The counter-rotating open rotor (CROR) engine concept, also called a propfan, has two propellers that rotate in opposite directions around the same axis. The upstream one imparts energy to the air flow that is recovered by the downstream one, increasing efficiency. Given the close proximity of the two rotors and the high dynamic loads, unsteady aerodynamics and fatigue are technical challenges that must be addressed. Funded by the EU, the project LIGHT-COWLS is developing methods to produce rotating engine nacelle components (cowls) out of lightweight composites targeted at the CROR. They will be used to produce conical cylindrical components approximately 1.5 m in diameter. For use in the EU’s Sustainable and Green Engine 2 (SAGE2) demonstrator, scientists focused on meeting the necessary weight and strength specifications, while solving the issue of high-temperature operation. The focus was on resins with high glass transition temperatures (Tg) and reinforcing fibres. Tg is a critical aspect for any polymeric system. Below the Tg, a polymeric compound has much higher strength and stiffness along with greater electrical insulation, dimensional stability and chemical resistance. For practical purposes, the Tg is often considered as the limit in operating temperature. Within the first project period, scientists selected and tested composite materials and developed a preliminary design. Based on this, partners carried out manufacturing risk mitigation trials to assess possible manufacturing challenges and take steps to reduce the probability of failure. The project then progressed to the critical design phase. All manufactured cowl parts were delivered to the SAGE 2 Open Rotor demonstration engine. LIGHT-COWLS researchers delivered aircraft-quality rotating cowls made from lightweight high-Tg composites to be used in the SAGE2 demonstrator for the CROR engine. Successful commercialisation will have major effects on fuel consumption and emissions with global impact on climate change and the costs of air travel.
Composites, counter-rotating open rotor, cowls, SAGE2, glass transition temperatures