Vattenfall

About: Vattenfall is a company organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Wind power & Combustion. The organization has 685 authors who have published 857 publications receiving 18912 citations. The organization is also known as: Vattenfall AB & Kungliga Vattenfallstyrelsen.

Arrangement on a jet burner for the combustion of pulverized coal in a combustion chamber with reduced NOx emissions

Abstract: The arrangement has a jet burner with main burners, and fuel nozzles horizontally bounded by bottom, intermediate and top air nozzles. Additional side air nozzles (6) are arranged on both side of each fuel nozzle without lateral distance to the fuel nozzles. The side nozzles have a same vertical extension as the fuel nozzles and the main burners. The side air nozzles are formed of single nozzles with round or rectangular cross section.

Comparison of field and circuit generator models in single machine infinite bus system simulations

Abstract: This paper compares the transient response of a finite element salient pole synchronous generator model connected to an infinite network bus to that of a system model based on an equivalent circuit representation of the machine. The characteristics and operating conditions of the two models are made equal as far as possible by thoroughgoing initiation and by using the finite element model for estimation of the circuit model parameters. It is found that the circuit model underestimates the stiffness and damping properties of the machine in comparison with the electromagnetic model, which largely is believed to be attributable to inadequate representation of the rotor circuits. The results raise questions regarding some common applications of equivalent circuit models.

Effects of Void Ratio and Hydraulic Gradient on Permeability and Suffusion of Glacial Till Cores

Abstract: Dams with core of broadly graded glacial moraines (tills) exhibit signs of internal erosion by suffusion to a larger extent than dams constructed with other types of materials, as reported by Sherard (1979). Garner and Fannin (2010) indicated that internal erosion initiates when an unfavorable combination of soil material, stress conditions and hydraulic load occur. A laboratory program, carried out at Lulea University of Technology (LTU), aims to study the effects of void ratio and hydraulic gradient on the initiation of suffusion of glacial till. It consists of suffusion tests conducted in permeameters with an inner diameter 101.6 mm and a height of 115 mm. Results show, as expected, that the hydraulic conductivity is lower with lower void ratio. Nevertheless, as the hydraulic gradient increases, the hydraulic conductivity reaches steady values. Changes in the hydraulic conductivity suggest variation in the initial void ratio due to detachment of the finer particles from the soil matrix. These fine particles start clogging the lower layers, therefore the rate of water flow decreases and so does the hydraulic conductivity. The hydraulic gradient for which the hydraulic conductivity reaches steady values is considered as the upper limit without suffusion evolved.