• 제목/요약/키워드: Mixed exhaust

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Firing Test of Core Engine for Pre-cooled Turbojet Engine

  • Taguchi, Hideyuki;Sato, Tetsuya;Kobayashi, Hiroaiki;Kojima, Takayuki;Fukiba, Katsuyoshi;Masaki, Daisaku;Okai, Keiichi;Fujita, Kazuhisa;Hongoh, Motoyuki;Sawai, Shujiro
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.115-121
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    • 2008
  • A core engine for pre-cooled turbojet engines is designed and its component performances are examined both by CFD analyses and experiments. The engine is designed for a flight demonstration of precooled turbojet engine cycle. The engine uses gas hydrogen as fuel. The external boundary including measurement devices is set within $23cm{\times}23cm$ of rectangular cross section, in order to install the engine downstream of the air intake. The rotation speed is 80000 rpm at design point. Mixed flow compressor is selected to attain high pressure ratio and small diameter by single stage. Reverse type main combustor is selected to reduce the engine diameter and the rotating shaft length. The temperature at main combustor is determined by the temperature limit of non-cooled turbine. High loading turbine is designed to attain high pressure ratio by single stage. The firing test of the core engine is conducted using components of small pre-cooled turbojet engine. Gas hydrogen is injected into the main burner and hot gas is generated to drive the turbine. Air flow rate of the compressor can be modulated by a variable geometry exhaust nozzle, which is connected downstream of the core engine. As a result, 75% rotation speed is attained without hazardous vibration and heat damage. Aerodynamic performances of both compressor and turbine are obtained and evaluated independently.

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A Study on the Thermal and Pollution Performances of the Heating Boilers with NG-H2 Mixture Ratio (난방용 보일러에서 NG-H2 혼소율에 따른 열 및 공해 성능의 검토)

  • SEO, JUNSUN;KIM, YOUNG-JIC;PARK, JUNKYU;LEE, CHANG-EON
    • Transactions of the Korean hydrogen and new energy society
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    • v.32 no.6
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    • pp.573-584
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    • 2021
  • Hydrogen is evaluated as one of the new energy sources that can overcome the limitations and pollution problems of conventional fossil fuels. Although hydrogen is CO2-free, attention is required in NOx emission and flame stability in order to use hydrogen in existing gas fuel system. However, use of electric grids is an unrealistic strategy for decarbonization for residential and commercial heating. Instead, use of H2 that utilizes city gas grid is suggested as a reasonable alternative in terms of compatibility with existing systems, economic feasibility, and accessibility. In this study, the thermal efficiency and NOx performance of the boiler according to the H2 mixture ratio and vapor humidified ratio are reviewed for a humidified NG-H2 boiler that vapor humidity to combustion air. Mixed fuel with H2 (20%) is almost similar to NG in terms of efficiency, flame temperature, and pollution performance. Thus, it is expected to be directly compatible with the existing NG system. If the exhaust temperature of the H2 boiler is lowered to around 60℃ at a humidified ratio of 15-20%, the NOx emission concentration can be suppressed to about 5-10 ppm. The level of efficiency reaches 87% of the rated load efficiency, which is equivalent to the highest grade achievable.

A Study on the Structural Stability of Nozzle Manufactured with 5-axis Machining (5축 가공으로 제작한 노즐의 구조 안정성에 관한 연구)

  • Changwook Lee;Yongseok Park;DuckYong Jo;Seong Man Choi
    • Journal of the Korean Society of Propulsion Engineers
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    • v.26 no.5
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    • pp.44-51
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    • 2022
  • In this study, 5-axis machining was proposed as a method for manufacturing a nozzle with a curved shape, and flow analysis and structural analysis were used for structural validation of the manufactured geometry. The program used for CFD obtained the internal temperature and pressure distribution of the nozzle using STAR-CCM+ and used it as the boundary condition for structural analysis. For structural analysis, the commercial program NASTRAN was used, and stress was calculated using the von-mises technique. Based on the maximum stress value generated, the safety margin was 0.78 and the safety margin of the bearing stress was 46.8. In addition, the creep life was calculated as 9.97 x 1012 hours using the Larson-Miller parametric method and applying the maximum stress value of 187 MPa and the exhaust gas perfectly mixed temperature of 463 K.

Membrane-Based Carbon Dioxide Separation Process for Blue Hydrogen Production (블루수소 생산을 위한 이산화탄소 포집용 2단 분리막 공정 최적화 연구)

  • Jin Woo Park;Joonhyub Lee;Soyeon Heo;Jeong-Gu Yeo;Jaehoon Shim;Jinhyuk Yim;Chungseop Lee;Jin Kuk Kim;Jung Hyun Lee
    • Membrane Journal
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    • v.33 no.6
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    • pp.344-351
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    • 2023
  • The membrane separation process for carbon dioxide capture from hydrogen reformer exhaust gas has been developed. Using a commercial membrane module, a multi-stage process was developed to achieve 90% of carbon dioxide purity and 90% of recovery rate for ternary mixed gas. Even if a membrane module with being well-known properties such as material selectivity and permeability, the process performance of purity and recovery widely varies depending on the stage-cut, the pressure at feed and permeate side. In this study, we verify the limits of capture efficiency at single-stage membrane process under various operating conditions and optimized the two-stage recovery process to simultaneously achieve high purity and recovery rate.

Assessment of Occupational Health Risks for Maintenance Work in Fabrication Facilities: Brief Review and Recommendations

  • Dong-Uk Park;Kyung Ehi Zoh;Eun Kyo Jeong;Dong-Hee Koh;Kyong-Hui Lee;Naroo Lee;Kwonchul Ha
    • Safety and Health at Work
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    • v.15 no.1
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    • pp.87-95
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    • 2024
  • Background: This study focuses on assessing occupational risk for the health hazards encountered during maintenance works (MW) in semiconductor fabrication (FAB) facilities. Objectives: The objectives of this study include: 1) identifying the primary health hazards during MW in semiconductor FAB facilities; 2) reviewing the methods used in evaluating the likelihood and severity of health hazards through occupational health risk assessment (OHRA); and 3) suggesting variables for the categorization of likelihood of exposures to health hazards and the severity of health effects associated with MW in FAB facilities. Methods: A literature review was undertaken on OHRA methodology and health hazards resulting from MW in FAB facilities. Based on this review, approaches for categorizing the exposure to health hazards and the severity of health effects related to MW were recommended. Results: Maintenance workers in FAB facilities face exposure to hazards such as debris, machinery entanglement, and airborne particles laden with various chemical components. The level of engineering and administrative control measures is suggested to assess the likelihood of simultaneous chemical and dust exposure. Qualitative key factors for mixed exposure estimation during MW include the presence of safe operational protocols, the use of air-jet machines, the presence and effectiveness of local exhaust ventilation system, chamber post-purge and cooling, and proper respirator use. Using the risk (R) and hazard (H) codes of the Globally Harmonized System alongside carcinogenic, mutagenic, or reprotoxic classifications aid in categorizing health effect severity for OHRA. Conclusion: Further research is needed to apply our proposed variables in OHRA for MW in FAB facilities and subsequently validate the findings.

Effect of CNG Heating Value Variations on Emissions Characteristics in a Diesel-CNG Dual-Fuel Engine (CNG 발열량 변화가 Diesel-천연가스 혼소엔진 배기 특성에 미치는 영향)

  • Jang, Hyongjun;Yoon, Junkyu;Lee, Sunyoup;Kim, Yongrae;Kim, Junghwan;Kim, Changgi
    • Journal of the Korean Institute of Gas
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    • v.20 no.6
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    • pp.43-49
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    • 2016
  • In this paper, purpose of study is emissions characteristics according to effects of heating value variations of CNG fuel in a dual-fuel engine fueled by diesel and natural gas. For heating value variation of CNG fuel, nitrogen gas was mixed with pure CNG fuel. So the higher heating value was changed from $10,400kcal/Nm^3$ to $9,400kcal/Nm^3$. Under one condition of CNG substitution rate was fixed at 80%, diesel fuel was injected at a fixed injection timing of 16 CAD BTDC and fuel pressure was also fixed at 110 MPa. The condition of tested engine was 1800 rpm and 500Nm. Emissions were sampled in exhaust pipe was located at downstream turbocharger. As a result, emissions characteristics were checked in heating value variations of CNG fuel with mixed nitrogen gas THC, $CH_4$ and CO emissions decreased and NOx and $CO_2$ increased.

A Study on the Oxy-Combustion of the Coal in Drop Tube Furnace (Drop Tube Furnace에서 석탄의 순산소 연소 특성)

  • Roh, Seon Ah;Yun, Jin Han;Lee, Jung Kyu;Keel, Sang In;Min, Tai Jin;Kim, Sang-Bok;Park, In-Yong;Han, Bangwoo;Kim, Jin-Tae
    • Clean Technology
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    • v.27 no.4
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    • pp.367-371
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    • 2021
  • The oxy-combustion system is one of the carbon recovery and storage technologies (CCS: Carbon capture & storage) that performs coal combustion using pure oxygen and recirculated flue gas. This is a technology that facilitates storage of carbon dioxide by generating an exhaust gas consisting of only carbon dioxide without a process of separating carbon dioxide and nitrogen when coal is burned using pure oxygen and recirculated flue gas mixture instead of a conventional air combustion system that produces carbon dioxide and nitrogen mixed exhaust gas. In this study, the characteristics of generated NO and SO2 as atmospheric pollutants during oxy-combustion were examined using O2/CO2 mixed simulation gas. The reaction temperature was varied from 900 ℃ to 1200 ℃ and oxygen partial pressure was varied from 30% to 50%. The results showed that NO and SO2 concentrations in flue gas increased as the oxygen concentration and the reaction temperature in the furnace increased. The partial pressure of CO2 in flue gas also increased as the oxygen concentration and the reaction temperature in the furnace increased. As a results of comparing NO production of 30% O2/CO2 oxy-combustion with air combustion, NO in flue gas increased with reaction temperature in both experiments and NO of oxy-combustion was 40 ~ 80 ppm lower than that of air combustion.

CO2 Decomposition Characteristics of Activated(Fe1-xMnx)3O4-δ and (Fe1-xCox)3O4-δ (활성화된(Fe1-xMnx)3O4-δ과 (Fe1-xCox)3O4-δ의 이산화탄소 분해 특성)

  • Park, Won-Shik;Oh, Kyoung-Hwan;Rhee, Sang-In;Suhr, Dong-Soo
    • Korean Journal of Materials Research
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    • v.23 no.4
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    • pp.219-226
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    • 2013
  • Activated magnetite ($Fe_3O_{4-{\delta}}$) has the capability of decomposing $CO_2$ proportional to the ${\delta}$-value at comparatively low temperature of $300^{\circ}C$. To enhance the $CO_2$ decomposition capability of $Fe_3O_{4-{\delta}}$, $(Fe_{1-x}Co_x)_3O_{4-{\delta}}$ and $(Fe_{1-x}Mn_x)_3O_{4-{\delta}}$ were synthesized and then reacted with $CO_2$. $Fe_{1-x}Co_xC_2O_4{\cdot}2H_2O$ powders having Fe to Co mixing ratios of 9:1, 8:2, 7:3, 6:4, and 5:5 were synthesized by co-precipitation of $FeSO_4{\cdot}7H_2O$ and $CoSO_4{\cdot}7H_2O$ solutions with a $(NH_4)_2C_2O_4{\cdot}H_2O$ solution. The same method was used to synthesize $Fe_{1-x}Mn_xC_2O_4{\cdot}2H_2O$ powders having Fe to Mn mixing ratios of 9:1, 8:2, 7:3, 6:4, 5:5 with a $MnSO_4{\cdot}4H_2O$ solution. The thermal decomposition of synthesized $Fe_{1-x}Co_xC_2O_4{\cdot}2H_2O$ and $Fe_{1-x}Mn_xC_2O_4{\cdot}2H_2O$ was analyzed in an Ar atmosphere with TG/DTA. The synthesized powders were heat-treated for 3 hours in an Ar atmosphere at $450^{\circ}C$ to produce activated powders of $(Fe_{1-x}Co_x)_3O_{4-{\delta}}$ and $(Fe_{1-x}Mn_x)_3O_{4-{\delta}}$. The activated powders were reacted with a mixed gas (Ar : 85 %, $CO_2$ : 15 %) at $300^{\circ}C$ for 12 hours. The exhaust gas was analyzed for $CO_2$ with a $CO_2$ gas analyzer. The decomposition of $CO_2$ was estimated by measuring $CO_2$ content in the exhaust gas after the reaction with $CO_2$. For $(Fe_{1-x}Mn_x)_3O_{4-{\delta}}$, the amount of $Mn^{2+}$ oxidized to $Mn^{3+}$ increased as x increased. The ${\delta}$ value and $CO_2$ decomposition efficiency decreased as x increased. When the ${\delta}$ value was below 0.641, $CO_2$ was not decomposed. For $(Fe_{1-x}Co_x)_3O_{4-{\delta}}$, the ${\delta}$ value and $CO_2$ decomposition efficiency increased as x increased. At a ${\delta}$ value of 0.857, an active state was maintained even after 12 hours of reaction and the amount of decomposed $CO_2$ was $52.844cm^3$ per 1 g of $(Fe_{0.5}Co_{0.5})_3O_{4-{\delta}}$.

Effect of Injection Pressure and Injection Timing on Spray and Flame Characteristics of Spray-Guided Direct-Injection Spark-Ignition Engine under Lean Stratified Combustion Operation (성층희박연소 운전조건에서 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 분무 및 화염특성)

  • Oh, Heechang;Lee, Minsuk;Park, Jungseo;Bae, hoongsik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.3
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    • pp.221-228
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    • 2013
  • An experimental study was carried out to investigate the effects of the injection timing on the spray and combustion characteristics in a spray-guided direct-injection spark-ignition (DISI) engine under lean stratified operation. An in-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were employed in this study. The combustion in a stratified DISI engine was found to have both lean premixed and diffusion controlled flame combustion characteristics. The injection timing condition corresponding to the stratified mixture characteristics was verified to be a dominant factor for these flame characteristics. For the early injection timing, a non-luminous blue flame and low combustion efficiency were observed as a result of the lean homogeneous mixture formation. On the other hand, a luminous sooting flame was shown at the late injection timing because of an under-mixed mixture formation. In addition, the smoke emission and incomplete combustion products were increased at the late injection timing as a result of the increased locally rich area. On the other hand, the NOx emissions decreased and IMEP increased as the injection timing retarded. The combustion phasing produced by the injection timing was verified as the reason for this observation.

Evaluation of Characteristics of Welding Zones Welded with Inconel 718 Filler Metal to Piston Crown Forged Material (피스톤 크라운용 단강에 인코넬 718 용접재료로 용접된 용접부의 특성 평가)

  • Lee, Sung-Yul;Moon, Kyung-Man;Jeong, Jae-Hyun;Lee, Myeong-Hoon;Baek, Tae-Sil
    • Journal of Ocean Engineering and Technology
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    • v.30 no.4
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    • pp.334-340
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    • 2016
  • The combustion chamber of a diesel engine is often exposed to a more serious wear and corrosion environment than other parts of the engine because its temperature increases as a result of using heavy oil of low quality. Therefore, repair and built-up welding methods must be performed on worn or corroded parts of the piston crown, exhaust valve, etc. from an economical point of view. In this study, Inconel 718 filler metal was used in repair welding on the groove of a forged steel specimen for a piston crown, along with built-up welding on the surface of another forged steel specimen. Then, the corrosion characteristics of the weld metal zone for the repair welding and the deposited metal zone for the built-up welding were investigated using electrochemical methods in a 35% H2SO4 solution. The deposited metal zone indicated better corrosion resistance than the weld metal zone, showing a nobler corrosion potential, higher impedance, and smaller corrosion current density. It is considered that metal elements with good corrosion resistance were generally included in the filler metal, and these elements were also greatly involved in the deposited meta by built-up welding, whereas the weld metal consisted of metal elements mixed with both the filler metal and base metal elements because of the molten pool produced by the repair welding. Finally, it is considered that the hardness of the weld metal was increased by the repair welding, whereas the built-up welding improved the corrosion resistance of the deposited metal.