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Passive Ice Protection System

Periodic Reporting for period 3 - PIPS (Passive Ice Protection System)

Okres sprawozdawczy: 2019-07-01 do 2020-12-31

In the domain of aeronautical security, one of the main energy contributors is the anti-icing system. Several zones must be protected against icing and one of these is the engine air intake. Two technologies are used nowadays for this function: the first one uses directly hot air coming from the engine to be brought on the back of the surface to be protected and the second one uses electric heaters on the same surface. Both are costly in terms of fuel consumption. PIPS project proposes a new technology in this domain. We propose to transport energy, which is currently not used, from hot air in the engine zone to the protected surface by the means of a two-phase system. This passive but highly efficient heat exchanger, utilizes the phase-changes of a thermal fluid and a capillary pump to bring the heat from one zone to another in a closed metallic loop.
The PIPS project addresses the specific aeronautical challenge relative to the improvement and optimization of nacelle/engine integration to save weight and fuel consumption thanks to high technology devices leading to significant CO2 savings.
The ultimate goal of this project is to replace the today ice protection systems mounted on the surfaces of engine intakes by a two-phase passive thermal system with the following main benefits:
• Reduction of fuel consumption and raise of the engine effectiveness using a highly efficient thermal system for the extraction of heat from the engine to the protected surface (high heat transfer capacity compared to the two-phase system mass);
• Decrease of mass and ease of thermal icing protection integration by removing the today electro-thermal and pneumatic usual device used to collect power from the engine;
• Increase of reliability of a critical function such as anti-icing by reducing active control and operations;
• Lower impact on environment and operating cost reduction by using a passive thermal system which is maintenance free.
At two-phase system level, the main innovation was the development of a novel system, derived from a space technology, to the specific aeronautical requirements. Materials, architecture and functioning are novel and are under patent application.
TRL6 was reached for the two-phase product to enable the European aeronautical communities to propose more efficient aircrafts with less environmental impacts.
Icing wind tunnel tests has proved the concept and the efficiency of the technology under relevant condition at full scale (icing and low temperature high speed wind) on most parts of the zone to be protected. Nevertheless, some parts were not properly de-iced due to bad distribution of heat on the zones to protect. Slight design modifications of the condenser are proposed to eventually achieve higher TRL levels.
The most relevant characteristics assessed and managed through this project were:
• The severe and highly variable thermal and mechanical environment around the engine and its nacelle and
• The specific geometry of the protected surface.
This project will so contribute to the strengthening of the competitiveness of the European industry by introducing two-phase heat management systems contributing to the reduction of CO2 emissions and airplane noise, toward an eco-conception and an eco-utilization point of view.
During the first period of the project, the concept has been specified. A trade-off has shown that for the given requirements and constraints in terms of environment and thermal performances, only a system consisting in several capillary pumped loops (CPL) could transport enough heat, completely passively, from the given hot source to the condenser. provided a new evaporator design. The resulting breadboarding activities have secured two important points:
- The manufacturing of the new evaporator;
- The concept of heat transfer from blown hot air to the inside of a two-phase system by means of heat sink fixed on the flat surfaces of the evaporator of the CPL.
A specific trade-off has been performed for the condenser which has shown that a design with an ALM part with tubing, inside the air intake skin, must cover the entirety of the air intake surface. Preliminary prediction and the PDR (Preliminary Design Review) have concluded that two system designs are possible:
- A three CPL completely passive system;
- A one CPL actively controlled system with a small amount of power need.
The first solution is 3 time heavier while the second is requiring spending some power to maintain the reservoir of the CPL at a given optimized temperature. The EM (Engineering Model) considered the second solution and was built at 1:1 scale. It enabled to prove the concept, validate the prediction and to establish the amount of power necessary to stabilize the saturation temperature of the fluid (<1.8% of the transported power).
The last part of the project dealt with the design and modelling of the system that has been tested in Icing Wind Tunnel (IWT). Prediction on the quantity of heat transported, the thermal resistance of each part has been successfully performed on the EM model and transposed to the IWT prototype. The analysis of the IWT tests and comparison with the model has been performed and showed that most quantities are well modelled and predicted but that a supplementary model is needed to predict in a satisfactory way the icing surface temperature in every point of the surface area.
The innovation realized in the two first periods of the project is the development of a new CPL with a new architecture (patent application). The evaporator in terms of material (full stainless steel), size (100 x 200), porous wick and design (double sided). The concept of capturing the heat by means of heat sinks from both side of the evaporator is also new and has been validated. Final tests have demonstrated in harsh conditions (high speed icing environment at low temperatures) that this new technology was efficient. The development of a new condenser inside the skin of the EAI with different heat flux densities on different position of the condenser is also new. The new condenser design mixes parallel and a series design distribution of heat on curved and complex surfaces. The actual design concept allows possible upgrading for other sizes of air intake or for other design cases by changing the size of the evaporator. The success of the project will enable to bring the heat which is actually unused, from hot air to de-ice the EAI and thus mainly reduce fuel consumption and CO2 emission.