Patrick Noble, propulsion staff engineer at Zunum Aero, explains how deploying engineering simulation is helping to achieve performance goals and reduce the time and costs of testing.
The aerospace industry is increasingly focusing on the development of hybrid-electric systems, especially for short-distance travel, to reduce emissions and operating costs. However, there are huge challenges. With 13,500 airports in the US, short-haul, regional air travel should be easy — a quick drive to a convenient airfield and you are ready for take-off.
There is, however, a vast regional transport gap. Not just in the US, but in Europe too. To close that gap, and help meet growing demand for lower energy usage and emissions, the industry must explore an alternative to today’s jet-driven hub-and-spoke model of flying. One option is for a door-to-door air system, using scale-independent hybrid-electric aircraft that reduce emissions and noise. For this alternative system to be successful, technology will be at the heart of all research, design and manufacturing activities.
Optimising a quiet, lightweight hybrid-electric propulsion system with efficient aerodynamic design is paramount to achieving the aircraft’s performance objectives. Traditionally, the process of component optimisation would be shared between design engineers and manufacturing engineers; the former would design a part, before handing over to the manufacturing team to trial and error a final component. The process is time intensive, costly and rarely produced a truly optimised part.
Engineering simulation, whereby components are digitally modelled, has revolutionised the development of parts over the last decade. Zenum, for example, employs it to deliver a propulsor (a ducted fan prototype) for ground-based testing using software obtained through the ANSYS Startup Programme. By accurately capturing the structural, aerodynamic and thermal loading behaviour of each component, the engineers make informed decisions about everything from large architectural issues — propulsor size, for example — to detailed system interfaces and joint behaviour. Simulation provides a reliable way to prove concept feasibility, improve efficiency and optimise design before the hardware and test phases of product development.
The Zunum Aero Quiet Electric Propulsor combines low-pressure fans with integrated fault-tolerant electric motors and controllers. In the past, developing such a product would have been very time intensive and costly, but through simulation the time it takes and the cash investment is slashed.
Design engineers first analyse the structural integrity of propulsion components, using finite element analysis (FEA) software ANSYS Mechanical. The engineering team simulates steady-state, modal and structural dynamics parameters, while also learning about the complete response of each component individually and how they work together. In addition, engineers model internal and external flows for aerodynamic pressure loss estimates and design optimisation, using computational fluid dynamics (CFD) software.
Because heat directly affects product reliability, the temperature of electrical components must remain within a set window. Engineers perform CFD fluid flow and heat transfer analysis using thermal management software ANSYS Fluent to predict temperature and heat rejection, and to design the cooling system, achieving further time and cost savings in the process.
Simulate to innovate
Delivering a propulsion system is not a single discipline assignment. In this case, it takes collaboration of engineers from across Zunum Aero’s power and propulsion groups to explore all the possible designs that could meet the propulsion requirements for the lowest total cost door-to-door aircraft. Through its compatibility and integrations capabilities, simulation software enables multiphysics evaluations for faster design optimisation.
By simulating multiple designs, the design team can analyse more components at a proof-of-concept level in the virtual world, without having to spend time or resources on testing. In fact, it is estimated that without simulation, validating the aircraft would have required nearly double the time. But even more than that, it would have cost millions of dollars in hardware tests.
In the past, major players in the industry would have absorbed this cost, due to the critical nature of conducting the tests, but today they can be replaced – and the testing enhanced – by software.
Flights from thousands of airports that get travellers to their destinations at a fraction of the cost — with less noise to disturb local residents and lower emissions for a healthier planet — is a lofty vision. But through hybrid-electric aircraft, engineered using simulation software, it is a viable one that is quickly moving into sight.