Wyniki wyszukiwania - BazTech

1

Modification of four-stroke engine for operation in two-stroke cycle for automotive application

Mitaniec W., Buczek K.

Combustion Engines

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2015

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R. 54, nr 3

3--12

EN

The main disadvantages of two-stroke engines such a big fuel consumption and big emission of hydrocarbons or carbon monoxide can be reduced by new proposal of design of two stroke engine based on four stroke engines. The paper describes the operation of high supercharged spark ignition overhead poppet valve two-stroke engine, which enables to achieve higher total efficiency and exhaust gas emission comparable to four-stroke engines. The work of such engines is possible by proper choice of valve timings, geometrical parameters of inlet and outlet ducts and charge pressure. The engine has to be equipped with direct fuel injection system enabling lower emission of pollutants. The work is based on theoretical considerations and engine parameters are determined on the simulation process by use GT-Power program and CFD program for different engine configurations. The initial results included in the paper show influence of valve timing on engine work parameters and predicted exhaust gas emission. The simulation results show that the nitrogen oxides are considerably reduced in comparison to four-stroke engines because of higher internal exhaust gas recirculation. The innovation of this proposal is applying of variable valve timing with turbocharging system in the two-stroke engine and obtaining a significant downsizing effect. The conclusions shows the possibilities of applying two-stroke poppet valve engine as a power unit for transportation means with higher total efficiency than traditional engines with possible change of engine operation in two modes: two- and four stroke cycles.

PL

Główne wady silników dwusuwowych, takie jak duże zużycie paliwa i duża emisja węglowodorów oraz tlenku węgla mogą być wyeliminowane przez propozycję nowej konstrukcji silnika 2-suwowego opartego na silniku 4-suwowym. W artykule przedstawiono pracę wysoko doładowanego górnozaworowego silnika 2-suwowego, który umożliwia uzyskanie większej sprawności niż silnika 4-suwowego przy utrzymaniu emisji szkodliwych składników spalin na poziomie silników 4-suwowych. Silnik jest wyposażony w bezpośredni wtrysk paliwa umożliwiający mniejszą emisję szkodliwych składników spalin. Przedstawiono osiągi silnika, które określono na podstawie symulacji w programie GT-Power oraz przy użyciu programu CFD. Silnik został zmodyfikowany przez zmianę systemu zaworowego i faz rozrządu dla pracy w cyklu 2-suwowym. Zaprezentowano zmiany zachodzące w parametrach termodynamicznych cylindra w czasie wymiany ładunku dla wersji 2- i 4-suwowej. Proces spalania był modelowany za pomocą prostych reakcji kinetycznych dla węglowodorów i tlenków azotu oraz reakcji dysocjacji. Wyniki symulacji wskazują, że emisja tlenków azotu jest znacznie mniejsza w porównaniu z silnikiem 4-suwowym z powodu dużej wewnętrznej recyrkulacji spalin. Innowacją w proponowanym silniku dwusuwowym jest zmienność faz rozrządu z doładowaniem turbosprężarkowym i uzyskanie znacznego zmniejszenia gabarytów silnika (downsizing). Podano także możliwość zastosowania górnozaworowego silnika 2-suwowego jako jednostki napędowej dla środków transportu o większej sprawności niż tradycyjne silniki, z możliwością pracy zarówno w cyklu 2-suwowym, jak i 4-suwowym.

2

Study of combustion and pneumatic spark ignition engine

Mitianiec W., Wiatrak W.

Journal of KONES

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2010

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Vol. 17, No. 1

283-290

EN

he paper describes the work of high speed spark ignition engine with additional high pressure air injection during combustion process. The analyzed conception of combustion and pneumatic engine is based on the European patent EPO - EP2 103777 A2 and polish announcement UP RP P-387992. The paper presents the results of theoretical and numerical investigations for different analyzed control parameters of the injection dose of air with comparison of work parameters for standard and modified engine. Additional post air injection enables achieving higher expansion pressure and additional oxygen for better fuel combustion. At proper air dose the charge temperature slightly decreases, which enables applying of a cheaper turbocharger in such engine in regard of thermal resistance of materials. The engine is equipped with electronic control system of air injection and directfuel injection. The paper shows an increase of dynamic engine performance for constant timings and pressure of air injection and variations of engine work in comparison to standard engine. Additionally the paper shows possible energy recovery system of such engine in the car. The conception is a certain input for "downsizing" of engines and reduction of exhaust emission. The results presented in the paper were obtained from computer programs based on prepared mathematical model.

3

Gas exchange in valved two-stroke SI engine

Buczek K., Mitianiec W.

Journal of KONES

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2010

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Vol. 17, No. 1

73-80

EN

The paper describes the work of high speed charged spark ignition overhead poppet valve two-stroke engine, which enables to achieve higher total efficiency and exhaust gas emission comparable to four-stroke engines. The work of such engines is possible by proper choice ofvalve timings, geometrical parameters of inlet, outlet ducts and charge pressure. The engine has to be equipped with direct fuel injection system enabling lower emission of pollutants. The work is based on theoretical considerations performed in GT-Power in previous authors' research and carried out in CFD code (KIVA 3 V) for different engine configurations. The initial results included in the paper show influence of inlet port geometry and charge pressure on engine scavenging process. Additionally, optimum fuel spray injector position was considered in order to obtain proper fuel vaporization and avoid significant wall-wetting. The simulation results show that the nitrogen oxides arę considerably reduced in comparison to four-stroke engines because ofhigher internal exhaust gas recirculation. The innovation of this proposal is applying of poppet intake and exhaust valves with turbocharging in the two-stroke engine and obtaining a significant downsizing effect. The conclusion shows the possibilities of proper gas exchange process in this type of two-stroke engine and thus, the feasibility of its application as a power unii for transportation means with higher total efficiency than traditional engines with possible change of engine work in two modes: two- and four-stroke cycles.

4

A new approach in development of two-stroke engines

Mitaniec W., Buczek K.

Silniki Spalinowe

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2009

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R. 48, SC2

99--104

EN

The paper describes the work of high speed charged spark ignition overhead poppet valve twostroke engine, which enables to achieve higher total efficiency and exhaust gas emission comparable to four stroke engines. The outflow of exhaust gases in this type of engine is partially forced by pressure of inlet air. This publication presents the engine, which has to be equipped with direct fuel injection system enabling lower emission of pollutants. The work is based on theoretical consideration and engine parameters are determined on the simulation process by use of GT-Power program for different engine configurations. The obtained results included in the paper show influence of valve timing on engine work parameters such as BMEP and BSFC. The conclusion points out the possibility of applying two-stroke poppet valve engine as a power unit for transportation means with higher total efficiency as traditional engines.

PL

Artykuł zawiera opis pracy szybkoobrotowego dwusuwowego silnika o zapłonie iskrowym wyposażonego w zawory grzybkowe umieszczone w głowicy, umożliwiającego uzyskanie wysokiej sprawności ogólnej silnika oraz emisji gazów wylotowych porównywalnej z silnikiem czterosuwowym. Wypływ gazów spalinowych tego typu silnika spowodowany jest częściowo przez ciśnienie gazów w układzie dolotowym. Zaprezentowany silnik, ze względu na obniżenie emisji toksycznych gazów, musi być wyposażony we wtrysk bezpośredni. Praca została oparta na rozważaniach teoretycznych, gdzie parametry pracy silnika zostały wyznaczone w programie GT-Power dla różnych konfiguracji silnika. Otrzymane wyniki zawarte w pracy pokazują wpływ czasów otwarcia zaworów na takie wielkości jak średnie ciśnienie efektywne czy jednostkowe zużycie paliwa. Uzyskane wnioski wskazują na możliwość zastosowania tego typu dwusuwowego silnika jako jednostki napędowej środków transportu o wyższej sprawności ogólnej silnika.

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

A valved two stroke engine as a new power source

Mitianiec W., Buczek K.

Journal of KONES

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2009

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Vol. 16, No. 3

259-268

EN

The present work defines main conception of modern, efficient and ecologic two-stroke engine. It indicates the scope of necessary modifications that have to be made in typical four-stroke engine to prepare it to work in two-stroke mode. Taking into account some limitations (especially in valve train design) authors performed several analyzes in order to check the possibility of proper scavenging process and obtain main engine characteristics. The paper contains description of simulation approach and selected mathematical models that was applied in carried over analyzes. The results of foregoing simulations, which were obtain taking advantage of GT-Power software should be considered as preliminary since several parameters have to be defined during research and 3D simulations. In order to expose advantages of modern two-stroke engine a simple comparison of it and its predecessor was performed taking into consideration BSFC maps. The objects of simulation were fluid flow, scavenging and combustion. This comparison indicates that proposed two-stroke engine achieve significantly less break specific fuel consumption (up to 27 g/kWh drop). Paper presents diagram of new type two-stroke engine with poppet valves, which is probably the most feasible layout of two-stroke engine, and GT-Power model of simulated single-cylinder engine based on four-stroke single cylinder engine.