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Neural network approach to compressor modelling with surge margin consideration

Loryś Sergiusz Michał, Orkisz Marek

Archives of Thermodynamics

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2022

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Vol. 43, no 1

89--108

EN

Artificial neural networks are gaining popularity thank to their fast and accurate response paired with low computing power requirements. They have been proven as a method for compressor performance prediction with satisfactory results. In this paper a new approach of artificial neural networks modelling is evaluated. The auxiliary parameter of ‘relative stability margin Z’ was introduced and used in learning process. This approach connects two methods of compressor modelling such as neural networks and auxiliary parameter utilization. Two models were created, one with utilization of the ‘relative stability margin Z’ as a direct indication of surge margin of any estimated condition, and other with standard compressor parameters. The results were compared by determination of fitting, interpolation and extrapolation capabilities of both approaches. The artificial neural networks used during the process was a two-layer feed-forward neural-network with Levenberg–Marquardt algorithm with Bayesian regularization. The experimental data was interpolated to increase the amount of learning data for the neural network. With the two models created, capabilities of this relatively simple type of neural-network to approximate compressor map was also assessed.

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Experimental determination of compressor map of the DGEN 380 engine compressor using the WESTT CS/BV turbine engine simulator

Pazura Karolina, Orkisz Marek

Combustion Engines

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2021

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R. 60, nr 2

26--31

EN

Currently aviation focuses mainlly on increasing the economy and ecology of engines. Production of NOx, CO2 and SO2 adversaly impacts the environment. Parallel goal to minimize SFC to achieve both lower: emission and mission costs. The optimization of components is thus very important. One of the ways of optimizing cycle is doing that based on compressor maps. However it is very expensive to plot one since experimental work needs to be done. The aim of this article is to present a methodology of creating compressor map based on ENGINE ANALOGY. There was used the virtual bench WESTT CS/BV for tests to receive pressure ratio and mass flow of DGEN 380 for three different values of flight speed and altitude, while the rotational speed was changed. The construction similarity of CFM 56-5B and APS 3200 gives the opportunity to plotted compressor maps using the engine analogy without the need for an experiment or using the virtual bench.

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Development of flow and efficiency characteristics of an axial compressor with an analytical method including cooling air extraction and variable inlet guide vane angle

Trawiński Paweł

Archives of Thermodynamics

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2021

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Vol. 42, no 4

17--46

EN

The development of a reliable mathematical model of an axial compressor requires applying flow and efficiency characteristics. This approach provides performance parameters of a machine depending on varying conditions. In this paper, a method for developing characteristics of an axial compressor is presented, based on general compressor maps available in the literature or measurement data from industrial facilities. The novelty that constitutes the core of this article is introducing an improved method describing the performance lines of an axial compressor with the modified ellipse equation. The proposed model is extended with bleed air extraction for the purposes of cooling the blades in the expander part of the gas turbine. The variable inlet guide vanes angle is also considered using the vane angle correction factor. All developed dependencies are fully analytical. The presented approach does not require knowledge of machine geometry. The set of input parameters is based on reference data. The presented approach makes it possible to determine the allowed operating area and study the machine’s performance in variable conditions. The introduced mathematical correlations provide a fully analytical study of optimum operating points concerning the chosen criterion. The final section presents a mathematical model of an axial compressor built using the developed method. A detailed study of the exemplary flow and efficiency characteristics of an axial compressor operating with a gas turbine is also provided.

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Influence of Axial Compressor Model Simplification and Mesh Density on Surge Margin Evaluation

Muchowski Rafał, Gubernat Sławomir Maciej

Advances in Science and Technology. Research Journal

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2021

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Vol. 15, no 3

243--253

EN

The menace of surge occurrence in the compressors is taken very seriously and its avoidance became a fundamental for the design of any modern jet engines. Nowadays, a problem with appropriate evaluation of the compressor surge margin while considering different simplifications of three-dimensional CFD model is still present. For that purpose, this article presents a comparison between the measurement data and several variants of 3D CFD models characterized by a specific mesh density. To calculate all the results on which the comparisons and conclusions are based, an 8-stage axial compressor is taken into account. Flow conditions of the machine are computed for three part load speeds: The low, the mid and the high one respecting the variable guide vanes schedule fitted to the specific load. For each of speed variants a four mesh configurations were generated: coarse, medium, fine and extra-fine. All speed configurations were treated with two different turbulence models – Wilcox k-ω and Menter’s SST k-ω, giving ultimately 15 CFD models, calculated with the TRACE solver using an initialization based on a circumferentially averaged flow solution delivered by the Streamline Curvature Method. During the study an additional assessment of reference grid independence was performed and the mesh convergence has been achieved. A comparison between turbulence models and the measurement proves that SST turbulence model is not well distributed through the speeds in compare to the measurement data and the Wilcox turbulence model. Inconsistency of sensitivity in the mesh coarsening for different rotational speeds was found. Increasing the mesh roughness level has to be executed for each speed separately. Overall compressor map shows that shift of the Pressure Ratio and the Mass Flow decreases with lower rotational speed. Neglecting the system add-ons like labyrinth sealing volumes, bleed-ports and other leakages has a visible influence on deviations from the measurements. Because of intended future use in design and optimization the “Medium” grid with Wilcox k-ω turbulence model was chosen, being a good representation of the Rig characteristics with reduction of the computing time.