towards a lighter engine for improved aircraft fuel...

Towards a Lighter Engine for Improved Aircraft Fuel Efficiency – Industrial Collaborative Research on Engine Weight Reduction Technologies

Presented By: Dr. Hamza M. Abo El Ella May 19, 2016

National Research Council

• The National Research Council (NRC) is the primary national research and technology organization (RTO) of the Government of Canada. • A federal government agency for science and technology research.

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National Research Council

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National Research Council

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• Aerospace • Gas Turbine Lab (GTL) • Flight Research Lab (FRL). • Aerodynamics Lab (AL). • Structures, Materials, and Manufacturing Lab (SMM).

Introduction: Gas Turbines for Aircraft Propulsion

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Typical mid-bypass turbofan engine (Pratt & Whitney PW6000)

Fan

Inter-Compressor Duct

Inter-Turbine Duct

LP Turbine

LP Compressor

HP Compressor

Exhaust Mixer

HP Turbine

Introduction: Improving Aircraft Fuel Efficiency

• Improve engine fuel efficiency. • Reduce pressure losses.

• E.g. optimize cavity flows.

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Rotor

Purge flow

Rotor disc

Stator

Cavity at rotor-stator interface

(Abo el ella, 2014)

Introduction: Improving Aircraft Fuel Efficiency

• Reduce engine weight. • Highly-loaded airfoils (reduces blade count but increases secondary

losses – critical for low AR, i.e. HPT).

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ou da y aye u d

Suct o s de eg o o ses oe o teessu e s de eg o

o ses oe o te

Passage vortex

Countervortex

Corner vortex

Boundary layer fluid

Inlet flow Freestream

fluid

Direction of rotation

Suction side leg of horseshoe vortexPressure side leg of

horseshoe vortex

Secondary flows Secondary flows

Introduction: Improving Aircraft Fuel Efficiency

• Reduce engine weight. • Highly-loaded airfoils (reduces blade count but increases secondary

losses – critical for low AR, i.e. HPT). • Must lower secondary losses (endwall contouring).

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(Praisner et al)

Introduction: Improving Aircraft Fuel Efficiency

• Reduce engine weight. • Highly-loaded airfoils (reduces blade count but increases secondary

losses – critical for low AR, i.e. HPT). • Must lower secondary losses (endwall contouring).

• Reduce size or length of ducting and other components. • Inter-compressor duct (ICD). • Inter-turbine duct (ITD). • Exhaust mixer.

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Typical mid-bypass turbofan engine (Pratt & Whitney PW6000)

Fan

Inter-Compressor Duct

Inter-Turbine Duct

LP Turbine

LP Compressor

HP Compressor

Exhaust Mixer

HP Turbine

Inter-Turbine Duct (ITD)

Inter-Turbine Ducts: Objectives

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• Extend the ITD design envelope to achieve: • Minimum length or • Maximum radial offset • with minimal or no

performance penalty.

• Benefits • Reduced engine length. • Reduced fan/LPT RPM. • Reduced LPT stage count. • Reduced engine weight.

Inter-Turbine Ducts: Initial Approach

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• Computational and Experimental Studies on S-shaped ducts. • CFD. • ITD Rig.

• Duct test section. • Upstream swirlers to simulate HPT.

Inter-Turbine Ducts: Initial Approach

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• Three S-shaped aggressive duct geometries (ITD-B, ITD-C, and ITD-D) where designed and tested with a common swirler geometry, and compared to a baseline duct (ITD-A).

ITD-B ITD-C ITD-D

(Mahallati et al, 2013 - GT2013-95065)

Inter-Turbine Ducts: Some Results

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• CFD and experimental results (ITD-B). • Detailed flow information for improved understanding of the

underlying flow physics and loss mechanisms for simple ducts.

(Mahallati et al, 2013 - GT2013-95065)

Inter-Turbine Ducts: Later Approach

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• Subsonic Turbine Rig • Single stage turbine.

• Duct test sections.

Inter-Turbine Ducts: Some Results

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• ITD-D was examined in the subsonic turbine rig to confirm the positive influence of tip leakage vortices in suppressing shroud flow separation.

Inter-Turbine Ducts: Current Approach

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• Numerical approach using engine representative geometry (with experimental validation in subsonic turbine rig). • Struts used for structural support and housing oil supply lines.

• Can be used aerodynamically to enable aggressive designs.

(Mahallati et al)

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Inter-Turbine Ducts: Future Work

• Experimental validation in the subsonic turbine rig. • Experimental validation at high speeds. • Optimizer tools for generating aggressive ITD geometries. • Active flow control strategies.

Exhaust Mixer

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Typical mid-bypass turbofan engine (Pratt & Whitney PW6000)

Fan

Inter-Compressor Duct

Inter-Turbine Duct

LP Turbine

LP Compressor

HP Compressor

Exhaust Mixer

HP Turbine

Exhaust Mixer: Objectives

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• Gain better understanding of flow physics. • Gases mix downstream of the

forced mixer before exiting the nozzle to improve thrust and reduce noise. • Some exhaust systems use

tabs to provide stiffness.

(Wright et al, 2015 - ISABE-2015-20246)

Exhaust Mixer: Approach

• CFD - Unstructured mesh. • Grid independence study

showed 5.5M cells were sufficient.

• Grid is fine enough to resolve wall boundary layers, free shear layers, mixing zones.

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(Wright et al, 2015 - ISABE-2015-20246)

Exhaust Mixer: Some Results

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Streamwise vorticity coefficient (No Tabs) Streamwise vorticity coefficient (With Tabs)

Downstream axial planes at x/Dh=0.07, 0.36, 0.72, 1.45 and 2.90

(Wright et al, 2015 - ISABE-2015-20246)

Total pressure coefficient (No Tabs) Total pressure coefficient (With Tabs)

Exhaust Mixer: Some Results

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Downstream axial planes at x/Dh=0.07, 0.36, 0.72, 1.45 and 2.90

(Wright et al, 2015 - ISABE-2015-20246)

Exhaust Mixer: Other Work

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• Weight reduction – e.g. exhaust casing struts and mixer integration.

• Effect of scalloping on mixer performance. • Effect of inlet swirl.

Exhaust Mixer: Future Work

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• Experimental validation of flow physics. • Active cooling of exhaust mixer for improved durability.

Summary

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• Engine weight reduction for improved aircraft fuel burn • Inter-Turbine Duct. • Exhaust Mixer.

• Collaborating with industry is a must to ensure valid practical solutions.

• N+0.1: 1-2% aircraft fuel burn improvement.

Acknowledgments

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• Ali Mahallati • Alex Wright

Hamza.aboelella@nrc.ca