Next generation turbine power plants will require high efficiency gas turbines with higher pressure ratios and turbine inlet temperatures than currently available. These increases in gas turbine cycle conditions will tend to increase NOx emissions. As the desire for higher efficiency drives pressure ratios and turbine inlet temperatures ever higher, gas turbines equipped with both lean premixed combustors and selective catalytic reduction after treatment eventually will be unable to meet the new emission goals of sub-3 ppm NOx. New gas turbine combustors are needed with lower emissions than the current state-of-the-art lean premixed combustors.In this program an advanced combustion system for the next generation of gas turbines is being developed with the goal of reducing combustor NOx emissions by 50% below the state-of-the-art. Dry Low NOx (DLN) technology is the current leader in NOx emission technology, guaranteeing 9 ppm NOx emissions for heavy duty F class gas turbines. This development program is directed at exploring advanced concepts which hold promise for meeting the low emissions targets.The trapped vortex combustor is an advanced concept in combustor design. It has been studied widely for aircraft engine applications because it has demonstrated the ability to maintain a stable flame over a wide range of fuel flow rates. Additionally, it has shown significantly lower NOx emission than a typical aircraft engine combustor and with low CO at the same time. The rapid CO burnout and low NOx production of this combustor made it a strong candidate for investigation. Incremental improvements to the DLN technology have not brought the dramatic improvements that are targeted in this program. A revolutionary combustor design is being explored because it captures many of the critical features needed to significantly reduce emissions.Experimental measurements of the combustor performance at atmospheric conditions were completed in the first phase of the program. Emissions measurements were obtained over a variety of operating conditions. A kinetics model is formulated to describe the emissions performance. The model is a tool for determining the conditions for low emission performance. The flow field was also modeled using CFD.A first prototype was developed for low emission performance on natural gas. The design utilized the tools anchored to the atmospheric prototype performance. The 1/6 scale combustor was designed for low emission performance in GE's FA+e gas turbine.A second prototype was developed to evaluate changes in the design approach. The prototype was developed at a 1/10 scale for low emission performance in GE's FA+e gas turbine. The performance of the first two prototypes gave a strong indication of the best design approach.Review of the emission results led to the development of a 3 rd prototype to further reduce the combustor emissions. The original plan to produce a scaled-up prototype was pushed out beyond the scope of the current program. The 3 rd prototype was designed at 1/10 scale an...
An efficient methodology to capture the nonlinear responses of combustor systems with prestress and Coulomb friction is developed. The combustor systems experience wear at the interfaces between components due to flow-induced vibrations. In particular, wear has been observed at the interface between the transition piece and the hula seal, and at the interface between the hula seal and the liner. These interfaces are prestressed, and their vibratory response has a softening nonlinearity caused by Coulomb friction combined with microslip. In addition, the contact between the hula seal and the transition piece is that between a convex surface and a concave surface. Hence, geometric nonlinearity of the contact stiffness in the normal direction is present also. These phenomena are hard to capture by full-order finite element (FE) approaches because they require time marching or harmonic balancing of very large models. To address this issue, we develop reduced order models (ROMs) which are specifically designed to capture Coulomb friction (combined with micro- and macroslip). To demonstrate the proposed approach, a simplified hula seal is placed between two very rigid plates (which relate to the transition piece and the liner). For validation, contact elements are used to model the interface between the plates and the hula seal. Transient dynamic analysis (TDA) in ansys is applied to the full-order model. The model is shown to exhibit softening nonlinearity and microslip at all levels of prestress. To show that ROMs for this system are possible (i.e., they exist), we use proper orthogonal decomposition (POD) to show that the dynamics is dominated by a low number of spatial coherences. For a variety of frequency ranges and prestress levels, we show that a single such coherence is dominant. Next, low order models are proposed and their parameters are identified. A systematic method to identify these parameters is developed. Particular attention is paid to the amount of calculations needed for obtaining these parameters. Finally, the ROMs are validated by comparing their predictions with results from TDA for the full-order model. We show that these ROMs can accurately predict the nonlinear response of the system.
In this paper, the unsteady aero loads in a typical gas turbine fuel nozzle (GTFN) are analyzed using detached eddy simulation (DES) and finite element models. These numerical models are validated with component and system level rig test data collected at GE Power & Water's combustion laboratory in Greenville, SC, and the models are used as design tools to reduce periodic pressure forces on GTFNs with a purge flow concept. Moreover, field tests were conducted at a joint development platform facility to verify the dynamic response during the design analysis cycle (DAC). This DAC is an example of GE Power & Water's capability in assessing the durability of its hardware using a combination of analytical tools and laboratory tests, along with verifications through field tests in real conditions. Such resources have enabled GE engineers to improve the hardware design and increase the life of GTFNs as a result. Nomenclature D h= hydraulic diameter f = frequency M = moments (with x, y, z subscripts for components) S = Strouhal number U = velocity
The application of the trapped vortex combustor (TVC) concept to heavy-duty gas turbine conditions has been explored. Combustor stability, lean blow out, and emission performance requirements limit design options for conventional lean premixed combustors. The TVC concept has demonstrated reduced emissions and high turndown with liquid fuels and could overcome existing lean premixed performance constraints as well. The present study examines premixed injection of natural gas into the TVC at heavy-duty gas turbine conditions. The emission performance is measured over a range of operating conditions. The combustor turndown and dynamics performance are also presented. To forecast the performance potential of the TVC combustor a chemical reactor network model was developed. The model was anchored with experimental data and implemented in the prediction of TVC combustor emissions and turndown performance. The reactor model confirms that NOx reduction greater than 60% is possible using a trapped vortex combustor (TVC).
An efficient methodology to capture the nonlinear responses of combustor systems with pre-stress and Coulomb friction is developed. The combustor systems experience wear at the interfaces between components due to flow-induced vibrations. In particular, wear has been observed at the interface between the transition piece and the hula seal, and at the interface between the hula seal and the liner. These interfaces are pre-stressed, and their vibratory response has a softening nonlinearity caused by Coulomb friction combined with micro-slip. In addition, the contact between the hula seal and the transition piece is that between a convex surface and a concave surface. Hence, geometric nonlinearity of the contact stiffness in the normal direction is present also. These phenomena are hard to capture by full order finite element approaches because they require time marching or harmonic balancing of very large models. To address this issue, we develop reduced order models (ROMs) which are specifically designed to capture Coulomb friction (combined with micro-slip and macro-slip). To demonstrate the proposed approach, a simplified hula seal is placed between two very rigid plates (which relate to the transition piece and the liner). For validation, contact elements are used to model the interface between the plates and the hula seal. Transient dynamic analysis (TDA) in ANSYS is applied to the full order model. The model is shown to exhibit softening nonlinearity and micro-slip at all levels of pre-stress. To show that ROMs for this system are possible (i.e., they exist), we use proper orthogonal decomposition to show that the dynamics is dominated by a low number of spatial coherences. For a variety of frequency ranges and pre-stress levels, we show that a single such coherence is dominant. Next, low order models are proposed and their parameters are identified. A systematic method to identify these parameters is developed. Particular attention is paid to the amount of calculations needed for obtaining these parameters. Finally, the ROMs are validated by comparing their predictions with results from TDA for the full-order model. We show that these ROMs can accurately predict the nonlinear response of the system.
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