[
home]
[
Personal Program]
[
Help]
tag
16:20
20 mins
Optimal Design of ORC Turbine Blades under Geometric and Operational Uncertainties
Nassim Razaaly, Giacomo Persico, Pietro Marco Congedo
Session: Session 5A: Turbines-Design & flow simulations
Session starts: Tuesday 10 September, 16:00
Presentation starts: 16:20
Room: Olympia
Nassim Razaaly (INRIA)
Giacomo Persico (Politecnico di Milano)
Pietro Marco Congedo (INRIA)
Abstract:
Typical energy sources for Organic Rankine Cycle (ORC) power systems feature variable
heat load and turbine inlet/outlet thermodynamic conditions. The use of organic compounds
with heavy molecular weight introduces uncertainties in the fluid thermodynamic modeling
and complexity in the turbomachinery aerodynamics, with supersonic flows and strong
shocks, which grow in relevance in the aforementioned off-design conditions. These features
also depend strongly on the local blade shape, which can be influenced by the geometric
tolerances of the blade manufacturing.
This study presents a Robust Optimization (RO) analysis on a typical supersonic nozzle
cascade for ORC applications under the combined effect of uncertainties associated to
operating conditions, fluid parameters, and geometric tolerances. The geometric variability is
described by a finite Karhunen-Loeve expansion representing a non-stationary Gaussian
random field, entirely defined by a null mean and its autocorrelation function. Real-gas effects
are modeled through the use of the polytropic improved Peng-Robinson equation of state
implemented within the open-source CFD solver SU2.
The blade is parametrized by moving B-splines control points, allowed to be displaced in the
direction locally normal to the blade. Different statistics, according to the RO formulation
chosen, of the Quantity of Interest (QoI) are minimized in the framework of mono-objective
optimization, constraining the mean mass flow-rate to be within a small range centered at the
baseline value, at nominal conditions. Linear combination
of mean and standard deviation of the QoI (equivalent to the popular Taguchi multi-objective
optimization) are considered, as well a linear combination of mean and high quantile.
The robust optimal blades are compared to the deterministic optimal shape. The impact of the
choice of the RO formulation on the final blades is highlighted.