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Abstract
The compressor of the gas turbine set consumes around 50 %-60 % of the
power generated by its turbine. Reducing the power consumed by the compressor
increases the net power produced by a gas turbine set. This power gain is attributed
to the redistribution of the power flow within the set. Therefore, this power
increase does not accompanied with increase in thermal or mechanical stresses
within the set. One of the most common technologies for the augmentation of the
gas turbine power is wet compression. Wet compression can be achieved by
introducing liquid DROPlets into the compressor. DROPlets evaporation during
compression process has what could be called micro-inter-cooling effect. This
leads to a reduction in the compressor consumed power.
In this study a numerical model is developed to study the effect of wet
compression on the performance of axial compressors. A commercial CFD code,
FLUENT, is used to solve the governing equations in a three dimensional, unsteady,
and turbulent flow simulation of a three stage axial flow compressor. Liquid
DROPlets are introduced as a dispersed phase and are tracked in a Lagrangian frame
to simulate the wet compression process. The model accounts for DROPlet-flow,
DROPlet-DROPlet, and DROPlet-wall interaction. Turbulence phenomenon is treated
using the RNG k - & turbulence model. The effect of turbulence on the dispersion
of DROPlets is taken into account using a stochastic model.
The flow field is solved in the dry case and the compressor performance is
analyzed in terms of; variation of air properties, characteristics of the operating
point, and consumed specific power. Performance change due to wet compression
is calculated. Parametric study has been performed to find out the effect of
important parameters on the compressor performance. These parameters include;
the injected coolant mass flow rate as a ratio of the dry air mass flow rate (injection
ratio), the DROPlet size, and the effect of DROPlet-DROPlet interaction.