• Journal of ILASS-Korea
• /
• v.28 no.4
• /
• pp.169-175
• /
• 2023

Multi-injection scheme is being applied to GDI combustion to reduce PM and PN emission to meet the EU7 regulation. However, very short injection duration encounters the ballistic injection region, which injection quantity does not increase linearly with injection duration when applying multi-injection. In this study, numerical studies were conducted to reveal the cause of ballistic injection and the effect of design parameters on ballistic region using 1-D simulation, AMESim. Injection rate and injection quantity were compared with experiment to validate the established model, which showed the accuracy with 10% error. The model revealed that the tendency of ballistic region coincides with the needle motion behavior, which means that parameters at the upper part of needle such as electro-magnetic force, needle spring force and needle friction force have dominant effect on ballistic injection. To figure out the effect of electro-magnetic and needle friction force on ballistic, those parameters were varied to plus and minus 10% with model. The result showed that those parameters clearly changed the ballistic region characteristics, however, the impact became insignificant for outside of ballistic region, which means that the ballistic injection is mainly influenced by initial motion of injector needle.

• Membrane Journal
• /
• v.25 no.1
• /
• pp.75-83
• /
• 2015

In this study, chlorophylls were been extracted from common local plants, deposited on polypropylene (PP) substrate using various approaches, and the oxygen generation effect of the chlorophylls were investigated. The loading of chlorophylls on the substrates was achieved by dipping and spraying methods, where the spraying coating showed overall better results regarding oxygen generation from the combustion experiments in the closed vessel or in the isolated vacuum oven cell than those of dip coating. In addition, a composite substrate was prepared by nylon6/6 nanofiber on the PP substrate, and it exhibited an increase in the activation of chlorophylls. In the case of samples containing titanium dioxide ($TiO_2$), the reaching time of oxygen concentration from 16% to 21% and the combustion test using a candle for a sample with 50% chlorophylls showed similar results to those of a sample without $TiO_2$. As such, combining a spray coating and $TiO_2$ incorporation into gas separation membrane systems are expected to be useful to understand the fundamentals of material properties for their applications as oxygen generation membranes and air filtration systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.10
• /
• pp.60-65
• /
• 2003

An experimental study was performed to understand ignition characteristics of gas turbine combustor with rotating fuel injection system. Liquid fuel applied to the inner surface of rotating fuel nozzle which was driven by high speed electrical motor is flung away by centrifugal forces. The real scale combustor and test rig was manufactured and tested under atmospheric condition in KARl combustion test facility. From the test results, this combustor ignition characteristics are highly dependent upon fuel nozzle rotating speed. Futhermore, combustor exit gas temperature was rapidly changed by increasing or decreasing the fuel nozzle rotating speed.

• Journal of ILASS-Korea
• /
• v.25 no.1
• /
• pp.21-26
• /
• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• Journal of ILASS-Korea
• /
• v.25 no.1
• /
• pp.27-33
• /
• 2020

NOx, PN and CO emissions from diesel trucks make up a significant portion of domestic air pollutant emissions. Therefore, test vehicles with various emission standards and driving modes were selected to evaluate the emission characteristics of regulated pollutants (NOx, PN, CO) in medium-duty trucks. As a result of test, all test vehicles were satisfied with Euro 5 or 6 regulation. NOx emissions of Euro 6 vehicles with after-treatment of LNT + DPF were lower than those of Euro 5 vehicles with DPF. In WLTC mode, all vehicles have high NOx emissions at section of extra high speeds, which are determined by increased fuel consumption and high combustion temperatures. CO and PN emissions from all vehicles were found to be low at section of low speeds. Also, The NO₂/NOx ratio was analyzed at 7-23% in each mode, and the NO₂/NOx ratio increased as the average vehicle speed increased. In NIER 9 mode, the CO, HC, and PN emissions were higher under cold conditions of engine than hot conditions of engine. In addition, vehicles with after-treatment system of LNT have similar NOx emissions level in this study.

• Journal of ILASS-Korea
• /
• v.25 no.1
• /
• pp.8-14
• /
• 2020

Recently, 1-D model-based engine development using virtual engine system is getting more attention than experimental-based engine development due to the advantages in time and cost. Injection rate profile is the one of the main parameters that determine the start and end of combustion. Therefore, it is essential to set up a sophisticated model to accurately predict the injection rate as starting point of virtual engine system. In this research, procedure of 1-D model setup based on AMESim is introduced to predict the dynamic behavior and injection rate of diesel injector. As a first step, detailed 3D cross-sectional drawing of the injector was achieved, which can be done with help of precision measurement system. Then an approximate AMESim model was provided based on the 3D drawing, which is composed of three part such as solenoid part, control chamber part and needle and nozzle orifice part. However, validation results in terms of total injection quantity showed some errors over the acceptable level. Therefore, experimental work including needle movement visualization, solenoid part analysis and flow characteristics of injector part was performed together to provide more accuracy of 1-D model. Finally, 1-D model with the accuracy of less than 10% of error compared with experimental result in terms of injection quantity and injection rate shape under normal temperature and single injection condition was established. Further work considering fuel temperature and multiple injection will be performed.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.3
• /
• pp.1-7
• /
• 2003

In this research, it is intended to measure shape of the nozzle throat of the KL-3 engine, which is the main engine of the KSR-III rocket. For the purpose, an image-based method was invented to replace the 3D pointer, which is actually inaccessible to such large scale engines. As a result, our equipment showed satisfactory Performances. Analysing the results of experiments, we find that the pattern of ablation is determined by the spray pattern and that the process of thermal ablation phenomena can be categorized in three regimes - the first regime that the shape of nozzle throat is maintained and ablation is negligible, the second regime that saw-tooth form is developed and ablation is accelerated, and the third regime that the saw-tooth form is already established and the growth of ablation rate is reduced Also, we find that the ratio of area increase after 60 seconds combustion is +5.82% and conclude that the ratio is acceptable and satisfactory.

• Journal of the Korean institute of surface engineering
• /
• v.48 no.6
• /
• pp.260-268
• /
• 2015

The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.19 no.1
• /
• pp.93-101
• /
• 2011

The modeling of SDR was carried out for the application of the solid waste incineration system. To find optimum operating condition for removal of acidic gases, computation fluid dynamic(CFD) model was used. In this study, the temperature profile of SDR(spray dry reactor) and the gas velocity profile for different models were investigated. In this model, the diameter of SDR was 3 meter and the height of SDR was 9 meter. The amount of inlet combustion gas of SDR was $6,125Nm^3/hr$ and the inlet temperature of SDR was 493 K. The amount of lime injection of SDR was 151 kg/hr. When the inlet shape of SDR was changed, the temperatur of SDR was changed and the gas velocity of SDR was 0.48 m/sec to 1.17m/sec and the outlet gas velocity of SDR was 6.9 m/sec to 7.42m/sec As a result of modeling, the average velocities in SDR and outlet were 0.489 m/sec and 7.424 m/sec, respectively, in which the temperature of outlet in SDR was 448 K.

• Journal of ILASS-Korea
• /
• v.23 no.4
• /
• pp.175-184
• /
• 2018

Emission characteristics of regulated (NOx, PM, CO, NMHC) and unregulated (VOCs, aldehydes, PAHs) air pollutants were investigated for diesel heavy duty buses equipped with different after-treatment systems (DPF+EGR and SCR) under urban driving cycle. The combustion temperature and the working temperature of SCR catalysts were important to make impact on NOx emissions, whereas PM emissions were low. The alkane groups dominated NMVOCs emissions, making 42.6~59.4% of sum of the NMVOCs emissions. Especially, alkane emissions of DPF+EGR-equipped vehicle included DOC had 14.9~15.5% higher than those of SCR-equipped vehicle due to low efficiency of oxidation catalyst. In the case of individual NMVOCs, n-nonane and propylene emissions highly occupied for DPF+EGR and SCR, respectively. Formaldehyde emissions among aldehydes were the highest and PAHs emissions were hardly detected except naphthalene and phenanthrene. The NMHC speciation has been shown to be the highest of the formaldehyde ranged 20.8~21.5%. The results of this study will be contributed to establish Korean HAPs emission inventory for automobile source.