Implementing Turbomachinery Physics into Data Map-Based Turbocharger Models

Abstract

<div class="htmlview paragraph">A convenient way of modelling turbochargers is based on data maps. These models are easy to put into place, require low CPU charge and are control-oriented. Data relative to compressor and turbine are read from tables: pressure ratio and efficiency are determined as functions of mass flow rate and rotary speed on two distinct data maps. Nevertheless, this type of model has drawbacks: <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">Usually, only higher turbocharger speed data are mapped (> 90000 rpm) although the low rpm zone is the most useful zone for normalized driving cycles simulations. Moreover, maps are poorly discretized, leading to the use of specific extra-interpolation methods (many are identified in [<span class="xref">5</span>]).</div></li> <li class="list-item"> <div class="htmlview paragraph">These methods are purely mathematical, which gives inaccurate results in extrapolation zones. Relation between pressure ratio and efficiency is then broken (i.e., if one implements a pumping model for the compressor, the pressure ratio will be affected, but not the efficiency).</div></li></ul></div> <div class="htmlview paragraph">The present paper develops a new extra/interpolation model incorporating physical laws. An analysis of turbo-machinery equations is performed. A new approach for extra-interpolating performance maps, which satisfies the physical laws stated in turbomachinery equations, is derived from this work. Results from this new model are compared with standard methods.</div> <div class="htmlview paragraph">The major conclusions drawn from this study are: 1 - The new model improves the simulation accuracy while keeping the same easiness of use and robustness. 2 - Extrapolation in the low rpm zone is derived from physical equations. 3 -This method is applicable to both compressor and turbine. 4 - The pressure ratio and efficiency maps are now linked.</div>