• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.572-579
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• 2006

Accurate heat release analysis based on the cylinder pressure trace is important for evaluating combustion process of diesel engines. However, traditional single-zone heat release models (SZM) have significant limitations due mainly to their simplified assumptions of uniform charge and homogeneity while neglecting local temperature distribution inside cylinder during combustion process. In this study, a heat release analysis based on single-zone model has been evaluated by comparison with computational simulation result using Fire-code, which is based on multidimensional model (MDM). The limitations of the single-zone assumption have been estimated, To overcome these limitations, an improved model that includes the effects of spatial non-uniformity has been applied. From this improved single-zone heat release model (Improved-SZM), two effective values of specific heat ratios, denoted by ${\gamma}_V$ and ${\gamma}_H$ in this study, have been introduced. These values are formulated as the function of charge temperature changing rate and overall equivalence ratio. Also, it is applied that each equation of ${\gamma}_V$ and ${\gamma}_H$ has respectively different slopes according to several meaningful periods during combustion progress. The heat release analysis results based on improved single-zone model gives a good agreement with FIRE-code results over the whole range of operating conditions of target engine, Hyundai HiMSEN H21/32.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.32-39
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• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, HCCI's operating range is limited by an excessive rate of pressure rise during combustion and the resulting engine knock in high-load. The purpose of this study was to gain a understanding of the effect of only initial temperature and thermal stratification for reducing the pressure-rise rate in HCCI combustion. And we confirmed characteristics of combustion, knocking and emissions. The engine was fueled with Di-Methyl Ether. The computations were conducted using both a single-zone model and a multi-zone model by CHEMKIN and modified SENKIN.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.51-58
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• 2003

A cycle simulation method is developed by coupling a commercial code, Ricardo's WAVE, with the SENKIN code from CHEMKIN packages to predict combustion characteristics of an HCCI engine. By solving detailed chemical kinetics the SENKIN code calculates the combustion products in the combustion chamber during the valve closing period, i.e. from IVC to EVO. Except the combustion chamber during the valve closing period the WAVE code solves thermodynamic status in the whole engine system. The cycle simulation of the complete engine system is made possible by exchanging the numerical solutions between the codes on the coupling positions of the intake port at IVC and of the exhaust port at EVO. This method is validated against the available experimental data from recent literatures. Auto ignition timing and cylinder pressure are well predicted for various engine operating conditions including a very high ECR rate although it shows a trend of sharp increase in cylinder pressure immediate after auto ignition. This trend is overpredicted especially for EGR cases, which may be due to the assumption of single-zone combustion model and the limit of the chemical kinetic model for the prediction of turbulent air-fuel mixing phenomena. A further work would be needed for the implementation of a multi-zone combustion model and the effect of turbulent mixing into the method.

• Journal of Power System Engineering
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• v.2 no.2
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• pp.20-26
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• 1998

Heat release data were obtained by analysis of cylinder diagrams from a test engine, naturally-aspirated small-size four-stroke DI diesel engine. These data were used to decide empirical coefficients of Whitehouse-Way's model, single zone combustion model. Finally, the comparison of calculated with experimental results was performed, and the accuracy of calculated versus experimental data of the model in predicting engine heat release and cylinder pressure was demonstrated.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1063-1071
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• 2004

Accurate heat release analysis of cylinder pressure data is important for evaluating performance in the development of diesel engine However, traditional single zone first law heat release model(SZM) has significant limitations due to the simplified assumption of uniform charge and neglecting local temperature inside cylinder during combustion process. In this study. heat release rate based on single zone heat release model has been evaluated by comparison with computational analysis results using Fire code which is based on multi-dimensional model(MDM). To overcome limitations due to simplicity of single zone assumption. especially the influence of specific heat ratio on gross heat release has been esteemed and newly suggested were the equation $\gamma$= $\gamma$(${T/T}_{max}$) which describes the variations of gases thermodynamic properties with mean temperature and maximum mean temperature inside cylinder Single zone heat release model applied with this equation is shown to give very good results over whole range of operating conditions when compared with computational analysis results based on multi-dimensional model.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.55 no.4
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• pp.411-418
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• 2019

In this study, to investigate the effect of physical and chemical properties of butanol on the engine performance and combustion characteristics, the coefficient of variations of IMEP (indicated mean effective pressure) and fuel conversion efficiency were obtained by measuring the combustion pressure and the fuel consumption quantity according to the engine load and the mixing ratio of diesel oil and butanol. In addition, the combustion pressure was analyzed to obtain the pressure increasing rate and heat release rate, and then the combustion temperature was calculated using a single zone combustion model. The experimental and analysis results of butanol blending oil were compared with the those of diesel oil under the similar operation conditions to determine the performance of the engine and combustion characteristics. As a result, the combustion stabilities of D.O. and butanol blending oil were good in this experimental range, and the indicated fuel conversion efficiency of butanol blending oil was slightly higher at low load but that of D.O. was higher above medium load. The premixed combustion period of D.O. was almost constant regardless of the load. As the load was lower and the butanol blending ratio was higher, the premixed combustion period of butanol blending oil was longer and the premixed combustion period was almost constant at high load regardless of butanol blending ratio. The average heat release rate was higher with increasing loads; especially as butanol blending ratio was increased at high load, the average heat release rate of butanol blending oil was higher than that of D.O. In addition, the calculated maximum. combustion temperature of butanol blending oil was higher than that of D.O. at all loads.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.3
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• pp.19-25
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• 2010

The purpose of this study is to gain a better understanding of the effects of fuel stratification on reducing the pressure-rise rate at high load in HCCI combustion. It was found that fuel stratification offers good potential to achieve a staged combustion event and reduced pressure-rise rates. The engine is fueled with Di-Methyl Ether (DME) which has unique 2-stage heat release. Numerical analysis is conducted with single and multi-zones model and detailed chemical reaction scheme is done by chemkin and senkin. Calculation result shows that proper fuel stratification prolongs combustion duration and reduce pressure rise rate. Besides IMEP, combustion efficiency and indicated thermal efficiency keep constant. However, too wide fuel stratification increases pressure rise rate and CO and NOx emissions in exhaust gas.

• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.197-198
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• 2012

Efficient numerical analysis of combustion induced by premixed swirl multi-burners in a gas turbine combustor is conducted by adopting swirler model. By analyzing the internal recirculation zone, the inner and outer diameters of the swiler are determined to be 28 mm and 76mm to 28mm, respectively. Tangential velocity of 35m/s is determined from swirl and recirculation angles. With swirler model adopted, the predicted temperature of combustion gas agrees well with that from single-burner calculation without the model. But, NOx emission is underestimated by 60 %.

• Journal of ILASS-Korea
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• v.3 no.2
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• pp.42-50
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• 1998

The effect of swirl flows un the fuel spray characteristics were investigated for various swillers in a model combustor. The interaction between the flow field and fuel spray in the main combustion tone made by frontal devices including fuel injection nozzles and swirlers. which were characterized by flow velocities, fuel droplet sizes and their distributions which were measured by APV(Adaptive Phase/Doppler Velocimetry) under atmospheric condition at 320cc/min kerosine fuel flow and 0.04kg/sec air supply. A dual swirler with circumferential two-stage swirl vanes of $40^{\circ}\;and\;45^{\circ}$ vanes in different directions and two single-stage swillers of $40^{\circ}$ vanes with 12 and 16 vanes were tested. It was found that the dual swirler has the largest recirculating zone with highest reverse flow velocity. The strongest swirl flow was found at the boundary of recirculation zone. Small fuel droplets were observed in the main axial stream and inside the recirculation zone when swirling flow field were generated by the frontal devices. These findings could give the tips on the optimal design of frontal devices to realize low emissions in gas turbine combustion.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.3
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• pp.9-18
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• 1995

The substitution of conventional fuel oil by alternative fuels is of immense interest due to liquid oil shortage and requirements of emission control standard. Among the alternative fuels, natural gas may be the most rational fuel, because of its widespread resource and clean est burning. Meanwhile, engine simulation is of great importance in engine development. Hence a zero-dimensional combustion model was developed for dual-fuel system. Natural gas was injected directly into the cylinder and small amount of distillate was used to provide the ignition kernel for natural gas burning. The intake air and exhaust gas flow was modeled by filling and emptying method. Although the single zone approach has an inherent limitation, the model showed promise as a predictive tool for engine performance. Its simulation was also made to see how the engine performance was influenced by the fuel injection timings and amount of each fuel.