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Wyszukujesz frazę "negative valve overlap" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Increase of high load limit in a gasoline HCCI engine
Autorzy:
Hunicz, J.
Kordos, P.
Gęca, M.
Powiązania:
https://bibliotekanauki.pl/articles/242189.pdf
Data publikacji:
2012
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
HCCI engine
negative valve overlap
high load limit
mechanical boost
Opis:
Engine operation in HCCI mode allows for improvement of thermal efficiency and substantial reduction NOX emission. The most production feasible solution for gasoline HCCI engine is application of exhaust gas trapping using a negative valve overlap. This technique increases thermal energy of a mixture, thus allowing for auto-ignition at moderate compression ratios. However, high exhaust gas re-circulation rate decreases volumetric efficiency. As a result, achievable engine loads are also reduced. Supercharging can be applied in order to improve volumetric efficiency and extend high load limit. However, increase of amount of intake air can lead to reduction of start of compression temperature via decrease of residuals in a mixture. In order achieve HCCI mode of combustion, temperature of start of compression must be kept within narrow limits. In this study experimental and modeling investigations were presented. Experiments were carried out using single cylinder research engine. The engine was equipped with fully variable valvetrain and direct gasoline injection. Application of mechanical boosting allowed for widening achievable load range in HCCI mode of operation. Numerical calculations allowed for determination of admissible valvetrain settings and intake pressure, which guarantee proper temperature of start of compression.
Źródło:
Journal of KONES; 2012, 19, 4; 231-238
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Combustion control in gasoline HCCI engine with direct fuel injection and exhaust gas trapping
Autorzy:
Hunicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/246912.pdf
Data publikacji:
2010
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
homogeneous charge compression ignition
variable valve timing
negative valve overlap
gasoline
direct injection
Opis:
Homogeneous charge compression ignition (HCCI) seems to be the most promising solution for gasoline engines in the light of future emissions regulations. This novel combustion technique allows for significant reduction of fuel consumption and engine-out NOX emissions at low and medium engine load/speed conditions. High heat release rate enables realization of the Otto cycle close to ideal, increasing thermal efficiency. Among different approaches to invoke an auto-ignition of air-fuel mixture, exhaust gas trapping with the use of a negative valve overlap is under intensive investigations. The paper presents research results ofcontrolling an auto-ignition and combustion phasing in a single cylinder gasoline engine with direct fuel injection operated in the negative valve overlap mode. The experiments were performed at variable valvetrain settings, providing a control of EGR rate and volumetric efficiency. Additionally, the combustion process was investigated at variable air-fuel ratio. It was found that volumetric efficiency and EGR ratę are mainly dependent on exhaust valve timing, while a timing of intake valve determined combustion on-set and its duration. The effects of EGR rate and air-fuel ratio on combustion timing and exhaust gas emissions were isolated. The direct fuel injection showed its benefits versus mixture formation outside the cylinder. The application of variable injection timing provided additional possibility to control the combustion timing and exhaust emissions. However, it was found that the fuel injection strategy should be related to the engine load conditions.
Źródło:
Journal of KONES; 2010, 17, 2; 137-144
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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