• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.839-848
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• 2000

This paper presents the results of an electromagnetic field analysis for a reverberation chamber that is an alternative method of a shielded anechoic chamber, which is widely used for the analysis and measurement of electromagnetic interference and immunity test. Inside the defined test volume of the rectangular and triangular type, the Schroeder Quadratic Residue Diffuser was employed. FDTD(Finite-Difference Time-Domain) simulation method was applied to produce the field characteristics inside those reverberation chambers. According to the results, field uniformities on the aforementioned two types of reverberation chambers were correlated within $\pm$3dB, and $\pm$4.4dB tolerances, and rectangular type reverberation chamber shows an independent polarization result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1188-1191
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• 2017

Thrust is one of the crucial performance parameter of a combustion chamber in the combustion chamber development test. So it is very important to measure an accurate thrust. Thrust calibration test was performed to identify the system characteristics, resistance and linearity of a vertical thrust measurement system(TMS) for accurate thrust measurement. It has been found 6.9% ~ 8.6% errors between the measured thrust by TMS calibration equations and theoretical thrust. It has been confirmed that the TMS calibration is necessary to be performed with the propellant lines connected to the combustion chamber for accurate thrust measurement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.603-615
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• 2012

Durability testing method trends of the thermal barrier coating(TBC) for the combustion chamber of the liquid-propellant rocket engine has been investigated. Many types of the durability testing method such as the mechanical tests to measure surface cohesion force, the thermal fatigue tests with laser, furnace, burner or plasma, the small scale combustion tests using injectors, and the thermo-mechanical fatigue tests were observed. The TBC with sufficient durability can be selected for the use of combustion chamber through such specimen-level tests and the durability can be verified by the tests using the real scale combustion chambers.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.272-279
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• 2019

In order to perform a pressure chamber experiment with a circular cylindrical pressure vessel, the dimensions of the cylinder need to be determined in the range of the maximum externally applied pressure of the chamber to create the collapse process. In this study, the collapse load values from published chamber test results, finite element analysis and the theory of thick cylinders were thoroughly compared in a aluminum cylinder. In order to investigate the effect of collapse load according to the ovality during manufacturing, nonlinear buckling analysis was performed and the collapse load according to ovality was compared. Based on the results, the dimensions of the steel cylinder were determined for the future chamber collapse test.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.40-46
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• 2006

A 30-tonf-class fullscale thrust chamber for the application to a Low-Earth-Orbit Space Launch Vehicle has been combustion tested over the wide ranges of a mixture ratio and a chamber pressure. The thrust chamber designed for a pump-fed open cycle engine was tested with an ablative chamber instead of a regenerative one for the initial evaluation of its performance and function. The test results revealed stable combustion characteristics. The hardware survived the harsh environment and showed very sound functional characteristics. The measured combustion efficiency turned out to be 95% and a specific impulse at sea level was estimated as 254sec, which are comparable to or above the predetermined design values.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.133-137
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• 2008

Results of combustion tests performed for a regenerative cooling combustor of a 30 tonf-class liquid rocket engine were described. The combustion chamber has chamber pressure of 60 bar, propellant mass flow rate of 89 kg/s, and nozzle expansion of 12. The combustion chamber is composed of mixing head, baffle injector, and regenerative cooling chamber. The hot firing tests were performed at design and off-design points. The test results show that the combustion characteristic velocity is in the range of 1738${\sim}$1751 m/sec and the specific impulse of the combustion chamber is in the range of 253${\sim}$270 sec. The peak of combustion characteristic velocity and specific impulse for this combustor is shown at mixture ratio of 2.35 and 2.5, respectively.

• Journal of Korean Clinical Health Science
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• v.1 no.2
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• pp.31-37
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• 2013

Purpose. This study was to investigate the analysis of the central corneal thickness and anterior chamber depth of eyes in Korean Young Population using the Pentacam topography. Methods. The subjects consisted of 126 eyes from normal cornea of Korean aged 7-12($8.857{\pm}1.501$) years during 2009. The thinnest location, pachy apex, and pupil central region of the cornea thickness was measured using the Pentacam pachymetry. The anterior chamber depth of normal corneas was measured with Pentacam. Results. The thinnest location of corneal thickness was $547.413{\pm}37.893$um. The pachy apex of cornea thickness was $552.103{\pm}36.016$um. Also, the pupil center of corneal thickness was measured $552.143{\pm}36.418$um. On the other hand, the mean thickness in the central cornea was a statically significant relationship(t-test, p=0.0002) between pachy apex and thinnest zone. Also the mean thickness of the central cornea was a statically significant correlation(pearson p=0.0001) among the pupil center, pachy apex and thinnest zone. The anterior chamber depth was $3.137{\pm}0.308$mm. The mean depth in the anterior chamber of cornea was a statically relationship(t-test, p>0.05) between OD and OS. Conclusions. The results of this clinical study suggested that the analysis of the central corneal thickness and anterior chamber depth using Pentacam in Korean young population can provide the useful morphological information in diagnosis of cornea for the contact lens fitting and corneal refraction surgery.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.79-84
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• 2012

An experiment of rapid pressurization-induced crack propagation of solid propellant was conducted by using a windowed test chamber. A pre-cracked specimen of solid propellant is installed in the chamber, and highly compressed nitrogen gas in an accumulator pressurizes the chamber until the chamber pressure reaches set-up pressure to make the chamber depressurization. Pressure-time trace was obtained from the experimental result, and pressurization rate was defined from the trace. In this study, three pressurization rates (64.34, 73.86 and 85.44 MPa/s) are considered, and propagation lengths are measured. Also, a progression of the crack propagation recorded by a high-speed digital camera is presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.539-544
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• 2012

An experiment of rapid pressurization-induced crack propagation of solid propellant was conducted by using a windowed test chamber. A pre-cracked specimen of solid propellant is installed in the chamber, and highly compressed nitrogen gas in a accumulator pressurizes the chamber until the chamber pressure reaches set-up pressure to make the chamber depressurization. Pressure-time trace was obtained from the experimental result, and pressurization rate was defined from the trace. In this study, three pressurization rates (64.34, 73.86 and 85.44 MPa/s) are considered, and propagation lengths are measured. Also, a progression of the crack propagation recorded by a high-speed digital camera is presented.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.50-57
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• 2014

A ground hot-firing test (HFT) was conducted to take out the optimal design configurations for the thrust chamber of 70 N-class liquid rocket engine under development. Monopropellant grade (purity: ${\geq}98.5%$) hydrazine was adopted as a propellant for the HFT, and three kinds of thrust chambers having characteristic lengths ($L^*$) of 2.79, 2.95, and 3.13 m were selected for their performance evaluation. It is revealed through the test and evaluation that the increase of the $L^*$ leads to a performance degradation in the test condition specified, and pulse response performance of the development model shows superior characteristics to commercialized hydrazine thrusters.