Aircraft Fuel Pump Design and Optimization

Introduction to Aircraft Fuel Pumps

Aircraft fuel pumps are one of the most important elements of a fuel system. The operating characteristics and reliability of it are critical for the performance and safety of the aircraft.

Usually, the inlet pressure of the aircraft fuel pump is very low, for example, the aircraft fuel pump of a commercial aircraft needs to operate at altitudes up to 45,000 feet, where the standard atmospheric pressure is about 2.14 psi (about 0.146 atm). What’s more, because fuel is the only consumable fluid carried by the aircraft, it needs to provide all of the cooling necessary for the proper function of the airframe and engine systems. As a result, the temperature of the fuel in the pump increases significantly. The vapor pressure of common fuel used in aircraft gas turbine engines, like Jet A, Jet B, JP-4 etc., gets higher as the temperature increases. Cavitation may occur when the local static pressure in the fluid drops below the vapor pressure of the fuel.

It is very important to avoid the cavitation problem when designing the aircraft fuel pump, because it will cause serious wear, tear, damage of the impeller and performance penalty, which reduces the pumps’ lifetime dramatically. In order to prevent cavitation and have a better suction performance, aircraft fuel pumps use inducers either alone or in conjunction with radial or mixed-flow impeller depending upon the flow and pressure requirements. Figure 1 shows an assortment of fuel pump impellers including radial, mixed flow and inducer types. [1]

Fuel Pump Impeller
Fig.1 Various Fuel Pump Impellers
Designing an Aircraft Fuel Pump with AxSTREAM®

AxSTREAM® helps create new designs, analyze existing designs and retrofit equipment. Users can optimize the flow path of fuel pumps from scratch using a small number of basic input parameters and a set of geometric constraints. Then users can get the specific design desired by editing and smoothing the flow path interactively, making sure the pump performance is as expected. Figure.2 shows some fuel pump designs with different flow path users can get from AxSTREAM®. Note that an inducer and a centrifugal impeller can be made as an integral part which also can be designed in AxSTREAM®, as shown in the right bottom of Figure 2.

Flow Path Capability
Fig.2 Flow Path Capability

The Fluid Designer™ (AxFDesigner) in AxSTREAM® allows users to create custom fluid files to be utilized for any pure fluid or a mixture of single species from the several reliable fluid properties databases (NIST RefPROP and Simulis Thermodynamic by ProSIM, etc.). This allows for very accurate treatment of fluid properties at each station along the hydraulic path and for all intended pump operating modes.  A user can select the required common jet fuels (for example, Jet A) directly from Fluid library, as shown in Figure 3.

AxFDesigner Fluid Designer
Fig.3 AxFDesigner™ Fluid Designer

 

The AxMAP™ module in AxSTREAM® is an effective tool to study the influence of operational parameters on pump performances. This module makes use of state-of-the art 1D/2D meanline/streamline solver taking into account real loss mechanisms. AxSTREAM® users commonly report faster compute times with good accuracy for this module.

Figure 4 shows a 3D view of a fuel pump designed from and based on 3/4 section view of Eaton fuel pump type 8810 (shown below) and its performance characteristics (taken from an open source).

Fuel Pump Optimized in AxSTREAM
Fig.4 Fuel Pump Optimized in AxSTREAM®

Figure 5 shows the performance curve of the designed in AxSTREAM® fuel pump.

Aircraft Fuel Pump Performance Curves in AxMAP
Fig.5 Aircraft Fuel Pump Performance Curves in AxMAP™
Validation of Results

Once the preliminary and detailed design of the aircraft fuel pump has been completed, a user can easily use the AxSTREAM® embedded AxCFD™ to validate the performance and flow behavior utilizing 3D CFD technology.

Figure 6 shows the CFD analysis solution of the AxSTREAM® designed fuel pump in AxCFD™. From the velocity contour, a pump designer can identify the vortex region in the stator and resolve this flow in a consequent design iteration. AxCFD™ allows users to evaluate a pump design early in the development process and make critical design decisions to better utilize development costs.

Fuel Pump CFD
Fig.6 CFD Analysis Solution of the Designed Fuel Pump in AxCFD™

AxSTRESS™ is a structural, modal and harmonic analysis solver using a Finite Elements Method with a customizable, automatic turbomachinery-specific mesh generation, which is also a part of AxSTREAM® platform. Figure 7 shows the stress and displacement contour of the AxSTREAM® designed fuel pump obtained by AxSTRESS™.

Mesh in AxSTRESS
Fig.7 Mesh and Von Mises Stress Contour Obtained by AxSTRESS

Learn more about how AxSTREAM® can help you and your team here or Contact Us for more information!

Reference:

[1] I. Karassik, J. Messina, P. Cooper and C. Heald (2008) Pump Handbook,4th edition, McGraw-Hill, pp 12.367–12.395.

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