• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.157-160
• /
• 2006

A turbo-expander is developed for the regeneration in the expansion process. The turbo-expander operates in the partial admission and supersonic flow, and an axial-type single stage turbine is applied to the turbo-expander. Its outer diameter is 82mm and the operating gas is R134a. A 15kW reciprocating compressor is applied in this experiment and the turbo-expander is installed in the expansion process instead of the commonly using expansion valve. Two supersonic nozzles are applied for the expansion process. The high speed of R 134a after passing the supersonic nozzles gives the impulse force to the turbo-expander and some powers are generated on this process. A generator is installed at the end of the turbo-expander shaft. The generating output power from the turbo-expander is controlled by the power controller. Pressures and temperatures are measured on the lines for the performance investigation. More than 600W/(kg/sec) are generated in this experiment.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.129-130
• /
• 2010

Design of turbo-compressors has been considered to be a high-tech which only a few early industrialized countries could do efficiently since it requires not only deep understanding of high level gas dynamics and complex fluid dynamics but also accumulation of experiences in the feedback of expensive manufacturing and difficult testing to the design theory and empirical design coefficients. CFturbo is the turbomachinery design software which incorporates traditional well formulated German design technology and latest software technology of 3-dimensional graphics. Fine/Turbo is a powerful tubomachinery-oriented CFD package with quality structured grid topology templates for almost all the tubomachinery configurations for easy, fast and accurate CFD analysis. Rapid and effcient process off turbo-compressor R&D is setup with the combination of CFturbo and Fine/Turbo.

• ETRI Journal
• /
• v.28 no.6
• /
• pp.790-792
• /
• 2006

The performance of a turbo decoder depends strongly on the number of iterations in its decoding process. It is necessary to stop the decoding process at an appropriate moment to alleviate the serious burden, in terms of both the computational speed and latency, part of which is associated with too many iterations. In this letter, we introduce a criterion for finding the opportune moment to stop the decoding process, called a hard decision aided criterion based on bit interleaved parity, which is known to have much simpler hardware logic, compared with other schemes, and does not lead to any significant performance degradation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.9C
• /
• pp.843-850
• /
• 2003

Turbo coding and turbo processing have been known as methods close to Shannon limit in the aspect of wireless MIMO communications similarly to wireless single antenna communication. The iterative processing can maximize the mutual effect of coding and interference cancellation, but turbo coding has not been used for turbo processing because of the inherent decoding process delay. This paper proposes a turbo coded MIMO system with adaptive turbo parallel space-time (Turbo-PAST) processing for high-speed wireless communications and a enhanced cyclic redundancy check (E-CRC) scheme as an efficient and simple priori stopping criterion. Simulation results show that the Turbo-PAST outperforms conventional system with 1.3dB and the proposed E-CRC scheme effectively reduces the amount of turbo processing iterations from the point of average number of iterations.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.3
• /
• pp.34-38
• /
• 2018

Recently, the turbo charger has become an important part because it yields little displacement and high power while downsizing the engine's fuel ratio for environmental purposes. In this study, flow analysis was conducted to form the basis of data regarding the best efficiency. The axial displacement was changed from none to 25 mm by controlling the configuration of the turbo charger and the flow analyses were compared with each other. The maximum rate of the outlet of model 1 was 46.36 m/s and the maximum pressure of model 4 was 0.761946 Pa. The maximum flow rate of model 4 was 0.000187650 kg/s. This study's result should aid in the effective design of a turbo charger with high performance.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.5
• /
• pp.91-96
• /
• 2011

This study aims to analyze the flow characteristics of turbo-fan which is applied to the industrial field. Numerical analysis has been carried out to investigate the pulsation behavior of exhaust air flown out turbo fan by rotating impeller with constant speed. Moving mesh technique is proved as time-accurate solution for the flow inside impeller. As numerical results come within the error range of 1% by comparing with theoretical results, the numerical analysis can be verified. Cutoff angle has large influence on the amplitude of pulsation and the least pulsation of flow can be generated by the cutoff angle of $20^{\circ}$.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.2
• /
• pp.90-95
• /
• 2011

This paper presents the study on the contact stress analysis of a pair of mating helical gears for turbo blower during rotation. Turbo blowers need high speed rotation of impeller in structure and high rate gear ratio. The use of helical gear indicated that noise was an important problem when the application involves high speeds and large power transmission. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at the lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. In this study, the gear design considering the contact stress on a pair of mating gear is more severe than that of AGMA standard.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.8
• /
• pp.816-822
• /
• 2003

In this paper, we propose an efficient iteration control method with low complexity for Turbo TCM(Turbo Trellis Coded Modulation) decoding which will be used fur power-limited environment. As the decoding approaches the performance limit of a given turbo code, any further iteration results in very little improvement. Therefore, it is important to devise an efficient criterion to stop the iteration process and prevent unnecessary computations and decoding delay. This paper presents an efficient algorithm for turbo TCM decoding that can greatly reduce the delay and iteration number. The proposed method use adaptive iteration number according to the criterion using the extrinsic information variance parameter in turbo TCM decoding process. The simulation results show that the proposed technique effectively can reduce the decoding delay and computation with very little performance degradation.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.2
• /
• pp.16-25
• /
• 2011

A Turbo-impeller is widely used in industries as well as in aero engines. Its design technology has been developed since the early 20th century. However, the final configuration of the impeller depends on the designers. In this study, a whole design process was introduced and an optimization method to design an impeller was studied in order to design a better impeller without influence by designers. In particular, as the Artificial Neural Network was applied to the optimization, the computational time for the optimization was equivalent to the time consumed by the gradient method and its result was guaranteed as the optimum in the whole design domain. Using this method, any impeller can be improved by selecting design variables after measuring profiles of the impeller.

• Tribology and Lubricants
• /
• v.21 no.3
• /
• pp.114-121
• /
• 2005

As fuel cell system is environmental friendly generator, its performance depends on its air supply system. Because, fuel cell stack generates electrical energy by electron and the electron is generated by reacting between air and hydrogen. So, more and more compressed air is supplied, more and more the energy can be obtained. In this study, turbo-expander supported by air foil bearing is introduced as the air supply system used by fuel cell systems. The turbo-expander is a turbo machine which operates at high speed, so air foil bearings suit its purpose for the bearing elements. Analysis for confirming the stability and endurance is conducted. Based on FDM and Newton-Raphson method, characteristics of air foil bearing, dynamic coefficients, pressure field and load capacity, are obtained. Using the characteristics of air foil bearing, the rotordynamic analysis is performed by finite element method. The analysis (stability analysis and critical speed map) shows that turbo-expander is stability at running speed. After the analysis, the test process and results are presented. The goals of test are running up to 90,000 RPM, flow rate of 150 $m^3/h$ and pressure ratio of 1.15. The test results show that the aerodynamic performance and stability of turbo-expander are satisfied to the primary goals.