• Journal of KSNVE
• /
• v.11 no.1
• /
• pp.29-35
• /
• 2001

Recently, the porous duct is becoming one of Possible ways to reduce the intake noise of an automobile instead of using resonators. In this article, acoustic characteristic of the porous duct is investigated theoretically and experimently. Futhermore, 4-pole parameter of the porous duct is introduced to predict transmission loss of it for various case. Acoustic efficiency of the porous duct is shown with experimental result using a car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.443-446
• /
• 2006

For the satisfaction of the high engine performance and the low radiated sound pressure simultaneously, the duct length in the vehicle intake/exhaust system should be tuned carefully in the design and development stage of a vehicle. This study was concerned about the effects of intake duct length in clean and dirty sides on the radiated sound emitted from an inlet. An index derived from the existing prediction model of radiated sound pressure was employed to determine which duct was more influential to the radiated sound. Comparing the experimental and predicted results, we found that the change of dirty-side duct length caused a larger change than that in the clean side in the radiated sound level from a tested intake system.

• Proceedings of the Korean Fiber Society Conference
• /
• 1996.10a
• /
• pp.29-34
• /
• 1996

In the present paper, the flow distribution in the hot air drying chamber of a sizing machine was numerically analyzed with respect to the geometries of the intake duct to obtain the more uniform flow distribution in the chamber. The result shows that the velocity distribution in the inlet of the chamber was significantly dependent on the the geometry of the intake duct. The degree of the non-uniformity in the chamber was reduced as the incident angle of the intake duct became to be smaller.

• 한국전산유체공학회:학술대회논문집
• /
• 2002.10a
• /
• pp.121-126
• /
• 2002

Aircraft propulsion systems often use diffusing S-duct to convey air flow from the wing or fuselage intake to the engine compressor, Well designed S-duct should incur minimal total pressure losses and deliver nearly uniform flow with small transverse velocity components at the engine compressor entrance. Reduced total pressure recovery lowers propulsion efficiency and nonuniform flow conditions at the engine face lower engine stall limits. In this study, S-duct which has maximum total pressure recovery and nearly uniform flow profiles at the compressure intake should be found using design optimization methods with 3-dimensional Wavier-Stokes analyses.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.181-184
• /
• 2002

CFD calculations are carried out to investigate the turbulent flow characteristics inside the duct of marine waterjet propulsors. The Reynolds-averaged Wavier-Stokes equations are solved using a finite-volume method. Standard $k-{\varepsilon}$ model and realizable $k-{\varepsilon}$ model are evaluated with an existing experimental data. Multi-block grid topology is adopted to describe the details of complex duct geometry. The present numerical methods are applied to the preliminary duct design of new waterjet propulsor system. Four different influx conditions are simulated to find out pressure and velocity distribution inside the intake duct. Attention is also paid upon the possible flow separation inside the waterjet duct. It is found that CFD tools can be used for the initial evaluation of inflow condition into the impeller of waterjet propulsor system.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.1 s.139
• /
• pp.1-9
• /
• 2005

Waterjet propulsion is widely used to thrust high speed marine vessels in excess of 30-35 knots by virtue of the high propulsive efficiency, good maneuverability, and less cavitation. From the aspect of power loss, approximately $7-9\%$ of the total power is lost in intake duct due to the flow separation, nonuniformity, etc. Thus, detail understanding of flow phenomena occurring within intake duct is essential to reduce the power loss, as well as noise and vibration. The present work solved 30 incompressible RANS equations to provide complicated viscous flow features of intake duct. The numerical results were compared with experiments and good agreements were obtained for three jet velocity ratios.

• Journal of computational fluids engineering
• /
• v.11 no.1 s.32
• /
• pp.57-66
• /
• 2006

An optimal shape design approach is presented for a subsonic S-shaped intake using aerodynamic sensitivity analysis. Two-equation turbulence model is employed to capture strong counter vortices in the S-shaped duct more precisely. Sensitivity analysis is performed for the three-dimensional Navier-Stokes equations coupled with two-equation turbulence models using a discrete adjoint method For code validation, the result of the flow solver is compared with experiment data and other computational results of bench marking test. To study the influence oj turbulence models and grid refinement on the duct flow analysis, the results from several turbulence models are compared with one another and the minimum number of grid points, which can yield an accurate solution is investigated The adjoint variable code is validated by comparing the complex step derivative results. To realize a sufficient and flexible design space, NURBS equations are introduced as a geometric representation and a new grid modification technique, Least Square NURBS Grid Approximation is applied With the verified flow solver, the sensitivity analysis code and the geometric modification technique, the optimization of S-shaped intake is carried out and the enhancement of overall intake performance is achieved The designed S-shaped duct is tested in several off-design conditions to confirm the robustness of the current design approach. As a result, the capability and the efficiency of the present design tools are successfully demonstrated in three-dimensional highly turbulent internal flow design and off-design conditions.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.3
• /
• pp.38-48
• /
• 2005

For the development of Scramjet engine technology, intake designing processes are investigated. The basic geometry is determined by the inviuld relation such as shock wave relations and geometric relations. Furthermore, bleed duct is installed for preventing boundary layer development and shock wave impingement. Performance of the designed intake is validated by numerical analysis. As a result, double- wedge intake showed better characteristics in total pressure recovery than single-wedge intake.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.1
• /
• pp.17-25
• /
• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.4
• /
• pp.87-93
• /
• 2016

In a Direct Connect(DC) mode altitude engine test, a labyrinth seal is set up between an air intake duct and an engine. The labyrinth seal plays a key role in mechanically isolating them, which contributes to the accurate measurement of thrust and the other component forces. However, when high vertical temperature gradient is generated in the supplied air in the duct, the isolation breaks down. In this paper, a labyrinth seal control device is designed and installed in an effort to eliminate the issue. Test result shows the device successfully gets rid of the contact problem even when high vertical temperature gradient is produced.