• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.383-391
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• 2009

Vibrations at different frequencies with a different intensity as well as a pressure pulsation with different parameters are two phenomena which can be observed at different water turbines. Due to the vibration and the pressure pulsation some restrictions of water turbine operation range are applied. Similar problems with the efficiency level in a wide water turbine operation range are the basic problems which are solved for ages. A theoretical and practical solution of the above mentioned problems is very much time and money consuming. The paper describes a new theoretical solution of the excitation and pressure pulsation decrease as well as extension of the operational range with high efficiency level. The new concept to decrease the vibrations and pressure pulsations is based on a heterogeneous runner blade geometry generation. The new concept of the runner geometry design was numerically tested at a low specific speed pump turbine, see Fig. 1, and basic points of the concept are presented in this paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.128-133
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• 2005

In this study, performance design programs for components of a turbopump unit (TPU) in a Liquid Rocket Engine (LRE), that has non-cryogenic centrifugal pumps and 1-stage impulse turbine with partial admission nozzle, were developed. The programs were integrated in a TPU module by balancing the mass flow rate for pump-turbine power, and the module was inserted into the LRE system conceptual design program. The fundamental design conditions, satisfying LRE system requirements and minimum mass flow rate condition of gasgenerator, were found and compared with data from a Russian liquid rocket engine.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.5 no.1
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• pp.1-6
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• 2009

In this study, an ORC (Organic Rankine Cycle) is investigated for a low-temperature geothermal power generation by a simulation method. A steady-state simulation model is developed to analyze cycle's performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump are modelled by an isentropic efficiency. Simulations were carried out for the given heat source and sink inlet temperatures, and given flow rate that is based on the typical power plant thermal-capacitance-rate ratio. HFC-245fa is considered as a working fluid of the cycle. Simulation results, at the given secondary working fluids conditions, show that even though the power can be presented by both the evaporating temperature and the turbine inlet superheat, it depends on the evaporating temperature primarily.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1036-1042
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• 2012

This paper describes an analysis on exergy efficiency of R744 OTEC power system to optimize the design for the operating parameters of this system. The operating parameters considered in this study include subcooling and superheating degree, evaporation and condensation temperature, and turbine and pump efficiency, respectively. The main results are summarized as follows : As the evaporation temperature, superheating degree, and turbine and pump efficiency of R744 OTEC power system increases, the exergy efficiency of this system increases, respectively. But condensation temperature and subcooling degree of R744 OTEC power system increases, the exergy efficiency of this system decreases, respectively. The effect of evaporation temperature and pump efficiency on R744 OTEC power system is the largest and the lowest among operation parameters, respectively. Therefore, the refrigerant temperature in the evaporator must be closely to the surface seawater temperature to enhance the exergy efficiency of R744 OTEC power system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.93-96
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• 2011

A genetic algorithm (GA) has been employed to optimize the major design variables of the liquid rocket engine. Mass flow rate to the main thrust chamber, mass flow rate to the gas generator and chamber pressure have been selected as design variables. The target engine is the open gas generator cycle using the LO2/RP-1 propellant. The objective function of design optimization is to maximize the specific impulse with condition of energy balance between the pump and the turbine. The properties of the combustion chamber have been obtained from CEA2. Pump & turbine efficiencies and properties of the gas generator have been modeled mathematically from reference data. The result shows 3~4% errors for the specific impulse and 2~6% errors for the pump power of the gas generator cycle compared to references.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.324-327
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• 2008

Two stage startup of high thrust liquid rocket engine can reduce the abrupt impulse to the vehicle and engine by changing oxidizer flow rate to the combustion chamber. Also it ensures stable ignition of combustion chamber against hard start and to prevent pump stall by the sudden supply of large mass flow rate. However high discharge pressure of oxidizer pump or temperature rise in gas generator may be a problem in applying the preliminary stage. To solve this problem, we analyzed the effect of the slope of oxidizer pump's head curve and the oxidizer mass flow rate to combustion chamber during preliminary stage using the rocket engine startup analysis code. A moderate slope(${\circleddash}{\sim}$-3) of head curve and 80% mass flow rate during preliminary stage can reduce the oxidizer pump discharge pressure by 15 to 20% comparing with the condition of ${\circleddash}$=-4.37 head curve and 70% mass flow rate. Also it can maintain the turbine inlet temperature rise within 50K from the nominal value.

• Tribology and Lubricants
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• v.28 no.4
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• pp.167-172
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• 2012

The turbo pump of a liquid rocket engine is composed of three main parts: the oxidizer pump, fuel pump, and turbine. Liquid oxygen ($LO_X$) is the working fluid in the cryogenic environment in the oxidizer pump, but tests are usually performed using liquid nitrogen ($LN_2$), which has a boiling point similar to that of $LO_X$ but is comparatively safer and easier to use for the test. In this study, a bearing test rig is developed and its performance is evaluated using a cryogenic ball bearing with $LN_2$ as the working fluid. Verifying the performance of the bearing test rig is crucial for ensuring correct working of the turbo pump unit in the liquid rocket engine. A stable test rig for the bearing in a cryogenic environment makes the bearing technology enhance its reliability. The test results show that the system operates stably and the requirement of performance time of 500 s is met. The test results of temperature, motor speed, and torque are discussed. The developed cryogenic bearing test rig is expected to help in widening knowledge and expanding research on ball bearings in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.198-202
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• 2005

Gas generator is the equipment to produce high enthalpy gas used to generate sufficient power to operate turbine and pump system for propellant feeding in liquid rocket engine. Since the limit in operating temperature is imposed due to turbine blade, the gas generator has to be operated at the temperature far below stoichiometric maintaining fuel rich combustion. In this research, fundamental study was performed to understand the non-equilibrium combustion process with in-house code and CFD-ACE as well.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.338-342
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• 2014

Energy storage is a key issue when integrating large amounts of intermittent and non-dispatchable renewable energy sources into electric power systems. To maintain the instantaneous power balance and to compensate for the influence of power fluctuations from renewable sources, flexible capability for power control is needed. Adjustable Speed Pumped Storage Power Generator is pumped storage unit that is adjustable for pump output adjustments as well as the highest efficiency operations because it has fast response time. In this paper we address the adjustable speed pumped storage power generator for frequency control against the intermittence of wind turbine output and calculate the appropriate capacity of adjustable speed pumped storage power generator.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.99-103
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• 2003

An analysis of the flow within supersonic turbine cascades is necessary to design and manufacture turbo-pump system. Because of the differences between the specified inlet boundary value and the computed inlet value caused by the far field inlet boundary condition, the computations at desired inlet conditions can not be achieved. So, this paper studied the problem occurred when far field inlet conditions were specified as inlet boundary conditions. And the numerical analyses using Fine Turbo, CFD Program, has been performed and compared with those of experiments when a converging-diverging nozzle or a linear nozzle was located in front of cascades instead of the far field inlet condition.