• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.6
• /
• pp.26-37
• /
• 2011

A 75-tonf-class LRE(liquid rocket engine) thrust chamber with ablative material for technology demonstration was manufactured on the basis of development technologies of 30-tonf-class LRE. Hydraulic characteristics of the thrust chamber were examined through cold flow test and ignition test of low flow condition. Test result showed that hydraulic function was good. Side ignition method with igniter ring also showed a fine function of ignition in operating ways of static condition. But a close review is required to understand the phenomena of generation and extinction of specific frequencies showed in dynamic characteristics ways. To achieve these, a large combustion test facility which is capable of performing combustion test at design condition of the 75-tonf-class thrust chamber should be constructed as soon as possible.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.69-73
• /
• 2009

Combustion test results of 1/2.5-scale thrust chamber for 75tonf-class liquid rocket engine were described. The thrust chamber has chamber pressure of 60 bar, propellant mass flow rate of 89 kg/s, and nozzle expansion ratio of 12. The combustion tests were conducted to verify the combustion performance, the regenerative cooling performance and the durability of thrust chamber at design point condition, and then were performed to confirm the operation and the combustion performance at low combustion pressure condition. All the tests had been successfully executed without the damage of the hardware. These test results present a possibility of hot firing test at low combustion pressure condition, and can be used as fundamental data to predict the combustion performance at design point condition for 75 tonf thrust chamber.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.29 no.8 s.145
• /
• pp.1176-1187
• /
• 2005

The purpose of this study was to evaluate the efficiency of cooling vests developed for farm workers harvesting red pepper in summer. The study was performed using the following two steps: 1) Climatic chamber test, 2) Field test. For the chamber test, a work environment was simulated as $33^{\circ}C$ and $65\%$RH, and the thermo-physiological and subjective responses were measured with and without cooling vests. Twelve young males participated as subjects. For the field test, three farmers participated while harvesting red pepper on the form, in summer. The measurements used were same as in the chamber test. Subjects were tested without any cooling vests, as a control. They were tested wearing vests with 2 frozen gel packs (CV2: Cooling area, $308cm^2$), and vests with 4 frozen gel packs (CV4: Sooting area, $616cm^2$). As a result of the chamber test, rectal temperature($T_{re}$) and mean skin temperature( $T_{sk}$) were lower in both CVs than in Control, and this tendency was statistically significant in CV4 (p<.05). Clothing microclimate temperature ($T_{clo}$) and total sweat rate (TSR) were significantly lower when wearing cooling vests (p<.05) Heart rate (HR) was also lower in wearing cooling vests than in Control, and the speed of recovery to the comfort level was faster when the subjects wore cooling vests. In addition, subjects felt 'less hot, less humid, and less uncomfortable' in both CVs than in Control. Field tests showed a similar tendency with the chamber tests. In particular, wearing the cooling vest was effective in restraining the raise of $T_{clo}$ on the back. It can be concluded that the cooling vest was effective in alleviating heat strain and discomfort in both the chamber test and the field test, despite the cooling area of the cooling vest being just $3.4\%$ of the body surface area ($616cm^2$).

• Journal of Auto-vehicle Safety Association
• /
• v.11 no.4
• /
• pp.50-56
• /
• 2019

Recently, automobile industries have developed ADAS, smart cars, connected cars, automated driving systems, which use a variety of sensor systems - ultrasonics, cameras, lidars and radars - and communication systems. It is necessary to examine the electromagnetic immunity of vehicles equipped with those systems. The electromagnetic immunity tests are carried out in an electromagnetic semi anechoic chamber, which is cut off from the outside. It is difficult to create test environments in which the radar sensor systems of vehicles work properly in the test chamber. In this study, test jigs were designed and tested and as a result they are shown to be effective to create test environments for electromagnetic immunity tests of vehicles equipped with radar sensors. We also proposed additional safety standards for immunity tests of vehicles with radar systems that currently do not exist.

• Journal of Auto-vehicle Safety Association
• /
• v.12 no.4
• /
• pp.7-12
• /
• 2020

Recently, automobile industries have developed ADAS, smart cars, connected cars, automated driving systems, which use a variety of sensor systems - ultrasonics, cameras, lidars and radars - and communication systems. It is necessary to examine the electromagnetic immunity of vehicles equipped with the sensor systems due to the fact that the normal operation of those systems is very important to the safety of the vehicles. The electromagnetic immunity tests are carried out in an electromagnetic semi anechoic chamber, which is cut off from the outside. It is difficult to create test environments in which the camera sensor systems of vehicles work properly in the test chamber. In this study, test jigs were designed and tested and as a result they are shown to be effective to create test environments for electromagnetic immunity tests of vehicles equipped with camera sensors. We also proposed additional safety standards for immunity tests of vehicles with camera systems that currently do not exist.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.5
• /
• pp.375-382
• /
• 2011

Semi volatile organic compounds (SVOCs) are used as plasticizers in building materials, interior materials, furniture, consumer electronics. etc. In the home, these SVOCs mix together with house dust. There is thus concern over the health effects of SVOCS in the home, there is a risk that they ini1uence childhood asthma and allergies. It is difficult to measure SVOCs emission rates from building materials or household appliances utilizing the usual test chamber methods, because the boiling points of SVOCs are higher and they are apt to adhere to the surface of the test chamber used. In this study, we introduce FLEC chamber method, passive sampler method and micro chamber method, which are used in Germany and Japan in order to measure SVOCs emission rates. Characteristic, merits and demerits of test methods are also considered.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11b
• /
• pp.101-104
• /
• 2005

This study presents experimental results from the performance test of a scaled reverberation chamber for measurement of sound insulation of panels. Experimental investigations were conducted in various parameters such as tunneling effect source locations, and maximum sound transmission loss. It is evident that the tunneling effect which means the variation with specimen location on the test frame gives rise to more than 3 dB deviation. One of the objective of this study that compares measured results between a real reverberation chamber and a simplified test apparatus, by using a specimen of a sandwich panel. It shows qualitatively resonable agreement from which one can find a potential to provide a design tool.

• Journal of the Korean Institute of Navigation
• /
• v.20 no.3
• /
• pp.107-115
• /
• 1996

With the rapid advance of electronic equipments and the frequent, use of them, the electromagnetic environments including EMC or EMI problems are very complicated. The radiation of electromagnetic waves from electronic equipments has strictly been controlled by the authorities concerned from many years ago. Though it is the most proper to test EMI or EMC in the open area test site, we have used the anechoic chamber in place of the test site because of its various restrictions. To achieve the purpose, in this paper, the performances of a few anechoic chambers according to absorbing materials are analyzed for horizontal and vertical polarizations respectively. Furthermore, the calculated and the measured site attenuations in semi-anechoic chamber made with ferrite grid are compared. The obtained results are to be valuable for designing an anechoic chamber.

• Journal of IKEEE
• /
• v.16 no.4
• /
• pp.290-296
• /
• 2012

In this study, an effective echo-suppression and cancellation technique using reflectors in semi-anechoic chamber and time-domain measurement is proposed. By using the proposed technique, the uniformity of electric field in QZ(Quiet Zone) could be improved and the antenna test environments similar to the fully anechoic chamber could be accomplished. The performances of the proposed test environments is verified with the simulated and measured data. And it is demonstrated that this test environment is possible to use the measuring the radiational characteristics of a small antenna in VHF band.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.427-430
• /
• 2008

Electroforming is one of the key technologies for the regenerative thrust chamber of the rocket engine. To use nickel electroforming method for the thrust chamber, direct electroforming of nickel on cupper and the welding method between different materials are needed. Minimizing the internal stress is one of the important factor for making thick electroforming,. Also minimizing contamination(ex. Sulfur containing compound) is another important factor for the stability of quality. This paper includes advanced methods for thick nickel electroforming, those of strength test results and EDS/EPMA inspection results. Advanced for electroforming process makes the achievement of Electro-beam welding between Inconel718(Manifold) and Nickel Electroforming. This paper also includes the influence of the electroforming precipitation angle on strength. Thus advanced electroforming improvement processes and the test results make achievement for manufacturing of the regenerative thrust chamber with direct nickel thick electroforming on cupper materials.