optimization of passenger individual air nozzles · optimization of passenger individual air...

Optimization of passenger individual air nozzles

March 2017Optimization of passenger individual air nozzles

STAR Global Conference 2017

Andreas RUCH

Environmental Control Systems Airbus Operations GmbH

© AIRBUS Operations GmbH. All rights reserved. Confidential and proprietary document.

Content


• Introduction

• Problem description: Purpose of individual air outlets, requirements and

motivation for optimization

• Parametric model creation and setup of automated optimization

• Results: Baseline design, automated design optimization and optimum

solution found

• Summary & Conclusion


Introduction – Airbus Commercial Aircraft at a glance


55,000Employees

€45.8billionAnnual revenue*

10yrsBacklog

400Operators

Data to end 2015

Passion

-Our global workforce is

united by a passion for

aviation and restless

desire to create better

ways to fly


Introduction – Airbus Commercial Aircraft at a glance



Introduction – Where we use CFD in Environmental Control Systems Design



Individual air nozzles – Purpose


• Individual air outlets can be found in many

aircraft models flying today

• Many different variants are existing

• Main reason given for use of nozzle:

• Reduction of ‚stuffiness‘ of air

• After boarding (first 30min) 70% of occupants open

nozzle (higher metabolism, entering from outside)

• Use of nozzles reduces to 62% after 40min, then

constant

• Most occupants target nozzle to upper body part

(52%), 32% to lower body, 15% to head

(head is a very sensitive area; upper body matters

most for overall thermal sensation)

(Source: “Experimental investigation of personal air supply nozzle use in

aircraft cabins”; Zhaosong Fang, Baizhan Li, Andrew N. Baldwin; 2015)


Individual air nozzles – Purpose

→ With ambient temperatures of >27°C, average velocities of 0.8 m/s

are perceived as comfortable

→ Air velocity is an important factor


Source: Ceiling Fans as Extenders of the

Summer Comfort Envelope; F.H. Rohles, F.H.,

S.A. Konz, B.W. Jones; 1983;

Source: ANSI/ASHRAE Standard 55-2013


Individual air nozzles – Motivation for design improvements

• Amount of air that can be supplied to the individual air nozzles is limited by

the overall air system performance

• Maximum pressure loss of the individual air nozzles is also limited:

• Pressure in supply manifold is driven by overall air system performance

• Generally, less pressure loss also means less noise generation



Individual air nozzles – Requirements

• Taking all previously mentioned considerations

into account, the requirements (i.e. pass/fail

criteria) can be summarized as follows:

• In the plane 1 m below the nozzle: A maximum air

velocity (magnitude) of 0.8 m/s shall be reached

• In the plane 1 m below the nozzle: In an area of at

least 300 cm^2 the air velocity (magnitude) shall

be above 0.5 m/s

• The maximum total pressure at the inlet shall be

minimized and stay below 300 Pa


1m

300 cm^2


Parametric model – Geometry


Wall

Pressure

outlet

Velocity

inlet

Inner part

• CATIA V5 was used to create a rotational-symmetric model

• The inner part, which defines the shap of nozzle is defined by a parametric

sketch


Parametric model – Design parameters


R1

L2

gamma

alpha

L3L1

beta

R2

R1

gap

ph1, ph2 and ph3 are parameters

that are used to define relations

between other constraints


Parametric model – Design parameters

• It is important that the parametric model enables as many different designs as

possible in order to exploit most of the available design space. However, the chosen

parameters may lead to impossible geometries. Defining relations between

parameters minimizes the generation of invalid geometries:


L1


Parametric model – Possible designs with the given parameters



Setup of CFD model – Mesh and physics definition

Mesh:

• Trimmed mesh, cell count was

around 4 million for all models

• Three volume controls for

refinements in the jet region

• 5 prism layers

Continuum setup:

• 3D steady state

• Segregated flow solver

• Constant density air

• SST k-ω turbulence model

• All y+ wall treatment



Setup of CFD model – Monitors, stopping criteria

Monitors:

Moving average over last 500 iterations

(field mean monitor with sliding window)

for all target quantities (c_max, p_tot and

CoreArea)

Stopping criteria:

• Asymptotic limits (max-min) over last

500 iterations:

• 0.1 m/s for c_max

• 10.0 Pa for p_tot

• 5.0 cm^2 for CoreArea

• Maximum allowed iterations: 15000

(design considered invalid, if this limit is

reached)



Results – Baseline design



Results – Automated design optimization

• As both the minimization of the pressure loss and the air flow rate was an

objective, the air flow rate as added to the optimization as a non-geometric

parameter

• Simulations were run on 96 CPUs (4.75 day in total)

• Number of simulations:

• Total: 175

• Feasible designs: 35 = 20%

• Infeasible designs: 79 = 45 %

• Errors during creation of geometry: 61 = 35 % (quite high, target should be

around 10%)



Parametric model – Pressure drop



Parametric model – Velocity field of different designs



Results – Parallel plot of all designs


• For the best designs, following important parameters can be identified:

• beta (angle of inner cone): around 30 to 35 deg

• gap: always around 3.2 to 3.5 mm

• L3 & R1: both values together implicitely define the inner diameter of nozzle (outer part)

• air flow rate: all best designs have similar air flow rates to today’s design


Results – Top design



Results – Comparison between baseline and top design

Total pressure difference between inlet and end of upper cone is small and similar for

both designs (14.8 Pa for baseline, 5.2 Pa for top design).

→ Major part of pressure loss not created here, only little margin for improvement!


Baseline design Top design


Results – Comparison between baseline and top design

→ Dynamic pressure at nozzle outlet significantly lower and more equally distributed

at optimized design!


Baseline design Top design


Summary & conclusion


• A significant improvement of the pressure loss

charactaristic could be achieved while meeting all

performance requirements (air flow rate, air velocities,

core area of the jet)

• Turnaround time for actuall optimization process less

than a week!

• Biggest challenge remains creation of the CAD-input:

• Definition of meaningful parameters – otherwise the

intepretation is difficult

• Robustness of the geometry: failure rate should be low in

order to make sure that no good design is overlooked

• Further work to be done:

• Check of manufacturing and industrial design aspects

• Test of a prototype for validation of performance and

accoustical behavior



© Airbus Operations GmbH. All rights reserved. Confidential and proprietary document. This document and all information contained herein is the sole property of Airbus Operations GmbH. No intellectual property rights are granted by the delivery of this document

or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of Airbus Operations GmbH. This document and its content shall not be used for any purpose other than that for which it is

supplied. The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, Airbus Operations GmbH will be pleased to

explain the basis thereof. AIRBUS, its logo, A300, A310, A318, A319, A320, A321, A330, A340, A350, A380, A400M are registered trademarks.

optimization of passenger individual air nozzles · optimization of passenger individual air...

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