• Title, Summary, Keyword: Fuel Flow

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

  • Jeon, Sang-Youn;Suh, Jung-Min;Kim, Kyu-Tae;Park, Nam-Gyu
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.11
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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.

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

  • Lee, Kang-Hee;Kim, Hyung-Kyu;Yoon, Kyung-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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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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Measurement Uncertainty Analysis of a Turbine Flowmeter for Fuel Flow Measurement in Altitude Engine Test (엔진 고공 시험에서 연료 유량 측정용 터빈 유량계의 측정 불확도 분석)

  • Yang, In-Young
    • The KSFM Journal of Fluid Machinery
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    • v.14 no.1
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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.

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

  • Lee, Kang-Hee;Woo, Ho-Kil
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.3
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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.

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

  • Hong, Jung-Goo;Lee, Min-Chul;Lee, Uen-Do;Oh, Kwang-Chul;Shin, Hyun-Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.8
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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.

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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    • v.17 no.12
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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.

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

  • 심한섭;이강윤;선우명호;송창섭
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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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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Numerical Study on Flow Distribution of Fuel Nozzles for a Combustor in a Micro Gas Turbine (마이크로 가스 터빈용 연소기의 연료 노즐의 유량 분배에 관한 수치 해석적 연구)

  • Kim, Taehoon;Do, Kyu Hyung;Han, Yong-Shik;Kim, Myungbae;Choi, Byung-Il
    • Journal of the Korean Society of Combustion
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    • v.19 no.4
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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.

Low Temperature Fluidity Performance Evaluation of Composited Package Fuel Heater for Diesel Cars (디젤차량용 통합연료히터의 저온유동성 성능평가)

  • Lee, Jeong-Hwa;Park, Hyung-Won;Lee, Woong-Su;Lee, Young-Jea;Lee, Bo-Hee;Yoon, Dal-Hwan
    • Journal of IKEEE
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    • v.18 no.1
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    • pp.152-158
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    • 2014
  • It is very important to supply the diesel fuel from fuel tank to combustion chamber in case of cold start procedure. the paraffin hydrocarbons are easily solidified at low fuel temperature and it can be blocking the fuel supply to the high pressure fuel pump. In order to reduce the fuel crystallization (Waxing), it have been used to develop not only cold flow additives but also the proper mounting design of fuel filter. Block heater in the fuel filter assembly have been also contained to improve the cold start and prevent blocking the fuel supply in Common Rail Direct Injection System. we can obtain the fuel pressure drop and fuel flow rate, power consumption of fuel heater to have the cold flow evaluation test with the saperated and composited fuel heater at the low ambient temperature, Due to evaluating cold flow performance of two block heater, we knew that composited package fuel heater was the excellent cold flow performance compared to separated type and obtained the parameters of cold flow.

An Engine Model of a Heavy-Duty Compressed Natural Gas Engine for Design of an Air-Fuel Ratio Controller (대형천연가스차량의 공연비제어기 설계를 위한 엔진모델)

  • 심한섭;이태연
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.12 no.5
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    • pp.80-87
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    • 2003
  • Air partial pressure ratio and inlet air mass flow are influenced by water vapor and gaseous fuel in mixture on Compressed Natural Gas (CNG) engines. In this paper, the effects of the water vapor and the gaseous fuel that change the air mass flow and the air-fuel ratio are studied. Effective air mass ratio is defined as the air mass flow divided by mixture mass flow, and also it is applied to the estimation of the inlet air mass flow and the air-fuel ratio. 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 CNG engines. The experimental results for the CNG engine show that estimation of the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal mode.