• 한국분무공학회지
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• 제27권3호
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• pp.117-125
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• 2022

This study examines whether engine fuel efficiency is improved by optimization of the exhaust valve timing in a state where the intake valve timing has been optimized in a small turbo gasoline engine that has intake cams and exhaust cams with fixed valve opening periods. When the exhaust valve is opened late, the expansion stroke is longer, and the efficiency can be improved. A 2-cylinder turbo gasoline engine with 0.8 liters of displacement and an MPI (Multi Point Injection) fuel system was used. The engine was operated at 1,500 and 3,000 rpm, and the load conditions included a partial load of 50 N·m and a high load of 70 N·m. Data was recorded as the exhaust valve timing was controlled, and this was used to calculate the efficiency of combustion using a heat release, the fuel conversion efficiency, and the pumping loss. Results and the hydrocarbon concentrations in the exhaust gas were compared for each condition. Experiment results confirmed that additional fuel efficiency improvements are possible through exhaust valve timing control at 1,500 rpm and 50 N·m. However, in other operating conditions, fuel efficiency improvements could not be obtained through exhaust valve timing control because cases where the pumping loss and fuel/air mixture slip increased when the exhaust valve timing changed and the fuel efficiency declined.

• Journal of Microbiology and Biotechnology
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• 제23권5호
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• pp.644-651
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• 2013

The fermented manure derivative known as Preparation 500 is traditionally used as a field spray in biodynamic agriculture for maintaining and increasing soil fertility. This work aimed at characterizing the product from a microbiological standpoint and at assaying its bioactive properties. The approach involved molecular taxonomical characterization of the culturable microbial community; ARISA fingerprints of the total bacteria and fungal communities; chemical elemental macronutrient analysis via a combustion analyzer; activity assays for six key enzymes; bioassays for bacterial quorum sensing and chitolipooligosaccharide production; and plant hormone-like activity. The material was found to harbor a bacterial community of $2.38{\times}10^8$ CFU/g dw dominated by Gram-positives with minor instances of Actinobacteria and Gammaproteobacteria. ARISA showed a coherence of bacterial assemblages in different preparation lots of the same year in spite of geographic origin. Enzymatic activities showed elevated values of ${\beta}$-glucosidase, alkaline phosphatase, chitinase, and esterase. The preparation had no quorum sensing-detectable signal, and no rhizobial nod gene-inducing properties, but displayed a strong auxin-like effect on plants. Enzymatic analyses indicated a bioactive potential in the fertility and nutrient cycling contexts. The IAA activity and microbial degradation products qualify for a possible activity as soil biostimulants. Quantitative details and possible modes of action are discussed.

• 한국화재소방학회논문지
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• 제26권2호
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• pp.75-83
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• 2012

반밀폐된 구획에서 발열량 변화에 따른 환기부족화재의 비정상 열 및 화학적특성에 관한 실험적 연구가 수행되었다. 이를 위해 실규모 ISO 9705 표준화재실의 출입구 폭이 0.1 m로 축소되었으며, 구획 중앙에 설치된 분사노즐을 통해 헵탄 연료의 유량은 선형적으로 증가되었다. 구획 내부의 온도, 열유속, 화학종농도 그리고 발열량의 연속적 측정이 이루어졌으며, 비정상 열 및 화학적특성을 표현하기 위하여 총괄 당량비의 개념이 적용되었다. 주요 결과로서, 총괄 연소효율과 구획 내부의 국부 연소효율은 시간에 따라 매우 다른 결과를 보이며, 이론과 측정된 발열량을 통한 총괄 당량비 역시 큰 차이를 보이게 된다. 온도, 열유속 및 화학종 농도의 시간에 따른 변화는 총괄 당량비 개념를 통해 표현될 수 있었다. 구획 내부에서 CO의 농도는 총괄 당량비 2.0~3.0의 범위에서 최대값을 보이며, 보다 과농한 조건에서 점차적으로 감소되는 현상이 발견되었다. 추가로 본 실험을 통해 얻어진 반밀폐된 구획화재의 비정상 열 및 화학적 거동은 향후 현실적인 화재 모델링을 위한 검증 데이터로 활용될 수 있을 것으로 기대된다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.91-99
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• 2014

The common-rail injectors are the most critical component of the CRDI diesel engines that dominantly affect engine performances through high pressure injection with exact control. Thus, from now on the advanced combustion technologies for common-rail diesel injection engine require high performance fuel injectors. Accordingly, the previous studies on the numerical and experimental analysis of the diesel injector have focused on a optimum geometry to induce proper injection rate. In this study, computational predictions of performance of the diesel injector have been performed to evaluate internal flow characteristics for various needle lift and the spray pattern at the nozzle exit. To our knowledge, three-dimensional computational fluid dynamics (CFD) model of the internal flow passage of an entire injector duct including injection and return routes has never been studied. In this study, major design parameters concerning internal routes in the injector are optimized by using a CFD analysis and Response Surface Method (RSM). The computational prediction of the internal flow characteristics of the common-rail diesel injector was carried out by using STAR-CCM+7.06 code. In this work, computations were carried out under the assumption that the internal flow passage is a steady-state condition at the maximum needle lift. The design parameters are optimized by using the L16 orthogonal array and polynomial regression, local-approximation characteristics of RSM. Meanwhile, the optimum values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance (ANOVA). In addition, optimal design and prototype design were confirmed by calculating the injection quantities, resulting in the improvement of the injection performance by more than 54%.

• 수산해양기술연구
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• 제26권1호
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• pp.65-75
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• 1990

Bosch법과 Zeuch법의 분사율 측정기를 직접설계, 제작하여 분사율 측정실험을 행한 결과 다음과 같은 결론을 얻었다. 1. Bosch법 분사율 측정기는 분사량의 참 값에 대한 측정오차가 약 $\pm$1%로 정밀도와 신뢰성이 높았다. 2. Bosch법 분사율 측정기에서, 분사율은 연료펌프의 회전수와 부하가 증가할수록 높아지는 반면, 분사기간(ms)은 회전수가 증가할수록 짧아짐을 알 수 있었다. 3. 본 실험에서는, 동일조건하의 단발분사가 연발분사에 비해 전체적으로 분사율이 낮고 기관의 1 cycle당 분사량도 약 30% 정도 적었다. 4. Zeuch법 분사율 측정기로 구한 체적강성계수의 값은 배압이 증가할수록 증가함을 알 수 있었다. 5. Zeuch법 분사율 측정기는 Bosch법 분사율 측정기에 비해 정밀도가 낮았다.

• 한국분무공학회지
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• 제23권4호
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• pp.212-220
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• 2018

As increase the number of vehicles, the issue of greenhouse gas that was emitted by them became important. As a result, greenhouse gas (GHG) regulations are being strengthened and efforts are being actively made to reduce greenhouse gas emissions in the automotive industry. In the other hand, regulations for harmful emission of vehicles have been reinforced by step. Especially, the lastly applied step, so called Euro 6, not only decreased NOx limit down to half of Euro 5 but also introduced real driving emission limit for NOx and PN. It is a challenge for manufacturers to meet the recent GHG regulation as well as the latest emission regulation. To overcome these regulations a De-NOx after-treatment system is being applied to diesel vehicles that are known emitting the lowest GHG among conventional internal combustion engines. At the time of the introduction of Euro 6 emission standard in Korea, in the domestic fuel economy certification test, some diesel vehicles emitted more $CH_4$ than Euro 5 vehicles. As a result, it was confirmed that LNT-equipped vehicles emitted a high level $CH_4$ and the level exceeded the US emission standard. In order to determine the reason, various prior literature was investigated. However, it was difficult to find a detailed study on the methane increase with LNT. In this paper, to determine whether the characteristics of vehicles equipped with LNT the affects the above issue and other greenhouse gases, 6 passenger cars were tested on several emission test modes and ambient temperatures with a environment chamber chassis dynamometer. 2 cars of these were equipped with LNT only, other 2 cars had SCR only, and LNT + SCR were applied to remaining 2 cars. The test result shown that the vehicles equipped with LNT emitted more $CH_4$ than the vehicles with SCR only. Also, $CH_4$ tended to increase as the higher acceleration of the test mode. However, as the test temperature decreases, $CH_4$ tended to decreased. $CO_2$ was not affected by kinds of De-NOx device but characteristic of the test modes.

• 공업화학
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• 제34권6호
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• pp.603-607
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• 2023

수성막포(aqueous film forming foam, AFFF)는 함정 유류화재 대응에 핵심적인 역할을 하는 주요 소화약제 중 하나이다. 이 형태의 소화약제는 막 형성, 열 제거, 연소 억제, 그리고 화학 물질 혼합물을 이용하여 화재를 진압하는 데 효과적이다. 이러한 특성은 유류화재 대응에 있어서 큰 장점을 제공하지만, AFFF는 폼 형태로 분사되어 화재에 대응하는 과정에서 기존 유체와 차별점을 가진다. 따라서 AFFF 폼의 레오미터를 활용한 유변학적 특성 분석은 함정 유류화재 대응을 위한 AFFF 분사 특성 예측에 핵심적인 역할을 수행하며, 이는 효과적인 화재 진압과 밀접한 연관이 있다. 본 연구에서는 레오미터 실험을 통해 AFFF 폼의 비뉴턴 유체(전단박화) 거동을 확인하였으며, 폼의 안정성과 직결되는 데이터들을 얻을 수 있었다. 이러한 실험 데이터들은 AFFF를 활용한 소화 시스템의 효율성을 높이는데 기여할 것으로 기대된다.