• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.386-391
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• 2021

Turbocharging is becoming a key technology for both diesel and gasoline engines. Regarding gasoline engines, turbocharging can help reduce carbon dioxide (CO2) emissions when used in conjunction with other technologies. This paper presents measurements of the turbine efficiency of pulsating flow in a twin-scroll turbocharger for gasoline engines. A cold gas test bench with a pulse generator was manufactured. The turbine efficiencies were calculated using the measured data of the instantaneous pressure and temperature of the inlet and exit of the turbine. The measurements were carried out at turbine speeds from 60,000 to 100,000 rpm under a pulsating flow of 25.0 Hz and 33.0 Hz. The turbine efficiencies ranged from 0.517 to 0.544. At the pulse frequency, 33.3 Hz, the variations in efficiency were 7.7% and 2.6% at turbine speeds of 60,000 rpm and 100,000 rpm, respectively. The turbine efficiency of the pulsating flow compared to those of steady flow was 7.0% and 3.0% lower at a turbine speed of 60,000 rpm and 100,000 rpm, respectively. The pulsating flow deteriorated the turbine efficiency, but the effects of pulsating flow decreased with increasing turbine speed.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.263-266
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• 2002

The KSR-III developed by KARI is the first rocket vehicle which is adopting the liquid propellant rocket engine system in Korea. Not only the engine itself, but also the propellant feeding system is one of the most important component in liquid rocket vehicle. In this paper, the authors are intended to introduce the multi-purpose test facility(PTA-II Test Facility) which is constructed for the variety of tests on KSR-III feeding system(single component tests, verification tests, cold flow tests and combustion tests). With the results of these tests, we can identify the characteristics of rocket feeding system and decide the optimum setting values of feeding system for the successful flight.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1412-1420
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• 2018

An experiment was performed using the large-scale test facility (LSTF), which simulated a 1% vessel upper head small-break loss-of-coolant accident with an accident management (AM) measure under an assumption of total-failure of high-pressure injection (HPI) system in a pressurized water reactor (PWR). In the LSTF test, liquid level in the upper head affected break flow rate. Coolant was manually injected from the HPI system into cold legs as the AM measure when the maximum core exit temperature reached 623 K. The cladding surface temperature largely increased due to late and slow response of the core exit thermocouples. The AM measure was confirmed to be effective for the core cooling. The RELAP5/MOD3.3 code indicated insufficient prediction of primary coolant distribution. The author conducted uncertainty analysis for the LSTF test employing created phenomena identification and ranking table for each component. The author clarified that peak cladding temperature was largely dependent on the combination of multiple uncertain parameters within the defined uncertain ranges.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.405-414
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• 1996

In this paper, the unsteady 2-dimensional turbulent flow model for thermal stratification in a pressurizer surge line of PWR plant is proposed to numerically investigate the heat transfer and flow characteristics. The turbulence model is adapted to the low Reynolds number K-$\varepsilon$ model (Davidson model). The dimensionless governing equations are solved by using the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The results are compared with simulated experimental results of TEMR Test. The time-dependent temperature profiles in the fluid and pipe nil are shown with the thermal stratification occurring in the horizontal section of the pipe. The corresponding thermal stresses are also presented. The numerical result for thermal stratification by the outsurge during heatup operation of PWR shows that the maximum dimensionless temperature difference is about 0.83 between hot and cold sections of pipe well and the maximum thermal stress is calculated about 322MPa at the dimensionless time 28.5 under given conditions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.111-114
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• 2009

A catalyst ignitor of small thrust engine using hydrogen peroxide and kerosene was designed and fabricated, which confirmed mass flow rate for design pressure through the water cold-flow test in this study. In order to investigate ignition performance, it was changed that mixture ratio for kerosene mass flow rate in a position which heat of hydrogen peroxide decomposition comes to a steady state. And we confirmed stable ignition property in a wide range of mixture ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.392-396
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• 2012

Experimental and computational study for steady-state pintle driven nozzle throat flow are carried out by changing four pintle shape. Results show that thruster performance is influenced by pintle shape greatly. This attributes to the distorted throat area and chamber pressure change as the pintle shape and its penetration.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.35-41
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• 2009

Both the nozzle expansion ratio and the chamber pressure are simultaneously and continuously changed according to pintle movement, resulting in a different internal flow structure and flow separation characteristics. In this paper, the pintle position effect on nozzle flow structure and separation phenomena is analyzed by experimental-aided Computational Fluid Dynamic(CFD). Among the turbulent models for RANS(Reynold Averaged Navier Stokes) in Fluent, Spalart-Allmaras model is better agreement with the nozzle wall pressure distribution attained by cold-flow test than other models. And even if a conical nozzle is used, there is a shock structure similar to cap-shock pattern mainly occurred in contoured or shaped optimized nozzle because of internal shock generated from pintle tip flow separation.

• Nuclear Engineering and Technology
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• v.32 no.2
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• pp.108-127
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• 2000

Hot leg break LBLOCA(Large Break LOCA) had a potential to be a containment maximum pressure accident in YGN3&4, which was induced from excessive conservatism in the CE analysis methodology of mass and energy release. This study conducted mass and energy release experiment for the hot leg break LBLOCA during post blowdown with an integral test facility, SNUF(Seoul National University Facility). This facility simulated YGN 3&4 with volume ratio of 1/1140 based on Ishii's three level scaling. Experiment showed that SI(Safety Injection) water refilled cold leg first and core later. SI water was vaporized in the core, which resulted in the repressurization of reactor. This increase of pressure drove the water in cold leg to flow up half height of U tubes. However, since the water was drained back soon, the release through the SG side broken section by evaporation was negligibly small. This study also provided experimental assessment of RELAP5 results by KAERI for the release through the SG side broken section.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.3
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• pp.562-568
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• 1998

Various diagnostic methods, such as electric pulp test, cold test, test cavity etc., have been used to determine the pulp vitality. At least two or more methods should be used with supplemental information to diagnose each case because using one method doesn't provide sufficient accuracy. These conventional methods have depended on nervous responses, but Laser Doppler Flowmeter determines the pulp vitality by measuring pulpal blood flow. In this case, we tested the vitality of the traumatized teeth with incomplete root apices and autotransplanted teeth with conventional methods and Laser Doppler Flowmeter. Conventional methods, such as electric pulp test and cold test can produce various responses according to the development state of the pulpal nerve and the sensory threshold of the patient. But, Laser Doppler Flowmeter has a lower false response rate than any other pulp vitality test methods and it can determine the vitality somewhat earlier than the other method.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1270-1275
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• 2004

Flow condensation heat transfer coefficients(HTCs) of R22 and R134a were measured on horizontal aluminum multi-channel tube. The experimental apparatus was composed of three main parts ; a refrigerant loop, a water loop and a water-ethylene glycol loop. The test section in the refrigerant loop was made of aluminum multi-channel tube of 1.4 mm hydraulic diameter and 0.53 m length. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. The data scan vapor qualities $(0.1{\sim}0.9)$, mass flux ($200{\sim}400$ $kg/m^{2}s$) and heat flux ($7.3{\sim}7.7$ $kW/m^{2}$) at $40{\times}0.2^{\circ}C$ saturation temperature in small hydraulic diameter tube. It was found that some well-known previous correlations were not suitable for multichannel tube. So, It must develop new correlations for multi-channel tubes.