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.

View Video Presentation: https://doi.org/10.2514/6.2022-3400.vid The paper describes the numerical campaign carried out at CIRA for the $1^{st}$ AIAA Ice Prediction Workshop (IPW). Some benchmarks have been selected with the aim of assessing the in-house numerical capabilities for different aspects of the ice-accretion chain. The computed cases range from water droplet impingement to complete ice-accretions both in two- and three-dimensions. The basic idea is coupling different methodologies to exploit their respective benefits towards the prediction of an in-flight ice-accretion. The common recognized approach is decoupling the air and water phases thus making use of well-assessed codes originally developed for each specific area. In particular, four different low- and high-fidelity methods are used to compute the aerodynamic field: a panel method and three finite-volume solvers. Different tools are used to compute the droplets' impingement on two and three-dimensional configurations and three different approaches are applied for ice-accretion. This allows for a certain flexibility in treating different levels of complexity for both the geometry and flow conditions. The main results achieved are discussed in the paper highlighting the issues to be addressed. Remedies to improve the accuracy of the numerical solutions are discussed.

An unsteady numerical investigation on mixed convection in a two dimensional open ended cavity with different aspect ratios is carried out. In this investigation, uniform temperature is set to the left and the right sides of the cavity while the other surfaces are adiabatic. The simulation is performed for a wide range of Reynolds numbers (Re = 100–1000) and Richardson numbers (Ri = 0.132–6.5 × 10²), and various cavity aspect ratios (L/D = 0.5–4.0) and H/D = 0.1. Governing equations are solved using a cell centered finite volume code, a SIMPLE numerical projection scheme and a 2nd order accuracy. Results are presented in the form of streamlines, isothermal lines, and velocity profiles in the channel. The conclusion is that the enhancement of heat transfer rate is generated principally by the increasing Re and the assisting configuration is thermally more efficient when compared to the opposing one.

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.

Purpose: The purpose of this paper is to focus on a morphing architecture, conceived to produce droop nose effect, thus preserving high lift performance and laminar flow.Design/methodology/approach: A numerical approach was adopted. On the base of preliminary aerodynamic requirements, the main aspects of the actuation architecture were defined and then assessed through a genetic approach.Findings: Two different working modalities of mentioned architecture were identified: the former implying the use of an actuator, the latter taking advantage of a tailored elastic element, able to actuate morphing under the action of aerodynamic loads, without the aid of actuators.Research limitations/implications: The research presented in this work refers to an optimisation process currently tailored on preliminary aerodynamic requirements (leading edge vertical displacement maximisation, leading edge radius increase).Originality/value: The research shows the possibility of producing morphing on the leading edge zone, actuating droop nose effect on metallic (constant and pice wise thickness) and composite skins.