Measurement of Performance Characteristics of a Piezoelectric Micro Blower

2013 ◽  
Author(s):  
Takashi Fukue ◽  
Koichi Hirose ◽  
Hirotoshi Terao
Keyword(s):  
Flow Rate ◽  
Measurement System ◽  
Performance Characteristic ◽  
Static Pressure ◽  
Characteristic Curve ◽  
Pressure Rise ◽  
Electronic Equipment ◽  
Cooling Performance ◽  
Cooling Air ◽  
The Relationship

This study conducts a measurement system of a performance of a piezoelectric micro blower. Electronic equipments such as laptop computers and cellular phones become smaller and thinner while their functions become more complex. As a result, a lot of components are mounted in an electronic enclosure and flow passages for the cooling air become narrow. This causes significant pressure drop and general cooling fans cannot supply enough cooling air. To improve cooling performance in small electronic equipment, a new air supply system which combines smaller and thinner size with a high pressure performance characteristic is needed. We focused on a novel piezoelectric micro blower. This blower can supply the airflow with high static pressure using the vibration of the piezoelectric element. This may produce a forced convection cooling with low electric power regardless of the size of electronic equipment and packaging density of electrical devices. However, to predict accurate cooling performance of the piezoelectric micro blower in thermal design, we have to obtain a correct supply flow rate of the blower because the cooling performance of forced convection is significantly dependent on the supply flow rate. Generally, an operating point of the blower, which is the operating pressure and the flow rate in electronic equipment, is the point of intersection of performance characteristic curve, which is the relationship between the blower’s pressure rise and the supply flow rate, and flow resistance curve in equipment. Therefore the measurement of the performance characteristic curve is most important. We tried to develop the measurement system of the performance characteristic curve of the piezoelectric micro blower with high accuracy. We succeeded to measure the relationship between the supply flow rate and the static pressure rise of the micro blower. Moreover, in order to clarify whether the micro blower is available for a cooling method of high-density packaging electronic equipment or not, we tried to investigate the effects of the obstruction, which is mounted in front of the blower, on the performance characteristic. Then, we confirmed whether the performance of the blower is changed by the components mounted near the blower or not.

Peak Flow Rate During Induced Cough: A Predictor of Successful Decannulation of a Tracheotomy Tube in Neurosurgical Patients

2010 ◽  
Vol 19 (3) ◽  
pp. 278-284 ◽  
Author(s):  
Linda Y. Y. Chan ◽  
Alice Y. M. Jones ◽  
Raymond C. K. Chung ◽  
K. N. Hung
Keyword(s):  
Flow Rate ◽  
Operating Characteristic ◽  
Peak Flow ◽  
Characteristic Curve ◽  
Peak Flow Rate ◽  
Tracheotomy Tube ◽  
Optimal Cutoff ◽  
Neurosurgical Patients ◽  
Optimal Cutoff Point ◽  
The Relationship

Background An accurate predictor of successful decannulation in neurosurgical patients that indicates the best time for tracheotomy decannulation would minimize the risks of continued cannulation and unsuccessful decannulation. Objective To determine whether the peak flow rate during induced cough is an appropriate predictor of successful decannulation. Methods A total of 32 neurosurgical patients with a tracheotomy were enrolled. The highest peak expiratory flow rate during 3 induced coughs, the total volume of tracheal secretions collected in 6 hours, and scores on the Glasgow Coma Scale were recorded. Logistic regression analysis was applied to determine the relationship between these variables and successful decannulation (reintubation not required within 72 hours). Results Decannulation was attempted in 23 of 32 patients. The remaining 9 patients were considered clinically inappropriate for the procedure. Of the 23 patients decannulated, 2 required reinsertion of the tracheotomy tube. Analysis revealed that peak flow rate during induced cough (odds ratio, 1.12; 95% confidence interval, 1.02–1.23) was independently associated with successful decannulation (accuracy, 75%; sensitivity, 85.7%; specificity, 54.5%). The receiver operating characteristic curve indicated an optimal cutoff point of 29 L/min. Conclusion Measurement of peak flow rate during induced cough is a simple and reproducible intervention that improves predictability of successful decannulation in patients with tracheotomy.

Dynamic Response of a Centrifugal Blower to Periodic Flow Fluctuations

1986 ◽  
Vol 108 (1) ◽  
pp. 77-82 ◽  
Author(s):  
A. N. Abdel-Hamid
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Pressure Rise ◽  
Rotation Frequency ◽  
Periodic Flow ◽  
Average Flow Rate ◽  
Centrifugal Blower ◽  
Inertia Effects ◽  
Average Flow ◽  
Discharge Flow Rate

Experimental investigation of the dynamic response of a centrifugal blower to periodic flow rate modulations was carried out at different blower operating conditions. For modulation frequencies in the range of 0.0085–0.085 of the shaft rotation frequency, the fluctuating pressures at inlet, discharge, and across a flow orifice were simultaneously measured and analyzed in the time and frequency domains. Measurements of the amplitude and phase of the transfer function between the blower static pressure rise and the discharge flow rate fluctuations indicated that the quasi-steady approximation should be limited to frequencies lower than 0.02 of the shaft rotation frequency. For the same average flow rate, the static pressure rise progressively lagged the discharge flow rate fluctuations as the frequency was increased. The trend was similar to that of the inertia effects of a fluctuating flow in a pipe. For the same frequency these inertia effects increased as the average flow rate through the blower was decreased. Applications of the results to on-line measurements of the slope of the characteristic curve and improved dynamic modeling of centrifugal compressors and blowers are discussed.

Measurement and Analysis of an Efficient Turbine Rotor Pump Work Reduction System Incorporating Pre-Swirl Nozzles and a Free Vortex Pressure Augmentation Chamber

2004 ◽  
Author(s):  
V. Laurello ◽  
M. Yuri ◽  
K. Fujii ◽  
K. Ishizaka ◽  
T. Nakamura ◽  
...  
Keyword(s):  
Relative Velocity ◽  
Static Pressure ◽  
Tangential Velocity ◽  
Pressure Rise ◽  
Turbine Rotor ◽  
Vortex Chamber ◽  
Free Vortex ◽  
Pressure Losses ◽  
Cooling Air ◽  
Velocity Pressure

Measurements and analysis of an efficient turbine rotor pump work reduction system is presented. The system features; a “low” radius pre-swirl nozzle comprised of cascade vanes with a radial orientation, equal radius seals downstream of the nozzle, “jumper” tubes across the nozzle, and a free vortex chamber. A scaled experimental rig was utilized to measure and compare with predictions the following; rotor pump work, average tangential velocity exiting the nozzle, tangential velocity variation in the axial and radial direction, free vortex chamber static pressure rise, effect of relative velocity pressure losses, and effect of “pollution” by seal flow. The effort focused on measuring pump work reduction and the efficiency of the pressure augmentation system. In contrast to aero-engines where the main objective of pre-swirl is to reduce cooling air temperature to the blades, the main objective for this industrial gas turbine is to reduce pump work and increase output. An external pre-cooler is utilized to achieve the large cooling air temperature reduction required to maintain disk material limits. The analytical results and rig test data are presented and compared. The results substantiated the following: the level of reduced rotor pump work due to pre-swirl, the static pressure rise in the free vortex chamber, the effect of eliminating “pollution”, and relative velocity pressure losses. CFD analytical results are compared with the rig data.

scholarly journals Design of High Efficiency Blowers for Future Aerosol Applications

2009 ◽  
Author(s):  
Raman Chadha ◽  
Gerald L. Morrison ◽  
Andrew R. McFarland
Keyword(s):  
Flow Rate ◽  
High Efficiency ◽  
Static Pressure ◽  
Pressure Rise ◽  
Electrical Energy ◽  
Design Flow ◽  
Preliminary Design ◽  
Aerosol Sampling ◽  
Wall Functions ◽  
Low Efficiency

High efficiency air blowers to meet future portable aerosol sampling applications were designed, fabricated, and their performance evaluated. A preliminary blower design based on specific speed was selected, modeled in CFD, and the flow field simulated. This preliminary blower size was scaled in planar and axial directions, at different rpm values, to set the Best Efficiency Point (BEP) at a flow rate of 100 L/min (1.67×10−3 m3/s @ room conditions) and a pressure rise of 1000 Pa (4″ WC). Characteristic curves for static pressure rise versus air flow rate through the impeller were generated. Experimentally measured motor/blower combination efficiency (ηEXP) for the preliminary design was around 10%. The low value was attributed to the low efficiency of the D.C. motor used (Chadha, 2005). CFD simulations using the κ–ε turbulent model and standard wall function (non-equilibrium wall functions) approach overpredicted the head values. Enhanced wall treatment under-predicted the head rise but provided better agreement with experimental results. The static pressure rise across the final blower is 1021 Pa at the design flow rate of 100 L/min. Efficiency value based on measured static pressure rise value and the electrical energy input to the motor (ηEXP) is 26.5%, a 160% improvement over the preliminary design.

Experimental Feasibility Study of Radial Injection Cooling of Three-Pad Air Foil Bearings

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Suman K. Shrestha ◽  
Daejong Kim ◽  
Young Cheol Kim
Keyword(s):  
Heat Exchange ◽  
Flow Rate ◽  
High Speed ◽  
Air Flow ◽  
Air Flow Rate ◽  
Design Factor ◽  
Cooling Performance ◽  
Radial Injection ◽  
Cooling Air Flow ◽  
Cooling Air

The foil bearing (FB) is one type of hydrodynamic bearing using air or another gas as a lubricant. When FBs are designed, installed, and operated properly, they are a very cost-effective and reliable solution for oil-free turbomachinery. Because there is no mechanical contact between the rotor and its bearings, quiet operation with very low friction is possible once the rotor lifts off the bearings. However, because of the high speed of operation, thermal management is a very important design factor to consider. The most widely accepted cooling method for FBs is axial flow cooling, which uses cooling air or gas passing through heat-exchange channels formed underneath the top foil. The advantage of axial cooling is that no hardware modification is necessary to implement it, because the elastic foundation structures of the FB serve as the heat-exchange channels. Its disadvantage is that an axial temperature gradient exists on the journal shaft and bearing. In this paper, the cooling characteristics of axial cooling are compared with those of multipoint radial injection, which uses high-speed injection of cooling air onto the shaft at multiple locations. Experiments were performed on a three-pad FB 49 mm in diameter and 37.5 mm in length, at speeds of 30,000 rpm and 40,000 rpm. Injection speeds were chosen to be higher than the journal surface speed, but the total cooling air flow rate was matched to that of the axial cooling cases. Experimental results show that radial injection cooling is comparable to axial cooling at 30,000 rpm, in terms of cooling performance. Tests at 40,000 rpm reveal that the axial cooling performance reaches saturation when the pressure drop across the bearing is larger than 1000 Pa, while the cooling performance of radial injection is proportional to the cooling air flow rate and does not become saturated. Overall, multipoint radial injection is better than axial cooling at high rotor speeds.

Blade Surface Pressure Measurements on a Low Pressure Rise Axial Flow Fan

2020 ◽  
Author(s):  
Johannes Rohwer ◽  
Sybrand J. van der Spuy ◽  
Theodor W. von Backström ◽  
Francois G. Louw
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Surface Pressure ◽  
Static Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Test Facility ◽  
Pressure Measurements ◽  
Blade Surface ◽  
Axial Flow Fan

Abstract Fan performance characteristic tests of axial flow fans provide information on the global flow field, based on stable inlet flow field distribution. More information is often required on the local flow distribution existing in the vicinity of the fan blades under installed conditions. A 1.542 m diameter scale model of an axial flow fan, termed the M-Fan is tested in an ISO 5801, type A, test facility. The M-fan was specifically designed for low-pressure, high flow rate application in air-cooled or hybrid condensers. The scaled version of the M-fan was designed to have a fan static pressure rise of 116.7 Pa at a flow rate of 14.2 m3/s. Two specially constructed M-Fan blades are manufactured to conduct blade surface pressure measurements on the blades. The fan blades are equipped with 2 mm diameter tubes that run down the length of the fan blades in order to convey the measured pressure. Piezo-resistive pressure transducers, located on the hub of the fan, measure the static pressure distribution on the blades and the data is transferred to a stationary computer using a wireless telemetry setup. The blade pressure measurement setup is re-commissioned from a previous research project and its performance is qualified by testing and comparing to experimental results obtained on the B2a-fan. Excellent correlation to previous results is obtained. The experimental M-fan results are compared against results from a periodic numerical CFD model of a fan blade modelled in an ISO 5801, Type A test facility configuration. The experimental tests and numerical model correlate well with each other. The experimental blade surface pressure measurements have a minimum Pearson correlation to the numerically determined values of 0.932 (maximum 0.971).

Unsteady Aerodynamic Performance of a Centrifugal Compressor With Oscillating Downstream Static Pressure

2005 ◽  
Author(s):  
H. J. Eum ◽  
S. H. Kang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Method Of Characteristics ◽  
Static Pressure ◽  
Pressure Rise ◽  
Acoustic Resonance ◽  
Specific Frequency ◽  
D Model

In many applications, centrifugal compressors experience various kinds of downstream pressure disturbances which can lead to unstable operation even at the design operating condition. In this paper, 3-D numerical simulations have been carried out to understand the dynamic behaviors of the centrifugal compressor for the pulsation of downstream pressure disturbances and 1-D model using the method of characteristics has been developed to predict the behaviors more effectively. Static pressure disturbances with a frequency range from 25Hz to 1300 Hz and constant amplitude have been introduced at the diffuser exit. Static pressure rise and mass flow rate deviated from the quasi-steady characteristic as the frequency increased. The fluctuation of mass flow rate at the diffuser exit was amplified or attenuated depending on the disturbance frequency. The fluctuation was severely amplified at a specific frequency which seemed to be an acoustic resonance of the present compressor model including an inlet duct, a blade passage and a diffuser. The result of 1-D model showed good agreements with that of 3-D numerical simulation.

The Effect of Hub Configuration on the Performance of an Air-Cooled Steam Condenser Fan

2020 ◽  
Author(s):  
Z. Meiring ◽  
S. J. van der Spuy ◽  
C. J. Meyer
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Volumetric Flow Rate ◽  
Superior Performance ◽  
Design Point ◽  
Static Efficiency ◽  
Air Cooled Condensers ◽  
The Impact

Abstract Axial flow fans used in air-cooled condensers are typically analysed with smooth rounded hubs as they offer superior performance when compared to other hub configurations. However, such a hub configuration is impractical and may increase the manufacturing and installation costs of air-cooled condensers. As such, it is desirable to use a simpler, yet effective, hub configuration in order to reduce the installation cost. This paper assesses the impact that a simpler hub configuration may have on the performance of an axial flow fan. This is done through a comparison of three hub configurations: a cylindrical hub with a flat nose, a cylindrical hub with a hemispherical nose, and a disk hub, installed on the B2a-fan. Computational fluid dynamics modelling, utilising OpenFOAM, is used to simulate each hub configuration. It is found that the impact on performance due to hub configuration is dependent on the volumetric flow rate through the fan. A thin disk hub exhibits superior performance at low flow rates, resulting in a 8.4% improvement in total-to-static pressure rise and a 5.7% point improvement in total-to-static efficiency. As volumetric flow rate increases, the effectiveness of the disk hub configuration reduces while the hemispherical and flat nosed cylindrical hub configurations result in similar performance metrics at the design point flow rate. At above design point flow rate, the flat nosed cylindrical hub configuration shows an improvement in performance over the hemispherical nose cylindrical hub configuration, with a 9.5% increase in total-to-static pressure rise and a 5.1% point improvement in total-to-static efficiency.

Study on P-Q Curves of Cooling Fans for Thermal Design of Electronic Equipment (Effects of Opening Position of Obstructions Near a Fan)

2011 ◽  
Author(s):  
Takashi Fukue ◽  
Masaru Ishizuka ◽  
Tomoyuki Hatakeyama ◽  
Shinji Nakagawa ◽  
Katsuhiro Koizumi
Keyword(s):  
Flow Rate ◽  
Perforated Plate ◽  
Pressure Rise ◽  
High Density ◽  
Thermal Design ◽  
Electronic Equipment ◽  
Flow Passage ◽  
Fan Performance ◽  
Cooling Fan ◽  
Cooling Fans

This study describes an operation pressure and supplies flow rate of an axial cooling fan installed in high-density packaging electronic equipment. Fan performance is generally defined by their P-Q curve, specifically, a relationship between fan pressure rise (ΔP) and flow rate (Q). A compact cooling fan often operates in a high-density mounting device, which may decrease the fan performance. In this study, we focus on an obstruction near a fan, which is electronic components such as PCBs, capacitors and heat sinks, as one of a factor which decreases fan performance. We installed a perforated plate which simulated the above components near a fan and measured the P-Q curve. To investigate a relationship between a fan performance decrease and an opening position near the fan, a part of the perforated plate was closed. Closed position was changed and explored an opening condition which caused the dominant fan performance decrease. From experiments, it was found that the fan performance was decreased when flow passage in front of a fan was blocked by an obstruction. Especially, when flow passage in front of a fan hub was blocked, a dominantly reduction of fan pressure was caused. An obstruction rear a fan has no effect on a fan performance curve itself. In addition, opening conditions in front of a fan tip had a little influence on a fan pressure characteristic when there was no obstruction in front of a hub.

CFD - Based Investigation of Effects of Obstruction in Front of Small Axial Cooling Fan and Deterioration of Supply Flow Rate

2021 ◽  
Author(s):  
Tetsushi Fukuda ◽  
Yukio Masuda ◽  
Takashi Fukue ◽  
Yasuhiro Sugimoto ◽  
Tomoyuki Hatakeyama ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Pressure Rise ◽  
Leading Edge ◽  
Rotating Stall ◽  
High Density ◽  
Electronic Equipment ◽  
Fan Performance ◽  
Cooling Fan ◽  
High Density Packaging

Abstract This study describes the deterioration of a small axial fan’s supply flow rate in high-density packaging electronic equipment. A cooling fan flow rate can be predicted by its P-Q curve, which shows a relationship between a pressure rise at a fan (ΔP) and a supply flow rate (Q). However, in high-density packaging electronic equipment, the fan performance is affected by the mounting components around the fans, and the accurate prediction of the supply flow rate becomes difficult. This paper tried to do flow visualization around a small axial cooling fan’s impellers when the obstruction was mounted in front of the fan through CFD analysis. A relationship between the supply flow rate by the fan and the flow pattern around the impellers was investigated while changing the distance between the test fan and the obstruction. Through this study, the following results can be obtained. The fan’s flow is stable in the rotating stall region and the higher flow rate operating points regardless of whether or without the obstruction. At the lower flow rate conditions, the formation of a complex unsteady flow is reproduced. As the flow rate decreases, the flow’s separation point becomes closer to the leading edge of the impeller. In the case of obstruction, the change of the flow pattern causes a larger attack angle. As a result, fan performance is degraded.

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