by Ben Chiswick, director of engineering enterprise growth at Drive System Design
The eVTOL trade is without doubt one of the fastest-moving sectors in aerospace and it’s set for continued fast progress. Because of this, producers are shifting shortly to capitalize on this and procure a aggressive benefit.
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Maybe the most important efficiency differentiator on this house would be the propulsion programs. In the end, this dictates the load capability, vary and pace. It additionally closely influences price.
As a comparatively new sector, the eVTOL market is but to seek out any widespread floor on electrified propulsion programs and has not progressed in direction of a set structure. That is comprehensible as there’s a myriad of selections to be made, together with motor sort, battery know-how, rim-driven or hub-driven followers, the variety of propulsion modules, multi-speed or direct drive, the record goes on.
There are actually a whole lot of 1000’s of doable propulsion structure mixtures. This leaves quite a lot of scope to get issues flawed.
In addition to figuring out the right structure, producers are additionally balancing the usage of bespoke components, to supply a aggressive answer, with off-the-shelf elements, to fulfill their time-to-market and value objectives. At both finish of this scale, how these elements are built-in performs a key function within the system’s total efficiency.
Simulation to extend understanding
The one life like approach to examine and analyze all these choices is thru the usage of simulation. Nevertheless, key to getting correct outcomes isn’t simply modeling the person elements however understanding the advanced interactions all through your complete system.
Ben Chiswick, engineering enterprise growth director, Drive System Design
At Drive System Design, we have now developed our personal in-house simulation answer referred to as ePOP (electrified Powertrain Optimisation Course of). It evaluates electrical propulsion architectures for a given eVTOL vary, plane sort, payload and flight profile.
We now have used ePOP to review the trade-offs that have to be made and spotlight widespread questions being requested.
For instance, what’s the optimum dimension and variety of propulsion modules for an eVTOL? Presently, many trade gamers are prepared to soak up the extra mass of extra modules to learn from the possibly improved effectivity it presents.
Our research exhibits that this strategy does certainly enhance effectivity. Transferring from 4 to eight propulsion modules doubles the powertrain mass however halves the power consumed over a flight cycle.
Nevertheless, our analysis additionally exhibits {that a} six module answer presents 75% of the identical power saving at half the rise in system mass. This highlights the necessity for optimization and discovering a ‘candy spot’ for a given software.
Design choices
One other vital consideration is rim-driven followers (RDF) versus hub-driven followers (HDF), every providing execs and cons. An RDF system can provide aerodynamic effectivity positive factors alongside the power to extra readily stack fan levels and introduce contra-rotating designs.
Nevertheless, a RDF system necessitates a clear sheet design that can require certification. This may be difficult for start-ups, which make up a big proportion of the eVTOL market.
The choice is to make use of a standard motor topology that may be leveraged from different sectors as a part of a industrial off-the-shelf (COTS) HDF system.
An more and more widespread query now being requested on this sector is whether or not or to not use a discount gearbox. Can the load penalty be counteracted by effectivity enhancements? The brief reply is sure, it may possibly, however understanding the place requires a radical understanding of the general system interactions.
Our case research confirmed {that a} direct drive design can restrict the effectivity of the system and {that a} well-integrated discount gear system answer can present decrease power consumption over a flight profile regardless of the extra mass.
The opposite consideration to make is that though a transmission does add price, weight and complexity it additionally gives vital flexibility in how greatest to realize the general power consumption goal. It does this by maintaining the motor inside it’s most effective working window for the next proportion of the flight cycle.
In such a aggressive market house it’s essential to not solely get it proper the primary time but additionally be the primary to get it proper. These two aims can usually be conflicting.
As a key efficiency differentiator, will probably be unsurprising information that there is no such thing as a one-size-fits-all electrical propulsion answer for the eVTOL market. Nevertheless, with a full-system strategy to simulation and a radical understanding of the advanced system interactions, propulsion programs will be confidently optimized for a selected software in the course of the idea section of the challenge, means earlier than investing in detailed engineering and {hardware}.
This text was supplied by Drive System Design, an engineering consultancy specialising within the design, growth and management of future transmission and driveline programs.
