• Title/Summary/Keyword: Flow-Ratio

Search Result 5,911, Processing Time 0.033 seconds

Intake Flow Characteristics with SCV Open Ratio in a 4-Valve Direct Diesel Engine (4밸브 직분식 디젤엔진의 SCV 개구율에 따른 흡입유동특성)

  • 최승환;전충환;장영준;이진욱
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.7 no.7
    • /
    • pp.66-75
    • /
    • 1999
  • Many researchers have developed the measurement technique of in-cylinder flow. Recently, there are lots of studies on steady flow with different SCV geometries. In this study the flow characteristics of four-valve cylinder head were examined in a steady test rig for different SCV open ratios. Each swirl ratio of several SCV angle was quantified by swirl impulse meter and 2D-LDV measurement. The results showed that the swirl ratio was controlled between 2.3 and 3.8 based on SCV angles. The velocity distributions of in-cylinder flow field were measured by 2-D LDV test and visualized swirl and tumble flow pattern at different positions. In this engine , we found out that the swirl was dominant flow.

  • PDF

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
    • /
    • v.12 no.5
    • /
    • pp.80-87
    • /
    • 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 Comparison of Accuracy Between a Turbine and an Orifice Meter in the Field (현장여건에 따른 터빈 유량계와 오리피스 유량계의 정확도 비교)

  • An, Seung-Hee;Her, Jae-Young
    • 유체기계공업학회:학술대회논문집
    • /
    • 1999.12a
    • /
    • pp.97-105
    • /
    • 1999
  • Orifice flow meters are frequently used for measuring gas flow in gas industry. However, to insure the accuracy of the measurement, a certain length of the meter run at the upstream of the flow meter is required. The objective of this study is to analyze flow measurement errors of the orifice flow meter quantitatively for shorter lengths of the meter runs than those suggested in the standard manuals with variation of diameter ratio( $\beta$ ratio) and flow rate. The test results showed that the flow measurement errors of the orifice meter were inversely proportional to the diameter ratio. In other words, when the diameter ratio is 0.3 and 0.7, the measurement error is $-7.3\%$ and $-3.5\%$, respectively. the main reason of the measurement error is due to the swirl effect from the configuration of the meter run at the upstream of the flow meter. In case the length of the meter run is shorter than that suggested in the standard manuals, the swirl effect is not removed completely and it affects the flow meter's performance. As mentioned above, the less the pipe diameter ratio, the more the flow measurement error. It means that the swirl effect on the orifice meter increases as the $\beta$ ratio decreases.

  • PDF

A Study on Flow Characteristics of Branch Type Sparger in Drain Tank for Depressurization (감압용 배수탱크내의 분기형 증기분사기의 유동특성에 관한 연구)

  • 김광추;박만흥;박경석
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.13 no.5
    • /
    • pp.356-367
    • /
    • 2001
  • A numerical analysis on branch type sparger in drain tank for depressurization is performed to investigate the flow characteristics due to the change of design factor. As the result of this study, sparger\\`s flow resistance coefficient(K) is 3.53 at the present design condition when engineering margin for surface roughness is considered as 20%, and flow ratio into branch pipe ($Q_s/Q_i$) is 0.41. The correlation for calculating flow resistance coefficients as design factor is presented. Flow resistance coefficient is increased as section area ratio of branch pipe for main pipe and outlet nozzle diameter of main pipe decreasing, but the effects of branch angle and inlet flow rate of main pipe are small. As the change rate of ($Q_s/Q_i$)becomes larger, the change rate of flow resistance coefficient increases. The rate of pressure loss has the largest change as section area ratio changing. The condition of maximum flow resistance in sparger is when the outlet nozzle diameter ratio of main pipe ($D_e/D_i$) is 0.167, the section area ratio ($A_s/A_i$) is 0.1 and the branch angle ($\alpha$) is 55^{\circ}$.

  • PDF

A Study on the Flow Characteristics and Engine Performance with Swirl Ratio Variance of Intake Port (흡기포트 선회비 변경에 따른 유동특성 및 엔진성능에 관한 연구)

  • Yoon, Jun-Kyu;Cha, Kyung-Ok
    • Proceedings of the KSME Conference
    • /
    • 2000.04b
    • /
    • pp.899-905
    • /
    • 2000
  • The characteristics of air flow and engine performance with swirl ratio variance of intake port In a turbocharged DI diesel engine was studied in this paper. The intake port flow is important factor which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. The swirl ratio for ports was modified by hand-working and measured by impulse swirl meter. For the effects on performance and emission, the brake torque and brake specific fuel consumption were measured by engine dynamometer and NOx, smoke were measured by gas analyzer and smoke meter. As a result of steady flow test, when the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased. And as the swirl ratio is increased, the mean flow coefficient is decreasing, whereas the gulf factor is increasing. Also, through engine test its can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, injection timing and compression ratio.

  • PDF

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
    • /
    • v.29 no.5 s.236
    • /
    • pp.554-560
    • /
    • 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.

Dependence of the Structural, Electrical, and Optical Properties of Al-doped ZnO Films for Transparent Conductors on the Process Atmosphere in Magnetron Sputtering (마그네트런 스퍼터링법으로 증착한 투명전극용 Al도핑된 ZnO의 공정 분위기에 따른 구조적, 전기적, 광학적 특성비교)

  • Yim, Keun-Bin;Lee, Chong-Mu
    • Korean Journal of Materials Research
    • /
    • v.15 no.8
    • /
    • pp.518-520
    • /
    • 2005
  • Effects of the $O_2/Ar$ flow ratio in the sputtering process on the crystallinity, surface roughness, carrier concentration, carrier mobility, and optical properties of Al-doped ZnO thin films deposited on sapphire (001) substrates by RF magnetron sputtering were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM of the (002) XRD intensity peak for the $O_2/Ar$ flow ratio of 0.5. The (101)peak also appeared and the degree of preferred orientation decreased as the $O_2/Ar$ flow ratio increased from 0.5 to 1.0. AFM analysis results showed that the surface roughness was lowest at the $O_2/Ar$ flow ratio of 0.5 and tended to increase owing to the increase of the grain size as the $O_2/Ar$ flow ratio increased further. According to the Hall measurement results the carrier concentration and carrier mobility of the fan decreased and thus the resistivity increased as the $O_2/Ar$ flow ratio increased. The transmittance of the ZnO:Al film deposited on the glass substrate was characteristic of a standing wave. The transmittance increased as the $O_2/Ar$ flow ratio in-RF magnetron sputtering increased up to 0.5. Considering the effects of the $O_2/Ar$ flow ratio on the surface roughness, electrical resistivity and transmittance properties of the ZnO:Al film the optimum $O_2/Ar$ flow ratio was 0.5 in the RF magnetron sputter deposition of the ZnO:Al film.

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
    • /
    • v.9 no.5
    • /
    • pp.131-139
    • /
    • 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.

  • PDF

Numerical Study on Double-Diffusive Convection in a Stratified Trapezoidal Enclosure (성층화된 사다리꼴 용기내에서의 이중확산유동에 관한 수치해석)

  • 현명택
    • Journal of Ocean Engineering and Technology
    • /
    • v.6 no.2
    • /
    • pp.143-150
    • /
    • 1992
  • Numerical simulation is made of a stably stratified salt-water solution due to lateral heating in an equilateral trapezoidal enclosure using boundary-fitted coordinate in grid generation. Results show four types of the global fluid pattern depending on the buoyancy ratio in the enclosure, i.e., unicell flow pattern for the low buoyancy ratio, layered flow pattern for the increasing buoyancy ratio, layered flow pattern with stagnant zone for the relatively high buoyancy ratio and stagnant flow pattern for the much higher buoyancy ratio.

  • PDF

Performance Optimization of a Hybrid Ground Source Heat Pump According to Secondary Flow Distribution Ratio between the Ground and the Supplemental Loop (지중 및 보조루프의 2차 유체 유량 분배비를 통한 하이브리드 지열히트펌프의 성능 최적화 연구)

  • Lee, Joo-Seong;Park, Hong-Hee;Kim, Won-Uk;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.24 no.2
    • /
    • pp.102-110
    • /
    • 2012
  • The objective of this study is to improve the performance of a hybrid ground source heat pump (HGSHP) by optimizing the flow distribution ratio of secondary fluid flow rate between a ground loop and a supplemental loop. Initially, a conventional ground source heat pump (GSHP) was tested to determine an optimum flow rate of the secondary fluid. Based on the selected optimum value, the HGSHP was also tested by varying the flow distribution ratio of the secondary fluid flow rate between the ground loop and the supplemental loop, such as 9:1, 7:3, 5:5, and 3:7. The results showed that the optimum flow distribution ratio of the secondary fluid flow rate was 7:3. The COP of the HGSHP was improved by 19% over the GSHP at a flow distribution ratio of 7:3 and an entering water temperature of $40^{\circ}C$.