• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.4
• /
• pp.407-414
• /
• 2016

As wind turbines are getting larger in size with multi-MW capacity, the blades are getting longer, over 40 m, and hence the asymmetric loads produced during the rotation of the rotor blades are increasing. Some factors such as wind shear, tower shadow, and turbulence have an effect on the asymmetric loads on the blades. This paper focuses on a method of modeling the dynamic load acting on a blade because of thrust variation under wind shear. A method that uses thrust coefficient is presented. For this purpose, "wind shear coefficient of thrust variation" is defined and introduced. Further, we calculate the values of the "wind shear coefficient of thrust variation" for a 2 MW on-shore wind turbine, and analyze them for speeds below the rated wind speed. Then, we implement a dynamic model that represents the thrust variation under wind shear on a blade, using MATLAB/Simulink. It is shown that it is possible to express thrust variations on three blades under wind shear by using both thrust coefficient and "wind shear coefficient of thrust variation."

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.3
• /
• pp.43-53
• /
• 2022

In this study, analysis of the flow characteristics of pintle-controlled nozzle with split-line TVC system and the thrust performance prediction was performed. The numerical computation was verified by comparing the thrust coefficient derived from the analysis results with the experimental data. By applying the same numerical analysis technique, the flow characteristics of nozzle were confirmed according to operating altitude, pintle stroke position and TVC angle with the 1/10 scale. As the TVC angle increased, thrust loss occurred and the tendency of AF was different depending on the position of the pintle stroke. Based on the analysis results, the relation of thrust coefficient was derived by applying the response surface methods. The thrust performance model with a slight difference of 1.2% on average from the analysis result was generated.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.4
• /
• pp.57-66
• /
• 2001

The precise prediction of the performance is essential to develope the system at the development of propulsion system since no experimental data are available. The accuracy of 1on the total system's performance as well as itself, which depends on how the correction fac $I_{sp}$, and so on, are determined in accurate. However some of the design factors are dete engineer's experience or the similar test data if they are available, so far. This study was the method of the determination of correction factors of both $I_{sp}$ and thrust in direct. The bas is to define the detail performance loss mechanism of solid rocket motors, might be occurre and to calculate in quantitative those correction factors from the performance loss mechanism the test results, the model of this study can predict those factors less than 1% error, in additi physical variances of each loss mechanism.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.8
• /
• pp.744-749
• /
• 2011

In this study, determination method of initial optimal nozzle expansion in pintle rocket was investigated. The initial optimal initial nozzle expansion was decided by maximizing the mass-averaged thrust coefficient that is calculated from thrust coefficient of minimum and maximum chamber pressure. The determination of initial optimal initial nozzle expansion was equivalent to that of the minimum propellant mass which was required for obtaining the desired mission performance. The highest pressure, thrust turndown ratio and total impulse ratio effected on the initial optimal nozzle expansion. Among them, total impulse ratio had great influence on the initial optimal nozzle expansion.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.4
• /
• pp.59-67
• /
• 2016

Numerical simulations have been performed to investigate thrust characteristics of a through-type pintle nozzle with or without flow separation at various operating altitudes. The low Reynolds number $k-{\varepsilon}$ with compressibility correction proposed by Sarkar are applied. The detail flow structures are observed and static pressures along nozzle wall are compared with experimental results. The flow separation in the pintle nozzle disappears and jet plume strongly expands as its operating altitude increases. To evaluate the thrust characteristics, the momentum term and pressure term of thrust are analyzed. Thrust and thrust coefficient at altitude 20 km are about 10% more than them at the ground 0km.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.4
• /
• pp.89-95
• /
• 2005

Thrust cut off(TCO) system is installed at the port of a rocket motor case forward dome. The snap ring and the closure are escaped sequentially by pulling out a wedge under internal pressure. The hydraulic structural tests of TCO and numerical simulations were performed, and both results were compared to understand the deformation behavior of TCO. By increasing splines symmetrically, the sealing capacity of TCO can be improved significantly. The escape pressure of TCO increases according to the increase of friction coefficient and there is a critical friction coefficient beyond which the snap ring can not be nearly escaped even after forced escape of wedge. Under low friction coefficient the snap ring is contracted to radial direction and easily escaped. But, under high friction coefficient, the snap ring can not be escaped from the port even after severe plastic deformation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.3
• /
• pp.65-71
• /
• 2003

In this research, we make the thin wall chamber to the measurement of heat flux of using a Kerosene/LOx liquid rocket engine's thrust chamber. The wall thickness is one millimeter. We measured outside wall temperature of thrust chamber by nine thermocouple. We suppose the system to the one-dimension unsteady state, and so the heat flux and heat transfer coefficient of thurst chamber are calculated using one-dimensional the transient energy equation by outside wall temperature. In this case, O/F ratio is 2.0, experimental variation is chamber pressure and we got the heat transfer coefficient of the proportion relation of 0.88 times for the chamber pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.9
• /
• pp.723-730
• /
• 2014

Experimental study for supersonic co-flowing fluidic thrust vectoring control utilizing the secondary flow is performed. The characteristics of the thrust vectoring of two dimensional supersonic flow (Mach 2.0) are studied by Schlieren flow visualization and highly-accurate multi-component force measurements using the load cells. It is observed that the thrust deflection angle initially decreases and increases again forming a V-shaped variation as the pressure of the secondary flow increases. Characteristics of the performance coefficients of the system are also studied, and the detailed operating conditions for higher performance of the technique are suggested.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.5
• /
• pp.93-99
• /
• 2003

The determination of thrust is essential in design and evaluation of a hypersonic airbreathing propulsion device. Conventional methods to determine the thrust is using thrust stand or force measurement system. However, these conventional methos are not applicable to the case where thrusts stands are impractical, such as free jet testing of engines, and model combustor. For this reason, the thrust determination method from measured pitot pressure is considered and validated. Validation of thrust determination from pitot pressures can be achieved by comparing the actual thrust from thrust stand. For validation purpose, a small-scale supersonic wind tunnel is installed on the thrust stand. Thrusts are measured while pressures are measured simulaneously. Then, the thrust from pitot pressure measurements are compared with the measured thrust and theoretical thrusts.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.392-394
• /
• 2017

In this study, the surface heat transfer coefficient of the 3D model of a thruster regulator in the high temperature and high pressure environment was estimated using the CFD. The thermal barrier coating (TBC) on the surface of the thruster regulator was modeled and the effect of the thickness of the TBC on the temperature of the thruster regulator was investigated. The thickness of the TBC was varied from $100{\mu}m$ to $500{\mu}m$. Results showed that the temperature of the surface and the inside the thruster regulator was lower for the thicker TBS case.