• Title/Summary/Keyword: Cavity Back

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A Case Study on The Reduction and Examination for Noise and Vibration of Backpass Heat Surface in the Power Plant Boiler (발전용 보일러의 후부 전열면 소음진동 저감에 관한 사례 연구)

  • Lee, Gyoung-Soon;Lee, Tae-Hoon;Moon, Seung-Jae;Lee, Jae-Heon
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.642-647
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    • 2008
  • The boiler structure is determined by combustion characteristics and construction costs in the combustion chamber of a large commercial boiler. The heat transfer in boiler is composed of the radiation and the convection. The convective heat transfer has happened to back-pass heating surface. The combustion gas sequentially passes through the reheater tube, 1st economizer tube, and 2nd economizer tube. In case of being lowered in boiler height, we have to install additional tube bundle in back-pass heating surface for increasing the heat transfer of boiler, which causes the noise and vibration from combustion gas. When the combustion gas passes through the back-pass tube bundle in specified load of commercial boiler, this paper analyzes the acoustic characteristics between vortex-shedding frequency and natural frequency in tube bundle cavity. The case study reduce the resonance by changing natural frequency characteristics of tube-bundle cavity using a way to install ant-noise baffle in the direction of combustion gas flow.

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Wideband Cavity Back Antenna for Signal Intelligence (신호 정보 수집용 광대역 캐비티 백 안테나)

  • Jeoung, Gu-Ho;Lee, Seong-Kyu;Choi, Jae-Hoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.12
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    • pp.1044-1052
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    • 2016
  • In this paper, a cavity back slot antenna with a rotated rectangular patch is proposed. The proposed antenna consists of a ground plane with cavity structure, a microstrip feed line, and a rectangular patch with slot. With a dimension of $55mm{\times}40mm{\times}10mm$, the proposed antenna has the wide bandwidth due to the cavity structure. Measured 10 dB return loss bandwidth and fractional bandwidth of the proposed antenna is 5,030 MHz(3.02~8.05 GHz) and 90.9 % at the center frequency of 5.05 GHz. The proposed antenna is designed and simulated using ANSYS HFSS v.15.0.0. The designed antenna is fabricated and tested to validate its performances.

Design of Cavity-Backed Microstrip Dipole Array Antennas with Enhanced Front-to-Back Ratio (전후방비가 개선된 Cavity-Backed 마이크로스트립 다이폴 배열 안테나 설계)

  • You, Dong-Gyun;Jeon, Jung-Ik;Lee, Hyoung-Ki;Choi, Hak-Keun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.1
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    • pp.37-44
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    • 2009
  • In this paper, a TRS band(Trunked Radio System: $806{\sim}866\;MHz$) array antenna has a good front-to-back ratio characteristics for the mobile communication base station is proposed. The proposed array antenna is composed of the $5{\times}3$ radiated elements which are the microstrip dipole antennas with the cavity-backed reflector. For the validity of the proposed antenna, the $5{\times}3$ array antenna is designed, fabricated, and its radiation characteristics are measured. As a result of measurements, the antenna gain is over 13.3 dBi and the front-to-back ratio is over 40 dB at the useable frequency band. We confirm that the designed antenna can be used as the mobile communication base station antenna with the excellent back lobe characteristics.

A Study on the Expansion Cavity Pipe for Performance Improvement of Exhaust System in Automotive (자동차 배기성능개선을 위한 확장형 공동파이프에 관한 연구)

  • Son, Sung-Man;Park, Kyoung-Suk
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.5
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    • pp.1-6
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    • 2009
  • The temperature of exhaust gas was raised by increasing of engine movement on developing engine. Thermal of high temperature and pressure reverse in bellows, because of increasing of engine movement and the thermal performance of converter in combustion. As a result, thermal loss is increased and thermal efficiency is decreased rapidly in bellows, it can occur to damage in mechanical structure. In this study, it was necessary to analyze back pressure performance and thermal characteristic on driving condition in exhaust system. It was adapted braid type bellows and straight type exhaust pipe. It was compared with curve type exhaust pipe for lay-out on considering to design of exhaust system. It was necessary to improve thermal characteristic and back pressure performance so that expansion cavity pipe(ECP) was installed between bellows and catalyst convert. Not only decreasing back pressure was solved but also thermal characteristic problems in exhaust pipe because of increasing capacity. According to this study, the basis of data is presented when new exhaust system is designed.

Numerical Study on the Variation of Axial Thrust of Rotating Disc with Pump-Out Vane (POV가 부착된 회전 원판의 축추력 변화에 관한 연구)

  • Seong Seong-Mo;Kang Shin-Hyoung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.3 s.246
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    • pp.230-237
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    • 2006
  • Flows in the cavity with pump out vane are calculated using the CFX-Tascflow CFD code. flow calculations are performed for different values of vane height, numbers, leakage flow rate, and rotational speed. The flow is very complex and three dimensional with strong vortex and leakage flow over the vane. The variations of pressure coefficient and K-factor with these parameters and resulting effects on the thrust and torque are studied. The present study contributes to showing the capability of flow simulation of back cavity with pump-out vane. The calculated results are good enough to be used back cavity design.

A study on the technical details of masonry veneer and cavity walls - Focused on the out wyth of clay bricks - (건축물 외부 중공벽의 시공방안에 관한 연구 - 외부 점토벽돌의 사용을 중심으로 -)

  • 양순갑
    • Journal of the Korean housing association
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    • v.8 no.3
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    • pp.219-230
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    • 1997
  • Lack of technical standards, specification and inadequate execution in masonry wall construction in Korea lead to produce serious flaw problems such as crack, efflorescene, and upset etc.. The purpose of this paper is to present the practical details for Masonry cavity wall construction to prevent rain penetration and to accommodate differential movement between the inner and outer wythes of cavity walls. Considering rain penetration and differential movement of both wythes of cavity walls, provision of an adequate air space, an airtight back-up wall, clean cavity with weepholes and vents, properly positioned flashing, tie and shelf angle etc. depend on the cavity wall types will help ensure good performance. The present details included noncorrosive hot dip galvanized steel or stainless steel for metal components, plastic and ultra violet resistant polypropylene Copolymer for other components was taken into account the construction method and several types of cavity walls in Korea

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Cavity-Backed Slot Array Antenna for a Repeater System of a Satellite Digital Multimedia Broadcasting (위성 DMB 중계기용 Cavity-Backed슬롯 배열 안테나)

  • Jung Hee-Chul;Lee Hak-Yong;Jung Byungwoon;Kang Gi-Cho;Park Myun-Joo;Lee Byungje
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.4 s.95
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    • pp.366-372
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    • 2005
  • This paper presents analysis of a slot array antenna having a low side lobe level and high front-to-back ratio for a repeater system of a satellite DMB(Digital Multimedia Broadcasting) service. Antennas for this repeater system require a high gain and enough isolation to reduce interferences between signals in system. Therefore, it is necessary to suppress a side lobe level and to increase front-to-back ratio. Unlike a structure 134 by lossy microstrip lines, in this work a single cavity-backed slot antenna array using a single waveguide feed is proposed to obtain the reliability for high power handling and high radiation efficiency. The side lobe level and front-to-back ratio are enhanced with tapered array technique and an optimized vertical reflector. The measured side lobe levels in H- and E-plane are under $-33.24\;\cal{dB}$ and $-35.78\;\cal{dB}$, respectively. The front-to-back ratio over $37.84\;\cal{dB}$, and the peak gain of over $17\;\cal{dBi}$ are measured.

Speaker Identification Based on Vowel Classification and Vector Quantization (모음 인식과 벡터 양자화를 이용한 화자 인식)

  • Lim, Chang-Heon;Lee, Hwang-Soo;Un, Chong-Kwan
    • The Journal of the Acoustical Society of Korea
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    • v.8 no.4
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    • pp.65-73
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    • 1989
  • In this paper, we propose a text-independent speaker identification algorithm based on VQ(vector quantization) and vowel classification, and its performance is studied and compared with that of a conventional speaker identification algorithm using VQ. The proposed speaker identification algorithm is composed of three processes: vowel segmentation, vowel recognition and average distortion calculation. The vowel segmentation is performed automatlcally using RMS energy, BTR(Back-to-Total cavity volume Ratio)and SFBR(Signed Front-to-Back maximum area Ratio) extracted from input speech signal. If the Input speech signal Is noisy, particularity when the SNR is around 20dB, the proposed speaker identification algorithm performs better than the reference speaker identification algorithm when the correct vowel segmentation is done. The same result is obtained when we use the noisy telephone speech signal as an input, too.

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On the Penetration Phenomena for Thin and Multi-Layered Finite Thickness Plates by a Long Rod Penetrator (긴 관통자에 의한 유한박판 및 적층표적재의 관통현상 연구)

  • 이창현;홍성인
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.7
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    • pp.1759-1772
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    • 1994
  • In this study, we re-examined the Tate's modified Bernoulli equation to study penetration phenomena for long rod projectile into single or multi-layered finite thickness plates. We used the force equlibrium equation at mushroomed nose/target interface instead of conventional pressure equation at the stagnation point. In our penetration model, we considered the velocity dependent $R_t$ value for semi-infinite target and considered only the back face effect for finite target. To compensate for $R_t$ value according to target's thickness and back face effect, we used the spherical cavity expansion theory for semi-infinite plate and used the cylindrical cavity expansion theory for finite plate. Also we developed the experimental technique using make screen to measure the penetration duration time at each layered plate. In 3-layered laminated RHA/mild steel/ A1 7039 plate, we observed that spall had occured around the back face of A1 7039 plate by the stress wave interaction. Through the comparison between theoretical and experimental data including Lambert's results, we conform that our study has good confidences.

Solidification Analysis Characteristics of Back Flow Prevention Check Valve (역류방지 체크밸브의 응고해석 특성)

  • Yoon, Jung-In;Moon, Jung-Hyun;Son, Chang-Hyo;Lee, Jung-Jin
    • Journal of Power System Engineering
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    • v.19 no.3
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    • pp.69-74
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    • 2015
  • Check valves used in vessels include shock-release function on piping system, aside from basic back flow prevention. However, proper and enough protection of system is not obtainable due to use of high-pressure and bulk fluids, resulting from enlargement of vessels. In this study, casting analysis of check valves protecting systems in flow path from water hammering or back flow is conducted, using Z-CAST program. Also, molten metal filling, flow analysis, solidification analysis and shrinkage cavity analysis are conducted. The main results are as following. Regarding filling of each risering, molten metal showed stable supply condition without being isolated. It was identified that the final solidification exists on risering, but shrinkage cavity possibly might happens at the point of isolation solidification.