1,720,966 research outputs found
Efficiency and Stall Margin Enhancements in Transonic Compressor Rotors Using Synthetic Jets: A Numerical Investigation
No full textAssessment of Morphing Wings on the Rear Empennages of a Tiltrotor
Get PDFCurrent trends in the design of transport aircraft have shown that in order to be economically viable and competitive
it is necessary to investigate technologies that can give an improvement in performance and a reduction in the fuel
consumption. The present study is aimed at investigating the effect of “Morphing Wings” on the aerodynamic
performance of the rear empennages of a new generation tiltrotor called ERICA (Enhanced Rotorcraft Innovative
Concept Achievement). Actually, morphing wings may offer significant potential benefits over conventional rigid
wings. In particular, the adaptive wing camber was selected as the most promising solution for the present work.
Specifically, the “finger concept” was chosen as the morphing technique due to its simplicity, reliability, and ability
to fulfill the strict safety rules. A series of computational fluid dynamic analyses at Re = 14x106 were performed in
order to obtain the best morphing shape of the “finger” elements in terms of aerodynamic efficiency and maximum.
A remarkable increment of lift coefficient slope and an overall aerodynamic efficiency enhancement was achieved
with respect to the baseline
Helicopter fuselage aerodynamic data fitting using multivariate smoothing thin plate splines
No full textSmoothing thin plate splines, a nonparametric statistical technique for multivariate data fitting, were investigated to predict the aerodynamic performance (output variables) of a generic 3D helicopter fuselage as functions of the pitch angle and of some geometric parameters describing their shape (input variables). In order for the smoothing thin plate splines to be properly applied, a database needed to be constructed containing pairs of input–output variables. To this purpose, a sample helicopter fuselage was chosen and 14 variants were generated modifying the geometric parameters; then, the pertinent lift, drag and pitching moment coefficients were obtained via computational fluid dynamics. The smoothing thin plate splines model was built excluding from the database one fuselage at a time and was then used to determine the aerodynamic performance of the left out configuration: finally, the obtained results were compared with those coming from direct computational fluid dynamics simulations over the same fuselage. The prediction capability of the smoothing thin plate splines models has been confirmed for all the analyzed fuselage geometries
Numerical Assessment of Pneumatic Devices on the Wing/Fuselage Junction of a Tiltrotor
Get PDFThe present study aimed at investigating the effect of boundary layer control techniques, in particular suction and blowing, on the aerodynamic performance of the wing/fuselage junction of a tiltrotor. To this purpose, a series of numerical analyses at Re=14×〖10〗^6 were performed in order to obtain the best shape and location of the suction/blowing slot in terms of aerodynamic efficiency and maximum lift gain with respect to the baseline. A preliminary cost-benefit analysis was also carried out by comparing the increased on board installed power required by these systems with the estimated reduction in the propulsive power due to improved aerodynamic characteristics of the aircraft
Airfoil Data Fitting using Multivariate Smoothing Thin Plate Splines
No full textSmoothing thin plate splines, a fitting technique based on a rigorous roughness penalty approach, have been recently investigated as a promising tool for bivariate interpolation of aerodynamic data. In this paper, this technique is implemented and extended to multivariate fitting. In particular, the method is applied for estimating the aerodynamic polars of well-known two-dimensional symmetrical and nonsymmetrical airfoils as functions of some geometric parameters describing the airfoil shape and a further variable defining the flow regime (either the Mach or the Reynolds number). Therefore, the simultaneous influence of five independent variables on three responses (lift, drag, and pitching moment coefficients) is investigated. To this purpose, a large database is generated via numerical simulations (using a validated flow solver) containing all information required to build a reliable response surface. Then, the model is built and its performance validated by performing queries on complete aerodynamic polars at various flow regime conditions of a series of airfoils not included into the database. Results show a very good matching between predicted and calculated curves, thus demonstrating the remarkable predictive capability of the implemented tool
Performance Optimization of a Heavy Class Helicopter Engine Installation Using Genetic Algorithms Coupled With CFD Simulations
Get PDFAerodynamic design and optimization of engine installation is a pivotal part of the helicopter design process. To this
purpose, an adaptive problem-independent and reliable optimization methodology would be particularly valuable for
accomplishment of such goal. The application of advanced evolutionary algorithms coupled with CFD solvers for
the accurate flow solution of validated numerical models represents a very powerful tool for the parametric design
and optimization of engine installation components. Within the JTI Clean Sky FP7 project “HeavyCopter” the
consortium constituted by the University of Padova (UNIPD) and the spin-off company HIT09 developed an
automatic optimization loop based on an in-house genetic algorithm called GeDEA, and applied it to engine
installation design of a heavy-class helicopter. This paper illustrates the application of the above mentioned
optimization loop both at cruise and hover reference flight conditions for such a helicopter. The algorithm pursues
the minimization of the total pressure losses at the air intakes while keeping the flow distortion at the engine inlet at
the lowest level; regarding the exhausts, the back-pressure is minimized in order to increase the power output of the
engine while preserving the entrainment ratio. The results highlight significantly improved performance margins
with respect to the baseline both for intakes and exhaust
Efficiency and Stall Margin Enhancements in Transonic Compressor Rotors Using Synthetic Jets: A Numerical Investigation
No full textSeveral passive and active techniques were studied and developed by compressor designers with the aim of improving the aerodynamic behavior of compressor blades by reducing, or even eliminating, flow separation. Fluidic-based methods, in particular, have been investigated for a long time, including both steady and unsteady suction, blowing and oscillating jets. Recently, synthetic jets (zero mass flux) have been proposed as a promising solution to reduce low-momentum fluid regions inside turbomachines. Synthetic jets, with the characteristics of zero net mass flux and non-zero momentum flux, do not require a complex system of pumps and pipes. They could be very efficient because at the suction part of the cycle the low-momentum fluid is sucked into the device, whereas in the blowing part a high-momentum jet accelerates it. To the authors’ knowledge, the use of synthetic jets has never been experimented in transonic compressor rotors, where this technique could be helpful (i) to reduce the thickness and instability of blade suction side boundary layer after the interaction with the shock, and (ii) to delay the arising of the low-momentum region which can take place from the shock-tip clearance vortex interaction at low flow operating conditions, a flow feature which is considered harmful to rotor stability. Therefore, synthetic jets could be helpful to improve both efficiency and stall margin in transonic compressor rotors. In this paper, an accurate and validated CFD model is used to simulate the aerodynamic behavior of a transonic compressor rotor with and without synthetic jets. Four technical solutions were evaluated, different for jet position and velocity, and one was investigated in detail
Efficient Aerodynamic Optimization of an Impulse Turbine Rotor Cascade
No full textPaper IMECE2009-10115, Lake Buena Vista, Florida, USA
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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