Publications

@proceedings{945,

title = {Evaluation of Unsteady CFD Models Applied to the Analysis of a Transonic HP Turbine Stage},

author = {Matteo Giovannini and Michele Marconcini and Andrea Arnone and Francesco Bertini},

isbn = {978-952-265-385-7},

year  = {2013},

date = {2013-04-01},

journal = {10th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics (ETC 2013)},

pages = {840-853},

address = {Lappeenranta, Finland},

abstract = {This paper presents an efficient textquotedblleftPhase-Laggedtextquotedblright method developed for turbomachinery applications. The method is based on the Generalized-Shape-Correction model. Moving averages techniques as well as double-passage domain formulation were adopted in order to reduce memory requirements and improve the model robustness. The model was used to evaluate the aerodynamic performance of the high pressure transonic turbine stage CT3, experimentally studied at the von Karman Institute for Fluid Dynamics within the EU funded TATEF2 project. Results are discussed and compared with both the available experimental data and the results obtained by means of both steady and unsteady scaled Full-Annulus approaches. Computational requirements of the GSC model are evaluated and presented showing that nowadays unsteady results can be reached at an affordable computational cost.},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}

@proceedings{935,

title = {A Critical Numerical Review of Loss Correlation Models and Smith Diagram for Modern Low Pressure Turbine Stages},

author = {Francesco Bertini and E Ampellio and Michele Marconcini and Matteo Giovannini},

url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=1776565},

doi = {10.1115/GT2013-94849},

isbn = {978-0-7918-5523-2},

year  = {2013},

date = {2013-01-01},

journal = {ASME Turbo Expo 2013: Turbine Technical Conference and Exposition},

volume = {6B: Turbomachinery},

pages = {V06BT37A018-; 14 pages},

publisher = {ASME},

address = {San Antonio, TX, USA, June 3–7},

abstract = {The Smith diagram, originally published in 1965, has been largely exploited as a preliminary design (PD) tool for axial turbines. Currently, it is applied to aeronautical Low Pressure Turbines (LPTs) in order to define basic characteristics during the feasibility study and to compare different configurations. The Smith diagram represents a correlation of stage performance (η) as function of flow coefficient (φ) and loading factor (ψ), but it does not take into account the effects of some important input parameters (single contributions of loss, Reynolds number, Aspect Ratio, Rotor Tip Clearance (RTC)) and does not report some key design outputs (deflections (δ), profile weights and stresses), which have also a direct relation with the configuration position on the Smith diagram. This study employs meanline analyses incorporating two traditional loss correlation models used in the turbine field (Craig and Cox, Kacker and Okapuu) to compare results with the original Smith diagram. The correlation approach allows one to obtain other important multidisciplinary information (primarily aero-mechanical) which was previously absent, which leads to some strategic design achievements. The investigation process is based on a reference two-stage turbine properly set to match specific operating points on the Smith diagram. Several three-dimensional blade geometries have been designed and then detailed 3D CFD analyses have been performed in order to acquire confidence with respect to the meanline results. This research adds additional important information for turbine module design to the Smith chart and allows for a numerical revision of the diagram itself, fine tuning it with data obtained from the analyses of modern blades optimized for high stage performance. Finally numerically-based loss predictors, broadly applicable to LPTs during optimization procedures before detailed CFD analyses, are presented and discussed.},

note = {ASME paper GT2013-94849},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}

@proceedings{953,

title = {A Path Towards the Aerodynamic Robust Design of Low Pressure Turbines},

author = {Francesco Bertini and Martina Credi and Michele Marconcini and Matteo Giovannini},

url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1694976&resultClick=1},

doi = {dx.doi.org/10.1115/GT2012-69456},

isbn = {978-0-7918-4474-8},

year  = {2012},

date = {2012-06-01},

journal = {ASME Turbo Expo 2012: Turbine Technical Conference and Exposition},

volume = {8: Turbomachinery, Parts A, B, and C},

pages = {pp. 1497-1507},

publisher = {ASME},

address = {Copenhagen, Denmark, June 11–15, 2012},

abstract = {Airline companies are continuously demanding lower-fuel-consuming engines and this leads to investigating innovative configurations and to further improving single module performance. In this framework the Low Pressure Turbine (LPT) is known to be a key component since it has a major effect on specific fuel consumption (SFC). 

 

Modern aerodynamic design of LPTs for civil aircraft engines has reached high levels of quality, but new engine data, after first engine tests, often cannot achieve the expected performance. Further work on the modules is usually required, with additional costs and time spent to reach the quality level needed to enter in service. The reported study is aimed at understanding some of the causes for this deficit and how to solve some of the highlighted problems. 

 

In a real engine, the LPT module works under conditions which differ from those described in the analyzed numerical model: the definition of the geometry cannot be so accurate, a priori unknown values for boundary conditions data are often assumed, complex physical phenomena are seldom taken into account, operating cycle may differ from the design intent due to a non-optimal coupling with other engine components. Moreover, variations are present among different engines of the same family, manufacturing defects increase the uncertainty and, finally, deterioration of the components occurs during service. 

 

Research projects and several studies carried out by the authors lead to the conclusion that being able to design a module whose performance is less sensitive to variations (Robust LPT) brings advantages not only when the engine performs under strong off-design conditions but also, due to the abovementioned unknowns, near the design point as well. 

 

Concept and Preliminary Design phases are herein considered, highlighting the results arising from sensibility studies and their impact on the final designed robust configuration. Module performance is afterward estimated using a statistical approach.},

note = {ASME paper GT2012-69456},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}

@proceedings{921,

title = {Aerodynamic Investigation of a High Pressure Ratio Turbo-Expander for Organic Rankine Cycle Applications},

author = {Michele Marconcini and Filippo Rubechini and Andrea Arnone and Alberto Scotti Del Greco and Roberto Biagi},

url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1695157},

doi = {10.1115/GT2012-69409},

isbn = {978-0-7918-4474-8},

year  = {2012},

date = {2012-01-01},

journal = {ASME Turbo Expo 2012: Turbine Technical Conference and Exposition},

volume = {8: Turbomachinery, Parts A, B, and C},

pages = {847-856},

publisher = {ASME},

address = {Copenhagen, Denmark, 11-15 June},

abstract = {The design of radial-inflow turbines usually relies on one-dimensional or mean-line methods. While these approaches have so far proven to be quite effective, they can not assist the designer in coping with some important issues, such as mechanical integrity and complex flow features. Turbo-expanders are in general characterized by fully three-dimensional flow fields, strongly influenced by viscous effects and passage curvature. In particular, for high pressure ratio applications, such as in organic Rankine cycles, supersonic flow conditions are likely to be reached, thus involving the formation of a shock pattern which governs the interaction between nozzle and wheel components. The nozzle shock waves are periodically chopped by the impeller leading edge, and the resulting unsteady interaction is of primary concern for both mechanical integrity and aerodynamic performance. This work is focused on the aerodynamic issues, and addresses some key aspects of the CFD modelling in the numerical analysis of turbo-expanders. Calculations were carried out by adopting models with increasing level of complexity, from the classical steady-state approach to the full-stage, time-accurate one. Results are compared in details, and the impact of the computational model on the aerodynamic performance estimation is discussed.},

note = {ASME paper GT2012-69409.},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}

@proceedings{RSADCG11,

title = {Aerodynamic Redesigning of an Industrial Gas Turbine},

author = {Filippo Rubechini and Andrea Schneider and Andrea Arnone and Federico Dacc `a and C Canelli and P Garibaldi},

url = {http://link.aip.org/link/abstract/ASMECP/v2011/i54679/p1387/s1},

doi = {dx.doi.org/10.1115/GT2011-46258},

isbn = {978-0-7918-5467-9},

year  = {2011},

date = {2011-01-01},

journal = {ASME Turbo Expo},

volume = {7: Turbomachinery, Parts A, B, and C},

pages = {1387-1394},

publisher = {ASME},

address = {Vancouver, BC, Canada, 6-10 June},

abstract = {This paper deals with the aerodynamic redesigning of a four-stage heavy-duty gas turbine. Traditional design tools, such as through-flow methods, as well as more sophisticated tools, such as three-dimensional RANS computations, were applied in subsequent steps according to a given hierarchical criterion. Each design or analysis tool was coupled with modern optimization techniques, and the overall redesign procedure relies on a neural-network-based approach aimed at maximizing the turbinetextquoterights power output while satisfying geometrical and mechanical constraints. A detailed description of the redesign procedure is provided, and the aerodynamic characteristics of the optimized geometry are discussed and compared to the original ones.},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}

@proceedings{948,

title = {Calculation of Steady and Periodic Unsteady Blade Surface Heat Transfer in Separated Transitional Flow},

author = {Roberto Pacciani and Filippo Rubechini and Andrea Arnone and E Lutum},

url = {http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleid=1608834&resultClick=3},

doi = {10.1115/GT2010-23275},

isbn = {978-0-7918-4399-4},

year  = {2010},

date = {2010-06-01},

journal = {ASME Turbo Expo 2010: Power for Land, Sea, and Air},

volume = {4: Heat Transfer, Parts A and B},

pages = {891-900},

publisher = {ASME},

address = {Glasgow, UK, June 14–18, 2010},

abstract = {In this work aerothermal investigations of a highly loaded HP turbine blade are presented. The purpose of such investigations is to improve the physical understanding of the heat transfer in separated flow regions, with the final goal of optimizing cooling configurations for aerodynamically highly loaded turbine designs. The analysis is focused on the T120 cascade, that was recently tested experimentally in the framework of the European project AITEB-2 (Aero-thermal Investigation of Turbine Endwalls and Blades). Such a cascade has a relatively low solidity that is responsible for the formation of a laminar separation bubble on the suction side of the blade. Separated-flow transition and transonic conditions downstream of the throat result in a flow configuration that is very challenging for traditional RANS solvers. Moreover, the separated flow transition pattern was found to have a strong impact on both the aerodynamic and thermal aspects. The study was carried out using a novel three-equation, transition-sensitive, turbulence model. It is based on the coupling of an additional transport equation for the laminar kinetic energy to the Wilcox k–ω model. Such an approach allows one to take into account the increase of the non-turbulent fluctuations in the pre-transitional and transitional region. Comprehensive aerodynamic and heat transfer measurements were available for comparison purposes. In particular, heat transfer measurements cover different Mach and Reynolds numbers, in both steady and periodic unsteady inflow conditions. A detailed comparison between measurements and computations is presented, and the impact of transition-related aspects on the surface heat transfer is discussed.},

note = {Paper No. GT2010-23275},

keywords = {},

pubstate = {published},

tppubtype = {proceedings}

}