차량용 미세먼지 센서용 소형 축류팬의 유동과 소음 성능 개선

송영욱,유서윤,정철웅,이인혁 한국음향학회 2023 韓國音響學會誌 Vol.42 No.1

Recently, as interest in air quality in vehicles increases, the use of fine dust detection sensors for air quality measurement is becoming common. An axial-flow fan is inserted in the fine dust sensor installed in the air conditioning system in the vehicle to prevent dust from sinking directly on the sensor. When the sensor operates, the flow noise caused by the rotation of the axial-flow fan acts as a major noise source of the fine dust sensor. flow noise is recognized as one of the product competitiveness of fine dust sensors. In this study, the noise was gradually reduced at the same flow rate by improving the flow performance of the small axial flow fan. First, a virtual fan performance tester consisting of about 20 million grids was developed to analyze the aerodynamic performance of the target small axial-flow fan. In addition, the flow field was simulated by using compressible Large Eddy Simulation for direct computation of flow noise as well as high-accurate prediction of flow rate. The validity of numerical method are confirmed through the comparison of predicted results with experimental ones. After the effects of pitch angle on flow performance were analyzed using the verified numerical method, the pitch angle was determined to maximize the flow rate. It was found that the flow rate was increased by 8.1 % and noise was reduced by 0.8 dBA when the axial-flow fan with the optimum pitch angle was used. 최근 차량 내 공기 질에 대한 관심이 증가함에 따라 공기 질 측정을 위한 미세먼지 감지 센서의 사용이 보편화되고 있다. 차량 내 에어컨 시스템에 설치되는 미세먼지 감지 센서 내에는 센서에 직접적으로 먼지가 가라앉지 않도록하기 위한 축류팬이 삽입되어 있다. 센서 작동 시 축류팬의 회전으로 인한 유동 소음은 미세먼지 감지 센서의 주요 소음원으로 작용한다. 차량의 전동화가 급격화가 진행되면서 이러한 유동소음은 미세먼지센서의 제품 경쟁력의 하나로인식되고 있다. 본 연구에서는 이러한 미세먼지센서용 소형 축류팬의 유동 성능을 개선하여 동일 유량에서 소음을 점감하였다. 먼저 대상 소형 축류팬의 공기역학적 성능을 분석하기 위해 약 2000만 개의 격자로 구성된 가상 팬 성능시험기를 구축하였다. 또한, 유량의 정확한 예측 뿐만 아니라 유동소음의 직접 계산을 위하여 압축성 대와류모사법을 사용하여 유동장을 모사하였다. 수치방법의 유효성은 예측결과와 실험 결과와의 비교를 통하여 확인하였다. 유효성이 검증된 수치 기법을 이용하여 피치각이 유동 성능에 미치는 영향을 분석하였고, 유량을 최대화할 수 있는 피치각을 도출하였다. 최적 피치각을 적용한 축류팬을 사용했을 때 유량은 8.1 % 증가하고 동일 유량에서 소음이 0.8 dBA 감소함을 확인하였다.

A disposable microfluidic flow sensor with a reusable sensing substrate

Kim, Jinho,Cho, Hyungseok,Han, Song-I,Han, Arum,Han, Ki-Ho Elsevier 2019 Sensors and actuators. B, Chemical Vol.288 No.-

<P><B>Abstract</B></P> <P>In many biological, medical and pharmaceutical applications, disposable flow sensors are highly desired to prevent biological contamination. However, due to their high cost, conventional microfluidic flow sensors are difficult to be used as disposable. This paper introduces a disposable microfluidic flow sensor (disposable-μFSensor) consisting of a disposable microchannel superstrate and reusable sensing substrate, which can be assembled and disassembled simply by vacuum pressure. Because the disposable microchannel superstrate is fabricated easily and cheaply using a silicone-coated release polymer thin film, it can be replaced after a single use, while the sensing substrate can be reused continuously. Experimental results show that the sensitivity, reproducibility, response time, long-term stability, resolution, and accuracy of the disposable-μFSensor are comparable to those of commercial microfluidic flow sensors. One of the key advantages of the disposable-μFSensor is that the measurable flow rate range can be adjusted very broadly, from 10 to 650 μL/min, by simply replacing only the disposable microchannel that has different bypass channel design, without having to change the sensing substrate. To demonstrate the usefulness of the disposable-μFSensor for biological, medical and pharmaceutical applications, the developed sensor was used to control the flow rates of a droplet generator, with the generated droplets having variations in diameter and volume of less than 1.25% and 4%, respectively. In summary, we report that the disposable-μFSensor is reproducible and accurate for various applications at low cost as well as resistant to biological contamination, in contrast to conventional flow sensors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A disposable microfluidic flow sensor for preventing biological contamination. </LI> <LI> Hybrid flow sensor using a disposable microchannel and a reusable sensing substrate. </LI> <LI> Disposable microchannel made of a PET thin film; simple fabrication and low cost. </LI> <LI> Performance comparable to that of commercial flow sensors. </LI> <LI> Adjustable full-scale flow rate by replacing disposable microchannel without changing substrate. </LI> </UL> </P>

Improvements in the Performance of a Microthermal Flow Sensor using Asymmetrically Located Temperature Sensors

이장현,김탁근,김동호,김주현,임시형 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.2

A microthermal flow sensor was developed using microfabrication techniques. The flow sensor comprised a microheater and three pairs of resistive temperature detector (RTD) sensors. The heater and the sensors were made of platinum thin films, and they were located in the middle of a thin oxide/nitride-layered membrane, which was used for thermal isolation. The operating characteristics of the developed microthermal flow sensor were investigated for various gap distances between the central heater and the upstream/ downstream RTD sensors. When the upstream/downstream RTD sensors were placed at asymmetric distances away from the central heater, the performance of the sensor improved for an air flow rate of 0-10 slpm. Our results indicate that an asymmetrical gap distance between the central heater and the upstream/downstream RTD sensors can be a key factor in improving the sensitivity and dynamic range of a microthermal flow sensor. To the best of the authors’ knowledge, these results are the first to experimentally demonstrate that an asymmetrical placement of RTD temperature sensors can improve the sensitivity and dynamic range of a microthermal flow sensor. Manuscript

유전체 (Si3N4/SiO2/Si3N4) 멤브레인 위에 제작된 크로멜-알루멜 열전 유량센서

이형주 ( Lee Hyeong Ju ),김진섭 ( Kim Jin Seob ),김여환 ( Kim Yeo Hwan ),이정희 ( Lee Jeong Hui ),최용문 ( Choe Yong Mun ),박세일 ( Park Se Il ) 한국센서학회 2003 센서학회지 Vol.12 No.3

Si₃N₄/SiO₂/Si₃N₄ 열차단막을 이용한 크로멜-알루멜(chromel-alumel) 열전(thermoelectric) 유량센서를 제작하였다. 백금 박막 히터의 저항온도계수는 약 0.00397/℃이었고, 크로멜-알루멜 열전쌍(thermocouple)의 Seebe다 계수는 약 36 μN/K이었다. 기체의 열전도도가 증가할수록 유량센서가 나타내는 열기전력은 감소하였으며, 히터의 온도가 증가하거나 히터와 열전쌍 사이의 간격이 감소할수즉 유량센서의 N₂유량에 대한 심도는 증가하였다. 히터 전압을 약 2.5 V로 하였을 때 유량센서의 N₂ 유량에 대한 감도는 약 1.5 ㎷/sccm^(1/2)이었고, 열 응답시간은 약 0.18초이었다. 크로켈-알루켈 열전 유량센서의 유량감도에 있어서 신형 범위가 Bi-Sb 유량센서의 것보다 더 넓게 나타났다. A chromel-alumel thermoelectric flow sensor using Si₃N₄/SiO₂/Si₃N₄thermal isolation membrane was fabricated. Temperature coefficient of resistance of thin film Pt-heater was about 0.00397/℃, and Seebeck coefficient of chromel-alumel thermocouple was about 36 ㎶/K. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and N₂-flow sensitivity increased as heater voltage increased or the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, N₂-flow sensitivity and thermal response time of the sensor were about 1.5 ㎷/sccm^(1/2) and 0.18 sec., respectively. Linear range in flow sensitivity of the flow sensor was wider than that of Bi-Sb flow sensor.

Gas-Flow Sensor using Optical Fiber Bragg Grating(FBG)

심준환,조석제,유영호,손경락 한국항해항만학회 2008 한국항해항만학회지 Vol.32 No.9

We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FBG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is thus simple and immune to electromagnetic interference(EMI). The FBG sensor was consisted of the sensing element and a coil heater. The metal coil was used to supply the current to the FBG. While some currents supply to the coil, the refractive index of the FBG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced. In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to 20 ℓ/min with a resolution of approximately 1ℓ/min at the applied currents of 100 ㎃ and 120 ㎃. The measured sensitivities were 15.3 pm/ℓ/min for 100 ㎃ and 20.2 pm/ℓ/min for 120 ㎃. We have proposed and demonstrated an gas-flow sensor using optical fiber bragg grating(FBG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is thus simple and immune to electromagnetic interference(EMI). The FBG sensor was consisted of the sensing element and a coil heater. The metal coil was used to supply the current to the FBG. While some currents supply to the coil, the refractive index of the FBG under the coil is changed and thus the wavelength shift of fiber optic sensor was induced. In this work, the wavelength shift according to flow-rate was experimentally studied and was used to evaluate the gas flow-rate in a gas tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to 20 ℓ/min with a resolution of approximately 1ℓ/min at the applied currents of 100 ㎃ and 120 ㎃. The measured sensitivities were 15.3 pm/ℓ/min for 100 ㎃ and 20.2 pm/ℓ/min for 120 ㎃.

Biomimetic Flow Sensor for Detecting Flow Rate and Direction as an Application for Maneuvering Autonomous Underwater Vehicle

Le Giang Tran,Woo-Tae Park 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.1

Attaining the information of the hydrodynamic flow rate and direction is essential to the maneuvering of autonomous underwater vehicles (AUVs). This work presents a pillar-based flow sensor that measures hydrodynamic flow rate and direction. We propose a design that mimic the working principle of the neuromast, a ubiquitous organ in fishes that sense the water flow. By utilizing advances in piezo-resistive pressure sensors and 3D printing technology, sensor fabrication becomes fast and cost-effective, owing to reductions in labor and material cost for small batches. Measured results showed that the sensor sensitivity was 9.24 mV/m/s in the single mode and 20.3 mV/m/s in the differential mode. The resolution of the flow sensor was measured to be 4.93 mm/s in the water tunnel testing. The angular resolution of the flow sensor was 2.25°.

상류 센서를 이용한 Reτ=395의 난류 채널 유동 반대 제어

김금영,윤진혁,이정일 대한기계학회 2023 大韓機械學會論文集B Vol.47 No.3

In this study, opposition control with upstream sensors is applied to the turbulent channel flow at Reτ =395. As a control input, the amplitude of the actuation at the wall is proportional to the transverse velocity at an upstream sensing location in the opposite direction and varies over time. We perform direct numerical simulations of turbulent channel flow and evaluate the control performance of skin friction reduction based on the locations of upstream sensor. It is shown that the opposition control with upstream sensors exhibits a better control performance than that with a sensor directly above the actuator. The use of upstream sensors for the opposition control effectively decreases the strength of streamwise vortices and velocity fluctuations near the wall, resulting in the maximum skin friction reduction of 26% for the turbulent channel flow with the optimal upstream sensor location. 본 연구에서는 Reτ =395에서 상류 센서 기반 반대 제어를 난류 채널 유동에 적용하였다. 제어 입력으로서, 벽에서의 가진 크기는 가진의 상류에 위치한 센싱 위치의 수직 방향 속도에 비례하고 반대 방향의 값으로 결정되며 시간에 따라 변화한다. 난류 채널 유동의 직접 수치 모사를 수행하고, 상류 센서 위치에 따른 마찰 저항 감소의 제어 성능을 평가하였다. 이를 통해 가진 위치 바로 위의 센서를 활용하는 것보다 상류 센서를 사용하는 반대 제어가 더 좋은 성능을 보임을 확인하였다. 상류 센서를 활용한 반대 제어는 벽 근처 주유동 방향 와류의 강도와 속도 섭동을 효과적으로 약화시켰으며, 최적의 상류 센서 위치에서 난류 채널 유동의 마찰 저항을 최대 26% 감소시켰다.

NUMERICAL INVESTIGATION ON BOTTOM GAP OF MICRO FLOW SENSOR

Abdullahl Mohd Zulkiefly,Kouta T,Kamijo Takuma,Yamamoto Makoto,Honami Shinji,Kamiunten Shoji Korea Society of Computational Fluids Engineering 2005 한국전산유체공학회지 Vol.10 No.1

Micro sensor is very useful for flow measurements in a number of engineering applications. Especially, it is necessary for the development of MEMS. This paper presents the 3D numerical simulation of flows around a micro flow sensor, which is mounted on a flat plate. The effects of the sensor configuration (i.e. bottom gap) and the Reynolds number on the flow field are numerically investigated. The numerical results indicate that the bottom gap clearly affects the flow fields over the top surface of the sensor. The Reynolds numbers also show a significant influence on the flow nature, especially on the recirculation zone at downstream of the sensor. The present results illustrate a certain improvement on the flow field for the sensor installed at O.5mm above the wall with four pillars, comparing with that directly mounted on the wall.

Experimental study of bubbly swirling flow in a vertical tube using ultrasonic velocity profiler (UVP) and wire mesh sensor (WMS)

Ari Hamdani,Tomonori Ihara,Nobuyoshi Tsuzuki,Hiroshige Kikura 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

Two-phase air-water bubbly swirling flow through a pipe is a complex turbulent flow and its prediction is still challenging. The present paper describes the experimental investigation of the air-water bubbly swirling flow in vertical co-current flow. Swirling flow is induced by a twisted tape in a 20 mm inner diameter pipe. The flow is investigated using Ultrasonic velocity profiler (UVP), which allows the measurement of liquid and gas velocities simultaneously. Furthermore, simultaneous measurement of void fraction is performed using Wire mesh sensor (WMS). The experimental results reveal that swirling flow has significant impact on bubbles’ distribution. In low liquid flow rate, the average bubble velocity is fairly uniform along the radial position and void fraction increases in the near wall region. However, increasing liquid flow rate at constant gas flow rate leads to increase in void fraction in the core region, this is mainly due to drift velocity which is affected by centrifugal force. Experimental findings and parametric trends based on the effects of swirling flow are summarized and discussed.

Design and Fabrication of Six-Degree of Freedom Piezoresistive Turbulent Water Flow Sensor

Dao, Dzung Viet,Toshiyuki, Toriyama,Wells, John C.,Susumu, Sugiyama 한국센서학회 2002 센서학회지 Vol.11 No.4

This paper presents the design concept, theoretical investigation, and fabrication of a six-degree of freedom (6-DOF) turbulent flow micro sensor utilizing the piezoresistive effect in silicon. Unlike other flow sensors, which typically measure just one component of wall shear stress ^[1,2], the proposed sensor can independently detect six components of force and moment on a test particle in a turbulent flow. By combining conventional and four-terminal piezoresistors in Si (111), and arranging them suitably on the sensing area, the total number of piezoresistors used in this sensing chip is only eighteen much fewer than the forty eight piezoresistors of the prior art piezoresistive 6-DOF force sensor ^[3].