• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.1
• /
• pp.1-11
• /
• 2022

In a gas turbine, fuel is exposed to a high temperature environment until it is fed to the combustor through the injector. Hydrocarbon fuels can coke under high temperature conditions, which can cause coking material to deposit on fuel lines or block the injector passages. In this study, a specimen simulating a fuel line located inside a gas turbine and Jet A-1 were heated using electric devices. Jet A-1 coking tests were performed by changing the wall temperature of the stainless steel specimen and the temperature of Jet A-1 supplied to the specimen. After the coked specimens were cut, the coking material and the inner surface were analyzed using an energy dispersive X-ray spectrometer and a field emission scanning electron microscope.

• Journal of Aerospace System Engineering
• /
• v.17 no.6
• /
• pp.72-81
• /
• 2023

Hydrogen-fueled gas turbines are a promising technology that can resolve the carbon dioxide emission issue as future aviation propulsion engines and carbon-free power generations. To achieve high efficiency and stability of gas turbines using 100% hydrogen as fuel, an innovative design of combustor systems is necessary to consider the characteristics of hydrogen, which are different from those of conventional hydrocarbon fuels. Micromix is a combustor design method, which aims to terminate the reaction quickly by intense mixing of fuel and air, consequently reducing NOx and increasing the stability. In this paper, we examine the principles and design process of micromix combustors as a pure-hydrogen combustion technology, and we introduce a design of a 30 kW micromix hydrogen combustor for research.

• Journal of Life Science
• /
• v.8 no.3
• /
• pp.257-262
• /
• 1998

Benzo(a)pyrene(B(a)P), an extensively studied polycyclic aromatic hydrocarbon(PAH), is a common contaminant produced through the burning of fossil fuels, particularly coal, and from the exhaust products of internal combustion engines. It produces a wide range of toxicities, including carcinogenicity in experimental animals. B(a)P has been shown to suppress systemic immunity in experimental animals, which may contribute to the growth of the chemical-induced tumors. Using colorimetric MTT assay natural killer(NK) cell-mediated growth inhibition of tomor cell was measured in normal and B(a)P-exposed C57BL/6 mice. Non-adherent splenocytes of normal or B(a)P-exposed mice were cultured with Yac-1 cells at four different effector/target(E/T) cell ratios ranging from 200/1, 100/1, 50/1, and 25/1 in an assay volume of 0.1 ml. After the optical density of culture wells containing MTT solution was measured at a wavelength of 540 nm, the percentage of dead cells relative to the control target cell number was calculated. The NK activity of B(a)P-exposed mice was markedly lower than that of non-exposed mice group at all E/T ratios. These results indicated that suppression of NK cell activity may play a role in allowing for the growth of tumors.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.12
• /
• pp.1129-1135
• /
• 2013

In this, three types of natural gas were employed to investigate the effect of low-calorific natural gas on the performance of and emissions from a heavy-duty CNG engine. The performance and emission characteristics were analyzed by conducting a full-load test, WHSC mode test, and WHTC mode test. The results showed that the torque of low-calorific natural gas with $9,800kcal/Nm^3$ of higher heating value decreased by 4.4 compared to that of the current natural gas with $10,400kcal/Nm^3$ of heating value. With low-calorific fuels, CO, $CO_2$, and $NO_x$ emissions decreased. However, THC emissions increased. According to the WHSC and WHTC mode test results, the thermal efficiency increased and the emission characteristics showed a similar trend to the full-load test results. Low-calorific natural gases cause a decrease in torque at full-load operation conditions and an increase in hydrocarbon emissions.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.306-309
• /
• 2005

One of the most critical issues in sol id oxide fuel cell (SOFC)running on hydrocarbon fuels is the risk of carbon formation from the fuel gas. The simple method to reduce the risk of carbon formation from the reactions is to add steam to the fuel stream, leading to the carbon gasification react ion. However, the addition of steam to fuel is not appropriate for the auxiliary power unit (APU) and potable power generation (PPG) systems due to an increase of complexity and bulkiness. In this regard, many researchers have focused on so-called 'direct methane' operation of SOFC, which works with dry methane without coking. However, coking can be suppressed only by the operation with a high current density, which may be a drawback especially for the APU and PPG systems. The single chamber fuel cell (SC-SOFC) is a novel simplification of the conventional SOFC into which a premixed fuel/air mixture is introduced. It relies on the selectivity of the anode and cathode catalysts to generate a chemical potential gradient across the cell. Moreover it allows compact and seal-free stack design. In this study, we fabricated honeycomb type mixed-gas fuel cell (MGFC) which has advantages of stacking to the axial direction and increasing volume power density. Honeycomb-structured SOFC with four channels was prepared by dry pressing method. Two alternative channels were coated with electrolyte and cathode slurry in order to make cathodic reaction sites. We will discuss that the anode supported honeycomb type cell running on mixed gas condition.

• Journal of the Korean Electrochemical Society
• /
• v.10 no.2
• /
• pp.110-115
• /
• 2007

Solid oxide fuel cell(SOFC) has high fuel flexibility due to its high operating temperatures. Hydrocarbonaceous fuels such as diesel has several advantages such as high energy density and established infrastructure for fuel cell applications. However diesel reforming has technical problems like coke formation in a reactor, which results in catastrophic failure of whole system. Performance degradation of diesel autothermal reforming (ATR) leads to increase of undesirable hydrocarbons at reformed gases and subsequently degrades SOFC performance. In this study, we investigate the degradation of SOFC performance(OCV, open circuit voltage) under hydrocarbon(n-Butane) feeds and characteristics of diesel performing under various ratios of reactants($H_2O/C,\;O_2/C$ molar ratios) for improvement of SOFC performance. Especially we achieved relatively high performance of diesel ATR under $H_2O/C=0.8,\;O_2/C=3$ condition.

• Clean Technology
• /
• v.24 no.1
• /
• pp.70-76
• /
• 2018

Pyrolysis of Saccharina japonica in an Auger reactor was conducted by varying the temperature and the auger speed and then physicochemical properties of the S. japonica-derived pyrolysis oil were analyzed. The maximum yield of S. japonica-derived pyrolysis oil (32 wt%) was obtained at a pyrolysis temperature of $412^{\circ}C$ and an auger speed of 20 rpm. Due to low carbon content and high oxygen content in the pyrolysis oil, the higher heating value of S. japonica-derived pyrolysis oil was $23.6MJ\;kg^{-1}$, which was about 60% that of conventional hydrocarbon fuels. By GC/MS analysis, 1,4-Anhydro-d-galactitol, dianhydromannitol, 1-hydroxy 2-propanone and isosorbide were identified as the main chemical compounds of S. japonica-derived pyrolysis oil. The bio-char has low higher heating value ($13.0MJ\;kg^{-1}$) due to low carbon content and high oxygen content and contains a large amount of inorganic components and sulfur.

• Journal of Soil and Groundwater Environment
• /
• v.14 no.5
• /
• pp.62-70
• /
• 2009

A field soil highly contaminated with petroleum hydrocarbons (JP-8 and diesel fuels) was employed for its remediation by a lab-scale thermal desorption process. The soil was collected in the vicinity of an underground storage tank in a closed military base and its contamination level was as high as 4,476 ppm as total petroleum hydrocarbon (TPH). A lab scale directly-heated low temperature thermal desorption (LTTD) system of 10-L capacity was developed and operated for the thermal treatment of TPH contaminated soils in this study. The desired operation temperature was found to be approximately $200-300^{\circ}C$ from the thermal gravimetric analysis of the contaminated field soils. The removal efficiencies higher than 90% were achieved by the LTTD treatment at $200^{\circ}C$ for 10 min as well as at $300^{\circ}C$ for 5 min. As the water content in the soils increased and therefore they were likely to be present as lumps, the removal efficiency noticeably decreased, indicating that a pre-treatment such as field drying should be required. The analysis of physical and chemical properties of soils before and after the LTTD treatment demonstrated that no significant changes occurred during the thermal treatment, supporting no needs for additional post-treatments for the soils treated by LTTD. The results presented in this study are expected to provide useful information for the field application and verification of LTTD for the highly contaminated geo-environment.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.1
• /
• pp.1-11
• /
• 2017

Bio-oil has attracted considerable interest as one of the promising renewable energy resources because it can be used as a feedstock in conventional petroleum refineries for the production of high value chemicals or next-generation hydrocarbon fuels. Zeolites have been shown to effectively promote cracking reactions during pyrolysis resulting in highly deoxygenated and hydrocarbon-rich compounds and stable pyrolysis oil products. In this study, catalytic pyrolysis was applied to upgrade bio-oil from yellow poplar and then fuel characteristics of upgraded bio-oil was investigated. Yellow Poplar(500 g) which ground 0.3~1.4 mm was processed into bio-oil by catalytic pyrolysis for 1.64 seconds at $465^{\circ}C$ with Control, Blaccoal, Whitecoal, ZeoliteY and ZSM-5. Under the catalyst conditions, bio-oil productions decreased from 54.0%(Control) to 51.4 ~ 53.5%, except 56.2%(Blackcoal). HHV(High heating value) of upgraded bio-oil was more lower than crude bio-oil while the water content increased from 37.4% to 37.4 ~ 45.2%. But the other properties were improved significantly. Under the upgrading conditions, ash and TAN(Total Acid Number) is decrease and particularly important as transportation fuel, the viscosity of bio-oil decreased from 6,933 cP(Control) to 2,578 ~ 4,627 cP. In addition, ZeoliteY was most effective on producing aromatic hydrocarbons and decreasing of from the catalytic pyrolysis.

• Korean Chemical Engineering Research
• /
• v.54 no.3
• /
• pp.394-403
• /
• 2016

$H_2$ production by chemical looping is an efficient method to convert hydrocarbon fuel into hydrogen with the simultaneous capture of concentrated $CO_2$. This process involves the use of an iron based oxygen carrier that transfers pure oxygen from oxidizing gases to fuels by alternating reduction and oxidation (redox) reactions. The enhanced reactivities of copper oxide doped iron-based oxygen carrier were reported, however, the fundamental understandings on the interaction between $Fe_2O_3$ and CuO are still lacking. In this study, we studied the effect of dopant of CuO to $Fe_2O_3/ZrO_2$ particle on the morphological changes and the associated reactivity using various methods such as SEM/EDX, XRD, BET, TPR, XPS, and TGA. It was found that copper oxide acted as a chemical promoter that change chemical environment in the iron based oxygen carrier as well as a structural promoter which inhibit the agglomeration. The enhanced reduction reactivity was mainly ascribed to the increase in concentration of $Fe^{2+}$ on the surface, resulting in formation of charge imbalance and oxygen vacancies. The CuO doped $Fe_2O_3/ZrO_2$ particle also showed the improved reactivity in the steam oxidation compared to $Fe_2O_3/ZrO_2$ particle probably due to acting as a structural promoter inhibiting the agglomeration of iron species.