• International Journal of Automotive Technology
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• v.8 no.3
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• pp.361-373
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• 2007

In previous work, an approach based on maximizing the efficiency of an internal combustion engine while ignoring the power conversion efficiency of other powertrain components, such as the electric motor and power battery or ultracapacitor, was implemented in the steady-state optimization of an internal combustion engine for hybrid electric vehicles. In this paper, a novel control algorithm was developed and successfully justified as the basis for maximal power conversion efficiency of overall powertrain components. Results indicated that fuel economy improvement by 3.9% compared with the conventional control algorithm under China urban transient-state driving-cycle conditions. In addition, using the view of the novel control algorithm, maximal power generation of the electric motor can be chosen.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.473-481
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• 2001

By depicting the transfer of heat and combustion reaction to take place within thin gas layers close to the propellant surface burning in a steady-state fashion, a mathematical equation has been deduced to describe the burning rate of solid propellant as a function of initial grain temperature and chamber pressure. It has been also assumed that chemical reaction could take place in premixing-diffusing zone but were carried out mainly in the reaction-flame zone. All these phenomena taken place in each zone of combustion have been assumed to be steady-state. In the present investigation, the equation, γ=$\kappa$$.$(1/R(T(sub)i+C))(sup)n$.$exp(-E(sub)a/R(T(sub)i+C))(P/z) is being presented and it is compared with experimental data. The proposed model has been tested and evaluated vis-a-vis strand burner data for three different propellants based on CTPB, and it has been found that the deviation of the computed burning rates from the measured rates ranged up to 2%.

• Journal of the Korean Society of Combustion
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• v.5 no.1
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• pp.1-6
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• 2000

Surface reaction occurs at a certain surface temperature when a catalyst is heated up in a reactive mixture. If homogeneous ignition does not occur, a steady state is observed because the heat produced by the surface reaction is balanced with the heat loss caused by convection, conduction and radiation. The present paper treats the effects of pressure on the surface temperature at the steady state. Hydrogen and oxygen are used as reactants and nitrogen as an inert gas. A spherical platinum catalyst of 1.5 mm in diameter is sustained in the chamber with two wires of 0.1 mm in diameter. As results, there exists a maximum steady temperature at a certain relative hydrogen concentration which increases with total pressure. At the steady state, it can be approximated that the heat release is estimated by the mass transfer considering the effect of natural convection. The experimental results are explained qualitatively by the approximation.

• Journal of the Korean Society of Combustion
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• v.19 no.3
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• pp.44-52
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• 2014

Solid oxide fuel cell(SOFC) makes electric power using hydrogen or reformed from methane and emits high temperature products that contain flammable species like hydrogen, carbon monoxide and methane which varies with operation condition. SOFC/gas turbine integrated system which uses thermal and chemical energy of the discharges is more efficient than SOFC itself. Burning character of the SOFC products will affect the efficiency and stability of the system. Experiments were conducted to know the characteristics of the flame for two typical composition of SOFC products, i.e. start-up and steady state composition. When coflowing air temperature was higher than $600^{\circ}C$, auto-ignitin occurred for both fuels. Though start-up fuel has higher contents of hydrogen, it makes longer flame than steady state composition. It was inferred that the amount of oxidizer necessary to burn makes this phenomenon. Steady state composition fuel was unstable since it contains lots of water. Nozzle that had 6 holes, distance between each hole was 16.7 times of hole diameter, improved the stability of the flame.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.43-51
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• 1997

Steady and unsteady numerical simulations are conducted for the experiments performed to investigate the ram accelerator flow field by using the expansion tube facility in Stanford University. Navier-Stokes equations for chemically reacting flows are analyzed by fully implicit and time accurate numerical methods with Jachimowski's detailed chemistry model for hydrogen-air combustion involving 9 species and 19 reaction steps. Although the steady state assumption shows a good agreement with the experimental schlieren and OH PLIF images for the case of $2H_2$+$O_2$+$17N_2$, it fails in reproducing the combustion region behind the shock intersection point shown in the case of $2H_2$+$O_2$+$12N_2$, mixture. Therefore, an unsteady numerical simulation is conducted for this case and the result shows all the detailed flow stabilization process. The experimental result is revealed to be an instantaneous result during the flow stabilization process. The combustion behind the shock intersection point is the result of a normal detonation formed by the intersection of strong oblique shocks that exist at early stage of the stabilization process. At final stage, the combustion region behind the shock intersection point disappears and the steady state result is retained. The time required for stabilization of the reacting flow in the model ram accelerator is found to be very long in comparison with the experimental test time.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.05a
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• pp.45-52
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• 2001

The study on the heat exchanger with catalytic combustion was performed as the development of the catalytic combustion applications. This study tried to achieve the both goals-the mixture preheating and the heat transfer to working fluid simultaneously by using the steady state catalytic combustion. The combustion characteristics were investigated with the quantitative, qualitative experimental variants of the mixture. In addition, the temperature distribution of catalytic layer was investigated to investigate the correlation between the combustion characteristics and the heat balance of the catalytic layer. As a result, the steady state reaction within the appropriate range of temperature is the critical factor in catalytic applications. To get this, the sensible control of both the mixture flow and the heat balance of catalytic layer were required.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.47-57
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• 1998

Characteristics of evaporation, flame propagation at moment of ignition and steady state combustion, and flow characteristics of combustible mixture have been investigated by experiments and computational simulation for the evaporation pot type kerosene burner. The results show how to design the evaporation pot in order to minimize the sticking of residual tar, and also indicate that symmetrical flame propagation along the flame ring from the kernel of ignition is achieved by modication of the shape of ignition part. In the case of steady state combustion, the uniform distribustion of flame at each flame hole is accomplished by proper modification of the piping instruments. The improved design of the structure and parts of the kerosene burner make up enhancement of flame stability and considerable reduction of CO and bad smell emission at moment of ignition.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.2
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• pp.75-84
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• 2002

A numerical analysis of unsteady motion in solid rocket motors with a nozzle has been conducted. The numerical formulation including modified $\kappa$-$\varepsilon$ turbulence model treats the complete conservation equation for the gas phase and the one-dimensional equations in the radial direction for the condensed phase. A fully coupled implicit scheme based on a dual time-stepping integration algorithm has been adopted to solve the governing equations. After obtaining a steady state solution, pulse and periodic oscillations of pressure are imposed at the head-end to simulate acoustic oscillations of a travelling-wave motion in the combustion chamber. Various steady and unsteady state features in the combustion chamber of a rocket motor has been analyzed as results of numerical calculations.

• Journal of Environmental Science International
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• v.6 no.3
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• pp.267-276
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• 1997

It has been studded that combustion and the production of air pollution of anthracite - bituminous coal blend In a fluidized bed coal combustor, The objects of thIns study were to investigate mixing characteristics of the particles as well as the combustibility of the low grade domestic anthracite coal and Imported h19h calorific bltununous coal in the fluidized bed coal combustor. They were used as coal samples ; the domestic low grade anthracite coal with heating value of 2,010kca1/kg and the Imported high grade bituminous coal with beating value of 6,520kca1/kg. Also, the effects of air flow rate and anthracite fraction on the reaching time of steady state condition have been studied. The experimental results are presented as follows. The time of reaching to steady state was affected by the temperature variation. The steady state time was about 120 minute at 300sc1h which was the fastest. It has been found that $O^2$ and $CO^2$ concentration were reached steady state at about 100 minute. It has been found that $O^2$ concentration decreased and $CO^2$ concentration increased as the height of fluidlzed bed Increased. It was found that splash zone was mainly located from 25cm to 35cm above distributor. Also, as anthracite traction Increased, the mass of elutrlatlon particles Increased, and $CO^2$ concentration decreased. As gk flow rate Increased,$O^2$ concentration decreased and $CO^2$ concentration increased. Regardless of anthracite fraction and flow rate, the uncombustible weight percentage according to average diameter of elutriation particles were approldmately high In the case of One Particles. As anthracite traction and k now rate Increased, elutriation ratio Increased. As anthracite fraction was increased, exit combustible content over feeding combustible content was Increased. Regardless of anthracite fraction, size distribution of Ued material from discharge was almost constant. Over bed temperature 85$0^{\circ}C$ and excess air 20% , the difference of combution efficiencies were little. It is estimate that the combustion condition In anthracite-bituminous coal blend combustion is suitable at the velocity 0.3m/s, bed temperature 85$0^{\circ}C$, the excess air 20%.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.117-127
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• 1997

To maintain the reasonable temperature in the engine is very important to keep the steady combustion state of engine and to prevent increasing of lubricant consump- tion, deteriorating of lubricant, shortening of the life time of engine and decreasing of material strength. The method of energy balance for devided elements of radiator is considered to analyse the performance of radiator. Th data of engine test and vehicle cooling tunnel test are applied to program for calculation of radiator outlet temperature, and this result is compared with outlet temperature of vehicle cooling tunnel test. As a result, the radiator outlet temperature by numerical analysis agrees well with that by experiment. It is concluded that this simulation program is available in developing the cooling system for a new car.