WP8 – Influence of platform behaviour on sub-system design
A gas turbine engine influences, and is influenced by, the platform it is attached to (e.g. a particular aircraft) and the manner in which it is attached. However, much of the academic research on engine structural performance is done without much detail on this context, instead making significant assumptions on the respective influences. This means the results of these studies must be interpreted with this assumption in mind. One major reason for not including this contextual information is that for traditional platforms there is little information in the public domain about these respective influences, and for new and emerging platform concepts this information is likely to be unknown.
One route to determining this information is using computer simulation, where methods such as Computer Aided Design, Finite element analysis, and Computational fluid dynamics can be combined to create virtual representations of a platform concept, and to assess its performance for a range of different operational scenarios. Such approaches have been proven highly effective and accurate for this application and are widely trusted in the community.
One issue with this approach is that the creation of detailed computer models is a highly skilled task, requiring significant time to prepare the models, and long computational runtimes to get the results. While this is appropriate for studies near to the end of the design process, when the product definition is well matured and the simulation is used to aid verification, this time and skill requirement is a barrier to being able to use computational tools earlier in the design process, when understanding on the influences of new platform concepts on sub-systems, such as the engine, are necessary to understand the feasibility of concepts and to understand the impact of design changes. And so, there are important research questions about how to make the computational simulation process better suited to understanding these influences for new design concepts. This will include questions about what ways should the platform and subsystems be modelled to provide sufficiently detailed results in the shortest possible time?, what represents sufficient detail for the types of understanding that is being sought?, how can these processes be automated to reduce preparation skill and time?
One of the considerations during early design stages is to understand the impact of the platform design on the engine response to “extreme events”. Such events are not part of a typical system’s operational cycles, but have the potential to cause significant loading on the entire system and so must be considered, and designed for, when developing a product.
“Fan-blade-off” is one such extreme event. It is when a blade of the fan at the front of the engine is released during operation. Due to the speed the fan is rotating at, and the mass of the individual blades, this is a very high energy event. When a fan-blade-off event happens there are stringent regularity requirements about how the blade must contained during such an event. While these events are simulated using finite element analysis today, the process of doing so is incredibly expensive. The nature of the solvers used means that the model needs to be meshed in a specific way which cannot be achieved automatically and takes a lot of time and skill to achieve manually. Also, during the events there are many unknowns that the simulation model needs to be setup to cater for, and many boundary conditions that need to be applied. As such, these simulations are carried out late in the design process when the concept is mature.
Within Cornerstone WP8, the aim has been to investigate how a platform influences the response to fan-blade-off event for a new aircraft concept, earlier in the design process, to help determine the suitability of the platform and subsystem combinations. The goal is to provide a capability which allows the influence on the structural behaviour of the platform on the forces experienced by the engine during a fan-blade-off event to be rapidly simulated, and so quick and early assessments to be made about the suitability of the use of the sub-system on a given platform.