This study presents a systematic causal analysis of the fuel consumption rate reduction phenomenon observed in mortar-carrier tracked vehicles during driving tests. The investigation focused on identifying the root causes and developing effective improvement measures. Through comprehensive inspections and tests of the chassis and power pack components, along with data analysis, the study identified the damage of the engine flywheel housing gasket and the clogging of the transmission exhaust pump strainer as the main causes of the reduced fuel consumption rate. The causal relationship between the two phenomena was empirically proven using material composition analysis and statistical techniques, enhancing the reliability and validity of the diagnosis. Based on the root cause analysis results, improvements were implemented, including the replacement of the engine gasket and the cleaning of the transmission exhaust pump strainer. The effectiveness of the improvements was quantitatively verified, confirming a significant enhancement in fuel consumption rate and cruising range. By employing a systematic and scientific analysis methodology, this study provides a foundation for improving the reliability and maintenance efficiency of similar weapon systems and power transmission systems in general.

To fabricate intermetallic nanoparticles with high oxygen reduction reaction activity, a high-temperature heat treatment of 700 to 1,000 °C is required. This heat treatment provides energy sufficient to induce an atomic rearrangement inside the alloy nanoparticles, increasing the mobility of particles, making them structurally unstable and causing a sintering phenomenon where they agglomerate together naturally. These problems cannot be avoided using a typical heat treatment process that only controls the gas atmosphere and temperature. In this study, as a strategy to overcome the limitations of the existing heat treatment process for the fabrication of intermetallic nanoparticles, we propose an interesting approach, to design a catalyst material structure for heat treatment rather than the process itself. In particular, we introduce a technology that first creates an intermetallic compound structure through a primary high-temperature heat treatment using random alloy particles coated with a carbon shell, and then establishes catalytic active sites by etching the carbon shell using a secondary heat treatment process. By using a carbon shell as a template, nanoparticles with an intermetallic structure can be kept very small while effectively controlling the catalytically active area, thereby creating an optimal alloy catalyst structure for fuel cells.

Currently, the most promising fuel candidate for use in sodium fast reactors (SFRs) is metallic fuel, which is produced by a modified casting method in which the metallic fuel material is sequentially melted in an inert atmosphere to prevent volatilization, followed by melting in a graphite crucible, and then injection casting in a quartz (SiO2) mold to produce metallic fuel slugs. In previous studies, U-Zr metallic fuel slugs have been cast using Y2O3 reaction prevent coatings. However, U-Zr alloy-based metallic fuel slugs containing highly reactive rare earth (RE) elements are highly reactive with Y2O3-coated quartz (SiO2) molds and form a significant thickness of surface reaction layer on the surface of the metallic fuel slug. Cast parts that have reacted with nuclear fuel materials become radioactive waste. To decrease amount of radioactive waste, advanced reaction prevent material was developed. Each RE (Nd, Ce, Ln, Pr) element was placed on the reaction prevent material and thermal cycling experiments were carried out. In casting experiments with U-10wt% Zr, it was reported that Y2O3 layer has a high reaction prevent performance. Therefore, the reaction layer properties for RE elements with higher reactivity than uranium elements were evaluated. To investigate the reaction layer between RE and NdYO3, the reaction composition and phase properties as a function of RE content and location were investigated using SEM, EDS, and XRD. The results showed that NdYO3 ceramics had better antireaction performance than Y2O3.

In pyroprocessing, the residual salts (LiCl containing Li and Li2O) in the metallic fuel produced by the oxide reduction (OR) process are removed by salt distillation and fed into electrorefining. This study undertook an investigation into the potential viability of employing a separate LiCl salt rinsing process as an innovative alternative to conventional salt distillation techniques. The primary objective of this novel approach was to mitigate the presence of Li and Li2O within the residual OR salt of metallic fuel, subsequently facilitating its suitability for electrorefining processes. The process of rinsing the metallic fuel involved immersing it in a LiCl salt environment at a temperature of 650°C. During this immersion process, the residual OR salt contained within the fuel underwent dissolution, thereby reducing the concentrations of Li2O and Li generated during the OR process. Furthermore, the Li and Li2O dissolved within the LiCl salt were effectively consumed through chemical reactions with ZrO2 particles present within the salt. Importantly, even after the metallic fuel had been subjected to rinsing in a conventional LiCl salt solution, the concentration of Li and Li2O within the salt remained consistent with its initial levels, due to the utilization of ZrO2. Moreover, it was observed that the Li- Li2O content within the metallic fuel was significantly diluted as a result of the rinsing process.

The stabilization technology for the damaged spent fuel is being developed to process the damaged fuel into sound pellet suitable for dry re-fabrication. It requires several treatments including oxidative decladding followed by reduction treatment for oxidized powder closely related to the quality of oxidized powders for pellet fabrication. For the development of operating condition for the reduction treatment, in this study, we evaluated the effect of air-cylinder based vertical shaking previously applied to oxidative decladding on powder reduction. For U3O8 of 50-100 g, the reduction test were applied with and without vertical shaking at 700°C under reduction atmosphere (Ar + 4%H2) and the concentration of hydrogen in effluent was measured to evaluate the reduction reaction. It was found that the vertical shaking system has allowed the reaction time of 50 g and 100 g U3O8 reduced by 33% compared to the test in static mode. Based on XRD analysis, the better crystallinity of the products was also achieved.

This paper is one of basic studies for development of fuel rail to secure strength of GDI system. The fuel rail supports high pressure of 200~250bar and stores fuel while reducing pulsation during injection. Therefore, the structural characteristics of the conventional fuel rail was investigated with respect to stress and displacement. Then, the study focused on reducing stress concentration on fuel rail design to enhance the strength of each components. It was found that the maximum stress was not affected to the dimensions of taper lengths and angles of holes for fuel pipe. Also, it was found that the shape of holes for fuel pipe was key factor to reduce maximum stress, and the bridge between injector and mounting holder was effective structure to reduce the stress of injectors and displacement of the fuel rail system.

The fuel used in this study, DMM is an oxygen additive containing 42.5% oxygen by weight and dissolved in diesel fuel, also known as methyl alcohol or Dimethoxymethane (CH3-O-CH2-O-CH3). DMM, which is a colorless liquid, shows chemical characteristics of gas-liquid and is also used as a diesel fuel component. In this study, five mixtures were added to the common diesel fuel at DMM addition rates of 2.5, 5, 7.5, 10 and 12.5% by volume. A single cylinder, four strokes, DI diesel engine was used as the test engine. Experimental data were also collected at 24 engine speed-load conditions operating in steady state. The purpose of this experiment was to study the effect of the addition ratio of oxidized fuel mixed in diesel fuel on engine power and exhaust performance. When compared with the common diesel fuel, the exhaust of Smoke was substantially reduced in all DMM mixing ratios. These results indicate that DMM can be an effective blend of diesel fuel and is an environmentally friendly alternative fuel. This study also shows that smoke and NOx emissions can be reduced at the same time through the application of oxygen fuel and EGR.

In anion exchange membrane fuel cells, Pd nanoparticles are extensively studied as promising non-Pt catalysts due to their electronic structure similar to Pt. In this study, to fabricate Pd nanoparticles well dispersed on carbon support materials, we propose a synthetic strategy using mixed organic ligands with different chemical structures and functions. Simultaneously to control the Pd particle size and dispersion, a ligand mixture composed of oleylamine(OA) and trioctylphosphine(TOP) is utilized during thermal decomposition of Pd precursors. In the ligand mixture, OA serves mainly as a reducing agent rather than a stabilizer since TOP, which has a bulky structure, more strongly interacts with the Pd metal surface as a stabilizer compared to OA. The specific roles of OA and TOP in the Pd nanoparticle synthesis are studied according to the mixture composition, and the oxygen reduction reaction(ORR) activity and durability of highly-dispersed Pd nanocatalysts with different particles sizes are investigated. The results of this study confirm that the Pd nanocatalyst with large particles has high durability compared to the nanocatalyst with small Pd nanoparticles during the accelerated degradation tests although they initially indicated similar ORR performance.

The several experiments of Diesel vehicles using EFT were completed. The experiments were performed on chassis dynamometer and road driving test using test mode such as FTP-75 and LA-4. The experiments were employed to measure the effect eco-friendly EFT additives on exhaust emissions and fuel consumption efficiency. In this experiment, the following results are obtained by analyzing the data relativity between exhaust emissions and EFT additives. The value of exhaust emissions such as NOX, SOX, CO2 and PM were improved as Diesel mixed EFT additives at th ratio of 200:1. The improvement of resulting data value was best PM, NOX, SOX, CO₂and fuel consumption rate in the order named.

The two experiments of gasoline vehicle using eco-friendly treatment(Ecoburn) were completed. The experiments was done on traveling using the performance testing mode for chassis dynamometer and road driving test. The experiments were employed to measure exhaust emissions and fuel consumption. In this experiment, the correlation between CO₂and fuel consumption were found in gasoline vehicle. The following results are obtained by analyzing the data relativity between exhaust emissions and additives. 1) If the value of exhaust emissions such as CO, HC, NOX, CO₂were improved as gasoline mixed additives at th ratio of 300:1. The value of fuel consumption were worse compare to those of exhaust emission. The improvement of resulting data value was best CO, HC, NOX and fuel consumption in the order named. 2) The value of CO₂ were to be nearly proportional to the fuel consumption value.

Fuel pump of a vehicle is a device to supply the fuel from fuel tank to engine. This study analyzed the pulsatility on the shape of fuel supply pipe using a CFD(Computational Fluid Dynamics). Numerical analysis was performed to use 3-dimensional incompressible k-ε turbulent model with measured pressure values at an exit by an experiment. Simulation models used commercial and improved model. In this study, the characteristics of the pulsatility reduced in improved model compared to those in commercial model. The pressure loss, which occurs at the flexure, was effective to pulsatile reduction. Commercial and improved model differed by numbers of flexure. The number of flexure between inlet and outlet decreased the difference of velocity and pressure. Therefore, the design of fuel supply pipe should be considered numbers and shape of flexure.

This paper is on developing the advanced method in diagnosis electronic control of gasoline and LPG engine. The experimental methods using oscilloscope were employed to measure waveform of hot wire, hot film, oxygen, ignition coil and injector. Through these analysis, emission reduction and fuel economy improvement were expected by depict vehicles. The experiment was carried out during no-load condition. A summary of the important results are as follows. 1. The factors affecting the secondary ignition waveform from the primary ignition waveform were reverse surge voltage and induced voltage . Actually shape of primary ignition waveform was normal, but a secondary ignition waveform was measured badly. 2. The area of the voltage-time diagram of secondary ignition waveform means the value of the effective discharge of energy. This value is negative, the fuel economy could be predicted badly and is positive, good value of fuel economy could be predicted. 3. Inspection and maintenance of DLI ignition vehicles compared to DIS ignition vehicles were essential. The secondary ignition waveform of the C type vehicle were worst compare to those of the different type vehicles. The injection duration of injector was largest C, D types in the order named, was shortest E, F type. As a result, E, F type are most effective among Gasoline vehicles.

상용원자로에서 발생하는 산화물 사용후핵연료의 부피감용과 재활용을 위하여 산화물을 금속으로 환원시 키는 공정에 대한 연구가 수행되어 왔다. 다양한 환원법 중에서, 한국원자력연구원은 LiCl-Li2O 용융염을 반 응매질로 사용하는 전해환원공정을 현재 개발 중이다. 파이로 공정의 전단부에 해당하는 전해환원 공정은 PWR 산화물 연료 주기를 소듐냉각 고속로의 금속연료 주기에 연결시켜 준다. 이 논문은 금속전환 공정을 개 발/개선하고, 용량 증대를 수행한 한국원자력연구원의 노력을 요약한다.

경막결정화를 이용한 산화물 사용후연료의 전해환원 공정에서 발생하는 LiCl 염폐기물 내 포함되어 있는 Cs 및 Sr을 분리(농축)에 대한 실험을 수행하였다. 결정화 공정에서 Cs 및 Sr과 같은 불순물들은 불순물들의 용융염 상 및 결정상에 대한 용해도이 차리로 분리되어 최종적으로 작은 양의 LiCl 용융염내에 농축된다. 본 연구에서는 LiCl-CsCl-SrCl2 계에대한 고체-액체 상평형도를 통해 결정화를 통한 분리가능성을 파악하였으며 열전달방정식 의 계산을 통해 경막결정화 운전중 LiCl 용융염상의 온도분포를 예측할 수 있었다. 경막결정화 공정에서 결정성 장 속도는 분리효율에 큰 영향을 미쳤으며 90%의 LiCl 재생율을 가정할 경우 20-25 l/min의 냉각속도 그리고 0.2 g/min·cm2보다 작은 결정성장 속도조건에서 각각의 Cs 및 Sr에 대하여 90% 정도의 분리효율을 나타내었다.

The electrocatalytic characteristics of oxygen reduction reaction of the PtxM(1-x) (M = Co, Cu, Ni) supported on multi-walled carbon nanotubes (MWNTs) have been evaluated in a Polymer Electrolyte Membrane Fuel Cell (PEMFC). The PtxM(1-x)/MWNTs catalysts with a Pt : M atomic ratio of about 3 : 1 were synthesized and applied to the cathode of PEMFC. The crystalline structure and morphology images of the PtxM(1-x) particles were characterized by X-ray diffraction and transmission electron microscopy, respectively. The results showed that the crystalline structure of the Pt alloy particles in Pt/MWNTs and PtxM(1-x)/MWNTs catalysts are seen as FCC, and synthesized PtxM(1-x) crystals have lattice parameters smaller than the pure Pt crystal. According to the electrochemical surface area (ESA) calculated with cyclic voltammetry analysis, Pt0.77Co0.23/MWNTs catalyst has higher ESA than the other catalysts. The evaluation of a unit cell test using Pt/MWNTs or PtxM(1-x)/MWNTs as the cathode catalysts demonstrated higher cell performance than did a commercial Pt/C catalyst. Among the MWNTs-supported Pt and PtxM(1-x) (M = Co, Cu, Ni) catalysts, the Pt0.77Co0.23/MWNTs shows the highest performance with the cathode catalyst of PEMFC because they had the largest ESA.