Numerical investigation on effect of spark plug configuration on performance in an engine cylinder

A numerical investigation of combustion inside single and twin-spark engines was performed to study the effect of a spark plug, positions and spark timings on engine performance. Improvement in engine performance is one of the automotive industry's primary research areas. Consequently, the study's results can be utilised to optimise engine configurations to achieve maximum performance. The investigation was conducted using a finite volume-based open-source software, OpenFOAM, for computational simulations. Simulations were conducted using the XiEngineFOAM solver with a transport equation for modelling flame fronts. The Standard k-e turbulence model was used to predict turbulence parameters. The simulation was conducted for compression and power stroke (crank angle between - 180° and 180°), assuming an even distribution of the air-fuel mixture within the pentroof 4-valve engine cylinder. Simulations were conducted for four cases, including variations in the position and timing of spark plugs in single-spark and twin-spark engines. According to the results of the simulations, the single-spark engine provides the best performance when the spark plug is ignited early and positioned at the cylinder's centre. When placed at an optimal position determined by flame travel and collision, the twin-spark engine gives the best performance at the highest difference between the spark timings of the two spark plugs

Characterization of optical fiber after surface modification

katedra: KTT; přílohy: CD ROM; rozsah: 80 s.Optical fibers have been used principally for data transmission, since it offers fast connectivity, low cost, and high resistance to damage. The purpose of this research was not to evaluate the data capabilities of plastic optical fibers (POF) which transmits axially, but rather to exploit the ability of the fiber emit light through the side of the fiber. The uses of side emitting fibers in textile would prove to beneficial in several ways, few of them being the flexibility of the fiber for integration into fabrics, and possibly to mask this fiber like all others, with the aid of classical textile dyeing methods. The POF, with trade name Flexi was used in this case, because of its flexibility, and variation in diameters available on the market. Flexi cores were stripped from its cladding, and were dyed using a disperse dye, under various conditions including changing in dye concentration and dye time. Samples were then analysed for side emission of light with the use of Prototype 1, which was an instrument specifically designed for the measurement of this nature. The results showed that the dye penetration is dependent on the dye time, if dye concentration and temperature are kept constant. After 40minutes of dyeing, the fiber core showed an increase in side emission, with lower loss due to attenuation. Also excessive time in the hot conditions degraded the fiber, such that the fiber became very stiff and brittle. Fibers were also subjected to heat, in the form of boiling water bath, for selected periods of time, and it was found that the effect was similar to that of the prior experiments. Surface treatment of Flexi fibers were carried out using ethyl acetate as an etching agent, to possibly accept more disperse dye on the fibers surface. The results after dyeing showed a more than significant improvement in both side emission and attenuation of light. The influence of the illuminating source of the fiber also proved to be important, such that the side emission is dependent on the temperature of light from the source.Optical fibers have been used principally for data transmission, since it offers fast connectivity, low cost, and high resistance to damage. The purpose of this research was not to evaluate the data capabilities of plastic optical fibers (POF) which transmits axially, but rather to exploit the ability of the fiber emit light through the side of the fiber. The uses of side emitting fibers in textile would prove to beneficial in several ways, few of them being the flexibility of the fiber for integration into fabrics, and possibly to mask this fiber like all others, with the aid of classical textile dyeing methods. The POF, with trade name Flexi was used in this case, because of its flexibility, and variation in diameters available on the market. Flexi cores were stripped from its cladding, and were dyed using a disperse dye, under various conditions including changing in dye concentration and dye time. Samples were then analysed for side emission of light with the use of Prototype 1, which was an instrument specifically designed for the measurement of this nature. The results showed that the dye penetration is dependent on the dye time, if dye concentration and temperature are kept constant. After 40minutes of dyeing, the fiber core showed an increase in side emission, with lower loss due to attenuation. Also excessive time in the hot conditions degraded the fiber, such that the fiber became very stiff and brittle.Fibers were also subjected to heat, in the form of boiling water bath, for selected periods of time, and it was found that the effect was similar to that of the prior experiments. Surface treatment of Flexi fibers were carried out using ethyl acetate as an etching agent, to possibly accept more disperse dye on the fibers surface. The results after dyeing showed a more than significant improvement in both side emission and attenuation of light. The influence of the illuminating source of the fiber also proved to be important, such that the side emission is dependent on the temperature of light from the source