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1

Heat release in a direct fuel injection SI two-stroke engine

Mitaniec W., Forma M.

Silniki Spalinowe

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2011

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R. 50, nr 3

EN

The paper presents a new method of determination of heat release rate on the base of experimental test in a two-stroke engine with direct gasoline injection. The target of the work was achieving of information about implementation of approximated Viebe function in mathematical models and simulation computer programs of a combustion process in spark ignition two-stroke engine with direct fuel injection due to the lack of such data in the literature. The energy balance equations were derived in oeder todetermine of heat release rate on the base of pressure measurements in the cylinder and change of the cylinder volume in the function of angle of crankshaft rotation. The paper presents several examples of heat release and approximate function, for which variable coefficients of Viebe function were determined for certain rotational speeds at wide opening throttle. Pressure measurements were carried out on the engine Robin EC12 wit capacity 115 cm3. Determination of heat release and burned fuel rate was calculated by means of own computer program. The paper also presents the method of determination of variable specific heat coefficients in the function of crankshaft rotation, which are also used in modeling of the engine processes.

PL

Artykuł przedstawia nowy sposób określenia wydzielania się ciepła na podstawie badań eksperymentalnych pomiaru ciśnień w dwusuwowym silniku ZI z bezpośrednim wtryskiem benzyny. Celem pracy było otrzymanie informacji o implementacji aproksymowanej funkcji Wiebe w modelach matematycznych i programach symulacyjnych procesu spalania w dwusuwowym silniku o zapłonie iskrowym z bezpośrednim wtryskiem paliwa z powodu braku takich danych w literaturze. Wyprowadzono równania bilansu energii celem określenia wydzielania się ciepła na podstawie pomiarów ciśnienia oraz zmiany objętości cylindra w funkcji kąta obrotu wału korbowego. Przedstawiono kilka przykładów wydzielania się ciepła oraz aproksymowanych funkcji, dla których określono zmienne współczynniki Wiebe dla wybranych prędkości obrotowych i pełnego otwarcia przepustnicy. Badania pomiaru ciśnień w cylindrze zostały przeprowadzone na silniku Robin EC12 o pojemności skokowej 115 cm3. Określenie wydzielania się ciepła i stopnia spalania paliwa było obliczane za pomocą własnego programu komputerowego. Artykuł przedstawia również sposób określenia zmiennych współczynników ciepeł właściwych w funkcji obrotu wału korbowego, które również są wykorzystywane w modelowaniu procesów silnikowych.

2

Experimental investigations in direct injected SI two-stroke engine

Mitianiec W., Forma M., Rodak Ł.

Journal of KONES

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2010

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Vol. 17, No. 2

335-342

EN

The paper presents the latest experimental results of smali power two-stroke engine with electronic controlled high pressure direct fuel injection. The work is one of the first solutions in such engines in Poland and was provided on industrial engine with capacity 115 cm3. A special experimental eąuipment and electronic control of fuel dose and injection phases enables to obtain a big decrease of specific fuel consumption and exhaust gas emission, particularly hydrocarbons with the same level of torque. Applying of direct injection in small power two-stroke engine gives possibility tofulfil exhaust emission reguirements. The paper presents the experimental stand and fuel injection system with results of main engine parameters and emission of chosen chemical components. The configuration of injection system was designed on the basis of previous simulation test in GT-Power and KIVA3V. Earlier fuel injection influences on better evaporation and mixture formation with small stratification, which enables full mixture combustion. Direct fuel injection in two-stroke engine decreases hydrocarbon emission 10 times and specific fuel consumption about 30% in comparison to carburetted engine. Exhaust gas emission is on level off our stroke engines with low emission of NOx. The engine was equipped with conventional automotive injector, which was not suited to small cylinder capacity. . On the basis of the simulations and experimental tests a main conclusion can be drawn, that the spray guided direct fuel injection is a way to obtain cleaner and more effective two-stroke engine for small power units.

3

Gasoline Mixture Combustion in Direct Fuel Injection SI Two-Stroke Engine

Mitianiec W., Rodak Ł., Forma M.

Archivum Combustionis

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2010

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Vol. 30 nr 4

377-397

EN

Process of gasoline mixture combustion in two-stroke engines is much more complicated than in four stroke engines. In order to decrease fuel consumption and exhaust gas emission, particularly hydrocarbons, two-stroke engines should have direct fuel injection systems. The paper presents results of both simulation and experimental tests on a small power gasoline two-stroke engine. The special high pressure injection system was elaborated in Cracow University of Technology for engine with capacity 115 cm3. The most important factor in such engine is small time for fuel evaporation and obtaining a homogeneous mixture in the combustion chamber. The gas flow in the cylinder (tumble and swirl) causes a certain deviation of fuel stream during injection and therefore location of the injector has big significance on the combustion process. The paper shows results of fuel distribution in the cylinder for different crank angles obtained from spatial simulation (KIVA3V) and propagation of the flame during combustion process. Experimental work was carried out on the engine in order to determine influence of injection parameters on engine work and combustion process. On the basis of pressure traces at different loads and rotational speeds heat release rates were calculated and Vibe functions were found. The paper presents the engine experimental stand and results of decreasing of important exhaust gases components at the same engine working parameters as in carburetted engine.

4

Simulation and experimental test of spray guided direct fuel injection in a two-stroke engine

Mitaniec W., Forma M.

Silniki Spalinowe

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2009

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R. 48, SC2

105--112

EN

The paper shows interaction between the scavenge air and fuel jet from the injector located in the cylinder head, which can induce the small size of fuel droplets and fast evaporation. The paper presents the computational results of fuel mixture formation and combustion process in direct fuel injection two-stroke engine with capacity 115 cm3. The simulation was carried out by use KIVA code with assumption of initial parameters from the experiment of the carbureted engine. The paper shows phases of mixture formation, combustion and concentration of the combustion product in the cylinder The experimental test carried out on the same engine equipped with electronic control direct fuel injection system shows the preliminary results of engine parameters and emission of pollutants.

PL

Artykuł pokazuje interakcję między strumieniem powietrza przepłukujacego i strumieniem paliwa z wtryskiwacza ulokowanego w głowicy cylindra, który może powodowac małe krople paliwa i ich szybkie odparowanie. Publikacja przedstawia wyniki obliczeń formowania mieszanki paliwowo-powietrznej i proces spalania w silniku dwusuwowym o pojemności skokowej 115 cm3 z bezpośrednim wtryskiem paliwa. Symulacje zostały przeprowadzone w programie KIVA przy załozeniu parametrów początkowych z badań silnika gaźnikowego. W pracy pokazano fazy formowania mieszanki, proces spalania oraz udział masowy produktów spalania w cylindrze. Artykuł ukazuje również wstępne parametry robocze silnika wyposażonego w elektroniczny system bezpośredniego wtrysku paliwa na podstawie badań eksperymentalnych.

5

Analysis of direct fuel injection in a small power two-stroke engine

Mitianiec W., Forma M.

Journal of KONES

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2009

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Vol. 16, No. 2

337-347

EN

Small power two-stroke engines can be competitive in regard of work parameters and pollutants emission in relation to four-stroke engines at some modifications, particularly changing of fuelling system. The paper presents a modifted air-assisted direct fuel injection in a two-stroke engine, which changes propagation of fuel jet in the combustion chamber. The main problem of mixture formation is short time for fuel evaporation after injection which should begin after closing of the exhaust port. The paper shows interaction between the scavenge air, additional air stream and fuel jet from the injector located in the cylinder head, which can induce the small size of fuel droplets and fast evaporation. The computational results of fuel mixture formation and combustion process in direct fuel injection two-stroke engine Robin EC-12 with capacity 115 cm3 are presented. The simulation was carried out by use KIVA code with assumption of initial parameters from the experimental tests on the carburetted engine. Setting of the injector in a regard of the cylinder head decides of fuel motion and evaporation in the combustion chamber. Air-assisted fuel injection influences on higher mixing of fuel and better combustion than by using DFI system. The paper shows phases of mixture formation, combustion and concentration of the combustion product in the cylinder with additional air stream. Spray guided high pressure direct injection system in SI two-stroke engine enables fulfil the restrictions of gas emission of one-wheeler vehicles and small power units.

6

Formation of fuel mixture in a SI two-stroke engine with direct fuel injection

Mitianiec W., Forma M.

Journal of KONES

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2008

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Vol. 15, No. 2

329-337

EN

Decreasing of fuel consumption and high hydrocarbon emission in a SI two-stroke engine applied in motorcycles, scooters and small power units is possible by change of fuelling system on direct fuel injection. The main problem of mixture formation is short time for fuel evaporation after injection which should begin after closing of the exhaust port. However well interaction between the scavenge air and fuel jet from the injector located in the cylinder head can induce the small size of fuel droplets and fast evaporation. The paper presents the computational results of fuel mixture formation and combustion process in direct fuel injection two-stroke engine Robin EC-12 with capacity 115 cm3. The simulation was carried out by use KIVA code with assumption of initial parameters from the experiment of the carbureted engine. Earlier fuel injection influences on better evaporation and mixture formation with small stratification, which enables full mixture combustion. The paper shows phases of mixture formation, combustion and concentration of the combustion product in the cylinder. Spray guided high pressure direct injection system in SI two-stroke engine enables fulfill the restrictions of gas emission of one-wheeler vehicles and small power units. New modern two-stroke engines and environmental protection require new fuelling systems and one of the most promising methods is direct spray guided fuel injection. Many work were done in this subject, however still there is no better option for small power two-stroke engines.

7

Mixture formation at spray guided direct injection in SI two-stroke engine

Mitianiec W., Forma M.

Czasopismo Techniczne. Mechanika

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2008

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R. 105, z. 7-M

115-127

EN

In the paper the top direct injection on the mixture formation is considered. Modelling of physics process during injection was carried out with assumption of the exact future experimental set-up. The hemisphere combustion chamber causes additional motion of gas and fuel before ignition. A difference approximation of differential equations of the injection and combustion was used for solving the problem by KIVA program. Velocity of gas influences on the distribution of liquid and vapour phases of injected fuel. In the paper: distribution of gaseous phase of fuel, gas temperature, vectors of charge velocity and vapour mass ratio for top and side fuel injection systems were shown.

PL

W artykule rozważano proces bezpośredniego wtrysku paliwa. Modelownie procesu fizycznego wtrysku paliwa zostało przeprowadzone przy założeniu przyszłego badawczego silnika. Półkulista komora spalania powoduje dodatkowy ruch gazu i paliwa przed zapłonem. Do rozwiązania tego problemu przeprowadzono aproksymację różnicową równań różniczkowych procesu wtrysku i spalania za pomocą programu KIVA. Prędkość gazu wpływa na rozprzestrzenianie się fazy ciekłej i parowej wtryskiwanego paliwa. W artykule pokazano rozkład par paliwa, temperaturę gazu, wektory prędkości ładunku i udział masowy par paliwa przy głowicowym i bocznym wtrysku paliwa.