• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.143-148
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• 2010

항공용 연료계통의 핵심부품인 연료승압펌프(FBP)의 신뢰도를 예측/평가하기 위하여 운용중에 지속적으로 발생되는 고장자료에 근거하여 고장추세분포를 도출하는데 Weibul Distribution 형태의 통계학적인 방법(Statistical Methods)을 사용하였다. 이를 토대로 하여 고장 자료분포를 시각적으로 분석하여 신뢰성 예측을 하였다. 분석결과, 형상모수(${\beta}$), 척도모수(${\eta}$) 및 평균고장시간(MTTF)을 산출하였다. 결과로부터 주요 고장원인이 기계부품의 마모나 노후화로 인하여 발생하는 마모고장기이며 산출된 평균고장시간 이전에 예방정비를 수행해야 사전에 고장을 방지할 수 있음을 알 수 있다.

• 한국항공우주학회지
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• 제41권5호
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• pp.391-403
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• 2013

전기 추진 프로펠러 항공기는 기존의 제트엔진으로부터 나오는 유해한 배기가스로 인한 환경적 우려와 국가 에너지 안보 차원에서 새로운 관심을 받고 있다. 그러나 전통적인 항공기 사이징 방법들은 여러 종류의 에너지원과 동력 시스템을 사용하는 전기 추진 항공기에 바로 적용될 수 없다. 본 연구에서는 일반화된 동력기반 사이징 기법에 기초한 전기 추진 항공기 사이징의 실제 예를 제시하였다. 여기서 일반 항공기는 프로펠러, 고온초전도모터, 수소가 연료로 사용되는 연료전지, 동력 조절 장치로 구성되는 전기 추진시스템에 의해 구동된다. 기술 향상의 영향을 평가하기 위해 전기 구성품들의 두 가지 다른 기술 구성을 가정하여 항공기 사이징을 수행하였고, 전형적인 형태의 기준 항공기와 사이징 결과를 비교하였다.

• 한국기후변화학회지
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• 제8권2호
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• pp.177-186
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• 2017

In this research, we have developed standardized procedures for preparing of emission inventories on military sector. The procedures are as follows; 1) Identify all relevant emission sources list of military sector in Republic of Korea. 2) Select methods to estimate GHGs emissions by source categories such as heating boilers, tactical vehicles, military vessels and military aviation from US EPA, IPCC, EEA/EMEP, and ROK Ministry of Environment. 3) Identify and select data sources for activities and parameters from Korea annual oil statistics and Korea Procurement system. 4) Compare with each GHGs emission used by each activities. The conclusive results utilized by emission source categories and associated factors are described as follows; In 2013, GHGs was estimated 2,656 kilotons $CO_2-eq$ emitted by military sector. The diesel combustion contributed from a minimum of 43.8% to a maximum of 50.2% and JP-8 contributed from a minimum of 43.7% to a maximum of 52.8% to the 2001~2015 GHGs emission trend. In the result of comparing GHGs emissions with Korea Annual Oil Statistics (Tier 1) and supplied fuel through the Korea Procurement System (Tier 2) in 2015, the total GHGs emission was 2,867 kilotons $CO_2-eq$ estimated by Tier 2 is similar to the emission estimated by Tier 1. However, this reveals that the GHGs emission separated by local areas were a lot of different from Tier 1 and 2. The cause of difference between Tier 1 and Tier 2 was that Korea annual oil statistics utilized data from a fuel supplier. The data does not reflect the reality of the location of end user.

• 한국항공운항학회지
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• 제15권4호
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• pp.24-32
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• 2007

In this study, computational structural vibration analyses of a smart unmanned aerial vehicle (SUAV) with tilt-rotors due to dynamic hub loads have been conducted considering detailed supporting structures of installed equipments. Three-dimensional dynamic finite element model has been constructed for different fuel conditions and tilting angles corresponding to helicopter, transition and airplane flight modes. Practical computational procedure for modal transient response analysis is successfully established. Also, dynamic loads generated by rotating blades and wakes in the transient and forward flight conditions are calculated by unsteady computational fluid dynamics technique with sliding mesh concept. As the results of present study, transient structural displacements and accelerations of the vibration sensitive equipments are presented in detail. In addition, vibration characteristics of structures and installed equipments of which safe operation is normally limited by the vibration environment specifications are physically investigated for different flight conditions.

• 한국항공운항학회지
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• 제23권2호
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• pp.51-56
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• 2015

This paper presents the procedure of drag prediction for EAV-1, based on a numerical analysis correlated to an in-flight test. EAV-1, developed by Korea Aerospace Research Institute, is a small-sized UAV to test a hydrogen-fuel cell power system. The long-endurance test flight of 4.5 hours provides numerous in-flight data. The thrust and drag of EAV-1 during the flight test are estimated based on the wind-tunnel test results for EAV-1's propeller performance. In addition, the CFD analysis using a commercial Navier-Stokes code is carried out for the full-scale EAV-1. The computational result suggests that the initial CFD analysis substantially under-predicts the in-flight drag in that the discrepancy is up to 27.6%. Therefore, additional investigation for more accurate drag prediction is performed; the effect of propeller slipstream is included in the CFD analysis through "fan disk" modelling. Also, the additional drag from airplane trim and load factor that actually exists during the flight test in a circular path is considered. These supplemental analyses for drag prediction turn out to be effective since the drag discrepancy reduces to 2.3%.

• 한국항공운항학회지
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• 제18권4호
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• pp.30-37
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• 2010

This paper deals with attitude determination and parameter estimation problems for a lunar module. For this we first derive equations of motion for the lunar module by considering allocation locations (configurations) of reaction thruster and a reaction wheel assembly. The lunar module is assumed as a rigid body. In order to include the effect of fuel sloshing on the dynamics of the lunar module, we model it as a spherical pendulum for a simple analysis. For estimating angular rates and moment of inertia of the module, we employ an extended Kalman filter and the least mean square algorithms, respectively. Finally we construct a dynamical model for the lunar module by combining all these elements.

• 한국항공운항학회지
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• 제18권4호
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• pp.51-58
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• 2010

Recently, aerospace structures have lightweight trend in order to reduce the cost of fuel and system, Carbon Fiber Reinforced Plastic (CFRP) can give the ability to reduce weight at 20~50% as the substitution of metal alloy, and there are advantages such as high Non-rigid, specific strength and anti-corrosion, but it is difficult to prove its destruction properties due to heterogeneous structure and anisotropy. In this study we designed specimen, inducing distinguishing destructions of material (for example, matrix crack, fiber breakage, and delamination) by using the Carbon Fiber Reinforced Plastic (CFRP) which is used in a real aircraft, to apply acoustic emission technique to aerospace structures. And we gained data via tensile testing and acoustic emission technique, from which each fault signal was classified respectively by using AE parameters and waveform.

• 한국항공운항학회지
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• 제27권4호
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• pp.9-20
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• 2019

A military aircraft generally includes external stores such as fuel tanks or external arming, depending on the purpose of the operation. When a store is dropped from a military aircraft at high subsonic, transonic, or supersonic speeds, the aerodynamic forces and moments acting on the store can be sufficient to send the store back into contact with the aircraft. This can cause damage to the aircraft and endanger the life of the crew. In this study, time accurate computational fluid dynamics (CFD) with dynamic moving grid (moving and deformable mesh, MDM) technique has been used to accurately calculate store trajectories. For the verification of the present numerical approach, a wind tunnel test model for the wing-pylon-finned store configuration has been considered and analyzed. The comparison results for the ejected store trajectories between the present numerical analysis and the wind tunnel test data at the Mach number of 0.95 and 1.2 are presented. It is also importantly shown that the numerical parameter of MDM technique gives significant effect for the calculated store trajectory in the low-supersonic flow such as Mach 1.2.

• 한국항공운항학회지
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• 제29권1호
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• pp.1-8
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• 2021

Low level wind shear, which often occurs at Jeju International Airport, is a phenomenon that occurs when the topological location and topographical characteristics of Jeju Island are combined with weather characteristics. Low level wind shears, which are caused by rapid changes in wind direction and wind speed, pose a threat to aircraft safety and also cause abnormal situations, such as aircraft go-around, diversion, and cancellation. Many meteorological studies have been conducted on weather patterns, occurrence periods and frequency of low level wind shears. However, researches related to aircraft operations are limited where here we study the similarities and differences between strong southwest winds and bidirectional tailwind type low level wind shears based on aircraft go-around cases at Jeju International Airport. The results are expected to be used to enhance safety when operating to Jeju International Airport, which includes pilot training that reflects the characteristics generated by wind changes, pilot prior notification, providing pilots with latest trends, and increasing extra fuel.

• 한국항공운항학회지
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• 제30권4호
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• pp.184-190
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• 2022

In an attempt to apply hybrid rocket to the RATO (Rocket-Assisted Take Off) system, combustion characteristics of the non-circular grain were figured out in this study. Having larger combustion area, it was reconfirmed that the non-circular grain has advantages over regression rate, characteristic velocity and chamber pressure in which all gave higher values. Experiments were performed to understand the effect of the non-circular grain geometry over time where local regression rates depending on grain location were analyzed. It was found that the regression rate of five distinct locations were different. Partial conclusion driven was that these differences are due to the heat transfer caused by dissimilar distances from the flame layer. Besides, as combustion duration increased, the fuel port became circular, and the regression rate converged to a single value over the whole grain.