Experimental Investigation of Fuel Mixing Concepts for 3rd Generation DLE Burners : Evaluation Through Water Rig and Atmospheric Combustion Rig Measurements

Abstract: New Siemens burner concepts thought to produce a more homogeneous air/fuel mix-ture and a better distribution of the fuel over the burner cross section have been evaluated. A homogeneous air/fuel mixture is known to produce the lowest levels of emitted oxides of nitrogen (NOx) which is a main objective for Siemens Industrial Turbomachinery AB (SIT). It is desired that a burner concept can be found which further reduces the amount of emitted NOx but at the same time maintains a moderate pressure drop. A water rig was used in in order to evaluate the mixing performance of the new concepts. A video camera, a laser and a fluorescent substance, simulating fuel, was used to record movies of the burner mixing tube cross section. The movies were post processed in Matlab using in-house scripts where intensity and RMSD fields were obtained. These fields were used to compare the fuel mixing ability of totally 21 new burner concepts to the burner concept currently applied in the SGT-800. The water rig experiments have shown that a more homogeneous air/fuel mixture, compared to the reference burner, is possible to achieve with 11 out of the 21 tested concepts. The water rig has shown a repeatability within 5%. The water rig results obtained from a test with the reference burner were also compared to CFD simulation results. The water rig showed good agreement to the CFD simulation when comparing the trends of the fuel mixing ability. Two of the newly developed concepts were also tested in the Atmospheric Combustion Rig (ACR) at SIT to evaluate the pressure drop and emitted NOx in atmospheric conditions. One of these concepts showed a deterioration of the fuel mixing performance based on the water rig experiments while the other showed an improvement. The expectations of these concepts in terms of emitted NOx were therefore a significant deterioration and improvement, respectively. The results showed that both concepts performed quite similar with a moderate reduction of emitted NOx. The unexpected results have been derived to the pressure dependence of NOx, burner to burner differences from manufacturing and the small amount of available measurement points. The measured pressure drop over the burners reached unacceptable levels and the design of the new concepts therefore needs further improvements.