• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.637-653
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• 1999

In this study well-known burned rate expressions of Weibe function and double Wiebe function have been adopted for the combustion analysis of large two stroke marine diesel engine. A cycle simulation program was also developed to predict the performance and pressure waves in pipes using validated burned rate function,. Levenberg-Marquardt iteration method was applied to cali-brate the shape coefficients included in double Wiebe function for the performance prediction of two-stroke marine diesel engine. As a result the performance prediction using double Wiebe func-tion is well correlated withexperimental dta with the accuracy of 5% and pressure waves in intake and transport pipe are well predicted. From the results of this study it can be confirmed that the shape coefficients of burned rate function should be modified using the numerical method suggested for the accurated prediction and double Wiebe function is more suitable than Wiebe func-tion for combustion analysis of large two stroke marine engine.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.368-373
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• 2015

As a preliminary study for the development of the gas fueled marine engine, prediction of indicated performances was carried out for a spark-ignition engine using commercial software, GT-POWER. The optimized models through a previous study were applied for the simulation of the intake and exhaust systems in a SI engine. The Spark-Ignition Wiebe model was used to calculate the burn rate in the cylinders and the modified Woschni model was used to calculate the heat transfer to the walls. The predicted performances, such as air delivery, cylinder pressures and indicated mean effective pressures under a range of operating conditions showed good agreement with the experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.26-36
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• 2010

This paper provides a description of the combustion model to obtain an accurate dynamic engine phenomena that satisfies real-time simulation for model-based engine control. The combustion chamber is modeled as a storage device for mass and energy. The combustion process is modeled in terms of a two-zone model for the burned and unburned gas fractions. The mass fraction burnt is modeled in terms of a Wiebe function. The instantaneous net engine torque is calculated from the engine speed and the instantaneous piston work. The modeling accuracy has been tested with a cylinder pressure data on a test bench and also the ability of real-time simulation has been checked. The results show that combustion model yields sufficiently good performance for the model-based control logic design. However the influence factors effected on model accuracy are some room for improvement.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.1
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• pp.91-101
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• 1986

Relations of each factor affected by emissions and the prediction of performance have been analyzed numerically by cycle simulation in the Spark Ignition Engine. Through theoretical analysis and experiments, the results are obtained as below. The calculated results and the experimental ones are almost highly agreeable on cycle simulation model, exhaust gas analysis and efficiency for processes in cylinder. Therefore this model is proved appropriate and can be useful for optimum design of Spark Ignition Engines on parametric studies. It is reaffirmed that the Wiebe's function is suitable for predicting Combustion Ration in Spark Ignition Engines. On parametric studies, it is found that optimum conditions whose density of emissions are lower and efficiency is maximum within propriety value are crankangle ATDC $15^\circ-20^\circ$, 2400 rpm. A/F=16 in this experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.80-89
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• 1993

Performance simulation for a Spark Ignition Wankel rotary Engine is presented in this paper. The volume of chamber at each eccentric shaft angle is evaluated by using geometric models of housing and rotor. A thermodynamic model which includes the first law of thermodynamics, combustion and convective heat transfer from chamber contents to surroundings is imployed. A thermochemical equilibrium model which considers 10 species(CO, $CO_2$, $O_2$, $H_2$, $H_2O$, OH, O, NO, $N_2$) in the burned gas region, is also employed. Four processes of gas exchange, compression, combustion and expansion are considered and the pressure, temperature and composition of chamber gas at each eccentric shaft angle in each process are computed in this performance simulation. This performance simulation must be useful for optimal design of Spark Ignition Wankel Rotray Engine with parametric study for various design parameters and operating conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.221-229
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• 1996

The engine speed fluctuation at idle operation mainly comes from cyclic variation of combustion in SI engine. In the present study, engineering model that is representing the cyclic variation of combustion was proposed for the sub-model of the engine cycle simulation. From the observed behaviors of the mass burn rates, probability density functions for the parameters of Wiebe function were defined. The mass burn rate of each cycle is obtained by Monte Cralo perturbation method with the probability function. The simulation results shows that trends of cylinder pressure variation and imep distribution follow up with those of experimental results at idle condition.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.4
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• pp.543-551
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• 1999

Diesel engine is a major source of the air pollution. In general the concentrations of these pollu-tants in diesel engine exhaust differ from values calculated assuming chemical equibrium. Thus the detailed chemical mechanisms by which these pollutions form and the kinetic of these process-es are important in determining emission levels. In this study the computer program has been developed to calculate the required thermodynam-ic properties of combustion products(10 spacies) for both equilibrium and non-equilibrium in cylin-der for diesel engines. Nitric oxide emissions are calculated by using the extended Zeldovich Kinet-ic mechanism with a steady state assumption for the N concentration and equilibrium values used for H, O, $O_2$ and OH concentrations. By the results it is confirmed that developed simulations program with the NO prediction model is validated against residual mass fraction combustion index of Wiebe's functions pre-mixed com-bustion ration fuel injection timing.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.658-665
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• 2014

Natural gas for marine diesel engine is considered as an important and clean source of energy because of simultaneously reducing the emission of NOx, SOx and GHG. Especially with a appearance of shale gas, the using of natural gas has been investigated aggressively and expected to expand rapidly. By the reports, gas engine and diesel engine were both in a similar performance in the power aspect, and the SFOC of gas engine was shown a little better than that of diesel engine. But the characteristics of exhaust gas emission were different according to various combustion technologies. And with lean burn technology, the emission of NOx could be reduced to 85% lower than that of diesel engine. In this paper, it was described that a simulation program has been developed to predict NOx emission. The developed program is adopted two-zone model and Wiebe function for combustion in cylinder. The effects of premixed and diffusive combustion could be simulated by using the excess air ratio as input data. And it was confirmed that the results of simulation were agreed with the general trends of exhaust gas emission according to various combustion conditions such as lean burn, premixed and diffusive combustion.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3275-3285
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• 2021

A Nuclear Power Plant (NPP) is a complex dynamic system-of-systems with highly nonlinear behaviors. In order to control the plant operation under both normal and abnormal conditions, the different systems in NPPs (e.g., the reactor core components, primary and secondary coolant systems) are usually monitored continuously, resulting in very large amounts of data. This situation makes it possible to integrate relevant qualitative and quantitative knowledge with artificial intelligence techniques to provide faster and more accurate behavior predictions, leading to more rapid decisions, based on actual NPP operation data. Data-driven models (DDM) rely on artificial intelligence to learn autonomously based on patterns in data, and they represent alternatives to physics-based models that typically require significant computational resources and might not fully represent the actual operation conditions of an NPP. In this study, a feed-forward backpropagation artificial neural network (ANN) model was trained to simulate the interaction between the reactor core and the primary and secondary coolant systems in a pressurized water reactor. The transients used for model training included perturbations in reactivity, steam valve coefficient, reactor core inlet temperature, and steam generator inlet temperature. Uncertainties of the plant physical parameters and operating conditions were also incorporated in these transients. Eight training functions were adopted during the training stage to develop the most efficient network. The developed ANN model predictions were subsequently tested successfully considering different new transients. Overall, through prompt prediction of NPP behavior under different transients, the study aims at demonstrating the potential of artificial intelligence to empower rapid emergency response planning and risk mitigation strategies.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1540-1553
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• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.