본 연구에서는 지그재그 배열로 배치된 리브 터뷸레이터가 적용된 내부 냉각 채널에서 리브 높이와 레이놀즈 수가 열전달 특성에 미치는 영향을 실험적으로 분석하였다. 실험 결과, 레이놀즈 수 증가에 따라 너셀 수가 증가하며 대류 열전달 성능이 향상되는 경향이 확인되었다. 또한, 리브 높이가 증가할수록 난류 형성이 촉진되어 열전달 성능이 개선되었으나, 동시에 압력 강하도 증가하는 것이 관찰되었다. 따라서 냉각 성능 향상과 압력 손실 최소화를 균형적으로 고려한 설계가 필요함을 확인하였다. 본 연구의 결과는 가스터빈 내부 냉각 채널의 설계 최적화를 위한 기초 데이터로 활용될 수 있으며, 향후 열관리 및 성능 개선을 위한 중요한 정보를 제공할 것으로 기대된다.

In the present study, various tangential angles of effusion hole configurations were investigated to evaluate their effects on the cooling performance and combustion characteristics of a can-type combustor model. Numerical simulations were conducted using the Reynolds stress model for turbulence modeling and the steady flamelet approach within the non-premixed combustion framework to model methane combustion. The results indicated that the effusion hole configuration with a tangential angle of 0° enhanced the liner wall cooling effectiveness by approximately 340.28%. This configuration also blocked 77.71% of the absorbed radiation flux, resulting in a 47.81% reduction in wall temperature. Furthermore, the lowest pattern factor value was observed when the liner wall was designed with effusion holes at a tangential angle of ±30°, compared to other configurations. Similarly, injecting cooling air into the combusted region through effusion holes at a tangential angle of 0° led to an approximate 20.23% reduction in thermal NOx emissions.

In the modern gas turbine, elevating the turbine inlet temperature is a key strategy to improve thermal efficiency and power performance. However, this temperature imposes significant thermal stress on the turbine component, leading to issues such as creep, thermal fatigue, oxidation, and corrosion which adversely affect the durability. To address these challenges various cooling techniques have been developed, including the use of internal rib turbulators and conductive coolant materials to ensure efficient thermal management. This study explores the impact of mist/steam flow and mist particle size within a cooling channel featuring an inclined rib turbulator. The findings reveal that introducing mist at specific mass ratios synergistically enhances secondary flow velocities. Smaller particles significantly improve heat transfer efficiency due to their rapid evaporation. Specifically, at a mist/steam mass ratio of 10% and a mist particle size of 10 μm, the enhancement values for Nusselt number ratio and thermal performance factors are 9.76% and 4.45%, respectively. Therefore, a 10 μm particle size is optimal for achieving the highest heat transfer and cooling efficiency within varying mist/steam mass ratios. These findings indicate significant potential for improving gas turbine efficiency and longevity, thereby reducing operational costs and maintenance frequency in the industry.

본 연구에서는 지그재그 배열로 배치된 리브 터뷸레이터가 적용된 내부 냉각 채널에서 리브 높이와 레이놀즈 수가 열전달 특성에 미치는 영향을 실험적으로 분석하였다. 실험 결과, 레이놀즈 수 증가에 따라 너셀 수가 증가하며 대류 열전달 성능이 향상되는 경향이 확인되었다. 또한, 리브 높이가 증가할수록 난류 형성이 촉진되어 열전달 성능이 개선되었으나, 동시에 압력 강하도 증가하는 것이 관찰되었다. 따라서 냉각 성능 향상과 압력 손실 최소화를 균형적으로 고려한 설계가 필요함을 확인하였다. 본 연구의 결과는 가스터빈 내부 냉각 채널의 설계 최적화를 위한 기초 데이터로 활용될 수 있으며, 향후 열관리 및 성능 개선을 위한 중요한 정보를 제공할 것으로 기대된다.

In the present study, various tangential angles of effusion hole configurations were investigated to evaluate their effects on the cooling performance and combustion characteristics of a can-type combustor model. Numerical simulations were conducted using the Reynolds stress model for turbulence modeling and the steady flamelet approach within the non-premixed combustion framework to model methane combustion. The results indicated that the effusion hole configuration with a tangential angle of 0° enhanced the liner wall cooling effectiveness by approximately 340.28%. This configuration also blocked 77.71% of the absorbed radiation flux, resulting in a 47.81% reduction in wall temperature. Furthermore, the lowest pattern factor value was observed when the liner wall was designed with effusion holes at a tangential angle of ±30°, compared to other configurations. Similarly, injecting cooling air into the combusted region through effusion holes at a tangential angle of 0° led to an approximate 20.23% reduction in thermal NOx emissions.

In the modern gas turbine, elevating the turbine inlet temperature is a key strategy to improve thermal efficiency and power performance. However, this temperature imposes significant thermal stress on the turbine component, leading to issues such as creep, thermal fatigue, oxidation, and corrosion which adversely affect the durability. To address these challenges various cooling techniques have been developed, including the use of internal rib turbulators and conductive coolant materials to ensure efficient thermal management. This study explores the impact of mist/steam flow and mist particle size within a cooling channel featuring an inclined rib turbulator. The findings reveal that introducing mist at specific mass ratios synergistically enhances secondary flow velocities. Smaller particles significantly improve heat transfer efficiency due to their rapid evaporation. Specifically, at a mist/steam mass ratio of 10% and a mist particle size of 10 μm, the enhancement values for Nusselt number ratio and thermal performance factors are 9.76% and 4.45%, respectively. Therefore, a 10 μm particle size is optimal for achieving the highest heat transfer and cooling efficiency within varying mist/steam mass ratios. These findings indicate significant potential for improving gas turbine efficiency and longevity, thereby reducing operational costs and maintenance frequency in the industry.

This study examines the charge reduction characteristics of charged particles using a neutralizer to prevent accidents from electrostatic discharge and enhance process efficiency. The research measures the number of charges, elimination efficiency, and penetration rate under various voltage polarity conditions with a DC-type bipolar electrostatic eliminator. The results indicate that electrostatic neutralization is most effective under negative high voltage (-HV) conditions, while the mesh penetration rate increases and charge accumulation occurs under positive high voltage (+HV) conditions. Furthermore, partial charge neutralization is observed under both positive and negative high voltage (±HV) conditions due to the sequential emission of positive and negative ions. This study quantifies the mitigation of electrostatic charge using a neutralizer, offering insights for optimizing filtration systems and improving process stability. Future research will refine electrostatic control mechanisms by considering additional parameters such as particle size, material properties, and flow conditions.

Propulsion motors are vital components in marine propulsion systems and industrial machinery, where high torque and operational reliability are paramount. During operation, high-power propulsion motors generate considerable heat, which can adversely affect efficiency, durability, and stability. Therefore, an effective thermal management system is necessary to maintain optimal performance and ensure long-term reliability. Cooling technologies, such as water jackets, are commonly employed to regulate temperature distribution, prevent localized overheating, and preserve insulation integrity under high-power conditions. This paper examines the cooling performance of water jackets for high-power propulsion motors through numerical analysis. We evaluated the effects of three different cooling pipe locations and varying coolant flow rates on thermal balance and cooling efficiency. Additionally, we analyzed temperature variations in the windings and key heat-generating components to determine if a specific cooling flow rate and pipe configuration can effectively keep the winding insulation (Class H) within its 180oC limit. The findings of this study highlight the significance of optimized cooling system design and contribute to the development of efficient thermal management technologies, ultimately enhancing motor reliability, operational stability, and energy efficiency.

This study presents a dual-impeller air-cooled heat exchanger aimed at improving thermal management in electro-optical tracking systems operating under high power density. Two geometric modifications were introduced to enhance flow characteristics and heat transfer performance: the curvature of the center plate and the integration of a pin-fin structure at the outlet. Through numerical simulation, the improved model demonstrated more efficient internal flow compared to the original model, achieved through enhanced inflow characteristics and reduced flow separation. The pin-fin structures induced localized turbulence and recirculation zones, contributing to an increased thermal exchange surface area and longer effective heat transfer time. Consequently, the outlet temperature of the internal system decreased by an average of 1.4°C across various rotational speeds, resulting in a 5.9% increase in heat exchanger efficiency compared to the original model. Overall, this study shows that structural enhancements in heat exchanger design can significantly improve the cooling performance of high-power electronic systems, suggesting practical applicability for advanced thermal management solutions.

A steam turbine is a well-known energy conversion device that transforms high pressure steam energy into the mechanical work. This mechanical work is generally used for electricity generation or to operate mechanical machinery. In this study, we developed the three-dimensional airfoils and flow paths for micro scale axial steam turbine blades adopting both one dimensional and two dimensional design techniques. The steam turbine has been designed with the objective of achieving an output power exceeding 3.5 MW and an efficiency nearly the 50%. The averaged radius of the steam turbine was set at 262.75 mm and the rotational speed of the the blades was targeted at 6000 RPM. The simulation was conducted under varying inlet operating pressure while maintaining a constant temperature. The numerical investigation result indicated that the designed steam turbine achieved a output power of approximately 3.9 MW and an efficiency of 48.45% at an operating pressure of at 47 bar.

A numerical study was conducted to investigate the effects of variations in cooling hole shape on film cooling performance. The injection angle and shapes of the cooling holes were designed with 30° injection angle, cylindrical shape and swirling hole shape with various pitch configurations. Film cooling effectiveness was compared under blowing ratios of 0.5, 1 and 1.5. The flow sturctures and characteristics were analyzed. The results show that as blowing ratios increases, swirling flow promotes coolant reattachment to the surface and mitigates lift-off tendencies, thereby improving film cooling effectiveness. And swirl strength has a significant influence on film cooling performance. Compared to conventional cylindrical holes, pitch 10 swirling hole shape improves in area-averaged cooling effectiveness by 4.36% and 9.52% at blowing ratios of 1 and 1.5, respectively.