• International Journal of Automotive Technology
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• v.8 no.5
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• pp.575-581
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• 2007

As current and future automobile emission regulations become more stringent, the research on flow distribution for an exhaust manifold and close-coupled catalyst(CCC) has become an interesting and remarkable subjects. The design of a CCC and exhaust manifold is a formidable task due to the complexity of the flow distribution caused by the pulsating flows from piston motion and engine combustion. Transient flow at the exhaust manifold can be analyzed with various computational fluid dynamics(CFD) tools. However, the results of such simulations must be verified with appropriate experimental data from real engine operating condition. In this study, an experimental approach was performed to investigate the flow distribution of exhaust gases for conventional cast types and stainless steel bending types of a four-cylinder engine. The pressure distribution of each exhaust sub-component was measured using a simulated dynamic flow bench and five-hole pitot probe. Moreover, using the results of the pitot tube measurement at the exit of the CCC, the flow distribution for two types of manifolds(cast type and bending type) was compared in terms of flow uniformity. Based on these experimental techniques, this study can be highly applicable to the design and optimization of exhaust for the better use of catalytic converters to meet the PZEV emission regulation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.359-363
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• 2011

In this paper, the characteristic of pressures had been analyzed with a series of shapes that are pressure probes used in supersonic wind tunnel. When a performance of supersonic wind tunnel is evaluated, the Mach number is calculated by using the ratio of static pressure in test section wall to total pressure in settling chamber. Also the flow condition can be visualized by schlieren system. However a number of limitations exist to measure pressure of test section due to high speed and boundary layer effect. Therefore a specific pressure probe is needed for evaluating flow condition in test section at a various of positions. In the paper, experiments were conducted in terms of some pitot probes and the results were compared and analyzed.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.122-128
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• 2000

Aerodynamic optimization of an automotive air-conditioning blower is a hard task because of the highly complex flow phenomena related to three-dimensional flow separations and the unsteady nature caused by the interaction between primary and secondary air flows throughout the fan. In this paper, an aerodynamic study on a forward-curved centrifugal fan has been carried out Firstly we obtained the fan performance curves versus flow rates showing its unstable nature in the surging operation range. Secondly aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage using a 5-hole pilot probe, at different operating conditions. Surface flow pattern near the cut-off area exhibits similar flow behavior above the best efficiency operating point, although the pressure level increases substantially with the Increase of flow rate. Vorticity in the casing passage flow occurs in all (low rates, downstream from the r-Z plane $\theta$=120 deg., where the position of its core changes with the circumferential location. Although complex, the general flow behavior were common, giving insight in its main aerodynamic features.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.10-10
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• 1998

천음속 익형에서 발생하는 응축충격파와 경계층의 간섭을 피동제어 하여 항력감소에 대한 연구를 2.5$\times$7$\textrm{cm}^2$ 천음속 풍동에서 수행하였다. 익형표면에 설치한 정압공으로 정압을, 익형후방에 설치한 8개의 Pitot probe로 전압을 동시에 측정하여 충격파를 통한 에너지의 손실과 항력의 변화를 계산하였고, 또한 유동장과 충격파의 형상을 가시화하기 위해 슈리렌 가시화 시스템을 사용하였다. 실험은 NACA 0012 익형에서 기공률 변화에 따른 피동제어의 항력감소 초과를 조사한 다음 NACA 64-018 익형에서는 기공률과 공동의 크기의 변화가 미치는 효과를 연구하였다. 피동제어의 개념은 충격파가 발생하는 하부벽을 다공벽으로 만들고 그 아래를 공동으로 만들면 충격파 후방의 상대적으로 높은 압력이 기류의 일부를 공동으로 자연스럽게 유입시키고 다시 공동에서 낮은 압력의 충격파 상류로 유출시키는 것이다.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.456-465
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• 2000

An experiment was conducted to investigate the aerodynamic losses of high pressure steam turbine nozzle (526A) subjected to a large range of incident angles ($-34^{\circ}\;to\;26^{\circ}$) and exit Mach numbers (0.6 and 1.15). Measurements included downstream Pitot probe traverses, upstream total pressure, and end wall static pressures. Flow visualization techniques such as shadowgraph and color oil flow visualization were performed to complement the measured data. When the exit Mach number for nozzles increased from 0.9 to 1.1 the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses measured at subsonic conditions ($M_2<0.9$). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on the shadowgraphs taken during the experiment, it' s believed that the large increase in losses at transonic conditions is due to strong shock/ boundary layer interaction that may lead to flow separation on the blade suction surface.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.109-112
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• 2002

The supersonic jet discharging from a petal nozzle is known to enhance mixing effect with the surrounding gas because it produces strong longitudinal vortices due to the velocity difference from both the major and minor axes of petal nozzle. In the present study, the supersonic free jet discharging from the petal nozzle is investigated experimentally. The nozzles used are 4, 6, and 8 lobed petal nozzles with a design Mach number of 1.7, and the flow fields are compared with a circular nozzle with the same design Mach number. The pitot impact pressures are measured using a fine pilot probe. The flow fields are visualized using a Schlieren optical method. The results show that the petal nozzle has more increased supersonic length compared with the circular jet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.7
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• pp.529-537
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• 2021

Wind tunnel tests were carried out with a scramjet high speed vehicle. Since the scramjet engine does not have a compressor, it has a simple structure, but it is important to design the intake for the supersonic combustion in the combustion chamber. In this study, internal flow characteristics and the starting condition were analyzed by measuring the pressure at the isolator exit just before the combustion chamber, and the intake performance parameters were calculated and compared the result on every Mach number. The aerodynamic characteristics of the flow-through high speed vehicle were analyzed and internal drag correction is required to precisely analyze the aerodynamic characteristics. In this paper, an experimental technique using three probes for internal drag correction was proposed. By applying internal drag correction, it was able to figure out the effect of the internal flow on the aerodynamic force of the vehicle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.511-517
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• 2009

A servo type angle of attack sensor using the null-seeking method is designed and its characteristics are analyzed in this study. Angle-of-attack in the null-seeking method is given by the probe rotation angle with respect to the body reference line when pressure difference measured in two holes on the probe becomes zero. This method provides highly accurate and uniform angle-of-attack measurements over all range. Hence, this kind of angle-of-attack sensor is adequate for unmanned aerial vehicles(UAVs). In this paper, we first analyze the requirements for developing angle-of-attack sensors. And the servo type angle-of-attack sensor is then designed and fabricated. The on-board angle-of-attack calculation algorithm is also developed. Finally, the characteristics of the developed angle-of-attack sensor are identified through MATLAB Simulink and wind tunnel tests.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.10
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• pp.1979-1989
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• 1992

An experimental study has been performed to investigate the horseshoe vortex system formed around cylindrical obstacles mounted vertically on the surface over which a boundary layer is formed. To measure the mean velocity of the flow field, a five-hole Pitot tube has been used. In addition, surface static pressure measurements and surface flow visualization were also performed. From the five-hole probe measurements, vorticity distribution was deduced numerically and the streamwise velocity distribution was also examined. To consider the effect of the leading-edge shape on the formation of the horseshoe vortex, a qualitative comparison was made between the three-dimensional flows around a circular cylinder and a wedge-type cylinder. The five-hole probe measurements showed a single primary vortex which exists immediately upstream of the obstacles, and endwall flow visualization showed the existence of a corner vortex. As the vortex passes around the obstacle, the vortex strength is reduced and the vortex core moves radially outward. Due to this horseshoe vortex, the fluid momentum is found to decrease along the streamwise direction. Since the horseshoe vortex formed around a wedge-type cylinder has weaker strength and is confined to a narrower region than that around a circular, the possibility that the secondary flow loss due to the horseshoe vortex can be reduced through a change of the leading- edge shape is proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.646-652
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• 1999

Detailed characteristics of the mean flow field inside the rotor of a multiblade fan with scroll are presented in this paper by measurements and visualizations. The measurements were taken with a five-hole probe and conformed by smoke test. How field is distinguished clearly in 3 regions with respect to the flow directions. The first region is near the exit of scroll where the fluid flows the opposite direction to the rotation of rotor. The second is opposite side of the scroll exit where the fluid flows the same direction to the rotation of rotor. The third is the region where the fluid flows toward the blades directly with the largest values comparatively. The strongest recirculation is happened in the second region, and the weakest one is in the third region. This complex configuration makes the flow field highly non-uniform and may cause to generate a noise and ineffective flow efficiency.