In the secondary cooling zone of the continuous casting process water/air nozzles are used to coo... more In the secondary cooling zone of the continuous casting process water/air nozzles are used to cool down the strand. The cooling has to be sufficient enough to ensure a certain shell thickness and finally the complete solidification of the material. Further a controlled and uniform cooling strategy is important to minimize the amount of defects in the solidified steel. For the determination of the water distribution and the cooling characteristic of water/air sprays at defined operation parameters the Nozzle Measuring Stand (NMS) at the Montanuniverstaet Leoben is used. In this work the measuring principle of the NMS is explained and the influence of several nozzle operation parameters on water/air sprays, in particular on their cooling characteristic is shown. In a first step the water distribution (WD) at different nozzle distances, water flows and air pressures was determined. Afterwards the heat transfer coefficient (HTC) for every parameter modification was measured. The surface...
AISTech2019 Proceedings of the Iron and Steel Technology Conference, 2019
Optimal cooling strategies for the secondary cooling zone of the continuous casting process are c... more Optimal cooling strategies for the secondary cooling zone of the continuous casting process are crucial for the production of high-quality steel slabs. To find such strategies it is necessary to understand the influence of spray properties on the cooling performance. Our experimental set-up allows a comparative monitoring of water droplet impingement characteristics on cold and hot steel surfaces. Droplet sizes and velocities at different air-mist spray conditions were examined by laser diffraction analysis and high-speed imaging. Partly, discrimination between incoming primary spray and secondary droplets formed during splashing could be achieved. For all experiments, the area of spray overlapping was of special interest.
Solidification models are an important tool for the prediction of temperatures and shell growth d... more Solidification models are an important tool for the prediction of temperatures and shell growth during the process of continuous casting of steel. To gain reliable simulation results, it is crucial to use highly sophisticated material data and boundary conditions depending on different process parameters. The focus of this work lies on the utilization of experimental data to describe the secondary cooling zone (SCZ) of a slab caster in the solidification model Tempsimu-3D. In this part of the caster, water and air-mist sprays are used to cool down the strand. To calculate the heat transfer coefficient caused by spray cooling (HTCspray), the model uses a correlation between the water impact density (WID) and the surface temperature of the slab. Together with the heat removal due to roll contact and radiation, this HTCspray is applied as a boundary condition for the SCZ. To adjust the parameters of the correlation formula, results from WID and HTC measurements are used. For validation, the simulation results are compared with a measurement of the slab surface temperature.
A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic... more A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic in the spray which was produced with the atomizer was investigated experimentally. Air flow induced in the atomizer causes a pressure reduction, hence the fuel is sucked into the atomizer. The mixture flow of air and liquid caused the atomization downstream due to the turbulence. In the twin-fluid atomizer, atomization is attained by injecting an air stream at tip of the liquid inlet port. In this research, the test liquid supply pressure was kept constant and the air flow rate through the atomizer was varied over a range of air supply pressure to obtain the variation in air liquid mass flow ratio (ALR) from 0.2 to 2.7. The results revealed that the air assisted atomizer had a capability to inject the test liquid in the range of the rates of 0.0019-0.00426 kg/s, with the use of air pressure supplied from 68.9 to 689 kPa. The images of the spray were obtained with a shadowgraph technique and analyzed to obtain the particle size and its distribution. Droplet size from twin-fluid atomizer had various sizes in the range of about 17-200 m. The atomizer can be applied for aerosol and combustion purposes.
In the secondary cooling zone of the continuous casting process water/air nozzles are used to coo... more In the secondary cooling zone of the continuous casting process water/air nozzles are used to cool down the strand. The cooling has to be sufficient enough to ensure a certain shell thickness and finally the complete solidification of the material. Further a controlled and uniform cooling strategy is important to minimize the amount of defects in the solidified steel. For the determination of the water distribution and the cooling characteristic of water/air sprays at defined operation parameters the Nozzle Measuring Stand (NMS) at the Montanuniverstaet Leoben is used. In this work the measuring principle of the NMS is explained and the influence of several nozzle operation parameters on water/air sprays, in particular on their cooling characteristic is shown. In a first step the water distribution (WD) at different nozzle distances, water flows and air pressures was determined. Afterwards the heat transfer coefficient (HTC) for every parameter modification was measured. The surface...
AISTech2019 Proceedings of the Iron and Steel Technology Conference, 2019
Optimal cooling strategies for the secondary cooling zone of the continuous casting process are c... more Optimal cooling strategies for the secondary cooling zone of the continuous casting process are crucial for the production of high-quality steel slabs. To find such strategies it is necessary to understand the influence of spray properties on the cooling performance. Our experimental set-up allows a comparative monitoring of water droplet impingement characteristics on cold and hot steel surfaces. Droplet sizes and velocities at different air-mist spray conditions were examined by laser diffraction analysis and high-speed imaging. Partly, discrimination between incoming primary spray and secondary droplets formed during splashing could be achieved. For all experiments, the area of spray overlapping was of special interest.
Solidification models are an important tool for the prediction of temperatures and shell growth d... more Solidification models are an important tool for the prediction of temperatures and shell growth during the process of continuous casting of steel. To gain reliable simulation results, it is crucial to use highly sophisticated material data and boundary conditions depending on different process parameters. The focus of this work lies on the utilization of experimental data to describe the secondary cooling zone (SCZ) of a slab caster in the solidification model Tempsimu-3D. In this part of the caster, water and air-mist sprays are used to cool down the strand. To calculate the heat transfer coefficient caused by spray cooling (HTCspray), the model uses a correlation between the water impact density (WID) and the surface temperature of the slab. Together with the heat removal due to roll contact and radiation, this HTCspray is applied as a boundary condition for the SCZ. To adjust the parameters of the correlation formula, results from WID and HTC measurements are used. For validation, the simulation results are compared with a measurement of the slab surface temperature.
A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic... more A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic in the spray which was produced with the atomizer was investigated experimentally. Air flow induced in the atomizer causes a pressure reduction, hence the fuel is sucked into the atomizer. The mixture flow of air and liquid caused the atomization downstream due to the turbulence. In the twin-fluid atomizer, atomization is attained by injecting an air stream at tip of the liquid inlet port. In this research, the test liquid supply pressure was kept constant and the air flow rate through the atomizer was varied over a range of air supply pressure to obtain the variation in air liquid mass flow ratio (ALR) from 0.2 to 2.7. The results revealed that the air assisted atomizer had a capability to inject the test liquid in the range of the rates of 0.0019-0.00426 kg/s, with the use of air pressure supplied from 68.9 to 689 kPa. The images of the spray were obtained with a shadowgraph technique and analyzed to obtain the particle size and its distribution. Droplet size from twin-fluid atomizer had various sizes in the range of about 17-200 m. The atomizer can be applied for aerosol and combustion purposes.
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Papers by Lukas Preuler