• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.05a
• /
• pp.197-201
• /
• 2010

Precise control of oxidizer mass flow rate is important for hybrid rocket thrust control. In this study, oxidizer mass flow rate control system is developed by using stepping motor which is controlled by Labview program. Gox is used for oxidizer and PolyCarbonate, PolyEthylene, and PMMA is used for solid propellant. To suppress thrust oscillation during thrust control experiment, schematics of the experiment is analysised and revised. Results show that thrust oscillation is suppressed successfully.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.1
• /
• pp.55-62
• /
• 2011

In this study, we tried to improve the thrust control performance through the thrust control combustion experiment of the hybrid rocket. We constructed the system which controls the oxidizer flow by combining a needle valve with a stepping motor and controlling the stepping motor drive according to the thrust control command order. Gas oxygen was used as the oxidizer for two different propellants, PE(Polyethylene), PC(Polycarbonate), respectively. To improve the slow response time and the oscillation phenomenon in the beginning stage of the thrust control combustion experiment, we measured and analyzed the change of the flow speed of the propellant pipe. The revised thrust control combustion experiment showed that the thrust was stably controlled with the margin or error from the thrust command within ${\pm}1$ N.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.282-286
• /
• 2004

Discharge current oscillation in a 20KHz range is a serious problem for Hall thruster performance, In our previous work, a possibility of controlling the oscillation amplitude by increasing the speed of neutral particles incoming to the ionization zone was predicted in our previous work. In this paper, the effects of diameter of anode orifice on the oscillation phenomena and the thrust performance were evaluated experimentally. The experimental results show that the measured amplitude of oscillation becomes smaller as the diameter of anode orifice. However, the larger orifice makes thrust performance lower. The results of numerical analysis of neutral particles show that these tendencies have much to do with neutral properties.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.3
• /
• pp.1-8
• /
• 2015

A ground hot-firing test(HFT) was accomplished to draw a correlation between the pressure oscillation intensity of combustion chamber and thrust response characteristics in a 70 N-class hydrazine thruster which has been developed recently. Monopropellant grade hydrazine was adopted as a propellant for the HFT, and combustion-chamber characteristic length, propellant injection pressure were applied as test parameters. It was confirmed that the decrease of thrust-chamber diameter and injection pressure augmented the pressure oscillation of stagnation chamber in the test condition specified, and the oscillation hampered the pulse response performance of test models.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.209-212
• /
• 2006

Insect and birds in nature flap their wings to generate fluid dynamic forces that are required for the locomotion. Most of the previous published papers discussed mainly on the effect of flapping parameters such as flapping frequency and amplitude on the thrust at a fixed Reynolds number. However, it is not much known on the values of the flapping parameters that the flapping wing requires to generate the thrust at the low Reynolds number flow. In this paper, the onset of the thrust generation is investigated using the lattice Boltzmann method. The wake patterns and velocity profiles behind a flat plate in heaving oscillation are investigated for the heaving amplitude of 0.5C. The time-averaged thrust coefficient value is investigated by changing the reduced frequency from 0.125 to 3.0 for three values of heaving amplitude (h/C=0.25, 0.325, 0.50). It is also found that the critical Strouhal number over which the flat plate starts to produce the thrust is around 0.1 and the thrust is an exponential function of the Strouhal number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.05a
• /
• pp.231-238
• /
• 2010

Combustion stability rating tests under condition low pressure of a 75-$ton_f$ liquid rocket engine(LRE) thrust chamber were carried out. Mixing head with decreased number of injectors than that of the other but with the same mass flow rate to the combustion chamber showed self-oscillation instability in chamber pressure of 30 bar. The other combustion chamber with increased number of injectors showed that high frequency combustion stability was maintained under condition of same pressure, but self-oscillation instability was generated in chamber pressure of 20 bar which can be considered as stability boundary region of this mixing head.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.574-578
• /
• 2008

In order to achieve thrust vector control and discharge stabilization in Hall thrusters, the azimuthal nonuniformity of propellant flow rate in an acceleration channel was created. A plenum chamber was divided into two rooms by two walls and propellant flow rate supplied to each section was independently controlled. In a magnetic layer type Hall thruster, steering angle of up to ${\pm}2.3$ degree was achieved. In an anode layer type Hall thruster, discharge current oscillation amplitude was decreased with the normalized differential mass flow rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.5
• /
• pp.397-403
• /
• 2007

Insect and birds in nature flap their wings to generate fluid dynamic forces that are required for locomotion. To develop a feasible flapping MAV, it is of crucially important to study the fundamental relations between flapping motion and thrust generation. In this paper, the onset conditions of the thrust generation of a heaving flat plate is investigated using a Lattice-Boltzmann method. For a fixed heaving amplitude of h/C=0.5, the effect of reduced frequency on the thrust generation is investigated. For several values of heaving amplitude(h/C=0.25, 0.325, 0.50), the effect of reduced frequency on the thrust generation is also investigated. It can be said that Strouhal number is more important rather than reduced frequency in case of thrust generation. It is found that the critical Strouhal number over which the flat plate starts to produce thrust is around 0.1. Thrust is an exponential function of the Strouhal number.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.14 no.3
• /
• pp.52-60
• /
• 2010

Combustion stability tests of 30 $ton_f$-class LRE thrust chamber with double swirl coaxial injector were carried out in domestic ground combustion test facility by means of artificial perturbation method. In these tests, thrust chambers with varying design factors like recess number of injector, baffle length, types of film cooling and chamber diameter were used and test results showed that these design factors are closely related with high frequency combustion stability. By using the oscillation decrement instead of the decay time in the combustion stability analysis of artificially perturbed LRE thrust chamber, it was confirmed that increment of damping factor results in the improvement of high frequency combustion stability of LRE thrust chamber.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.10
• /
• pp.905-911
• /
• 2011

With the progress of micro actuator technology, studies on the development of micro air flapping wing vehicles are actively undergoing. In the present study, the changes of both lift and thrust characteristics of the wings are investigated using a boundary element method. Lift of the heaving wing is not generated when the wing is beating with smaller frequencies than 1 Hz. Thrust increases with amplitude and frequency. As the wing's taper and aspect ratios increase, both lift and thrust also increase. Results on the pitching oscillation and flapping motion will be included in the future work.