DESIGNING A SIMPLE LINKAGE BETWEEN TWO FUEL TANK RESERVOIRS

Designing a Simple Linkage between Two Fuel Tank Reservoirs



Designing a Simple Linkage between Two Fuel Tank Reservoirs

Summary

Using an aircraft fuel tank as an industrial case-study, the paper describes some recent research developments at BAE SYSTEMS that allow the airframe and systems life-cycles to become better aligned with linkage between two fuel tank reservoirs. In particular, the paper demonstrates that the design and analysis of the fuel system can be integrated with the airframe structure linking two fuel tanks (McAdsms, 1942: 241). This will reduce qualification times in the future and enable Simulation Based Acquisition (SBA), that is, the procurement of aircraft based on synthetic results rather than physical testing.

This project covers different domains: product development, design and construction, computer modeling and analysis, and testing and experimental investigation. It includes different learning tasks, such as programming, functionality of DSP-based system and prototyping approach using higher level language like MATLAB

Introduction

The current generation of military aircraft requires a prolonged and costly activity to develop and qualify the fuel system. This involves a combination of performance analysis, fuel rig and flight test programmes, culminating in system qualification (Smith & Hallett, 1954: 1486).

The qualification includes gauging analysis of tank contents, one-dimensional network analysis for pressure, flow and thermal distributions, as well as the selective use of Computational Fluid Dynamics (CFD) for three-dimensional flow analysis. Each of these analyses is currently performed separately and the results are summarised in a form suitable for simulation of the overall fuel system. This is used as a means of demonstrating system capability and predicting performance. Subject to appropriate validation, operational scenarios can be investigated in detail on an engineering workstation (Witte, 1954: 168). This reduces the uncertainty in design and the amount of (expensive) system testing.

The Flight Control System (FCS) requires the continuous estimation of fuel mass and centre of gravity (CG). These can be derived from the mass and CG of individual fuel cells for any combination of aircraft pitches and rolls angles. For a specific cell, this is constructed as a relationship between the volume of fuel and the height of the equilibrium-free fuel surface, as illustrated in Figure 1 (Waite, 1955: 158). Currently, CATIA V4 solids representing the fuel in each cell are first constructed. An in-house software application then repeatedly splits each fuel cell solid with gauging planes which take into account the aircraft pitch and roll angles and percentage divisions along the length of the gauge probe.

The application analyses the remaining fuel solids for their volumes and CGs and produces text file output. This is applied to each gauge probe and typically considers 55 combinations of pitch and roll angles and 21 equally-spaced percentage lengths, i.e. a total of 1155 solid split operations and analysis interrogations. Inevitably, this analysis provides no information beyond the physical extremes of the gauge probe. A fuel cell can fill above 100% of the wetted probe length, in which case, the excess fuel is ...