Investigation of the laminar and turbulent combustion behavior in a one-cylinder internal combustion engine

Thrun, Alexander

This Thesis deals with the analysis of the combustion behavior of a gas-fueled one cylinder internal combustion engine used in a commercially available nail gun (BeA Gasnagler). The main focus was laid on the difference in combustion under laminar and under turbulent conditions, the latter induced by solid obstacles in the chamber or by a small electrical fan located in the top of the cylinder head. Additionally, different fuel compositions, consisting of either propane-air or propene/1-buteneair, were investigated. A major part of the Thesis was the design and setup of the required optical and electronic detection systems as well as the re-design of the engine electronics and housing for their implementation in the experimental detection systems. The combustion process was investigated for pressure-time traces, piston velocity and flame expansion characteristics. For the latter, two detection systems were developed. The whole flame structure was imaged using the flame’s chemiluminescence, while the two-dimensional flame could be visualized using the fluorescence of OH radicals around λ = 314nm probed at λ = 283.01nm by a laser-induced fluorescence (LIF) system. For the characterization of the fan-induced turbulent flow, a particle image velocimetry (PIV) setup was built. In comparison to laminar conditions, the fan-induced turbulence enhanced the combustion efficiency drastically, as indicated by an increase of the rate of pressure rise in the chamber by a factor of 10 to (dp/dt) ≈ 1300 bar s−1. Turbulent combustion was investigated for flame quenching effects, as a strong decrease of ignition probability of premixed propane-air fuels was found for a fan start Δtfan = -250 ms before ignition, corresponding to a fan speed of ufan ≈ 10,000 rpm and a Reynolds number of Re= 40,000. This effect could not be observed for the unsaturated fuel, which was externally injected using pre-filled cartridges.

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Thrun, Alexander: Investigation of the laminar and turbulent combustion behavior in a one-cylinder internal combustion engine.

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