The mixture formation process in diesel engines consists of injection by which fuel is divided into small droplets, heating and evaporation of fuel, and mixing of fuel droplets and air in the combustion chamber. In other words, the shape and position of combustion chamber, fuel injection and air motion play a crucial role in the formation of mixture. Thus, many studies have been carried out in order to improve the mixing performance of fuel and air in the cylinder and improve combustion efficiency.

However, it was not fully taken into account that mass flow rate of intake air could be reduced when air swirl intensity was increased, while changing the inlet channel profile and the helical spiral shroud (HSS) shape of the intake valve. In addition, some attempts have been made to increase the air swirl and turbulent kinetic energy (TKE) by changing the shape of combustion chamber, but little study has been focused on improving the in-cylinder airflow characteristics by changing the eccentricity of combustion chamber.

Sin Mun Hak, a researcher at the Faculty of Mechanical Science and Technology, investigated the variation of in-cylinder swirl intensity and TKE depending on the eccentricity of combustion chamber. To this end, he conducted simulations of six series of eccentric combustion chambers.

The results showed that the air swirl intensity and turbulent kinetic energy in the combustion chamber increases as the y-axis eccentricity of combustion chamber is placed on the eccentric direction of injector and the x-axis eccentricity increases gradually from the centre of cylinder to the direction of injector. It was also shown that when the eccentricity is too large, there will be a drop in the fuel spray jet velocity or airflow separation in the region of mixture formation, resulting in a gradual increase in power and torque and then a decrease over a certain limit.

For more information, please refer to his paper “Effect of Combustion Chamber Eccentricity on In-Cylinder Air Flow and Combustion Process in Direct Injection Diesel Engine” in “Proceedings of KUTIC-2025”.

Nowadays, most spacecraft use solar array continuously facing the sun by solar array drive assembly (SADA) to increase the energy efficiency. However, in spacecraft with rotating flexible appendages, system dynamics and control are very difficult.

There has been an extensive study on suppressing the vibration caused by flexible appendages in such spacecraft across the world. What is attracting a great deal of attention is a method by the robust controller design. However, almost all robust control systems considered only fixed flexible appendages and neglected their rotation dynamics.

Sonu Kwang, a post-graduate student at the Faculty of Aerospace Engineering, proposed an attitude control method to suppress the vibration of flexible spacecraft with rotating solar array.

First, he simplified the singular dynamic model of spacecraft with rotation of flexible appendages by introducing extended state and modal identities into a non-singular state space-formed dynamic model. Based on this simplified dynamic model, he developed a PD-type static output feedback controller that essentially guarantees asymptotic stability and disturbance rejection. Then, he designed a compensator for the extended system including a static output feedback controller in order to ensure the stability of the control system under the influence of rotations of solar array, variation of natural frequency and damping coefficients, high-order flexible modes and measurement noises.

Through computer simulations, he found that the proposed attitude control system with and without compensators stabilized the attitude within 60s and suppressed flexible vibration.

You can find the details in his paper “Vibration Suppression for Flexible Spacecraft with Rotating Solar Array” in “Proceedings of KUTIC-2025”.

High accuracy and machining capability are the main requirements for metal cutting operations, and high cutting speed and feed rate increase the quality of machining parts, machining accuracy and metal removal per unit time. However, tool life and material removal rates are contradictory because of higher tool temperature, accelerated wear, shorter tool life, and lower machining efficiency with increasing tool replacement time and replacement rate.

Since both material removal rate and tool life are related to cutting conditions, it is necessary to choose appropriate cutting conditions.

Ham Kum Chol, a section head at the Faculty of Mechanical Science and Technology, developed an optimization model with maximum tool wear life at constant metal removal rate (efficiency) per unit time and proposed a method of optimizing the cutting conditions affecting tool life.

The tool wear model was constructed as a polynomial regression model from the simulation data using Deform3D finite element software, and the optimization solution was performed by MATLAB’s fmincon function.

The proposed method was applied to the cutting of high-temperature alloy Ti6A14V as a machining objective, which showed improved machining accuracy and machining time of center machine.

The proposed method can be applied to the selection of cutting conditions for maximizing tool life when machining various hard-working materials.

If more information is needed, please refer to his paper “Optimization of Cutting Parameters in Milling Based on Model of Tool Wear” in “Proceedings of KUTIC-2025”.