Backward Traveling Rotating Stall Waves in Centrifugal Compressors

2002 ◽  
Author(s):  
Z. S. Spakovsky
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
First Principles ◽  
Rotating Stall ◽  
Air Injection ◽  
System Stability ◽  
Centrifugal Compressors ◽  
Injection Scheme ◽  
Surge Margin ◽  
Low Order

Rotating stall waves that travel against the direction of rotor rotation are reported for the first time and a new, low-order analytical approach to model centrifugal compressor stability is introduced. The model is capable of dealing with unsteady radially swirling flows and the dynamic effects of impeller-diffuser component interaction as it occurs in centrifugal compression systems. A simple coupling criterion is developed from first principles to explain the interaction mechanism important for system stability. The model findings together with experimental data explain the mechanism for first-ever observed backward traveling rotating stall in centrifugal compressors with vaned diffusers. Based on the low-order model predictions, an air injection scheme between the impeller and the vaned diffuser is designed for the NASA Glenn CC3 high-speed centrifugal compressor. The steady air injection experiments show an increase of 25% in surge-margin with an injection mass flow of 0.5% of the compressor mass flow. In addition, it is experimentally demonstrated that this injection scheme is robust to impeller tip-clearance effects and that a reduced number of injectors can be applied for similar gains in surge-margin. The results presented in this paper firmly establish the connection between the experimentally observed dynamic phenomena in the NASA CC3 centrifugal compressor and a first principles based coupling criterion. In addition, guidelines are given for the design of centrifugal compressors with enhanced stability.

Backward Traveling Rotating Stall Waves in Centrifugal Compressors

2004 ◽  
Vol 126 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Z. S. Spakovszky
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
First Principles ◽  
Rotating Stall ◽  
Air Injection ◽  
System Stability ◽  
Centrifugal Compressors ◽  
Injection Scheme ◽  
Surge Margin ◽  
Low Order

Rotating stall waves that travel against the direction of rotor rotation are reported for the first time and a new, low-order analytical approach to model centrifugal compressor stability is introduced. The model is capable of dealing with unsteady radially swirling flows and the dynamic effects of impeller-diffuser component interaction as it occurs in centrifugal compression systems. A simple coupling criterion is developed from first principles to explain the interaction mechanism important for system stability. The model findings together with experimental data explain the mechanism for first-ever observed backward traveling rotating stall in centrifugal compressors with vaned diffusers. Based on the low-order model predictions, an air injection scheme between the impeller and the vaned diffuser is designed for the NASA Glenn CC3 high-speed centrifugal compressor. The steady air injection experiments show an increase of 25% in surge-margin with an injection mass flow of 0.5% of the compressor mass flow. In addition, it is experimentally demonstrated that this injection scheme is robust to impeller tip-clearance effects and that a reduced number of injectors can be applied for similar gains in surge-margin. The results presented in this paper firmly establish the connection between the experimentally observed dynamic phenomena in the NASA CC3 centrifugal compressor and a first principles based coupling criterion. In addition, guidelines are given for the design of centrifugal compressors with enhanced stability.       Winner of the “Best Paper Award,” Turbomachinery Committee

Numerical Investigation of Rotating Stall Characteristics and Active Stall Control in Centrifugal Compressors

2014 ◽  
Author(s):  
Taher Halawa ◽  
Mohamed Alqaradawi ◽  
Osama Badr ◽  
Mohamed S. Gadala
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Air Injection ◽  
Tip Leakage Flow ◽  
Centrifugal Compressors ◽  
Flow Rates ◽  
Injection Angle ◽  
Mass Flow Rates

This paper focuses on providing better view for the understanding of rotating stall phenomenon in centrifugal compressors by using numerical simulations and presents a study of the role of air injection method in delaying stall inception by using different injection parameters aiming at increasing the efficiency of this method. Results showed that the formation of stall begins at the impeller inlet due to early flow separation at low mass flow rates and due to the increase of the turbulence level and the absence of fluid orientation guidance at the vaneless region. The flow weakness causes back flow that results in the formation of the tip leakage flow which causes stall development with time. Results also showed that using air injection at specified locations at the vaneless shroud surface at injection angle of 20° and with injection mass flow rate of 1.5% of the inlet design mass flow rate, can delay the stall onset to happen at lower mass flow rate about 3.8 kg/s comparing with using injection with angle of 10° with different injection mass flow rates and also comparing with the case of no injection.

Numerical Simulation of Stall Development Into Surge and Stall Control Using Air Injection in Centrifugal Compressors

2014 ◽  
Author(s):  
Taher Halawa ◽  
Mohamed Alqaradawi ◽  
Osama Badr ◽  
Mohamed S. Gadala
Keyword(s):  
Numerical Simulation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Air Injection ◽  
Good Effect ◽  
Sudden Increase ◽  
Centrifugal Compressors ◽  
Surge Margin

This study presents a numerical simulation of the formation of rotating stall and the initiation of surge in order to study the connection between stall and surge in centrifugal compressors. Also, the current paper introduces an optimization of the air injection method as a way to increase the surge margin. Results showed that during stall, the compressor is exposed to velocity and pressure fluctuations varying with time, and these fluctuations are increased suddenly and causing surge initiation. The major part which is responsible for the sudden increase in fluctuations is the vaneless region because it was found that the problem starts at the impeller exit near the shroud surface and then transfers to the impeller inlet. Results also showed that during surge, forces on the impeller blades increase to nearly double of its initial value and then decrease again. By using air injection at the vaneless region with different injection angles, it was found that injection with angle of 30° has a good effect on preventing surge and minimizing the pressure fluctuations comparing to other injection angles results. Results showed finally that the surge margin can be increased by using the injection with angle of 30° and with injection mass flow rate of 1% of the design inlet mass flow rate and this causes the surge limit to shift from 4 kg/s to 3.9 kg/s.

Numerical Investigation of Steady Air Injection Flow to Control Rotating Stall in Centrifugal Compressors

2014 ◽  
Author(s):  
Taher Halawa ◽  
Mohamed Alqaradawi ◽  
Osama Badr ◽  
Mohamed S. Gadala
Keyword(s):  
Kinetic Energy ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Air Injection ◽  
Centrifugal Compressors ◽  
Injection Angle ◽  
Injection Method ◽  
Vane Angle

This paper concerns the role of air injection method in stabilization and stall control in centrifugal compressors. The main aim is to find the best arrangement of air injection parameters such as injection angle and injection mass flow rate in order to optimize the injection performance for stabilizing the compressor and increasing the surge margin. Numerical model was built to simulate high speed transonic centrifugal compressor working at an operating point close to surge. Air was injected at 12 locations at the vaneless region between the impeller and the diffuser at shroud surface with 5 different injection angles and 3 different injection mass flow rates. Results showed that the best injection method is when using an injection angle of 30° with injection mass flow rate of 1.5% of the design mass flow rate and the worst injection method is the injection at angle of 180° (reverse tangent injection). Results also indicated that by using air injection, the number of stalled diffuser passages is decreased compared to the case of no injection. The most significant result of this paper is that using an angle of injection around twice the value of the diffuser vane angle gives the best results and makes the ideal correction of the fluid kinetic energy and fluid angle at the diffuser inlet. It was found that injecting air at an angle less than the diffuser vane angle weakens the effect of injection and doesn’t increase kinetic energy of the fluid at diffuser inlet. It was also found that injecting air at an angle larger than the diffuser vane angle corrects the fluid direction but, at the same time, decreases the fluid kinetic energy at diffuser inlet.

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.

Effects of Non-Axisymmetric Volute on Rotating Stall in the Vaneless Diffuser of a Centrifugal Compressor

2020 ◽  
Author(s):  
Zitian Niu ◽  
Zhenzhong Sun ◽  
Baotong Wang ◽  
Xinqian Zheng
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Stability Boundary ◽  
Rotating Stall ◽  
Evolution Process ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Centrifugal Compressors ◽  
Specific Location

Abstract Rotating stall is an important unstable flow phenomenon that leads to performance degradation and limits the stability boundary in centrifugal compressors. The volute is one of the sources to induce the non-axisymmetric flow in a centrifugal compressor, which has an important effect on the performance of compressors. However, the influence of volute on rotating stall is not clear. Therefore, the effects of volute on rotating stall by experimental and numerical simulation have been explored in this paper. It’s shown that one rotating stall cell generates in a specific location and disappears in another specific location of the vaneless diffuser as a result of the distorted flow field caused by the volute. Also, the cells cannot stably rotate in a whole circle. The frequency related to rotating stall captured in the experiment is 43.9% of the impeller passing frequency (IPF), while it is 44.7% of IPF captured by three-dimensional unsteady numerical simulation, which proves the accuracy of the numerical method in this study. The numerical simulation further reveals that the stall cell initialized in a specific location can be split into several cells during the evolution process. The reason for this is that the blockage in the vaneless diffuser induced by rotating stall is weakened by the mainstream from the impeller exit to make one initialized cell disperse into several ones. The volute has an important influence on the generation and evolution process of the rotating stall cells of compressors. By optimizing volute geometry to reduce the distortion of the flow field, it is expected that rotating stall can be weakened or suppressed, which is helpful to widen the operating range of centrifugal compressors.

scholarly journals Surge Margin Optimization of Centrifugal Compressors Using a New Objective Function Based on Local Flow Parameters

2019 ◽  
Vol 4 (4) ◽  
pp. 42
Author(s):  
Johannes Ratz ◽  
Sebastian Leichtfuß ◽  
Maximilian Beck ◽  
Heinz-Peter Schiffer ◽  
Friedrich Fröhlig
Keyword(s):  
Objective Function ◽  
Centrifugal Compressor ◽  
Computational Effort ◽  
Angle Distribution ◽  
Centrifugal Compressors ◽  
Local Flow ◽  
Vaned Diffuser ◽  
Flow Parameters ◽  
Surge Margin ◽  
Beta Angle

Currently, 3D-CFD design optimization of centrifugal compressors in terms of the surge margin is one major unresolved issue. On that account, this paper introduces a new kind of objective function. The objective function is based on local flow parameters present at the design point of the centrifugal compressor. A centrifugal compressor with a vaned diffuser is considered to demonstrate the performance of this approach. By means of a variation of the beta angle distribution of the impeller and diffuser blade, 73 design variations are generated, and several local flow parameters are evaluated. Finally, the most promising flow parameter is transferred into an objective function, and an optimization is carried out. It is shown that the new approach delivers similar results as a comparable optimization with a classic objective function using two operating points for surge margin estimation, but with less computational effort since no second operating point near the surge needs to be considered.

Centrifugal Compressor Inlet Guide Vanes for Increased Surge Margin

1991 ◽  
Vol 113 (4) ◽  
pp. 696-702 ◽  
Author(s):  
C. Rodgers
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
System Stability ◽  
Negative Slope ◽  
Vaned Diffuser ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Surge Margin ◽  
Compressor Inlet ◽  
Surge Line

This paper describes the results of compressor rig testing with a moderately high specific speed, high inducer Mack number, single-stage centrifugal compressor, with a vaned diffuser, and adjustable inlet guide vanes (IGVs). The results showed that the high-speed surge margin was considerably extended by the regulation of the IGVs, even though the vaned diffuser was apparently operating stalled. Simplified one-dimensional analysis of the impeller and diffuser performances indicated that at inducer tip Mach numbers approaching and exceeding unity, the high-speed surge line was triggered by inducer stall. Also, IGV regulation increased impeller stability. This permitted the diffuser to operate stalled, providing the net compression system stability remained on a negative slope.

Performance Characteristics of a Centrifugal Compressor with Air Injection

1973 ◽  
Vol 187 (1) ◽  
pp. 425-434 ◽  
Author(s):  
J. D. Ledger ◽  
R. S. Benson ◽  
H. Furukawa
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Mass ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Performance Characteristics ◽  
Air Injection ◽  
Delivery Pressure ◽  
Mass Flow Rates ◽  
The Right

The parameters which influence the performance characteristics of centrifugal compressors with air injection through nozzles at the rotor tip are developed using both dimensional analysis and a simple model. Experiments on a small centrifugal compressor show that the injection air pressure is the main influence on the overall performance such as excess torque, increased delivery pressure and increased delivery flow. With air injection the pressure-mass flow characteristics are displaced to the right with surge occurring at increased total mass flow rates and the overall pressure ratio across the compressor is increased for the same total mass flow.

The Impact of Reciprocating Compressor Pulsations on the Surge Margin of Centrifugal Compressors

2016 ◽  
Author(s):  
Klaus Brun ◽  
Rainer Kurz ◽  
Sarah Simons
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Pulsation ◽  
Numerical Approach ◽  
Piping System ◽  
Analysis Tool ◽  
Reciprocating Compressor ◽  
Centrifugal Compressors ◽  
Surge Margin ◽  
Periodic Pressure ◽  
The Impact

Pressure pulsations into a centrifugal compressor can move its operating point into surge. This is concerning in pipeline stations where centrifugal compressors operate in series/parallel with reciprocating compressors. Sparks (1983), Kurz et al., (2006), and Brun et al., (2014) provided predictions on the impact of periodic pressure pulsation on the behavior of a centrifugal compressor. This interaction is known as the “Compressor Dynamic Response” (CDR) theory. Although the CDR describes the impact of the nearby piping system on the compressor surge and pulsation amplification, it has limited usefulness as a quantitative analysis tool, due to the lack of prediction tools and test data for comparison. Testing of compressor mixed operation was performed in an air loop to quantify the impact of periodic pressure pulsation from a reciprocating compressor on the surge margin of a centrifugal compressor. This data was utilized to validate predictions from Sparks' CDR theory and Brun's numerical approach. A 50 hp single-stage, double-acting reciprocating compressor provided inlet pulsations into a two-stage 700 hp centrifugal compressor. Tests were performed over a range of pulsation excitation amplitudes, frequencies, and pipe geometry variations to determine the impact of piping impedance and resonance responses. Results provided clear evidence that pulsations can reduce the surge margin of centrifugal compressors and that geometry of the piping system immediately upstream and downstream of a centrifugal compressor will have an impact on the surge margin reduction. Surge margin reductions of <30% were observed for high centrifugal compressor inlet suction pulsation.

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