Wyniki wyszukiwania - BazTech

1

Experimental and modeling study of the gasoline HCCI engine with internal gas recirculation

Hunicz J., Gęca M.

Silniki Spalinowe

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2013

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R. 52, nr 1

3-9

EN

In this study experimental and modeling investigations of a gasoline HCCI engine with internal gas recirculation have been presented. Experimental measurements enabled identification of attainable range of valvetrain settings and air excess coefficient that allows a realization of the HCCI combustion. Factors determining the charge exchange process and the resulting in-cylinder temperature were specified based on computational analysis.

PL

W pracy przedstawiono wyniki badań eksperymentalnych i modelowych procesu roboczego benzynowego silnika HCCI z wewnętrzną recyrkulacją spalin. Na podstawie wyników badań eksperymentalnych określono zakres faz rozrządu oraz współczynnika nadmiaru powietrza, w którym możliwa jest realizacja procesu HCCI. Przeprowadzone badania symulacyjne pozwoliły na zidentyfikowanie czynników kształtujących przebieg wymiany ładunku oraz temperaturę w cylindrze.

2

Increase of high load limit in a gasoline HCCI engine

Hunicz J., Kordos P., Gęca M.

Journal of KONES

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2012

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Vol. 19, No. 4

231-238

EN

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.

3

A study of charge exchange in a residual-effected HCCI gasoline engine

Hunicz J.

Silniki Spalinowe

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2011

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R. 50, nr 2

25-34

EN

An in-cylinder charge exchange process in a gasoline homogeneous charge compression ignition (HCCI) engine operated in a negative valve overlap (NVO) mode was studied. Research was performed using a single-cylinder research engine with fully variable valve actuation. Combination of in-cylinder pressure traces processing and fluid flow model enables cycle-by-cycle analysis of charge composition and temperature. It allows forecasting of in cylinder pressure volume and temperature-volume histories and can be used for physical-based engine control. In this paper influence of valves timings and valves lifts on the gas exchange process was analyzed. Special attention was paid to the effects of backflows of the in cylinder charge to an intake port.

PL

W artykule przedstawiono wyniki analizy procesu wymiany ładunku w benzynowym silniku HCCI (ang. Homogeneous charge compression ignition) działającym z ujemnym współotwarciem zaworów. Badania eksperymentalne zostały przeprowadzone na jednocylindrowym silniku badawczym wyposażonym w układ zmiany faz rozrządu i wzniosu zaworów. Połączenie analizy ciśnienia indykowanego w cylindrze i modelu przepływu czynnika roboczego pozwala na określanie składu oraz temperatury czynnika w cylindrze z rozdzielczością cyklową. Dzięki temu możliwe jest przewidywanie przebiegów krzywych temperatury i ciśnienia sprężania, co może być wykorzystane do sterowania silnika w oparciu o model fizyczny. W niniejszej pracy dokonano analizy wpływu zmiennych faz rozrządu i zmiennego wzniosu zaworów na proces wymiany ładunku. Szczególną uwagę zwrócono na efekty przepływów zwrotnych z cylindra do kanału dolotowego.

4

Combustion control in gasoline HCCI engine with direct fuel injection and exhaust gas trapping

Hunicz J.

Journal of KONES

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2010

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Vol. 17, No. 2

137-144

EN

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.