• 한국추진공학회지
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• 제13권3호
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• pp.1-8
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• 2009

본 연구에서는 비행 중 PW4000 엔진의 축류압축기에서 발생된 서지 현상이 엔진성능에 미치는 영향에 대하여 연구하였다. 이륙조건에서는 항공기의 엔진성능이 급격히 변화하므로 순항할 때 보다 자주 서지가 발생할 수 있다고 판단된다. EPR은 서지 발생과 동시에 급격히 저하하는 것으로 나타나 민감도가 가장 컸다. 엔진 rpm과 Wf도 EPR과 거의 동일한 경향이었으며, Vibration 변화는 크지 않았으나 N1 Vibration 변화가 상대적으로 크게 나타났다. 따라서 비행 중 EPR, N1 rpm, Wf 값이 급격히 저하되고 EGT가 비선형적으로 상승하는 상태를 서지 발생 감지에 적용할 수 있을 것으로 판단된다.

• 한국항공운항학회지
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• 제24권4호
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• pp.12-19
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• 2016

In the case of hard problems to find solutions or complx combination problems, there are various optimization algorithms that are used to solve the problem. Among these optimization algorithms, the representative of the optimization algorithm created by imitating the behavior patterns of the organism is the PSO (Particle Swarm Optimization) algorithm. Since the PSO algorithm is easily implemented, and has superior performance, the PSO algorithm has been used in many fields, and has been applied. In particular, PSO-SAPARB (PSO with Swarm Arrangement, Parameter Adjustment and Reflective Boundary) algorithm is an advanced PSO algorithm created to complement the shortcomings of PSO algorithm. In this paper, this PSO-SAPARB algorithm was applied to the longitudinal controller design of a VTOL (Vertical Take-Off and Landing) aircraft that has the advantages of fixed-wing aircraft and rotorcraft among drones which has attracted attention in the field of UAVs. Also, through the introduction and performance of the Korean SBAS (Satellite Based Augmentation System) named KASS (Korea Augmentation Satellite System) which is being developed currently, this paper deals with the availability of algorithm such as the PSO-SAPARB.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.236-239
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• 2008

본 연구에서는 PW4000 엔진의 축류압축기 서지 발생이 엔진성능에 미치는 영향에 대하여 연구하였다. EPR은 서지 발생과 동시에 급격히 저하하는 것으로 나타나 민감도가 가장 큰 파라미터였다. N1 rpm과 N2 rpm도 EPR과 거의 동일한 경향으로 감소하였으며, Vibration 변화는 크지 않았으나 N1 Vibration 변화가 상대적으로 크게 나타났다. 따라서 비행중 EPR, N1 rpm, Wf 값이 급격히 저하되고 EGT가 비선형적으로 상승하는 상태로서 서지 발생을 감지할 수 있을 것으로 판단된다.

• 한국전산유체공학회지
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• 제18권4호
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• pp.41-46
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• 2013

The selection of the optimal position of the flap was performed in order to improve the aerodynamic performance during the take-off and landing processes of aircraft. For this, the existing airfoils of the main wing and flap are selected as the baseline model and the lift coefficients (cl) according to angle of attacks (AOA) were calculated with the change of the position of flap airfoil. The objective function was defined as the consideration of the maximum cl, lift to drag ratio and cl at certain AOA. Then, at 121 experimental points within $20mm{\times}20mm$ domain, two dimensional flow simulations with Spalart-Allmaras turbulence model were performed concerning the AOA from 0 to 15 degree. If the optimal position was located at the domain boundary, the domain moved to the optimal position. These processes were iterated until the position was included in the inside of the domain. From these processes, the flow separation at low AOA was removed and cl increased linearly comparing with that of the baseline model.

• Ocean Systems Engineering
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• 제12권1호
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• pp.23-38
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• 2022

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

• 한국추진공학회지
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• 제2권2호
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• pp.47-55
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• 1998

중형항공기용 터보팬엔진의 설계점, 탈설계점에 대한 정상상태 및 천이상태 성능해석을 수행하였다. 정상상태 성능해석은 설계점으로 선정한 지상최대추력조건과 탈설계점으로 선정한 최대상승조건과 순항조건에서 수행하였으며 부분부하 성능해석 결과 저압압축기 회전속도 90％RPM에서 가장 연료소모율이 적어 경제적임을 확인하였다. 천이상태 성능해석은 각각의 비행조건에서 연료의 Step증가, Ramp증가, Ramp감소, Step 증가 후 Ramp 감소의 경우에 대하여 수행하였다. 천이상태의 성능해석을 위해서는 압축기와 터빈의 일에 대한 조합이 필요한데, 일의 조합방정식에 포함된 잉여 토오크의 적분에는 Modified Euler Method를 적용하였다. 천이상태 성능해석 결과, 모든 비행조건에서 Step 및 Ramp 증가의 경우 고압압축기의 터빈입구온도가 제한온도를 초과하며, 최대상승조건에서 연료를 Step 또는 5.5초 이내의 Ramp 증가시킬 경우 고압압축기에서 실속이 발생함을 확인하였다.

• Journal of Biosystems Engineering
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• 제39권3호
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• pp.158-165
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• 2014

Purpose: The objective of this paper was to compare test standards regarding the performance and safety of agricultural tractors to identify the differences in test conditions, measurement tolerances, and test procedures. Based on the comparison, some recommendations were proposed for possible revisions or improvements to current tractor test standards. Methods: The test standards and codes of major standards development organizations (SDOs), such as the Organization for Economic Cooperation and Development (OECD), the International Organization for Standardization (ISO), the American Society of Agricultural and Biological Engineers (ASABE), EC type approval, and the board of actions of the Nebraska Tractor Test Laboratories (NTTL), were selected and analyzed. Comparison of the test standards: The ISO provides references for fuel and lubricants for tractor tests, and the OECD provides additional measurements for calculating fuel consumption characteristics during the power take-off (PTO) tests. The ISO, EC type approval, and the ASABE provide PTO protective device and the safety requirements. During drawbar power tests, seven transmission ratios are selected for fully automatic transmissions, according to the OECD. In case of hydraulic lift tests, ISO 789-2 and OECD Code 2 advise the use of a static lift force, while SAE J283 advises the use of additional dynamic lift capacity tests for a better representation of in-field operations. The OECD, the ISO, and EC type approval determine the seat index point (SIP), whereas the ASABE determines the seat reference point (SRP) for roll-over protective structure (ROPS) tests. Diversified measurement tolerances were among the braking performance test standards. The European Union (EU) has developed daily limits for vibration exposures with adaptations from ISO 2631-1. Electromagnetic compatibility evaluations are emerging of high-efficiency tractors due to the long-term conformance to electromagnetic emissions and interferences. Comparisons of tractor test standards discussed in this paper are expected to provide useful information for tractor manufacturers and standards development personnel to improve the performance and safety test standards of tractors.

• 한국항공우주학회지
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• 제33권2호
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• pp.22-31
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• 2005

본 연구에서는 회전익 항공기의 수직 이/착륙 성능과 고정익 항공기의 고속/고효율 순항 비행 성능을 모두 가지는 Canard Rotor/Wing 항공기 최적 형상설계를 수행하였다. CRW 항공기의 특징인 로터/날개 가변 방식과 로터 회전 시 팁 제트를 통하여 회전력을 얻는 점 때문에 기존의 회전익 또는 고정익 사이징 프로그램만으로는 바로 적용이 어렵고 Reaction Driven 로터에 대한 해석 모듈의 추가와 회전익/고정익 비행 모드 해석이 혼합되어야 한다. 따라서 기존의 사이징 프로그램을 바탕으로 로터 성능, 덕트 유동, 엔진 유동 해석 코드를 연결하여 Reaction Driven 로터 성능 해석이 가능하게 하였으며, 비행체 외형상 특징과 임무별 비행특징이 반영되도록 사이징 프로그램을 개발하였다. 1500 lbs급 소형 무인기에 대하여 비행체 사이징을 수행하고 성능에 크게 영향을 미치는 설계변수를 파악하여 최적화 문제를 구성하였고 전역적 최적화 기법을 이용하여 최소 중량을 가지는 CRW 항공기의 최적형상을 도출하였다.

• Journal of Biosystems Engineering
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• 제39권1호
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• 한국추진공학회지
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• 제19권6호
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• pp.10-18
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• 2015

로켓 기반 공기흡입추진(RBCC : Rocket Based Combined Cycle) 엔진이 적용된 재사용 발사체의 요구 중량 및 성능을 분석하고 예측하였다. RBCC 엔진을 위해 개발한 엔진 모델과 비행체 궤적 모델을 통합하여 RBCC 기반 재사용 발사체의 궤적 및 성능계산 모델을 개발하였으며, 기존 논문의 결과와 비교함으로써 검증하였다. 개발된 모델과 기존 논문을 바탕으로 총 이륙중량 15톤의 재사용 발사체에 대한 무게분석과 엔진의 요구 조건을 도출하였으며, 엔진의 모드 전환 마하수 변화 등에 따른 비행체의 추진제 요구량 변화를 분석하였다.