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1

Low Temperature Combustion of Jet Propellant-8 Fuel in Compression Ignition Engine with the Low Compression Ratio

Pawlak Grzegorz, Płochocki Patryk, Skrzek Tomasz

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 4

273--283

EN

Jet Propellant-8 (JP-8) is used as a fuel for a standard Compression Ignition (CI) engine instead of diesel oil, especially in the military applications. The properties of a kerosene-type fuel, which is JP-8, encourage us to test different strategies of mixture creation and combustion, which could be more effective for this fuel than these elaborated for diesel oil. The experiment aimed to show whether it is possible to realise an effective Low Temperature Combustion (LTC) strategy in a CI engine with a low compression ratio for JP-8 fuel. The tests were focused on the combustion of a lean homogeneous JP-8/air mixture close to the knock limit. Additionally, the combustion process of the homogeneous mixtures diluted with EGR was examined. The AVL research engine with a common rail system and low compression ratio (CR = 12) was adapted for the tests. In order to create a homogeneous mixture early, multi injection of JP-8 under high pressure (90 MPa) was applied. The results of the HCCI operation were compared to the Partially Premixed Combustion (PPC) mode without EGR, tested on the same engine with a low CR. The experiment showed that it is possible to realise the LTC process for the HCCI engine fueled with JP-8, though the knock limited the engine load. The application of EGR allowed controlling the phase and rate of the heat release. The higher share of EGR made the HCCI engine cycles less repetitive. Generally, for the HCCI engine operation, the CO and total hydrocarbons (THC) emissions were on a high level. The PM emission was also relatively high, whereas NOx was maintained on a low level for all of the examined points.

2

Hydrous Methanol Fuelled HCCI Engine Using Ignition Improver CAI Method - ANN Approach

Venkatesan M., Moorthi N. S. V., Franco P. A., Manivannan A., Karthikeyan R.

Mechanics and Mechanical Engineering

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2015

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Vol. 19, nr 1

31--49

EN

The present study is to examine the performance and emission characteristics of a Homogeneous Charge Compression Ignition (HCCI) engine where hydrous methanol (85% methanol and 15% water) is used as primary fuel and Diethyl ether (DEE) as an ignition improver. A modified diesel engine has been used as a HCCI engine. By measuring the excess air ratio (λDEE), the quantity of DEE flow rate is measured and excess air ratio (fiDEE) is varied from fiDEE5.6 to fiDEE 9.5. Experimental results reveal that HCCI engine gives better brake thermal efficiency (BTE) at high loads (λDEE 9.5). It shows decrease in oxides of nitrogen (NOx) emission, slightly high emission of carbon monoxide (CO) and unburned hydrocarbon (HC) compared to conventional compression ignition (CI) engine. Radial basis function neural network (RBFN) model has been developed with brake power, excess air ratio and energy share as input and BTE, CO, HC, NOx, rate of pressure rise as output. About 80% of total experimental data is used for training purposes, and 20% is used for testing. The performance of the developed RBFN model were compared with experimental data, and were statistically evaluated which was found to be in good agreement.

3

Ocena strat cieplnych silnika HCCI z wewnętrzną recyrkulacją spalin na podstawie badań symulacyjnych

Hunicz J., Gęca M.

Logistyka

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2014

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nr 6

4555-4563

PL

W pracy przedstawiono analizę strat cieplnych silnika HCCI (ang. Homogeneous Charge Compression Ignition) wykorzystującego wewnętrzną recyrkulację spalin. Aby uzyskać wewnętrzną recyrkulację spalin stosuje się tzw. ujemne współotwarcie zaworów i zredukowany wznios zaworów. Taka modyfikacja układu rozrządu powoduje, że w cyklu pracy silnika 4-suwowego sprężanie występuje dwukrotnie. W związku z tym zwiększa się współczynnik wymiany ciepła pomiędzy czynnikiem roboczym i ściankami komory spalania. Z drugiej jednak strony, temperatura czynnika roboczego podczas spalania jest mniejsza niż w silniku o zapłonie iskrowym (ZI). Wykorzystując model komputerowy silnika przeprowadzono porównawcze obliczenia strat cieplnych silnika w dwóch konfiguracjach; silnika pracującego w trybie HCCI oraz pracującego w trybie ZI. Analiza wykazała, że w trybie pracy HCCI współczynnik przejmowania ciepła przez ścianki komory spalania jest większy, jednakże jest on kompensowany przez niższe temperatury czynnika roboczego. Ponadto, zredukowane straty wymiany ładunku oraz mniejsza entalpia spalin powodują znaczące zwiększenie sprawności cieplnej w stosunku do trybu pracy ZI.

EN

The paper presents an analysis of thermal losses in HCCI (Homogeneous Charge Compression Ignition) engine with internal exhaust gas re-circulation. Internal gas re-circulation was achieved using negative valve overlap technique at reduced valve lifts. Application of modified valvetrain operation resulted in dual compression during a single cycle of 4-stroke engine. Consequently, coefficient of heat exchange between in-cylinder gas and the walls of combustion chamber was increased. However, mean in-cylinder temperatures were lower than in spark ignition engines. Using computer simulations of the engine working cycle analysis of heat losses in HCCI combustion versus spark ignition combustion was performed. The obtained results have shown that in the case of HCCI combustion coefficient of heat exchange between the working fluid and the combustion chamber walls was higher than one in the case of spark ignition combustion. However, it was compensated by the lower average in-cylinder temperature. Additionally, reduced gas exchange losses and lower exhaust enthalpy provided an increase in thermal efficiency over the spark ignition combustion.

4

Increase of high load limit in a gasoline HCCI engine

Hunicz J., Kordos P., Gęca M.

Journal of KONES

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2012

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Vol. 19, No. 4

231-238

EN

Engine operation in HCCI mode allows for improvement of thermal efficiency and substantial reduction NOX emission. The most production feasible solution for gasoline HCCI engine is application of exhaust gas trapping using a negative valve overlap. This technique increases thermal energy of a mixture, thus allowing for auto-ignition at moderate compression ratios. However, high exhaust gas re-circulation rate decreases volumetric efficiency. As a result, achievable engine loads are also reduced. Supercharging can be applied in order to improve volumetric efficiency and extend high load limit. However, increase of amount of intake air can lead to reduction of start of compression temperature via decrease of residuals in a mixture. In order achieve HCCI mode of combustion, temperature of start of compression must be kept within narrow limits. In this study experimental and modeling investigations were presented. Experiments were carried out using single cylinder research engine. The engine was equipped with fully variable valvetrain and direct gasoline injection. Application of mechanical boosting allowed for widening achievable load range in HCCI mode of operation. Numerical calculations allowed for determination of admissible valvetrain settings and intake pressure, which guarantee proper temperature of start of compression.

5

A novel in-cylinder fuel reformation approach to control HCCI engine combustion on-set

Gnanam G., Haggith D., Sobiesiak A.

Silniki Spalinowe

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2009

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R. 48, nr 3

37-48

EN

Homogeneous Charge Compression Ignition (HCCI) engines have the potential to deliver high thermal efficiencies (when compared to spark ignition engines) coupled with ultra-low NOx emissions and Particulate Matter (PM) for partialload operating regions. However, the inherent absence of Start of Combustion (SOC) or combustion on-set control has been a major obstacle for implementing this technology into production engines. In the present work, a new in-cylinder reformation strategy to control the on-set of combustion has been incorporated into a HCCI engine fuelled with lean ethanol/air mixtures. The objective of the in-cylinder reformation process is to generate hydrogen enriched gas (which includes other intermediate species) from ethanol reformation, which is then used to control the subsequent HCCI cycle combustion on-set. The experimental engine used for the study is a four-stroke, three cylinder In-Direct Injection (IDI) type compression ignition engine which was converted to single cylinder operation for HCCI combustion. A prototype reformation chamber has been designed and fabricated with direct injection capabilities to examine the proposed in-cylinder reformation process. In order to clarify the effects of reformation products on HCCI combustion on-set, experiments were conducted with constant engine speed, initial charge temperature, and engine coolant temperature.The engine performance was evaluated based on cycle-resolved in-cylinder pressure measurements and regulated engineout emissions. The experimental results demonstrate that the proposed in-cylinder reformation strategy is an effective method for controlling HCCI combustion on-set (SOC) and reduces the regulated engine-out emissions. Furthermore, the experimental results indicate that there is an optimal in-cylinder reformation fuelling percentage which will have a positive impact on regular HCCI combustion at given operating conditions.

PL

Silniki o zapłonie samoczynnym zasilane mieszanką jednorodną (HCCI) umożliwiają osiąganie większych wartości sprawności cieplnej w porównaniu do silników o zapłonie iskrowym z jednoczesną ultraniską emisją tlenków azotu NOx oraz cząstek stałych (PM) w zakresie średnich obciążeń silnika. Jednak brak wyraźnego początku spalania (SOC) lub sterowania chwilą samozapłonu stanowią ważną przeszkodę wprowadzenia tej technologii do silników produkcyjnych. W tym artykule omówiono zastosowanie nowej metody sterowania chwilą samozapłonu w silniku HCCI napędzanym ubogimi mieszankami etanol/powietrze, która jest oparta na procesie reformingu paliwa wewnątrz cylindra (polegającym na gazyfikacji i wzbogaceniu w wodór, przyp. red.). Celem tego procesu jest wygenerowanie gazu bogatego w wodór podczas reformingu etanolu, który jest następnie używany do kontroli chwili zapłonu w cyklu HCCI. Do eksperymentu wykorzystano czterosuwowy, trzycylindrowy silnik o zapłonie samoczynnym z wtryskiem pośrednim, który przekształcono w silnik pracujący na pojedynczym cylindrze ze spalaniem typu HCCI. Prototypową komorę do reformingu zaprojektowano i zbudowano z możliwością wtrysku bezpośredniego, w celu przetestowania przebiegu tego procesu wewnątrz cylindra. W celu wyjaśnienia wpływu reformingu na chwilę samozapłonu HCCI, eksperymenty przeprowadzono przy stałej prędkości obrotowej silnika, stałej początkowej temperaturze dawki paliwa oraz czynnika chłodzącego silnika. Pracę silnika oceniano w oparciu o pomiary ciśnienia wewnątrz cylindra i pomiary emisji związków toksycznych. Wyniki eksperymentu pokazują, że proponowany reforming wewnątrz cylindra jest efektywną metodą kontroli chwili zapłonu HCCI, zmniejszającą również emisję. Wskazują one również, że istnieje optymalny procent paliwa poddawanego reformingowi wewnątrz cylindra, który pozytywnie wpływa na spalanie w silnikach HCCI w danych warunkach.

6

HCCI engine - idea and expectations. Case study

Kowalewicz A.

Journal of KONES

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2008

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Vol. 15, No. 2

217-224

EN

Internal combustion engines yet have not exhausted their development possibilities in the range of economy and ecology demands. Development of SI and CI engines, which several years ago proceeded individually in-parallel, now becomes likely in common: one type of engine shares some features with the other one, e.g. direct injection, electronically controlled injectors, electronic control unit etc. However, type of ignition and mixture formation are still different (spark assisted ignition versus auto ignition and homogeneous mixture versus heterogeneous). HCCI engine overcomes this difference. At present HCCI engine uses both type of ignition modes and both types of mixture in different ranges of operational parameters. Direct injection during compression stroke and stratified charge are characteristics for low and mild power resulting in low emission of CO and HC as well as NOx. Combustion is initiated by spark when mixture is very poor. For maximum load and speed, auto-ignition of homogeneous stoichiometric mixture takes place in the whole volume of combustion chamber. Due to the absence of flame and low temperature, nitrogen oxides, of which molecules arise in post flame zone, are low. Also emission of CO and HC are low due to stoichiometry of the mixture. The key problem is controlled auto-ignition as a function of speed and load (fully HCCI engine). Several methods of auto-ignition control (CAI) are discussed in this paper.

7

An HCCI engine fuelled with is-octane, ethanol and their blends

Gnanam G., Sobiesiak A., Reader G.

Journal of KONES

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2006

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Vol. 13, No. 2

81-94

EN

This paper investigates Homogeneous Charge Compression Ignition (HCCI) combustion on an engine that is fuelled with ethanol, iso-octane, and ethanol/iso-octane. The engine is a four-stroke three cylinder in-direct injection type diesel engine converted to a single cylinder HCCI operation. In order to clarify the effects of fuel chemistry on HCCI combustion, the trials were done at a constant engine speed, a fixed initial charge temperature and engine coolant temperature. The HCCI engine was fuelled with a lean mixture of air and fuel (ethanol, iso-octane or mixture of ethanol/iso-octane). The engine performance parameters studied here include indicated mean effective pressure (IMEP) and thermal efficiency. Heat-release rate (HRR) analysis was done to determine the effect of fuels on combustion on-set. The experimental results demonstrate that the addition of iso-octane to ethanol retards the on-set of combustion and subsequently leads to a reduction of the IMEP and thermal efficiency. For a particular fuel, the on-set of combustion depends closely on the intake charge temperature (as reported by several other researchers) and any increase in the initial charge temperature leads to advances in the on-set of combustion. Furthermore, the experimental results demonstrate that operating the engine on a lean charge reduces engine-out NOx emissions significantly.

8

Spalanie mieszanki DME i gazu ziemnego w silniku HCCI

Ishida M., Jung S., Ueki H., Sakaguchi D.

Silniki Spalinowe

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2005

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R. 44, nr 2

20--29

PL

Celem tego opracowania jest wyjaśnienie charakterystycznych cech zapłonu, procesu spalania, granicy spalania stukowego i granicy wypadania zapłonu mieszanki gazu ziemnego i niewielkiej ilości eteru dimetylowego (DME) w silniku HCCI. W badaniu spalania gaz ziemny i niewielka ilość DME zostały dodane do powietrza dolotowego w postaci mieszanki jednorodnej. Współczynnik nadmiaru powietrza dla gazu ziemnego został zwiększony w celu wykrycia granicy spalania stukowego lub granicy wypadania zapłonu silnika testowego HCCI przy stałej ilości DME. Eksperymentalnie zbadano wpływ dodania gazu ziemnego na stłumienie niskotemperaturowych reakcji DME oraz wpływ ilości DME i temperatury dolotu na szybkość reakcji utleniania, granicy spalania stukowego mieszanki DME/gaz ziemny, oraz zakres obciążenia silnika HCCI.

EN

The objectives of the present study is to clarify ignition characteristics, the combustion process, the knock limit and the misfire limit of natural gas mixed with a small amount of dimethyl ether (DME) in a HCCI engine. In the combustion test, natural gas and a small amount of DME were charged into the suction air homogeneously. The equivalence ratio of natural gas was increased to find the knock limit or the misfire limit of the HCCI test engine under a constant DME amount. The effect of the natural gas addition on suppression of the low temperature reaction of DME, and the effects of the DME amount and the intake temperature on the reaction rates, the knock limit of the DME/natural gas mixture, and the operation load range of the HCCI engine were investigated experimentally.