• 한국자동차공학회논문집
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• 제4권3호
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• pp.92-101
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• 1996

In a gasoline engine, the characteristics of air flow is very important not only for the design of the intake system geometry bout also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement of the induction air mass. In this study, an air flow rate measurement was conducted by using the hot wire flow meter at the upstream of the intake port and the throttle. At the upstream of the throttle, the overshoot phenomena of the air flow rate by fast throttle opening were analyzed with choked flow. At the upstream of the intake port, the cylinder variation of the air flow rate and the difference between fast throttle opening and closing were showed during the unsteady state by the throttle step change. The results of this study can be used for the design of the throttle valve geometry and cylinder by cylinder control.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.373-376
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• 2008

Industrial Steam Turbine first stage shell pressure is related to throttle flow. Theoretically, first stage shell pressure could, therefore, be measured and used as an index of turbine throttle flow. However, accurate flow measurements show that this pressure is not a reliable index of the actual flow. Data analysis of steam turbinessubjected to ASME acceptance tests shows that the use of first stage shell pressure as an index of throttle flow produced errors as large as 9.6 %. The mean of the errors was +2.2% with a standard deviation of ${\pm}$2.8 %. Applications that require an accuratedetermination of turbine steam flow, such as turbine acceptance testing, should, therefore, not rely on this method. Therefore, First stage shell pressure measurement serves as a valid and economical indicator of turbine throttle flow in cases where a high degree of accuracy in throttle flow measurement is not required but repeatability is desired, such as for boiler control. Generally speaking, Steam turbine first stage shell pressure may also be a very useful monitor of turbine performance when used with certain other turbine measurements.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.1-8
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• 2002

The flow and combustion patterns have been investigated inside the gasoline engine cylinder with the swirl or tumble flow, whereas the air flow characteristics, which are generated in the part of intake system before entering into the intake manifold, have not been known completely. It is necessary to analyze the flow field in the intake system consisting of air rater, throttle valve and intake manifold. The throttle valve, used to control the intake air flow rate, is important because it makes various mass flow rate and flow patterns. Three-dimen-sional How characteristics such as velocities, turbulent intensities and Reynolds shear stresses are measured by the hot wire anemometer at the exit of the throttle valve with the variation in the valve opening angle($15^{\circ}$, $45^{\circ}$, $75^{\circ}$ and $90^{\circ}$) and the Reynolds numbers (45000, 70000 and 140000). There are a lot of changes in flow characteristics at $75^{\circ}$ due to the large recirculation flow comparing with those of the other cases, and the streamwise velocity is especially enforced strongly below the valve shaft. The other component velocities are relatively large near the centerline parallel to the valve shaft. The effects of the Reynolds number on the flow field are not severe.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2002년도 하계학술발표대회 논문집 제21권 1호
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• pp.469-474
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• 2002

In recent years, modularization of engine parts has increased the application of plastic products in air intake systems. Plastic intake manifolds provide many advantages including reduced weight, contracted cost, and lower intake air temperatures. These manifolds, however, have some weakness when compared with customary aluminium intake manifolds, in that they have low sound transmission loss because of their lower material density. This low transmission loss of plastic intake manifolds causes several problems related to flow noise, especially when the throttle is opened quickly. The physical processes, responsible for this flow noise, include turbulent fluid motion and relative motion of the throttle to the airflow. The former is generated by high-speed airflow in the splits between the throttle valve and the inner-surface of the throttle body and surge-tank, which can be categorized into the quadrupole source. The latter induces the unsteady force on the flow, which can be classified into the dipole source. In this paper, the mechanism of noise generation from the turbulence is only investigated as a preliminary study. Stochastic noise source synthesis method is adopted for the analysis of turbulence-induced, i.e. quadrupole noise by throttle at quick opening state. The method consists of three procedures. The first step corresponds to the preliminary time-averaged Navier-Stokes computation with a $k-\varepsilon$ turbulence model providing mean flow field characteristics. The second step is the synthesis of time-dependent turbulent velocity field associated with quadrupole noise sources. The final step is devoted to the determination of acoustic source terms associated with turbulent velocity. For the first step, we used market available analysis tools such as STAR-CD, the trade names of fluid analysis tools available on the market. The steady state flows at three open angle of throttle valve, i.e. 20, 35 and 60 degree, are numerically analyzed. Then, time-dependent turbulent velocity fields are produced by using the stochastic model and the flow analysis results. Using this turbulent velocity field, the turbulence-originated noise sources, i.e. the self-noise and shear-noise sources are synthesized. Based on these numerical results, it is found that the origin of the turbulent flow and noise might be attributed to the process of formulation and the interaction of two vortex lines formed in the downstream of the throttle valve. These vortex lines are produced by the non-uniform splits between the throttle valve and inner cylinder surface. Based on the analysis, we present the low-noise design of the inner geometry of throttle body.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.36-47
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• 1999

Three-way catalyst converter, cleaning up the exhaust gas contamination of SI engine, has the best efficiency when A/F ratio is near the stoichiometry . The feedback control using oxygen sensors in the exhaust manifold has limits caused by the system delays. So the accurate measurement of air flow rate to an engine is essential to control the fuel injection rate especially on transient condition like the rapid throttle opening and closing. To measure the rapid change of flow rates. the air flow meter for the engine requires quick response, flow reversal detection, and linearity . Tjhe proposed integration type air flow meter (IFM), composed of an ultrasonic flow meter with an integration circuit, has significantly improved the measurement accuracy of air mass inducted through the throttle body. The proposed control method estimated the air mass at the cylinder port using the measured air mass at the throttle . For the fuel dynamic model, the two constant fuel model is introduced . The control parameters from air and fuel dynamics are tuned to minimize the excursion of the air fuel ratio. As a result A/F ratio excursion can be reduced within 5% when throttle rapidly opens and closes at the various engine conditions.

• 한국소음진동공학회논문집
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• 제14권4호
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• pp.310-318
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• 2004

For many industrial problems originating from aerodynamic noise, noise prediction techniques, reliable and easy to apply, would be of great value to engineers and manufacturers. General algorithm is presented for the prediction of internal flow-induced noise from quick opening throttle valve in an automotive engine. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curle's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve show good agreement with actual measurements. The results show that the dipole noise is dominant in this phenomena and the origin of noise sources is attributed to the anti-vortex lines formed in the down-stream from a throttle valve. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.78-83
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curls extension of Lighthills. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 항공우주기술
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• 제3권2호
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• pp.50-55
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• 2004

이륙중량 900㎏의 CRW 비행체에 맞게 설계한 추진시스템에 대해서 회전익모드 및 천이모드에서의 성능해석을 수행하였다. 추진시스템은 터보제트엔진, 덕트류 및 노즐로 구성된다. 엔진 터빈출구부터 노즐까지의 덕트 내부유동을 1차원 유동으로 가정하여 압축성, 점성유동해석을 하였다. 특히 로터 블레이드내의 유동은 점성효과와 함께 원심력의 효과도 고려하였다. 계산결과로 회전익모드에서 요구동력을 만족시키기 위한 엔진 Throttle 범위와, 천이모드에서 요구동력 및 요구출력을 만족시키기 위한 엔진 Throttle, 유량배분, 로터회전속도, 순항 노즐면적 등을 제시하였다.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.1-12
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• 1997

In an SI engine, the characteristics of the air flow is important not only for the design of the intake system geometry but also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement using the ultrasonic flow meter and hot wire flow meter was conducted at the upstream of the intake port and the throttle. At the upstream of the intake port, the pulsating flow into the cylinder affected by the pressure wave was detected directly with the flow meters instead of pressure sensors. At the upstream of the throttle, the reverse flow phenomena were showed by comparing the flow pattern measured by the hot wire air flow meter and the ultrasonic air flow meter. The results of this study can be used for the analysis of the tuning effect in the intake manifold and estimation of the error in real time measurement for the air flow rate.

• 자동차안전학회지
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• 제11권1호
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• pp.48-54
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• 2019

Optimal engine control is needed to cope with the global environmental regulations that are globally enforced. For optimum engine control, the electronic throttle control system (ETCS) is a prerequisite. Automotive makers are having an effect on reducing emissions and improving fuel economy by applying ETCS which is designed to secure stability. The ETCS controls the output of the throttle valve by passing the output value of the accelerator position sensor (APS) to the engine control unit (ECU). In this study, the authors investigated the safety standards of domestic and overseas accelerator control system and tried to understand how the air flow control affects the engine output by replacing the throttle. The authors suggest an improvement proposal of safety standard based on the result of driving evaluation by various modes.