Electrification of aircraft is a very challenging task as the demand for energy and power is high. While the storage and generation of electrical energy are widely studied due to the limited specific energy and specific power of batteries and fuel cells, electric machines (power electronics and motors) which have years of experience in many industrial fields must be improved when applied to aviation: they generally have a high efficiency but the increase in power levels determines significant thermal loads which, unlike internal combustion engines (ICE), cannot be rejected with the exhaust. There is therefore a need for thermal management systems (TMSs) with the main objective of maintaining operating temperatures below the maximum level required by electric machines. Turboprop aircraft, such as the ATR 72 or the Dash 8-Q400, are commonly used for regional transport and are equipped with two gas turbine engines whose combined power is in the order of 4 MW. Electric and hybrid propulsion systems for these aircraft are being studied by several leading commercial aviation industries and start-ups, and the 1MW motor size seems to be the main option as it could be used in different aircraft configurations, particularly those that exploit distributed electric propulsion. With reference to the topics mentioned above, the present work presents the design of a TMS for a high-power motor/generator whose electrical architecture is known. Once integrated with the electrical part, the TMS must allow a weight/power ratio of 14 kW/kg (or 20 kW/kg at peak power) while maintaining the temperature below the limit temperature with reasonable safety margins. Submerged jet oil is the cooling technique here applied with a focus on diathermic oil. Parameters affecting cooling, like rotor speed and filling factor, are analysed with advanced CFD.

Electrification has become increasingly common in aerospace due to climate change concerns. After successful applications in general aviation aircraft, electrification is now addressing subregional (up to 19 passengers) and regional aircraft (around 80 passengers). Megawatt-class electric motors are needed both to drive propellers and to act as high-power generators in hybrid–electric propulsion systems. Power levels for this class of aircraft require a proper design of heat management systems capable of dissipating a much higher quantity of heat than that dissipated by traditional cooling systems. The technical solution here explored is based on the addition into a diathermic base liquid of nanoparticles, which can increase (by up to 30%) the thermal conductivity of the refrigerant, also providing large surface area enhancing the heat transfer capacity of base liquids. The Italian Aerospace Research Centre (CIRA), as part of the European research initiative Optimised Electric Network Architectures and Systems for More-Electric Aircraft (ORCHESTRA), developed a thermal management system (TMS) based on impinging jets technology for a 1 MW electric motor. In this work, a numerical verification of the possibility for nanofluids to improve the heat exchange efficiency of a submerged oil impinging jets TMS designed to directly cool the inner components of a 1 MW motor is conducted. Investigations aimed to analyse two nanoparticle types (alumina and graphite) added to diathermic oil with concentrations between 1% and 5% by volume. The application of nanofluids significantly increases final thermal conductivity with respect to conventional coolants, a 60% improvement in heat transfer at a fixed mass flow rate is achieved. Electric motor maximum temperatures are approximately 10% lower than those achieved with solely diathermic oil. This result is significant as a safety margin is needed in all cases where a sudden increase in power occurs.

One of the tasks of the FutureWings project, funded by the European Commission within the 7th framework, was to numerically validate the mechanical behavior of a wing whose deflections had to be controlled via a suitable distribution of piezoelectric patches. Starting from a reference geometry (a NACA 0012 airfoil), wing profiles were implemented and analyzed using the fluid–structure interaction analysis technique. The wing section was designed with a morphing profile in which both the front and rear parts self-deform via piezoelectric patches that serve actuators glued to the skin of the profile. A Macro Fiber Composite (MFC) was used as the piezoelectric actuator. Aeroelastic analyses were performed at low Mach numbers under the sea-level flight condition. Analysis of the technical solution was based on an examination of the aerodynamic coefficients and polar curves of the profile, as the control voltage of the patches can vary. The results were compared with those available in the literature. As a preliminary step, this work contributes to examining the current technical possibilities of this technology relating to the application of piezoelectric patches as actuators in the field of aerostructures.

One of the challenges of our age is climate change and the ways in which it affects the Earth’s global ecosystem. To face the problems linked to such an issue, the international community has defined actions aimed at the reduction in greenhouse gas emissions in several sectors, including the aviation industry, which has been requested to mitigate its environmental impact. Conventional aircraft propulsion systems depend on fossil fuels, significantly contributing to global carbon emissions. For this reason, innovative propulsion technologies are needed to reduce aviation’s impact on the environment. Electric propulsion has emerged as a promising solution among the several innovative technologies introduced to face climate change challenges. It offers, in fact, a pathway to more sustainable air travel by eliminating direct greenhouse gas emissions, enhancing energy efficiency. Unfortunately, integrating electric motors into aircraft is currently a big challenge, primarily due to thermal management-related issues. Efficient heat dissipation is crucial to maintain optimal performance, reliability, and safety of the electric motor, but aeronautic applications are highly demanding in terms of power, so ad hoc Thermal Management Systems (TMSs) must be developed. The present paper explores the design and optimization of a TMS tailored for a megawatt electric motor in aviation, suitable for regional aircraft (~80 pax). The proposed system relies on coolant oil injected through a hollow shaft and radial tubes to directly reach hot spots and ensure effective heat distribution inside the permanent magnet cavity. The goal of this paper is to demonstrate how advanced TMS strategies can enhance operational efficiency and extend the lifespan of electric motors for aeronautic applications. The effectiveness of the radial tube configuration is assessed by means of advanced Computational Fluid Dynamics (CFD) analysis with the aim of verifying that the proposed design is able to maintain system thermal stability and prevent its overheating.

Electrification has become increasingly common in aerospace due to climate change concerns. After successful applications in general aviation aircraft, electrification is now addressing subregional (<= 19 pax) and regional aircraft (~ 80 pax). Megawatt-class electric motors are needed both to drive propellers and to act as high-power generators in hybrid-electric propulsion systems. Although the efficiency of these electric machines is very high, the power levels require the design of heat management systems capable of dissipating a much higher quantity of heat than that dissipated by traditional cooling systems. Coolants also deserve renewed attention as their associated physical properties need to be improved to ensure greater heat removal than conventional coolants. The technical solution here explored is the addition of nanoparticles into a base liquid. Nanoparticles, in fact, have unique properties such as high thermal conductivity and large surface area that enhance the heat transfer capacity of base liquids. However, the addition of nanoparticles into a base liquid induces new challenges to be faced, such as stability, thermal and electrical conductivity properties of nanofluids, cleaning and erosion of equipment. The Italian Aerospace Research Centre (CIRA) has developed, as part of the European research initiative ORCHESTRA, a thermal management system (TMS) based on impinging jets technology for a 1 MW electric motor. This work presents the subsequent activities that CIRA has carried out to demonstrate the enhancements achievable from nanofluids. In particular, two different nanoparticles were added to the base liquid of the cooling system of the aforementioned 1 MW electric motor: alumina and graphite in two distinct molecular structure configurations, each with different concentrations between 1% and 10% (volume fraction of diathermic oil). The application of nanofluids to the reference TMS is shown to increase heat transfer at a fixed mass flow rate.

The growing need to reduce aviation’s carbon footprint and reliance on fossil fuels has prompted the exploration of alternative propulsion technologies. Fuel cell (FC) systems offer a sustainable solution, generating only water vapor as a by-product. This paper presents a conceptual study, focusing on subsystem integration and safety aspects, for an 80-passenger, hydrogen-powered aircraft developed within the European Union (EU) co-funded NEWBORN (NExt generation high poWer fuel cells for airBORNe applications) Project. The designed configuration incorporates wing-mounted pods housing fuel cells, an electric motor, an inverter, a Thermal Management System (TMS), and Balance of Performance (BoP). This configuration is an effort towards environmentally friendly solutions, addressing climate change and paving the way towards greener aviation.