Rotorcraft Engine-Nacelle Cooling Model Calibration Project

Rotorcraft Engine-Nacelle Cooling Model

Calibration Project

Nacelle Cooling SolutionsSenior Design Team

Mechanical Engineering

College of Engineering and Natural Sciences

19 November 200419 November 2004 NCSNCS

Nacelle Cooling Solutions: The Nacelle Cooling Solutions: The TeamTeam

Jason LeeJason LeeTeam LeaderTeam Leader

Theran CochranTheran CochranTeam SecretaryTeam Secretary

Colby HuffmonColby HuffmonTeam Financial OfficerTeam Financial Officer

David TallmanDavid TallmanProductions ManagerProductions Manager

Technical Advisor: Dr. Earl P. N. DuqueTechnical Advisor: Dr. Earl P. N. Duque


Presentation OverviewPresentation Overview

Project ObjectivesProject Objectives

Breakdown of tasksBreakdown of tasks

Discussion of Computational ModelDiscussion of Computational Model

Discussion of Experimental ModelDiscussion of Experimental Model

Our Vision of the project’s futureOur Vision of the project’s future

Stephanie Hilliard

Adding some type of graphic to break up textg


Industry Standard ModelIndustry Standard Model

Methodology for engine cooling analysis Methodology for engine cooling analysis is described in SAE, ARP-996A, is described in SAE, ARP-996A, “Cooling Data for Turbine Engines in “Cooling Data for Turbine Engines in Helicopters”.Helicopters”.

Originally written in 1967, and last Originally written in 1967, and last revised in 1986.revised in 1986.

Stephanie Hilliard


What is ARP-996A?What is ARP-996A?

Describes a standard method of Describes a standard method of presenting needed data and calculating presenting needed data and calculating the required cooling air for a given the required cooling air for a given engine-nacelle installation in rotorcraft.engine-nacelle installation in rotorcraft.

““Purpose:Purpose: Efficient design of a turbine Efficient design of a turbine engine installation requires … engine installation requires … Cooling Cooling margins developed by these methods margins developed by these methods would be subject to full scale testing would be subject to full scale testing for verification.”for verification.”


Project StatementProject Statement

Our ObjectiveOur Objective: Determine a confidence : Determine a confidence interval to be associated with results interval to be associated with results obtained from the industry standard obtained from the industry standard model. model.

Our study is based upon the AH-64 Our study is based upon the AH-64 installation of the Apache Longbow installation of the Apache Longbow helicopter.helicopter.


AH-64 DataAH-64 Data

Stephanie Hilliard

cannot read, make better.


Project ExecutionProject Execution

Three Main Phases:Three Main Phases: Computational Model DevelopmentComputational Model Development Experimental DevelopmentExperimental Development Results and Recommendations. Results and Recommendations.

Current StatusCurrent Status: Completing : Completing Computational Stage and beginning Computational Stage and beginning Conceptual stage of the test model.Conceptual stage of the test model.


Computation: Phase IComputation: Phase I

Major TasksMajor Tasks

Understanding the underlying theory behind Understanding the underlying theory behind the model described by ARP-996A.the model described by ARP-996A.

Develop a numerical algorithm for the Develop a numerical algorithm for the model.model.

Implement a computer program to execute Implement a computer program to execute the algorithm.the algorithm.


Experimental: Phase IIExperimental: Phase II


Develop an appropriately scaled model of Develop an appropriately scaled model of the engine-nacelle installation.the engine-nacelle installation.

Design and execute an appropriate Design and execute an appropriate experiment.experiment.

Analyze experimental data and determine Analyze experimental data and determine a confidence interval. a confidence interval.


Results: Phase IIIResults: Phase III


Based on results of data analysis, determine Based on results of data analysis, determine a recommendation for improvements, and/or a recommendation for improvements, and/or advice on interpretation of results from ARP-advice on interpretation of results from ARP-996A methodology.996A methodology.

i.e. a fudge factor for the methods described i.e. a fudge factor for the methods described in ARP-996Ain ARP-996A


Computational ModelComputational Model

Used to provide numbers for comparison Used to provide numbers for comparison with experimentwith experiment

Based on the model described in SAE Based on the model described in SAE ARP-996AARP-996A

Engine is broken lengthwise into several Engine is broken lengthwise into several elementselements

Energy balance on each elementEnergy balance on each element


1-D Model Schematic1-D Model Schematic


Nodal Energy Balance Nodal Energy Balance EquationsEquations

Engine surface:Engine surface:

Nacelle:Nacelle:

Annulus flow:Annulus flow:

IN222111 2 a,apaaaaa TTcW=TTAh+TTAh

44

222222

2224

24

1112

TTσAε+TTAh+

TTAh=TTσAε

ab

aa

42

41112111 TTσAε+TTAh=Lq aa


Solving the Energy Solving the Energy Balance for Each ElementBalance for Each Element

Energy balance equationsEnergy balance equations Three equationsThree equations Non-LinearNon-Linear

Use Newton’s Method for Non-Linear Use Newton’s Method for Non-Linear SystemsSystems


Newton's Method for Newton's Method for Nonlinear SystemsNonlinear Systems

Given a vector of Given a vector of n n functions, find functions, find simultaneous roots simultaneous roots for all of themfor all of them

The messy part: The messy part: calculating the calculating the Jacobian matrixJacobian matrix n=ji,

x

F=J

j

i

1

0

x

x

x

x

)(

)(

)(

)(

3

2

1

f

f

f

F


Newton's Method for Newton's Method for Nonlinear SystemsNonlinear Systems

Solve linear system (J(Solve linear system (J(xx))))yy = F( = F(xx)) Gaussian elimination or Cramer's ruleGaussian elimination or Cramer's rule ARP uses Cramer's ruleARP uses Cramer's rule Easiest to just use \ operator in MatlabEasiest to just use \ operator in Matlab

set new set new xx = = xx + + yy

repeat until repeat until yy is close to zero is close to zero


Find Find TT11, or , or WW??

ARP uses mass flow rate of the annulus as ARP uses mass flow rate of the annulus as one of the variables in the node equationsone of the variables in the node equations

Using the engine surface temperature Using the engine surface temperature instead has advantagesinstead has advantages Mass flow rate must be the same for each nodeMass flow rate must be the same for each node Temperature can changeTemperature can change The math is simplerThe math is simpler Required mass flow rate can still be foundRequired mass flow rate can still be found


Finding the Required Mass Flow:Finding the Required Mass Flow:The ARP WayThe ARP Way

1.1. Calculate TCalculate T22, T, Taa, W for first element, W for first element

2.2. Calculate TCalculate T22, T, Taa, W for next element, W for next element

3.3. Take maximum WTake maximum W

4.4. Re-Calculate temperatures of previous Re-Calculate temperatures of previous elementselements

5.5. Repeat from 2. for each elementRepeat from 2. for each element

6.6. Re-calculate required flows from step 1. Re-calculate required flows from step 1. until convergeduntil converged


Finding the Required Mass Flow:Finding the Required Mass Flow:The New WayThe New Way

1.1. Make a guess for the required mass flow Make a guess for the required mass flow WW

2.2. Calculate temperatures throughout Calculate temperatures throughout engineengine

3.3. Are the temperatures all low enough?Are the temperatures all low enough? if yes, then the flow rate is high enoughif yes, then the flow rate is high enough if no, then increase the flow rate and try if no, then increase the flow rate and try

againagain


Advantages of the New WayAdvantages of the New Way

Flow rate is automatically held constant Flow rate is automatically held constant over the entire engineover the entire engine

Easier to non-dimensionalize the node Easier to non-dimensionalize the node equationsequations

Easier to calculate the Jacobian matrixEasier to calculate the Jacobian matrix

Don’t have to deal with changing Don’t have to deal with changing hh with with WW


Non-dimensional Nodal Non-dimensional Nodal Energy Balance Energy Balance

0

011

01

IN22113

41

421

42223222

42

411111

aa,aa

a

a

θθM+θθC+θθC=f

θθR+θR+θC+θθC=f

=θθR+θθC=f

Lq

TWc=M,

Lq

TσAε=R,

Lq

TσAε=R

Lq

TAh=C,

Lq

TAh=C,

Lq

TAh=C

bpbb

bbbaba

24112

2

4112

1

223

222

111

aINa,=iT

T=θ

b

ii 2,1,;

Stephanie Hilliard

Not clear that this is nodal.


Test Model DevelopmentTest Model Development

Based on data for the AH-64 Based on data for the AH-64 installation, a simplified model can installation, a simplified model can be described.be described.

A series of cylinders, with nominal A series of cylinders, with nominal diameters given by scaled AH-64 diameters given by scaled AH-64 data.data.

Stephanie Hilliard

emphasize that we are in the conceptual stage, what are the concepts


Our Physical Model GeometryOur Physical Model Geometry

Stephanie Hilliard

break out and illustrate the concepts from here.


Physical Model ConceptsPhysical Model Concepts

Scale 1:2, 6061 Aluminum to be used, or Scale 1:2, 6061 Aluminum to be used, or 15 gauge sheet metal15 gauge sheet metal

Nacelle circular cross-section to simplify Nacelle circular cross-section to simplify airflow velocity profilesairflow velocity profiles


Experimental Heat Source Experimental Heat Source ConceptsConcepts

Resistance wire and Resistance wire and a current source.a current source.

Propane burners Propane burners


Engine with NacelleEngine with Nacelle

Stephanie Hilliard

make more clear, change colors and hide planes.


The Next Steps to Our GoalThe Next Steps to Our Goal

Material SelectionMaterial Selection

Heating Element SelectionHeating Element Selection

Model ConstructionModel Construction

Test Rig Design and ConstructionTest Rig Design and Construction

Data AcquisitionData Acquisition

ExecutionExecution


Phase II: Schedule Phase II: Schedule

Phase II

Experimental Development:

Including Test model development

Design of Experiment

Procurement and Construction

Experiment Execution:

Including Data Analysis


Experimental DevelopmentExperimental Development

What are we trying to achieve?What are we trying to achieve?

What will the measurements be?What will the measurements be?

Engine Surface TemperatureEngine Surface Temperature

Nacelle Surface TemperatureNacelle Surface Temperature

Cooling Air TemperatureCooling Air Temperature

How will we get the data from the How will we get the data from the experiment?experiment?

Appropriate Data AcquisitionAppropriate Data Acquisition

Stephanie Hilliard

more direct throughout the presentation. avoid passive voice.

Stephanie Hilliard

Clear up, OBJECTIVES


Data AnalysisData Analysis

What do we do with the data when we’ve What do we do with the data when we’ve run the experiment?run the experiment? Compare surface temperature profiles with Compare surface temperature profiles with

those obtained from the computational those obtained from the computational model.model.

Based on this comparison, determine the Based on this comparison, determine the confidence interval for the methods confidence interval for the methods described in ARP-996A.described in ARP-996A.


Results and RecommendationsResults and Recommendations

Based upon the results from the data Based upon the results from the data analysis, we can recommend one of two analysis, we can recommend one of two things:things: A revision to ARP-996A, consisting of the A revision to ARP-996A, consisting of the

addition of a warning section describing the addition of a warning section describing the accuracy of the methods described there in. accuracy of the methods described there in.

A complete revision of ARP-996A, including A complete revision of ARP-996A, including a new model describing new methods.a new model describing new methods.

Stephanie Hilliard

Bldg. 510


In Conclusion:In Conclusion:

What are we trying to accomplish?What are we trying to accomplish?

A measure of “goodness” for the 1-D model A measure of “goodness” for the 1-D model described in SAE, ARP-996A.described in SAE, ARP-996A.

Provide data from an appropriate Provide data from an appropriate experimental test to back up our experimental test to back up our conclusions.conclusions.


Any Questions?Any Questions?

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Rotorcraft Engine-Nacelle Cooling Model Calibration Project