Robust Optimization of an Aircraft Power Thermal Management System

Abstract

The thermal management of modern aircraft has become more challenging as aircraft capabilities have increased. The use of thermally resistant composite skins and the desired for low observability, reduced ram inlet size and number, has reduced the ability to transfer heat generated by the aircraft to the environment. As the ability to remove heat from modern aircraft has decreased, the heat loads associated with the aircraft have increased. Early in the aircraft design cycle uncertainty exist in both aircraft requirements and simulation predictions. In order to mitigate the uncertainty it is advantageous to design thermal management systems that are insensitive to the design cycle uncertainty. The risk associated with design uncertainty can be reduced through robust optimization. In the robust optimization of the thermal management system three noise factors were selected: 1) engine fan air temperature, 2) avionics thermal load, and 3) engine thrust. The three controllable factors selected for the robust optimization were: 1) compressor pressure ratio, 2) return fuel heat exchanger (RFHX) area, and 3) recuperator heat exchanger (RHX) area. The robust optimization of the thermal management system identified the engine fan air temperature and the avionics thermal load as the dominate noise factors. The worst case noise factor combination resulted in a 258% increase in return fuel heat load. The robust optimization identified the compressor ratio as the dominate control factor followed by the RFHX area. The optimization of the controllable factors resulted in a 51% reduction in the mean return fuel heat load and a 63% reduction in return fuel heat load variance. The risk associated with design cycle uncertainty can be minimized through the employment of the robust optimization methodology. Nomenclature

Experimental Validation of Graph-Based Hierarchical Control for Thermal Management

“…When hydraulic graphs of multiple components are interconnected to represent a system, the hydrodynamics can be represented in the form of Eqs. (6) and (7). The fluid system configuration used for demonstration in this paper consists of closed loops such that fluid mass does not enter or exit the system.…”

“…When thermal graphs of multiple components are interconnected to represent a system, the thermodynamics can be represented in the form of Eqs. (6) and (7). In the notation of the thermal graph variables, Eq.…”

“…Many approaches have been explored to meet this challenge, with a focus on employing transient analyses to improve upon traditional steady-state analyses [4]. These approaches include integrated aircraft modeling [3], characterization of component performance under transient operation [5,6], design optimization [7], improved topologies for thermal management [8], enhanced mission planning [9], and advanced control approaches [10][11][12][13].…”

Cooling Ability/Capacity and Exergy Penalty Analysis of Each Heat Sink of Modern Supersonic Aircraft

“…Jain et al [42] presented an exergy-based objective function to solve the multi-objective optimal control problems for TMS. Bodie et al [43] developed a robust optimization for reducing the effect of uncertainty on TMS, in which three factors are comprehensively considered: EFA temperature, avionics thermal load, and engine thrust. Deppen et al [44] proposed a predictive control strategy which utilizes preview of upcoming loads and disturbances to prevent violation of temperature constraints.…”

Passive Thermal Management for Avionics in High Temperature Environments

“…In fact, thermal management has been identified as the most difficult challenge associated with advanced aircraft design. The difficulty lies with the lack of available sinks, which are limited due to the low thermal conductivity of composite skins, high-altitude and high-speed operation, and Low Observability (LO) requirements 4 . As a result, aircraft fuel becomes the most attractive sink.…”