• Aerospace Engineering and Technology
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• v.7 no.2
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• pp.170-175
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• 2008

In this study, it was investigated that the characteristics of startup and compatibility using several type hot and cold gases. The characteristics of starting LRE by pyro starter was compared with that by a Helium spinner. The compatibility of pyro gas, a gaseous Helium, Hydrogen+Nitrogen mixture gas, and air was investigated by a simple 1D turbine analysis considered the properties of each gas and turbine efficiency. Most of them were compatible to start up the LRE however air was properly used only for low power mode of turbine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.216-220
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• 2006

In this study, it was investigated that the characteristics of startup and compatibility using several type hot and cold gases. The characteristics of starting LRE by pyro starter was compared with that by a He spinner. The compatibility of pyre gas, a gaseous He, H2+N2 mixture gas, and air was investigated by a simple 1D turbine analysis considered the properties of each gases and turbine efficiency. Most of them were compatible to start up the LRE but air was properly used only when the turbine was low power mode.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.70-75
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• 2014

Programs of energy balance, mode analysis and transient analysis for a liquid rocket engine have been introduced. The analysis methods have been verified through comparison between the present results, and the results of the other program and experimental data. An energy balance analysis is used for engine system design at the early development phase. A mode analysis is used for decision of engine operation conditions and test conditions, and studying deviation of an engine performance. A transient analysis can predict a propellant flow rate, thrust, impulse at transient phase. It is essential to establish a startup/shut down sequence. The analysis programs will be used to develop the engines of KSLV-II.

• Asian Journal of Innovation and Policy
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• v.7 no.3
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• pp.511-533
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• 2018

As the developed and developing economies make the transition to knowledge-based economies, the high-tech sector has been the primary engine in enabling this transformation. Given this context, the policy making and implementation abilities of the countries' local administration assume significance. This study therefore attempts to examine the policy evolution undertaken by China and India which resulted in the emergence of high-tech startup ecosystems in these countries. Further, using a theoretical framework for an ideal entrepreneurial ecosystem, it tries to understand the similarities and differences prevalent currently in the Indian and Chinese high-tech startup ecosystem. The results of the study indicate that although both the countries took different paths, from a macro-perspective, they follow the same pattern as observed in the US and Israel policy making - that of the change in the role of Government as a regulator to that of an enabler of the entrepreneurial ecosystem. The differences and similarities between the key entrepreneurial ecosystem components provide additional knowledge about the currently prevailing conditions of the ecosystem in these countries.

• Journal of Power Electronics
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• v.13 no.5
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• pp.841-853
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• 2013

An application of doubly-fed induction generator (DFIG), which is one of adjustable speed generators, to a gas engine cogeneration system has been investigated. To operate during a blackout as an emergency power supply is one of important roles for the gas engine cogeneration system. However, the DFIG requires initial excitation for startup during a blackout because the DFIG has no excitation source. In this paper, we propose the "blackout start" as a new excitation method to generate a rated voltage at the primary side during a blackout. In addition, a stand-alone operation following a blackout has been investigated by using experimental setup with a real gas engine. Power flows in the generating set with the DFIG at the stand-alone operation have been investigated experimentally. Experimental investigation of the power flow suggests that the generating set with DFIG has optimal speed in minimizing whole system losses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.129-132
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• 2008

For the development of the 30tonf level LOx/kerosene liquid rocket engine, turbopump-gas generator closed-loop coupled tests are performed. To simulate engine operation conditions, combustion chamber was substituted by flow control orifices. In simulated engine system operation environment, chill-down procedure, startup characteristics, nominal operability of turbopump+gas generator coupled Test Plant are confirmed. Turbopump and gas generator are confirmed to operate well in simulated engine environment. The control system for regulating power and mixture ratio of Test Plant are also successfully confirmed.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.56-64
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• 2010

A system design has been conducted of the liquid rocket engine for Korean launch vehicle (KSLV-II, Korea Space Launch Vehicle II). The present turbopump-fed liquid rocket engine of vacuum thrust 76 ton and vacuum specific impulse 297 sec adopts gas generator cycle. The combustion pressure of the regeneratively cooled combustor is 60 bar. The propellant is LOx/kerosene. The engine is started by pyrostarter and the combustor is ignited by TEA (TriEthylAluminium). The engine system performance and the subsystems performance requirements are given through energy balance analysis. The combustion pressure, specific impulse and the engine mass are analyzed to be reasonable comparing with the published data. The startup analysis method which will be used in the future has been validated against the turbopump-gas generator coupled test. The tuning method for performance variation of the engine which is not actively controled has been prepared by mode analysis and performance deviation analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.563-568
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• 2010

Turbopump-gas generator open-loop coupled tests are performed during the development of a 30tonf-LOx/Kerosene rocket engine. In the turbopump-gas generator open-loop tests, the propellants to gas generator are supplied from the outlets of turbopump, while the gas exhausted from the gas generator is vented out to the atmosphere, instead of being used to turbine driving. This paper presents the objectives, procedure, and results of the open-loop coupled test, in addition to a schematic representation of the test apparatus and the operating conditions for the test facility system and control system. The results of turbopump-gas generator open-loop coupled test confirm chill-down procedure, startup characteristics, nominal operability and smooth shutdown of the open-loop coupled Test Plant in test conditions simulating engine system operation environment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.10
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• pp.801-807
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• 2020

Opening characteristics of a main oxidizer shut-off valve at different valve inlet pressures have been experimentally investigated. The pilot pressure at the moment of the valve opening increases linearly with increasing the valve inlet pressure and the increased pilot pressure reduces the valve travel time. As the pilot pressure increases at the moment of valve opening, the time to start opening the valve is delayed resulting in increasing the valve opening time. With the increment of the valve inlet pressure, the valve opening time is mainly determined by the time required for the pilot pressure to start opening the valve. Therefore the design of a pilot gas supply system can readily control the valve inlet pressure at the valve opening as well as the amount of oxidizer supplied to a combustion chamber during the engine startup.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.165-172
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• 2004

LE-7A is the main engine of the H-IIA launch vehicle. Under its development, the nozzle suffered from two troubles during startup and shutdown transients of the engine. One is a large side load, which damages the actuator of the nozzle, and the other is damage on regenerative cooling tubes due to high heat load. It has been considered that these problems are caused by a peculiar separation pattern called Restricted Shock Separation (RSS). RSS is observed in several rocket nozzles, for example, LE-7A nozzle, Vulcain nozzle and so on. Their contours are not conventional truncated perfect (TP) nozzle - LE-7A nozzle is a compressed truncated perfect (CTP) nozzle and Vulcain nozzle is a thrust optimized (TO) nozzle. Although it is believed that the occurrence of RSS is affected by the nozzle contour, the mechanisms are not clarified sufficiently yet. In the present paper, a parametric numerical study is carried out to investigate the mechanisms of the occurrence of RSS in CTP nozzles during startup transient. The results show that RSS is caused by the adverse pressure gradient downstream of the Mach disk. The adverse pressure gradient is caused by the interaction of the pressure wave and Mach disk. The method to avoid the occurrence of RSS is also examined. A small step inside the nozzle affects the position of the separation point and prevents RSS. The result shows that the possibility that RSS can be suppressed by controlling the position of the separation point.