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Investigation of the Radical Nitration of Isooctane Fuel via Nitromethane Propellant

Bayar C. C.

Central European Journal of Energetic Materials

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2018

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Vol. 15, no. 2

225--242

EN

The possible radical nitration reactions of isooctane fuel with nitromethane propellant, which is generally used as an additive in fuel formulations, were thermodynamically investigated both at room temperature and at a higher temperature of 691.15 K. The temperature of 691.15 K was chosen because it is the auto-ignition temperature of isooctane and nitromethane and has the potential to mimic better engine conditions. The computational calculations were performed at the theoretical level of DFT UB3LYP/cc-pVDZ. Four different nitration reactions and nitrated products were considered and interpreted in detail. The most and the least favorable nitrations were observed at the primary and secondary carbons of isooctane at 691.15 K, respectively. Four of the designated reactions were endothermic at this temperature. The other outcome of this study was that there was a direct relationship between the thermodynamic tendencies of the considered reactions and the ballistic performances (detonation velocities, detonation pressures, and specific impulses) of their nitrated products. The thermodynamic properties of heats of combustion and deflagration temperatures were calculated via empirical formulations based on the stoichiometry and some other structural parameters of the energetic materials. The results for nitromethane and the nitro-isooctane products were examined.

2

Ortho-para spin conversion of Ps by paramagnetic O2 dissolved in organic compounds

Zgardzińska B., Białko W., Jasińska B.

Nukleonika

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2015

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Vol. 60, No. 4, part 1

801--804

EN

The o-Ps mean lifetime value in liquids decreases in the presence of the paramagnetic oxygen molecules via the ortho-para conversion process. This effect was observed for several organic samples composed of carbon and hydrogen atoms differing in the arrangement of atoms forming the molecule, e.g. n-alkanes, alcohols, branched isomer of alkane, cycloalkane. The usually observed tendency of the o-Ps lifetime value to be an increasing function of temperature (in the case of measurements performed in vacuum) changes to a decreasing one in the presence of O2 dissolved in the sample. The difference between the o-Ps lifetimes measured in samples in vacuum and in the presence of O2 increases with the distance from the melting point. The ortho-para constant rate λconv was estimated to be ~130 μs–1 at 300 K for three compounds investigated.

3

A comparison of burning characteristics of iso-octane and ethanol fuels in an optical SI engine

Moxey B., Cairns A., Zhao H.

Journal of KONES

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2013

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Vol. 20, No. 2

299--305

EN

Over the next few decades the automotive industry will be faced with a number of challenging decisions as the world’s supply of oil reduces and the global population increases beyond 7 billion. These factors have driven some researchers to look at blending fossil fuels with alternatives such as crop-produced alcohols (or so-called biofuels). The currently reported study was concerned with the combustion characteristics of ethanol-isooctane blended fuels in a specially designed, single cylinder, spark ignition research engine equipped with full bore overhead optical access. The testing was undertaken using port fuel injection (PFI) and was focused on the behaviour of differing ethanol concentrations under varied internal exhaust gas re-circulation levels (IEGR). Simultaneous high speed imaging and in-cylinder pressure data analysis was used to understand the fundamental influence of varying ethanol content on turbulent flame propagation and subsequent mass burning. The resulting images were analysed looking at the speed of the advancing flame and the shape factor of the burning velocity. The initial evidence suggested that under the moderate speeds and loads tested, poor charge mixture preparation associated with ethanol was leading to fast but unstable burn rates. This could be avoided and combustion improved by using increased valve overlap settings, with the hot residuals entering the intake port aiding the full evaporation of the fuel.

4

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.