연소실 압력변동과 2차 연료 분사가 스월 화염에서 화염안정화와 배출 특성에 미치는 영향

김종률(Jong-Ryul Kim),최경민(Gyung-Min Choi),김덕줄(Duck-Jool Kim) 한국연소학회 2007 KOSCOSYMPOSIUM논문집 Vol.- No.-

Influence of changing combustor pressure on flame stabilization and emission index in the swirl-stabilized flame was investigated The combustor pressure was controlled by suction fan at combustor exit. Pressure index (P=Pabs/Patm), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, respectively, was controlled in the range of 0.7~1.3 for each equivalence ratio conditions. The flammable limits of swirl flames were largely influenced by changing combustor pressure and they showed similar tendency with laminar flames. NOx emission index decreased with decreasing pressure index for overall equivalence ratio conditions. R.m.s. of pressure fluctuations is increased with decreasing combustor pressure. This flame fluctuation caused incomplete combustion, hence CO emission index increased. These oscillating flames were measured by simultaneous CH chemiluminescence time-series visualization and pressure fluctuation measurement.

Investigation on characteristics of pressure fluctuation in a centrifugal pump with clearance flow

Lulu Zheng,Xiaoping Chen,Wei Zhang,Zu-chao Zhu,Jinglei Qu,Mengmeng Wang,Xiaojie Ma,Xueli Cheng 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9

Clearance flow has great impact on pressure fluctuation of centrifugal pumps. Numerical calculations are performed to study the pressure fluctuation characteristics of centrifugal pump with wear ring clearance, especially in the regions of interaction between main flow and clearance flow (IMC) and clearance. The accuracy of numerical calculations is illustrated by comparing the experiments of performance and pressure fluctuation. Results show that, in clearance region the pressure fluctuation is still governed by blade passing frequency (f BPF ). Its amplitude of dominate frequency of pressure fluctuation becomes larger as the probe approaches the impeller exit. In IMC region, the pressure fluctuation at impeller outlet is dominated by f BPF . However, the dominate frequency at the entrance of impeller is less than f BPF . In addition, as the flow rate increased, the amplitude of dominate frequency of pressure fluctuation increases at impeller entrance, whereas an inverse trend is observed at wear ring clearance region.

A Study on Fluctuating Pressure Load on High Speed Train Passing through Tunnels

Seo Sung-Il,Park Choon-Soo,Min Oak-Key The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.

Wind tunnel study on fluctuating internal pressure of open building induced by tangential flow

Sheng Chen,Peng Huang,Richard G. J. Flay 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.2

This paper describes a wind tunnel test on a 1:25 scale model of TTU building with several adjustable openings in order to comprehensively study the characteristics of fluctuating internal pressures, especially the phenomenon of the increase in fluctuating internal pressures induced by tangential flow over building openings and the mechanism causing that. The effects of several factors, such as wind angle, turbulence intensity, opening location, opening size, opening shape and background porosity on the fluctuating internal pressures at oblique wind angles are also described. It has been found that there is a large increase in the fluctuating internal pressures at certain oblique wind angles (typically around 60° to 80°). These fluctuations are greater than those produced by the flow normal to the opening when the turbulence intensity is low. It is demonstrated that the internal pressure resonances induced by the external pressure fluctuations emanating from flapping shear layers on the sidewall downstream of the windward corner are responsible for the increase in the fluctuating internal pressures. Furthermore, the test results show that apart from the opening shape, all the other factors influence the fluctuating internal pressures and the internal pressure resonances at oblique wind angles to varying degrees.

A Study on Fluctuating Pressure Load on High Speed Train Passing through Tunnels

Sung-Il Seo,Choon-Soo Park,Oak-Key Min 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.4

The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.

Numerical investigation of three-dimensional cavitation evolution and excited pressure fluctuations around a twisted hydrofoil

Bin Ji,Xianwu Luo,Yulin Wu,Kazuyoshi Miyagawa 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

Unsteady cavitating turbulent flow around a twisted hydrofoil was analyzed to illustrate the physical mechanism of the cavitygeneratedpressure fluctuations. The numerical simulations of cavitating flow were based on the Partially-Averaged Navier-Stokes(PANS) method and a mass transfer cavitation model. The validity of PANS model has been evaluated and confirmed in cavitation simulationsby present authors using three different cases, 2D hydrofoil (Ji et al. 2012 [37]), 3D hydrofoil (Ji et al. 2013 [31]) and marine propeller(Ji et al. 2012 [38]), which shows that the PANS model with fk = 0.2 and fe = 1 can obtain more accurate estimates of unsteadycavitating flows with large-scale fluctuations at a reasonable cost. In present paper we intended to shed light on the physical process responsiblefor the pressure fluctuations excited by cavitation. The cavity volume was analyzed to illustrate the relationship between thecavitation evolution and the pressure fluctuations. The results show that the cavity volumetric acceleration curve tracks remarkably wellwith the main features of the time-dependent pressure fluctuations except for the high frequency component. Thus, the cavity volumetricacceleration is the main source of the excited pressure fluctuations by cavitation. It is noted that the cavitation induced pressure fluctuationsare transmitted along the suction surface of the hydrofoil and are synchronized with those on the pressure surface at the midplane ofthe twisted hydrofoil. Further, the pressure fluctuations on the pressure surface decrease towards the center from both the leading andtrailing edges of the hydrofoil, with a minimum at 60% chord length from the leading edge.

Effect of cohesive powders on pressure fluctuation characteristics of a binary gas-solid fluidized bed

Liping Wei,Youjun Lu,Jianbo Zhu,Guodong Jiang,Jun Hu,Haipeng Teng 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.10

The effect of cohesive particles on the pressure fluctuations was experimentally investigated in a binary gassolid fluidized bed. The pressure fluctuation signals were measured by differential pressure sensors under conditions of various weight percentages of cohesive particles. The cohesive particles increased the fixed bed pressure drop per unit height and decreased the minimum fluidization velocity. The Wen & Yu equation well predicts the minimum fluidization velocity of the binary system. The addition of cohesive particles slightly decreased the bubble size in bubbling flow regime when the cohesive particles and the coarse particles mixed well, while the bubble size greatly decreased when the cohesive particles agglomerated on the bed surface. The time series of pressure fluctuations was analyzed by using the methods of time domain, frequency domain and wavelet transformation. The normalized standard deviation of pressure fluctuations decreased with increasing weight percentages of cohesive particles. A wide bandwidth frequency of 0 to 1Hz got narrower with a single peak around 0.6Hz with an increase in proportion of the cohesive particles. The meso-energy and micro-energy of pressure fluctuations were decreasing with increasing cohesive particles proportions, which indicated that adding cohesive particles could reduce the energy dissipation of bubble and particle fluctuations.

Study on dynamic characteristics of the bladder fluid pulsation attenuator based on dynamic mesh technology

Qunwei Zhu,Yongxiang Zhang,Danchen Zhu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3

Fluid-flow and pressure fluctuation are main causes of vibration and noise in liquid-conveying pipeline. As a crucial auxiliary component of liquid-conveying pipeline, the bladder pressure fluctuation attenuator plays an important role in absorbing fluctuations. According to the working condition, reasonable selection of attenuator parameters can give full play to the maximum efficiency of the attenuator so as to reduce pressure fluctuation of the pipeline. Based on the stress model of the attenuator, the mathematical and simulation models of the attenuation device are established by suitable hypothesis and simplification, and based on the calculation and physical models provided by FLUENT software, the movement of bladder was simulated by dynamic mesh and UDF (user-defined function). The absorption effect of attenuator on pipeline pressure fluctuation was investigated under different inflating pressures and frequencies. The results show that reasonable selection of initial pressure of the attenuator can effectively reduce the pressure fluctuation of pipeline fluid. Compared with the theoretical analysis results, the simulation results are more close to the experimental results, and the validity of the simulation model is verified, and a method and new idea are provided for the future study of the parameters of the bladder pressure fluctuation attenuator.

EFFECT OF OUTDOOR PRESSURE FLUCTUATIONS ON NATURAL VENTILATION IN A ROOM WITH TWO OPENINGS

Han, Hwa-Taik,Kim, Jung-Kyung,Han, Chang-Ho 대한설비공학회 2012 International Journal Of Air-Conditioning and Refr Vol.20 No.2

We investigated the effects of outdoor pressure fluctuations on natural ventilation in a room with two openings. One opening is exposed to an oscillating outdoor pressure and the other is exposed to a fixed neutral pressure. The ventilation airflow rate depends on the amplitude and period of the outdoor pressure fluctuations, the room volume, and the sizes of the openings. Dimensionless parameters are derived from the governing equations that determine indoor pressure responses due to outdoor pressure fluctuations. The pressure responses and the airflow rates through the openings are obtained using a fourth-order Runge-Kutta method. The flow regions are categorize into a synchronized region, an opening resistance region, and a transition region, depending on the dimensionless parameters. Applications are considered using an example building space to investigate the effective air change rates depending on the size of the openings and the period of wind pressure fluctuations.

Effect of Outdoor Pressure Fluctuations on Natural Ventilation in a Room with Two Openings

한화택,김중경,CHANG-HO HAN 대한설비공학회 2012 International Journal of Air-Conditioning and Refr Vol.20 No.2

We investigated the effects of outdoor pressure fluctuations on natural ventilation in a room with two openings. One opening is exposed to an oscillating outdoor pressure and the other is exposed to a fixed neutral pressure. The ventilation airflow rate depends on the amplitude and period of the outdoor pressure fluctuations, the room volume, and the sizes of the openings. Dimensionless parameters are derived from the governing equations that determine indoor pressure responses due to outdoor pressure fluctuations. The pressure responses and the airflow rates through the openings are obtained using a fourth-order Runge-Kutta method. The flow regions are categorized into a synchronized region, an opening resistance region, and a transition region, depending on the dimensionless parameters. Applications are considered using an example building space to investigate the effective air change rates depending on the size of the openings and the period of wind pressure fluctuations.