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Rotorcraft Engine-Nacelle Cooling Model Calibration Project PowerPoint Presentation
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College of Engineering and Natural Sciences. Rotorcraft Engine-Nacelle Cooling Model Calibration Project. Nacelle Cooling Solutions Senior Design Team Mechanical Engineering. Nacelle Cooling Solutions: The Team. Presentation Overview. Project Objectives Breakdown of tasks

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Presentation Transcript
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College of Engineering and Natural Sciences

Rotorcraft Engine-Nacelle Cooling Model Calibration Project

Nacelle Cooling Solutions

Senior Design Team

Mechanical Engineering

presentation overview
Presentation Overview
  • Project Objectives
  • Breakdown of tasks
  • Discussion of Computational Model
  • Discussion of Experimental Model
  • Our Vision of the project’s future

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industry standard model
Industry Standard Model
  • Methodology for engine cooling analysis is described in SAE, ARP-996A, “Cooling Data for Turbine Engines in Helicopters”.
  • Originally written in 1967, and last revised in 1986.

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what is arp 996a
What is ARP-996A?
  • Describes a standard method of presenting needed data and calculating the required cooling air for a given engine-nacelle installation in rotorcraft.
  • “Purpose: Efficient design of a turbine engine installation requires … Cooling margins developed by these methods would be subject to full scale testing for verification.”

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project statement
Project Statement
  • Our Objective: Determine a confidence interval to be associated with results obtained from the industry standard model.
  • Our study is based upon the AH-64 installation of the Apache Longbow helicopter.

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project execution
Project Execution
  • Three Main Phases:
    • Computational Model Development
    • Experimental Development
    • Results and Recommendations.
  • Current Status: Completing Computational Stage and beginning Conceptual stage of the test model.

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computation phase i
Computation: Phase I
  • Major Tasks
    • Understanding the underlying theory behind the model described by ARP-996A.
    • Develop a numerical algorithm for the model.
    • Implement a computer program to execute the algorithm.

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experimental phase ii
Experimental: Phase II
  • Major Tasks
    • Develop an appropriately scaled model of the engine-nacelle installation.
    • Design and execute an appropriate experiment.
    • Analyze experimental data and determine a confidence interval.

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results phase iii
Results: Phase III
  • Major Tasks
    • Based on results of data analysis, determine a recommendation for improvements, and/or advice on interpretation of results from ARP-996A methodology.
    • i.e. a fudge factor for the methods described in ARP-996A

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computational model
Computational Model
  • Used to provide numbers for comparison with experiment
  • Based on the model described in SAE ARP-996A
  • Engine is broken lengthwise into several elements
  • Energy balance on each element

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nodal energy balance equations
Nodal Energy Balance Equations
  • Engine surface:
  • Nacelle:
  • Annulus flow:

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solving the energy balance for each element
Solving the Energy Balance for Each Element
  • Energy balance equations
    • Three equations
    • Non-Linear
  • Use Newton’s Method for Non-Linear Systems

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newton s method for nonlinear systems
Newton's Method for Nonlinear Systems
  • Given a vector of n functions, find simultaneous roots for all of them
  • The messy part: calculating the Jacobian matrix

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newton s method for nonlinear systems1
Newton's Method for Nonlinear Systems
  • Solve linear system (J(x))y = F(x)
    • Gaussian elimination or Cramer's rule
    • ARP uses Cramer's rule
    • Easiest to just use \ operator in Matlab
  • set new x = x + y
  • repeat until y is close to zero

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find t 1 or w
Find T1, or W?
  • ARP uses mass flow rate of the annulus as one of the variables in the node equations
  • Using the engine surface temperature instead has advantages
    • Mass flow rate must be the same for each node
    • Temperature can change
    • The math is simpler
    • Required mass flow rate can still be found

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finding the required mass flow the arp way
Finding the Required Mass Flow:The ARP Way
  • Calculate T2, Ta, W for first element
  • Calculate T2, Ta, W for next element
  • Take maximum W
  • Re-Calculate temperatures of previous elements
  • Repeat from 2. for each element
  • Re-calculate required flows from step 1. until converged

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finding the required mass flow the new way
Finding the Required Mass Flow:The New Way
  • Make a guess for the required mass flow W
  • Calculate temperatures throughout engine
  • Are the temperatures all low enough?
    • if yes, then the flow rate is high enough
    • if no, then increase the flow rate and try again

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advantages of the new way
Advantages of the New Way
  • Flow rate is automatically held constant over the entire engine
  • Easier to non-dimensionalize the node equations
  • Easier to calculate the Jacobian matrix
    • Don’t have to deal with changing h with W

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test model development
Test Model Development
  • Based on data for the AH-64 installation, a simplified model can be described.
  • A series of cylinders, with nominal diameters given by scaled AH-64 data.

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physical model concepts
Physical Model Concepts
  • Scale 1:2, 6061 Aluminum to be used, or 15 gauge sheet metal
  • Nacelle circular cross-section to simplify airflow velocity profiles

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experimental heat source concepts
Experimental Heat Source Concepts
  • Resistance wire and a current source.
  • Propane burners

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the next steps to our goal
The Next Steps to Our Goal
  • Material Selection
  • Heating Element Selection
  • Model Construction
  • Test Rig Design and Construction
  • Data Acquisition
  • Execution

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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

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experimental development
Experimental Development
  • What are we trying to achieve?
    • What will the measurements be?
      • Engine Surface Temperature
      • Nacelle Surface Temperature
      • Cooling Air Temperature
    • How will we get the data from the experiment?
      • Appropriate Data Acquisition

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data analysis
Data Analysis
  • What do we do with the data when we’ve run the experiment?
    • Compare surface temperature profiles with those obtained from the computational model.
    • Based on this comparison, determine the confidence interval for the methods described in ARP-996A.

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results and recommendations
Results and Recommendations
  • Based upon the results from the data analysis, we can recommend one of two things:
    • A revision to ARP-996A, consisting of the addition of a warning section describing the accuracy of the methods described there in.
    • A complete revision of ARP-996A, including a new model describing new methods.

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in conclusion
In Conclusion:
  • What are we trying to accomplish?
    • A measure of “goodness” for the 1-D model described in SAE, ARP-996A.
    • Provide data from an appropriate experimental test to back up our conclusions.

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