Experimental and Numerical Investigation of a Compressor Cascade at Highly Negative Incidence

Abstract

ABSTRACT:The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade-and consequently engine-performance remain unexplored at relatively far off-design conditions, such as windmilling or sub-idle. Such regimes are dominated by blade operation under extremely low mass flows and rotational speeds that imply highly negative values of incidence angle, thus totally separated flows on the pressure side of the blades. Those flow patterns are difficult to be measured and even more difficult to be numerically predicted as the current modelling capability of separated internal flows is of limited reliability. In this paper, the performance of a 3-dimensional linear compressor cascade at highly negative incidence angle is initially experimentally investigated. The main objective of the study is to derive the total pressure loss and outlet flow angle through the blades and use the data for the validation-calibration of a numerical solver enhancing its capability to predict highly separated flows. The development of the CFD model and the simulation strategy followedare also presented.The numerical results are compared against the derived test data demonstrating a good agreement. In addition, most trends of the properties of interest have been captured sufficiently, therefore the physical phenomena are considered to be well captured, allowing the numerical tool to be used for further studies on similar test cases.

Development of a Preliminary Design Method for Subsonic Splittered Blades in Highly Loaded Axial-Flow Compressors

“…The variables of i eq and δ eq herein can be gained by a typical correlation methodology developed by Lieblein [7] for conventional blades, which has been extensively employed by Banjac et al [9], McGlumphy [18], and Zachos et al [19]. The method can be expressed implicitly by Equations (10) and 11:…”

“…Therefore, it is necessary to correct the correlations with off-reference conditions so as to apply the model under practical compressor circumstances. Based on the basic correlations, the reference minimum-loss incidence and deviation angles can be modified with additional corrections from different factors, as shown in Equations (18) and (19):…”

Experimental analysis of the unsteady, turbilent flow through the fan stage of a high-bypass turbofan in windmilling conditions

“…Yet a detailed understanding of the flow features inside the critical components is essential for a reliable prediction of the overall performance, especially in severe off-design operating conditions. Available detailed experimental and numerical studies, conducted on a compressor cascade (Zachos et al, 2011) and on a contemporary high-bypass ratio turbofan in an altitude test cell (Prasad and Lord, 2010) indicate that, in windmilling operation, the fan stage operates under severe off-design (negative) angle-of-attack conditions, leading to the development of flow separation on both rotor and stator. These observations were confirmed by a previous experimental study on a small, geared turbofan, at ground level (García Rosa et al, 2015).…”

Effect of Combustor Geometry on Performance of Airblast Atomizer Under Sub-Atmospheric Conditions

“…However, the increasing fidelity and reliability of numerical solvers encourages their use for studying the spray phenomena under conditions that are otherwise difficult to reproduce within an experimental environment. Examples of successful application of CFD studies can be found in Zachos et al (2011), Manzar et al (2009) and Chalet et al (2010). In this paper, results from a number of atomizer CFD simulations that were run at sub-atmospheric pressures are presented.…”