Component-led integrative optimisation methodology for avionic thermal management

The modern military aircraft can be defined as a System of Systems (SoS); several distinct systems operating simultaneously across boundary interfaces. As the on-board subsystems have become more complex and diverse, the development process has become more isolated. When considering thermal management of distributed heat loads, the aircraft has become a collection of individually optimised components and subsystems, rather than the implementation of a single system to perform a given task. Avionic thermal management is quickly becoming a limiting factor of aircraft performance, reliability and effectiveness. The challenge of avionic thermal management is growing with the increasing complexity and power density of avionic packages. The aircraft relies on a heat rejection growth capacity to accommodate the additional through-life avionic heat loads. Growth capacity is defined as an allowable thermal loading growth designed into the system by the underutilisation of spatial and cooling supply at aircraft introduction; however, this is a limited resource and aircraft subsystem cooling capability is reaching a critical point. The depleted growth capacity coupled with increased avionic power demands has led to component thermal failure. However, due to the poor resolution of existing data acquisition, experimental facilities or thermodynamic modeling, the exact inflight-operating conditions remain relatively unknown. The knowledge gap identified in this work is the lack of definitive methodology to generate high fidelity data of in-flight thermal conditions of fast-jet subsystems and provide evidence towards effective future thermal management technologies. It is shown that, through the development of a new methodology, the knowledge gap can be reduced and as an output of this approach the unknown system behaviour can be defined. A multidisciplinary approach to the replication, analysis and optimisation of a fast-jet TMS is detailed. The development of a new Ground Test Facility (GTF) allows previously unidentified system thermal behaviour to be evaluated at component, subsystem and system level. The development of new data to characterise current thermal performance of a fast jet TMS allows recommendations of several new technologies to be implemented through a component led integrative system optimisation. This approach is to consider the TMS as a single system to achieve a single goal of component thermal management. Three technologies are implemented to optimise avionic conditions through the minimisation of bleed air consumption, improve avionic reliability through increased avionic component isothermalisation and increase growth capacity through improved avionic heat exchanger fin utilisation. These component level technologies improved system level performance. A reduction in TMS bleed air consumption from 1225kg to 510kg was found to complete a typical flight profile. A peak predicted aircraft specific fuel consumption saving of 1.23% is seen at a cruise flight condition because of this approach to avionic thermal management.