The preliminary design of a new combustion chamber requires the combination of many elements of know-how in terms of combustor design rules, aerothermal calculations and preliminary design tools. To use this knowledge more efficiently pre-competitive work on an automated knowledge-based combustor design methodology is done within the European project INTELLECT D.M. (Integrated Lean Low Emission Combustor Design Methodology) in order to set up a KBE (Knowledge Based Engineering) system. In the method presented here, the rules and calculation routines are implemented into an automated preliminary design system using an Excel-driven database to generate a parametric Unigraphics CAD model. The utilized design rules represent state-of-the-art combustor design and will be extended later by lean combustion design rules, which are currently developed within INTELLECT D.M.. The database contains all design parameters and rules to provide CAD, CFD and optimization tools with the required information. Based on a set of performance parameters the system automatically generates the parametric geometry of a combustor containing the liners with cooling devices (optionally Z-ring or effusion cooling) and mixing holes, heat shield, cowl, casings and (pre)diffusor. To estimate the required cooling air, one-dimensional heat transfer equations including convection, radiation and conduction are solved. The generated CAD model visualizes the calculated combustor geometry and forms the basis for an automated CFD mesh generation utilizing the grid generator ICEM CFD.
Advanced state-of-the-art gas turbine combustion chamber design requires a multitude of design rules and parameters using a large number of empirical correlations. In order to allow for a more effective use of this knowledge, the preliminary combustor design system PRECODES was developed in the framework of the European research project INTELLECT D.M. (INTEgrated Lean Low Emission CombusTor Design Methodology). The development of PRECODES has already been described by the authors in previous ASME papers [1], [2]. This paper is focused on the results achieved by the application of the system and the demonstration of its potential regarding an automated combustion chamber design. Since the preliminary design of the combustor is performed and optimized fully automatically by the system, the evaluation and comparison of a much higher number of combustor configurations is possible compared to using a manual design process. Moreover detailed CFD analysis is no more limited to the final design phase, but can now be performed early during the preliminary design phase. The CFD results allow for a detailed postprocessing, to check whether all requirements, as derived from the design rules by correlations are satisfied by the configuration (e.g. zonal air/fuel ratios, residence times). The iterative combustor design process loop, as described by the authors in the previous papers [1], [2] has been closed. New, improved combustor design rules have been derived providing a sophisticated combustor design. Different preliminary combustor configurations are produced by the system on the basis of varying performance parameters and geometric requirements, resulting in a variation of the combustor volume, mixing holes sizes and application of different types of mixing holes required to meet the zonal stoichiometries. Some of the configurations have been analysed and compared more specifically using the detailed post-processing capability. An overview of this detailed post-processing analysis and of the data comparison is given in the paper. A promising configuration has been obtained with respect to NOx and CO emissions, at the same time ensuring sufficient residence times for both relight and combustion efficiency requirements.
The design of state-of-the-art combustion chambers is based on a multitude of design rules. To use this knowledge more effectively and to accelerate the combustor design process an automated combustion chamber design tool is being developed within the European project INTELLECT D.M. (Integrated Lean Low Emission Combustor Design Methodology). Due to the automation of the design process the time required to set up a new preliminary combustion chamber design is reduced from weeks to hours. The development of the automated preliminary combustor design tool is described in [1]. The focus of this paper is on new developments of the design system PRECODES (preliminary combustor design system) including automated mesh generation and CFD simulation. Design rules and parameters are formalized and stored within an EXCEL database. The combustor layout process including the calculations of cooling air mass flows and the zonal layout is done automatically using this database. The layout process has to be iteratively adjusted in order to find an optimal design due to the nonlinear interdependence of some of the design variables. The EXCEL database provides information for two parametric CAD models. The first parametric model includes the flame tube, pre-diffuser, cowl, metering panel, heatshield and the casing. Therefore it is relatively complex and only used for weight approximation and visualization purposes. The second CAD model is a generic model of the flame tube providing the basis for the automatic CFD mesh generation and CFD simulations. The CAD geometry is transferred to the commercial grid generator ICEM-CFD via the ICEM internal direct CAD interface. Based on the CAD geometry a multiblock structured mesh is generated automatically. Due to the utilization of the same blocking master model for different flame tubes varying in combustor size and orientation, and size and position of the mixing holes the mesh topology differs only marginally between different designs. Thus the CFD simulations are well comparable. Different combustor configurations are generated based on input parameter changes, i.e. changing the pressure level, the zonal stoichiometry or the maximum allowable material temperatures. An overview of the present results and the potentials of applying the automated combustor design tool PRECODES is presented.
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