• Journal of the Optical Society of Korea
• /
• v.20 no.4
• /
• pp.481-487
• /
• 2016

This study presents a new optical system for a combiner-type head-up display (HUD) with a cylindrical lens as an asymmetrical aberration corrector, instead of a freeform mirror. In the initial design process based on off-axial aberration analysis, we obtain an off-axis two-mirror system corrected for linear astigmatism and spherical aberration by adding a conic secondary mirror to an off-axis paraboloidal mirror. Thus, since the starting optical system for an HUD is corrected for dominant aberrations, it enables us to balance the residual asymmetrical aberrations with a simple optical surface such as a cylinder, not a complex freeform surface. From this design process, an optical system for an HUD having good performance is finally obtained. The size of the virtual image is 10 inches at 2 meters away from a combiner, and the area of the eye box is 130×50 mm².

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.3
• /
• pp.425-433
• /
• 1994

The conventional weakly-coupled tap-off for CATV and/or MATV transmitting circuits has been fabricated empirically and experimentally. So, the theoretical analysis or the design method of the conventional one has not been established, the characteristics of which were not good. To solve these problems, we have proposed a modified weakly-coupled freedom in design. This paper describes the design theories and analysis method of the theoretical frequency characteristics of a Modified Weakly-coupled Tap-off with high density of coupling intervals for CATV and/or MATV system. From the theoretical analysis it has been shown that the frequency characteristics of the tap-off proposed here are improved much in comparision with the conventional one. Furthermore, the practical measurements of frequency characteristics for the fabricated circuits show agreement with the theoretical results, and hence, the validity of proposed design and analysis methods has been confirmed.

• The KSFM Journal of Fluid Machinery
• /
• v.19 no.6
• /
• pp.34-42
• /
• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.245-249
• /
• 2007

In this study a model-based diagnostic method using the Neural Network was proposed for PW206C turbo shaft engine and performance model was developed by SIMULINK. Fault and test database to build the NN was obtained at various off-design operating range such as flight altitude, flight Mach number and gas generator rotational speed variation. According to the fault detection analysis results, it was confirmed that the proposed fault detection method could find well the fault of compressor, compressor turbine and power turbine at on-design point as well as off-design point conditions.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.11 no.3
• /
• pp.29-34
• /
• 2007

In this study a model-based diagnostic method using the Neural Network was proposed for PW206C turbo shaft engine and performance model was developed by SIMULINK. Fault and test database to build the NN was obtained at various off-design operating range such as flight altitude, flight Mach number and gas generator rotational speed variation. According to the fault detection analysis results, it was confirmed that the proposed fault detection method could find well the fault of compressor, compressor turbine and power turbine at on-design point as well as off-design point conditions.

• The KSFM Journal of Fluid Machinery
• /
• v.17 no.3
• /
• pp.5-12
• /
• 2014

This paper presents a design optimization for meridional profile and blade angle ${\theta}$ of a centrifugal compressor with DOE (design of experiments) and RSM (response surface method). Control points of the $3^{rd}$ order Bezier curve are used for design parameters and specific overall efficiency is used as object function. The response surface function shows good agreement with the 3D computational results. Three different optimized designs are proposed and compared with reference design at design point and off-design point. Contours of relative Mach number, static entropy, and total pressure are analyzed for improvement of performance by optimization. Off-design performance analysis is conducted by total pressure and efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.9
• /
• pp.1264-1276
• /
• 2000

Light-off catalyst has been used for minimization of cold-start emissions. Improved cold-start performance of light-off catalyst needs the optimal design in terms of flow distribution, geometric surface area, precious metal loading, cell density and space velocity. In this study, these influential factors are numerically investigated using integrated numerical technique by considering not only 3-D fluid flow but also heat and mass transfer with chemical reactions. The present results indicate that uneven catalyst loading of depositing high active catalyst at upstream of monolith is beneficial during warm-up period but its effect is severely deteriorated when the space velocity is above 100,000 $hr^{-1}$ To maximize light-off performance, this study suggests that 1) a light-off catalyst be designed double substrate type; 2) the substrate with high GSA and high PM loading at face be placed at the front monolith; and 3) the cell density of the rear monolith be lower to reduce the pressure drop.

• The KSFM Journal of Fluid Machinery
• /
• v.4 no.3 s.12
• /
• pp.46-52
• /
• 2001

This paper describes a turbine test program conducted at Seoul National University(SNU). To measure blades' aerodynamic performance, either linear(2-Dimensional) or annular(3-Dimensional) cascades are often used. However, neither cascade can consider effects such as those due to rotation or rotor-stator interaction. Therefore, a rotating test facility for axial turbines has been designed and built at SNU, and its description is given in this paper. The results from an axial turbine performance test are presented. At the design point, the measured efficiency agrees with the efficiency predicted by a meanline analysis. At off design points, however, the measured and predicted efficiencies diverge. The most likely cause is hypothesized to be the inaccuracy of correlations used in the meanline analysis at off design points.

• Journal of computational fluids engineering
• /
• v.6 no.1
• /
• pp.14-20
• /
• 2001

The CFD analysis of the three-dimensional turbulent flow in the impeller and diffuser of an axial flow pump was performed. Not only the design point but also the off-design points were computed. The results were compared with available experimental data in terms of head generated. At the design point, the analysis accurately predicted the experimental head value. In the range of the higher flow rates, the results were also in very good agreement with the experimental data, not only in absolute value but also in term of slope. Although experimental data to be compared were not available in the range of the lower flow rates, the results well described the S-shape performance curve of the axial pump characteristic.

• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.91-98
• /
• 2001

As the second part of the author's study, off-design behavior of the design and performance parameters in the low-solidity cascade diffuser in a centrifugal compressor is investigated. The experimental flange-to-flange compressor map serves the validity of application of the present CFD work to the detailed investigation of the low-solidity cascade diffuser. Some meanline design and performance parameters as well as three-dimensional internal secondary flow fields are studied when the flow rate is changed from deep choke to stall.