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1

Relations between ion signal and flame propagation in cylinder of a rapid compression machine

Fiedkiewicz Łukasz, Pielecha Ireneusz

Combustion Engines

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2019

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R. 58, nr 4

264--268

EN

Internal combustion engine diagnostics using traditional methods of cylinder pressure signal processing limits the amount of information available about the combustion process. It is necessary to conduct research in order to obtain more precise information - in-creasing the combustion process diagnosis potential. One such suggestion is the use of an ionization signal and an attempt to link it to the flame development during combustion of gaseous fuels. The article attempts to identify such a relationship using a rapid compression machine due to optical access it provides to the combustion chamber. As a result of the research, the relationships between the ionization voltage (chemical and thermal) of the first combustion phase and the corresponding flame development rates were determined. A relatively high coefficient of determination value was obtained for both relations, which indicates the possibility of obtaining diagnostic information about the combustion process from the ionization signal.

2

CFD study of the Effect of Piston Crevice Volume on the Temperature Distribution in a Rapid Compression Machine

Nyong Oku E., Ebieto Celestine, Bassey Ene Ekpo, Azorshubel Ikem

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 1

46--51

EN

One of the conditions for controlling the aerodynamics in the reaction chamber is designing a crevice volume on the surface of the piston head. The importance of the crevice volume is to contain the cool boundary layers generated as a resulting of the moving reactor piston. However, this crevice volume consequently drops the end gas pressure and temperature at the end of the stroke. The CFD study of the aerodynamic effect of a piston movement in a reaction chamber was modelled using the commercial code of Ansys Fluent and assuming a 2-Dimensional computational moving mesh. A starting optimal crevice volume of 282 mm3 was used for further optimisation. This resulted in five crevice lengths of 3 mm, 5 mm, 7 mm, 9 mm and 12 mm, respectively. The crevice height of 5 mm was found to improve the compressed gas pressure at the end of the stroke to about 2 bar and temperature about 17.7 K and also maintained a uniform temperature field, while that of 12 mm had the least peak compressed gas pressure. This study investigated the possible means of improving the peak pressure and temperature drop in a rapid compression machine by further optimisation of the crevice volume.

3

Evaluation of mixture swirl in the cylinder chamber in a conceptual system with combustion surrounded by inactive gases

Cieślik W., Pielecha I.

Combustion Engines

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2018

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R. 57, nr 4

40--47

EN

Internal combustion engines have seen a reduction of the dynamics of their efficiency growth in recent years. All kinds of new modifications and changes introduced in this field can only manage changes of engine efficiency at the level of a fraction of a percent. Considering the concept of unification of SI and CI internal combustion engine structures, one can expect to see their efficiency increase by the reduction of losses, whose causes and occurrence is commonly known. The improvement of the combustion system is mainly related to the reduction of thermal losses generated in this process. Therefore, the current issue is the advanced analysis of any possibilities of improving the combustion conditions and more fully understanding the processes that accompany them. The authors of the article see such a possibility in the conceptual control of the combustion process, which aims to obtain a combustible mixture surrounded by nonflammable gases. This way the flame contact with the cylinder walls is limited, which should in turn contribute to reducing the heat exchange with the walls. This research is a continuation of previous research work; current work focuses on determining the actual distribution of gases in the combustion chamber using the advanced shadow photography method. The article specifies the effect of nonflammable gas injection pressure increase on the area of the boundary layer formed between the non-flammable gases and cylinder walls.

4

Design of the rapid compression machines for combustion researches in spark ignition engines

Leżański T., Sęczyk J., Wolański P.

Journal of KONES

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2012

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Vol. 19, No. 4

379-391

EN

The rapid compression machines (RCM) are extensive applied to combustion process researches and mixture process preparation research in the internal combustion engines (ICE). The principal advantage of these arrangements is easy optical access to the inside space of combustion chamber. This enables to observe the course of ignition process and the flame propagation process. There are some RCM designs, which they differ, first of all, the modelling method of piston movement into cylinder. The most known designs use the pneumatic and hydraulic drives. Their concern is that they enable the modelling compression stroke only but combustion is performed in constant volume combustion chamber. It was not relevant for the research of the new combustion system elaborated at Aircraft Engine Department of Warsaw University of Technology (AED). The RCM elaborated at AED has unique form it includes the crank mechanism, speedy operating electromagnetic clutch and flywheel. The applying of this design enables modelling the compression stroke and working stroke (two-stroke from engine cycle). It enables assessment of the system with semi-open combustion chamber what it will be impossible using other RCM designs. The different designs RCM used for combustion research at the research and development centres, on worldwide will be compared with the design of RCM developed at AED. The most known designs of the different RCM were described and the research result examples were given in this paper. The advantages and disadvantages of the different designs were discussed too in this paper.

5

Thermodynamic aspects of combustion in gasoline engines fitted with a multiple fuel injection

Wislocki K., Pielecha I., Maslennikov D., Czajka J.

Journal of KONES

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2011

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Vol. 18, No. 4

543-553

EN

The multiple fuel injection is being applied not only in diesel engines but in direct injection gasoline engines as well. The injection duration in gasoline engines is similar (pressure values at present approx. 20 MPa) to the injection duration of diesel fuel. The methodology and results of the tests related to the fuel dose division and injection strategy on the thermodynamic indexes during the combustion process have been presented in the paper. The tests were performed for several ways of fuel dose division at injection pressures of 5, 10 and 20 MPa (modifying also the time of the injection). The paper presents: state of research on the effects of multiple injection in gasoline engines, research equipment and methodology when applying the Rapid Compression Machine, estimation of the thermodynamic indexes, injection strategies, influence of injection pressure on the thermodynamic indexes, single fuel dose, two-phase fuel injection, three-phase fuel injection, changes in the combustion pressure, changes of the average thermodynamic temperature of the charge in the cylinder, heat release rate, heat release and relative value of the heat used for strategies, the influence of the fuel injection pressure on the course of the combustion in a Rapid Compression Machine including the course of the heat release.

6

The assessment of the usefulness of a Rapid Compression Machine in optical research on the injection and combustion processes of liquid fuels

Wisłocki K., Pielecha I., Czajka J., Maslennikov D., Kaźmierowski J.

Silniki Spalinowe

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2010

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R. 49, nr 4

3-14

EN

In the paper the possibilities of A Rapid Compression Machine in the investigation of the fundamental processes in IC engines have been presented. The test-stand design, principles of its control and basic operational features have been discussed and compared with the parameters of the test facilities of similar type currently in use worldwide. A short evaluation has been performed or its functionality and possibilities of application in the research on thermodynamics or injection and combustion processes. The evaluation pointed to the possibility of variation of the parameters and variables in the RCM. The main parameters and operational indexes of the Test-stand have been presented along with some examples of the achieved results from the investigations of engine internal processes.

PL

W artykule przedstawiono możliwości wykorzystania Maszyny Pojedynczego Cyklu do badania podstawowych procesów silnikowych. Omówiono budowę stanowiska, zasady sterowania jego pracą oraz podstawowe cechy użytkowe, które porównano z innymi urządzeniami tego typu stosowanymi w badaniach światowych. Przeprowadzono krótką ocenę jego funkcjonalności i możliwości prowadzenia badań w zakresie termodynamiki procesów wtrysku i spalania z wykorzystaniem metod indykatorowych oraz badań optycznych wskazując na wariantowania cech konstrukcyjnych oraz parametrów i zmiennych sterujących procesami silnikowymi. Zaprezentowano warunki pracy urządzenia i przedstawiono przykładowe wyniki badań i analiz procesów wewnątrzsilnikowych.

7

Some problems of combustion system operation with semi-open combustion chamber for spark ignition engine

Leżański T., Sęczyk J., Wolański P.

Journal of KONES

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2010

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Vol. 17, No. 4

287-294

EN

The some problems concern of the new combustion system operation with semi open combustion chamber, which can be used in spark ignitions internal combustion engines are presented in this paper. These considerations are based on the visualization research results, with using rapid compression machine (RCM). In this researched combustion system the original combustion chamber was divided by partition in prechamber and main combustion chamber. This division of the original combustion chamber exists only when the piston is close to TDC, for the rest of the cycle the chambers arefully open. Ignition is initiated in the prechamber using electric spark plug, but the mixture in main combustion chamber is ignited by the stream of the burned gases injected from prechamber through the orifice in partition, if the ignition advance angle is correct. If the ignition advance angle is incorrect the mixture from prechamber will be outflowing through the orifice in partition and through the slot which is created between the partition and piston crowns. This last stream is swirled on the partition edge, what causes decrease of the stream speed outflowed from the orifice in partition to main combustion chamber. If the ignition advance angle is too big, then a peak pressure and compression work is very big because the burned gases are compressed instead of the fresh air/fuel mixture. This causes that the effective work is small and combustion efficiency is small.

8

Validation of the Numerical Simulation of Iso-octane Auto-ignition Delay Time in Rapid Compression Machine with the Use of ECFM-3Z (Extended Coherent Flame Model - 3 Zones) Combustion Model Against Experimental Data

Jaworski P., Priesching P., Teodorczyk A., Bandel W.

Archivum Combustionis

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2010

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Vol. 30 nr 1-2

1-14

EN

Nowadays combustion models come up to the requirements of engineers. Numerical simulations show good agreement with experimental results of the compression ignition (CI) and spark ignition (SI) engines. Controlled auto-ignition (CAI) has emerged as one of the most promising engine technologies with the potential to combine fuel efficiency and improved emissions performance. Despite considerable advantages controlling the combustion is still an area of on-going research. The combustion models used for engine simulations are not well prepared and they have to be validated with experimental data. In this paper the first step of setting up of the combustion model is presented with the use of experimental results from three different rapid compression machine (RCM) experiments. That kind of work has to be performed before real engine calculations, to give the brief view on the differences in the experimental and simulation data. Also during this work an improved thermodynamic database for the ECFM-3Z combustion model in the FIRE software was introduced.

9

Using of high speed photography to research of ignition process in SI engines with semi open combustion chamber

Leżanski T., Sęczyk J., Siwiec S., Wolański P.

Journal of KONES

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2009

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Vol. 16, No. 4

277-286

EN

The results of the research into visualisation of the ignition process in a combustion system with divided, semi open combustion chamber, for SI engines are presented in this paper. In this combustion system the original combustion chamber was divided, by partition, into prechamber and the main combustion chamber. Initiation of the ignition had place in the prechamber using electric spark plug. Expected results of the research of this combustion system were: shortening ofcombustion time in all combustion chambers, reduction of exhaust emission and increased engine efficiency. The research was focused on experimental study of flame propagation during ignition and combustion into the prechamber when the point of ignition was placed in the wali of the prechamber opposite to the ońfice in the prechamber, in the middle of the prechamber and in the orifice in the partition. The rapid compression machine (RCM) was used in the experimental research to facilitate visualisation of the process. This high speed Schlieren photography system and high speed pressure measurement system were used to record path of combustion and pressure variation in the combustion chamber. The best results were obtained when the point of ignition was placed at the wali of the prechamber, it was probably caused by flame front turbulisation immediately after ignition initiation. In this case the shortest time of combustion and the highest maximum cycle pressure were achieved resulting in the maximum combustion efficiency and minimum exhaust emission. If the point of ignition was placed in the middle of the prechamber or in the orifice in the partition, immediately after ignition initiation the laminar flame front was observed. This flame front was turbulised after some time from ignition initiation, however, the time to turbulisation was shortened in the case of the ignition in the middle of the prechamber. As a result, the combustion time after ignition initiation in the orifice in the partition was close to one in the original combustion chamber. Pictures in the paper present black-white high speed photography of the flame front development after ignition initiation for different ignition placements and the curves of flame front travel after the ignition.

PL

W publikacji przedstawiono wyniki badań wizualizacyjnych procesu zapłonu w systemie spalania z dzieloną, półotwartą komorą spalania przeznaczonego dla silników o zapłonie iskrowym. System charakteryzuje się podziałem standardowej komory spalania na komorę wstępną i zasadniczą. Inicjacja zapłonu od świecy elektrycznej ma miejsce w komorze wstępnej. Przedmiotem badań był przebieg zapłonu i spalania mieszaniny w komorze wstępnej, w przypadku umieszczenia elektrod świecy zapłonowej: na ściance, w środku komory wstępnej, w otworze w przegrodzie łączącym komorę wstępną z komorą zasadniczą. Badania prowadzono przy zastosowaniu maszyny pojedynczego sprężu co pozwoliło ułatwić wizualizację procesu. Wraz z rejestracją przebiegu spalania na taśmie filmowej rejestrowano przebieg zmian ciśnienia w komorze spalania. Najlepsze efekt uzyskano w przypadku miejsca inicjacji zapłonu na ściance komory wstępnej. Wówczas czas spalania był najkrótszy, ponieważ spalanie miało charakter turbulentny. W przypadku zapłonu w środku komory wstępnej i zapłonu w otworze spalanie, bezpośrednio po zapłonie, miało charakter laminarny i dopiero po pewnym czasie następowała turbulizacja płomienia, z tym, że l w przypadku zapłonu w otworze czas ten był bardzo długi. W efekcie czas spalania, w przypadku zapłonu w otworze, j był bardzo zbliżony do czasu spalania w komorze standardowej. Najkrótsze czasy spalania uzyskiwano w przypadku zapłonu na ściance, co wyraźnie można ocenić na wykresach i fotografiach przebiegu spalania.

10

Research of influence of design parameters on combustion system operation for SI engines

Leżanski T., Sęczyk J., Wolański P.

Journal of KONES

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2009

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Vol. 16, No. 4

265-276

EN

The summary of the investigation performed with a new combustion system with divided semi-open combustion chambers for SI engines while using rapid compression machine (RCM) is presented in this paper. Division of the combustion chamber with partition to the prechamber and the main combustion chamber exists only when the piston is close to the TDC, for the rest of the cycle the chambers are fully open. Variable parameters of the combustion system during the tests were: ratio of the prechamber volume to the sum of the prechamber and main combustion chamber volumes, diameter of the orifice in the partition, point of the ignition and ignition advance angle (ignition timing). Constant parametr es were: RCM speed — 1800 rpm, and stoichometric mixture of air to natural gas- it contained 96% ofmethane. research results show that the ignition advance angle, which ensures the optimal results, has to be adjusted for each configuration of the RCM design parameters. The influence of prechamber volume, orifice diameter, point of ingnition and ignition advance angle on combustion process in the combustion chamber was analysed. If the prechamber volume is too small the energy of the stream is small and the stream has a small range. Its energy is too small to travel through all the main combustion chamber with the speed greater than the combustion speed. The partition orifice diameter influences on the time from the start of the ignition to the beginning of the stream outflow.from prechamber to the main combustion chamber and the stream energy. The biggest influence on stream formation process has the placement of the ignition and the best results are obtained when the ignition occured on the prechamber wall. The high speed Schilieren photographs of the combustion process of the most characteristic cases and of the travel of the flame front curves are shown in this paper. The research results show the direction of the trade - off investigation of commercial SI engine for a wide range of engine speed and loads.

PL

W publikacji podsumowano wyniki badań prowadzonych nad nowym systemem spalania dla silników o zapłonie iskrowym, w którym dokonano podziału standardowej komory spalania na komorę wstępną i komorę zasadniczą. Przy tym podział ten występuje wyraźnie tylko wówczas, kiedy tłok znajduje się w pobliżu GMP. Badania prowadzono przy zastosowaniu maszyny pojedynczego sprężu. Zmiennymi parametrami konstrukcyjnymi były: stosunek objętości komory wstępnej do całkowitej objętości komory spalania, średnica otworu w przegrodzie łączącego komorę wstępną z komorą zasadniczą, miejsce zapłonu. Badania prowadzono przy różnych wartościach kąta wyprzedzenia zapłonu, przy stałej prędkości obrotowej wału korbowego 1800 obr./min. Paliwem była stechiometryczna mieszanina powietrza z gazem ziemnym zawierającym 96% metanu. Wyniki badań wskazują, że dla uzyskania pozytywnego efektu konieczne jest dobranie odpowiedniego kąta wyprzedzenia zapłonu dla każdej konfiguracji parametrów konstrukcyjnych (objętość komory wstępnej, średnica otworu w przegrodzie, miejsce zapłonu). W pracy przeanalizowano wypływ: stosunku objętości komór spalania wstępnej do zasadniczej, średnicy otworu w przegrodzie oraz miejsca zapłonu na przebieg spalania i stwierdzono, że przy zbyt małej objętości komory spalania energia strugi jest zbyt mała, aby przemieścić się z dużą prędkością przez całą zasadniczą komorę spalania, większą niż prędkość spalania w komorze standardowej. Średnica otworu w przegrodzie wpływa zarówno na czas od początku zapłonu do początku wypływu jak i energię strugi. Miejsce zapłonu najsilniej wpływa na proces tworzenia się strugi. W publikacji przedstawiono fotografie z przebiegiem spalania w najbardziej charakterystycznych przypadkach oraz wykresy przemieszczeń czoła płomienia w przypadku różnych fotografii parametrów badań

11

Investigation of combustion process in rapid compression machine using high speed schlieren photography

Glinka W., Leżański T., Wolański P.

Journal of KONES

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2007

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Vol. 14, No. 4

91-100

EN

The paper presents results of experimental investigation of combustion process in rapid compression machine. New combustion system for spark ignition engines, in which combustion chamber was divided into the prechamber and main chamber was applied. It is known as Jet Dispersion Combustion (JDC) because intensification of combustion process is achieved by the injection of the burning mixture jet into the main chamber. Experimental set up and testing procedure is briefly described. Schlieren system was used to visualize combustion process. Development of combustion process was recorded with high speed camera. The research was focused on study of the influence of prechamber volume, spark location, ignition timing and orifice diameter on flame propagation and pressure variation inside the main combustion chamber. To avoid soot deposition on glass windows of combustion chamber all tests were conducted for propane/air mixture of stoichiometric composition. The research results show that the application of new combustion system allows obtaining the increase of maximum rate ofpressure rise and maximum pressure as well as maximum combustion efficiency.

PL

W pracy przedstawiono wyniki badań eksperymentalnych procesu spalania w maszynie pojedynczego sprężu. W badaniach zastosowano oryginalny system spalania, opracowany w Zakładzie Silników Lotniczych Politechniki Warszawskiej, w którym dokonano podziału komory spalania na komorę wstępną i główną. System ten, znany jako JDC (Jet Dispersion Combustion), intensyfikuje proces spalania w wyniku wtrysku palącej się strugi mieszaniny z komory wstępnej do komory głównej. W artykule przedstawiono opis stanowiska badawczego i stosowanych procedur badawczych. Do wizualizacji procesu spalania został wykorzystany smugoskop. Przebieg procesu spalania był rejestrowany szybką kamerą. Badania prowadzono przy zastosowaniu mieszaniny propanu z powietrzem o składzie stechiometrycznym, w celu uniknięcia zaczernienia wzierników w komorze badawczej. Celem pracy było zbadanie wpływu objętości komory wstępnej, miejsca zapłonu, wyprzedzenia zapłonu oraz średnicy otworu w przegrodzie na szybkość rozprzestrzeniania się płomienia oraz na przebieg ciśnienia w komorze głównej. Wyniki badań wskazują, że zastosowanie tego systemu spalania pozwala uzyskać zwiększenie maksymalnych wartości szybkości narastania ciśnienia, ciśnienia oraz sprawności spalania.

12

Influence of oxygen concentration on combustion characteristics of hydrocarbon-air mixtures under high temperature and pressure

Kanno A., Kawakami T., Sutkowski M., Teodorczyk A.

Journal of KONES

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2006

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Vol. 13, No. 2

197-203

EN

The emission of NOx, SOx, HC and CO2 from internal combustion engines is still a major issue in the development of modern engines. Especially for new concepts, like EGR (Exhaust gas recirculation), developed, detailed information about the pollutant formation is required. However, the experiments of actual standard engines are generally very complicated processes including the residual gas from the last cycle and the flow in an engine cylinder. Thus, experimental data measured using actual engines become unreliable. To obtain the essential data on combustion of hydrocarbon-CO2-N2-O2 mixtures, the experiments have been performed under conditions of high temperature and pressure, which are achieved by a spark ignited opposed rapid compression machine. The main conclusions are as follows: (1) The maximum burning pressure decreases with decreasing oxygen concentration at same EGR ratio. (2) The total burning time decreases with decreasing the concentration of O2 in methane-COx-N2-O2 and propane-CO2-N2-O2 mixtures. (3) The reduction ratio of flame speed is relatively larger on the fuel rich side than that on the lean side. Numerical modeling was focused on the influence of EGR ratio on exhaust emission. Methane fuel was used in the modeling