• 한국분무공학회지
• /
• 제22권1호
• /
• pp.22-28
• /
• 2017

In this study, the effects of intake valve closing timing by using Cam-in-Cam system on combustion and emission characteristics for diesel engine were investigated under GT-POWER simulation environment. As a result, it was found that volumetric efficiency and effective compression ratio were decreased as the intake valve closing(IVC) timing is retarded due to its backflow effect. Also, we found that in-cylinder pressure, heat release rate and NOx emission were decreased as IVC timing was retarded. These show that the LIVC(late intake valve closing) can be effective to control AFR and mixing rate in diffusion combustion of diesel engine.

• 한국자동차공학회논문집
• /
• 제5권3호
• /
• pp.137-146
• /
• 1997

Spray characteristics of high pressure injectors for diesel engines have been experimentally studied with special emphasis on the effect of swirl. A constant volume chamber was rotated in order to generate a continuous swirl having the flow field of a solid body rotation, resulting in the linear dependance of the swirl number on the rotating speed of the chamber. Emulsified fuel is injected into the chamber and the developing process of fuel sprays is visualized. The fuel spray developing process in D.I. diesel engine was investigated by this liquid injection technique. The effect of swirl on the spray tip penetration is quantified through modelling. Results show that the spray tip penetration is qualitatively different for low and high pressure injections. For high pressure injection case, a good agreement is achieved between the experimental results and the modeling accounting the effect of swirl. For low pressure injection, a reasonable agreement is obtained. It is found that excessive swirl may cause adverse effect on spray dispersion during the initial combustion period since the spray can not be impinged on chamber wall.

• 한국자동차공학회논문집
• /
• 제14권4호
• /
• pp.39-48
• /
• 2006

In this research, in order to study the spray, combustion, and emission characteristics of the common rail DME engine, the target engine was disassembled, and 3D CAD file was constructed using a 3D measurement machine and a rapid prototyping machine. Using the obtained 3D geometry, fine moving meshes are generated, and three dimensional non-steady turbulence flow field and combustion phenomenon including spray were numerically analyzed. As a result, IMEP of DME and diesel in medium and high speed revolution showed similar performance. As the DME fuel start to burn in spray area, the vaporized fuel rapidly spreads squish area in low speed revolution. In the case of DME engine, CO and NOx are relatively consistent with experiment results. It was found that the break-up, evaporation, collision model of DME fuel need to be properly adjusted through matching the characteristics of fuel and injector for further improvement.

• 한국분무공학회지
• /
• 제1권2호
• /
• pp.16-23
• /
• 1996

In case of a high-speed D.I. diesel engine. the injected fuel spray is unavoidable that the impinging on the wall of piston cavity and in this case the geometry of piston cavity has a great influence on the atomization structure and air flow fields. In the field of combustion and in many other spray applications, there are clear evidence of correlation between spray structure and emission of pollutants. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, a single spray was impinged on each cavity wall at indicated angle in a quiescent atmosphere at room temperature and pressure, as being the simplest case, and 3 types of piston cavity such as Dish, Toroidal and Re-entrant type was tested for analyzing the influence of cavity geometry. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation $\sigma(t)$ and variation factor (v.f.) was measured with the lapse of time.

• 한국전산유체공학회지
• /
• 제5권1호
• /
• pp.8-13
• /
• 2000

In this study, the spray models incorporated into the GTT code were tested for sprays injected in quiescent swirling gases and for the sprays impinging on a flat wall, and the validity of the models has been confirmed by comparing the calculated results with the experimental data. Using this code, the gas flow, spray behavior and fuel vapor distributions in the combustion chamber of a D.I engine have been numerically analyzed with respect to the constant injection pressure and the injection pressure varying with injection time.

• Journal of Advanced Marine Engineering and Technology
• /
• 제16권1호
• /
• pp.35-46
• /
• 1992

In this study, we calculated gas flow fields and distribution of fuel droplet and mass fraction using the CONCHAS-SPRAY code which modified to execute in IBM PC and changed three important factors, injection rate pattern (BASIC, I, II, III), different bowl shape and spray type. Especially vortices which be influenced by fuel-air mixing process, evaporation and flame propagation are generated more strongly in the bowl-piston type combustion chamber than in the flat-piston type. As the spray type changes, it is found that conical type produced large and strong vortices and fuel droplets are effictively diffused into the entire combustion chamber. As the injection rate pattern changes I, II, III based on BASIC type, we confirmed that End-of-Injection Effect strongly influence on droplets life time.

• 한국분무공학회지
• /
• 제15권4호
• /
• pp.195-201
• /
• 2010

Due to its carbon-neutral nature, biogas generated from anaerobic digestion or fermentation of biodegradable wastes is one of the important renewable energy sources to reduce global warming. It is mainly composed of methane and various inert gases such as $CO_2$ and $N_2$, and the actual composition of biogas significantly varies depending on the origin of anaerobic digestion process. Therefore, in order to effectively utilize this fuel as an energy source for electricity, it is important to develop power generation engines which can successfully apply biogas with significant composition variations. In this study, efforts have been made to develop a diesel-biogas duel fuel engine as a way to achieve such a stable power generation. The effects of diesel fuel injection quantity and pressure on stable combustion and engine performance were investigated, and an impact of diesel fuel atomization was discussed. The engine test results show that there exists a 2 stage combustion which consists of diesel pilot fuel burning and premixed biogas/air mixture burning in dual fuel engine operation and optimum diesel injection parameters were suggested for biogases with various compositions and heating values.

• 한국자동차공학회논문집
• /
• 제8권1호
• /
• pp.40-47
• /
• 2000

A model for the prediction of combustion and exhaust emissions of DI diesel engine has been formulated and developed. This model is a quasi-dimensional phenomenological one and is based on multi-zone combustion modelling concept. This model is developed based on the concept of Hiroyasu's multizone combustion models. It takes nozzle injection (spray) parameters, induction swirl into consideration and the models of zone velocity, air entrainment, fuel droplet evaporation and mixture combustion are upgraded. Various parameters, such as cylinder pressure, heat release rate, Nox and soot emission, and these parameters in the zone are simulated. The results are compared with the experimental ones, too.

• 한국자동차공학회논문집
• /
• 제4권3호
• /
• pp.211-219
• /
• 1996

In a small high-speed D. I. diesel engine, the injected fuel spray into the atmosphere of the high temperature is burnt by go through the process of break up, atomization, evaporation and process of ignition. These process are important to decide the emission control and the rate of fuel consumption and out put of power. Especially, in the case of injected fuel spray impinging on the wall of piston cavity, the geometry of piston cavity gives great influence the ignitability of injected fuel and the flame structure. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, the spray was impinged on the wall of 3 types of piston cavity such as Dish, Toroidal, Re-entrant type, in order to analyze the combustion process of impinging spray precisely and systematically. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation σ(t) and variation factor(vf) was measured with the lapse of time.

• 대한기계학회논문집
• /
• 제12권3호
• /
• pp.534-540
• /
• 1988

본 연구에서는 디이젤분무 주위기체의 유동특성중에서 유동속도에 관하여 보 고 하였다. 본모에서는 분무기간중 분사압력의 시간경과특성이 상이한 두 종류의 분 사계를 사용하여 생성된 분무와 주위 기체와의 유동방향의 시간경과 및 유입시기, 정 상유입속도 도달시간등을 분무의 축방향과 반경방향에 대하여 상세한 측정결과를 얻었 기에 보고한다.