Impeller-Vaned Diffuser Interaction in a Centrifugal Compressor at Off Design Conditions

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
P. Gaetani ◽  
G. Persico ◽  
A. Mora ◽  
V. Dossena ◽  
C. Osnaghi
Keyword(s):  
Flow Rate ◽  
Strong Dependence ◽  
Maximum Flow ◽  
Fast Response ◽  
Huge Number ◽  
Vaned Diffuser ◽  
Experimental Campaign ◽  
Flow Features ◽  
Aero Engines ◽  
Operating Points

As centrifugal compressors find a huge number of applications in industry and in aero-engines, the detailed analysis and comprehension of the impeller-vaned diffuser interaction is of interest to improve the efficiency and the operating range. This paper presents the results of a wide experimental campaign devoted to the understanding of the impeller-diffuser interaction; in particular, the paper focuses on the features occurring when the compressor works in off design conditions. Data were taken at three operating points (near surge, best efficiency, and maximum flow rate point) in the impeller-vaned diffuser gap by a fast response probe; the single stage compressor runs at 12,500 RPM giving a peripheral Mach number of 0.77. At first, data are reduced to evidence the main impeller flow features, which are compared at different flow rates. Furthermore time mean diffuser effects on the impeller are commented and finally the impeller-diffuser interaction is discussed. Results evidence the effect of the diffuser on the impeller, mainly in terms of static pressure and flow velocity, which have a strong dependence on the flow rate.

Impeller–Vaned Diffuser Interaction in a Centrifugal Compressor at Off Design Conditions

2011 ◽  
Author(s):  
P. Gaetani ◽  
G. Persico ◽  
A. Mora ◽  
V. Dossena ◽  
C. Osnaghi
Keyword(s):  
Flow Rate ◽  
Strong Dependence ◽  
Maximum Flow ◽  
Fast Response ◽  
Huge Number ◽  
Vaned Diffuser ◽  
Experimental Campaign ◽  
Aero Engine ◽  
Flow Features ◽  
Operating Points

As centrifugal compressors find a huge number of applications in industry and in aero-engine, the detailed analysis and comprehension of the impeller–vaned diffuser interaction is of interest to improve the efficiency and the operating range. The paper presents the results of a wide experimental campaign devoted to the understanding of the impeller–diffuser interaction; in particular the paper focuses on the features occurring when the compressor works in off design conditions. Data were taken at 3 operating points (near surge, best efficiency and maximum flow rate point) in the impeller–vaned diffuser gap by a fast response probe; the single stage compressor runs at 12500 RPM giving peripheral Mach number of 0.77. At first, data are reduced to evidence the main impeller flow features which are compared at different flow rates. Furthermore time mean diffuser effects on the impeller are commented and finally the impeller–diffuser interaction is discussed. Results evidence the effect of the diffuser on the impeller, mainly in terms of static pressure and flow velocity, which have a strong dependence on the flow rate.

Impeller Rotating Stall as a Trigger for the Transition From Mild to Deep Surge in a Subsonic Centrifugal Compressor

1993 ◽  
Author(s):  
Beat Ribi ◽  
Georg Gyarmathy
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Critical Value ◽  
Rotating Stall ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
Compressor Map ◽  
Operating Points

The present paper concerns the transition from mild to deep surge in a single stage centrifugal compressor using a vaned diffuser. Time-resolved measurements of the mass flow rate and the static pressures at various locations of the compressor were analyzed for different diffuser geometries and different operating points in the compressor map. When the throttle valve was gradually closed at an impeller tip Mach number (Mu) above 0.4, the compressor showed first mild and then deep surge whereas at Mu=0.4 rotating stall was the dominant instability. This single-cell rotating stall was identified to be caused by the impeller. During mild surge at higher Mach numbers the instantaneous flow and pressure traces showed that the overall flow at the stage inlet intermittently dropped below the critical value associated with the occurence of impeller rotating stall. Rotating stall appeared for a while but vanished as soon as the flow increased again. With further throttling, however, a threshold was reached at which rotating stall triggered deep surge. The results show that triggering only occurred if the flow deficiency causing rotating stall persisted long enough to permit the stall cell to make at least one or two revolutions.

Combined Impeller-Diffuser Design and the Influence of Slotted Guide Vanes on the Performance of Radial Diffusers

2009 ◽  
Author(s):  
Philipp Epple ◽  
Mihai Miclea ◽  
Caslav Ilic ◽  
Antonio Delgado
Keyword(s):  
Flow Rate ◽  
Design Method ◽  
Maximum Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Vaned Diffuser ◽  
Advantages And Disadvantages ◽  
Major Loss ◽  
Working Principle ◽  
The One

Radial diffusers are devices to increase the static pressure of a radial impeller-diffuser-unit (IDU) and in many cases also its efficiency. A new design method for the coupled Impeller-Diffuser-Layout is proposed. This new design method is presented and the resulting theoretical differences of the vaned and vaneless diffusers are shown. It is known, also, that at high flow rates, the vaned diffusers will choke, i.e. the maximum flow rate of an IDU will be much less as the one of the impeller alone or an IDU with vaneless diffuser. In order to avoid the flow rate decrease in the vaned diffuser due to this blockage or choking, a new kind of diffuser is proposed: the slotted diffuser. The theoretical principles of chocking and the solution with the slotted diffusers are explained. In order to have an in depth understanding of its working principle, three IDU are numerically examinated: with vaneless diffuser, regular vaned diffuser and the new slotted diffuser. In general the slotted diffuser delivers approximately the same pressure and efficiency but a substantial higher flow rate than the vaned diffuser. The vaneless diffuser has the highest flow rate, but the lowest pressure. An in detail analysis of the gap losses between the exit of the impeller and the entry of the vaned regular and slotted diffusers is presented, unrevealing an major loss source in vaned IDU. Flow patterns of the different diffuser types are shown illustrating in a clear manner the working principle of these diffusers and their respective advantages and disadvantages. Finally, in order to validate the theoretical and numerical results, prototypes were built and measurements performed at a norm test rig according to DIN 24 163. Pictures of the prototypes as well as of the test rig are shown. The experimental results are in good agreement with the predictions of the numerical simulations confirming the theoretical and numerical investigations.

Impeller–Vaned Diffuser Interaction in a Centrifugal Compressor at the Best Efficiency Point

2011 ◽  
Author(s):  
P. Gaetani ◽  
G. Persico ◽  
A. Mora ◽  
V. Dossena ◽  
C. Osnaghi
Keyword(s):  
Centrifugal Compressor ◽  
High Performance ◽  
Fluid Dynamic ◽  
Fast Response ◽  
Cfd Simulations ◽  
Vaned Diffuser ◽  
Power Exchange ◽  
Complex Fluid ◽  
Point Data ◽  
Aero Engines

Centrifugal compressors find a huge number of applications in industry and in aero-engines; the detailed comprehension of the complex fluid-dynamic mechanisms occurring in these machines is crucial to improve their efficiency and their operating range. The paper presents a study on the impeller–vaned diffuser interaction in a high-performance compressor stage, in the frame of a wide experimental campaign devoted to the comprehension of unsteady flows in centrifugal compressor stages. The paper focuses on the best efficiency operating point. Data were collected in the impeller–vaned diffuser gap by applying a fast response probe. The impeller runs at 12500 RPM and the peripheral Mach number is 0.77. At first, data are reduced to highlight the main flow structures released by the impeller. CFD simulations — first verified against experimental data — were also performed to get detailed information of the flow field inside the impeller. The core of the paper is the discussion of the impeller–diffuser interaction. Results evidence the effect of the diffuser on the impeller in terms of static pressure and flow velocity. Moreover, the interaction process makes the average flow rate discharged by an impeller channel and the power exchange to be unsteady.

Outcome of Buccal Mucosal Graft Urethroplasty in Long Segment Anterior Urethral Stricture

2020 ◽  
Vol 19 (2) ◽  
pp. 64-68
Author(s):  
Mrinmoy Biswas ◽  
Sudip Das Gupta ◽  
Mohammed Mizanur Rahman ◽  
Sharif Mohammad Wasimuddin
Keyword(s):  
Urethral Stricture ◽  
Flow Rate ◽  
Surgical Outcome ◽  
Simple Technique ◽  
Anterior Segment ◽  
Maximum Flow ◽  
Anastomotic Site ◽  
Buccal Mucosal Graft ◽  
Male Patients

Objective: To assess the success of BMG urethroplasty in long segment anterior urethral stricture. Method: From January 2014 to December 2015, twenty male patients with long anterior segment urethral stricture were managed by BMG urethroplasty. After voiding trial they were followed up at 3 month with Uroflowmetry, RGU & MCU and PVR measurement by USG. Patients were further followed up with Uroflowmetry and PVR at 6 months interval.Successful outcome was defined as normal voiding with a maximum flow rate >15ml /sec and PVR<50 ml with consideration of maximum one attempt of OIU after catheter removal. Results: Mean stricture length was 5.2 cm (range 3-9 cm) and mean follow-up was 15.55 months (range 6-23 months). Only two patients developed stricture at proximal anastomotic site during follow-up. One of them voided normally after single attempt of OIU. Other one required second attempt of OIU and was considered as failure (5%). Conclusion: BMG urethroplasty is a simple technique with good surgical outcome. Bangladesh Journal of Urology, Vol. 19, No. 2, July 2016 p.64-68

Research on an axial-mounted dual magnetostrictive material rods-based electro-hydrostatic actuator

2021 ◽  
pp. 1045389X2110145
Author(s):  
Yuchuan Zhu ◽  
Chang Liu ◽  
Yunze Song ◽  
Long Chen ◽  
Yulei Jiang ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Flow Rate ◽  
Flow Distribution ◽  
Maximum Flow ◽  
Magnetostrictive Material ◽  
Simulation Techniques ◽  
Motion State ◽  
New Type ◽  
Output Characteristics ◽  
Active Rectification

In this paper, an electro-hydrostatic actuator driven by dual axial-mounted magnetostrictive material rods-based pumps (MMPs) with a new type of active rectification valve is designed in the current study. Based on flow distribution of the active rectification valve and driving energy provided by two MMPs, the actuator can output continuous and bidirectional displacement. By establishing a mathematical model of the actuating system, using simulation techniques, the change rule of hydraulic cylinder’s motion state caused by different driving signals are studied and analyzed. Test equipment platform is constructed in the laboratory to test the output characteristics and confirm the feasibility of the new concept. The experimental results indicate that the maximum flow rate can reach approximately 2.7 L·min−1, while the operating frequency is 180 Hz.

Lichen sclerosis–induced long segment anterior urethral stricture: The early outcome of one-stage repair using dorsolateral onlay buccal mucosa graft

2021 ◽  
pp. 039156032110033
Author(s):  
Atef Fathi ◽  
Omar Mohamed ◽  
Osama Mahmoud ◽  
Gamal A Alsagheer ◽  
Ahmed M Reyad ◽  
...  
Keyword(s):  
Success Rate ◽  
Urethral Stricture ◽  
Flow Rate ◽  
Urine Volume ◽  
Maximum Flow ◽  
Maximum Flow Rate ◽  
P Value ◽  
Onlay Graft ◽  
Voiding Symptoms ◽  
Stricture Recurrence

Background: Substitution urethroplasty using buccal mucosal grafts can be performed by several approaches including ventral onlay graft, dorsal onlay graft, or ventral urethrotomy with dorsal inlay graft. Our study aims to evaluate the surgical outcome of dorsolateral buccal mucosal graft for long segment anterior urethral stricture >6 cm in patients with Lichen sclerosus (LS). Methods: A retrospective study included patients who underwent repair for long segment anterior urethral stricture >6 cm due to LS between January 2013 and April 2019. All patients were followed-up at 3, 6, 9, and 12 months postoperatively and then yearly by clinical symptoms, uroflowmetry, and calculation of post-void residual urine volume. Retrograde urethrogram was requested for patients with voiding symptoms or decreased maximum flow rate. Stricture recurrence that required subsequent urethrotomy or urethroplasty was considered failure. The success rate and surgical complications were collected and analyzed. Results: Thirty patients were identified. The median age (range) was 39 (25–61) years and a median (range) stricture length was 8 (6–14) cm. Most of postoperative complications were of minor degree. The success rate at median follow-up of 15 (12–24) months was 86.5%. The median maximum flow rate increased significantly from 6 (2–11) ml/s preoperatively to 18 (range: 6–23) ml/s at the 6th month ( p value < 0.001). Conclusion: Dorsolateral buccal mucosal grafts urethroplasty for long anterior urethral stricture caused by LS has a high success rate and low risk of complications including stricture recurrence.

scholarly journals Improving Output Performance of a Resonant Piezoelectric Pump by Adding Proof Masses to a U-Shaped Piezoelectric Resonator

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 500
Author(s):  
Jian Chen ◽  
Wenzhi Gao ◽  
Changhai Liu ◽  
Liangguo He ◽  
Yishan Zeng
Keyword(s):  
Flow Rate ◽  
Maximum Flow ◽  
Working Fluid ◽  
Driving Voltage ◽  
Piezoelectric Resonator ◽  
Piezoelectric Pump ◽  
Compact Structure ◽  
Output Performance ◽  
Volume Efficiency ◽  
Working Efficiency

This study proposes the improvement of the output performance of a resonant piezoelectric pump by adding proof masses to the free ends of the prongs of a U-shaped piezoelectric resonator. Simulation analyses show that the out-of-phase resonant frequency of the developed resonator can be tuned more efficiently within a more compact structure to the optimal operating frequency of the check valves by adjusting the thickness of the proof masses, which ensures that both the resonator and the check valves can operate at the best condition in a piezoelectric pump. A separable prototype piezoelectric pump composed of the proposed resonator and two diaphragm pumps was designed and fabricated with outline dimensions of 30 mm × 37 mm × 54 mm. Experimental results demonstrate remarkable improvements in the output performance and working efficiency of the piezoelectric pump. With the working fluid of liquid water and under a sinusoidal driving voltage of 298.5 Vpp, the miniature pump can achieve the maximum flow rate of 2258.9 mL/min with the highest volume efficiency of 77.1% and power consumption of 2.12 W under zero backpressure at 311/312 Hz, and the highest backpressure of 157.3 kPa under zero flow rate at 383 Hz.

Surge in a Low-Speed Radial Compressor

1998 ◽  
Author(s):  
Corine Meuleman ◽  
Frank Willems ◽  
Rick de Lange ◽  
Bram de Jager
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Lumped Parameter Model ◽  
Pressure Oscillations ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Radial Compressor ◽  
Low Speed ◽  
Lumped Parameter

Surge is measured in a low-speed radial compressor with a vaned diffuser. For this system, the flow coefficient at surge is determined. This coefficient is a measure for the inducer inlet flow angle and is found to increase with increasing rotational speed. Moreover, the frequency and amplitude of the pressure oscillations during fully-developed surge are compared with results obtained with the Greitzer lumped parameter model. The measured surge frequency increases when the compressor mass flow is throttled to a smaller flow rate. Simulations show that the Greitzer model describes this relation reasonably well except for low rotational speeds. The predicted amplitude of the pressure rise oscillations is approximately two times too small when deep surge is met in the simulations. For classic surge, the agreement is worse. The amplitude is found to depend strongly on the shape of the compressor and throttle characteristic, which are not accurately known.

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