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1

Lean-burn combustion systems in spark ignitron engines: advantages and limitations

Gorczakowski A., Jarosiński J.

Journal of KONES

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2008

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Vol. 15, No. 2

97-102

EN

Spark-ignited internal combustion engines are in the use for over130 years (first example was presented by Otto in 1876). The engine development is directed to more power, better efficiency and lower emissions. Mixture formation and in-cylinder motion are the main parameters of the combustion process improvement. One of the effective methods of engine development is lean combustion. Application of lean-burn combustion systems in spark ignitron engines has been proposed many times. Such systems have several important advantages in comparison with conventional systems. Lean-burn combustion makes possible engine operation at high compression ratio, equivalent to high thermal efficiency and at low emission of toxic components of the combustion gases. Lean-burn combustion is also a subject of serious limitations, requiring remedial steps. General limitations are introduced by a fall of the reaction rate, equivalent to increased time of combustion. Lean-burn combustion introduces also changes to flame structure: it contributes with increased flame thickness and with a rise of quenching distance. These changes influence limit conditions of spark ignition. The only solution omitting this threat might be obtained by replacing of a spark ignition by another ignition system or by application of a spark ignition system with increased distance between electrodes and with much higher ignition energy. Typical solutions rationalizing lean-burn combustion in engines are discussed in the paper and some limit conditions highlighted..

2

High compression ratio engine with high-octane fuel supply

Malewicz K., Hetmańczyk I., Mamala J., Borecki D.

Silniki Spalinowe

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2007

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R. 46, nr SC1

61-65

EN

Essence of engine's modification is higher compression ratio obtain thanks to changing of combustion chamber volume. Fuel circuit has possibility to parallel supply base fuel (gasoline) and high-octane fuel. High-octane fuel is use only in transient states which risk of knock combustion is much higher, so time when engine is supplied by high-octane fuel is strongly shorter than time of work with base fuel. High-octane fuel consumption is reasonably low in relation to energetic efficiency. Main part of the system is electronic control unit (ECU) which allows undertaking decisions which kind of fuel is necessary to supply the engine. Principal task of ECU is knock combustion control. Suggested modification thanks to simple construction, low weight and higher dynamic parameters could be use in existing powertrains.

3

High compression ratio engine with dual fuel supply

Malewicz K., Jantos J., Hetmańczyk I., Mamala J., Augustynowicz A.

Journal of KONES

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2007

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Vol. 14, No. 3

371-376

PL

W artykule przedstawiono aspekty zastosowania mechatronicznego systemu zarządzania układami zasilania dwupaliwowego silnika spalinowego o zapłonie iskrowym i stałym zwiększonym stopniu sprężania. Nadrzędnym celem systemu, w tak zmodyfikowanym silniku, jest identyfikacja i zapobieganie możliwemu do wystąpienia procesowi spalania stukowego w warunkach przejściowych oraz pełnego obciążenia. Synteza algorytmu sterowania wymusza traktowanie sygnałów (m.in. Spalania stukowego, prędkości obrotowej i podciśnienia w kolektorze dolotowym) jako zmiennych sterujących nie tylko wyprzedzeniem zapłonu, ale priorytetowo okresową potrzebą zasilania paliwem, lub mieszaniną paliw, o wyższej wartości liczby oktanowej. Dla realizacji koncepcji układ zasilania silnika został zmodernizowany tak, aby istniała możliwość równoczesnego zasilania zarówno paliwem podstawowym, jak i paliwem o zwiększonej liczbie oktanowej, przy zachowaniu stechiometrii spalania. Paliwo o zwiększonej liczbie oktanowej w przedmiotowym silniku jest dozowane indywidualnie na każdy kanał dolotowy, za pomocą zaworu czterodrożnego sterowanego silnikiem krokowym w pętli sprzężenia zwrotnego. Najważniejszym elementem układu zasilania, jest programowalny sterownik Mixed Fuel, zarządzający, kiedy i w jakich warunkach silnik ma być zasilany dodatkowym paliwem o zwiększonej liczbie oktanowej. W wielu ośrodkach naukowo-badawczych na świecie (FEV, SAAB) prowadzone są badania nad rozwiązaniem tego problemu. Jednak skuteczne rozwiązanie musi spełniać szereg warunków, m.in. Technologicznych i ekonomicznych związanych z prostą konstrukcją oraz niskimi kosztami eksploatacji. W artykule przeanalizowano konstrukcję układu zasilania dwupaliwowego doprężonego silnika spalinowego o zapłonie iskrowym oraz przedstawiono wyniki wstępnych badań.

EN

Aspects of using a mechatronic system that regulates supply systems in a dual-fuel combustion engine of spark ignition and constant high compression ratio, were presented in the hereby article. A major aim of the system in such a modified engine is to identify and prevent a potential knock combustion process in transitory and full load conditions. Synthesis of a controlling algorithm imposes treating signals (among others knock combustion, rotational speed and manifold air pressure) as variables that control not only ignition delay but, as a priority, temporary necessity of supply with fuel or fuel mixture of higher octane number. In order to effect this concept, the engine supply system was modernized in such a way that simultaneous supply with both basic fuel and fuel of high-octane number was made possible. Still, combustion stoichiometry was preserved. High-octane fuel in the subject engine is dispensed individually at every manifold with the use of a four-way valve controlled with a step motor position in a feedback loop. A programmable Mixed Fuel driver is the most important element of the supply system as it regulates when and in which conditions the engine is supplied with additional high-octane fuel. Many scientific and research centres worldwide (FEV, SAAB) have conducted tests to solve the problem. However, an effective solution must fulfil several conditions, such as technological and economical, connected with simple structure and low operation costs. Structure of the supply system in a dual-fuel compressed combustion engine of spark ignition was presented in the article. Moreover, initial tests results were presented along.