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RISS 인기검색어
- 검색키워드
- 저자 : Ommi, Fathollah (검색결과 5 건)
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Using Acoustic Liner for Fan Noise Reduction in Modern Turbofan Engines
Azimi, Mohammadreza,Ommi, Fathollah,Alashti, Naghmeh Jamshidi The Korean Society for Aeronautical and Space Scie 2014 International Journal of Aeronautical and Space Sc Vol.15 No.1
With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.
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Kamran Poorghasemi,Fathollah Ommi,Hamed Yaghmaei,Amin Namaki 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1
NO and Soot trade off is an important challenge for engineers in DI Diesel engines. This paper, introduces multiple injection as a strategy for simultaneous reduction of NO and Soot emissions on a DI diesel engine and also proposes a new concept of variable injection pressure and studies its effect on the engine emissions. To evaluate the benefits of multiple injection strategies and to reveal combustion mechanism, modified three dimensional CFD code KIVA-3V was developed. Results showed that using post injection with appropriate dwell between injection pulses has a great effect on simultaneous reduction of the emissions. Based on computational results, NO reduction formation mechanism in multiple injection strategy is as a single injection with retarded injection timing. It is shown that reduction in soot formation is because of the fact that in split fuel injection the soot, which is producing rich regions at the head of fuel spray, are not replenished by newly injected fuel in post injection pulse. Also increasing injection pressure in post injection will reduce the Soot emission dramatically while NO emission is in control for increase of fuel burning rate in post injection pulse.
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Using Acoustic Liner for Fan Noise Reduction in Modern Turbofan Engines
Mohammadreza Azimi,Fathollah Ommi,Naghmeh Jamshidi Alashti 한국항공우주학회 2014 International Journal of Aeronautical and Space Sc Vol.15 No.1
With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.
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COMBUSTION DEVELOPMENT OF A BI-FUEL ENGINE
O. S. ABIANEH,M. MIRSALIM2,F. OMMI 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.1
Environmental improvement and energy issues are increasingly becoming more important as worldwide concerns. Natural gas is a good alternative fuel that can help to improve these issues because of its large quantity and clean burning characteristics. This paper provides the experimental performance results of a Bi-Fuel engine that uses Compressed Natural Gas as its Primary fuel and gasoline as its secondary fuel. This engine is a modification of the basic 1.4-liter gasoline engine. Generally, on the unmodified base engine, torque and power for CNG fuel are considerably lower than gasoline fuel. In this paper, the influence of fuels on wall temperature, performance and emissions are investigated. Environmental improvement and energy issues are increasingly becoming more important as worldwide concerns. Natural gas is a good alternative fuel that can help to improve these issues because of its large quantity and clean burning characteristics. This paper provides the experimental performance results of a Bi-Fuel engine that uses Compressed Natural Gas as its Primary fuel and gasoline as its secondary fuel. This engine is a modification of the basic 1.4-liter gasoline engine. Generally, on the unmodified base engine, torque and power for CNG fuel are considerably lower than gasoline fuel. In this paper, the influence of fuels on wall temperature, performance and emissions are investigated.
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Experimental study of fine center electrode spark plug in Bi-fuel engines
Saeed Javan,Syed Shahabodin Alaviyoun,Seyed Vahid Hosseini,F. OMMI 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.3
In the present work, the erosion of platinum fine center electrode spark plugs and conventional nickel plugs are investigated in a gasolineand natural gas bi-fuel engine. The effect of electrode erosion is evaluated by comparing the required ignition voltage and cold startability of the different plug designs. After durability tests, platinum fine center electrode plug had insignificant electrode erosion andnegligible gap growth; whereas the nickel plug had notable erosion and gap growth. There was no detectable side sparking for fine centerelectrode plugs. In terms of performance, the required ignition voltage of fine center electrode plug was lower than conventional sparkplug. Also, results of a cold start test demonstrated that the starting time of the engine with fine electrode plugs was lower than conventionalspark plugs. The surface of electrodes was studied by the scanning electron microscope and the energy dispersive X-ray spectroscopytechniques. Cracking and peeling was observed on the surface of the nickel conventional electrodes, but not on the surface of theplatinum fine electrodes. These tests show that platinum fine center electrodes could be suitable for gasoline/natural gas bi-fuel engines tomeet long lifetime demand.
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