Filtyp
Coherent anti-Stokes Raman scattering of pure rotational transitions, rotational CARS, is demonstrated as an efficient method for temperature determination in sooting flames. The dual broadband CARS approach was used to measure temperature profiles in premixed, sooting ethylene flames at atmospheric pressure by probing the nitrogen gas. The recorded spectra were of equally high quality in non-soot
Swan band emission of C2. which had been produced and excited (d3∏x←a 3∏u, Δ v = 0) by focused, tunable, visible laser radiation, was studied in sooting ethylene flames. The C2signal from the sooting regions of the flames was found to be proportional to the measured volume fractions of soot, indicating laser-vaporized soot to be the source of the signal, and as such it can be used as a diagnostic
Laser-induced fluorescence from carbon atoms, excited at the two-photon resonances around 280 nm, has been detected in fuel-rich hydrocarbon flames together with Swan band emission from the C2 radical, which was non-resonantly excited at the same wavelengths. The emission from the C atom and from the C2 molecule exhibited several similarities, indicating a possible common photo-chemical origin.
Recent developments in rotational CARS thermometry and critical issues when comparing vibrational and rotational CARS thermometry are described. In particular, the development of dual broadband rotational CARS and the noise characteristics of this approach are emphasized. The difficulty with unambiguous temperature determination in vibrational CARS with unknown parameters, in particular the nonres
High elevations of groundwater at Mosul city is a very big problem and may cause mass destructions to the environment, health and building foundations due to the closing of groundwater near ground surface. From field investigations for 43 large diameter shallow wells, the water elevations were measured 14 times through 7 months. Utilizing raster based GIS operations with automated parameter estima
A model for calculating the noise in nonlinear optical processes arising from (nonquantum) stochastic fluctuations (mode beating) in and between the lasers participating in the nonlinear interaction has been previously developed. Assuming that all individual laser mode phases and laser modes are (statistically) independent (Gaussian statistics) and that the nonlinear interaction can be expressed a
The temperature in the thermal boundary layer close to the combustion chamber wall was measured under knocking and non-knocking conditions using dual-broadband rotational coherent anti-Stokes Raman Scattering (CARS). A horseshoe-shaped combustion extension was employed to get an optical access to the region near the combustion chamber wall. Time-resolved measurements of the cylinder pressure (at t
It is generally accepted that knocking combustion influences the heat transfer in SI engines. However, the effects of heat transfer on the onset of knock is still not clear due to lack of experimental data of the thermal boundary layer close to the combustion chamber wall. This paper presents measurements of the temperature in the thermal boundary layer under knocking and non-knocking conditions.
Pure rotational coherent anti-Stokes Raman scattering (CARS) has for the first time been investigated for pressures up to 44 MPa in nitrogen gas at room temperature. An atomic filter consisting of a heated cell with sodium vapour was successfully applied for suppression of stray light originating from the narrowband CARS pump laser beam. With increasing pressure the rotational CARS spectrum is smo
Cycle-resolved end-gas temperatures were measured using dual-broadband rotational CARS in a single-cylinder spark-ignition engine. Simultaneous cylinder pressure measurements were used as an indicator for knock and as input data to numerical calculations. The chemical processes in the end-gas have been analysed with a detailed kinetic mechanism for mixtures of iso-octane and n-heptane at different
Laser-induced fluorescence measurements have been performed in turbulent non-premixed flames close to the lift-off point and in laminar premixed acetylene flames. The spectrally analyzed fluorescence signal showed good correspondence to known spectra from glyoxal (C2H2O2). Laser-induced fluorescence spectra from glyoxal vapor using the same excitation wavelength of 428 nm showed the same strongest
To study the hydrology of peatlands and explore wetness distribution is difficultmainly due to the complexity of the surface of peatlands, and also due to the presence of permafrost underlain peatlands in the arctic regions. I have chosen the area called Stordalen mire in the arctic region in northern Sweden for my study.In this thesis, I aimed to study spatially distributed hydrological modelling
Two-dimensional visualization of soot has been realized in flames with the use of laser-induced fluorescence in C2 from laser-vaporized soot [LIF(C2)LVS]. Soot particles are heated to vaporization temperatures by the absorption of laser radiation. C2 radicals produced by this process are excited at wavelengths around 563 nm through the transition ν′ = 0 d3∏g←ν″ = 1 a3∏u, and the subsequent fluores
Biogenic volatile organic compounds (BVOCs), which are mainly emitted by vegetation, may create either positive or negative climate forcing feedbacks. In the Subarctic, BVOC emissions are highly responsive to temperature, but the effects of climatic warming on BVOC emissions have not been assessed in more extreme arctic ecosystems. The Arctic undergoes rapid climate change, with air temperatures i
Shrubs have increased in abundance and dominance in arctic and alpine regions in recent decades. This often dramatic change, likely due to climate warming, has the potential to alter both the structure and function of tundra ecosystems. The analysis of shrub growth is improving our understanding of tundra vegetation dynamics and environmental changes. However, dendrochronological methods developed
