for the blade vibration behavior. Results of flow angle investigations at the impeller inlet together with the analysis of oil pattern show that the broad-band pressure fluctuations and blade excitation can be attributed to a strong reverse flow near the suction side of the radial blade in the shroud zone. This reverse flow has its source downstream of the impeller and is extending back up to a location ahead of the impeller inlet. Similar results were obtained when the compressor was operated with vaneless and vaned diffuser configurations.

A Dangerous Blade Vibration Phenomenon due to Unsteady Flow in Centrifugal Compressors

1993 ◽  
Author(s):  
D. Jin ◽  
H. Hasemann ◽  
U. Haupt ◽  
M. Rautenberg
Keyword(s):  
Unsteady Flow ◽  
Mass Flow ◽  
Reverse Flow ◽  
Broad Band ◽  
Rotating Stall ◽  
High Mass ◽  
Resonance Excitation ◽  
Blade Vibration ◽  
Unsteady Pressure ◽  
Vane Diffuser

Dangerous blade excitation caused by unsteady flow in a high pressure/high mass flow compressor running in a low mass flow region has been investigated. Experiments were carried out for compressors with two different types of vaned diffusers. Blade vibration was measured with strain gages while simultaneous unsteady pressure was measured with fast response dynamic transducers. All measured results were analysed in detail so that an in-depth understanding of blade excitation mechanism can be obtained. Firstly, the compressor with a straight-channel vane diffuser at reduced rotational speed of 12,300 rpm in an unstable operation region was considered. The analysis of blade vibration and unsteady pressure showed an unusual excitation phenomenon. Besides a strong blade vibration frequency component near the first blade mode frequency excited by the rotating stall cells existed another dangerous resonance excitation with first blade mode component which dominated the blade vibration spectrum. A detailed pressure signal analysis indicated that this blade vibration was excited by a broad band pressure fluctuation due to a strong reverse flow occurring simultaneously with the rotating stall. Further reducing the compressor mass flow to the operation point shortly before surge, the rotating stall was significantly weakened while the reverse flow kept its intensity until surge occurred. In this operation region blades suffered throughout a violent excitation of resonance because of the strong reverse flow. These blade excitation phenomena were also found in the next experiment for the compressor with a cambered vane diffuser at higher rotational speeds of nred = 13,500 and 14,000 rpm. The maximum strain values of blade vibration were obtained to quantitavely estimate the danger of blade vibration caused by this excitation.

Blade Excitation by Circumferentially Asymmetric Rotating Stall in Centrifugal Compressors

1992 ◽  
Author(s):  
D. Jin ◽  
U. Haupt ◽  
H. Hasemann ◽  
M. Rautenberg
Keyword(s):  
Pressure Ratio ◽  
Excitation Frequency ◽  
Fast Response ◽  
Rotating Stall ◽  
High Mass ◽  
Vibration Frequencies ◽  
Strain Gages ◽  
Blade Vibration ◽  
Pressure Pattern ◽  
Frequency Components

The excitation of blade vibration by circumferentially asymmetric rotating stall in a high pressure ratio, high mass flow centrifugal compressor with radial impeller and vaned diffusers has been investigated. This was accomplished experimentally by means of blade vibration measurements with strain gages mounted on the blades and simultaneous unsteady pressure measurements with fast response dynamic transducers. The earlier results showed rotating stall effects as the monofrequent excitation of blade vibration. However a more detailed analyses of blade vibration by very strong rotating stall in the speed range of 13,000–14,500 rpm displayed multiple frequency components of blade vibration besides the main excitation frequency caused by rotating stall. The frequency values were found to be related to frequencies of shaft rotation and rotating stall. The detailed analyses of the pressure signals of rotating stall obtained from dynamic transducers located at different circumferential positions on the shroud wall showed a different pressure pattern amplitude due to rotating stall. The circumferentially asymmetric amplitude profile of the rotating stall was an additional excitation of blade vibration. By aid of two-dimensioal Fourier analysis for the pressure pattern of rotating stall, a calculation method for blade vibration frequencies by circumferentially asymmetric rotating stall was developed. The predicted blade vibration frequencies corresponded to the frequency components on the blade vibration spectrum obtained from the strain gages.

scholarly journals Blade Vibration on Centrifugal Compressors: Blade Response to Different Excitation Conditions

1985 ◽  
Author(s):  
U. Haupt ◽  
K. Bammert ◽  
M. Rautenberg
Keyword(s):  
Pressure Ratio ◽  
Rotating Stall ◽  
High Mass ◽  
Blade Vibration ◽  
Vibration Measurements ◽  
High Pressure Ratio ◽  
Vibration Data ◽  
Impeller Outlet ◽  
Different Types ◽  
Inlet Zone

Results and analysis of blade vibration measurements on a high pressure ratio / high mass flow centrifugal compressor made with strain gages and using multichannel telemetry are described for compressors with 3 different types of vaned diffusers. Considerable high frequency blade excitation and vibration of the shallow region near the impeller outlet were observed. Initial progress to predict this dangerous excitation caused by the diffuser vanes was made with the help of FE computations using a simplified element system consisting of the vibrating zones of a 90° sector of the impeller. Satisfactory agreement with measured vibration data was achieved. The influence of rotating stall on blade excitation was investigated using different types of vaned diffusers leading to different numbers of rotating stall zones and variations in the rotational speed of the cells. Blade vibration intensity due to surge in conjunction with variations of the diffuser is also considered. Holographic interferometry was successfully applied to blade vibration measurements on compressors in operation. The investigation was aimed at studying the occurrence of blade modes and the vibratory behavior of the different blades near the interesting inlet zone. The occurrence of different constellations of blade modes at a resonance point and at an operating point far from resonance was demonstrated.

scholarly journals Effects of Variable Inlet Guide Vanes on Small Centrifugal Compressor Performance

1999 ◽  
Author(s):  
Minoru Ishino ◽  
Yuji Iwakiri ◽  
Akinobu Bessho ◽  
Hiroshi Uchida
Keyword(s):  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Flow Analysis ◽  
Flow Distribution ◽  
Suction Side ◽  
High Mass ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Compressor Performance

Variable inlet guide vanes (VIGVs) have been developed for a small centrifugal compressor of automobile turbocharger. The effects of pre-whirl flow generated by VIGVs on compressor performance have been studied experimentally. Furthermore, the flow condition in impeller passage of the compressor with VIGVs has been compared to that of the compressor without VIGVs by using three-dimensional flow analysis. The results of experimental study have shown that pre-whirl flow is advantageous to the efficiency and surge characteristics of compressor. A weak fluid oscillation, which usually occurs in the region of high pressure-ratio and high mass flow rates, has been controlled by using VIGVs. The results of calculation of the viscous compressible flow have shown that the pre-whirl generated by VIGVs is effective in decreasing the area of the reverse flow which occurs at shroud suction side and smoothing the flow distribution between shroud and hub at the impeller exit.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

Effect of Different Geometrical Inlet Pipes on a High Speed Centrifugal Compressor

2013 ◽  
Author(s):  
Ce Yang ◽  
Ben Zhao ◽  
C. C. Ma ◽  
Dazhong Lao ◽  
Mi Zhou
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Ratio ◽  
Inlet Pipe ◽  
Unsteady Pressure ◽  
Bent Pipe ◽  
Low Mass ◽  
Compressor Performance ◽  
Spectral Frequency ◽  
The One

Two different inlet configurations, including a straight pipe and a bent pipe, were experimentally tested and numerically simulated using a high-speed, low-mass flow centrifugal compressor. The pressure ratios of the compressor with the two inlet configurations were tested and then compared to illustrate the effect of the bent inlet pipe on the compressor. Furthermore, different circumferential positions of the bent inlet pipe relative to the volute are discussed for two purposes. One purpose is to describe the changes in the compressor performance that result from altering the circumferential position of the bent inlet pipe relative to the volute. This change in performance may be the so-called clocking effect, and its mechanism is different from the one in multistage turbomachinery. The other purpose is to investigate the unsteady flow for different matching states of the bent inlet pipe and volute. Thus, the frequency spectrum of unsteady pressure fluctuation was applied to analyze the aerodynamic response. Compared with the straight inlet pipe, the experimental results show that the pressure ratio is modulated and that the choke point is shifted in the bent inlet pipe. Similarly, the pressure ratio can be influenced by altering the circumferential position of the bent inlet pipe relative to the volute, which may have an effect on the unsteady pressure in the rotor section. Therefore, the magnitude of interest spectral frequency is significantly changed by clocking the bent inlet pipe.

scholarly journals On the Mechanism of Dangerous Blade Vibration due to Blade Flow Interactions on Centrifugal Compressors

1989 ◽  
Author(s):  
U. Haupt ◽  
D. F. Jin ◽  
M. Rautenberg
Keyword(s):  
Pressure Field ◽  
Reverse Flow ◽  
Wave Number ◽  
Resonance Excitation ◽  
Blade Vibration ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Part Load ◽  
Operation Conditions ◽  
Flow Interactions

Severe blade flow interactions at part load operation conditions were investigated on a centrifugal compressor with a vaned diffuser leading to material stresses beyond the allowable values. By means of a number of measurement and analysis techniques it could be found, that a stationary periodic pressure field is produced on the circumference by the vibrating blade itself, which is induced at resonance conditions by the peripheral pressure non-uniformity due to the outlet tube. This peripheral pressure field of an integer wave number intensifies the blade resonance excitation from downstream leading to an additivity effect between wave amplitude and blade displacement. The significant role in this mechanism plays the reverse flow near the corner shroud/suction side in the impeller, occurring at part load operation, which is controlled by the interaction of the tip angle of the vibrating blade and the flow angle at that location. It could be demonstrated, that this dangerous blade vibration — in addition — is the source of a shift of the surge line towards higher mass flow, reducing the compressor operating range considerably in this operating zone.

Some Studies on Low Solidity Vaned Diffusers of a Centrifugal Compressor Stage

2005 ◽  
Author(s):  
T. Ch. Siva Reddy ◽  
G. V. Ramana Murty ◽  
Prasad Mukkavilli ◽  
D. N. Reddy
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Recovery Coefficient ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Centrifugal Compressor Stage ◽  
Pressure Recovery Coefficient

Numerical simulation of impeller and low solidity vaned diffuser (LSD) of a centrifugal compressor stage is performed individually using CFX- BladeGen and BladeGenPlus codes. The tip mach number for the chosen study was 0.35. The same configuration was used for experimental investigation for a comparative study. The LSD vane is formed using standard NACA profile with marginal modification at trailing edge. The performance parameters obtained form numerical studies at the exit of impeller and the diffuser have been compared with the corresponding experimental data. These parameters are pressure ratio, polytropic efficiency and flow angle at the impeller exit where as the parameters those have been compared at the exit of diffuser are the static pressure recovery coefficient and the exit flow angle. In addition, the numerical prediction of the blade loading in terms of blade surface pressure distribution on LSD vane has been compared with the corresponding experimental results. Static pressure recovery coefficient and flow angle at diffuser exit is seen to match closely at higher flows. The difference at lower flows could be due to the effect of interaction between impeller and diffuser combinations, as the numerical analysis was done separately for impeller and diffuser and the effect of impeller diffuser interaction was not considered.

scholarly journals Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor

1998 ◽  
Author(s):  
I. Kassens ◽  
M. Rautenberg
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Guide Vane ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Inlet Guide Vane ◽  
Flow Measurements ◽  
Flow Angle ◽  
Partial Load ◽  
Measurement Location

In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller. The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured. Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.

Excitation of Blade Vibration due to Surge of Centrifugal Compressors

1992 ◽  
Author(s):  
D. Jin ◽  
U. Haupt ◽  
H. Hasemann ◽  
M. Rautenberg
Keyword(s):  
Centrifugal Compressor ◽  
Rotational Speed ◽  
High Performance ◽  
Dynamic Pressure ◽  
Rotating Stall ◽  
Blade Vibration ◽  
High Rotational Speed ◽  
Blade Thickness ◽  
Periodic Pressure ◽  
Compressor Surge

Centrifugal compressor surge at high rotational speed and reduced blade thickness can produce dangerous excitation effects which have numerous resulted in problems in the past. This paper presents an investigation of blade excitation during surge in a high performance single stage centrifugal compressor with various impeller and diffuser geometry. The blade vibration was measured using blade mounted strain gages. The flow characteristics during surge as the cause of blade excitation were simultaneously determined by fast response dynamic pressure transducers. The experiments have been performed using a radial and a backswept impeller, as well as a vanless and vaned diffusers. The rotational speed of the compressor was varied from 5,000 to 14,500 rpm. The characteristics of unsteady flow during surge, such as, the flow pattern of rotating stall and the non-periodic pressure fluctuation during surge were studied in detail. The experimental results demonstrated that, in addition to the excitation of rotating stall during surge, strong non-periodic pressure fluctuations at the beginning and the end of the surge induced dangerous blade excitations in all compressor configurations. The maximum strain values of blade vibration for all compressor versions at different rotational speeds of the compressor were measured to estimate the danger of blade excitation during surge. The results showed that the blade excitation during compressor surge with vaned diffusers is stronger than the excitation with a vanless diffuser and that the blade excitation with a radial impeller is stronger than the excitation with a backswept impeller.

Sign in / Sign up

Export Citation Format

Share Document