THE WORK BEHIND THE METHODS
PUBLICATIONS
The peer-reviewed work behind the methods:
in aerospace, energy, green building and maritime engineering.
01
Smart Mobility Aviation Multimodal Connectivity and Interoperability. Future Operative Scenarios Design and Modelling
G. A. Misté, A. Dal Monte, D. Papale, E. Benini, F. Lo Cicero, G. Troiano, C. Fiorillo
POLARIS Innovation Journal (internal journal of Leonardo Spa), Vol. 39, 2019
MORE INFO
The global scenario of transport modes is rapidly changing. The development of hybrid/electric propulsion aircrafts is progressing in parallel with the evolution of electrical technologies. Starting from 2035, a big reduction of the energy needed for air transport is expected (approximately 20% compared to conventional aircraft), in order to respond to increasingly stringent environmental regulations issued by national and international Bodies/Entities or Associations. In a future context of advanced intermodal and multimodal transport system, particular importance will be given by the regional connections performed by fixed wing aircraft able to manage trips with a “door to door” time within 4/5 hours. The article presents a new way of modelling possible future operational scenarios (2035+) for regional fixed-wing aircraft incorporating hybrid/electric propulsion technologies, based on the collaboration between Leonardo Aircraft and the University of Padova in the frame of the PROSIB research project. The aim is to show how the new hybrid aircraft connections could coexist and improve the current and future networks of high-speed train, highways, commercial aircraft operations, through an innovative methodology able to estimate overall travel time and passengers transported in the whole European context. Two case studies representing the European intermodal/multimodal network are shown in order to illustrate the potential of the model.
02
Design Evaluation and Performance Assessment of Rotorcraft Technology by 2050
J. Stevens, E. Rademaker, C. Scullion, S. Vouros, N. Van Oosten, E. Benini, G. A. Misté, G. Venturelli
European Rotorcraft Forum, September 2019
MORE INFO
The extended Clean Sky Joint Technology Initiative (JTI) within the EU Horizon 2020 Framework Programme proposes to introduce a number of concept aircraft and rotorcraft to replace reference technology counterparts at different time scales (2020/2035/2050). This Clean Sky 2 (CS2) promotes the importance of those concept configurations and their application in the future. An increasing global demand within and outside the European Union (EU) for an efficient air mobility and transportation system (i.e. more flexible, resilient, effective and affordable), and future projected growth for its application, will lead to the requirement for development of highly optimised transportation solutions.
Within CS2, the project DEPART2050 (Design Evaluation and Performance Assessment of Rotorcraft Technology by 2050) aims to undertake the environmental and socio-economic assessments for two fast rotorcraft technologies, being the tilt rotor aircraft and the compound rotorcraft under development by the Original Equipment Manufacturers (OEMs), the NGCTR and the Racer. Such fast rotorcraft with improved capabilities (higher payload, range and speed) will have an inherent advantage. This will enable the utilisation of smaller airports (as they can operate from shorter runways) and optimally located heliports. The objectives of the project work will be to undertake at airport level and at Air Transport System (ATS) level, assessments of environmental (emissions and noise) and mobility (connectivity and productivity) improvements that may be accrued through replacement of reference helicopter technology over the designated time scales. The assessments will be made for a selected number of mission scenarios: Search and Rescue, Oil and Gas, Emergency Medical Service, Passenger Air Transport and Cargo Transport.
To widen the scope of the DEPART2050 project, additional assessments will be performed for two generic fast rotorcraft: a tilt rotor aircraft and a compound rotorcraft. These generic rotorcraft, having been defined by the DEPART2050 project partners, are different from and do not represent the ones under development by the OEMs within CS2 (NGCTR and Racer). Within the DEPART2050 project so far, the rotorcraft configurations have been defined and the models set up. The assessment metrics and missions have been further detailed. Initial assessments have been performed for fuel consumption, exhaust gas emissions, noise impact and mobility impact, showing that the set-up is viable and that results are in line with expectations. Considerable reductions have been found for fast rotorcraft relative to conventional helicopters, both in fuel consumption and CO2 emission per passenger-kilometre, as well as in absolute travel time. But it also has become clear that more work is required to come to actual and final conclusions. The project will run till late 2021 and more results will become available in due time.
03
Testing of a Long-Burning-Time Paraffin-Based Hybrid Rocket Motor
E. Paccagnella, M. Santi, A. Ruffin, F. Barato, D. Pavarin, G. A. Misté, G. Venturelli, N. Bellomo
Journal of Propulsion and Power, Vol. 35(2): 432-442, March 2019
MORE INFO
One of the main issues that prevents the widespread use of hybrid propulsion is the low regression rate of classical hybrid fuels. Recently, paraffin-based fuels have been proposed as a viable solution; however, concerns about paraffin thermomechanical properties have often been seen as a possible showstopper. A small-scale hybrid rocket, able to burn hydrogen peroxide and paraffin wax for an extended time, has been designed, built, and tested in order to investigate the suitability of paraffin wax as a hybrid fuel for actual missions. The motor has a nominal burning time of 80 s, which is compatible with the majority of the missions performed by rocket motors. The motor has been tested successfully, demonstrating that paraffin can be used on real missions. Two different types of paraffin were used: type A and type B, which have regression rates of 1.45 and 1.07 mm/s, respectively, at a reference oxidizer mass flux of 50 kg/m2*s and at a reference pressure of 15 bar. Moreover, temperature measurements inside the fuel grain demonstrated the liquid layer theory to be valid. An instrumented nozzle has also been used to better investigate the thermal behavior of the nozzle assembly.
04
Development of a Flow Control Valve for a Throttleable Hybrid Rocket Motor and Throttling Fire Tests
A. Ruffin, M. Santi, E. Paccagnella, F. Barato, N. Bellomo, G. A. Misté, G. Venturelli, D. Pavarin
Joint Propulsion Conference, Cincinnati, USA, July 2018. DOI: 10.2514/6.2018-4664
MORE INFO
Hybrid rockets technology is growing in interest in recent years. The main reasons of this renewed interest is that hybrid rocket motors are simple, safe to develop and operate, reliable, green and less expensive than traditional propulsive technologies (solids and liquids). Another peculiar feature of hybrid rocket motors is throttleability, i.e. the ability to control the thrust level on demand, and this, in hybrids, is achieved by controlling the oxidizer mass flow to the combustion chamber, hence the need for a flow control valve.
At University of Padova, the Hybrid Propusion Group has been developing lab-scale hybrid rocket motors that are particularly suited to be implemented with a flow control valve, using HTP, a monopropellant, as oxidizer, and a catalytic bed injection which is not affected by the problems of atomization of an injection plate.
The flow control valve presented in this paper exploits the cavitation on an actuated pintle in order to choke the mass flow. The advantages of such a device, which is called variable area cavitating venturi, are insensitivity of the mass flow to the downstream pressure variation and linearity of the mass flow with the throat area.
The paper presents the design phase of the flow control valve and its static and dynamic characterization achieved during cold flow tests. Moreover throttling fire tests are presented in order to understand the throttling behavior of our lab-scale test motor.
05
Spatial Distribution Study of Sweeping Jet Actuators along the Spanwise Direction in an Aircraft Wing
A. Mancini, A. Dal Monte, E. Benini
Aerospace Science and Technology, 2018
MORE INFO
Fluid dynamic actuators play a central role among the devices adopted to increase the aerodynamic performance of commercial wings. Specifically, sweeping jets allow to delay the boundary layer separation and improve aerodynamic efficiency using oscillatory flow on the wing suction side. The present work discloses different numerical analysis with the purpose of investigating the effects of the spanwise distribution on aerodynamic performances: first the behaviour of a sweeping jet was studied in a 2D numerical analysis, next it was embedded in a commercial wing and a 3D analysis was carried out. Finally, the effects of the spanwise distribution of multiple sweeping jets are discussed; furthermore, the effects of the actuator are also presented considering the formation of vortices in the flap suction side zone and their development in the wake. An optimal distribution has been found and it shows a marked enhancement in the lift to drag ratio respect to the other configurations.
06
Development and Testing of a Long Burning Time Lab-scale Paraffin-based Hybrid Rocket Motor
M. Santi, E. Paccagnella, A. Ruffin, F. Barato, D. Pavarin, G. A. Misté, G. Venturelli, N. Bellomo
53rd AIAA/SAE/ASEE Joint Propulsion Conference Atlanta, USA, July 2017 https://arc.aiaa.org/doi/10.2514/6.2017-4829
MORE INFO
Hybrid rocket motors have several potential advantages with respect to current used propulsion systems (i.e. solids and liquids): simplicity, safety, reliability, environmental friendliness, lower cost. One of the main issues that prevents the widespread use of hybrid propulsion is the low regression rate of classical hybrid fuels. Recently, paraffin based fuels have been proposed as a viable solution thanks to their high regression rate due to the entrainment of small fuel droplets as added mass transfer mechanism. However, concerns about paraffin thermomechanical properties have often been seen as a possible showstopper.
To investigate the suitability of paraffin wax as a hybrid fuel for actual missions, a small-scale hybrid rocket able to burn for extended time has been designed, built and tested. The motor has a nominal burning time of 80 seconds, compatible with the majority of missions performed by rocket motors. The motor has been tested successfully demonstrating that paraffin can be used on practical missions. Moreover, the liquid layer theory has been shown to be valid thanks to temperature measurements inside the fuel grain.
Other tests have been performed with an instrumented nozzle to better investigate the thermal behavior of the nozzle assembly.
07
Development of a Cavitating Pintle for a Throttleable Hybrid Rocket Motor
A. Ruffin, F. Barato, M. Santi, E. Paccagnella, N. Bellomo, G. A. Misté, G. Venturelli, D. Pavarin
7th European Conference For Aeronautics and Aerospace Sciences (Eucass), Milan, July 2017
MORE INFO
Hybrid rocket motors have several potential advantages respect to current used propulsion systems (i.e. solids and liquids) like simplicity, safety, reliability, environmental friendliness, lower cost. A particular positive feature of hybrid rockets is the possibility to control the thrust level operating only on the oxidizer mass flow. Thanks to this it is possible to develop a relatively simple propulsion system that is throttleable on demand without the complex mixture ratio control and related hardware of a liquid system. In the past University of Padua has developed a lab-scale hybrid rocket motor that can be throttled at few different discrete levels with the use of parallel feedlines. To give the possibility of having a continuous throttling capability a new mass flow control has been developed recently. The mass flow control make use of a cavitating pintle. The cavitating pintle acts as a cavitating venturi in order to choke the mass flow and make it independent of downstream pressure. The pintle is used to change the venturi throat area and consequently varying the oxidizer mass flow keeping a constant upstream pressure. The paper presents the design of the cavitating pintle and the experimental campaign composed by cold tests followed by hot fire tests of the lab scale hybrid rocket.
08
Kriging-assisted design optimization of S-shape supersonic compressor cascades
G. Venturelli, E. Benini
Aerospace Science and Technology. 58. 275-297. 10.1016/j.ast.2016.08.021
MORE INFO
In this paper, multi-objective design optimization of a supersonic compressor cascade was dealt with. The geometry considered was an S-shaped 2D cascade developed and tested at DLR (DLR-PAV-1.5), operating under unique incidence and inlet Mach number equal to 1.5 so as to develop approximately a static pressure ratio of 2. In such conditions, the cascade shows a strong lambda shock- boundary layer interaction. Methodology included the use of an in-house Kriging-assisted evolutionary algorithm driving an iterative loop which includes a parametric code for geometry representation and the ANSYS Fluent© solver for flow calculation. Cascade optimization was carried out by varying the shapes of both the suction and the pressure sides while maintaining the unique incidence condition using an iterative CFD-based procedure. The objectives were to minimize the cascade total pressure losses and to maximize the static pressure ratio using a Pareto ranking criterion. Results showed that loss coefficient could be reduced by 25% and the static pressure ratio could be improved by 6.5% as a results of a decrease in the pre-shock Mach number by virtue of an extended pre-compression mechanism that involves the entire suction surface upstream of the passage shock.
09
Variable-Speed Rotor Helicopters: Performance Comparison between Continuously Variable and Fixed-Ratio Transmissions
G. A. Misté, E. Benini
Journal of Aircraft, 2016, Vol. 53: 1189-1200. DOI: 10.2514/1.C032744
MORE INFO
Variable-speed rotor studies represent a promising research field for rotorcraft performance improvement and fuel-consumption reduction. The problems related to employing a main rotor variable speed are numerous and require an interdisciplinary approach. There are two main variable-speed concepts, depending on the type of transmission employed: fixed-ratio transmission and continuously variable transmission rotors. The impact of the two types of transmissions upon overall helicopter performance is estimated when both are operating at their optimal speeds. This is done by using an optimization strategy able to find the optimal rotational speeds of the main rotor and turboshaft engine for each flight condition. The process makes use of two different simulation tools: a turboshaft engine performance code and a helicopter trim simulation code for steady-state level flight. The first is a gas turbine performance simulator (called TSHAFT), developed and validated at the University of Padova. The second is a simple tool used to evaluate the single blade forces and integrate them over the 360 deg revolution of the main rotor, and thus to predict an average value of the power load required by the engine. The results show that the fixed-ratio transmission does not present significant performance differences compared to the continuously variable transmission for a wide range of advancing speeds. However, close to the two conditions of maximum interest (that is, hover and cruise forward flight), the discrepancies between the two transmission types become relevant: in fact, engine performance is found to be penalized by fixed-ratio transmission, proving that significant fuel reductions can be obtained only by employing the continuously variable transmission concept. In conclusion, fixed-ratio transmission is a good way to reduce fuel consumption at intermediate advancing speeds; continuously variable transmission advantages become relevant only near hover and high-speed cruise conditions.
10
A Methodology for Determining the Optimal Rotational Speed of a Variable RPM Main Rotor/Turboshaft Engine System
G. A. Misté, A. Garavello, E. Benini, M. Gonzalez-Alcoy
Journal of the American Helicopter Society (AHS), Volume 60, Number 3, July 2015
MORE INFO
Variable speed rotors represent an innovative research field for the development of new rotorcraft designs. Issues related to employing a main rotor variable speed are numerous and require an interdisciplinary approach. For this reason, a preliminary effort has been made to understand the performance implications of coupling helicopter trim and turboshaft engine simulations. Following this, two different models of a UH-60 Black Hawk helicopter and a GE T700 turboshaft engine are implemented and validated against experimental data. Then, an optimization algorithm is employed to find the optimal main rotor speed with the aim of minimizing fuel consumption. Different simulation cases are analyzed to quantify the benefits related to the optimal main rotor speed depending on flight condition, altitude, and helicopter gross weight. It is found that coupling both the helicopter and engine model is necessary to adequately determine the correct rotational speed corresponding to minimum fuel consumption. More than 10% fuel saving is shown to be feasible. The results obtained employing a variable speed main rotor are broadly discussed, and future possible applications of the methodology are suggested.
11
Variable Speed Rotor Helicopters: Optimization of Main Rotor – Turboshaft Engine Integration
G. A. Misté
Ph.D. thesis, University of Padova, 2015
MORE INFO
Record: https://www.research.unipd.it/handle/11577/3424123
Variable speed rotors (VSRs) represent an innovative research field for the development of new rotorcraft designs. The possibility to change the rotational speed of a helicopter rotor, as a function of the specific flight condition, makes it possible to achieve optimum performance and relevant fuel consumption reductions. However, issues related to employing a main rotor variable speed are numerous and require an interdisciplinary approach. The present study represents the first effort in the open literature aimed at understanding the performance implications of coupling helicopter trim and turboshaft engine simulations for a VSR model.
A gas turbine simulation code, TSHAFT, and a helicopter performance tool, TCOPTER, have been implemented in order to be able to carry out the coupled analysis. Following this, the VSR concept has been tested on a real helicopter case: the models of a UH-60 Black Hawk helicopter and a GE T700 turboshaft engine have been implemented and validated against experimental data. Subsequently, an optimization routine has been employed to find the optimal main rotor speeds which minimize fuel consumption in different helicopter flight conditions.
Two different approaches to VSRs have been analyzed: the former employing a traditional fixed ratio transmission (FRT), the latter assuming a continuously variable transmission (CVT). In the FRT case, since the turbine and main rotor speeds are in a fixed ratio, the optimal speed has been calculated as the best compromise between optimal main rotor speed and optimal turbine speed. In the CVT case, the study has been carried out assuming that main rotor and turbine speeds were free to rotate at their optimal speeds.
Different simulation cases have been analyzed in order to quantify the benefits related to the optimal main rotor speed depending on flight conditions, altitude and helicopter gross weight. It has been found that coupling both the helicopter and engine model is important to adequately determine the correct rotational speed corresponding to minimum fuel consumption. More than 13% fuel saving has been shown to be feasible.
Finally, possible improvements to the VSR concept have been studied. In particular, a trial has been made to redesign the power turbine of the GE T700 in order to improve the efficiency of the engine in a wide speed variation range.
12
Genetic Inspired Computing for Multi-objective optimization: Comparison Berween Pure and Surrogate-Assisted Evolutionary Algorithms on Multidimensional Test Functions
E. Benini, G. Venturelli, L. Lanieski-Wolk
Proc. Third International Conference on Advances in Computing, Communications ICACCI (2014). Delhi, India, 24-27 September, 2014
MORE INFO
In this paper, a comparison between a “pure” genetic algorithm (GeDEA-II) and a surrogate-assisted algorithm (ASEMOO) is carried out using up-to-date multiobjective and multidimensional test functions. The experimental results show that the use of surrogates greatly improves convergence when both two- and three-objective test cases are dealt with. However, its convergence capabilities depend on how the surrogate can have an accurate picture of the fitness function landscape and seem to decrease as the number of the objective increases from two to three. On the contrary, a pure genetic algorithm always assures a minimum level of “front coverage”, regardless of the problem on hand. Such minimum level could be considered sufficient for real-life problem optimizations. Also The dimensionality of the design space affects in opposite directions the two algorithms: for ASEMOO the increase of dimensionality is detrimental to performance, while GeDEA-II experiences benefits due to total amount of direct evaluations. It seems that GeDEA-II has an optimal population size around 20, regardless the dimensionality of the problem at hand.
13
Turbojet Engine Performance Tuning with a New Map Adaptation Concept
G. A. Misté, E. Benini
Journal of Engineering for Gas Turbines and Power, July 2014, 136:071202. DOI: 10.1115/1.4026548
MORE INFO
136:071202 — DOI: 10.1115/1.4026548
Gas turbine off design performance prediction is strictly dependent on the accuracy of compressor and turbine map characteristics. Experimental data regarding component maps are very difficult to find in literature, since it is undisclosed proprietary information of the engine manufacturers. To overcome this limitation, gas turbine engineers use available generic component maps and modify them to reach the maximum adherence with the experimental measures. Different scaling and adaptation techniques have been employed to this aim; these methodologies are usually based upon analytic regression models which minimize the deviation from experimental data. However, since these models are built mainly for a specific compressor or turbine map, their generalization is quite difficult: in fact, regression is highly shape-dependent and, therefore, requires a different model for each different specific component. This paper proposes a solution to the problem stated above: a new method for map adaptation is investigated to improve steady-state off design prediction accuracy of a generic gas turbine component. The methodology does not employ analytical regression models; its main principle relies in performing map modifications in an appropriate neighborhood of the multiple experimental points used for the adaptation. When using gas turbine simulation codes, component maps are usually stored in a data matrix and are ordered in a format suitable for 2D interpolation. A perturbation of the values contained in the matrix results in component map morphing. An optimization algorithm varies the perturbation intensity vector in order to minimize the deviation between experimental and predicted points. The adaptation method is integrated inside TSHAFT, the gas turbine prediction code developed at the University of Padova. The assessment of this methodology will be exposed by illustrating a case study carried out upon a turbojet engine.
14
Helicopter Fuselage Data Fitting Using Smoothing Thin Plate Spline
G. Venturelli, R. Ponza, E. Benini
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering January 25, 2013
MORE INFO
Smoothing 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.
15
Performance of a Turboshaft Engine for Helicopter Applications Operating at Variable Shaft Speed
G. A. Misté, E. Benini
Proceedings of the ASME GTIndia Conference 2012, Mumbai, India, 1st December 2012
MORE INFO
1 December 2012 — DOI: 10.1115/GTINDIA2012-9505
An off-design steady state model of a generic turboshaft engine has been implemented to assess the influence of variable free power turbine (FPT) rotational speed on overall engine performance, with particular emphasis on helicopter applications. To this purpose, three off-design flight conditions were simulated and engine performance obtained with different FTP rotational speeds were compared. In this way, the impact on engine performance of a particular speed requested from the main helicopter rotor could be evaluated. Furthermore, an optimization routine was developed to find the optimal FPT speed which minimizes the engine specific fuel consumption (SFC) for each off-design steady state condition. The usual running line obtained with constant design FPT speed is compared with the optimized one. The results of the simulations are presented and discussed in detail. As a final simulation, the main rotor speed Omega required to minimize the engine fuel mass flow was estimated taking into account the different requirements of the main rotor and the turboshaft engine.
16
Assessment of the Engine Installation Performance of a Redesigned Tilt-rotor Intake
G. A. Misté, T. Nibale, A. Garavello, E. Benini
Proceedings of the 68th American Helicopter Society (AHS) Forum Fort Worth, Texas, USA, May 2012
MORE INFO
The always growing interest that rotorcraft manufacturers on reducing the environmental impact of their products pushes toward the development of specific methodologies devoted to propulsive efficiency optimization and evaluation of gas turbine engine performance. In particular, the determination of benefits that re-design and optimization of airframe engine installation components have on fuel consumption assume a relevant position in the design process. Optimized inlet and exhaust geometries can be obtained by coupling CFD codes with advanced optimization algorithms, automatically searching for optimal solutions among a prescribed search space. The consortium constituted by the University of Padova (UNIPD) and the spin-off company HIT09 successfully applied this automatic optimization approach to several components of the European tilt rotor ERICA, including engine installation. In this paper, the assessment of the engine performance gain given by such optimization is done using an engine off design performance prediction software, TSHAFT. First, a brief presentation of the code, developed at UNIPD, is given, along with validations carried out on a specific test case found in literature, for which experimental data are known. Subsequently, TSHAFT is employed in the ERICA case, taking into account inlet flow distortion effects. An exhaustive performance comparison between baseline and optimized engine installations is provided, highlighting the remarkable improvement in engine efficiency and compressor stability achieved by means of the optimization method implemented.
01
Small Wind Turbines: a New Methodology for Aerodynamic Performance Assessment Under Gust Conditions
L. Menegozzo, A. Dal Monte, E. Benini, A. Benato
Renewable Energy 121, 2018, p. 123-122
MORE INFO
In the present work, a numerical study aimed to analyse the effect of an extreme loading event on a Horizontal Axis Wind Turbine (HAWT) is performed. A 3D unsteady CFD model of the NREL Phase VI small-sized wind turbine is validated against experimental data, with the incompressible solver of ANSYS Fluent and an unstructured moving mesh strategy. Then the Extreme Operating Gust (EOG) model from IEC 61400-2 is considered as the inlet condition. The results of the aerodynamic response and of the structural ultimate check, based on the IEC guidelines, are presented for both the operating and the parked turbine, in order to underline the benefit of the safety position in terms of lower stress transferred to the critical root section.
02
A Kriging-assisted multiobjective evolutionary algorithm
G. Venturelli, E. Benini, L. Łaniewski-Wołłk
Applied Soft Computing, 2017
MORE INFO
A surrogate-assisted (SA) evolutionary algorithm for Multiobjective Optimization Problems (MOOPs) is presented as a contribution to Soft Computing (SC) in Artificial Intelligence (AI). Such algorithm is grounded on the cooperation between a “pure” evolutionary algorithm and a Kriging based algorithm featuring the Expected Hyper-Volume Improvement (EHVI) metric. Comparison with state-of-art pure and Kriging-assisted algorithms over two- and three-objective test functions have demonstrated that the proposed algorithm can achieve high performance in the approximation of the Pareto-optimal front mitigating the drawbacks of its parent algorithms.
03
Numerical study on internal flow field of a reversible turbine during continuous guide vane closing
X. Mao, A. Dal Monte, Y. Zheng, E. Benini
Energies, Volume 10, N. 7, Pages 988, 2017
MORE INFO
The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. In this way, the instability of the flow field is analyzed by continuously changing the guide vane openings from the best efficiency point (BEP). Unsteady flow characteristics are described by post-processing signals for several monitoring points including mass flow, torque, head and pressure in the frequency and time-frequency domains. The formation of vortices of different scales is observed from the origin to further enlargement and stabilization; the effect of the rotating structures on the flow passage is analyzed, and the influence of unsteady flow development on the performance of the turbine is investigated. Finally, the evolution during the period of load rejection is characterized in order to determine the hydrodynamic conditions causing the vibrations in the machine.
04
Development of an Open Source Environment for the Aero-Structural Optimization of Wind Turbines
A. Dal Monte
Ph.D. thesis, University of Padova, 2017
MORE INFO
An advanced open source optimization environment, for the design of Horizontal and Vertical Axis Wind Turbines, is hereby presented: several geometric parameters can be used as design variables while the proposed objective functions allow to run a multi-disciplinary study considering structural and aerodynamic analysis and the impact of the design on the total cost. In order to improve the performances of the considered wind turbine model, the airfoils can be parametrized in serveral ways and both in-house functions and open source tools are integrated in the optimization environment, based on DAKOTA. A BEM code evaluates the aerodynamic performances of the HAWT blades and it can be coupled with both FEM analysis and functions for the analysis of the cost of energy. The open source CFD code OpenFOAM has also been included, as a module, in the overall environment: a CFD analysis can be run in an completely automatic way, from the denition of the geometry, through the generation of the mesh and the solving phase to the post- processing analysis. The proposed optimization environment succeeded in improving the performances of both the considered Horizontal and Vertical Axis Wind Turbines in terms of structural, aerodynamic and cost objective functions.
05
Proposal for a Coupled Aerodynamic Structural Wind Turbine Blade Optimization
A. Dal Monte, S. De Betta, M. Raciti Castelli, E. Benini
Composite Structures, Volume 159, Pages 144–156, January 2017
MORE INFO
An advanced design algorithm for the AOC 15/50 wind turbine is hereby presented: both aerodynamic and structural parameters are considered as the design variables for a coupled BEM–FEM optimization.
In order to obtain an improvement in rotor blade design, a modified version of the S.O.C.R.A.TE. algorithm combines a BEM evaluation of its aerodynamic performance, a FEM structural analysis and a genetic algorithm. Both the aerodynamic power (resulting from the BEM analysis) and the tip displacement (produced by the aerodynamic forces and the inertial loads) are considered as the fitness functions for the optimization problem.
An improved distribution of both chord values and twist angles is determined, as well as an optimal layout of the blade composite skin. A slight increase in the aerodynamic power generation is obtained, as well as a marked improvement in overall blade deformation characteristics.
06
Validation of a numerical model of a Horizontal Axis Wind Turbine with experimental data using two CFD codes
A. Dal Monte, E. Benini
EWEA Analysis of Operating Wind Farms, Bilbao 14-15 April 2016
MORE INFO
Aim of the work is the assessment of the numerical model of the AOC15/50 Horizontal Axis Wind Turbine using the open source CFD code OpenFOAM. The obtained results are compared with both experimental and numerical data obtained from the fluid-dynamic analysis performed using the commercial CFD Package ANSYS Fluent.
The calculated power curve for the online rotational wind speed (65rpm) and the contribution of the blade sections to the total torque in spanwise direction are presented. Also, the comparison of the pressure distribution on the blade surface and the absolute velocity flow field are presented.
The analysis show a good accordance in the power prediction for low velocities, however stall phenomena compromise the evaluation of the power curve for high velocities.
07
Numerical Evaluation of Aerodynamic and Inertial Contributions to Darrieus Wind Turbine Blade Deformation
M. Raciti Castelli, A. Dal Monte, M. Quaresimin, E. Benini
Renewable Energy 51, 2016, p. 101-112
MORE INFO
This paper presents a model for the evaluation of aerodynamic and inertial contributions to a vertical-axis wind turbine (VAWT) blade deformation. Through the use of a specially designed coupling code, a solid modeling software, capable of generating the desired blade geometry depending on the design geometric parameters, is linked to a finite volume Computational Fluid Dynamic (CFD) code for the calculation of rotor performance and to a Finite Element Method (FEM) code for the structural design analysis of rotor blades. After describing the computational model and the relative validation procedure, a full RANS unsteady calculation is presented for a three-bladed rotor architecture, characterized by a NACA 0012 profile. Flow field characteristics are investigated for a constant unperturbed free-stream wind velocity of 9 m/s, determining the torque coefficient generated from the three blades as a function of rotor azimuthal coordinate. The emphasis is subsequently placed on obtaining an estimate for both pressure/tangential forces and centrifugal ones to blade structural loadings, thus assessing the influence of aerodynamic and inertial contributions to blade stresses and deformations.
08
Development of Numerical Procedures for Turbomachinery Optimization
G. Venturelli
Ph.D thesis, University of Padova, 2015
MORE INFO
This Doctoral Thesis deals with high speed turbomachinery optimization and all those tools employed in the optimization process, mainly the optimization algorithm, the parameterization framework and the automatic CFD-based optimization loop. Optimization itself is not just a mean to improve the performance of a generic system, but can be a powerful instigator that helps gaining insight on the physic phenomena behind the observed improvements. As for the optimization engine, a novel surrogate-assisted (SA) genetic algorithm for multi-objective optimization problems, namely GeDEA-II-K, was developed. GeDEA-II-K is grounded on the cooperation between a genetic algorithm, namely GeDEA-II, and the Kriging methodology, with the aim at speeding up the optimization process by taking advantage of the surrogate model. The comparison over two- and three-objective test functions revealed the effectiveness of GeDEA-II-K approach. In order to carry out high speed turbomachinery optimizations, an automatic CFD-based optimization loop built around GeDEA-II-K was constructed. The loop was realized for a UNIX/Linux cluster environment in order to exploit the computational resources of parallel computing. Among the tools, a dedicated parameterization framework for 2D airfoils and 3D blades has been designed based on the displacement filed approach. The effectiveness of both the CFD- based automatic loop and the parameterization was verified on two real-life multi-objective optimization problems: the 2D shape optimization of a supersonic compressor cascade and the 3D shape optimization of the NASA Rotor 67. To better understand the outcomes of the optimization process, a wide section has been dedicated to supersonic flows and their behavior when forced to work throughout compressor cascades. The results obtained surely have demonstrated the effectiveness of the optimization approach, and even more have given deep insight on the physic of supersonic flows in the high speed turbomachinery applications that were studied.
09
Multi-Objective Structural Optimization of a HAWT Composite Blade Composite Structures
A. Dal Monte, M. Raciti Castelli, E. Benini
Vol 106, 2013, p. 101-112
MORE INFO
The AOC 15/50 wind turbine blade has been considered as the baseline configuration for a structural optimization process based on a multi-objective genetic algorithm. Through the optimization of several combinations of both the type and the layup of the laminas, an improved rotor blade has been obtained without changing the composite materials adopted for the original architecture. The design variables of the optimization are both the choice of the employed materials and their placement in the layout of the blade skin. A marked reduction of the overall blade weight and a corresponding increment of its flapwise rigidity have been obtained. An unwanted small increase of the edgewise deformation has also been registered, requiring a further optimization process starting from the obtained optimal rotor blade configuration, in order to enhance also the edgewise rigidity of the blade.
10
Direct Measurements of Wind Data over 100 Meters above the Ground in the Site of Lendinara, Italy
A. Dal Monte, M. Raciti Castelli, G. Bellato, L. Stevanato, E. Benini
International Journal of Mathematical, Computational, Physical, Electrical and Computer Engineering Vol 6, No 9, 2012
MORE INFO
The wind resource in the Italian site of Lendinara (RO) is analyzed through a systematic anemometric campaign performed on the top of the bell tower, at an altitude of over 100 m above the ground. Both the average wind speed and the Weibull distribution are computed. The resulting average wind velocity is in accordance with the numerical predictions of the Italian Wind Atlas, confirming the accuracy of the extrapolation of wind data adopted for the evaluation of wind potential at higher altitudes with respect to the commonly placed measurement stations.
11
Evaluation of the wind potential in the province of Belluno (Italy)
A. Dal Monte, M. Raciti Castelli, E. Benini
Environmental, Energy, and Structural Monitoring Systems (EESMS, 2012)
MORE INFO
Anemometric data from a measurement campaign performed in the whole province of Belluno (Italy) have been analyzed in order to evaluate its wind potential. Data collected from 15 anemometric stations, placed at a height of 10 m over the ground, have been considered. The temporal evolution of the average wind velocity in each measurement site has been computed, as well as the Weibull distribution, allowing a comparison between measured data and the prediction of the Italian Wind Atlas.
01
PV-PCM Integrated Glazed Facades and Robustness of Optimization
A. Dal Monte, H. Elarga, F. Goia, E. Benini
Building Simulation Conference 2019, Rome, 2-4 September 2019
02
PV-PCM Integration in Glazed Building. Co-Simulation and Genetic Optimization Study
H. Elarga, A. Dal Monte, E. Benini
Building and Environment, Vol 126, p. 161-175
MORE INFO
The study describes a multi-objective optimization algorithm for an innovative integration of forced ventilated PV-PCM modules in glazed façade buildings: the aim is to identify and optimize the parameters that most affect thermal and energy performances. 1-D model, finite difference method FDM, thermal resistances technique and enthalpy method were applied to describe different façade solutions and transient thermal performance of PCM. The coupling between the PV-PCM façade code implemented in MATLAB and the TRNSYS software was developed to estimate the dynamic thermal energy profiles. An exploratory step has also been considered prior to the optimization algorithm: it evaluates the energy profiles before and after the application of PCM to PV module integrated in glazed building. The optimization analysis investigate parameters such as ventilation flow rates and time schedule to obtain the best combination suiting the PCM performance and external-internal loads. A group of solution were identified on the Pareto front. Savings in thermal loads for the best individual reached 26.4% while the best in temperature increment in operating temperatures was recorded as 6.8% comparing to the design set temperature.
03
Thermal and electrical performance of an integrated PV-PCM system in double skin façades: A numerical study
H. Elarga, F. Goia, A. Zarrella, A. Dal Monte, E. Benini
Solar Energy 136(C):112-124, October 2016
MORE INFO
In this article the performance of a system that integrates a photovoltaic (PV) layer and a phase change material (PCM) layer in a double skin façade (DSF) is investigated. A physical–mathematical model is developed to simulate the dynamic thermal behaviour of the system, and numerical simulations are carried out for different climates (Venice, Helsinki and Abu Dhabi) in order to evaluate the performance of the proposed solution. The numerical model combines different validated codes for the simulation of optical, thermal, and electrical behaviour of PCM, PV and DSF. The model is then coupled with the indoor air heat balance equation to evaluate the impact of the proposed façade system on the heating and cooling energy demand.
The adoption of a PCM layer in the DSF cavity, in combination with a semi-transparent PV layer, leads to a reduction in the monthly cooling energy demand in the 20–30% range. This result is particularly relevant for hot climates – where cooling loads are seen throughout the year. The improvement in terms of heating load in more cold- dominated locations is limited. The smoothing of the PV module temperature leads to an increase in the electrical energy converted by the PV, with peak values of improvement in the range of 5–8% when the DSF is equipped with the PCM–PV configuration. Ventilation strategies of the façade cavity, coupled with the correct selection of PCM (and of its transition-phase temperature range), are the key aspects to ensure effective management of the proposed technology.
01
High Performance Waterjets: Study of an Innovative Scoop Inlet and Development of a Novel Method to Design Ducted Propellers
D. Papale
Ph.D. thesis, University of Padova, 2015
MORE INFO
In the last decades the diffusion of waterjet systems for commercial applications in the high speed field is on the increase. These marine propulsors show remarkable qualities in terms of fuel consumption, noise, vibrations and manoeuvrability but they have some disadvantages which make their use optimal only for a limited speed range and which limit the overall propulsive efficiency. In the present document is described a way to modify a conventional waterjet with the aim of reducing these problems, increasing the overall efficiency. Many problems are dealt with. In chapter 3 it is shown how the substitution of a conventional flush inlet with a new scoop inlet could be an efficient way to minimise the total pressure losses and the non- uniformity velocity distribution upstream the pump, limiting in this way the influence of the boundary layer ingestion on the machine performance. In chapter 4 a novel method to study and design axial pumps is developed and explained. In chapter 5 a rim driven propeller is designed and tested numerically and experimentally demonstrating the good prediction capabilities of the method.
02
Design and Computational Fluid Dynamics Testing of a Ducted Propeller for a Hovercraft Vehicle Propulsion System
D. Papale
M.Sc. thesis, University of Padova, 2011
MORE INFO
In the following work we will show how to carry out a preliminary design of a propulsion system for a hovercraft vehicle. The study was divided into three parts: analysis of the lift sub-system, analysis of the thrust sub-system and the analysis of the blade diffuser for turning axially the air flow exiting from the propeller of the thrust sub-system.
The analysis was carried out by using a program written in Matlab, and subsequently using a CFD analysis to evaluate and confirm the choices made during development of the project.
The work has been completed with good results: for all the three aspects we found a way that enabled us to achieve the desired results with a high degree of reliability. After this analysis, it will be possible to proceed with experimental tests and therefore with the industrial production of the hovercraft propulsion system