Experimental Study on the Performance and Pressure Fluctuations of a Regenerative Gas Blower for Different Design Parameters

2011 ◽  
Author(s):  
Younghoon Kim ◽  
Shin Hyoung Kang ◽  
Yonggyu Noh
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Fast Response ◽  
Fuel Cell Vehicle ◽  
Maximum Efficiency ◽  
Design Parameters ◽  
Pressure Transducers ◽  
Total Enthalpy ◽  
Aspect Ratios ◽  
Blade Thickness

A regenerative gas blower design for fuel cell vehicle is presented. Two issues studied concern non-dimensional performance characteristics under various design parameters and the noise of the blower due to unsteady pressure fluctuation. Non-dimensional performance curves were measured at various rotating speeds and gas mixture ratios. Blower models using different design parameters such as the stripper angle, blade aspect ratios and blade thickness ratios were tested. The effects that aforementioned parameters had on performance were investigated. Surface pressure fluctuations were measured in the channel close to both ends of the stripper using fast-response pressure transducers. A sharp blade increases the maximum isentropic total enthalpy coefficient and the maximum efficiency because the pressure loss coefficient of the circulatory flow is reduced. A small stripper angle enhanced the maximum isentropic total enthalpy coefficient and the maximum efficiency because working sections was lengthened. The enlarged stripper angle and the low pressure difference across the stripper reduce the magnitude of pressure fluctuation at the blade passing frequency.

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.

Horizontal Pressure Fluctuation in Bubbling Fluidized Bed

2003 ◽  
Author(s):  
Vesa V. Walle´n
Keyword(s):  
Pressure Gradient ◽  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Middle Part ◽  
Biomass Combustion ◽  
Bottom Part ◽  
Pressure Transducers ◽  
Bubbling Fluidized Bed ◽  
Horizontal Pressure

Pressure measurements were conducted in a two-dimensional hot atmospheric bubbling fluidized bed reactor in the laboratory of Energy and Process Engineering at Tampere University of Technology. A set of six fast pressure transducers was used to detect the rapid pressure fluctuations inside the bubbling bed of the reactor. These pressure transducers were placed both vertically and horizontally into the reactor. From these measurements it was found that the vertical pressure fluctuation took place at the same time at different levels of the bed. Also the same fluctuation could be seen under the air distributor. The horizontal pressure fluctuation was found to vary both by place and time. At the bottom part of the bed the highest pressure peaks was found at centre of the bed. Most of the time there was a pressure gradient the highest pressure being in the centre of the bed. This gradient creates horizontal flow of gases from middle to the sides. The velocity of this flow varies with the size of the pressure gradient. The opposite effect can be found in the upper part of the bed. The highest pressure was no more in the middle part of the bed. Instead, it was found to be between the centre of the bed and left and right walls. The pressure was low at the walls but also rather low at the middle of the bed. There must be flow towards the walls and to the centre axis. These pressure fluctuations can provide an explanation for the well-known “wandering plume” effect. They can also give a tool to better describe the mixing inside a bubbling fluidized bed. This kind of tool is needed when biomass combustion is modelled in bubbling fluidized bed.

Wake, Shock, and Potential Field Interactions in a 1.5 Stage Turbine—Part II: Vane-Vane Interaction and Discussion of Results

2003 ◽  
Vol 125 (1) ◽  
pp. 40-47 ◽  
Author(s):  
R. J. Miller ◽  
R. W. Moss ◽  
R. W. Ainsworth ◽  
N. W. Harvey
Keyword(s):  
High Pressure ◽  
Potential Field ◽  
Pressure Fluctuations ◽  
Interaction Mechanism ◽  
Fast Response ◽  
Rotor Blades ◽  
Suction Surface ◽  
Time Resolved ◽  
Pressure Transducers ◽  
The Individual

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flow field in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. In the first half of this paper it is shown that, in addition to the two main interaction mechanisms (upstream vane-rotor and rotor-downstream vane interactions, presented in Part I of this paper) a third interaction occurs. This new interaction mechanism is shown to be caused by the interaction between the downstream vane’s potential field and the upstream vane’s trailing edge potential field and shock. The unsteady rotor surface static pressure fluctuations caused by this interaction are shown to occur on the late rotor suction surface at a frequency corresponding to the difference in the numbers of upstream and downstream vanes. The second part to the paper discusses the mechanisms that cause vane-rotor-vane interaction. The rotor’s operating point is periodically altered as it passes the downstream vane. It is shown that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.

scholarly journals The Effect of Aspect Ratio on Compressor Performance

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Ho-On To ◽  
Robert J. Miller
Keyword(s):  
Aspect Ratio ◽  
Flow Field ◽  
Pressure Rise ◽  
Rate Of Change ◽  
Maximum Efficiency ◽  
Order Model ◽  
Aspect Ratios ◽  
Blade Thickness ◽  
Compressor Performance ◽  
Low Order

Abstract The optimum aspect ratio at which maximum efficiency occurs is relatively low, typically between 1 and 1.5. At these aspect ratios, inaccuracies inherently exist in the decomposition of the flow field into freestream and endwall components due to the absence of a discernible freestream. In this paper, a unique approach is taken: a “linear repeating stage” concept is used in conjunction with a novel way of defining the freestream flow. Through this approach, physically accurate decomposition of the flow field for aspect ratios as low as ∼0.5 can be achieved. This ability to accurately decompose the flow leads to several key findings. First, the endwall flow is found to be dependent on static pressure rise coefficient and endwall geometry, but independent of the aspect ratio. Second, the commonly accepted relationship that endwall loss coefficient varies inversely with the aspect ratio is shown to be physically inaccurate. Instead, a new term, which the authors refer to as the “effective aspect ratio,” should replace the term “aspect ratio.” Moreover, not doing so can result in efficiency errors of ∼0.6% at low aspect ratios. Finally, there exists a low aspect ratio limit below which the two endwall flows interact causing a large separation to occur along the span. From these findings, a low-order model is developed to model the effect of varying aspect ratio on compressor performance. The last section of the paper uses this low-order model and a simple analytical model to show that to a first order, the optimum aspect ratio is just a function of the loss generated by the endwalls at zero clearance and the rate of change in profile loss due to blade thickness. This means that once the endwall configuration has been selected, i.e., cantilever or shroud, the blade thickness sets the optimum aspect ratio.

Wake, Shock and Potential Field Interactions in a 1.5 Stage Turbine: Part II — Vane-Vane Interaction and Discussion of Results

2002 ◽  
Author(s):  
R. J. Miller ◽  
R. W. Moss ◽  
R. W. Ainsworth ◽  
N. W. Harvey
Keyword(s):  
High Pressure ◽  
Potential Field ◽  
Pressure Fluctuations ◽  
Interaction Mechanism ◽  
Fast Response ◽  
Rotor Blades ◽  
Suction Surface ◽  
Time Resolved ◽  
Pressure Transducers ◽  
The Individual

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighbouring blade rows is investigated with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flowfield in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. In the first half of this paper it is shown that, in addition to the two main interaction mechanisms (upstream vane-rotor and rotor-downstream vane interactions, presented in Miller et al. [1]) a third interaction occurs. This new interaction mechanism is shown to be caused by the interaction between the downstream vane’s potential field and the upstream vane’s trailing edge potential field and shock. The unsteady rotor surface static pressure fluctuations caused by this interaction are shown to occur on the late rotor suction surface at a frequency corresponding to the difference in the numbers of upstream and downstream vanes. The second part to the paper discusses the mechanisms that cause vane-rotor-vane interaction. The rotor’s operating point is periodically altered as it passes the downstream vane. It is shown that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.

Influence of Pump-Circuit Coupling on Acoustic Waves in Pipelines and Pump Velocity Fields

2013 ◽  
Author(s):  
Jens Keller ◽  
Jorge Parrondo ◽  
Eduardo Blanco ◽  
Raúl Barrio ◽  
Carlos Suárez
Keyword(s):  
Acoustic Impedance ◽  
Acoustic Waves ◽  
Rotation Axis ◽  
Pressure Fluctuations ◽  
Acoustic Emissions ◽  
Fast Response ◽  
Velocity Fields ◽  
Matrix Analysis ◽  
Centrifugal Pumps ◽  
Pressure Transducers

Hydraulic piping systems are sensitive to excessive acoustic emissions which can give rise to vibrations or to failure of mechanical elements due to fatigue. Common excitation sources are centrifugal pumps due to the periodic interaction of the impeller with the volute tongue. They radiate pressure fluctuations into the connected circuit at the blade-passing frequency which are reflected in the circuit. The aim of the present investigation was the experimental characterization of the perturbations induced in a piping network as a function of the acoustic impedance of the circuit using fast-response pressure transducers. Three transducers were placed along the discharge pipe to decompose the pressure signal into the radiated and reflected acoustic wave, with amplitude and phase. The speed of sound in the water pipelines was determined experimentally. Results of impedance at the pump tongue were compared with a theoretical approach, using a Transfer Matrix Analysis, where each pipe element is represented by a 2×2-matrix, relating the acoustic pressure and velocity fluctuations at the two ports. Attenuation was considered by using complex wavenumbers. The acoustic impedance was changed by using different rotation speeds and by using a cavity which works as a harmonic oscillator whose resonance frequency can be changed. The results presented for different operating points show the influence of changing impedance on the pressure perturbations due to pump-circuit acoustic coupling. The pump was built with a transparent impeller and volute to conduct Particle Image Velocimetry (PIV) measurements in a plane perpendicular to the pump rotation axis. Phase-averaged velocity fields were obtained at different blade positions in the zone around the tongue. Vorticity fields were derived from it and turbulence is shown by representing in-plane turbulent kinetic energy (TKE). Strong vorticity and turbulence occurred in the volute channel behind the blade and near the tongue tip.

Effect of Clocking on the Second Stator Pressure Field of a One and a Half Stage Transonic Turbine

2004 ◽  
Author(s):  
J. Gadea ◽  
R. De´nos ◽  
G. Paniagua ◽  
N. Billiard ◽  
C. H. Sieverding
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Fast Response ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Static Pressure Distribution ◽  
Transonic Turbine

This paper focuses on the experimental investigation of the time-averaged and time-resolved pressure field of a second stator tested in a one and a half stage high-pressure transonic turbine. The effect of clocking and its influence on the aerodynamic and mechanical behaviour are investigated. The test program includes four different clocking positions, i.e. relative pitch-wise positions between the first and the second stator. Pneumatic probes located upstream and downstream of the second stator provide the time-averaged component of the pressure field. For the second stator airfoil, both time-averaged and time-resolved surface static pressure fields are measured at 15, 50 and 85% span with fast response pressure transducers. Regarding the time-averaged results, the effect of clocking is mostly observed in the leading edge region of the second stator, the largest effects being observed at 15% span. The surface static pressure distribution is changed locally, which is likely to affect the overall performance of the airfoil. The phase-locked averaging technique allows to process the time-resolved component of the data. The pressure fluctuations are attributed to the passage of pressure gradients linked to the traversing of the upstream rotor. The pattern of these fluctuations changes noticeably as a function of clocking. Finally, the time-resolved pressure distribution is integrated along the second stator surface to determine the unsteady forces applied on the vane. The magnitude of the unsteady force is very dependent on the clocking position.

Influence of T-shape tip clearance on performance of a mixed-flow pump

2017 ◽  
Vol 232 (4) ◽  
pp. 386-396 ◽  
Author(s):  
Tan Lei ◽  
Xie Zhifeng ◽  
Liu Yabin ◽  
Hao Yue ◽  
Xu Yun
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Rotation Frequency ◽  
Tip Clearance ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Movement Trajectories ◽  
Blade Thickness ◽  
Flow Pump

Influence of original and T-shape blade end on performance of a mixed-flow pump is investigated by using experimental measurement and numerical simulation. The new proposed T-shape blade end is formed at 95%–100% blade height with a linear increase of blade thickness. In comparison with original blade end, the efficiency of pump with T-shape blade end increases by 1.86%, and the leakage flow decreases by 15.95%. Space streamlines across the blade tip clearance can be divided into three beams with different movement trajectories, and the swirl motions of streamlines directly correspond to the swirling strength. The highest amplitude of pressure fluctuation appears at the blade leading edge along the tip clearance. In comparison with original blade end, the highest amplitude of pressure fluctuation for T-shape blade end decreases by 27.45%. The dominant frequencies of the pressure fluctuations in tip clearance region for original blade end and T-shape blade end are both five times of the axis rotation frequency, corresponding to the impeller blade number of five.

scholarly journals Design, Analysis, and Experiment on a Novel Stick-Slip Piezoelectric Actuator with a Lever Mechanism

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 863 ◽  
Author(s):  
Weiqing Huang ◽  
Mengxin Sun
Keyword(s):  
Piezoelectric Actuator ◽  
Simple Structure ◽  
Fast Response ◽  
Displacement Sensor ◽  
Design Parameters ◽  
The Finite Element Method ◽  
Stick Slip ◽  
Lever Mechanism ◽  
Series Of Experiments ◽  
Stator Design

A piezoelectric actuator using a lever mechanism is designed, fabricated, and tested with the aim of accomplishing long-travel precision linear driving based on the stick-slip principle. The proposed actuator mainly consists of a stator, an adjustment mechanism, a preload mechanism, a base, and a linear guide. The stator design, comprising a piezoelectric stack and a lever mechanism with a long hinge used to increase the displacement of the driving foot, is described. A simplified model of the stator is created. Its design parameters are determined by an analytical model and confirmed using the finite element method. In a series of experiments, a laser displacement sensor is employed to measure the displacement responses of the actuator under the application of different driving signals. The experiment results demonstrate that the velocity of the actuator rises from 0.05 mm/s to 1.8 mm/s with the frequency increasing from 30 Hz to 150 Hz and the voltage increasing from 30 V to 150 V. It is shown that the minimum step distance of the actuator is 0.875 μm. The proposed actuator features large stroke, a simple structure, fast response, and high resolution.

scholarly journals Investigation into the Relationship between Super-Knock and Misfires in an SI GDI Engine

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2099
Author(s):  
Jian Gao ◽  
Anren Yao ◽  
Yeyi Zhang ◽  
Guofan Qu ◽  
Chunde Yao ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Direct Injection ◽  
Exhaust Valve ◽  
Gasoline Direct Injection ◽  
Exhaust Pipe ◽  
Pressure Transducers ◽  
Spark Plug ◽  
Si Engines ◽  
Gdi Engine ◽  
The Relationship

The super-knock poses new challenges for further increasing the power density of spark ignition (SI) engines. The critical factors and mechanism connecting regarding the occurrence of super-knock are still unclear. Misfire is a common phenomenon in SI engines that the mixture in cylinder is not ignited normally, which is often caused by spark plug failure. However, the effect of misfire on engine combustion has not been paid enough attention to, particularly regarding connection to super-knock. The paper presents the results of experimental investigation into the relationship between super-knock and misfires at low speed and full load conditions. In this work, a boosted gasoline direct injection (GDI) engine with an exhaust manifold integrated in the cylinder head was employed. Four piezoelectric pressure transducers were used to acquire the data of a pressure trace in cylinder. The spark plugs of four cylinders were controlled manually, of which the ignition system could be cut off as demanded. In particular, a piezoelectric pressure transducer was installed at the exhaust pipe before the turbocharger to capture the pressure traces in the exhaust pipe. The results illustrated that misfires in one cylinder would cause super-knock in the other cylinders as well as the cylinder of itself. After one cylinder misfired, the unburned mixture would burn in the exhaust pipe to produce oscillating waves. The abnormal pressure fluctuation in the exhaust pipe was strongly correlated with the occurrence of super-knock. The sharper the pressure fluctuation, the greater the intensity of knock in the power cylinder. The cylinder whose exhaust valve overlapped with the exhaust valve of the misfired cylinder was prone to super-knock.

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