Browsing by Author "Chou, T. H."

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Experimental investigation of the effect of nozzle throat diameter on the performance of a hybrid rocket motor with swirling injection of high-concentration hydrogen peroxide
(2019-11-01)
Wei, S. S.
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Lee, M. C.
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Chien, Y. H.
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Chou, T. H.
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Wu, J. S.
One of the issues of using a normal graphite nozzle for the hybrid rocket propulsion is the serious throat erosion due to combustion with a higher O/F ratio. This may undermine the throttling capability of the hybrid rocket engine. In this study, we would like to address how the propulsion performance changes under the conditions of different nozzle throat diameters and O/F ratios. We designed and tested a 40-kgf class single-port hybrid rocket motor with the swirling injection of oxidizer, which utilizes the 90 wt% hydrogen peroxide and polypropylene (PP) as oxidizer and fuel, respectively. Three different diameters of graphite nozzle throat (10, 11, and 12 mm) were used to approximate various conditions of nozzle erosion, while the mass flow rates of the injected oxidizer were kept the same. The hot-fire test results indicated that the thrust was nearly the same even the nozzle throat diameters and O/F ratios were different. Especially, the discrepancies among the measured thrusts and oxidizer ISP under various test conditions were found to be less than 1%, which is highly beneficial for the purpose of the thrust control using mass flow rate control of the oxidizer for a hybrid rocket engine with swirling injection of high-concentration hydrogen peroxide.
Mixing Effectiveness Study in Scramjet Combustion
(2013-01-01)
Chen, Y. S.
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Lian, Y. Y.
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Chou, T. H.
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Lai, Alfred
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Wu, J. S.
Scramjet propulsion provides promising opportunities for high-speed transportation and cost reduction for satellite and spacecraft launch operations. This paper provides some selected numerical examples among the abundance of available test cases for the purpose of demonstrating to what extends the current computational models can do in assisting the design and test programs of scramjet combustors. Numerical examples that cover a wide range of flight speeds are investigated with benchmark data validations. Ideas of mixing enhancement and flame holding mechanisms in scramjet combustion is analyzed and planned for the future experimental investigations. (C) 2013 The Authors. Published by Elsevier Ltd.
Multiphysics simulations of rocket engine combustion
(2011-06-01)
Chen, Yen-Sen
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Chou, T. H.
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Gu, B. R.
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Wu, J. S.
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Wu, Bill
Recently, the hybrid rocket propulsion has become attractive to the research community and has developed the trend to become an alternative to the conventional liquid and solid rockets. The hybrid rocket is a combination of both the solid and liquid systems with half of the plumbing of the liquid rocket but retaining its operational flexibility and avoiding the explosive nature of the solid rocket. Among available hybrid systems, the N(2)O (Nitrous Oxide)-HTPB (Hydroxyl-Terminated PolyButadiene) hybrid propulsion represents the simplest but sufficiently efficient design. Unfortunately, even until now, research in developing hybrid N(2)O-HTPB propulsion system still strongly depends on trials-and-errors, which are time-consuming and expensive. Thus, detailed understanding of the fundamental combustion processes that are involved in the N(2)O-HIPB propulsion system can greatly impact the research community in this field. This may further facilitate the successful modeling of the combustion processes and help improving the design of N(2)O-HTPB propulsion system in the future. A comprehensive numerical model with real-fluid properties and finite-rate chemistry was developed in this research to predict the combustion flowfield inside a N(2)O-HIPB hybrid rocket system. Good numerical predictions as compared to experimental data are also presented. (C) 2010 Elsevier Ltd. All rights reserved.
NUMERICAL INVESTIGATION OF A N2O/HTPB HYBRID ROCKET MOTOR WITH A DUAL-VORTICAL-FLOW (DVF) DESIGN
(2017-12-01)
Lai, A.
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Lin, Y. C.
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Wei, S. S.
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Chou, T. H.
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Lin, J. W.
A compact hybrid rocket motor design that incorporates a dual-vortical-flow (DVF) concept is proposed. The oxidizer (nitrous oxide, N2O) is injected circumferentially into various sections of the rocket motor, which are sectored by several solid fuel "rings" (made of hydroxyl-terminated polybutadiene, HTPB) that are installed along the central axis of the motor. The proposed configuration not only increases the residence time of the oxidizer flow, it also implies an inherent "roll control" capability of the motor. Based on a DVF motor geometry with a designed thrust level of 11.6 kN, the characteristics of the turbulent reacting flow within the motor and its rocket performance were analyzed with a comprehensive numerical model that implements both real-fluid properties and finite-rate chemistry. Data indicate that the vacuum specific impulse (Isp) of the DVF motor could reach 278 s. The result from a preliminary ground test of a lab-scale DVF hybrid rocket motor (with a designed thrust level of 3,000 N) also shows promising performance. The proposed DVF concept is expected to partly resolve the issue of scalability, which remains challenging for hybrid rocket motors development.
Unipolar Switching Behaviors of RTO WO(X) RRAM
(2010-02-01)
Chien, W. C.
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Chen, Y. C.
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Lai, E. K.
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Yao, Y. D.
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Lin, P.
The microstructure and electrical properties of the WO(X)-based resistive random access memory are investigated in this letter. The WO(X) layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WO(X) layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.
Unipolar Switching Behaviors of RTO WOX RRAM
(2010-02-01)
Chien, W. C.
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Chen, Y. C.
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Lai, E. K.
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Yao, Y. D.
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Lin, P.
The microstructure and electrical properties of the WOX-based resistive random access memory are investigated in this letter. The WOX layer is formed by converting the surface of the W plug with a CMOS-compatible rapid thermal oxidation process. The conductive-atomic-force-microscopy result indicates that nanoscale conducting channels exist in the WOX layer and result in a low initial resistance. This letter studies the unipolar operation-the programming, reading, and reliability behaviors of the device are characterized systematically. The low programming voltages for RESET (3.3 V/50 ns) and fast SET speed (3 V/300 ns) are achieved along with cycling endurance greater than 10(7) times. In addition, the device is immune to read disturb. A 2-bit/cell operation is also demonstrated for high-density applications.