scholarly journals A mm-Scale Aeroelastic Oscillation-Based Anemometer

2012 ◽  
Author(s):  
Ian McKay
Keyword(s):  
Oscillation Frequency ◽  
Flow Measurement ◽  
Bluff Body ◽  
Low Cost ◽  
Fluid Velocity ◽  
Plastic Strip ◽  
Aeroelastic Flutter ◽  
Air Speed ◽  
Thin Plastic ◽  
Onset Velocity

By combining the aeroelastic and vortex-forced flutter modes of a thin plastic strip, its oscillation frequency can be confined to scale monotonically with fluid velocity. This principle has been used to produce a low-cost, mm-scale anemometer that measures air speed to ±(5% + 0.5m/s) from 1–18m/s. The device uses a 2mm slot-type photointerrupt detector to monitor the fundamental frequency of a 7μm thick Kapton strip suspended parallel to air flow. This paper describes the prototype and three of the experiments that informed its design. These investigated the effect of a bluff body on flutter onset velocity, the effect of filament geometry on bending position, and the effect of the superposition of the vortex-forced and aeroelastic flutter modes on discretely-measured flutter frequency. The experiments demonstrate that a trapezoidal filament in the wake of a similarly-sized bluff body is well-suited for this novel flow measurement strategy.

scholarly journals Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

2021 ◽  
Author(s):  
Fabian Burmann ◽  
Jerome Noir ◽  
Stefan Beetschen ◽  
Andrew Jackson
Keyword(s):  
Acoustic Waves ◽  
Flow Measurement ◽  
Low Cost ◽  
Time Of Flight ◽  
Zonal Flow ◽  
Gravitational Acceleration ◽  
Complex Flow ◽  
Ultrasonic Time ◽  
Theoretical Predictions ◽  
Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

scholarly journals Fuzzy uncertainty analysis and reliability assessment of aeroelastic aircraft wings

2020 ◽  
Vol 124 (1275) ◽  
pp. 786-811
Author(s):  
M. Rezaei ◽  
S.A. Fazelzadeh ◽  
A. Mazidi ◽  
M.I. Friswell ◽  
H.H. Khodaparast
Keyword(s):  
Structural Parameters ◽  
Low Cost ◽  
Fuzzy Variable ◽  
Fuzzy Uncertainty ◽  
Aircraft Wings ◽  
Wing Flutter ◽  
Flutter Speed ◽  
Wing Model ◽  
Safe Region ◽  
Air Speed

ABSTRACTIn the present study, fuzzy uncertainty and reliability analysis of aeroelastic aircraft wings are investigated. The uncertain air speed and structural parameters are represented by fuzzy triangular membership functions. These uncertainties are propagated through the wing model using a fuzzy interval approach, and the uncertain flutter speed is obtained as a fuzzy variable. Further, the reliability of the wing flutter is based on the interference area in the pyramid shape defined by the fuzzy flutter speed and air speed. The ratio between the safe region volume and the total volume of the pyramid gives the reliability value. Two different examples are considered—a typical wing section, and a clean wing—and the results are given for various wind speed conditions. The results show that the approach considered is a low-cost but suitable method to estimate the reliability of the wing flutter speed in the presence of uncertainties.

Study on Velocity Measurement of Gas/Solid Flow Based on Electrostatic Sensor

2014 ◽  
Vol 614 ◽  
pp. 275-278
Author(s):  
Yu Tang ◽  
Xiang Deng ◽  
Shuo Tian
Keyword(s):  
Measurement System ◽  
Velocity Measurement ◽  
Flow Measurement ◽  
Cross Correlation ◽  
Low Cost ◽  
High Sensitivity ◽  
Two Phase ◽  
Solid Flow ◽  
Correlation Algorithm ◽  
Electrostatic Induction

Electrostatic sensor is based on the principle of electrostatic induction. It is widely used for gas/solid two-phase flow measurement because it has the advantages of simple structure, high sensitivity, low cost, etc. In this paper, a velocity measurement system of gas/solid flow based on electrostatic sensor and cross-correlation algorithm is discussed. Electrostatic sensor with circular electrode is adopted. By COMSOL optimum simulation, the axial length of the electrode is designed. The signal conditioning circuits are discussed and cross-correlation algorithm is analyzed. The initial experimental results demonstrate that the velocity measurement system of gas/solid flow designed in this paper is feasible.

scholarly journals Spin-up in a tank induced by a rotating bluff body

1999 ◽  
Vol 388 ◽  
pp. 49-68 ◽  
Author(s):  
D. MAYNES ◽  
J. KLEWICKI ◽  
P. McMURTRY
Keyword(s):  
Steady State ◽  
Turbulent Diffusion ◽  
Bluff Body ◽  
Fluid Velocity ◽  
Tangential Velocity ◽  
The Body ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
Acceleration Rate ◽  
Time Required

Spin-up of a turbulent flow in a cylindrical tank caused by a rotating bluff body has been investigated using flow visualization, fluid velocity measurements, and hydrodynamic torque measurements. During the spin-up process three distinct temporal regimes exist. These regimes are: (i) a build-up regime where the torque and the tangential velocity fluctuations in the close proximity of the body remain constant; (ii) a decay regime where these quantities decay with power-law relations; and (iii) a mean flow steady state where these values remain relatively constant. Experiments were conducted in two tanks differing in volume by a factor of 80 and with a large range of bluff body sizes. A non-dimensional time scale, τ, based upon turbulent diffusion is determined and the tangential velocity fluctuations and torque coefficient start to decay at a fixed value of τ. Likewise, steady state is attained at a larger fixed value of τ. This time scaling is physically based upon the time required for momentum to be transferred over the entire tank volume due to turbulent diffusion, and is general for any body size, tank size, rotation rate, and acceleration rate.

A Fluidic Actuator for Active Combustion Control

2008 ◽  
Author(s):  
Daniel Guyot ◽  
Christian Oliver Paschereit ◽  
Surya Raghu
Keyword(s):  
Heat Release ◽  
Fast Moving ◽  
Oscillation Frequency ◽  
Bluff Body ◽  
Combustion Instability ◽  
Combustion Control ◽  
Flow Modulation ◽  
Fuel Flow ◽  
Oscillation Frequencies ◽  
Instability Frequency

In this work the performance of a fluidic actuator in an active combustion control scheme is demonstrated. The actuator was tested in two different burner configurations, a bluff body burner and a generic swirl-stabilized burner, where it modulated parts of the fuel flow. The oscillation frequency was controlled by varying the inlet mass flow of the actuator. Fluidic actuators are of special interest for fuel-based active control schemes featuring high frequency fuel flow modulation, as they are much more durable then conventional valves due to the absence of fast moving parts. Hot wire measurements were performed to investigate the fluidic actuator’s oscillation characteristics without combustion. The actuator was then incorporated into a bluff body burner and a swirl-stabilized burner, respectively, where it modulated parts of the fuel flow blended with nitrogen. Pressure and heat release fluctuations in the combustor were recorded and images of the flame were taken. For both burners the heat release response of the flame to fuel flow modulation was first studied during stable combustion. The spectra of the heat release signals showed a clear peak corresponding to the fluidics’ oscillation frequency, thus validating the ability of the actuator to influence the combustion process. As the next step, each of the two combustors was operated at conditions that featured a strong low-frequency combustion instability when no fuel was modulated. In case of the bluff body burner applying fuel modulation resulted in attenuation of the combustion instability for some oscillation frequencies. The attenuation was highest when modulating the fuel flow in between the fundamental instability frequency and its subharmonic. Modulating the fuel flow at the subharmonic, however, resulted in an amplification of the instable mode. Also when applied to the swirl burner, the fludics’ fuel flow modulation caused a significant reduction of the pressure oscillations, although the actuator could only be operated at oscillation frequencies much lower than the instability frequency due to the attached tubes. The results obtained in this work show that the fluidic actuator in use allows for fuel modulation and hence combustion control without the need for complex and fast moving parts, thus ensuring a long actuator lifetime. This makes the fluidic actuator highly appropriate for application in industrial gas turbines.

scholarly journals Optimasi Gasifikasi Serbuk Tandan Kosong Kelapa Sawit Menggunakan Powder Gasifier Type Cyclone

2019 ◽  
Vol 39 (3) ◽  
pp. 258
Author(s):  
Riksa Prayogi Widyaprawira ◽  
Radi Radi ◽  
Bambang Purwantana
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Fluid Velocity ◽  
Mass Rate ◽  
Empty Fruit Bunches ◽  
Fuel Ratio ◽  
Gasification Process ◽  
Air Speed ◽  
Fresh Fruit Bunches ◽  
Cfd Method

Every year, palm-oil production is increasing. Each ton of fresh fruit bunches produced to 22%–23% of oil palm empty fruit bunches (OPEFB). Based on the laboratory test, OPEFB contains 69,72% volatile and 3353,97 kcal/kg of calor. Aim of the research is to determine size material OPEFB in gasification process, determine combination AFR (Air Fuel Ratio) in gasifier tipe cyclone so that produce optimal energy and to prediction gasification process with CFD method (Computational Fluid Dynamic). The powder gasifier cyclone type method is used to convert this into renewable energy. The research method consists of OPEFB powder material with 14, 30 and 50 mesh treatment, 4 air-fuel ratio, and material mass rate treatments, and variations of the length of middle-pipe treatment. The weight of each sample is 500 g, added with 100 g of charcoal and repeated 3 times. The result shows the mesh A3 has the highest temperature at 348.23 °C, 1008,68 kcal/kg of heat value, 30.07% of efficiency, 97.81 kg/kg of AFR value, but has the lowest engine working capacity (EWC) with 14.65 kg/hours. Based on sensor test, A3 treatment, the voltage of monoxide sensor output is 1.45 mV; 1.81 mV of hydrogen; and methane at 0.66 mV. In the combination of air speed and screw rotational treatment, AFR values were generated by treatment B4 with EWC value of 20 kg/hour and AFR of 97.1 kg/kg. The highest gasmonoxide sensor results in treatment B4 is 1.58 mV; hydrogen 1.98 mV. Based on the length of the enter pipe in the reactor, treatment C1 produces an optimal value of the EWC value at 16.6 kg/hour, the heat energy value is 997 kcal/kg, the efficiency value is 29.73% and the AFR value is 82,87 kg/kg. In treatment C1 the gas monoxide sensor voltage is 1.6 mV; and methane is 1.46 mV. The CFD simulation shows that the distribution of temperature, fluid velocity and pressure in the middle iteration have a significant increase. This can be influenced by the dimensions of powder gasifier cyclone type with CFD simulation.

On the Development of a Thermal Comfort Control for Classrooms Conditioned by Split-Type Systems

2019 ◽  
Author(s):  
Anastacio Silva Junior ◽  
Nathan Mendes ◽  
Rogério Vilain ◽  
Marcelo Pereira ◽  
Katia Cordeiro Mendonça
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Low Cost ◽  
Type System ◽  
Type Systems ◽  
General Purpose ◽  
Representative Point ◽  
Air Velocity ◽  
Comfort Index ◽  
Air Speed

Abstract Thermal comfort conditions may vary substantially within an air-conditioned room equipped by split-type systems. In this work, the comfort conditions in a classroom were evaluated experimentally based on the PMV index, according to ISO 7730 Standard that defines the thermal satisfaction in occupied environments. The experiment was carried out at three different supply airflows (high, medium and low) and three set-point temperatures (23, 24 and 25°C). The results showed that there is a considerable variation in the air velocity field in the room as well as in the PMV values for three different supply airflows, consequently significant changes of thermal comfort indices can be noticed. Several curves were adjusted aiming to express the values of PMV, deriving a simplified comfort index for rooms conditioned by split-type systems based on dry-bulb air temperature and air speed. The purpose of this adjustment is to obtain an equation that provides the value of the comfort index for cooling purposes. Thus, for a certain condition of use, one can predict what will be the value of PMV in an occupied environment, enabling the implementation of a control system of the comfort according to this new index (ICS). The variables considered in obtaining the curve were the air temperature (Tar) and the air velocity (Var), since these two variables can be controlled directly by the split-type system. The general purpose of this work is to provide experimental data for the development of a low-cost device to automatically control ICS-based thermal comfort in a space conditioned by a split-type system through a single and representative point within the classroom.

scholarly journals Versatile Voltage-Mode Biquadratic Filter and Quadrature Oscillator Using Four OTAs and Two Grounded Capacitors

Electronics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1493
Author(s):  
San-Fu Wang ◽  
Hua-Pin Chen ◽  
Yitsen Ku ◽  
Chia-Ling Lee
Keyword(s):  
Integrated Circuit ◽  
Oscillation Frequency ◽  
Low Cost ◽  
Circuit Complexity ◽  
Low Noise ◽  
Active Components ◽  
Quadrature Oscillator ◽  
Voltage Mode ◽  
Biquad Filter ◽  
Oscillation Condition

This article presents a versatile voltage-mode (VM) biquad filter with independently electronic tunability. The proposed structure using one dual-output operational transconductance amplifier, three single-output operational transconductance amplifiers (OTAs) and two grounded capacitors was explored to derive a new VM quadrature oscillator with the independent control of the oscillation frequency and the oscillation condition. The proposed versatile VM biquad filter achieves nearly all of the main advantages: (i) simultaneous realizations of band-reject, band-pass, and low-pass from the same architecture, (ii) multiple-input and multiple-output functions, (iii) independent electronic adjustability of quality factor and resonant angular frequency, (iv) no resistor needed, (v) all input terminals with cascade functions, (vi) no additional inverting amplifier for input signals, (vii) using only grounded capacitors, and (viii) easy to implement a VM quadrature oscillator with independent electronically controlled oscillation frequency and oscillation condition. The proposed versatile VM biquad filter employs only four OTAs and two grounded capacitors. The active components of the proposed VM biquad filter are one less than that of recent reports. The proposed circuit also brings versatility and simplicity to the design of VM biquad filters and VM quadrature oscillators. Filters and oscillators with less active and passive components have the advantages of low cost, low power dissipation, low circuit complexity, and low noise. Commercially available integrated circuit LT1228 and discrete components can be used to implement the proposed OTA-based circuits. The simulation and experiment results validated the theoretical analysis.

A 200 °C Quad-Output Buck Type Switched Mode Power Supply IC

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000022-000027
Author(s):  
Daniel T. Goff ◽  
Steve J. A. Majerus ◽  
Walter Merrill
Keyword(s):  
Power Supply ◽  
Oscillation Frequency ◽  
Low Cost ◽  
Bias Current ◽  
Buck Converter ◽  
Step Response ◽  
Level Shift ◽  
Output Current ◽  
Sensors And Actuators ◽  
Switched Mode Power Supply

A high temperature (>200 °C), quad-output, buck type switched-mode power supply (SMPS) IC capable of operating over a wide input supply range of 6 V to 15 V is described. The IC is a compact power supply solution for multi-voltage microprocessors, sensors, and actuators. The SMPS topology is a 112 kHz fixed-frequency, synchronous buck converter with slope compensation. A novel internal feedback design enables the output voltages to be pin-programmed to one of three common supply voltages—5 V, 3.3 V, or 1.8 V—while an external resistor divider can also be used for arbitrary voltage programming. Integrated power supply output MOSFET switches minimize the external part count and synchronous rectification reduces power dissipation and improves current capacity. The IC was fabricated in a conventional, low-cost, 0.5 μm bulk CMOS foundry process. Patented circuit design techniques allow the IC to operate in excess of 200 °C and circuit operation was demonstrated at ambient temperatures up to 225 °C. The foundry process is optimized for 5 V applications, however, the IC accepts input voltages up to 15 V and can produce outputs up to 10 V by utilizing extended drain single- and double-sided NMOS and PMOS transistors for the linear regulator pass transistor, error amplifier, and SMPS switches. The high-side FETs are controlled through capacitive coupled level shift circuits to ensure the gate-oxide voltage limits are not exceeded while still maintaining fast signal transitions. The IC also includes a tunable, 25 MHz monolithic oscillator that is programmable over a SPI serial interface. The oscillator bias current is comprised of a programmable constant-gm bias current and a programmable PTAT bias current. The programmability can be used to set the oscillation frequency, but can also be used together with a calibration curve on a microcontroller to achieve a more stable oscillation frequency over temperature. The output current of the quad SMPS was limited to 70 mA by a lower than expected saturation current of the extended-drain PMOS switch devices. The system showed good line regulation (<0.1%) and 50% load step response stability (+/− 100 mV) at a nominal output current of 50 mA when tested at 200 °C ambient.

Sign in / Sign up

Export Citation Format

Share Document