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Assessment of possible use of the ionization signal for the combustion process diagnostics in a spark-ignition combustion engine powered by natural gas

Fiedkiewicz Ł., Pielecha I.

Eksploatacja i Niezawodność

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2018

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Vol. 20, no. 4

630--637

EN

The ionization signal, which is a result the presence of ions and electrons in the cylinder space of the internal combustion engine, is affected by many factors, including: temperature, pressure, fuel mixture composition, fuel type, presence of exhaust gases and others. The shape of the signal changes to a large extent from cycle to cycle, which indicates the stochastics of the combustion process. Nevertheless, its analysis provides a lot of useful information, such as the location of the maximum pressure or the maximum heat release rate. Using these signals allows supplementing the limited engine control systems of the combustion process in internal combustion engines. The paper presents a comparative analysis of the gas ionization current signal in the cylinder and the variable pressure at fixed operating points of a single-cylinder, four-stroke engine powered by natural gas. The analysis allowed to determine the relationship between the positions of the maximum thermal ionization signal value and of the maximum combustion pressure value. Additionally the relationship between the position of the maximum thermal fraction derivative and the maximum heat release rate was established.

PL

Sygnał jonizacji wynikający z obecności jonów oraz elektronów w przestrzeni cylindra silnika spalinowego jest składową wielu czynników, między innymi: temperatury, ciśnienia, składu mieszanki, rodzaju paliwa, obecności reszty spalin oraz innych. Kształt sygnału zmienia się w znacznym stopniu z cyklu na cykl, co świadczy o stochastyce procesu spalania. Mimo tego, jego analiza dostarcza wielu przydatnych informacji, takich jak położenie maksymalnego ciśnienia czy maksymalnej szybkości wywiązywania się ciepła. Ich wykorzystanie pozwala uzupełnić ograniczone systemy kontroli procesu spalania w silnikach spalinowych. W artykule przedstawiono analizę porównawczą sygnału prądu jonizacji gazów w cylindrze oraz ciśnienia szybkozmiennego przy ustalonych punktach pracy jednocylindrowego, czterosuwowego silnika zasilanego gazem ziemnym. W wyniku analizy uzyskano zależność położenia maksymalnej wartości sygnału jonizacji termicznej od położenia maksymalnej wartości ciśnienia spalania, uzależniono również położenie maksimum pochodnej członu termicznego od położenia maksimum szybkości wywiązywania się ciepła.

2

Optical analysis of the gas flame development in a RCM using a high-power ignition system

Fiedkiewicz Ł., Pielecha I.

Combustion Engines

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2018

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R. 57, nr 2

47--54

EN

The combustion process quality is determined by several factors: the composition of the fuel-air mixture in the vicinity of the spark plug and the discharge conditions on the spark plug. This article assesses a high-power ignition system using optical gas flame propagation analyzes. The tests were carried out in a rapid compression machine, using a fast camera for filming. The spark plug discharge quality assessment was determined indirectly by the flame propagation conditions after the ignition of the mixture (during methane combustion). The size of the flame surface and the rate of its change were assumed as a comparative criterion. It has been found that when using an ignition system with high discharge power the rate of flame development is 14% higher with respect to conventional ignition systems. In addition, the shorter development time of the early flame phase after discharge when using the new ignition system was confirmed. Based on the obtained test results and analyzes, modifications of engine operation settings were indicated, resulting from the use of a high discharge power system.

3

Use of the gas ionization signal for combustion process diagnostics in the cylinder of a spark ignition engine

Fiedkiewicz Ł., Pielecha I., Wisłocki K.

Combustion Engines

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2017

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R. 56, nr 4

196--200

EN

The running diagnostics of the combustion process in an internal combustion engine is essential for increasing its efficiency and to improving its performance indicators. The modern diagnostics of this process no longer concerns only measurements of fast-changing thermodynamic variables, but also measurements of other parameters allowing for its evaluation. The use of electrical or optical methods in diagnostics enables the evaluation of local process parameters, such as occurrence of the flame and its temperature distribution. Actually, there are some new methods under investigation which are proposed for this kind of diagnostic. This article focuses on demonstrating the potential for using an electric signal from the gas ionization to estimate the maximum combustion pressure in a cylinder of an SI engine. This is a comparative analysis of the gas ionization current signal in the cylinder and the fast-changing pressure at fixed operating points of a 4-stroke natural gas powered engine. The study was carried out on a one-cylinder 4-stroke SI engine equipped with a cylinder pressure recording system and monitoring of the cylinder ionization current using appropriate measuring systems. The influence of engine operating conditions on the ability to determine cylinder pressure based on the ionization current signal was analyzed. This impact assessment was analyzed statistically and a strong correlation was found between the analyzed signals. The obtained results point in the potential direction of development of this type of measuring system.

4

The influence of the ignition system characteristic on the two-stroke engine operating conditions

Fiedkiewicz Ł., Cieślik W., Pielecha I.

Journal of Mechanical and Transport Engineering

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2016

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Vol. 68, No. 4

5--15

EN

This paper presents an indicator analysis of the impact of the characteristics of an electronic ignition system on the operating conditions of a two-stroke spark ignition engine. The tests were carried out on a single-cylinder two-stroke engine equipped with a combustion pressure sensor using the apparatus for recording fast-varying signals. The influence of changes of the ignition angle of advance at constant engine speeds on the engine operating indicators was analysed. The assessment of the impact of the changes to the settings of the ignition system was analysed in terms of thermodynamic conditions: combustion pressure and average effective pressure. It was found that the ignition angle of advance has positive influence on engine operating conditions and uniformity of engine operation. As a measure of non-uniformity of engine operation were accepted the coefficient of variation of the engine speed and the mean indicated pressure. It was indicated that, along with the ignition angle of advance, the indicators of two-stroke engine operation also increase with simulta-neous increase in the non-uniformity of engine operation.

PL

W artykule przedstawiono analizę indykatorową wpływu charakterystyki elektronicznego układu zapłonowego na warunki pracy silnika dwusuwowego o zapłonie iskrowym. Badania prowadzono na jednocylindrowym silniku dwusuwowym wyposażonym w czujnik ciśnienia spalania z wykorzystaniem aparatury do rejestracji sygnałów szybkozmiennych. Analizie poddano wpływ zmiany kąta wyprzedzenia zapłonu przy ustalonych prędkościach obrotowych silnika na wskaźniki jego pracy. Ocenę wpływu zmian nastaw układu zapłonowego analizowano w aspekcie warunków termodynamicznych: ciśnienia spalania oraz średniego ciśnienia użytecznego. Stwierdzono pozytywny wpływ wyprzedzenia zapłonu na warunki pracy silnika oraz na jego równomierność pracy. Jako miarę nierównomierności jego pracy przyjęto współczynnik zmienności prędkości obrotowej i średniego ciśnienia indykowanego. Wykazano, że wraz z wyprzedzeniem zapłonu zwiększają się wskaźniki pracy silnika dwusuwowego z jednoczesnym zwiększeniem nierównomierności jego pracy.