An Experimental Investigation of Stator Induced Unsteadiness on Centrifugal Impeller Outflow

1996 ◽  
Vol 118 (1) ◽  
pp. 41-51 ◽  
Author(s):  
M. Ubaldi ◽  
P. Zunino ◽  
G. Barigozzi ◽  
A. Cattanei
Keyword(s):  
Static Pressure ◽  
Fast Response ◽  
Centrifugal Impeller ◽  
Flow Measurements ◽  
Vaned Diffuser ◽  
Pressure Transducers ◽  
Front End ◽  
Impeller Outlet ◽  
Instantaneous Flow Field ◽  
Response Pressure

Detailed flow measurements were taken in a centrifugal turbomachine model to investigate the aerodynamic influence of the vaned diffuser on the impeller flow. The model consists of an unshrouded centrifugal impeller with backswept blades and a rotatable vaned diffuser, which enables a continuous variation of the vaned diffuser location with respect to the measuring points. Phase-locked ensemble-averaged velocity components have been measured with hot-wire probes at the impeller outlet for 30 different relative positions of the probe with respect to the diffuser vanes. The data also include the distribution of the ensemble-averaged static pressure at the impeller front end, taken by means of miniature fast response pressure transducers flush-mounted at the impeller stationary casing. By circumferentially averaging the results obtained for the different circumferential probe locations, the periodically perturbed impeller flow has been split into a relative steady flow and a stator-generated unsteadiness. The results for the different probe positions have also been correlated in time to obtain instantaneous flow field images in the relative frame, which provide information on the various aspects of the diffuser vane upstream influence on the relative flow leaving the impeller.

An Experimental Investigation of Stator Induced Unsteadiness on Centrifugal Impeller Outflow

1994 ◽  
Author(s):  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Glovanna Barigozzi ◽  
Andrea Cattanel
Keyword(s):  
Static Pressure ◽  
Fast Response ◽  
Centrifugal Impeller ◽  
Flow Measurements ◽  
Vaned Diffuser ◽  
Pressure Transducers ◽  
Front End ◽  
Impeller Outlet ◽  
Instantaneous Flow Field ◽  
Response Pressure

Detailed flow measurements were taken in a centrifugal turbomachine model to investigate the aerodynamic influence of the vaned diffuser on the impeller flow. The model consists of an unshrouded centrifugal impeller with backswept blades and a rotatable vaned diffuser which enables a continuous variation of the vaned diffuser location with respect to the measuring points. Phase locked ensemble averaged velocity components have been measured with hot wire probes at the impeller outlet for 30 different relative positions of the probe with respect to the diffuser vanes. The data also include the distribution of the ensemble averaged static pressure at the impeller front end, taken by means of miniature fast response pressure transducers flush mounted at the impeller stationary casing. By circumferentially averaging the results obtained for the different circumferential probe locations, the periodically perturbed impeller flow has been split into a relative steady flow and a stator generated unsteadiness. The results for the different probe positions have also been correlated in time to obtain instantaneous flow field images in the relative frame, which provide information on the various aspects of the diffuser vane upstream influence on the relative flow leaving the impeller.

scholarly journals Stator Exit Flow Fields in the Multistage Environment of an Axial Compressor

1995 ◽  
Author(s):  
M. Jung ◽  
J. Eikelmann
Keyword(s):  
Steady State ◽  
Axial Compressor ◽  
Fast Response ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Flow Measurements ◽  
High Loss ◽  
Pressure Transducers ◽  
Dominant Feature ◽  
Response Pressure

Detailed measurements have been taken at the exit of the four stages of an axial compressor of industrial design for two operating points. Pneumatic probes and fast response pressure transducers have been used. Special attention is paid to the endwall flow near hub and casing and the stage-by-stage development of this region of high loss. The steady state investigations show the leakage flow to be the dominant feature of the endwall region near the hub. This is also apparent near the casing for the unshrouded and adjustable stator blades. At the hub this flow phenomenon intensifies axially from stage-to-stage and with increased aerodynamic loading. Variations in geometry of the radial clearance at the casing have been investigated to understand the structure and effects of the leakage flow. Unsteady state flow measurements confirm the steady state results. Further, the endwall flow and especially the leakage vortex are detected as regions of high periodic fluctuations.

Experimental Study of Centrifugal Impeller Discharge Flow in Vaneless and Vaned Diffusers

1984 ◽  
Vol 106 (2) ◽  
pp. 455-467 ◽  
Author(s):  
M. Inoue ◽  
N. A. Cumpsty
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Centrifugal Impeller ◽  
Data Logging ◽  
Reference Case ◽  
Vaned Diffuser ◽  
Impeller Outlet ◽  
On Line ◽  
Made In

The flow discharged from centrifugal impellers is highly distorted and its behavior in the diffuser could be expected to have a determining effect on the performance of the compressor. The present work sets out to investigate this. The experimental work reported in this paper was designed to investigate the interaction between the vaned diffuser and the impeller. Unsteady measurements of velocity and wall static pressure were made at numerous positions in a vaned diffuser using an on-line data logging system. Experiments were carried out at a range of flow coefficients for three diffusers with 10, 20, and 30 vanes set at each of three different radius ratios, 1.04, 1.1, and 1.2. A limited number of experiments were also carried out with restaggered diffuser vanes and as a reference case extensive measurements were made in a vaneless diffuser build. The impeller, which was designed for a pressure ratio of 4.6, was run at low speed (3000 rpm) after modification to make its overall diffusion equivalent to that at the high speed for which it was designed. The circumferential distortion from the impeller was attenuated very rapidly in the entrance region of the diffuser vanes and suprisingly had only minor effects on the flow inside the vaned diffuser passage. The effect of the diffuser vanes on the flow discharged from the impeller was evident and reversal of flow back into the impeller was detected when the diffuser vanes were close to the impeller and the flow rate was not very high. The time-mean total and static pressure at impeller outlet were found to vary over the pitch of a diffuser vane, and a variation in the strength of the impeller wake was also observed.

The Effect of the Operating Point on the Pressure Fluctuations at the Blade Passage Frequency in the Volute of a Centrifugal Pump

2002 ◽  
Vol 124 (3) ◽  
pp. 784-790 ◽  
Author(s):  
Jorge L. Parrondo-Gayo ◽  
Jose´ Gonza´lez-Pe´rez ◽  
Joaquı´n Ferna´ndez-Francos
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Fast Response ◽  
Strong Increase ◽  
Flow Rates ◽  
Blade Passage ◽  
Pressure Transducers ◽  
Leading Role ◽  
Dynamic Forces ◽  
Response Pressure

An experimental investigation is presented which analyzes the unsteady pressure distribution existing in the volute of a conventional centrifugal pump with a nondimensional specific speed of 0.48, for flow-rates from 0% to 160% of the best-efficiency point. For that purpose, pressure signals were obtained at 36 different locations along the volute casing by means of fast-response pressure transducers. Particular attention was paid to the pressure fluctuations at the blade passage frequency, regarding both amplitude and phase delay relative to the motion of the blades. Also, the experimental data obtained was used to adjust the parameters of a simple acoustic model for the volute of the pump. The results clearly show the leading role played by the tongue in the impeller-volute interaction and the strong increase in the magnitude of dynamic forces and dipole-like sound generation in off-design conditions.

Analysis of pulsating flow measurement of engine exhaust by a Pitot tube flowmeter

2005 ◽  
Vol 6 (1) ◽  
pp. 85-93 ◽  
Author(s):  
H Nakamura ◽  
I Asano ◽  
M Adachi ◽  
J Senda
Keyword(s):  
Fast Response ◽  
Differential Pressure ◽  
Pulsating Flow ◽  
Pitot Tube ◽  
Engine Exhaust ◽  
Idle Speed ◽  
Pressure Transducers ◽  
Vehicle Engine ◽  
Before And After ◽  
Response Pressure

The Pitot tube flowmetering technique has been used to measure pulsating flow from a vehicle engine exhaust. In general, flowmetering techniques that utilize differential pressure measurements based on Bernoulli's theory are likely to show erroneous readings when measuring an average flowrate of pulsating flow. The primary reason for this is the non-linear relationship between the differential pressure and the flowrate; i.e. the flowrate is proportional to the square root of the differential pressure. Therefore, an average of the differential pressure does not give an average of pulsating flow. In this study, fast response pressure transducers have been used to measure the pulsating pressure. Then the pulsating differential pressure is converted to the flowrate while keeping the pulsation unaveraged. An average flowrate is then calculated in the flowrate domain in order to maintain linearity before and after averaging. The peak amplitude of a pulsation measured here was about 1800 L/min at an average flowrate of 70 L/min when the engine ran at idle speed. This measurement has been confirmed by measuring the pulsation with a gas analyser. The results show a large amount of back and forth gas movement in the exhaust tube. This magnitude of pulsation can cause as much as five times higher erroneous results with the pressure domain averaging when compared to a flowrate domain averaging.

The Effect of Vane Clocking on the Unsteady Flowfield in a One and a Half Stage Transonic Turbine

2007 ◽  
Author(s):  
O. Schennach ◽  
R. Pecnik ◽  
B. Paradiso ◽  
E. Go¨ttlich ◽  
A. Marn ◽  
...  
Keyword(s):  
Laser Doppler Velocimetry ◽  
Three Dimensional ◽  
Fast Response ◽  
Navier Stokes ◽  
Doppler Velocimetry ◽  
Pressure Transducers ◽  
Wake Interactions ◽  
Transonic Turbine ◽  
Response Pressure ◽  
Vane Clocking

The current paper presents the results of numerical and experimental clocking investigations performed in a high-pressure transonic turbine with a downstream vane row. The objective was a detailed analysis of shock and wake interactions in such a 1.5 stage machine while clocking the vanes. Therefore a transient 3D-Navier Stokes calculation was done for two clocking positions and the three dimensional results are compared with Laser-Doppler-Velocimetry measurements at midspan. Additionally the second vane was equipped with fast response pressure transducers to record the instantaneous surface pressure for 20 different clocking positions at midspan.

A Novel Approach to Surge Control: High-Frequency Pressure Variance As an Indicator of Impending Surge in Centrifugal Compressors

2018 ◽  
Author(s):  
Meera Day Towler ◽  
Tim Allison ◽  
Paul Krueger ◽  
Karl Wygant
Keyword(s):  
High Speed ◽  
Fast Response ◽  
Time Signal ◽  
Multiple Time ◽  
Pressure Data ◽  
Pressure Transducers ◽  
Surge Margin ◽  
Novel Approach ◽  
Surge Control ◽  
Response Pressure

This investigation studies fast-response pressure measurements as an indicator of the onset of surge in a single-stage centrifugal compressor. The objective is to determine an online monitoring approach for surge control that does not rely on surge margin relative to maps from predictions or factory testing. Fast-response pressure transducers are installed in the suction piping, inducer, diffuser, and discharge piping. A speed line is mapped, and high-speed pressure data are collected across the compressor map. The compressor is driven into surge several times to collect pressure data between during surge and between surge events. Following testing, these data are post-processed via filtration and statistical analyses. It is determined that, when taken together, the mean and range of the standard deviation of the time signal for multiple time steps can be used to determine whether the compressor’s operating point is approaching surge for the conditions tested.

On the Use of Fast-Response Pressure Transducers in a Common-Rail Diesel Injection System

2006 ◽  
Author(s):  
R. Amirante ◽  
L. A. Catalano ◽  
A. Dadone ◽  
V. Lombardo
Keyword(s):  
Pressure Transducer ◽  
Single Injection ◽  
Electric Circuit ◽  
Fast Response ◽  
Common Rail ◽  
Injection System ◽  
Pressure Transducers ◽  
Multiple Injections ◽  
Diesel Injection ◽  
Response Pressure

The aim of this paper is to investigate the use of fast-response pressure transducers for measuring the instantaneous pressure in different sections of a common-rail diesel injection system, both for a single injection and for multiple injections. The influence of the pressure transducer onto the measured pressure is evaluated numerically by comparing the pressure history computed without the pressure transducer and that computed with the presence, and thus with the disturbance, of this sensor. A new electric circuit is proposed in substitution of the standard electronic central unit, which allows to modify the injection parameters and to perform injections on a test rig, as done in the automotive applications. Experimental results are provided both for a single injection and for multiple injections, to demonstrate the capabilities of the proposed test bench for the unijet injectors.

Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor

2019 ◽  
Author(s):  
Sasuga Ito ◽  
Masato Furukawa ◽  
Satoshi Gunjishima ◽  
Hiroki Usuki ◽  
Takafumi Ota ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
High Response ◽  
Low Flow ◽  
Pipeline System ◽  
Flow Phenomenon ◽  
Pressure Transducers ◽  
Transonic Centrifugal Compressor ◽  
Response Pressure

Abstract Surge is an unsteady flow phenomenon occurring at low flow rates in the pipeline system including compressors. The surge is a phenomenon that must be avoided because of the danger in the operation: the pipeline equipment can be damaged or the operation cannot be continued. Experimental work is required not only to understand the unsteady behavior but to also validate the CFD used for more localized analysis and development of the understanding of the flow phenomena when operating near surge. Nevertheless, there are still many unclear points not only about the flow phenomenon at the inception of the surge which is important for the prediction of the surge but also about the surge behavior itself. Especially, as for the surge occurring in transonic centrifugal compressors, there are currently few experimental research cases due to the difficulty of the unsteady measurement. In this research, we measured the time variations in pressure and flow rate in a transonic centrifugal compressor for a vehicle turbocharger which consists of an impeller, vaneless diffuser and scroll. In the experiments, the measurement pipes were set upstream and downstream of the compressor and the velocity and the wall static pressure were measured with an I-type hot wire probe and high response pressure transducers, respectively. In addition, to investigate the process and the occurrence point of the back flow in surge, the wall static pressure was measured by means of high response pressure transducers which were mounted on the shroud upstream of the impeller and the diffuser hub at the two-circumferential positions, respectively. As the result of the experiments, the unsteady flow process during the mild and deep surges was measured and the inception of deep surge was clarified.

Investigation of the Wake Effect From the Centrifugal Splitter Impeller Blade to the Vaned Diffuser

2012 ◽  
Author(s):  
Xuechen Li ◽  
Guang Xi ◽  
Jiang Hua ◽  
Wuqi Gong
Keyword(s):  
Flow Characteristics ◽  
Suction Side ◽  
Wake Flow ◽  
Centrifugal Impeller ◽  
Wake Effect ◽  
Impeller Blade ◽  
Vaned Diffuser ◽  
Side Pressure ◽  
Unsteady Wake ◽  
Impeller Outlet

In this paper, the unsteady wake effect from an unshrouded centrifugal impeller with splitter blades was numerically and experimentally investigated. The numerical simulated detail flow characteristics of two stations, respectively placed at the impeller outlet and the diffuser inlet, were compared with the measured data. The “jet-wake” flow pattern was observed at the exit of the impeller. And the investigation showed that the wake effect of the splitter was weaker that of the main blade. But both the main blade and the splitter blade wake could affect the diffuser performance at a range of whole-chord length and they provoked the pressure side profile pressure fluctuating intensely from 10% chord to 50% chord, while the suction side pressure varying rapidly at the range from 60% chord to 80% chord.

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