• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.28-36
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• 2016

Theoretical model of a variable thrust solid rocket motor with a pintle nozzle was derived. For the chamber pressure control, classical model linearization and proportional-intergral controller was used. And then two types of gain scheduling controller were suggested to imporve controller performance for the non-linear propulsion model. Considering characteristics of systems, control gains were scheduled by chamber pressure or free volume. Step responses of each controllers were compared. As a result, the proper control algorithm about characteristics of variable thrust rocket motor was suggested.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.167-174
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• 2011

Solid propulsion systems have simple structures compared to other propulsion systems and are suitable to long-term storage. However the systems generally have limits on control of thrust levels. In this paper we suggest control algorithms for combustion chamber pressure of variable thrust solid propulsion systems using special nozzles such as pintle valve. For this we use a simple pressure change model by considering only mass conservation within the combustion chamber, design a classical algorithm and also a nonlinear controller using feedback linearization technique. Derived thrust equation and designe a thrust control model. We design the proportion-integral controller for linearizing about operating point. We also demonstrate the performance of controller model through numerical simulations.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.18-25
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• 2011

Solid propulsion systems have simple structures compared to other propulsion systems and are suitable for long-term storage. However the systems generally have limits on control of thrust levels. In this paper we suggest control algorithms for combustion chamber pressure of variable thrust solid propulsion systems using special nozzles such as pintle valve. For the pressure control within the chamber, we use a simple pressure change model by considering only mass conservation within the combustion chamber, design a classical algorithm and also a nonlinear controller using the feedback linearization technique. Also we derive the equation of the thrust for an under-expanded one-dimensional nozzle and then design a proportional-intergral controller after linearizing the thrust model for an operating point. Finally, we demonstrate the performance of the controller through a numerical simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.49-58
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• 2018

This paper introduces a research on the control method design for the subsonic intake flow of a dual-combustion ramjet engine. To design the control method, the intake flow dynamic response characteristics, based on a designated flow condition and intake geometry, are investigated, and a control method concept considering the intake flow characteristics is established. Using a dynamic simulation model of a dual-combustion ramjet, control input/output linearized models are obtained such that a control loop design based on linearized models can be accomplished. Finally, from various control loop simulations, the performance of the control method, including its control loop stability, is evaluated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.445-455
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• 2010

In order to effectively predict thermo-acoustic instability within real combustors of rocket engines and gas turbines, in the present study, the Helmholtz equation in conjunction with the time lag hypothesis is discretized by the finite element method on three-dimensional hybrid unstructured mesh. Numerical nonlinearity caused by the combustion response term is linearized by an iterative method, and the large-scale eigenvalue problem is solved by the Arnoldi method available in the ARPACK. As a consequence, the final solution of complex valued eigenfrequency and acoustic pressure field can be interpreted as resonant frequency, growth rate, and modal shape for acoustic modes of interest. The predictive capabilities of the present method have been validated against two academic problems with complex impedance boundary and premixed flame, as well as an ambient acoustic test for liquid rocket combustion chamber with/without baffle.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.157-166
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• 2014

A light water reactor (LWR) fuel rod consists of zirconium alloy cladding tube and uranium dioxide pellets with a slight gap between them. The modeling of heat transfer across the gap between fuel pellets and the protective cladding is essential to understanding fuel behavior under irradiated conditions. Many researchers have been developing fuel performance codes based on finite element method (FE) to calculate temperature, stress and strain for multidimensional analysis. The gap conductance model for multi-dimension is difficult issue in terms of convergence and nonlinearity because gap conductance is function of gap thickness which depends on mechanical analysis at each iteration step. In this paper, virtual link gap element (VLG) has been proposed to resolve convergence issue and nonlinear characteristic of multidimensional gap conductance. In terms of calculation accuracy and convergence efficiency, the proposed VLG model has been evaluated for variable cases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.505-511
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• 2015

Solid oxide fuel cell operate at high temperature ($800{\sim}1000^{\circ}C$). High temperature have an advantage of system efficiency, but a weak durability. In this study, linear state space controller is designed to handle the temperature of solid oxide fuel cell system for proper thermal management. System model is developed under simulink environment with Thermolib$^{(R)}$. Since the thermally optimal system integration improves efficiency, very complicated thermal integration approach is selected for system integration. It shows that temperature response of fuel cell stack and catalytic burner are operated at severe non-linearity. To control non-linear temperature response of SOFC system, gain scheduled linear quadratic regulator is designed. Results shows that the temperature response of stack and catalytic burner follows the command over whole ranges of operations.