• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.2
• /
• pp.166-174
• /
• 2009

The liquid column trajectory and column breakup length characteristics have been experimentally studied in angled jets injected into subsonic crossflow. Pulsed shadowgraph photography and Planar Liquid Laser Induced Fluorescence measurements were used to determine the angled effects. And the main objectives of this research are to get a empirical formula of liquid column trajectory and breakup length with below the $90^{\circ}$ degree injection angle conditions, and were compared with previous results. It was also found that the empirical formula, which reversed injection conditions of air stream. As the result, This has been shown that liquid column trajectories and column breakup length were spatially dependent on various injection angle, normalized injector exit diameter, air-stream and fuel injection velocity. Furthermore, the empirical formula of liquid column trajectories and breakup length has been some different of drag coefficient results between normal angled injection and reversed injection in subsonic crossflow.

• Journal of the Korean Institute of Gas
• /
• v.19 no.6
• /
• pp.22-27
• /
• 2015

Hydrogen features highest energy density per mass and is expected to be desirable as a fuel of HALE(High altitude long endurance) UAV(Unmanned aerial vehicle). A reciprocating internal combustion engine is known to be a reliable and economic power source for this kind of UAV. Therefore, the combination of hydrogen and engine is worth of doing research. Test bench with 2.4L Spark-Ignited engine was prepared for the experiment in which start and combustion characteristics at idle condition were examined in this study. Stable hydrogen supply system and a universal ECU(Engine control unit) were also utilized for the test engine. Equivalence ratio and spark timings at idle operation were investigated and compared to the data of gasoline engine. The results will be a starting point for full-scale research of hydrogen engine for HALE UAV.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.12
• /
• pp.1489-1495
• /
• 2013

High-pressure flows are ubiquitous in many industrial fields. A representative application is fuel injection using a common-rail control system in diesel engines, where the injection pressure in the injector exceeds 1000 bar. In high-speed injection, the fluid injected through the nozzle undergoes breakup owing to the interaction with the ambient gas. The breakup process influences mixture formation, which in turn influences combustion in diesel engines. Therefore, it is very important to analyze the breakup process of fuel spray. The Reitz and Diwakar model and cascade atomization and breakup (CAB) model were used in this study as sub-models for the numerical analysis of the breakup process of fuel spray. This study aims to precisely analyze the breakup process of spray and to investigate the breakup frequency of the injected fuel. Consequently, it proposes a suitable sub-model for analyzing the breakup process of a diesel spray by using CFX, a commercial CFD program.

• Journal of the Korea Convergence Society
• /
• v.10 no.11
• /
• pp.327-333
• /
• 2019

The Fuel-cut driving is started when the acceleration pedal released with transmission gear engaged. Fuel economy of the vehicle improves by active fuel-cut driving. A deep-learning technique is proposed to predict fuel-cut driving with vehicle speed, acceleration and road gradient data in the study. It's 3~10 of hidden layers and 10~20 of variables and is applied to the 9600 data obtained in the test driving of a vehicle in the road of 12km. Its accuracy is about 84.5% with 10 variables, 7 hidden layers and Relu as activation function. Its error is regarded from the fact that the change rate of input data is higher than the rate of fuel consumption data. Therefore the accuracy can be better by the normalizing process of input data. It's unnecessary to get the signal of vehicle injector or OBD, and a deep-learning technique applied to the data to be got easily, like GPS. It can contribute to eco-drive for the computing time small.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.375-379
• /
• 2008

In this paper, a 10N class liquid propellant rocket utilizing a dissolving reaction of hydrogen peroxide is constructed and tested. Through a series of designs, seven orifices with a diameter of 200 ${\mu}m$ and a nozzle with a neck of 2.5mm in diameter and area ratio of 2.56 were made. The platinum coated on Isolite was used for catalyst. 90wt% peroxide pressed at 20 bar by nitrogen gas was used for performance evaluation. The length of the catalyst bed and the load of platinum was taken as the parameters for this experiment. For the catalyst support length of 4cm loaded on 5wt% platinum, satisfactory $c^*$ efficiency and stable thrust was observed. The light weight body of the rocket was composed of aluminum. Rocket rose about 10m with relatively constant velocity in launching test.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.3
• /
• pp.204-211
• /
• 2019

The analysis on two-phase flow in a Lean Direct Injection(LDI) combustor has been investigated. Linearized Instability Sheet Atomization(LISA) and Aerodynamically Progressed Taylor Analogy Breakup(APTAB) breakup models are applied to simulate the droplet breakup process in hollow-cone spray. Breakup model is validated by comparing penetration length and Sauter Mean Diameter(SMD) of the experiment and simulation. In the LDI combustor, Precessing Vortex Core(PVC) is developed by swirling flow and most droplets are atomized along the PVC. It has been confirmed that all droplets have Stokes number less than 1.0.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.1-9
• /
• 2020

Using kerosene and liquid oxygen, 1.5-tonf class liquid-liquid pintle injector with rectangular two-row orifice was designed and manufactured. The combustion test of the pintle injector was carried out to verify the combustion performance and combustion stability under a supercritical condition which is the actual operation condition of the liquid rocket engine. The combustion test result showed that the pintle tip was damaged by the high temperature combustion gas in the high-mixed ratio recirculation zone of the combustion chamber. To solve this problem, the insert nozzle was installed in the pintle injector to increase cooling performance at the pintle tip. As a result of the hot firing test, installation of the insert nozzle, AR and BF had a great effect on pintle tip cooling performance.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.4
• /
• pp.53-58
• /
• 2021

Based on surrogate model, a hydrocarbon mixture was analyzed by visualizing the impinging break up mechanism in subcritical and supercritical conditions. Decane and methylcyclohexane with different critical pressures and temperatures were selected as experimental fluids. The impinging injector was installed inside the chamber, and the spray was visualized through a speed camera in subcritical and supercritical conditions. The injection condition of the mixture and chamber was kept constant at Pr(P/P_c) = 1, and Tr(T/T_c) was increased from 0.48 to 1.02. As Tr increased, the spray angle increased, and the sheet length decreased as the properties of the mixture reached each critical point. In addition, when the mixture approached the near critical point, it was shown that the change in density gradient was largely observed out of the impinging break up mechanism.

• Journal of the Korean Institute of Gas
• /
• v.27 no.3
• /
• pp.91-97
• /
• 2023

Aging construction machinery and vehicles with old diesel engines usually have a long life span, so they continue to emit harmful emissions. Therefore, replacing these older diesel engines with engines that meet the latest emisstion standard is expected to help improve air quality, and engines with propane fuels, which are easily available at construction sites, can be an appropriate alternative. In this study, a propane fueled engine was developed based on a 6.8-liter CNG engine, and technologies such as gas injectors, exhaust gas recirculation (EGR), and enhanced catalysts were applied. As a result, nitrogen oxides achieved half of the emission performance at the Stage-V level, the latest emission standard, while securing diesel engine output and torque in the same class.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.8
• /
• pp.991-998
• /
• 2013

The fuel injection pipe of a common rail system used in a clean diesel vehicle plays a role in supplying fuel from a rail to the injector of each cylinder connecting the engine under a repeated internal pressure. The fuel injection pressure is increased to over 200 MPa for satisfying EU emission standards and improving fuel efficiency, and a heading process and an autofrettage process are required for preventing folding defects and improving fatigue life. In this study, the flow stress and SN data of the material of the pipe are obtained through a tensile test and a fatigue test. The heading process for checking the folding defects of pipe ends is performed by using FEA. Furthermore, the optimal design of the autofrettage process for improving fatigue life considering not only the compressive residual stresses of the inner surface but also the tensile residual stresses of the outer surfaces of the pipe under the repeated internal pressure is performed by using FEA. To verify the process design, fatigue analysis for the autofrettaged pipe is performed.