Earticle

In the present study, we conducted the research on the high efficiency propulsion system for the development of long-endurance UAV with an electric propulsion system. For the long endurance UAV, fair aerodynamic characteristics with the high efficiency of the propulsion system is required because the flight power and the duration time of the long-endurance UAV vary greatly depending on the efficiency of the propulsion system. Therefore, in this study, the tracking program which records the performance of motor, propeller was developed because of their wide variation in the efficiency depending on the using condition, and records from the existing flight test program were utilized to check the accuracy of the program we had developed. For the development of future long-endurance solar UAV, we confirmed the applied voltage of motor, the optimal rotation of propeller and the gear ratio of reduction gear in order to get the highest efficiency on the propulsion system at the optimal flying condition.

본 연구에서는 저속 운항 구간(6∼10노트)에서 가변피치 프로펠러(CPP)를 탑재한 군함의 수중 방사소음 급증 문제를 해결 하기 위해 Hybrid Controllable Pitch Propeller (HCPP)시스템을 제안한다. 기존 CPP 시스템에서는 베어링 윤활을 위한 최소 회전수를 유지하면서 속도 저감을 위해 피치를 감소시켜야 하는 운용상의 충돌로 인해, 프로펠러 루트 부근에서 부분 피 치 공동(cavitation)이 발생한다. 선행 연구에 따르면 8노트 운항 시 소음이 최대 20 dB까지 증가하는 것으로 보고되어, 저속 운용 성능에 제한이 발생하고 있다. 제안된 HCPP는 저속 구간에서 피치를 100%로 고정하고 회전수(RPM) 제어를 통해 속도 를 조절하는 이중 운용 모드(dual-mode operation)개념을 도입하였다. 또한, 강제 윤활 시스템(forced lubrication system)을 적용하여 25∼40 RPM 구간에서도 안정적인 윤활을 보장함으로써 공동 발생을 근본적으로 억제하고, 15∼20 dB 의 소음 저감 효과를 달성하였다. 이와 함께 추진 효율이 향상되고 추력 변동이 감소하는 효과도 확인되었다. HCPP는 기존 CPP 하드웨어를 유지한 채 제어 로직과 윤활 시스템의 개선만으로 구현이 가능하므로 경제성이 높다. 이를 통해 0∼15노트 전 구간에서 정숙 운항(quiet operation)이 가능해지며, 함정의 대잠전(ASW) 운용 능력을 크게 향상시킬 수 있다.

This study proposes a Hybrid Controllable Pitch Propeller (HCPP)system to mitigate the surge in underwater radiated noise observed in naval vessels equipped with conventional CPPs during low-speed operations (6–10 knots). In typical CPP systems, the trade-off between maintaining a minimum RPM for bearing lubrication and reducing propeller pitch for speed control often leads to partial pitch cavitationnear the propeller root. Previous investigations have reported noise increases of up to 20 dB at 8 knots, thereby constraining operational performance. The proposed HCPP introduces a dual-mode operation concept, fixing the pitch at 100% and regulating speed through RPM variation in low-speed ranges. By incorporating a forced lubrication systemthat ensures stable lubrication at 25–40 RPM, the system effectively suppresses cavitation and achieves a 15–20 dB reduction in underwater noise. Moreover, it enhances propulsion efficiency and minimizes thrust fluctuations. The HCPP concept can be realized by upgrading control logic and lubrication systems while retaining existing CPP hardware, offering excellent economic feasibility. This technology enables quiet operation across the entire 0–15 knot range, significantly improving the vessel’s anti-submarine warfare (ASW) capability.

This paper illustrates recent advancements relative to a non-conventional propulsion system for boats and is based on two previous papers of the author presented at a conference (see Muscia, 2015a,b). The system does not consider propellers and utilizes the vibration generated by two or more pairs of counter rotating masses. The resultant of the centrifugal forces applies an alternate thrust to the hull that oscillates forward and backward along the longitudinal axis of the boat. The different hydrodynamic drag forces that oppose to the oscillation produce a prevalently forward motion of the vessel. The vibration that causes the motion can be suitably defined to maximize the forward displacement and the efficiency propulsion of the system. This result is obtained by using elliptical gears to rotate the counter rotating masses. The computation of the propulsion efficiency is based on a suitable physical mathematical model. Correlations between numerical experiments on models and possible full scale application are discussed. Some remarks in relation to practical applications and critical issues of the propulsive solution are illustrated. The results have been obtained with reference to a CAD model of a real boat already manufactured whose length is approximately equal to 13 m.

In order to investigate propulsion efficiency and cavitation characteristics for expanded area ratio variation of the 8800TEU class container propeller, a series of performance tests were conducted at Large Cavitation Tunnel (LCT) and Towing Tank (TT) in KRISO. The cavitation test of the existing propellers (KP1029 & KP1030) was conducted using FRP model ship in LCT. On the basis of LCT test results, it was required to design propeller with better propulsion efficiency and cavitation performance. Two propellers (KP1171 & KP1172) with decreased expanded area ratio were designed on the basis of KP1029 propeller. The new design propellers showed higher efficiency than KP1029 and reasonable cavitation performance. In the future, they will be applied as the standard propeller for the propeller design of the large container ship. Through the performance test and prediction results for the new design propellers, it is thought that high-load propeller with better propulsion efficiency and cavitation performance will be developed constantly.

In order to investigate propulsion efficiency and cavitation characteristics for expanded area ratio variation of the 8800TEU class container propeller, a series of performance tests were conducted at Large Cavitation Tunnel (LCT) and Towing Tank (TT) in KRISO. The cavitation test of the existing propellers (KP1029 & KP1030) was conducted using FRP model ship in LCT. On the basis of LCT test results, it was required to design propeller with better propulsion efficiency and cavitation performance. Two propellers (KP1171 & KP1172) with decreased expanded area ratio were designed on the basis of KP1029 propeller. The new design propellers showed higher efficiency than KP1029 and reasonable cavitation performance. In the future, they will be applied as the standard propeller for the propeller design of the large container ship. Through the performance test and prediction results for the new design propellers, it is thought that high-load propeller with better propulsion efficiency and cavitation performance will be developed constantly.

This paper is to compare by numerical analysis the flow characteristics and propulsion performance of stern with the shape change of K-duct, a pre-swirl duct developed by Korea Research Institute of Ships & Ocean Engineering (KRISO). First, the characteristics of the propeller and the resistance and self-propulsion before and after the attachment of the K-duct to the ship were verified and the validity of the calculation method was confirmed by comparing this result with the model test results. After that, resistance and self-propulsion calculations were performed by the same numerical method when the K-duct was changed into five different shapes. The efficiency of the other five cases was compared using the delivery horsepower in the model scale and the flow characteristics of the stern were analyzed as the velocity and pressure distributions in the area between the duct end and the propeller plane. For the computation, STAR-CCM +, a general-purpose flow analysis program, was used and the Reynolds Averaged Navier-Stokes (RANS) equations were applied. Rigid Body Motion (RBM) method was used for the propeller rotating motion and SST k-ω turbulence model was applied for the turbulence model. As a result, the tangential velocity of the propeller inflow changed according to the position angle change of the stator, and the pressure of the propeller hub and the cap changes. This regulated the propeller hub vortex. It was confirmed that the vortex of the portion where the fixed blade and the duct meet was reduced by blunt change.

This paper provides numerical results for the estimation of the efficiency of KRISO energy saving devices in the design stage. A finite volume method is used to solve Reynolds averaged Navier-Stokes (RANS) equations, where the SST k-$\omega$ model is selected for turbulence closure. The propeller rotating motion is determined using a rigid body motion (RBM) scheme, which is called a sliding mesh technique. The numerical analysis focuses on predicting the power reduction by the designed KRISO devices (K-DUCT) under a self-propulsion condition. The present numerical results show good agreement with the available experimental data. Finally, it is concluded that CFD can be a useful method, along with model tests, for assessing the performance of energy saving devices for propulsion efficiency improvement.

본 연구는 실제 선박 운항 데이터를 기반으로 항해 조건에 따른 기관 부하 및 배출 특성의 변화를 분석하고자 하였다. 이를 위해 실습선 백경호에서 수집한 항해 데이터(선속, 상대풍 방향 및 속도)와 기관 데이터(엔진 부하, NOx, SOx 배출량)를 통합하여 고해상도 시계열 데이터셋을 구축하였다. 조건 구간별 곡선 적합(curve fitting)과 피어슨 상관분석을 통해 변수 간 정량적 관계를 평가하였다. 분석 결과, 선속과 기관 부하 간에는 높은 양의 상관관계(r ≈0.86, R² ≈ 0.74)가 확인되었으며, 전방풍 조건에서는 선속 증가에 따라 Load와 NOx 배출이 급격히 증가하는 경향을 보였다. 반면, 후방풍 조건에서는 비교적 일정한 기관 응답이 유지되었으며, SOx는 전체적으로 불규칙한 분포를 나타냈다. 이러한 결과는 외력 조건에 따라 기관의 연료 소모 및 배출 반응이 구조적으로 다르게 나타남을 보여주며, 단순 속도 제어 중심의 운항 전략보다는 조건 기반의 대응 전략이 필요함을 시사한다. 본 연구는 실측 데이터 기반의 조건 반응 해석을 통해 선박 운항 효율 개선과 온실가스 저감을 위한 운항 전략 수립에 기초자료를 제공하며, 향후 다변량 예측 모델 및 실시간 최적화 알고리즘 개발의 기반이 될 수 있다.

This study analyzed variations in engine load and emission characteristics under different navigational conditions using actual ship operation data. To achieve this, we constructed a high-resolution time-series dataset by integrating navigational data (ship speed, relative wind direction, and speed) with engine data (engine load, NOx, and SOx emissions) collected from the training ship Baekkyung-ho. We evaluated quantitative relationships among the variables through curve fitting by condition segments and Pearson correlation analysis. Our results revealed a strong positive correlation between ship speed and engine load (r = 0.859, R² ≈ 0.74). Under headwind conditions, both engine load and NOx emissions increased significantly with speed, while under tailwind conditions, the engine response remained relatively stable, with SOx emissions displaying an irregular distribution. These findings indicate that the fuel consumption and emission responses of the engine vary significantly based on external forces, suggesting that a condition-based operational strategy is more effective than a simple speed-control approach. By providing insights based on actual measurements, this study offers essential data for developing operational strategies aimed at improving ship fuel efficiency and reducing greenhouse gas emissions. Additionally, it can serve as a foundation for creating multivariate predictive models and real-time optimization algorithms in the future.

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO₂ emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author's previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO2 emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author’s previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.

본 논문에서는 현재 운행되고 있는 선형 유도전동기의 슬립주파수 고정 방식이 아닌 선형 유도전동기를 이용한 자기부상열차의 슬립주파수와 수직력 및 추진력과의 관계를 이용, 열차의 가감속시 운행패턴에 따라 운행 중 슬립주파수가 가변할 수 있는 슬립주파수 가변패턴을 형성, 선형유도전동기 자기부상시스템에서의 에너지 효율향상 가능성을 검증하였다. 슬립주파수와 수직력, 추진력과의 관계를 이용 슬립주파수 일정 실효치전류제어 알고리즘과 슬립주파수 일정 벡터제어 알고리즘을 사용하여 운전조건과 슬립주파수를 변경하며 운전조건에 따른 가장 효율적인 슬립주파수의 패턴을 형성하였다. 이 후 모의시험과 실차를 이용한 실험을 통해 알고리즘에 대한 정당성과 실제 효율의 증가를 통해 타당성을 검증하였다. 앞선 두 가지 알고리즘을 통해 열차부상에 영향을 미치지 않는 범위의 수직력을 가지는 범위내에서 슬립주파수를 가변 운전 조건에 따른 최적의 슬립주파수에 대한 정보를 기반으로 운행 중 가변하는 슬립주파수를 자동열차운전(ATO)시스템에 적용 모의실험을 통해 그 적용가능성과 효율을 검증하였다.

최근 대두되는 선박배기가스 저감 등의 환경정책으로 인하여 에너지의 효율적 이용에 관심이 증가하고 있다. 본 논문에서는 함정의 에너지 효율 향상을 위하여 사용 부하에 따라 해수펌프를 제어하는 고효율 해수냉각시스템을 제안한다. 본 논문에서는 제안하는 시스템의 효과를 알아보기 위하여 추진 디젤기관의 냉각시스템을 모델링 하고 함정 운항특성을 고려한 시뮬레이션을 수행하였다. 시뮬레이션 결과 제안한 고효율 해수냉각시스템이 기존 해수냉각시스템에 비하여 약 53%의 에너지 절감효과가 있었다. 본 연구 결과는 향후 함정 추진 디젤기관의 해수냉각시스템의 성능 향상에 유용한 자료로 활용될 수 있다.

Recently, there has been increasing interest in the efficient use of energy due to policies related to the reduction of greenhouse gas. This paper suggests a highly efficient sea water cooling system for the load-dependent control of a seawater pump depending on the load, to improve energy efficiency of the warship. This study models the propulsion diesel engine and simulation reflecting the characteristics of the warship operation state that checked the performance of high efficiency sea water cooling system. The simulation results revealed the cooling system of high efficiency with energy savings of approximately 53% compared to the existing cooling systems. These results can be used to improve the performance of the cooling system of the warship propulsion diesel engine in the future.