Innovative Solutions For The Thermal Control Of Aeronautic Vehicles

The ECS and the anti-ice systems are two of the energy consumers for an aircraft; they absorb together two times the sum of the power of all the other systems (electrical, mechanical and hydraulic). More efficient ECSs and a more efficient anti-ice sub-systems would reduce the aircraft fuel consumption increasing the operative radius of the vehicle and also increasing the maximum useful load.&#13;\n&#13;\nThe anti-ice sub-system is not only a key energy consumer but it is also a system critical for the flight safety: a failure of this system means a mission abort and the landing on the nearest airport.&#13;\n&#13;\nThis thesis presents the results of several mathematical models which have been developed to study the performance of the aforementioned systems and the strategies to reduce their impacts on the aircraft fuel consumption. The models have been developed using AMEsim and Simulink.&#13;\n&#13;\nIn particular a mathematical model, which describes the behavior of the inline pneumatic valves, have been created. The model uses the fundamental thermodynamic and mechanical differential equations to simulate the dynamic behavior of the valves. The mathematical model reproduces the results of the experimental tests within their uncertainty. The validated model has been used to explore the behavior of the valve and its own subcomponents proposing two possible solutions to increase the operative range of the valves and to decrease the influence of the pressure and temperature on the regulated pressure.&#13;\n&#13;\nThe second detailed mathematical model created calculates the performance of the plate and wavy fins compact heat exchangers. The model, based on the work of Kays &amp; London, includes some improvements related to the description heat exchanger geometry and related to the empirical correlations used to calculate the number of Stanton. The tests performed on three different heat exchangers have been used to validated the developed model; the mathematical model is able to predict the performance of the performance of the HXs with an accuracy compatible with most the industrial applications.&#13;\n&#13;\nThe developed detailed models have been used to simulate the behavior of the system where they are installed.&#13;\n&#13;\nThe behavior of an anti-ice system at extreme high bleed air temperature has been analyzed. An innovative architecture for anti-ice system is studied and the benefits on aircraft fuel consumption for a standard day mission are shown.&#13;\n&#13;\n The performance of an reverse Brayton-Joule cycle has been analyzed and a new possible control strategy based on a line installed in series to the air cycle machine is proposed. The limits of the proposed architecture are exposed studying the case of a system used to cool some electronic equipment. The benefits of the use of a reverse Brayton-Joule system which does not use the air bled from the engine (bleedless approach) are detailed with particular attention to the gain in terms of fuel penalty.&#13;\n&#13;\nThe thesis ends with the results of the VCS simulations. Some technical solutions to fit a fixed displacement compressor architecture into an aircraft are explained; the solutions are oriented to increase the reliability of the compressor avoiding a continuous switch on and off even with low heat loads. A variable displacement compressor improves the overall efficiency of the system on a full mission profile (high COP in the cruise phase). Two strategies, one for passenger compartments and one for electronic cooling, which are able to expand the working envelope (in terms of minimum heat load) of the variable displacement compressor architecture are proposed.

Topic: Heat Transfer and Optimization
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences