• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.90-96
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• 2012

In order to determine optimal design length of adhesive joint of a composite rocket motor case, stress analysis of joint part according to changes of adhesive length was done. Adhesive length has a range of 50 mm to 300 mm as design variables. The ratio of adhesive length without any stress gradient to initial non-stressed adhesive length was determined as evaluation criteria for selection of adhesive length, which called "stress gradient length ratio". The numerical result showed that stress gradient length ratio of joint part with adhesive length of more than 200 mm was increased very slowly with increase of adhesive length. It means that adhesive length of about 200 mm could be the optimal dimension to ensure the structural safety of joint part against internal pressure of 2,500 psi.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.35-47
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• 2011

Dynamic characteristics of a flow control valve, which plays an important role in thrust and O/F control of liquid rocket engines, have been analyzed by the AMESim simulator modeling. The speed control method was proposed for the control of the flow valve equipped with a BLDC motor. The experimental results demonstrated the feasibility of systematical application as well as the performance of the speed control method. Moreover, the speed control method for BLDC motor is much simpler than the P control method in complex flow systems. With the speed control method, the control flow characteristics were evaluated according to plunger shapes. Consequently, same plunger shape proved to be more efficient in the mixture ratio control operated by two flow valves. It was also shown that the appropriate modification of plunger shapes could reduce the mixture ratio perturbation by 0.5%.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.32-36
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• 2016

Test equipment was designed and manufactured to evaluate thermal reaction characteristic of internal insulators of solid rocket motor. Test is allowed up to chamber pressure 2,500 psi, burn-time 100 s. A cross section of test sample part is quadrature, and various test samples can be comparable at the same time. Inner temperature of test sample can be measured by thermocouples during burning. Test was executed in condition of efficient average chamber pressure 1,000 psi, efficient burn-time 10 s and safety of equipment was confirmed. Basic data for understanding thermal characteristics of internal insulator, that is, pressure-time curve, temperature-time curve in the test sample, and thermal destruction thickness of test sample was gained successfully.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.17-26
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• 2004

In this paper, power transmission systems converts the shaft power of a Turbo-shaft Engine with Free Power Turbine into the generator power and be composed of a method being supplied in the thrust motor driving a propellers. Being used this, Gas turbine engine works to flat rating about 110 kw (147 shp) that the thrust motor be extremely supplied from the engine of 317shp. In this test equipment, the engine is installed with the flywheel being able to the damping function when happen to the varying load between gas turbine engine output-shaft and generator. Then if the flywheel of inertial moment be not considered, the generator and motor not get the required power from the engine for raising the load. Also it is certified that the engine works the abnormal operation. Hence the flywheel of inertial moment is determined the required range to do the performance analysis with the dynamic transient from the given and tested engine data. This system is able to get the required power after a mounting test with the redesigned flywheel.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.61-65
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• 2006

A thery was developed to design a high pressure vessel with combined structure of the metal and the composite to withstand the pressure of several tens of thousands psias to reduce the weight of the impulse motor which produces high level of thrust within several tens of seconds. The elastic-plastic stress analyses were carried out to prove the validity of the design theory A combustion chamber of the impulse motor was designed by the design theory, fabricated, and tested by the hydraulic pressure and the static firings. The bursting pressures from the tests were compared to those predicted by tile design theory and the stress analyses and found to be almost the same. It will be possible to design the high pressure vessel with combined structure of the metal and the composite very easily by the proposed design theory.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.233-236
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• 2009

In this study, the characteristic of the hybrid rocket motor with $LN_2O$(Liquid Nitrous oxide) was investigated experimentally. HDPE(High Density PolyEthlene) was used as fuel with different sized single port. When used $LN_2O$, combustion efficiency is lower than using $GN_2O$(Gas Nitrous oxide), because of completeness of vaporization of droplet and mixing. And regression rate was changed by different oxidizer phase. This behavior was considered that flame temperature and combustion of solid fuel front/end surface.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.2
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• pp.28-34
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• 2020

In order to relieve the burden of the rear ablative material, the combustion test of the solid rocket motor with the forward deployed multi-pin grain design was successfully performed twice. However, after disassembling the solid rocket motor, a non-uniform ablation pattern was found in the rear ablative material. Periodic repetition of local and regional ablation was measured precisely. Two-dimensional flow and eddy flow, created by the uneven main-pin flow hitting the rear ablative material, were identified as the cause of non-uniform ablation. In addition. when the rear pins were removed, the possibility of securing the soundness of the rear ablative material was confirmed as the average flow velocity and the standard deviation were lowered.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.112-118
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• 2004

Recently, development of rare earth permanent magnet with the high remanence, high coercivity allows the design of brushless motors with very high efficiency over a wide speed range. Cogging torque is produced in a permanent magnet by magnetic attraction between the rotor mounted permanent magnet and the stator teeth. It is an undesired effect that contributes to output ripple, vibration, and noise of machine. This cogging torque can be reduced by variation of magnet arc length, airgap length, magnet thickness, shifting the magnetic pole and varying the radial shoe depth and etc. In this paper, some airgap length and magnet arc that reduce cogging torque are found by finite element method(FEM) and Maxwell stress tensor method. The SPM(Surface Permanent Magnet) type of high-power Brushless DC (BLDC) motor is optimized as a sample model.

• International Journal of Automotive Technology
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• v.4 no.2
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• pp.87-94
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• 2003

Recent advancements of permanent magnet (PM) materials and solid-state devices have contributed to a substantial performance improvement of permanent magnet machines. Owing to the rare-earth PMs, these motors have higher efficiency, power factor, output power per mass and volume, and better dynamic performance than induction motors without sacrificing reliability. Not surprisingly, they are continuously receiving serious considerations for a variety of automotive and propulsion applications. An electric vehicle (EV) requires a high-effficient propulsion system having a wide operating range and a capability of generating a high peak torque for short durations. The improvement of torque-speed performance for these systems is consequently very important, and researches in various aspects are therefore being actively pursued. A great emphasis has been placed on the efficiency and optimal utilization of PM machines. This requires attention to many aspects related to the machine design and overall performance. In this respect, the prediction of iron losses is particularly indispensable and challenging, especially for drives with a deep field-weakening range. The objective of this paper is to present iron loss estimations of a PM motor over a wide speed range. As aforementioned, in EV applications core losses can be significant during high-speed operation and it is imperative to evaluate these losses accurately and take them into consideration during the motor design stage. In this investigation, the losses are predicted by using an analytical model and a 2D time-stepped finite element method (FEM). The results from different analytical approaches are compared with the FEM computations. The validity of each model is then evaluated by these comparisons.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.71-78
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• 2007

An experimental investigation was conducted to clarify the combustion characteristics of Polyethylene-GOX(PE-GOX) hybrid motor using a single-port fuel grain configuration. Data from the experiments were analyzed to evaluate the length-averaged regression rate of PE-GOX propellants. Based on the existing theories, the empirical regression rate formulas provided from Marxman[3,4] and Altman[14] showed good concordance with the PE-GOX experiments. The accuracy of the regression rate was then evaluated and compared with the measured one. As a result, Marxman's model was somewhat more precise than Altman's model in these experiments. Moreover, the consideration of the empirical regression rate showed that O/F ratio has minor variation due to the quasi constant inflow of the fuel during motor firing.