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Flame stabilization in a swirl-stabilized combustor occurs in an aerodynamically generated recirculation region which is a result of vortex breakdown. The characteristics of the recirculating flow are dependent on the swirl number and on axial pressure gradients. Coupling to downstream pressure pulsations is also possible. In order to fix the position of the recirculation zone, an extended fuel lance was inserted into the burner. An additional benefit of the extended lance was to enable secondary fuel injection directly into the recirculation zone where the flame is stabilized. Tests were conducted with and without secondary fuel injection. The measurements included optimization of the location of the extended lance in the mixing chamber and variation of the amount of secondary fuel injection at different equivalence ratios and output powers. Flow visualizations showed that stabilization of the recirculation zone was achieved. The effect of the extended lance on pressure and heat release oscillations and on emissions of NOx, UHC and CO was investigated. The results were confirmed in high pressure single burner pressure tests and in a full scale land-based test gas-turbine. The lance has been successfully implemented in engines with sufficient stability margins and good operational flexibility. This paper shows the careful development process from lab scale tests to full scale engine tests until the implementation into the field engines.

A novel combustion technique, based on the Double Cone Burner, has been developed and tested. N 0 x emissions down to very low levels are reached without the usual strong dilution of the fuel for MBtu syngases from oxygen blown gasification of coal or residual oil. A limited amount of dilution is necessary in order to prevent ignition during the mixing of fuel and combustion air.The relevant properties of the fuel are reviewed in relation to the goal of achieving premixed combustion. The basic considerations lead to a fuel injection strategy which is completely different from that for natural gas. A high speed premixing system is necessary due to the very short chemical reaction times of MBlu fuel. Fuel must be prevented from forming ignitable mixtures inside the burner for reliability reasons. A suitable fuel injection method, which can be easily added to the ABB double cone burner, is described. In common with the design of the standard EV burner, the MBtu EV burner with this fuel injection method is inherently safe against flashback.Three dimensional flow field and combustion modelling is used to investigate the mixing patterns and the location of the reaction front. Two burner test facilities, one operating at ambient and the other at full gas turbine pressure, have been used for the evaluation of different burner designs. The full pressure . tests were carried out with the original gas turbine burner size and geometry. Combing the presented numerical predictive capabilities and the experimental test facilities, burner performance can be reliably assessed for a wide range of MBtu and LBtu fuels (residue oil gasification, waste gasification, coal gasification etc.).The atmospheric tests of the burner show NO x values below 2 ppm at an equivalence ratio equal to full load gas turbine operation. The NO x increase with pressure was found to be very high. Nevertheless, NO x levels of 25 vppmd (e7) 15% 02) have been measured at full gas turbine pressure. Implemented into ABB's recently introduced gas turbine 0T13E2 the new combustion technique will allow a more straightforward IGCC plant configuration without air extraction from the gas turbine to be used.

Results from ignition and cross-ignition tests performed on an atmospheric 60°-sector test rig equipped with three EV-type burners are presented. Based on these results a model was developed for an annular combustor, which calculates the primary ignition and burner-burner cross-ignition limits for the combustor in terms of burner operation variables (equivalence ratio and pilot fuel ratio) using a generally applicable methodology described in the paper. Key ingredients of the model are the description of mixture flammability and a mixing model representing the ignition relevant mixing behaviour of the burners in the annular combustor. Ignition and cross-ignition are observed to occur, if the mixture equivalence ratio determined from the mixing model is above the flammability limits calculated for the particular operating conditions. Even in the case of cross iginition across an externally piloted or switched-off burner, the model reproduces the experimental cross-ignition limits, confirming that the basic physics have been captured.

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The transverse profile of the circulating beam of the CERN PS is obtained from the interaction between the particles and a thin wire rapidly moving through it. The signal from a secondary particles monitor or the secondary emission current of the wire is sampled against the wire position every four beam revolutions in the machine. A stand-alone desk compu ter performs the real-time control of the wire displa cement as well as the acguisitions and calculations necessary to display the profiles and the corres ponding emittances. A traversing speed of 20 m/s in the measurement area is reached, using a high torque motor rigidly linked to a U shaped wire holder. All elements are carefully designed and chosen for low inertia and minimum load on the wire. This enables measurements of high energy beams of more than 1013 p/p in the PS with negligible emittance blow-up due to multiple scattering. This blow-up is still acceptable at injection energy. A link to the PS main computer allows operation from any one of the main consoles.

The NOx emissions of low NOx premix combustors are not only determined by the burner design, but also by the multi burner interaction and the related distribution of air and fuel flows to the individual burners. Often the factors that have a positive impact on NOx emission have a negative impact on the flame stability, so the main challenge is to find an optimum point with the lowest achievable NOx while maintaining good flame stability. The hottest flame zones are where most of the NOx is formed. Avoiding such zones in the combustor (by homogenization of the flame temperature) reduces NOx emissions significantly. Improving the flame stability and the combustion control allows the combustor to operate at a lower average flame temperature and NOx emissions. ALSTOM developed a combustion optimization package for the GT13E2. The optimization package development focused on three major issues: • Flame stability; • Homogenization of flame temperature distribution in the combustor; • Combustion control logic. The solution introduced consists of: • The reduction of cooling air entrainment in the primary flame zone for improved flame stability; • The optical measurement of the individual burner flame temperatures and their homogenization by burner tuning valves; • Closed loop control logic to control the combustion dependent on the pulsation signal. This paper shows how fundamental combustion research methods were applied to derive effective optimization measures. The flame temperature measurement technique will be presented along with results of the measurement and their application in homogenization of the combustor temperature distribution in an engine equipped with measures to improve flame stabilization. The main results achieved are: • Widening of the main burner group operation range; • Improved use of the low NOx operation range; • NOx reduction at the combustor pulsation limit and hence, large margins to the European emission limit (50 mg/m3 @ 15%O2).

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