• 한국추진공학회지
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• 제24권6호
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• pp.16-27
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• 2020

넓은 비행영역에서 스크램제트 엔진의 운용을 위해, 비행 조건의 변화에도 안정적인 성능을 나타내는 흡입구의 설계가 중요하다. 본 연구에서는 마하수 4~6, 받음각 -6도~6도의 넓은 비행영역에서 안정적인 성능을 얻기 위한 2D 고정형 흡입구의 설계 방법에 대한 연구를 수행하였다. 설계 방법 및 설계 주안점에 대해 제시한 후, 넓은 비행영역에서 높은 전압력 회복율과 유량 포획율을 갖는 흡입구를 설계함에 있어 가장 중요한 설계요소인 초기 압축각도와 비행 마하수 설계점에 따른 성능예측 및 분석을 수행하였다. 분석 결과를 바탕으로 넓은 비행영역에서 안정적인 성능을 나타내기 위한 두 가지 주요 설계요소의 선정기준을 제시하였다.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2791-2796
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• 2010

In the present study, we constructed a membrane inlet assembly for selective permeation of volatile airborne organic compounds for subsequent analysis by time-of-flight mass spectrometry. The time-dependent diffusion of analytes through a $75\;{\mu}m$ thick polydimethylsiloxane membrane was measured by monitoring the ion signal after a step change in the sample concentration. The results fit well to a non-steady-state permeation equation. The diffusion coefficient, response time, and sensitivity were determined experimentally for a range of polar (halogenated) and nonpolar (aromatic) compounds. We found that the response times for several volatile organic compounds were greatly influenced by the alkyl chain length as well as the size of the substituted halogen atoms. The detection limits for benzene, ethylbenzene, and 2-propanol were 0.2 ppm, 0.1 ppm, and 3.0 ppm by volume, respectively, with a linear dynamic range greater than three orders of magnitude. These results indicate that the membrane inlet/time-of-flight mass spectrometry technique will be useful for a wide range of applications, particularly for in situ environmental monitoring.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.303-308
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• 2005

A miniaturized time-of-flight mass spectrometer with an electron impact ionization source and sheet membrane introduction has been developed. The advantages and features of this mass spectrometer include high sensitivity, simple structure, low cost, compact volume with field portability, and ease of operation. A mass resolution of 400 at m/z 78 has been obtained with a 25 cm flight path length. Under optimized conditions, the detection limits for the volatile organic compounds (VOCs) studied were 0.2-10 ppm by volume with linear dynamic ranges greater than three orders of magnitude. The response times for various VOCs using a silicone membrane of 127 $\mu$m thickness were in the range 4.5-20 s, which provides a sample analysis time of less than 1 minute. These results indicate that the membrane introduction/time-of-flight mass spectrometer will be useful for a wide range of field applications, particularly for environmental monitoring.

• 한국추진공학회지
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• 제19권3호
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• pp.65-72
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• 2015

본 연구에서는 이중램제트 엔진 및 로켓/터빈 기반 복합사이클 엔진에의 활용을 위해 Mach 3에서부터 Mach 8까지 넓은 마하수 영역에서 적용이 가능한 초음속흡입구의 형상설계를 수행하고 그 설계방법론에 대해 고찰하였다. 축대칭 가변흡입구를 기본 개념으로 중심콘 각도 및 경사충격파 각도를 이용한 기하학적 관계식으로부터 흡입구 형상을 설계하였으며, 100%에 준하는 포획면적비를 갖도록 하였다. 또한 전산해석결과로부터 Mach 3~8까지 조건에서 흡입구 중심콘에서 발생한 충격파가 올바르게 배치되는 것을 확인하였다.

• 한국분무공학회지
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• 제27권2호
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• pp.66-76
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• 2022

This study presents a prediction methodology of transport properties using the methane-based TRAPP (m-TRAPP) method in a wide range of temperature and pressure conditions including both subcritical and supercritical regions, in order to obtain thermo-physical properties for hydrocarbon aviation fuels and their products resulting from endothermic reactions. The viscosity and thermal conductivity are predicted in the temperature range from 300 to 1000 K and the pressure from 0.1 to 5.0 MPa, which includes all of the liquid, gas, and the supercitical regions of representative hydrocarbon fuels. The predicted values are compared with those data obtained from the NIST database. It was demonstrated that the m-TRAPP method can give reasonable predictions of both viscosity and thermal conductivity in the wide range of temperature and pressure conditions studied in this paper. However, there still exists large discrepancy between the current data and established values by NIST, especially for the liquid phase. Compared to the thermal conductivity predictions, the calculated viscosities are in better agreement with the NIST database. In order to consider a wide range of conditions, it is suggested to select an appropriate method through further comparison with another improved prediction methodologies of transport properties.

• 항공우주기술
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• 제3권2호
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• pp.197-207
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• 2004

현재 개발중인 스마트 무인기는 일반적인 헬리콥터와 같이 수직이착륙이 가능할 뿐만 아니라 고정익기와 같이 고속의 비행이 가능함을 목표로 하고 있다. 그러므로 흡기구는 여러 비행조건에서 엔진이 제 효율을 낼 수 있도록 충분한 공기를 흡입하루 수 있어야 함은 물론이고 비행체의 운행속도에 따라서도 그 효율이 어느 이상 저하되지 않도록 설계되어야 한다. 본 논문에서는 고속 비행체에 적합한 pitot 형태와 엔진 특성에 따른 플레넘 챔버를 장착한 흡기구를 설계하였다. 그리고 CFD-ACE를 이용하여 설계된 흡기구의 성능 해석을 수행하였으며 엔진 내부에서의 swirl과 distortion을 조사하고 압력손실에 대해서 연구하였다.

• 한국항공운항학회지
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• 제11권1호
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• pp.5-16
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• 2003

The present study was carried out to develop highly efficient RC ornithopter 'Songgolmae' powered by motor and battery. Designed electric ornithopter, which has the dimension of O.88m(W)${\times}$0.56m(L)${\times}$0.15m(H), is smaller than a conventional ornithopter. This ornithopter weighs 277 grams and has 3 channels radio control. It runs on an electric motor by a lithium polymer battery and has a gear ratio of about 75${\sim}$95 to 1 to flap its 88 cm wingspan. The aerodynamic performance of the ornithopter, applied to a flapping motion only, was validated by flight tests. Flight times have exceeded 23 minutes until the battery was used up. The flight test results indicate that the ornithopter developed here has sufficient thrust to propel itself in a forward flight. From the economical point of view and the handling of the RC ornithopter, it can be said that the developed robot ornithopter is an effective RC ornithopter. This robot ornithopter flies its way high into the sky just like a real bird flies. The robot ornithopter is used for a wide range of missions.

• International Journal of Aeronautical and Space Sciences
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• 제14권3호
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• pp.247-255
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• 2013

The flight control of re-entry vehicles poses a challenge to conventional gain-scheduled flight controllers due to the widely spread aerodynamic coefficients. In addition, a wide range of uncertainties in disturbances must be accommodated by the control system. This paper presents the design of a roll channel controller for a non-axisymmetric reentry vehicle model using the trajectory linearization control (TLC) method. The dynamic equations of a moving mass system and roll control model are established using the Lagrange method. Nonlinear tracking and decoupling control by trajectory linearization can be viewed as the ideal gain-scheduling controller designed at every point along the flight trajectory. It provides robust stability and performance at all stages of the flight without adjusting controller gains. It is this "plug-and-play" feature that is highly preferred for developing, testing and routine operating of the re-entry vehicles. Although the controller is designed only for nominal aerodynamic coefficients, excellent performance is verified by simulation for wind disturbances and variations from -30% to +30% of the aerodynamic coefficients.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.393-396
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• 2006

본 논문은 이중모드램제트(램제트-스크램제트 연합 작동) 엔진의 작동한계 분석을 기초하여 광범위한 비행 마하수를 충족시키는 엔진에 대한 설계 인자 (흡입구와 연소실)를 고찰하였다. 램제트와 스크램제트의 작동 천이 비행 마하수를 도출하고, 두가지 경우의 연소기(일정한 압력과 일정한 단면적)의 연소실 작동 한계 특성을 파악하여 이중모드 램제트 엔진의 설계 개념을 연구하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.118.2-118
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• 2001

This research describes a development of laser distance sensor with precise resolution even in the case that the object surface has some curvature. There are typical two methods in measuring the distance by using laser light source, so called time of flight and optic-triangular methods. Both methods have an advantage and a disadvantage each other. In general, the time of flight method produces wide range of the measurement, but low accuracy. The other method is vice versa. In this research, the optic-triangular methods with one-dimensional CCD cell are proposed to obtain the precise distance measure from the sensor the surface of the curved object ...