Browsing by Author "Azamar Aguirre, Hasani"

Now showing 1 - 4 of 4
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    Considerations on axial compressor bleed for sub-idle performance models
    (American Society of Mechanical Engineers, 2021-01-11) Roig Tió, Ferran; Ferrer-Vidal, Luis E.; Azamar Aguirre, Hasani; Pachidis, Vassilios
    The trend towards increased bypass ratio and reduced core size in civil aero-engines puts a strain on ground-start and relight capability, prompting renewed interest in sub-idle performance modelling. While a number of studies have looked at some of the broad performance modelling issues prevalent in this regime, the effects that bleed can have on sub-idle performance have not been addressed in the literature. During start-up and relight, the unknown variation in bleed flows through open handling bleed valves can have a considerable impact on the compressor’s operating line. This paper combines experimental, numerical and analytical approaches to look at the effect that sub-idle bleed flows have on predicted start-up operating lines, along with their effect on compressor characteristics. Experimental whole-engine data along with a purpose-built core-flow analysis tool are used to assess the effect of bleed model uncertainty on engine performance models. An experimental rig is used to assess the effects of reverse bleed on compressor characteristics and measurements are compared against numerical results. Several strategies for the generation of sub-idle maps including bleed effects are investigated.
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    Development of a research model to study the operability of a variable pitch fan aero engine in reverse thrust
    (Global Power and Propulsion Society, 2020-09-09) Rajendran, David John; Bentley, David; Azamar Aguirre, Hasani; Tunstall, Richard; Pachidis, Vassilios
    A rationale for the level of model fidelity required to provide the most representative flow field information to ascertain the feasibility of using a Variable Pitch Fan (VPF) in a modern high bypass ratio aero engine to generate reverse thrust is described in this paper. This is done by comparing the 3D RANS flow field solution for a newly developed reverse flow VPF design from two research models: i) isolated engine model in which the bypass duct, guide vanes, splitter and VPF are wrapped in an axisymmetric nacelle and placed in a generic far-field domain and b) integrated model in which the engine is installed to an airframe in landing configuration through a pylon and placed in a far-field domain bound by a rolling runway. The flow field solution obtained at an aircraft landing speed of 80 knots indicates that even though both models can predict the general flow patterns, there are substantial differences in parameters such as the amount of reverse stream, circumferential distribution of flow properties and flow development downstream of the engine. These differences impact the levels of reverse thrust generated, flow distortion entering the core engine and resultant airframe forces. This study makes the case that it is necessary to use an integrated model that includes a full engine nacelle installed on an airframe, to answer design questions for engineering the VPF system to generate reverse thrust.
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    Development of a streamline curvature axial-flow compressor performance simulator graphical-user-interface for design and research
    (International Society for Air Breathing Engines (ISABE), 2017-09-11) Azamar Aguirre, Hasani; Pachidis, Vassilios; Templalexis, Ioannis
    The all-time interest to increase turbomachinery efficiencies and pressure ratios has led to the progression of more robust and accurate simulation methods and tools. Even though 3-D CFD analyses are highly detailed and despite the computational power nowadays, they can be costly in terms of time and resources. Conversely, 2-D SLC methods provide acceptable performance and flow field results in short times. Because of economical and practical reasons, SLC still represents the cornerstone for turbomachinery design. In the present, the knowledge demand from the academia community in the airbreathing engine field has been expanding year after year. Nevertheless, there are very few open-source turbomachinery solvers that can be accessed, where user needs to know at least the basics of the programming language syntax and familiarize with it. For these reasons, a GUI was developed for an existing in-house 2-D SLC axial-flow compressor performance code, called SOCRATES. A GUI in this context supports as a teaching mechanism to explain not only the method itself, but also the compressor aerodynamic behaviour. The SOCRATES GUI consists in the axial-flow compressor model setup, solution and visualization for geometry and results. This paper outlines the main features of the 2-D SLC GUI, and uses a two-stage fan to show the flow field parameters and compressor/fan map, showing a consistent agreement against measured data.
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    An improved streamline curvature-based design approach for transonic axial-flow compressor blading
    (International Society for Air Breathing Engines (ISABE), 2017-09-11) Azamar Aguirre, Hasani; Pachidis, Vassilios; Templalexis, Ioannis
    The increasing demand to obtain more accurate turbomachinery blading performance in the design and analysis process has led to the development of higher fidelity flow field models. Despite extensive flow field information can be collected from threedimensional (3-D) Reynolds-averaged Navier-Stokes (RANS) numerical simulations; it comes at a high computational cost in terms of time and resources, particularly if a comprehensive design space is explored during optimization. In contrast, through-flow methods such as streamline curvature (SLC), provide a flow solution in minutes whilst offering acceptable results. Furthermore, if the SLC fidelity is improved, a more detailed component-blading study is expected. For this reason, a fully-detailed transonic flow framework was implemented and validated in an existing in-house two-dimensional (2-D) SLC compressor performance to improve the performance results fidelity in transonic conditions. The improvements consist of two sections: (1) blade-profile modelling; (2) flow field solution. The bladeprofile modelling considers a 3-D blade-element-layout method to correctly model the sweep and lean angle, which determine the shock structure. The essential part of the transonic flow framework is its solution, formed of two parts: (1) a physics-based shock-wave model to predict its structure, and associated losses; (2) and a novel choking model to define the choke level for future spanwise mass flow redistribution. To demonstrate the functionality of the full comprehensive transonicflow approach, the well-known NASA Rotor 67 compressor was used to prove that the inlet relative flow angle should be limited by the choking incidence at the required blade span locations. A 3-D RANS numerical simulation for the NASA Rotor 67 validated the transonic-flow model, showing minimum differences in the spanwise mass flow distribution for the choked off-design cases. The current improvements implemented in the 2-D SLC compressor/fan performance simulator enhance the fidelity not only in analysis mode, but also in design optimisation applications.