• Title/Summary/Keyword: Mass Flow Ratio

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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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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.

A Study on the Heat Recovery Performance of Water Fludized-Bed Heat Exchanger (물유동층 열교환기의 열회수성능 연구)

  • 김한덕;박상일;이세균
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.8
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    • pp.690-696
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    • 2003
  • This paper presents the heat recovery performance of water fluidized-bed heat exchanger. Temperature and humidity ratio of waste gas are considered as important parameters in this study. Therefore, the heat recovery rate through water fluidized-bed heat exchanger for exhaust gases with various temperatures and humidity ratios can be estimated from the results of this study. Mass flow ratio (the ratio of mass flow rate of water to that of gas) and temperature of inlet water are also considered as important operating variables. Increase of heat recovery rate can be obtained through either high mass flow ratio or low temperature of inlet water with resultant low recovered temperature. The heat recovery performance with the mass flow ratio of about up to 10 has been investigated. The effect of number of stages of water fluidized-bed on the heat recovery performance has been also examined in this study.

Characteristics of T-phase flow distribution and pressure drop in a horizontal T-type evaporator tube (수평 T형 증발관내 2상류의 유량분배 및 압력강하 특성)

  • 박종훈;조금남;조홍기
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.5
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    • pp.658-668
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    • 1999
  • The objective of the present study is to investigate the effect of experimental parameters on the hydrodynamic characteristics in a horizontal tee-type evaporator using R-22. The experimental apparatus consisted of an unheated tee-type test section, a liquid-vapor separator, a preheated, mass flow meters, a plate heat exchanger, pump, and other measurement devices. The experimental parameters were mass flux(500 and 600kg/$m^2$s), inlet quality(0.1~0.3) and separation ratio(0.3~0.7). Absolute pressure at the inlet of the test section was 0.652 MPa. The branch-to-inlet inner diameter ratio was 0.61. Pressure gradient at the branch section was larger than that at the run section at the same separation ratio. Pressure drop per unit length increased at the run section and decreased at the branch section as the separation ratio increased. Pressure drop predicted by the separated flow model agreed with experimental data within -35 to +16%. Generally, predicted values showed similar trend with the data. Mass flow ratio of vapor refrigerant was affected by the inlet quality more than the mass flux.

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Mass Transfer Characteristics of Vertical Two-Phase Flows with Orifice Nozzle (오리피스 노즐 수직 2 상 유동의 물질전달 특성)

  • Kim, Dong Jun;Yang, Hei Cheon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.10
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    • pp.817-824
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    • 2015
  • Experiments were carried out to investigate the flow and mass transfer characteristics of an orifice nozzle. Measurements of primary and suction flow rates, dissolved oxygen concentration, and electric power were obtained. Vertically injected mixed-jet images were captured by a direct visualization technique with a high speed camera unit. The mass ratio, volumetric mass transfer coefficient, and mass transfer performance were calculated using the measured data. As the primary flow pressure increases, the mass ratio decreases slightly, while the volumetric mass transfer coefficient and electric power increase. As the primary flow pressure increases and the mass ratio decreases, the mass transfer rate increases because of the fine bubbles and wider distribution of the bubbles.

Effect of Orifice Nozzle Design and Input Power on Two-Phase Flow and Mass Transfer Characteristics (2 상 유동 및 물질전달 특성에 미치는 오리피스 노즐형상과 소요동력의 영향)

  • Yang, Hei Cheon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.4
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    • pp.237-243
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    • 2016
  • It is necessary to investigate the input power as well as the mass transfer characteristics of the aeration process in order to improve the energy efficiency of an aerobic water treatment. The objective of this study is to experimentally investigate the effect of orifice nozzle design and input power on the flow and mass transfer characteristics of a vertical two-phase flow. The mass ratio, input power, volumetric mass transfer coefficient, and mass transfer efficiency were calculated using the measured data. It was found that as the input power increases the volumetric mass transfer coefficient increases, while the mass ratio and mass transfer efficiency decrease. The mass ratio, volumetric mass transfer coefficient, and mass transfer efficiency were higher for the orifice configuration with a smaller orifice nozzle area ratio. An empirical correlation was proposed to estimate the effect of mass ratio, input power, and Froude number on the volumetric mass transfer coefficient.

EFFECT OF ASPECT RATIO ON SLIP FLOW IN RECTANGULAR MICROCHANNELS

  • Islam, Md.Tajul;Lee, Yeon-Won
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2803-2810
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    • 2007
  • Three dimensional numerical studies were carried out to investigate the effect of aspect ratio on gas slip flow in rectangular microchannels. We focused on aspect ratio effect on slip velocity, pressure distribution and mass flow rate. As aspect ratio decreases the wall slip velocity also decreases. As a result nonlinearity of pressure distribution increases. The slip velocities on sides and top/bottom walls are different and this difference decreases with increasing aspect ratio. These two velocities are equal when aspect ratio is 1. The ratios of slip mass flow rate over noslip mass flow rate increases with increasing aspect ratios.

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Performance Analysis of a Seawater Ice Machine Applied Two-stage vapor compression refrigeration system for Various Refrigerants (2단 증기 압축식 냉동시스템을 적용한 해상용 제빙장치의 냉매에 따른 성능 분석)

  • Yoon, Jeong-In;Son, Chang-Hyo;Heo, Seong-Kwan;Jeon, Min-Joo;Jeon, Tae-Young
    • Journal of Power System Engineering
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    • v.20 no.2
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    • pp.85-90
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    • 2016
  • Coefficient of performance (COP) for two-stage compression system is investigated in this paper to develop seawater ice machine. The system performance is analyzed with respect to degrees of superheating and subcooling, condensing and evaporating temperatures, compression and mechanical efficiencies and mass flow ratio in an inter-cooler. The main results are summarized as follows : The COP of the system grows when the mass flow ratio, subcooling degree and evaporating temperature edge up. Contrariwise, the system performance descends in case that superheating degree and condensing temperature increase. The most effective factor for the COP is the mass flow rate ratio. Each refrigerant has different limitation for a value of the mass flow ratio in the inter-cooler because of difference in material property.

Shower-Head Film Cooling on the Leading Edge of a Turbine Blade: Measurements of Local Blowing Ratio and Flow Visualizations (터빈 블레이드 선단에서의 샤워헤드 막냉강 - 국소분사율 측정 및 유동의 가시화 -)

  • Jeong, Chul Hee;Lee, Sang Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.3
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    • pp.419-430
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    • 1999
  • Measurements of local blowing ratio and ammonia-diazo flow visualizations have been conducted for a shower-head film cooling on a first-stage turbine stator. In this study, six rows of normal holes are drilled symmetrically on the semicircular leading edge of a simulated blunt body. The measurements show that for an average blowing ratio based on freestream velocity, M, of 0.5, local average mass flow rate through the first two rows of the holes is less than those through the second and third two rows of the holes, and the fraction of mass flow rate through the first two rows to total mass flow rate has a tendency to increase with the increment of M. The flow visualizations reveal that the injection through the first two row results in inferior film coverage even In the case of M = 0.5, meanwhile the row of holes situated at farther downstream location provides higher film-cooling performances for all tested M. This is because film-cooling effectiveness depends on local mainflow velocity at the hole location as well as the mass flow rate through each row.

An Experimental Study of the Variable Sonic/supersonic Ejector Systems (가변형 음속/초음속 이젝터 시스템에 관한 실험적 연구)

  • Lee Jun Hee;Kim Heuy Dong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.5 s.236
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    • pp.554-560
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    • 2005
  • A new method to improve the efficiency of a hydrogen fuel cell system was introduced by using variable sonic/supersonic ejectors. To obtain the variable area ratio of the nozzle throat to ejector throat which controls the mass flow rate of the suction flow, the ejectors used a movable cylinder inserted into a conventional ejector-diffuser system. Experiments were carried out to understand the flow characteristics inside the variable ejector system. The secondary mass flow rates of subsonic and supersonic ejectors were examined by varying the operating pressure ratio and area ratio. The results showed that the variable sonic/supersonic ejectors could control the recirculation ratio by changing the throat area ratio, and also showed that the recirculation ratio increased fur the variable sonic ejector and decreased for the variable supersonic ejector, as the throat area ratio increases.