Holger Streb

Advanced Burner Development for the VX4.3A Gas Turbines

The Vx4.3A gas turbine family has already been well received by the market. Nevertheless the market drives technology towards both increased turbine inlet temperatures and reduced emissions.The HR3 burner was originally developed for the V4.2 and Vx4.3 fleet featuring silo combustors in order to mitigate the risk of flashback and to improve the NOx- emissions (Prade, Streb, 1996). Due to its favourable performance characteristics in the Vx4.3 family the advanced HR3 burner was adapted to the Vx4.3A series with annular combustor.The paper reports upon the design, testing and field evaluation steps which were necessary to implement the burner for the 50 and 60 cycle gas turbines.With CFD calculations the flow field and the mixing of natural gas and combustion air have been optimised. A number of tests in the Siemens test facilities confirmed these predictions. The atmospheric 3 burner segment combustion test rig allows to test flame interaction, stability and exhaust gas emission simultaneously.In the Siemens Berlin Test Facility which provides a platform for full scale gas turbine testing 24 HR3-burners were implemented into a V84.3A gas turbine with a base load power output of 184 MW at ISO conditions for prototype testing before introducing this new burner generation into the bigger 50 cycle family V94.3A.Implementation of 24 scaled HR3 burners were installed in the V94.3A of Cottam Development Centre (Great Britain) and demonstrated an excellent performance. The gas turbine reached an ISO base load output of 265 MW with NOx emissions well below 25 ppmvd.Due to the very promising test results in Berlin and Cottam, this burner modification, which can be retrofitted to all VX4.3A gas turbines, was implemented nearly fleet wide.Copyright

Application of Endoscopic OH*-Chemiluminescence Measurements at a Full-Scale High-Pressure Gas Turbine Combustion Test Rig

Single burner combustion tests play a key role in the Siemens gas turbine combustion system development process. The main scope of these tests is to assess the performance of combustor design variants in terms emissions or combustion stability at gas turbine relevant operation conditions. Both emissions and combustion stability strongly depend on the flame front and flame position. A pragmatic approach to investigate the flame is to detect the chemiluminescence signal of the combustion intermediate species OH*. Thus, the OH*-chemiluminescence signal was recorded at high-pressure combustion tests to get more insight in the complex interactions between combustor design, operation conditions and combustion performance.To minimize the impact of the measurement system on the combustion behavior, the optical access to the test rig was realized by using a water-cooled probe with an UV-transparent endoscope. The probe was located in the test rig side-wall, downstream of the burner outlet, viewing towards the burner with a 90° angle relative to the endoscope orientation. The experimental setup was completed by a combination of bandpass filters and an ICCD camera.During the experiments acoustic pressure oscillations inside the combustion chamber were recorded simultaneously to the chemiluminescence images to allow for phase-sorting of the recorded images during the image post-processing. The post-processed images then were correlated with the pressure oscillations to investigate the relationship of the heat release to the pressure oscillations.The measurements were carried out during single burner gas turbine combustion tests at realistic gas turbine operation conditions at a scaled pressure of 9 bar.This paper presents selected test results and discusses how they give new insight in the complex combustion processes at full-scale high-pressure gas turbine combustion tests.Copyright

Burner Development for Flexible Engine Operation of the Newest Siemens Gas Turbines

The newest Siemens gas turbine family has already been well received by the market. Nevertheless, the market drives continuing development of the family and the combustion system. Central focus is put on further increasing reliability and component lifetime and on increased inspection cycles, as well as increasing the engine power output and efficiency, which is directly linked to higher turbine inlet temperatures. Increasing attention, however, is given to the flexibility concerning fuel quality and according fluctuations. Additionally, more and more strict emission requirements must be considered. This paper especially reports on demonstration of the capability of the Siemens gas turbines with an annular combustion system to fulfil the requirements for the highest operational flexibility. Thus, the combustion system has been tested and qualified for the highest operating flexibility with special fuel requirements such as burning Naphtha, Light Oil #2 and Natural gas with an extremely wide range of heating values as well. Also special operation modes such as fuel changeover, fastest load changes for island grid operation, frequency response and load rejection require this highly flexible combustion system without any hardware exchange. In different frames when fired with natural gas, base load is reached with the NOx emissions ranging well below 25 ppmvd, confirming the high potential of this advanced hybrid burner. In liquid fuel operation, dry NOx emissions of 75ppmvd were demonstrated but by injecting fuel / water emulsion NOx emissions were reduced to below 42 ppmvd with different liquid fuel qualities. Combustion dynamics, unburned Hydrocarbons, CO and soot emissions remained always below the required limits.Copyright

Combustion System Update SGT5-4000F: Design, Testing and Validation

The first Siemens AG SGT5-4000F engine with hybrid burner ring combustor (HBR) was introduced in 1996. Since then, frequent evolutionary design improvements of the combustion system were introduced to fulfill the continuously changing market requirements. The improvements particularly focused on increased thermodynamic performance, reduced emissions, and increasing operational flexibility in terms of load gradients, fuel flexibility, and turndown capability.According to the Siemens product development process, every design evolution had to pass several validation steps to ensure high reliability and best performance. The single steps included cold flow and mixing tests at atmospheric pressure, high-pressure combustion tests in full-scale sector combustion test rigs, and full engine tests at the Berlin test facility (BTF).After successful validation, the design improvements were gradually released for commercial operation. In a first step, cooling air reduction features have been implemented in 2005, followed by the introduction of a premixed pilot as second step in 2006. Both together resulted in a significant reduction of the NOx emissions of the system. In a third step, an aerodynamic burner modification was introduced in 2007, which improved the thermo-acoustic stability of the system towards higher turbine inlet temperatures and adapted to fuel preheating to allow for increased cycle efficiency. All three features together have been released as package in 2010 and to date accumulated more than 50,000 operating hours (fleet leader 24,000).This paper reports upon the steps towards this latest design status of the SGT5-4000F and presents results from typical focus areas of lean premixed combustion systems in gas turbines including aero-dynamical optimization, fuel/air mixing improvements and cooling air management in the combustor.Copyright