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Technical Briefs

Investigation of Heat Transfer and Scale Effects on the Performance of a Giffard Injector-Pumped Microrocket

[+] Author and Article Information
Natalya A. Brikner1

 Graduate Research Assistant e-mail: natalya.brikner@duke.edu Graduate Research Assistant e-mail: wgg2@duke.eduAssistant Professor Mem. ASME e-mail: jonathan.protz@duke.edu Department of Mechanical Engineering and Materials Science,  Duke University, Durham, NC 27705

William G. Gardner, Jonathan M. Protz

 Graduate Research Assistant e-mail: natalya.brikner@duke.edu Graduate Research Assistant e-mail: wgg2@duke.eduAssistant Professor Mem. ASME e-mail: jonathan.protz@duke.edu Department of Mechanical Engineering and Materials Science,  Duke University, Durham, NC 27705

A decrease in pressure of 15–20% of the chamber pressure is typical across the manifold and helps to ensure adequate mixing and atomization of the propellants in the combustion chamber [14].

For engine performance calculations that require the temperature of the exhaust gas at the exit plane of the rocket, T∞ is reduced by considering the heat transferred from the exhaust flow to the walls.

1

Corresponding author.

J. Thermal Sci. Eng. Appl 3(4), 044503 (Oct 24, 2011) (6 pages) doi:10.1115/1.4005074 History: Received August 18, 2010; Revised September 05, 2011; Accepted September 06, 2011; Published October 24, 2011; Online October 24, 2011

A novel approach to propellant pressurization for microscale rocket engines is introduced. The Giffard injector is shown to be a viable alternative to turbomachinery for pressurizing the liquid propellants on board a microrocket, offering a design free of moving parts. Extending the authors’ previous work, the engine performance is computed for several fuel/oxidizer combinations. A large-scope study of the heat transfer throughout the regenerative cooling engine cycle examines the effects of combustion chamber pressure and engine size on performance. A boiler is designed that facilitates the heat transfer required for adequate cooling and is modeled using the effectiveness-number of transfer units method. The computed specific impulse and thrust-to-weight ratio of the design for the propellants considered are roughly 250 s and 2000, respectively. The power density of the proposed injector-pumped design is seen to behave like that of turbopumped microrockets up to a critical nozzle throat diameter of approximately 1 cm, beyond which the advantages of an entirely static structure are outweighed by decreasing performance.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Regenerative cooling engine cycle, showing propellant flow paths and main components

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Figure 2

Schematic of injector implemented in design

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Figure 3

Maximum discharge pressure versus tank temperature for propellants considered

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Figure 4

Friction factor and aspect ratio of boiler flue versus Reynolds number

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Figure 5

Ratio of weights of injector-pumped design to turbopumped design versus Reynolds number for ethanol and hydrogen peroxide

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Figure 6

Performance of engine for several propellant combinations. To illustrate use of the chart, a hydrogen peroxide/ethanol engine with a 2.5 mm nozzle throat would operate at a chamber pressure of roughly 40 atm, generating a thrust of 20 N, a thrust-to-weight ratio of 1000, and a specific impulse of 250 s. Larger nozzles offer higher thrust but the thrust-to-weight ratio decreases significantly.

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