Session: 34-06 Axial compressor design methods

Paper Number: 129347

129347 - Design Guidelines for Inertial Particle Separators 

Helicopter engines are designed to breathe clean air, free of particulate matter. The reality of course, especially in dusty environments of the harshest operating theatres, is quite different. When particles of atmospheric dust are drawn into the engine, they can erode compressor blades, corrode metal surfaces, deposit on to surfaces, and clog critical gas flow pathways. This leads to a decrease of fuel efficiency and a reduction of operating life. To prolong useful engine life in austere environments, an inertial particle separator may be integrated with the engine by the OEM or offered as an option, integrated with the intake, by the airframer.

Inertial particle separators rely on sharp changes to the flow direction to cause particles to deviate from fluid streamlines and be separated from the core flow [1]. Such changes also cause losses in total pressure due to friction, total pressure distortion, and in some cases flow separation. Controlling the duct flow path and cross-sectional area is critical to achieving maximum efficiency with minimum pressure loss. Recent advances in additive manufacturing, coupled with new markets in more electric or fully electric aircraft, have opened-up a wider design space for this method of air-cleaning, which is compact and offers low drag. In this contribution, we describe the development of a fast, reduced order model to solve the flow-field and particle concentration gradient across an inertial particle separator, in order to provide guidelines for inertial particle separator design and explore new concepts for non-annular geometries.

The particle separator is defined by a mean gas path, which sits at the centroid of the duct cross-section. The model framework computes the centripetal drag force by first transforming the principal mean gas path into the Serret-Frenet reference frame to measure the local radius of curvature, and second, solving the local one-dimensional flow field by application of the isentropic flow equations for ideal gas. Loss in pressure due to wall friction, bends, and rapid area expansion are accounted for at each point along the gas path. We demonstrate the capability of the reduce order approach to rapidly and accurately predict the two performance parameters of inertial separators - pressure drop and separation efficiency - by comparing with results from a known test case in the literature [2]. We then apply the code to three hypothetical conceptual designs and show to what extent the key design parameters of splitter position, throat position, gas path curvature (through spline control points), and scavenge efficiency affect the two competing objectives of minimum pressure loss and maximum separation efficiency. Key findings are that a high aspect ratio cross-section is favoured to maximise separation area, and that splitter position is used as a tuning parameter to maximise separation efficiency for a given target test dust.

[1] Filippone, A., & Bojdo, N. (2010). Turboshaft engine air particle separation. Progress in Aerospace Sciences, 46(5–6), 224–245. https://doi.org/10.1016/j.paerosci.2010.02.001

[2] Barone, D., Loth, E., & Snyder, P. (2017). Influence of particle size on inertial particle separator efficiency. Powder Technology, 318, 177–185. https://doi.org/10.1016/j.powtec.2017.04.044

Presenting Author: Nicholas Bojdo University of Manchester

Presenting Author Biography: Nicholas Bojdo is a senior lecturer in the School of Engineering at the University of Manchester. He completed his PhD in 2012 on the subject of helicopter intake protection. He specialises in particle transport and reduced order performance modelling, with application to the impact of gas turbines operating in dusty environments. He has been investigator on four research council funded projects and one EU CleanSky project, and has authored over 20 peer-reviewed journal papers. He has partaken in two NATO Research Task Groups and is a Member of the Royal Aeronautical Society, UK Vertical Lift Network, and Vertical Flight Society.

Authors:

Nicholas Bojdo University of Manchester
Antonio Filippone University of Manchester