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An oil layer fuel absorption/desorption modeling was developed. Multi- component fuel model has showed more reasonable condition than single component model. Henry's constant which is related to solubility is the most important variable in the oil layer absorption/desorption mechanism. The oil segments close to the top of the cylinder liner have more significant contribution to the fuel absorption and desorption process than other oil segments. At the warmed-up condition, the effect of the engine speed on the percent fuel absorbed/desorbed is minimal. But at low oil film temperature, percent of fuel absorbed/desorbed is decreased with increasing the engine speed because of low value of molecular diffusion coefficient of fuel. The amount of fuel trapped in the piston crevice is from 2 to 2.3 times larger than that of fuel in the oil film. However, fuel from oil film slowly desorbs into the combustion chamber compared with fuel from the piston crevices when the engine is cold
A dynamic model of proton exchange membrane fuel cell(PEMFC) system is designed to understand the performance of the PEMFC in residential power generator(RPG) over various balance of plant(BOP) options. In particular, since the performance of PEMFC system should be optimized for given operating ranges, it is necessary to design suitable BDP components which can support the operating ranges. The objective of this study is to develop a dynamic system model for the study of PEMFC performance over various BOP options. Therefore, a dynamic model is composed of a PEMFC stack model, a water management system model, a thermal management system model and a fuel/air supply model and the model is integrated under SIMULINK(R)environment. Basic simulation results will be presented.
An experimental study on the design of a catalytic combustor for high temperature MCFC system has been performed. The roles of the catalytic combustor are to completely burn anode off-gas and to supply sufficient CO₂ to cathode channels. In order to avoid hot spots or fuel slippage, flow uniformity at the catalyst inlet was achieved by installing two crossing perforated plates between the catalyst and the mixing chamber with minimal pressure drop. Effects of inlet temperature and fuel composition on catalytic combustion have been tested in the present study. A Pd/Ce/Ni-Al₂O₃ catalyst was used for complete combustion of the off-gas at GHSV = 36,000.
An object of this study is to understand the correlation of injection characteristics and injector dimensions according to biodiesel mixture. The Injection characteristics of different types of common-rail injectors are the number of nozzle holes (5~8), jet cone angle (146˚~153˚), hydraulic flow rate (830~900 ml/min) injection quantity and response time. Prior to characteristic experiment, the reference injector has been selected in 6 candidates injectors under the investigation of injected quantity according to the biodiesel mixture so that injector type can be determined. The injector is used for the characteristic experiment which varied the various operating conditions including pressure 23 MPa, 80 MPa, 160MPa, changing in injection duration 0.16 ms~1.2 ms and even mixture ratio. The result shows that the nozzle hole number and cone angle influence the injection quantity much more than nozzle hole diameter at low injection pressure and the nozzle hole diameter at high injection pressure, post injection duration.
Study for utilization of landfill gas was proposed. Portion for existing landfill gas utilization for energy source remains under 10% that is too far considering potential value of the gas. Based on the domestic landfill gas condition, reforming process by rotating arc plasma was investigated. Conversion rate of CH₄ and CO₂ determined by the amount of energy input. The main products were H₂ and CO, and representative by-product was the C₂H₂. Ratio of H₂/CO of synthesis gas range was from 1.671 to 1.699. About 2 ㎾ of energy supply is expected to result in conversion of CH₄ above 90% where specific energy density is 17.6 kJ/LCH4.
A vortex tube is a simple device without moving parts or chemical reactions. The vortex tube has many advantages in terms of simplicity, durability, low cost, smallness or lightness, adjustability of temperature and environmentally friendly. The present study is to predict the temperature and energy separation of the experimental separation values and elucidate the fundamental principle of the vortex tube. To this end, 2D axisymmetric swirl flow simulations were carried out. As a result, on the whole, temperature separation and energy separation were well predicted compared to the previous numerical analysis results. A reverse flow is observed at the low temperature outlet, which leads to underestimation of the temperature and energy separation at the low temperature outlet.
In a multi-effect solar distiller, a feeding rate of the seawater to each effect number should be decreased as the effect number is increased. Typically, this decreasing rate of the fed seawater in the each effect was not constant. However, the different decreasing rates between the effects are unreasonable since the decreasing rate of thermal energy in each effect is theoretically constant. In this paper, computational analysis is carried out to elucidate this abnormal phenomena. The analysis results showed that the amount of distillates was almost same at both the conditions of the different decreasing rate and constant one. The analysis also includes the optimum flow rate of the seawater feed with various amount of energy inputs which get from heat exchanging process with exhaust gas of high temperature. The results showed that the optimum feeding rate of the first effect as the energy input increases was linearly increased or saturated, and that depended on the variables such as gas velocity, gas temperature and the operating time which related with the heat exchanging means with the exhaust gas.