• The Journal of Engineering Geology
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• v.30 no.3
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• pp.223-235
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• 2020

In this study, pulse tests were undertaken at an underground research facility, as part of in-situ hydraulic tests, to derive the hydrogeological characteristics of crystalline rock. The applicability of pulse tests for estimating the transmissivity of a fractured rock mass was evaluated by comparing the results to those from a slug test. Results from the pulse and slug tests were very similar for the test section, with both tests indicating low transmissivity. A slight difference between the results of pulse and slug tests, however, was observed in the section with the transmissivity larger than 1 × 10^-8 ㎡/s, which is likely due to the difference in the radii of influence of the tests. Furthermore, when the pulse test was conducted in permeable zones where transmissivity was larger than 1 × 10^-7 ㎡/s, it was difficult to produce accurate results. This lack of accuracy was due to the rapid recovery of the hydraulic head in these permeable test zones. When performing pulse tests, it was important to accurately measure the pressure when valves were opened and closed in order to apply the head change in the test section. Although it is difficult to derive the hydrogeological characteristics from pulse tests in areas with high permeability, these tests can be used as an economical test method for identifying hydrogeological characteristics in a relatively short time, especially when deriving the transmissivity of rocks with low permeability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.666-669
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• 2011

The rupture disc shapes of bulkhead type pulse separation device(PSD) are designed for new dual pulse rocket motor. Before final design PSD, that three different rupture disc are tested and confirmed the performance of the discs. Through analyzing the test results the PSD decides, two rupture disc shapes with flow holes of eight circles and eight trapezoids.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.121-131
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• 2020

In this paper, the transmissivities obtained from the pulse test, the slug test and the constant head test were compared each other to assess an applicability and a reliability of the hydrogeological test method, which are commonly used to derive the hydrogeological properties of a crystalline rock at un underground research facility. When comparing the results of the pulse test and the slug test, the transmissivities were very similar in the entire test section of the medium. However, there was a little discrepancy in the results in the areas where the permeability is relatively high. The results of the constant head test on the same section showed the lower transmissivity than the results of the pulse test and the slug test on the highly permeable section. This difference in permeability was considered to be due to the difference in the radius of the hydraulic effect applied in each hydraulic test. When the heterogenetic distribution of fracture affects the hydrogeological properties on crystalline rock, it is believed that the hydrogeological characteristics can be explained through a constant head test or a constant flow rate test with a large hydraulic effective radius, as well as a pulse and a slug test that can identify hydrogeological properties in a relatively short time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.24-27
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• 2012

In this study, the full scale flight type Dual-Pulse Rocket Motor(DPRM) with the bulkhead type Pulse Separation Device(PSD) was designed, manufactured, and fire-tested. The bursting time and pressure of PSD were analyzed by the pressure, thrust and vibration results of static fire tests and ablation of PSD was measured with 3-D coordinate measuring machine. As a result, PSD requirements, bursting conditions and thermal safety, were satisfied.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.60-66
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• 2014

As a evaluation method of combustion stability in a liquid rocket engine thrust chamber, external disturbance devices are used. In the paper, the study on pulse-gun ignition tests for a combustion stability rating test of a thrust chamber was performed. Charging volume of pulse-guns was determined by confirming the intensities of the pressure waves from the ignition tests in the cold-flow conditions. While using same injector head, combustion instabilities were not encountered during 14 hot-firing tests without pulse-guns but combustion instabilities were triggered by pulse-gun ignition during 2 hot-firing tests. The results showed that the pulse-gun ignition test could be the evaluation method and could reduce the hot-firing test number for the stability rating of a thrust chamber.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1490-1491
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• 2006

포항가속기연구소 선형${\mu}$가속기의 대전력 RF부품의 시험과 RF증폭을 위해 사용되는 클라이스트론 튜브의 시험용 전원으로 펄스전원인 모듈레이터를 사용하고 있다. 고전적인 방식의 교류전압을 변환하여 직류로 만들고 이 전원을 L-C공진충전에 의해 펄스를 생성하는 펄스 커패시터에 약 2배의 직류전원으로 충전하는 기법을 사용하고 있다. 이들 전원은 저주파의 대용량 변압기를 사용하여 직류로 변환하는 부품들의 부피가 크다. 새로운 충전기법을 적용한 펄스전원의 경우는 고주파 인버터 전원을 채택하여 그 부피를 줄이고 지령충전에 의해 펄스를 생성하는 싸이라트론의 애노드에 고전압이 머무는 시간을 줄임으로서 자발방전이나 고전압 아크에 의한 오동작을 최소로 할 수 있다는 장점이 있다. 본 논문에서는 고주파 전원 방식을 채용한 펄스 모듈레이터의 제어방법의 개선과 부피를 줄여 운전의 효율성을 높인 내용으로 발표하고자 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.101-104
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• 2010

A bulkhead-type pulse separation device has been developed for the multi-pulse rocket motor. The design parameters of the pulse separation device were the shape of the rupture disc slit, welding conditions, and the implementation of the seal disc. The pneumatic tests of the fabricated pulse separation devices showed that the rupture pressure increased as the quantity of the rupture disc slit and welding strength increased and the seal disc was implemented.

• Proceedings of the KIEE Conference
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• summer
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• pp.1184-1186
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• 2004

Focus Electrode(FE) 기능을 갖는 진행파관 증폭기(TWTA)를 구동하기 위하여 고전압 펄스전원 장치가 필요하다. 이 전원장치는 영부터 -5.0 kV TWT 캐소드 고전압 위에서 펄스 출력으로 동작되어야 한다 고전압펄스전원장치는 바이어스 전압이 영부터 -1.5 kV사이를 연속적으로 가변 할 수 있어야 하고, 펄스의 반복 주파수는 CW로 부터 1 kHz 그리고 펄스폭은 $10\;{\mu}s$부터 $500\;{\mu}s$로 선택 가능하여야 한다. 그리고 출력펄스의 상승 및 하강 시간은 150 ns 보다 작아야 한다. 턴-온 및 오프의 스윗칭 시간을 만족시키기 위하여 고전압 스위치는 직렬로 연결된 FET 모듈을 사용하였다. 본 논문에서는 이러한 고전압 펄스전원장치의 설계 및 제작원리 그리고 시험결과에 대하여 다루었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.99-106
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• 2005

The SRT(stability rating test) technique, which is indispensable for the development of a LRE(liquid rocket engine), essentially requires a development of a combustion test sequence as well as artificial perturbation devices. For the development of an indigenous SRT technique, several combustion tests of sub-scale LRE were performed to search a proper combustion test sequence. At first, a pressure-wave inducing device which is used for adapting pulse gun was designed and a cooling gas supply system for the pressure-wave inducing device was set up to prevent a malfunction of pulse gun. Through the several combustion tests which included cooling procedure of a pressure-wave inducing device, a proper combustion test sequence was found out. It did not make any significant disturbance at normal combustion process. Finally, an indigenous SRT technique has been developed successfully.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.1
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• pp.98-106
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• 2022

To develop reliable dual pulse rocket motor, vacuum ignition performance at high altitude and design stability for rupture pressure of the Pulse Separation Device(PSD) are required. In this study, rupture pressure analysis method for the membrane type PSD of the dual pulse rocket motor was developed. The PSD rupture pressure formulation was derived from strain-pressure relationships. The PSD vacuum rupture test apparatus and the PSD 1 second vacuum ignition test apparatus were developed, which can simulate the high altitude vacuum environment. Rupture pressure of PSD was analyzed by conducting the PSD vacuum rupture test, and design values of PSD were derived. Finally, vacuum ignition performance and rupture pressure of the designed PSD were validated with PSD 1 second vacuum ignition test.