Off-design operation is a generic terminology for many possible situations. I propose a classification as follow :
- operationnal off-design : operating conditions shift from the design specification. The modification can concerne the mean values and/or the fluctuation of the supply flow. (a modification of operating point is operational off-design ; a pulsating flow is an unsteady operational off-design) ;
- geometric off-design : geometry of the stage shift from its design definition ;
- functionnal off-design : the sign of the work exchange between the flow and the machine changes, such as when compressors used in turbine-like mode (free or load-controled windmilling, reverse flow...)
This classification is easily illustrated in a loading-to-flo-coefficients diagram () :
Figure 1 : classification of the categories of off-design functionning into a loading-to-flow coefficients diagram.
Three leading study cases are associated to the different off-design situations : operation of variable geometry radial turbines in steady and unsteady flows (geometric off-design), low-speed fans in load-controled windmilling operation (functional off-design) and centrifugal compressors near surge (operational off-design). Experimental, numerical, and low-order methods are applied.
- Steady operation :
The interaction between rotor and stator geometries is investigated, and secondary flows are analysed, in order to propose design recommendations.
Figure 2 : exemple of investigation of variable geometry stator with twisted blades - FineTurbo - Iso-surface of Q-criteria (from Emmanuelli & al., 2016).
Funding : partnership with Liebherr Aerospace.
- Unsteady operation :
Radial turbine stages are fed with a brutal variation of inlet conditions (step variation < 5ms) in order to analyse the transient. The quasi-static nature of the response is discussed for different geometric configuration of the stator.
Figure 3 : Evolution of the time-derivated pressure signal at stations B & C in the stage for the nominal opening configuration of the stator - Experimental data. An azimutal evolution of the attenuation of the pressure front exists.
The local analysis of the flows in low speed fans in non-conventional operating situation such as windmilling gives information about (i) relight capabilities of turbofans and (ii) design of reversible fans in the purpose of energy recovery systems. The use of diagrams helps understanding the progressive evolution of the functionning of a fan toward a turbine-like operating mode.
Figure 4 : theoretical operating line of a typical low-speed fan in a diagram, for two quadrants (from Binder & al., 2015).
Figure 5 : expected local evolution of the flow along the blade span for a progressive evolution from fan-like operation toward turbine-like operation (increase of ). Local co-existence of turbine mode and compressor mode is observed spanwise ; is the neutral radius (from Binder & al., 2015).
Funding : partnership with SAFRAN/Technofan.
Contribution to the understanding of stall inception is proposed through the detailled analysis of full-anulus sliding-mesh URANS simulations performed by Yannick Bousquet on a subsonic centrifugal compressor with a vaned diffuser. A test bench is developped for the production of validation data.
Figure 6 : visualization of the criteria applied on the instantaneous flow field at the inlet of a centrifugal compressor operating near surge. The development of a Kelvin-Helmoltz instability is observed (from Bousquet & al., 2015).
Funding : partnership with Liebherr Aerospace.
 Binder N., Courty-Audren S.K., Duplaa S., Dufour G., Carbonneau X., Theoretical Analysis of the Aerodynamics of low-speed Fans in free and load-controlled windmilling operation, Journal of Turbomachinery.
 Bousquet Y., Carbonneau X., Dufour G., Binder N., and Trebinjac I., Numerical Investigation of Kelvin-Helmholtz Instability in a Centrifugal Compressor Operating Near Stall, Journal of Turbomachinery
 Bousquet Y., Carbonneau X., Dufour G., Binder N., and Trebinjac I., Analysis of the Unsteady Flow Field in a Centrifugal Compressor from Peak Efficiency to Near Stall with Full-Annulus Simulations, International Journal of Rotating Machinery, vol. 2014, Article ID 729629, 11 pages. doi:10.1155/2014/729629
 Binder N., Garcia Benitez J., and Carbonneau X., Dynamic Response in Transient Operation of a Variable Geometry Turbine Stage : Influence of the Aerodynamic Performance, International Journal of Rotating Machinery, vol. 2013, Article ID 735321, 11 pages, 2013. doi:10.1155/2013/735321
 Carbonneau, X. and Binder, N. Performance Back-deduction from a Loading to Flow Coefficient Map : Application to Radial Turbine. (2012) Journal of Thermal Science, vol. 21 (n° 6). pp. 509-517. ISSN 1003-2169
 Binder, N. and Carbonneau, X. Performance of a Thrust Vectoring Solution for UAV. Journal of Propulsion and Power, vol. 28 (n° 5). pp. 1125-1129. ISSN 0748-4658
 Binder, N, Le Guyader, S. and Carbonneau, X. – Analysis of the variable geometry effect in radial turbines, Journal of Turbomachinery.
 Carbonneau, X. ; Binder, N. and Jamme, S. - Evaluation of the thrust recovery of an aircraft flap outflow valve – Journal of Aircraft – vol.47 no.5 (1473-1480) doi : 10.2514/1.47419.
 N. Binder, X. Carbonneau et P. Chassaing. Off-design consideration through the properties of some pressure-ratio line of radial inflow turbines. Int. J. of Rotating Machinery, 273296.
 Ortolan A., Courty-Audren SK., Binder N., Carbonneau X., and Challas F., Experimental and numerical flow analysis of low-speed fans at highly loaded windmilling conditions, ASME Turbo-Expo 2016, Accepted. To be presented.
 Emmanuelli, Ariane and Carboneau, Xavier and Bousquet, Yannick and Binder, Nicolas, Effect of Twisted Vanes on Leakage Losses in Variable Geometry Radial Turbines, (2016) In : 15th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC).
 Ortolan A., Carbonneau X., Binder N., Challas F., and Meauzé G., Innovative fan design for both high compressor and windmilling performance, 12th International Symposium on Experimental Computational Aerotermodynamics of Internal Flows, 13-16 July 2015, Genova, Italy
 Carbonneau X., Bousquet Y., Binder N., Belkouchi, B., Analysis of Variable Geometry Nozzle Flow with Twisted Vanes in Radial Turbines, ETC 2015.
 Bousquet Y., Carbonneau X., Dufour G., Binder N., and Trebinjac I., Numerical Investigation of Kelvin-Helmholtz Instability in a Centrifugal Compressor Operating Near Stall, ASME Turbo-Expo 2015
 Courty-Audren SK., Carbonneau X., Binder N., and Challas F., Comparaison des Méthodes Numériques Stationnaires et Instationnaires dans la Prédiction des Ecoulements Décollés – Application à un Ventilateur Subsoique en Autorotation, Congrès Français de Mécanique, Bordeaux, France.
 Courty-Audren SK., Binder N., Carbonneau X., and Challas F., Potential of Power Recovery of an Axial Fan in Windmilling Operation, 10th European Turbomachinery Conference, Lappeeranta, Finland.
 Carbonneau, Xavier and Binder, Nicolas Back deduction of the radial turbine map from a loading to Flow coefficient diagram. In : 14th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery (ISROMAC), 27 Feb - 02 Mar 2012, Honolulu, Hawaii, USA.
 Minck, Olivier and Binder, Nicolas and Cherrier, Olivier and Lamotte, Lucie and Pommier-Budinger, Valérie Fan noise analysis using a microphone array. In : Fan 2012 - International Conference on Fan Noise, Technology, and Numerical Methods, 18-20 Apr 2012, Senlis, France.
 Carbonneau, X. ; Binder, N. - Analysis of the pressure-ratio lines for radial turbine – 8th European Turbomachinery Conference, Graz.
 S. Le Guyader, N. Binder, X. Carbonneau et P. Chassaing. Back pressure effects on variable geometry turbine performances. Heat Transfer, Fluid Mechanics and Thermodynamics, 6th International Conference, Pretoria, South Africa.
 N. Binder, X. Carbonneau, P. Chassaing. Properties of some pressure-ratio line of radial inflow turbines and application to off-design considerations. 12th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery.
 S. Le Guyader, N. Binder, X. Carbonneau et P. Chassaing. Aerodynamic approach of a variable stator controllability for a small radial turbine. 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Sun City, South Africa.
 X. Carbonneau, N. Binder et P. Chassaing. De la conception à la réalisation d’un turboréacteur de 100 daN de poussée destiné à la propulsion de drones. 41ème Colloque d’Aérodynamique Appliquée, Lyon.
 N. Binder, X. Carbonneau, et P. Chassaing. Aerodynamic moment measurements on stator blades of a small dimension variable geometry radial turbine stage. 2nd EVI-GTI Conference, Dubrovnik.
 N. Binder, X. Carbonneau, et P. Chassaing. Influence of a variable guide vane nozzle on the design parameters of a radial turbine stage. 6th European Turbomachinery Conference (ETC 6), Lille, France.
 N. Binder, X. Carbonneau, et P. Chassaing. Volute outlet conditions study by measurements on the stator blades of a small dimension radial turbine stage, 4th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Cape Town, South Africa.
 Caractérisation de l’écoulement dans un étage de turbine centripète à géométrie variable, XVeme Congrès Français de Mécanique, Nancy, France.