Earticle

방산기술이 복제되거나 방해기술이 발달되어 그 가치와 효용이 낮아지는 것을 방지하고 부적절한 수출을 방지하기 위한 보호가 필요하여 2015년도에 방위산업기술보호법이 제정되었다. 방산기술이란 방위산업과 관련된 국방과학기술 중에 서 국가안보를 위하여 보호되어야 하는 기술을 의미한다. 그러나 현재 방산기술 보호체계 중에서 보호대상 기술의 식별 및 관리 체계의 기술식별 기준이 법규화 되어 있지 않다. 이에 본 연구에서는 델파이 설문을 통하여 141개 방산기술 중에서 고효율 내연기관 추진 기술과 관련 있는 디젤기관 요소기술 식별기준을 정립하고 방산기술 보호체계 중 보호대상 기술의 식별 및 관리 체계를 개선하였다. 연구결과로 디젤기관 요소기술 식별기준으로 작전 운용성, 내구성, 안전성, 계열화 및 모듈화 등을 정립하였다.

The Defense Technology Security Act was enacted in 2015 to protect the defense industrial technology from being duplicated or interfering technologies being developed, which prevents its value and utility from deterioration and prevents inappropriate export. Defense industrial technology refers to technology that should be protected for national security among the national defense science and technology related to the defense industry. However, technical identification criteria of identification and management system of protection technology are not regulated. Therefore, in this study, through the Delphi survey, diesel engine core technology identification criteria related to the high efficiency internal combustion engine propulsion technology among the 141 defense industrial technologies is established to improve the identification and management system of the technology to be protected among the defense industrial technology protection system. As a result of the study, operational operability, durability, safety, sequencing and modularization were established as diesel engine core technology identification criteria.

Diesel engine has the advantages of strong power, low fuel consumption and good durability, so it has been widely used in transportation, automobile, ship and other fields. However, the nitrogen oxides(NOx) and particulate matter(PM) emitted by diesel engines have become one of the main causes of air pollution. Especially during idling, the engine temperature is low, and there are more residual exhaust gases in the combustion chamber, resulting in the formation of more harmful emissions. In this study, performance of a single cylinder, four-stroke, direct injection (DI) diesel engine fueled with diesel–biodiesel mixtures has been experimentally investigated.

본 연구에서는 가변 압축비 조절기구가 부착된 단기통 4행정 수냉식 디젤 엔진(모델 : Farryman A 30 marine, TQ, UK) 에 바이오디젤 연료(BDF)를 적용하여 엔진의 성능변수와 배기가스 특성을 살펴보았으며 여러 가지 연료와 운전조건에 따른 비연료 소비율(SFC)과 매연 농도도 함께 조사하였다. 사용된 연료는 상업용 디젤유(DF)와 BDF100(BDF 100 %), 그리고 이들의 혼합유인 BDF20(BDF vol. 20 % + DF vol. 80%) 이며, 이 중에서 DF를 비교 기준 연료로 하였다. 실험조건으로는 압축비(CR)가 12:1, 14:1, 16:1 및 18:1 이며, 엔진 속도가 1000, 1500, 2000 및 2500 rpm 이다. 실험 결과, BDF의 SFC는 엔진 속도에 따라 DF에 비하여 1.3 ～ 3.7 % 증가하여 나타났으며, 매연 농도는 DF에 비하여 최대 45.7 % 감소하여 나타난 반면에, NOx 는 최대 38 % 까지 크게 나타났는데 이는 선행 연구결과인 12.0 % 정도를 훨씬 상회한다. 또한, 엔진 출력은 사용한 연료 종류에 따라 큰 차이를 보이지 않는 것으로 나타났다.

An experimental study on engine performance parameters and emission gas characteristics for bio-diesel fuels (BDF's) was performed by using of a specific engine; the type of single-cylinder, four-stroke, water-cooled diesel engine with variable compression ratio adjustment mechanism (the model Farryman A 30 marine, TQ, UK). Specific fuel consumptions (SFC) and soot tendency(smoke %) for various fuel and/or operation conditions were also examined. The BDF's used were prepared BD 20 and BD 100 together with the commercial diesel fuel (DF) for reference. The established conditions for experiment were 12:1, 14:1, 16:1 and 18:1 for compression ratio (CR), and 1000, 1500, 2000 and 2500 rpm for engine speed. It was found that SFC of BDF's is increased 1.3 ～ 3.7 % compared with DF according to the rpm's; for the smoke %, BDF's value is reduced significantly up to max. 45.7 % in comparison to that of DF; and while NOx is increased amazingly up to max. 38 %, which is too much than the previous results of around 12.0 %. Also, it does not seem that the engine's power output remains changed significantly according to the fuels used.

In this study, we investigated the effects of diesel-palm oil biodiesel-ethanol blends on combustion and emission characteristics in a 4-cylinder common rail direct injection (CRDI) diesel engine at low idling operations. The engine speed and engine load was 750 rpm and 40 Nm, while the main and pilot injection timing was respectively fixed at 2 °CA before top dead center (BTDC) and 20 °CA BTDC. The experimental results showed that the cylinder pressure increased with the increasing of palm oil biodiesel ratio from 20% to 100%. In addition, the peak value of cylinder pressure increased by 4.35% compared with pure diesel fuel when 5 vol.% ethanol oil added to diesel oil. Because the palm oil biodiesel and ethanol are the oxygenated fuel, the oxygen content played an important role in improving combustion. Based on the high oxygen content of biodiesel and ethanol, their mixing with diesel fuel effectively reduced PM emissions but increased NOx slightly, while CO and HC had no significant changes.

This study has focused on using fuel injections as variables for measuring performance and reducing exhaust gas in turbo-charger inter-cooler diesel engine. In experiments, we changed nozzle hole diameter, diameter of an injection pipe, and injection timing as variable. The results show that torque, fuel consumption and smoke are reduced as nozzle hole diameter decreases, while NOx increases. When the diameter of injector is reduced, torque, fuel consumption and smoke are deteriorated, but NOx is decreased. In addition, when the time for injection is advanced, torque, fuel consumption and smoke are improved, but the density of NOx is increased .

This study examines how the oxygen content in fuel influences exhaust emissions in an indirect injection diesel engine. Experiments were conducted to evaluate variations in engine performance and emission characteristics when using commercial diesel fuel and oxygenated blended fuels with four different blending ratios. In addition, the influence of exhaust gas recirculation (EGR) on NOx emission behavior was analyzed. Ethylene glycol butyl ether(EGBE), which contains approximately 27% oxygen by mass, was used as an oxygenated additive. As an ether type oxygenated fuel, EGBE has been reported to significantly reduce smoke emissions compared with conventional diesel fuel. This effect is attributed to the additional oxygen supplied during the combustion process, which promotes more complete oxidation particularly under high-load and high-speed operating conditions. The experimental results indicate that the application of an oxygenated blended fuel containing 10 vol-% EGBE, together with a cooled EGR system at an EGR rate of about 10%, enables simultaneous reduction of smoke and NOx emissions.

The potential for biodiesel to replace diesel has been explored as an alternative fuel for naturally aspirated indirect injection diesel engines. Overall biodiesel smoke emissions were significantly reduced compared to diesel fuel, which was approximately 36% lower at 2000 rpm, peak load conditions. And torque, power and brake energy consumption did not show much difference. However, compared to diesel fuel, NOx emissions from biodiesel have increased. To combat this problem, an EGR(exhaust gas recirculation) method has been applied to reduce NOx emissions. It was confirmed that simultaneous reduction of NOx and smoke was confirmed by cooling EGR method(10~15%) and biodiesel(20 vol%).

In this study, the spray characteristics of blending fuel with diesel fuel and high viscosity biodiesel fuel was investigated. The research was performed for the effect on biodiesel fuel blending ratio and injection pressure for the spray behavior. The experimental process of spray injection was analyzed with LDPAlaser diffraction particle analyzer). In addition, spray atomization characteristics were researched with SMD(Sauter mean diameter) and droplet distribution on various injection pressure conditions. Fuel containing high viscosity biodiesel fuel has some different spray behaviors on account of the viscosity and surface tension. Though this experimental result, we found that the increase of injection pressure enables SMD to get smaller, but the increase of blending ratio makes SMD larger.

Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular, the exhaust emissions of diesel engines are recognized as main causes of the air pollution. CRDI (common rail direct injection) diesel engine is widely used for the sake of minimization on exhaust emission. Because biodiesel fuel is a renewable and alternative fuel for diesel engine, its usability is expanded. An commercial CRDI diesel engine used to commercial vehicle was fueled with diesel fuel and 5% biodiesel blended fuel (BDF 5%) with city mode in excess of 300 hours. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. To check the engine parts (valve, injector), the engine was inspected after test. It was concluded that there was no unusual deterioration of the engine, or any unusual changes in engine power and exhaust emissions in spite of operation of 300 hours with BDF 5%.