• Title/Summary/Keyword: Cold Gas

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Study of Cold Gas Propulsion System Utilizing Butane as Liquefied Propellant (부탄을 액화 연료로 사용한 냉가스 추진 시스템에 대한 연구)

  • Kang, Suk-Jin;Kwon, Ky-Beom;Cho, Dong-Hyun;Lee, Sang-Hyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.4
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    • pp.323-328
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    • 2007
  • A direct application of liquefied gas propellants to a typical small satellite cold gas propulsion system was analyzed. Performance of systems using liquefied gas propellant under consideration was compared to that of a nitrogen cold gas propulsion system. Liquefied gas propellant propulsion system's performance, required tank volume, and required propulsion system mass has been calculated at the same mass, volume, and total impulse condition of a typical nitrogen cold gas propulsion system. It was found that the liquefied gas propulsion system has advantages in performance, volume, and mass, compared to a typical nitrogen cold gas system, and can be directly applied to a cold gas propulsion system.

Investigation of Small Current Interruption Performance for New Type of Interrupting Chamber in SF$_{6}$ Gas Circuit Breaker (신차단방식 SF$_{6}$ 가스 차단기의 소전류 차단성능 연구)

  • Song, Won-Pyo;Kweon, Ki-Yeoung;Lee, Jae-Sung;Song, Ki-Dong;Kim, Maeng-Hyun;Ko, Hee-Seok
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.11
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    • pp.519-526
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    • 2005
  • This paper presents computer simulation results for developing new type of SF$_{6}$ Circuit Breaker in terms of cold gas flow after small current interruption. This cold gas flows down a nozzle into the chamber of a circuit breaker. There are many difficult problems in analyzing the gas flow due to complex geometry, moving boundary, shock wave and so on. When predicting the dielectric capability of a gas circuit breaker after interruption, the gas pressure and density distributions due to the cold gas must be considered in addition to the electrical field imposed across the gas. A self-coded computational fluid dynamics (CFD) program is used for the simulation of cold gas flow in order to evaluate the electrical field characteristic across open contacts and transient characteristics of insulations after small current interruption.

EFFECTS OF CAM PHASE AND SPARK RETARD TO INCREASE EXHAUST GAS TEMPERATURE IN THE COLD START PERIOD OF AN SI ENGINE

  • KIM D.-S.;CHO Y.-S.
    • International Journal of Automotive Technology
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    • v.6 no.6
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    • pp.585-590
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    • 2005
  • The effects of spark timing and exhaust valve timing change on exhaust gas temperature during cold start period of an SI engine are studied through engine bench tests. The exhaust gas temperature increases when the spark timing or valve timing are retarded individually, due to late combustion or slow flame speed. Therefore, exhaust gas temperature shows a large increase when the two timings are retarded simultaneously. However, it is considered that combustion stability during cold start deteriorated under these retarded conditions. To increase exhaust gas temperature for fast warmup of catalysts while maintaining combustion stability, an optimal condition for spark and valve timing retard should be applied for the cold start period.

Material Properties of Thick Aluminum Coating Made by Cold Gas Dynamic Spray Deposition (초음속 저온분사법에 의해 적층된 알루미늄 층의 재료 물성)

  • Lee, Jae-Chul;Ahn, Sung-Hoon
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.10
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    • pp.88-95
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    • 2006
  • Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold-spray uses supersonic gas flow to carry metallic powders to the substrate. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but in this study macro scale deposition was conducted. Properties of aluminum layer by cold-spray deposition such as coefficient of thermal expansion (CTE), modulus of elasticity. hardness, and electric conductivity were measured. The results showed that properties of aluminum layer by cold-spray deposition were different from properties of pure aluminum and aluminum alloy.

Study about material properties of Al particles and deformation of Al alloy substrate by cold gas dynamic spray (초음속 저온분사법에 의한 알루미늄 합금 모재의 변형과 적층된 알루미늄 층의 물성에 대한 연구)

  • Lee, J.C.;Ahn, S.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.145-148
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    • 2006
  • Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold gas dynamic spray is conducted by powder sprayed by supersonic gas jet, and generally called the kinetic spray or cold-spray. Cold-spray was developed in Russia in the early 1980s to overcome the defect of thermal spray method. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but our research team tried to apply this method to macro scale deposition. The macro scale deposition causes deformation of a thin substrate which is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy and properties of deposited aluminum layer such as coefficient of thermal expansion, Elastic modulus, hardness, electric conductivity were measured. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

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HI gas kinematics of galaxy pairs in the Hydra cluster from ASKAP pilot observations

  • Kim, Shin-Jeong;Oh, Se-Heon
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.61.1-61.1
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    • 2020
  • We examine the HI gas kinematics and distribution of galaxy pairs in group or cluster environment from high-resolution Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot observations. We use 22 well-resolved galaxies in the Hydra cluster of which 4 galaxies are visually identified as pairs and others are isolated ones. We perform profile decomposition of HI velocity profiles of the galaxies using a new tool, BAYGAUD which enables us to separate a line-of-sight velocity profile into an optimal number of Gaussian components based on Bayesian MCMC techniques. All the HI velocity profiles of the galaxies are decomposed into kinematically cold or warm gas components with their velocity dispersion, 4~8 km/s or > 8 km/s, respectively. We derive the mass fraction of the kinematically cold gas with respect to the total HI gas mass, f = log10(M_cold / M_HI), of the galaxies and correlate them with their dynamical mass. The cold gas reservoir of the paired galaxies in the Hydra cluster is found to be relatively higher than that of the isolated ones which show a negative correlation with the dynamical mass in general.

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A Study on the District Community Cooling System using LNG Cold Energy (LNG 냉열이용 지역집단 냉방시스템에 대한 연구)

  • Kim, Chung-Kyun;Kim, Seung-Chul
    • Journal of the Korean Institute of Gas
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    • v.14 no.6
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    • pp.27-30
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    • 2010
  • This paper presents the system design process of district community cooling system using LNG cold energy. The newly developed LNG cooling system includes several heat exchangers, LNG storage tank, thermal mass storage tank, several cold energy storage tanks, gas air-conditioners, compressors, constant pressure regulators, cold energy and hot energy supply pipes. In addition, the gas air-conditioner system is installed to supply not sufficient cold energy due to low level of city gas consumptions during a summer period. This system design is very effective and safe to supply cold energy mass of fresh air by exchanging two thermal masses of an air and 200kcal/kg cold energy of LNG. The district community cooling system with LNG cold energy does not produce CO2 and freon gases in the air.

Design and Exergy Analysis for a Combined Cycle of Liquid/Solid $CO_2$ Production and Gas Turbine using LNG Cold/Hot Energy

  • Lee, Geun-Sik
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.1
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    • pp.34-45
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    • 2007
  • In order to reduce the compression power and to use the overall energy contained in LNG effectively, a combined cycle is devised and simulated. The combined cycle is composed of two cycles; one is an open cycle of liquid/solid carbon dioxide production cycle utilizing LNG cold energy in $CO_2$ condenser and the other is a closed cycle gas turbine which supplies power to the $CO_2$ cycle, utilizes LNG cold energy for lowering the compressor inlet temperature, and uses the heating value of LNG at the burner. The power consumed for the $CO_2$ cycle is investigated in terms of a solid $CO_2$ production ratio. The present study shows that much reduction in both $CO_2$ compression power (only 35% of the power used in conventional dry ice production cycle) and $CO_2$ condenser pressure could be achieved by utilizing LNG cold energy and that high cycle efficiency (55.3% at maximum power condition) in the gas turbine could be accomplished with the adoption of compressor inlet cooling and regenerator. Exergy analysis shows that irreversibility in the combined cycle increases linearly as a solid $CO_2$ production ratio increases and most of the irreversibility occurs in the condenser and the heat exchanger for compressor inlet cooling. Hence, incoming LNG cold energy to the above components should be used more effectively.

Comparative studies of gasification potential of agro-waste with wood and their characterization

  • Tripathi, Amarmani;Shukla, S.K.
    • Advances in Energy Research
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    • v.3 no.3
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    • pp.181-194
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    • 2015
  • In this work, an experimental study of the gasification on wood was carried out in downdraft type fixed bed Gasifier attached with 10 kW duel fuel diesel engine. The main objective of the study was to use wood as the biomass fuel for downdraft Gasifier and to evaluate the operating parameter of gasifier unit to predict its performance in terms of gas yield and cold gas efficiency. The influence of different biomass on fuel consumption rate, gas yield and cold gas efficiency was studied. Composition of producer gas was also detected for measuring the lower heating value of producer gas to select the feed stock so that optimum performance in the existing gasifier unit can be achieved. Under the experimental conditions, Lower heating value, of producer gas, cold gas efficiency and gas yields, using wood as a feed stock, are $4.85MJ/m^3$, 46.57% and $0.519m^3/kg$.

Effect of Carrier Gases on the Microstructure and Properties of Ti Coating Layers Manufactured by Cold Spraying (저온 분사 공정으로 제조된 Ti 코팅층의 미세조직 및 물성에 미치는 송급 가스의 영향)

  • Lee, Myeong-Ju;Kim, Hyung-Jun;Oh, Ik-Hyun;Lee, Kee-Ahn
    • Journal of Korean Powder Metallurgy Institute
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    • v.20 no.1
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    • pp.24-32
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    • 2013
  • The effect of carrier gases (He, $N_2$) on the properties of Ti coating layers were investigated to manufacture high-density Ti coating layers. Cold spray coating layers manufactured using He gas had denser and more homogenous structures than those using $N_2$ gas. The He gas coating layers showed porosity value of 0.02% and hardness value of Hv 229.1, indicating more excellent properties than the porosity and hardness of $N_2$ gas coating layers. Bond strengths were examined, and coating layers manufactured using He recorded a value of 74.3 MPa; those manufactured using $N_2$ gas had a value of 64.6 MPa. The aforementioned results were associated with the fact that, when coating layers were manufactured using He gas, the powder could be easily deposited because of its high particle impact velocity. When Ti coating layers were manufactured by the cold spray process, He carrier gas was more suitable than $N_2$ gas for manufacturing excellent coating layers.