• 한국대기환경학회지
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• 제12권2호
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• pp.131-139
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• 1996

The developent of ceramic combustor is being increased beca- use of the excellent physical properties of ceramic material, that is, high-resistant strength, high emissivity power and high corrosin-resistance. Ceramic combustor has been interested in the application of ultra-lean combustion for low NO$_{x}$ emission and gaseuos waste incineration with good combustion. This experimental study was conducted to investigate the combustion and emission characteristics of wall recess type ceramic combustor with equivalence ratio, mixture flow velocity and wall recess depth as parameters. The results in this study are as follows: 1. Wall recess played a important role to extend flame stability region. 2. The peak temperature of gas was peoportional to equivalence ratio, mixture flow velocity and wall recess depth. 3. The static pressure of mixing chamber and inlet temperature depended on the position of flame zone. 4. NO reduction was achieved by lean mixture without lower combustibility.y.

• 한국분무공학회지
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• 제23권2호
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• pp.49-57
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• 2018

Numerical study under single-injection on bi-swirl coaxial injectors with different recess lengths was performed using ANSYS Fluent. The bi-swirl coaxial injectors which consisted of inner closed-type and outer open-type swirl injectors, had three different recess lengths. By changing mass flow rates, numerical simulation was repeated using the Reynolds stress BSL turbulent model. The numerical results such as discharge coefficient and spray angle were compared with previous experimental data and were found to be approximately matched well with them, irrespective of recess length. Quantitative data which was hard to be measured from experiments, were successfully obtained through the present numerical study.

• 한국추진공학회지
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• 제7권2호
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• pp.62-69
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• 2003

Swirl형 인젝터는 연소가 안정적이고 효율이 높으며 비교적 넓은 구간의 혼합비 변화에 민감하게 반응하지 않는 장점을 가지고 있다. 바깥쪽 오리피스 끝단에서 안쪽 오리피스 끝단까지의 길이인 Recess 길이는 Swirl형 인젝터 성능의 주요 변수로, 추진제의 충돌, 혼합, 분무, 연소에 많은 영향을 준다. 이에 본 연구에서는 Recess 길이에 따라 엔진의 성능이 어떻게 변화하는지에 대해 수치해석, 비연소 실험, 연소 실험을 통해 확인해 보았다. 그 결과 Recess 길이에 따른 로켓엔진의 성능 변화를 확인 할 수 있었고, 인젝터의 성능을 평가하는 과정에서 수치해석, 비연소 실험을 통한 성능 예측이 연소실험을 통해 타당한 과정임을 확인 할 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.111-121
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• 1997

The stability of a rotor-bearing system supported by swirl-controlled hybrid journal bearing with pair-type angled injection orifices is investigated for improvement of the whirl frequency ratio by allowing effective control of the tangential flow inside the bearing clearance, i.e., by achieving more freedom in controlling strength and direction of the supply tangential flow inside the bearing clearance. It is suggested that the system instability can be improved through the change of bearing dynamic characteristic parameters with the swirl control. The orifice diameter d$_0$ and recess injection angle $\alpha$ along with combinations of swirl/anti-swirl supply pressures and directions (3.0-3.0MPa, 4.0-2.0MPa, 2.0-4.0MPa) are selected for design parameters for swirl-controlled effective factors dependent on journal speeds (3000, 9000, 15000, 21000 rpm). It has been found that the orifice diameter do shows strong effects on effective maneuverability of direct-stiffness and direct damping values, while recess injection angle $\alpha$ results in substantial magnitude and direction of cross-stiffness. Specifically, recess injection parameters which are functions of angle of orifice feeding flow and recess dimensions showed very feasible effect on the stability of swirl-controlled rotor-bearing system.

• Tribology and Lubricants
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• 제13권3호
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• pp.63-72
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• 1997

The stability of a rotor-bearing system supported by swirl-controlled hybrid journal bearing with pair-type angled injection orifices is investigated for improvement of the whirl frequency ratio by allowing effective control of the tangential flow inside the bearing clearance, i.e., by achieving more freedom in controlling strength and direction of the supply tangential flow inside the bearing clearance. It is suggested that the system instability can be improved through the change of bearing dynamic characteristic parameters with the swirl control. The orifice diameter $d_0$ and recess injection angle $\alpha$ along with combinations of swirl/anti-swirl supply pressures and directions (3.0~3.0 MPa, 4.0~2.0 MPa, 2.0~4.0 MPa) are selected for design parameters for swirl-controlled effective factors dependent on journal speeds (3000, 9000, 15000, 21000 rpm). It has been found that the orifice diameter $d_0$ shows strong effects on effective maneuverability of direct-stiffness and direct damping values, while recess injection angle $\alpha$ results in substantial effects on the magnitude and direction of cross-stiffness. Specifically, recess injection parameters which are functions of angle of orifice feeding flow and recess dimensions showed very feasible effect on the stability control of swirl-controlled rotor-bearing system.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.451-454
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• 2006

This paper describes the results of cold flow test and hot firing tests of an uni-element coaxial swirl injector and hot firing tests of a subscale combustor, as to the development effort of coaxial swirl injector for high performance liquid rocket engine combustor. A major design parameter for coaxial swirl injector is the recess number of a bi-swirl injector. The results of hot firing tests of the uni-element injector combustor and the sub-scale combustor are analyzed to investigate the effect of the recess number influencing on the combustion performance and pressure fluctuation. The test results of a cold flow test of the unielement combustor shows that it was shown that the change in recess number has significant effect on mixing characteristics and efficiency, while the effect of recess number on atomization characteristic is not The results of a series of firing tests using unielement and subscale combustor show that the recess length significantly affects the hydraulic characteristics, the combustion efficiency, and the dynamics of the liquid oxygen/kerosene bi-swirl injector. As a point of combustion performance, combustion efficiencies are 90% for unielement combustor and 95% for subscale combustor. The difference in the characteristic velocities between the unielement combustor and the subscale combustor may be caused by the difference in thermal loss to the combustor wall and the relative lengths of the combustion chamber. For a mixed type coaxial swirl combustor, the pressure drop across the injector increases as recess number becomes larger. The low frequency pressure fluctuation observed in unielement combustor can be related to the propellant mixing characteristics of the coaxial bi-swirl injector. The effect of the recess number on the pressure fluctuation inside the combustion chamber is more significant in un i-element combustor than the subscale combustor, of which the phenomena are also observed in time domain and frequency domain.

• Tribology and Lubricants
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• 제24권6호
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• pp.343-348
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• 2008

In this paper, a CFD (Computational fluid dynamics) code, FLUENT is adopted to investigate accurate flow characteristics for a slipper bearing which is used swash plate type hydraulic axial piston pump. Static pressure and velocity distributions, and velocity vectors are plotted for different film thickness and slipper rotational velocity. In recess region, there exists a doughnut shaped vortex ring. The static pressure distributions are non-uniform and the flow fields are highly asymmetrical under bearing rotation. Therefore the numerical method adopted in this paper can be use in design of hydrostatic components and further studies are required.

• 교육시설 논문지
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• 제24권5호
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• pp.3-10
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• 2017

This study was tried to find out characteristics of students' movement in classroom and homeroom. The object was the school whose homebase management was different by grade. Observation research was tried about middle school class that is simultaneously worked with different type of homeroom and the movement of students under various situations was analyzed. As a result, students in exclusive subject classroom moved in short time within one or two minutes after class. In case of exclusive homeroom, returning frequency of students was nearly about 85 to 100 percent within ten minutes in end of end. Behavioral characteristics of students in dual purpose homeroom was similar in exclusive subject classroom. The class using dual purpose homeroom showed high ratio in use of center homebase, therefore, returning frequency at short recess time was extremely low. In case of dual purpose homeroom at lunch time, next class students moved in early time and maximized within one or two minutes in end of end. These results are thought to be useful for planning spaces of variation type.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.699-703
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• 2017

액체로켓엔진에 사용되는 동축 와류형 분사기의 유동특성을 알아보기 위해 closed-type과 open-type 단일 분사기에 대한 수치해석을 수행하였다. ANSYS FLUENT라는 상용프로그램을 이용하여 해석적인 연구를 수행하였다. 분사기는 리세스 길이가 다른 3개의 모델을 선정하였다. 분사기 접선 방향의 입구로 유입되는 질량유량에 따라서 분사기 유동특성이 어떻게 변하는지 알아보기 위하여 수치해석을 수행하였으며, 실험을 통해 측정된 결과를 비교 및 분석하였다. 수치해석을 통해 얻은 결과는 실험을 통해 얻은 분사기 전단에 작용하는 압력과 유량계수와 차이가 크지 않음을 알 수 있었다.

• 한국기계연구소 소보
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• 통권18호
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• pp.21-27
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• 1988

In this study, a series of experiments and analyses are performed to estimate the static characteristics of hydrostatic journal bearing such as load capacity, pressure change in each recess, eccentricity of spindle, etc. The experiments are carried out for a multi-recess type journal bearing with capillary restrictor. The Finite Element Method(FEM) is used for the analyses. The predicted load capacity under the condition of stationary or eccentric ratio of bellow 0.2 of the spindle shows excellent agreement with the measured. But, with an increase of the eccentric ratio when the spindle is rotating, the predicted load capacity is largely estimated than the measured. It seems that the difference is mainly caused among others from the fact that the effect of oil-viscosity variation due to the temperature change in the bearing is not introduced into the analyses. The analysis method proposed to estimate the static characteristics of hydrostatic journal bearing is considered to be very reliable since the predicted results are overall in good agreement with the measured.