CROP Project Newsletter Q1/2014
The Project
The CROP project (Cycloidal Rotor Optimized for Propulsion) introduces an innovative propulsion system for aircraft based on the cycloidal rotor concept, using an integrated approach that includes the electric drive train, airframe integration and an environmentally friendly energy source.
Cycloidal Rotor Optimized for Propulsion
The CROP system is supported on a multi-physics approach:
1. The high thrust is obtained by unsteady-based cycloidal rotor operation;
2. The development of low-weight electric power drives for the system;
3. Airframe re-design to accomplish optimum integration of the cycloidal propulsor;
The strengths of the CROP concept are:
- High thrust levels by using unsteady airflows
- Low weight by using an integrated design approach between airframe and cycloidal propulsor
The revolutionary CROP propulsion concept will introduce new air-vehicle concepts, overcoming traditional limitation on short take-off and landing, including hovering capability.
For further information, please visit www.crop-project.eu
Project Interim Report 2013
Meetings: KOM – January 2013, Covilhã/Portugal
The CROP Kick-off Meeting (KoM) took place at the University of Beira Interior (UBI) at Covilhã (Portugal) on January 21st – 22nd 2013. The scientific organisation was entrusted to Prof. José Pascoa (UBI) and an organising committee was set up in the earliest phase of the process to take care of the organisation.
The KoM featured talks covered topics related to experimental planning, preliminary concept design of the system, CFD analysis, technology evaluation, testing and targeted configurations.
CROP Consortium
Official Video of the CROP Project Kick off Meeting
Intermediate Research Results
System modelling started in June under Work Package 2.4.3 and this led to an analysis of possible cyclogyro rotor configurations in September (Work Package 2.6). In June IAT21 started to validate the evaluations derived from this modelling. To do this IAT21 had to design and develop a cyclogyro rotor assembly that could be used at the heart of a future electrically powered aircraft.
A wide variety of different designs, structures and materials were tested in order to achieve consistency in weight and strength. After many weeks of exhaustive tests a major breakthrough was achieved in October when the rotor assembly components met the design expectations and passed high load stress tests in the CROP test rig in IAT21's laboratory in Traun/Austria.
D-Dalus L1 Electric Lab Model
IAT21 then constructed a small lab model with 4 rotor assemblies to assess whether the anticipated thrust would be sufficient to launch a small electrically powered cyclogyro aircraft. The experimentation work now moved from the domain of mechanical and materials engineering to software systems engineering as the team sought to design the complex control systems that would control motor speed, vary the pitch of the blades on each rotor and stabilize the aircraft in flight. Each of the experimentation threads came together in October when, in the cold test labs in Traun, IAT21 successfully launched a 20 kg electrically powered laboratory model of a cyclogyro craft.
For further information to the CROP features, please visit: www.d-dalus.com
The main concern of the scientists of University of Modena and Reggio Emilia is the blades' pitching mechanism. The present and actually simpler model to realize is a four bars linkage mechanism. It guarantees almost sinusoidal pitching schedule, with the possibility of varying the maximum angle of attack – i.e. the intensity of thrust – and the thrust direction.
Nevertheless given the wide variability on the possible flight conditions, and on the contrary the limited set of pitching schedules a four bar linkage mechanism offers, it is questionable if this configuration always represents an optimal solution in terms of stability and energy consumption for the system.
A comparison with other blades' pitching mechanisms, which can set different pitching schedules, is required. About possible alternative configuration for a comparison there is the cam-based passive blade pitching mechanism developed by Chopra et al., which can reproduce the zero angle of attack pitching schedule (ZAOA) for different advance ratios Formel, where:
V: Flux velocity at infinity,
Omega: Angular velocity of the rotor,
Radius: Radius of the rotor.
An almost sinusoidal pitching schedule can then be added to the ZAOA schedule in order to produce thrust.
Another interesting configuration is given by cycloidal rotors with individual actuation of rotor blades. Contrary to the previous cases, no predetermined pitching profiles are now given, but actually all the possible blades' pitching schedules can be theoretically achieved. So before operating a comparison the optimal pitching profiles are to be determined for given fly conditions.
In order to achieve this, some aerodynamic models are to be developed and/or tested and some optimization techniques are to be applied. For the first ones, together with some basilar models, adaptations from the much more sophisticated UBI models, which work with good agreement with experimental results in hover condition, will be considered. For the second ones, different minimization techniques like Lagrange multipliers and least square methods for truncated Fourier series' coefficients will be used.
Once achieved optimal pitching schedules, comparisons among the pitching mechanisms so far described will be performed. They will be based on CFD analysis, on the responses of the aerodynamic models previously described and if possible on experimental results. Fly conditions considered will be uniform forward flight at different velocities and advanced ratios, together with hover flight at different angular velocity. If performances registered by the four bar linkage mechanism will not disclose too much from the other ones, this set up will be recommended; otherwise the implementation of other configurations will be strongly suggested.
UBI is working on the implementation of PECyT (Plasma Enhanced Cycloidal Thruster) technology on CROP. PECyT uses DBD (Dielectric Barrier Discharge) plasma actuators for active flow control at reduced cost and weight. Plasma-based devices exploit the momentum coupling between the surrounding gas and plasma to manipulate the flow. This technology could be used to delay the stall onset on the blades, thus increasing the amount of lift that can be produced by each blade (Ref. [1]).
In this task we want to assess the cost/benefit of PECyT system in the performance improvement of classical CRs. We will show that the combined effects of the leading edge vortex with the PECyT system could delay flow separation at high angles of attack. The analysis of this kind of complex flows can be performed using numerical gas dynamic codes with suitable multiphysic CFD models (Ref. [2]).
Multi-DBD
When compared with other flow control techniques, these devices require low power consumption and do not require any moving mechanical parts. They also have a very fast frequency response that allows a real-time control of the fluid flow. A multi DBD (Figure 1a) consists in several pairs of electrodes separated by a dielectric barrier which is usually glass, Kapton or Teflon. One electrode is exposed to the air and the other is fully covered by a dielectric material.
The exposed electrode is assumed to be loaded by a high voltage, whereas the covered electrode is supposed to be grounded. Afterwards a high AC voltage signal, of sufficient amplitude (5-40kV) and frequency (1-20 kHz), is applied between the electrodes. The intense electric field partially ionizes the surrounding gas producing non-thermal plasma on the dielectric surface.
The ionized air (plasma) in presence of the electric field produces an attraction/repulsion on the surrounding air. Ionized particles are accelerated and transmit their momentum, through collisions, to the neutral air particles in the plasma region over the covered electrode. The result is an acceleration of the air in the proximity of the surface of the dielectric (ionic wind).
Experimental Activities
Ref. [1] - M. Abdollahzadeh, J.C. Páscoa, P.J. Oliveira (2013), "Two dimensional numerical modelling of nanosecond plasma Actuators, a preliminary study of application in propulsion systems", in Proc. EUCASS 2013 5th European Conference for Aeronautics and Space Sciences Munich, Germany, 1 - 5 July 2013.
Ref. [2] - M. Abdollahzadeh, J.C. Páscoa, P.J. Oliveira (2013), "Two-dimensional numerical modelling of interaction of micro-shock wave generated by nanosecond plasma actuators and transonic flow", Journal of Computational and Applied Mathematics, in press, www.sciencedirect.com.
Dissemination
CROP at AERO Friedrichshafen, April 2013
During 24th – 27th of April 2013, the CROP project was represented in Hall B3 besides other EU funded projects at the AERO Expo at Friedrichshafen / Germany, Europe's largest trade fair for general aviation.
CROP at AERO Friedrichshafen
CROP at Paris Air Show, June 2013
IAT21 has represented the CROP Project the Paris Air Show in June 2013.
CROP at Paris Air Show
Publications
During 2013 there were several publications made within the CROP project, its technology and its research results.
University of Beira Interior
Participation in SAE conference with one publication:
Monteiro J. A., Páscoa J. C., Xisto C.M., (2013), "Analytical Modelling of a Cyclorotor in Forward Flight", in Proc. SAE Aerotech 2013, Montreal, Quebec, Canada Nº 2013-01-2271 doi:10.4271/2013-01-2271.
Participation in ASME International Mechanical Engineering Congress & Exposition (San Diego, USA): 
Leger A. J., Páscoa J. C., Xisto C. M., (2013) "Parametric design of cycloidal rotor thrusters", Proceedings of ASME 2013 International Mechanical Engineering Congress & Exposition, IMECE2013, November 15-21, San Diego, California USA.
Organization of two sessions on topic 1-3 "Advances in Propulsion System" (José Páscoa, Michele Trancossi).
Participation in ICEUBI2013 conference with one publication:
Leger A. J., Páscoa J. C., Xisto C. M., (2013) "Kinematic and Dynamic Parametric Analysis of Cycloidal Rotor Thrusters", Proceedings of ICEUBI 2013 - International Conference on Engineering, November 27-29, UBI, Covilhã, Portugal.
José Páscoa participated in the Workshop Organized by ITS Portugal
www.its-portugal.eu
, at July 13, presenting MAAT, ACHEON and CROP projects.
Politecnico di Milano
L. Gagnon, M. Morandini, G. Quaranta, P. Masarati, "Cyclogyro Thrust Vectoring for Anti-Torque and Control of Helicopters", American Helicopter Society annual forum, May 2014, Montreal, Canada.
L. Gagnon, G. Quaranta, M. Morandini, P. Masarati, C. M. Xisto, J. C. Páscoa, "Fluid-Structure Interaction Analysis of a Cycloidal Rotor", AIAA conference, June 2014, Atlanta, USA.
Project Consortium
Universidade da Beira Interior   Universidade da Beira Interior, Portugal
Università di Modena e Reggio Emilia   Università degli Studi di Modena e Reggio Emilia, Italy
IAT21 - Innovative Aeronautics Technologies GmbH   IAT21 - Innovative Aeronautics
Technologies GmbH, Austria
The University of Sheffield   The University of Sheffield, United Kingdom
Grob Aircraft AG   Grob Aircraft AG, Germany
Politecnico di Milano   Politecnico di Milano, Italy
Disclaimer
Coordinator:
Universidade da Beira Interior, Portugal
Contact:
Prof. Dr. José Carlos Páscoa Marques
Convento de Santo Antonio
Covilha, Portugal
Email: pascoa@ubi.pt
www.ubi.pt
For more information about the CROP project, please visit: www.crop-project.eu.
The research leading to these results has received funding from the European Union Seventh Framework Programme [FP7/2007-2013] under grant agreement no. [323047]
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