Browsing by Author "Lai, A."

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COMPARISON OF THE PROPULSION PERFORMANCE OF AEROSPIKE AND BELL-SHAPED NOZZLE USING HYDROGEN PEROXIDE MONOPROPELLANT UNDER SEA-LEVEL CONDITION
(2019-06-01)
Lai, A.
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Wei, S. S.
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Lai, C. H.
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Chen, J. L.
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Liao, Y. H.
This study investigates numerically the performance of applying aerospike nozzle in a hydrogen peroxide mono-propellant propulsion system. A set of governing equations, including continuity, momentum, energy and species conservation equations with extended k-epsilon turbulence equations, are solved using the finite-volume method. The hydrogen peroxide mono-propellant is assumed to be fully decomposed into water vapor and oxygen after flowing through a catalyst bed before entering the nozzle. The aerospike nozzle is expected to have high performance even in deep throttling cases due to its self-compensating characteristics in a wide range of ambient pressure environments. The results show that the thrust coefficient efficiency (C-f,C-eta) of this work exceeds 90% of the theoretical value with a nozzle pressure ratio (PR) in the range of 20 similar to 45. Many complex gas dynamics phenomena in the aerospike nozzle are found and explained in the paper. In addition, performance of the aerospike nozzle is compared with that of the bell-shape nozzle.
Investigation of Dual-Vortical-Flow Hybrid Rocket Engine without Flame Holding Mechanism
(2018-01-01)
Lai, A.
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Chou, T. -H.
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Wei, S. -S.
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Lin, J. -W.
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Wu, J. -S.
A 250 kgf thrust hybrid rocket engine was designed, tested, and verified in this work. Due to the injection and flow pattern of this engine, this engine was named dual-vortical-flow engine. This propulsion system uses N2O as oxidizer and HDPE as fuel. This engine was numerically investigated using a CFD tool that can handle reacting flow with finite-rate chemistry and coupled with the real-fluid model. The engine was further verified via a hot-fire test for 12 s. The ground I-sp of the engine was 232 s and 221 s for numerical and hot-fire tests, respectively. An oscillation frequency with an order of 100 Hz was observed in both numerical and hot-fire tests with less than 5% of pressure oscillation. Swirling pattern on the fuel surface was also observed in both numerical and hot-fire test, which proves that this swirling dual-vortical-flow engine works exactly as designed. The averaged regression rate of the fuel surface was found to be 0.6 similar to 0.8 mm/s at the surface of disk walls and 1.5 similar to 1.7 mm/s at the surface of central core of the fuel grain.
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.