• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1266-1276
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• 2018

In this paper, three-dimensional neutronic calculations were performed in order to calculate the dependency of CRW on the temperature of fuel and moderator and the moderator void. Calculations were performed using the known MTR_PC computer codes in the core configuration 61 of TRR. The dependency of CRW on the fuel temperature in the range of $20-340^{\circ}C$ and the moderator temperature of each control rods were studied. Based on the positions of the control rods, the calculations were performed in three different cases, named case A, B and C. By the results, the worth of each control rods increases by increasing of the coolant temperature in all methods, however, the total CRW is somewhat independent of the fuel temperature. In addition, the results showed that the variation of CRW versus density depends on the positions of the control rods and the most change in CRW in the coolant temperature, $20-100^{\circ}C$ (279 pcm), belongs to SR4. Finally the effect of void on CRW was studied for different void fraction in coolant. The most worth change is about $2 for 40% void fraction related to SR1 and SR3 in case B. For 40% void fraction, the total CRW increases about $7.5, $6 and $7 in cases, A, B and C, respectively.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3001-3006
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• 2008

Recently, the internal combustion engines have focused on reducing both the CO2 emissions in order to cope with severe regulations for greenhouse effect. Therefore, various new technologies have been developed in many countries. Among them, the cooling system is spotlighted because it has great effect on fuel efficiency. However, the present engine cooling system is almost same as one of the 50 years ago. The needs for high performance and compact size make it important to improve engine cooling system, down-sizing and control method of coolant flow. Thus, low fuel consumption technology such as control and synthetic management of cooling system was necessary to satisfy with these needs. In this study, we applied electric thermostat to improve the fuel economy. The fuel consumption was compared after driving FTP-75 mode on both conditions which were with a conventional wax thermostat and with a electric thermostat. The coolant temperature of opening the electric thermostat is higher.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.161-166
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• 2022

To measure the change in friction loss due to the control of fuel mass and oil temperature in a gasoline engine, the floating liner method was used to measure the friction generated by the piston of a single-cylinder engine. First, to check the effect of combustion pressure on friction, the friction loss was measured by adjusting the fuel mass. It was confirmed that the friction loss increased as the fuel mass increased under the same lubrication conditions. In addition, it was confirmed that the mechanical efficiency decreased as the fuel mass increased. Next, to check the effect of lubrication conditions on friction, the friction loss was measured by controlling the oil temperature. It was confirmed that friction loss increased as the oil temperature decreased at the same fuel mass. As the oil temperature decreases, the viscosity increases, resulting in decreased mechanical efficiency and increased friction loss.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.76-85
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• 2016

This study introduces the system layout and control strategy necessary to start and operate a fuel processor in a wide range of temperatures where a gasoline was selected as the fuel of fuel processor considering logistic support of Korea Army. The autothermal reformig(ATR) catalyst is heated to light-off temperature by combustion method in the initial stage. In order to ignite the gasoline and air mixture stably, the glow plug is installed after ATR catalyst. When the catalyst is increased to light-off temperature, the reformer is operated from initiation to steady state conditions as follows: Partial oxidation(POX) mode, partial ATR mode, full ATR mode. Finally the start-up and control strategy is validated by the operational test of gasoline fuel processor at low and room temperature. As a result the gasoline fuel processor is able to start-up within 40 min and to produce the reformate gas which has 37 ~ 42 vol.%(dry basis) of $H_2$ and 0.3 vol.% of CO.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.4
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• pp.235-241
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• 2005

Thermal creep properties of the advanced zirconium fuel claddings named by HANA alloys which were developed for high burn-up application were evaluated. The creep test of HANA cladding tubes was carried out by the internal pressurization method in temperature range from 350 to $400^{\circ}C$ and in the hoop stress range from 100 to 150 MPa. Creep tests were lasted up to 800 days, which showed the steady-state secondary creep rate. The creep resistance of HANA fuel claddings was affected by final annealing temperature and various factors, such as alloying element, applied stress and testing temperature. From the results the microstructure observation of the samples before and after creep test by using TEM, the dislocation density was increased in the sample of after creep test. The Sn as an alloying element was more effective in the creep resistance than other elements such as Nb, Fe, Cr and Cu due to solute hardening effect of Sn. In case of HANA fuel claddings, the improved creep resistance was obtained by the control of final heat treatment temperature as well as alloying element.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.80-87
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• 2002

Liquefied petroleum gas (LPG) is used in spark ignition (SI) engines. Fuel injection rate of an injector is affected by fuel temperature and pressure in LPG liquid injection systems for either a multi-point-injection (MPI) or a direct injection (DI) engine. Even fuel injection conditions are varied, the air-fuel ratio should be accurately controlled to reduce exhaust emissions. In this study, a correction factor fur the fuel injection rate of an injector is derived from density ratio and pressure difference ratio. A compensation method of injected fuel amount is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI engine show that this system works well fur a full range of engine speed and load condition, and the air-fuel ratio is accurately controlled by the proposed correction factor.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.72-79
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• 2009

Recently, the internal combustion engines have focused on reducing the $CO_2$ gas in order to cope with severe regulations for fuel economy. Therefore, various new technologies have been developed. Among them, cooling system is spotlighted because it has great effect on fuel economy. In this study, we measured the friction losses of engine parts according to engine speed and oil temperature. We also obtained optimized oil temperature which has the minimum friction losses. Then, we selected optimized oil temperature range and gave informations of friction losses for each engine parts. In addition, we analyzed relationship between coolant temperature and oil temperature by using engine performance test system. From this experiment, we obtained the database for relationship between coolant temperature and oil temperature. Then, we found the optimal temperature about engine oil. We analyzed BSFC and exhaust emissions by controlling the high coolant temperture. If we controlled coolant temperature more higher, BSFC has a little difference but exhaust emissions such as THC and CO have reduced. By using these experimental results, we predicted that IC engine have more low fuel consumption and exhaust emissions by optimized cooling control strategy.

• International Journal of Aerospace System Engineering
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• v.5 no.2
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• pp.16-22
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• 2018

An analysis has been made on the performance variation due to pressure drop change at propellant supply pipes of liquid rocket engine. The objective is to compare the effectiveness of control variables to tune the liquid rocket engine performance. The mode analysis program has been used to estimate the engine performance for different modes which is realized by controlling the flow rate of propellant. The oxidizer of combustion chamber, the fuel of combustion chamber, the oxidizer of gas generator and the fuel of gas generator are the independent variables to control engine thrust, engine mixture ratio and temperature of gas generator product gas. The analysis program is validated by comparing with the powerpack test results. The error range of compared variables is order of 4%. After comparison of tuning effectiveness it is turned out that the pressure drop at oxidizer pipe of gas generator and pressure drop at combustion chamber fuel pipe and the pressure drop at the fuel pipe of gas generator can effectively tune the thrust of engine, mixture ratio of engine and temperature of product gas from gas generator respectively.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.206-211
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• 2008

In this research, combustion and spray characteristics were investigated experimentally in a constant volume chamber by applying bio-diesel fuel to a common-rail system in which precise control is available for utilizing environmentally friendly properties of bio-diesel fuel. The experiment was conducted at fuel temperatures $20^{\circ}C$ and $-20^{\circ}C$ to investigate combustion characteristics of bio-diesel fuel provoking problems in fluidity specially in a low temperature. For the visualization, the experiment was carried out under various conditions of ambient pressure, injection pressure and fuel temperature. The test was made by three different types of diesel fuels, conventional diesel, BD20 and BD100. In summary, this research aims to investigate combustion characteristics in the application of bio-diesel fuels and compare the results with performance of conventional diesel fuel. This experimental data may provide fundamentals of spray and combustion of bio-diesel fuels at a low temperature and contribute to the development of bio-diesel engines in future.