• Journal of Aerospace System Engineering
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• v.13 no.5
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• pp.72-78
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• 2019

Inlet hammershock is the critical loads condition for designing the inlet duct structure of a fighter. The sudden flow reduction in engine compressor causes inlet hammershock with high pressure. The traditional method was used to combine extreme conditions (maximum speed, sea level altitude, and cold day) to analyze this compression wave inlet hammershock pressure. However, after the 90s there have been papers that presented the probabilistic approach for the inlet hammershock to achieve the appropriate design pressure. This study shows how to analyze the inlet hammershock pressure by making practical use of the Republic of Korea Air Force real flight usage data under probabilistic approach and then analyze approximately 30% decreased inlet hammershock pressure compared with the traditional valve.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.136-142
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• 2007

A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The supersonic cascade with a 2-dimensional supersonic nozzle was tested for the axial gap ratio (${\delta}$) of the supersonic turbine that is the one of the turbine design parameter. Firstly, the flow was visualized by a single pass Schlieren system. Next, total and static pressure of the cascade were measured by a pressure scanning system. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

• Explosives and Blasting
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• v.26 no.2
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• pp.29-37
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• 2008

In general, the size of tunnel cross section in construction site is $50{\sim}200m^2$. But, electric cable tunnel, telecommunication cable tunnel, mine tunnel. Waterproof tunnel have small cross section less than $20m^2$. There are so many problem at small sectional tunnel: restriction of equipment, dead pressure by precompression, loss of efficiency, increase of work time. Especially, explosives remainder by precompression of previous detonation is serious problem. To find its measures of dead pressure (explosives remainder), the following series of progress have been conducted: (1) survey of previous study (2) investigate causes of dead pressure (3) set up of its measures (4) application and appraisal at tunnel site. The measures, change of cut pattern, hole space over 40cm, adjustment of delay time, are proved by experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.95-98
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• 2004

The present work has been developed the study of interpretation of separation behavior in gas expansion separation(GES) bolt which has the separation characteristic without fragmentation and minimum pyre-shock during the operation of the explosive bolt. In order to obtain the performance of minimum pyro-shock, the present work used non-compressive material instead of separation explosives. The use of the interpretation processor could be extensively helped to design the shape and the amount of explosives in the explosive bolt having complex geometry, and to analyse the separation behavior during the operation. It is also proved that the GES bolt is the most suitable the separation system necessary to minimum pyro-shock and non fragmentation compare to others.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.539-549
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• 2017

In this paper, experimental studies on the shroud separation were performed to investigate characteristics of the shroud separation at mach 3. Shroud separation tests were carried out in the vertical free-jet wind tunnel that is capable of testing separable structures. A shroud model was miniaturized to meet test objectives and test section dimensions of the wind tunnel. Pneumatic Locking and separation mechanisms were designed considering external force due to free stream. High speed cameras were used to record the shroud motion and unsteady shock patterns over the deploying shrouds during the shroud separation process. Also, unsteady pressures on the nose surface were measured by using the pressure sensors. Through the tests, the measurement data necessary for researches on the shroud separation technology were obtained. Shroud separation behaviors and characteristics of unsteady pressure on the nose surface for each external flow conditions were analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.115-122
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• 2020

This study aimed to improve the reliability of the assurance pressure of a gun barrel due to the difference between the US Standard and Korean Standard. In addition, the reliability was found to differ according to the maximum pressure of the Ammunition, so restrictions are expected. During the development of the new bullet, the maximum pressure of the bullet was approximately 3,000 psi higher than the assurance pressure of the gun barrel. To solve this problem, the reliability of the cannon was analyzed when the assurance pressure of the gun barrel increased. First of all, the technical data from overseas were reviewed to check for cases of increased assurance pressure, and tests were performed to determine if it could withstand high pressure through a verification firing test. Finally, the simulation analyzed the stability of the recoil buffer. The study found no abnormal results in all items, suggesting that an increase in the assurance pressure for a gun barrel was possible. This study is expected to be used as basic data for future reliability studies of similar equipment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.521-530
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• 2011

Since aircraft fuel tanks have many interfaces connected to the airframe as well as the fuel system, they have been considered as one of the system-dependent critical components. Crashworthy fuel tanks have been widely implemented to rotorcraft and rendered a great contribution for improving the survivability of crews and passengers. Since the embryonic stage of military rotorcraft history began, the US army has developed and practised a detailed military specification documenting the unique crashworthiness requirements for rotorcraft fuel tanks to prevent most, hopefully all, fatality due to post-crash fire. The mandatory crash impact test required by the relevant specification, MIL-DTL-27422D, has been recognized as a non-trivial mission and caused inevitable delay of a number of noticeable rotorcraft development programs such as that of V-22. The crash impact test itself takes a long-term preparation efforts together with costly fuel tank specimens. Thus a series of numerical simulations of the crash impact test with digital mock-ups is necessary even at the early design stage to minimize the possibility of trial-and-error with full-scale fuel tanks. In the present study the crash impact simulation of a few fuel tank configurations is conducted with the commercial package, Autodyn, and the resulting equivalent stresses and internal pressures are evaluated in detail to suggest a design improvement for the fuel tank configuration.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.3
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• pp.37-44
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• 2003

In rough seas, bow-flare regions of the sea-going ships are subject to high impact pressures due to the bow-flare slamming and panting. And many ships suffer structural damages in that region, even though they were built under the bow structure strengthening rules of the ship classes. So, a new design method for bow-flare structure is highly required. In this paper, bow-flare damage analysis is performed for 17 ships (total number of damage/non-damage data is 782). Based on this analysis, a new design standard and method for bow-flare structure (shell plate, frame and web frame) is proposed. 80.4% of the present damage/non-damage data were well-explained by this new design standard.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.49-59
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• 2008

In this study, the design method of a 155 mm Solid Fuel Ramjet projectile is proposed and a flight performance analysis program through mathematical modelling is developed. Through flight performance analysis, ramjet performance during flight, which is comprised of thrust, specific impulse, pressure recovery ratio, location of shock waves, and magnitude of drag, was predicted. The results show that compared to Rocket Assisted Projectile(RAP), the range was increased by 90 %. Furthermore, how variations in nozzle exit area ratio and the intake area cause variations in range was observed. This research on modeling and simulation methodology will provide useful data for future development of solid fuel ramjet projectiles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.265-271
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• 2007

A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. Experiments were performed to find the flow characteristics of a supersonic turbine with the cascade positions and to find a factor of the expansion loss. The supersonic cascade with a 2-dimensional supersonic nozzle was tested with the cascade positions. The flow was visualized by a Z-type Schlieren system. The static pressures at the turbine cascade inlet and outlet were measured by pressure transducers and a pressure scanner. Also, The total pressures at the turbine cascade back flow were measured. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions of the supersonic turbine were observed. And the flow characteristics in the supersonic turbine with the cascade positions were observed.