Knut Vaagsaether

Experiments with Flame Propagation in a Channel with a Single Obstacle and Premixed Stoichiometric H 2-Air

Results of an experimental study of flame propagation in a 100 mm by 100 mm cross section and 1500 mm long open channel with a single obstacle (BR = 0.9) are presented. The gas mixture in the experiments were 30%vol H 2 in air. Both perpendicular and angular light were used for schlieren photography. The study included how point and distributed ignition source affected the flame propagation and pressure buildup. The main objective was to investigate whether the flame propagation could be simplified with a two-dimensional assumption for CFD simulation purposes. Flame front inversion was seen in the experiments, and after inversion it never turned back to the original shape again. After the inversion the flame could not be considered two-dimensional. A visible boundary layer grew in front of the flame as it inverted.

Experimental Study of Gas Explosions in Hydrogen Sulfide-Natural Gas-Air Mixtures

An experimental study of turbulent combustion of hydrogen sulfide (H2S) and natural gas was performed to provide reference data for verification of CFD codes and direct comparison. Hydrogen sulfide is present in most crude oil sources, and the explosion behaviour of pure H2S and mixtures with natural gas is important to address. The explosion behaviour was studied in a four-meter-long square pipe. The first two meters of the pipe had obstacles while the rest was smooth. Pressure transducers were used to measure the combustion in the pipe. The pure H2S gave slightly lower explosion pressure than pure natural gas for lean-to-stoichiometric mixtures. The rich H2S gave higher pressure than natural gas. Mixtures of H2S and natural gas were also studied and pressure spikes were observed when 5% and 10% H2S were added to natural gas and also when 5% and 10% natural gas were added to H2S. The addition of 5% H2S to natural gas resulted in higher pressure than pure H2S and pure natural gas. The 5% mixture gave much faster combustion than pure natural gas under fuel rich conditions.

A METHOD FOR ESTIMATING THE BURNING VELOCITY IN A TUBE BY USING EXPERIMENTAL PRESSURE RECORDS AND THE ONE-DIMENSIONAL RCMLAB CODE

This paper describes a method for determining the quasi one-dimensional burning velocity for gas explosion experiments in a smooth tube from pressure records. A one-dimensional random choice method code (RCMLAB) has been written in MATLAB. The combustion model in RCMLAB treats the combustion wave as a discontinuity. For a given burning velocity S(t), we can find the weak deflagration solution and calculate the flow field. This allows us to estimate S(t) from the measured pressures. This was done using a proportional controller with the difference ΔP between estimated and observed pressure as input and the time derivative of S as output. The experimental setup consists of three tubes with a diameter of 22 mm and lengths of 1, 2, and 5 m. The tubes were filled with premixed stoichiometric propane/air. The model for determining the burning velocity for a gas explosion in a smooth tube seems to work quite well.