• 제목/요약/키워드: Fuel Flow

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균일한 축방향 유동에 노출된 핵 연료봉의 진동특성 분석 (Vibration Characteristics of a Nuclear Fuel Rod in Uniform Axial Flow)

  • 전상윤;서정민;김규태;박남규
    • 한국소음진동공학회논문집
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    • 제16권11호
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    • pp.1115-1123
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    • 2006
  • Nuclear fuel rods are exposed to axial flow in a reactor, and flow-induced-vibration due to the flow usually causes damage in the fuel rods. Thus a prior knowledge about dynamic behavior of a fuel rod exposed to the flow condition should be provided. This paper shows that dynamic characteristics of a nuclear fuel rod depend on axial flow velocity. Assuming small lateral displacement, the effects of uniform axial flow are investigated. The analytic results show that axial flow generally reduces fuel rod stiffness and raises its damping in normal condition. Also, the critical axial velocities which make the fuel rod behavior unstable were found. That is, solving generalized eigenvalue equation of the fuel rod dynamic system, the eigenvalues with positive real part are detected. Based on the simulation results, on the other hand, it turns out that the ordinary axial flow in nuclear reactors does not affect to stability of a nuclear fuel rod even in the conservative condition.

엔진 고공 시험에서 연료 유량 측정용 터빈 유량계의 측정 불확도 분석 (Measurement Uncertainty Analysis of a Turbine Flowmeter for Fuel Flow Measurement in Altitude Engine Test)

  • 양인영
    • 한국유체기계학회 논문집
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    • 제14권1호
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    • pp.42-47
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    • 2011
  • Measurement uncertainty analysis of fuel flow using turbine flowmeter was performed for the case of altitude engine test. SAE ARP4990 was used as the fuel flow calculation procedure, as well as the mathematical model for the measurement uncertainty assessment. The assessment was performed using Sensitivity Coefficient Method. 11 parameters involved in the calculation of the flow rate were considered. For the given equipment setup, the measurement uncertainty of fuel flow was assessed in the range of 1.19~1.86 % for high flow rate case, and 1.47~3.31 % for low flow rate case. Fluctuation in frequency signal from the flowmeter had the largest influence on the fuel flow measurement uncertainty for most cases. Fuel temperature measurement had the largest for the case of low temperature and low flow rate. Calibration of K-factor and the interpolation of the calibration data also had large influence, especially for the case of very low temperature. Reference temperature, at which the reference viscosity of the sample fuel was measured, had relatively small contribution, but it became larger when the operating fuel temperature was far from reference temperature. Measurement of reference density had small contribution on the flow rate uncertainty. Fuel pressure and atmospheric pressure measurement had virtually no contribution on the flow rate uncertainty.

유동혼합기에 의한 회전유동을 고려한 핵연료 봉의 동적 안정성해석 (Dynamic Stability Analysis of the Nuclear Fuel Rod Affected by the Swirl Flow due to the Flow Mixer)

  • 이강희;김형규;윤경호
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.641-646
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    • 2008
  • Long and slender body with or without flexible supports under severe operating condition can be unstabilized even by the small cross flow. Turbulent flow mixer, which actually increases thermal-hydraulic performance of the nuclear fuel by boosting turbulence, disturbs the flow field around the fuel rod and affects dynamic behavior of the nuclear fuel rods. Few studies on this problem can be found in the literature because these effects depend on the specific natures of the support and the design of the system. This work shows how the dynamics of a multi-span fuel rod can be affected by the turbulent flow, which is discretely activated by a flow mixer. By solving a state-space form of the eigenvalue equation for a multi-span fuel rod system, the critical velocity at which a fuel rod becomes unstable was established. Based on the simulation results, we evaluated how stability of a multi-spanned nuclear fuel rod with mixing vanes can be affected by the coolant flow in an operating reactor core.

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혼합날개의 주기적 유동교란에 따른 다점지지 연료봉의 고유치변화 (Variation of Eigenvalues of the Multi-span Fuel Rod due to Periodic Flow Disturbance by the Flow Mixer)

  • 이강희;우호길
    • 한국소음진동공학회논문집
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    • 제20권3호
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    • pp.215-222
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    • 2010
  • Long and slender body, like a fuel rod, oscillating in axial flow can be unstabilized even by the small cross flow which can be activated by the flow mixer or turbulent generator. It is important to include these effects of flow disturbance in dynamic stability analysis of nuclear fuel rod. This work shows how eigen frequency of a multi-span fuel rod can be changed by the swirl flow, which is discretely generated by a flow mixer. By solving a state-space form of the eigenvalue equation for a multi-span fuel rod system, the critical velocity at which a fuel rod becomes unstable was calculated. Based on the simulation results, we evaluated how stability of a multi-spanned nuclear fuel rod with mixing vanes can be affected by the coolant flow in an operating reactor core.

혼합기 공급방식에 따른 덤프연소기의 연소 불안정성에 관한 실험적 연구 (A Experimental Study on the Instability of Combustion in a Dump Combustor with Respect to Fuel and Air Mixing and Flow Conditions)

  • 홍정구;이민철;이은도;오광철;신현동
    • 대한기계학회논문집B
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    • 제29권8호
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    • pp.963-970
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    • 2005
  • The combustion instability of turbulent flames is the most important problem of the gas turbine combustor. Thus improved understanding of mechanisms of combustion instability is necessary for the design and operation of gas turbine combustors. In this study, the cause of the combustion instability in a rearward-step dump combustor was investigated with respect to the fuel flow modulation; choked fuel flow, unchoked fuel flow and fully premixed mixture flow. We observed various types of combustion instabilities with respect to the change of equivalence ratio, fuel flow conditions and fuel injection location. Particularly in the unchoked fuel flow condition, it was found that the oscillation time of combustion instability is strongly related to the convection time of the fuel and that the pressure fluctuation in a lab-scale combustor is highly related to the vortex and the equivalence ratio fluctuations due to fuel flow modulation and unmixedness of the fuel and air.

기체연료 엔진에서 공연비제어를 위한 흡입공기량 추정 (Estimation of Inlet Air Mass Flow for Air-Fuel Raito Control of Gaseous-Fuel Engines)

  • 심한섭;이강윤;선우명호;송창섭
    • 한국자동차공학회논문집
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    • 제9권5호
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    • pp.131-139
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    • 2001
  • Highly accurate control of the air-fuel ratio is important to reduce exhaust gas emissions of the gaseous-fuel engines. In order to achieve this purpose, inlet air mass flow must be measured exactly, and precise engine models are necessary to design engine control systems. In this paper, the effects of water vapor and gaseous fuel that change the air mass flow are studied. The effective air mass ratio is defined as the air mass flow divided by the mixture mass flow, and also it is applied to the estimation of the inlet air mass flow. The presence of the gaseous fuel and the water vapor in the mixture reduces the air partial pressure and the effective air mass ratio of the gaseous-fuel engines. The Experimental results for an LPG engine show that the estimation of the inlet ai mass flow based upon the effective air mass ratio is more accurate than that of the normal air mass flow.

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Effects of Piston Shapes and Intake Flow on the Behavior of Fuel Mixtures in a GDI Engine

  • Kang, Jeong-Jung;Kim, Duck-Jool
    • Journal of Mechanical Science and Technology
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    • 제17권12호
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    • pp.2027-2033
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    • 2003
  • The purpose of this study is to investigate the stratification of fuel vapor with different in-cylinder flow, piston cavity and injection timings in an optically accessible engine. Three different piston shapes that are F(Flat), B(Bowl) and R(Re-entrance) types were used. The images of liquid and vapor fuel were captured under the motoring condition using Laser Induced Exciplex Fluorescence technique. As a result, at early injection timing of 270 BTDC, liquid fuel was evaporated faster by tumble flow than swirl flow, where most of fuel vapor were transported by tumble flow to the lower region and both sides of cylinder for the F-type piston. At late injection timing of 90 BTDC, tumble flow appears to be moving the fuel vapor to the intake side of the cylinder, while swirl flow convects the fuel vapor to the exhaust side. The concentration of mixture in the center region was highest in the B-type piston, while fuel vapor was transported to the exhaust side by swirl flow in F and R-type pistons. At the injection timing of 60 BTDC, the R-type piston was better for stratification due to a relatively smaller bowl diameter than the others.

건물용 고분자 전해질 연료전지 금속분리판 유동장 형상 변화에 따른 산소 확산 특성에 대한 연구 (A Study on Oxygen Diffusion Characteristics According to Changes in Flow Field Shape of Polymer Electrolyte Membrane Fuel Cell Metallic Bipolar Plate for Building)

  • 박동환;손영준;최윤영;김민진;홍종섭
    • 한국수소및신에너지학회논문집
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    • 제32권4호
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    • pp.245-255
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    • 2021
  • Various studies about metallic bipolar plates have been conducted to improve fuel cell performance through flow field design optimization. These research works have been mainly focused on fuel cells for vehicle, but not fuel cells for building. In order to reduce the price and volume of fuel cell stacks for building, it is necessary to apply a metallic flow field, In this study, for a metallic flow field applied to a fuel cell for building, the effect of a change in the flow field shape on the performance of a polymer electrolyte membrane fuel cell was confirmed using a model and experiments with a down-sizing single cell. As a result, the flow field using a metal foam outperforms the channel type flow field because it has higher internal differential pressure and higher reactants velocity in gas diffusion layer, resulting in higher water removal and higher oxygen concentration in the catalyst layer than the channel type flow field. This study is expected to contribute to providing basic data for selecting the optimal flow field for the full stack of polymer electrolyte membrane fuel cells for buildings.

마이크로 가스 터빈용 연소기의 연료 노즐의 유량 분배에 관한 수치 해석적 연구 (Numerical Study on Flow Distribution of Fuel Nozzles for a Combustor in a Micro Gas Turbine)

  • 김태훈;도규형;한용식;김명배;최병일
    • 한국연소학회지
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    • 제19권4호
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    • pp.8-13
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    • 2014
  • Flow distribution of fuel nozzles for a combustor in a micro gas turbine is numerically investigated. The fuel supply system for the present study has 12 single nozzles with a diameter of several hundred micrometers. A uniform temperature distribution of a combustor outlet should be achieved for maximizing the lives of the turbine blades and nozzle guide vanes. For this, it is very important to uniformly supply fuel to a combustor. In order to investigate flow distributions of fuel nozzles, numerical models for fuel nozzles are made and solved by a commercial code, ANSYS FLUENT. An effect of a fuel nozzle diameter and fuel flow rates on flow distribution of fuel nozzles is numerically investigated. As a result, non-uniformity is increasing as a diameter of a single fuel nozzle increases. Finally, an appropriate diameter of a single fuel nozzle is suggested.

교류 흐름 방식을 적용한 암모니아 공급 고체산화물 연료전지의 성능 분석 (Performance Analysis of Ammonia-Fed Solid Oxide Fuel Cell Using Alternating Flow)

  • 쿠엔;잡반티엔;이동근;이선엽;배용균;안국영;김영상
    • 한국수소및신에너지학회논문집
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    • 제33권5호
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    • pp.557-565
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    • 2022
  • The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.