Flexibility is key to the future success of natural gas fired power generation. As renewable energy becomes more widely used, the need for reliable, flexible generation will increase. As such, gas turbines capable of operating efficiently and in emissions compliance from extended low load to full load will have a significant advantage. A wider range of gas fuels, including shale gas and refinery/industrial byproduct gas, is becoming increasingly available, with the opportunity to further reduce the cost of electricity. A combustion system capable of operating with wider ranges of heavy hydrocarbons, hydrogen and inerts will have an advantage to accommodate the future fuel gas trends and provide value to gas turbine operators. The FlameSheet™ combustor incorporates a novel dual zone burn system to address operational and fuel flexibility. It provides low emissions, extended turndown and fuel flexibility. FlameSheetTM is simply retrofittable into existing installed E/F-class heavy duty gas turbines and is designed to meet the energy market drivers set forth above. The operating principle of the new combustor is described, and details of a full scale high pressure rig test and engine validation program are discussed, providing insight on rig and engine emissions, as well as combustion dynamics performance. The FlameSheetTM implementation and validation results on a General Electric 7FA heavy duty gas turbine operating in a combined cycle power plant is discussed with emphasis on operational profile optimization to accommodate the heat recovery steam generator (HRSG), while substantially increasing the gas turbine normal operating load range.

One of the common issues within the industrial gas turbine fleet is the susceptibility of a can-annular combustors’ fuel manifold cover (support housings) to develop embedded cracks. These cracks, located in the assembly joint of cover plates that create internal passages for fuel delivery to the combustion system, have enough of a driving force to propagate to the surface of the component. Once a crack propagates to the surface, gas has the potential to leak into the enclosure, posing a potential fire and safety risk. Furthermore, cracked fuel manifold covers are prone to increased NOx levels and excessive dynamics. Consequently, operators have the potential for a forced outage due to the failure of the fuel manifold. Currently, the existing solution is to replace the support housings with new or refurbished housings, with prior analyses requiring near perfect fusion. An ultrasonic inspection procedure has been developed to inspect a combustor’s fuel manifold cover for embedded cracks, which are not currently detectable with FPI or X-ray methods. Through this method, the amount of fusion in the assembly joint is readily obtained, including the ability to understand if the crack is partial-thickness or through-thickness. Parametric fracture analyses, utilizing experimental material test data calibrated to service-exposed components, are conducted to predict the residual life. Coupled with the engine operating data, including the use of cold- or heated-fuels, a recommendation for the remaining useful operation of the support housings can be provided. Ultimately, by completing the ultrasonic inspection and analysis on the support housing/fuel manifold, both the risk of an unplanned outage in the future and the lifecycle management cost to the operator is reduced.

Improvements in turbine performance are increasingly driven by the need to control leakage both in the main gas path as well as in the secondary air flow system. Seals for static to static interfaces have a wide usage in gas turbine for component interface locations and are becoming more important as engines reach higher temperature targets and compressor pressure ratios. Both flex and honeycomb seals have been used for many years during other OEM seal service upgrades. These seals are designed to be capable of sustaining low leakage operation whilst achieving long lifetimes. To determine the sealing capability of honeycomb and flex seals an advanced hydraulically actuated rig was designed and constructed. A series of leakage performance tests were carried out that accurately simulate engine conditions, including pressure and relative axial and radial movements. The results of these tests are compared against previously presented data on standard membrane seals. Compared to the membrane seal, the flex seal has approximately 60% lower equivalent clearance when tested with uneven (triangular) grooves. This reduction was due to the bending of the seal and subsequent closing of the seal gap under pressure. The flex and membrane seal performed similarly well under more nominal conditions. The honeycomb seal achieved a consistently low leakage under all pressure loadings. All three sealing types have their place in the required technology mix which is essential when aiming for maximized engine performance and lifetime.