• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.1-9
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• 2020

Using kerosene and liquid oxygen, 1.5-tonf class liquid-liquid pintle injector with rectangular two-row orifice was designed and manufactured. The combustion test of the pintle injector was carried out to verify the combustion performance and combustion stability under a supercritical condition which is the actual operation condition of the liquid rocket engine. The combustion test result showed that the pintle tip was damaged by the high temperature combustion gas in the high-mixed ratio recirculation zone of the combustion chamber. To solve this problem, the insert nozzle was installed in the pintle injector to increase cooling performance at the pintle tip. As a result of the hot firing test, installation of the insert nozzle, AR and BF had a great effect on pintle tip cooling performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.135-140
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• 2010

An important goal in diesel engine research is the development of a means to reduce the emissions of nitrogen oxides (NOX). The use of a cooled exhaust gas recirculation (EGR) system is one of the most effective techniques currently available for reducing nitrogen oxides. Since Particular Matter (PM) fouling reduces the efficiency of an EGR cooler, a trade-off exists between the amount of NOX and PM emissions, especially at high engine loads. In the present study, engine dynamometer experiments have been performed to investigate the heat exchange characteristics of the stack-type EGR coolers with wave fin pitches of 3.6 and 4.6 mm. The results show that the heat exchange effectiveness is decreased as surface area decrease with pitch of 4.6 mm due to PM fouling. As surface area increase at pitch of 3.6 mm, super-cooling happens in the recirculated exhaust gas.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.769-775
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• 2008

In this study, the investigations on the dimpled type Exhaust Gas Recirculation (EGR) cooler have been focused on the high heat exchanger efficiency. To overcome low heat exchanger efficiency of general EGR cooler, the dimpled type EGR cooler was developed. It was ensured the improvement of the performance of the dimpled type EGR cooler related to the heat exchange based on a series of the experiment. These results were caused by the increase of thermal surface area in accordance with the dimple's one. The estimation model of the heat exchanger efficiency using the Effectiveness-NTU method was also developed in order to verify the validity of experimental result. Also, the program for the estimation of the heat exchanger efficiency on the EGR cooler with regard to the dimpled tube shape was developed. Resultantly, it was confirmed that the dimpled type EGR cooler could be served better performance than the conventional one in view of the heat exchanger efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.25-32
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• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• Journal of Hydrogen and New Energy
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• v.30 no.6
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• pp.593-600
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• 2019

The combustion characteristics of methane/hydrogen pre-mixed flame have been investigated with swirl stabilized flame in a laboratory-scale pre-mixed combustor with constant heat load of 5.81 kW. Hydrogen/methane fuel and air were mixed in a pre-mixer and introduced to the combustor through a burner nozzle with different degrees of swirl angle. The effects of hydrogen addition and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using particle image velocimetry (PIV), micro-thermocouples, various optical interference filters and gas analyzers to provide information about flow velocity, temperature distributions, and species concentrations of the reaction field. The results show that higher swirl intensity creates more recirculation flow, which reduces the temperature of the reaction zone and, consequently, reduces the thermal NO production. The distributions of flame radicals (OH, CH, C₂) are dependent more on the swirl intensity than the percentage of hydrogen added to methane fuel. The NO concentration at the upper part of the reaction zone is increased with an increase in hydrogen content in the fuel mixture because higher combustibility of hydrogen assists to promote faster chemical reaction, enabling more expansion of the gases at the upper part of the reaction zone, which reduces the recirculation flow. The CO concentration in the reaction zone is reduced with an increase in hydrogen content because the amount of C content is relatively decreased.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.27-34
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• 2023

Using ammonia as fuel for solid oxide fuel (SOFC) cells has become an attractive topic nowadays due to its high efficiency, environmental friendliness, and ease of storage and transportation. Several configurations of ammonia-fed SOFC systems have been proposed and investigated, demonstrating high electrical efficiency. However, to further enhance efficiency, it is crucial to understand the inefficient components of the system. The exergy concept is well-suited for this purpose, making exergetic analysis essential for ammonia-fed SOFC systems. This study conducts an exergetic analysis for three selected systems: a simple fuel cell system (FC), an anode off-gas recirculation system (RC-FC), and a recirculation system with water removal (RC-WR-FC). The results reveal that the exergetic efficiencies of the FC, RC-FC, and RC-WR-FC are 48.7%, 51.6%, and 58.4%, respectively. In all three systems, the SOFC stack is the main source of exergy destruction. However, other components with relatively low exergetic efficiency, such as the burner, air heat exchanger, and cooler/condenser, offer greater opportunities for improvement.