April 3, 2018

Dr. Anthony J Dean, PhD

Combustion Summer School 2018 – Day 3

Engine Fundamentals…….Powering & Moving Our World

Plan for Today

Morning

• Propulsion and Power Context

• Global Trends & Drivers for Change

• Combustion Systems

• Combustion Design

Afternoon

• Gas Turbine Engine Design Workshop

Imagine….Propulsion

Next Generation Air-breathing Combustion

…. More efficient, lower emissions: GE 9x 1st flight in 2018

I-A - First U.S. jet engine

1941: 1st US jet engine

1958/1965: 1st Mach 2 and 3Supersonic Propulsion

Jet Engine Propulsion

1903: Washington to Tokyo in 3 months

1903: Wright BrothersReciprocating engines

Powered Flight

GE90-115

2006: Washington to Tokyo in 12 hours

2003: GE 90-115B

Largest & Quietest

Low Low High High CombustorLow Low High High Combustor

GE90-115

2018 – H and J-class combined cycle gas turbines

2016 article: http://www.powermag.com/siemens-ge-mhpsa-advance-gas-power-efficiency/?pagenum=2

• Pressure ratio 20-30

• Power (Simple Cycle) 350 – 500 MW

• Efficiency (Combined Cycle) >60%

1939: 4MW at 17.4% efficiency….2018: 1188 MW at 63.08% (3 GT in 1 CC plant)

Imagine….Power Generation

• Pressure ratio 4.4

• Power 4MW

• Efficiency 17.4%

1939 – 1st commercial power generation gas turbine (Switzerland)

1188 MW 2.7 million average homes in Japan

Global Trends

• Competitive Pressure - Fuel Usage & Fuel Prices• GHG Awareness• Clean Air Awareness• Unconventional Oil & Gas• Biofuels

Combustion Moves and Powers our World…..continued growth projected through 2035

Source: BP 2017

• Growth in developing regions will offset declines in developing world

• Gas: projected growth- 1.2B people still without reliable

power

• Oil: growth in Aviation- passenger-mile traffic continues to

grow

Source: BP statistical Source of World Energy 2015

Cost: Global Demand and Fuel Price Volatility

Cost focus drives innovation for efficiency

Green House Gas Awareness (CO2, CH4, ….)

Drives innovation for efficiency and alternative fuels

http://cdiac.ornl.gov/

Air Quality Awareness

http://aqicn.org

April 1, 2018: http://aqicn.org/

Air Quality Awareness

Awareness drives emissions standards around the world

April 1, 2018: http://aqicn.org/city/uae/al-ain/islamic-institute/

“The Age of Gas” – The Rise of Unconventional Gas

Drives innovation for fuel flexibility

Source: US Energy Information Administration

U.S. Total Natural Gas Proved Reserves (2007-2016)

Increasing Share of Shale Gas

Trends: Growth of Biofuels and Fischer–Tropsch Fuels

Drives innovation for fuel flexibility Source: BP statistical Source of World Energy 2015

~0.5% of current global fuel usage

Trend ImplicationDemand for lower cost of ownership - advanced engines with lower operating (fuel) cost (and lower CO2)

Emissions Regulations (NOx, PM, etc) - has driven 25+ years of combustion technology

Paris climate agreement (CO2) - Government incentives and target toward fuel displacement & more efficiency

Design Implications of Trends

Gas Turbine – Brayton Cycle Primer

Source: Wikipedia

Source: Wikipedia

Drivers of Higher Efficiency

↑ Temperature

↑ Pressure Ratio

↑ Component Efficiencies

Demand for More Efficient Engines

Ideal Brayton Cycle

16 /Source: General Electric GER-4194

2010 2015 2020

“H” (steam)

Cycle Efficiency Advances: Gas Turbines w/ Bottoming Cycle

“HA”

World records

62.2% (50 Hz)

63.08% (60 Hz)

Inlet

• Broader range of T3, P3

Outlet

• Higher Turbine Inlet

Temperature

Consequences of Advanced Cycles

18 /

Combustion and Emissions

from Fuel from Air

Re

ac

tan

ts Fuel Air

No

rma

l

Pro

du

cts

CO2 Water Nitrogen Excess Oxygen

Un

inte

nd

ed

Pro

du

cts

UnburnedHydrocarbon

CarbonMonoxide

Oxides of NitrogenNOx

Soot(Particulate)

To

tal P

rod

uc

ts

Normal and unintended products of combustion

Source: Roy Primus, GE

Combustion and EmissionsGas Turbine exhaust emissions burning conventional fuels.

Source: General Electric GER-4211

Ground-based Emissions Requirements – World Bank

Local emissions regulations often more stringent (eg California)Source: World Bank

Aviation NOx Emissions Requirements

Evolution of Landing and Take-Off (LTO) Cycle Engine NOx Emissions

ICA

O N

Ox

sta

nd

ard

s (g

/kN

)

Source: ICAO https://www.icao.int presentation by Dr. Neil DicksonICAO Air Transport Bureau

Paris Climate Accord & Aviation CO2 Emissions

• March 2017: ICAO Council adopts new CO2 emissions standard for aircraft

• Applies to new aircraft type designs from 2020, and aircraft already in-production as of 2023.

• Aircraft in-production aircraft which by 2028 don’t comply Source:https://www.icao.int/

Meetings/EGAP/Presentations

Mix of Fuel Types in the Future

Source: BP 2017

• Rise of cost - effective Renewables: - leading to market uncertainty for combustion devices in energy markets- market opportunity for biofuels

• “Age of Gas”: reduced coal use, and liquid fuels

Biofuels fuels for propulsion … promisingSuitable fuels must …

• Result in less carbon

• Be delivered in quantity

• Be cost effective

• Compatible with food production

Timeline of Aviation alternative fuels

Algae … a potential source?

Source: ICAO

25 /

Fuel Effects on Combustion System Performance

Atomization

Reaction

Evaporation

LBO/

Ignition

Liner

Temperatures

Exit

Temperature

Profiles

Smoke/

Particulates

Gaseous

Emissions

Nozzle

CokingSmoke

Point

Viscosity

Aromatics

Vapor

Pressure

Distillation

Profile

Density

Freezing

Point

Heat of

Combustion

Processes

Particles

Surface

Tension

Atomization

Reaction

Evaporation

LBO/

Ignition

Liner

Temperatures

Exit

Temperature

Profiles

Smoke/

Particulates

Gaseous

Emissions

Nozzle

CokingSmoke

Point

Viscosity

Aromatics

Vapor

Pressure

Distillation

Profile

Density

Freezing

Point

Heat of

Combustion

Processes

Particles

Surface

Tension

PerformanceFuel Properties

CombustionDynamics

Many Linkages Between Fuel Properties and Combustion Performance

From OEM presentation to National Jet Fuels Combustion Program

Alternative gaseous fuels•Fuels characterized by the heating value and constituents:

– Modified Wobbe index < 40 or > 60

– Low to med BTU fuels, LHV < ~800 BTU/SCF

– High BTU fuels, LHV > ~1200 BTU/SCF

• High H2 fuels > 5% by volume

• High CO, CO2, N2, C2+

Refinery, Process

Off Gases

• High H2, CO2, CO

LNG, Associated

Flare Gas

• High C2+

LNG

• High N2, CO2

COG, Low BTU

Syngas

• High H2, CO2, CO

Modified Wobbe Index=

LHV/ (MWgas/28.96 * T)^0.5

Combustion Systems

GT Combustor Architectures• Ground-based Gas Turbines• Aircraft Engines

Source: General Electric GER-4194

Ground-based Gas Turbines

• Silo Combustor

• Can-annular Combustor

• Annular Combustor

GE 7FB Gas Turbine

Combustion System Architectures

Diffusion Can Combustor• Rich burning• up to 300 ppm NOx•Highly fuel flexible•No staging

GT Combustor Technology Evolution

DLN-1 Combustor• Axially Staged Combustion • 3-25 ppm NOx• E-class Gas Turbines

DLN-2 Combustor• Fully Premixed Combustion• 9-25 ppm NOx• F,H-class Gas Turbines

Inlet Flow Conditioner

Diffusion Swirler

Diffusion Gas Holes

Swirler Vanes

Premix Fuel Passages

Source: General Electric GER-4194

Low Emissions Combustor Flame Structure

• Flame imaging of low emissions combustor

• Multiple fuel nozzles in each combustion chamber

30

Reheat Gas Turbine

Alstom GT24/26 • Annular Combustor• Sequential Combustor

Aircraft Engine Approaches to Reduced Emissions

• More fuel injection points

• More air to combustor dome

• Fuel system complexity (staging)

Single Annular Combustor (SAC)• Rich burning• 54% of CAEP/2 NOx (Tech In.)• Proven performance• No staging• 3M+ flight hours (LEC)

CFM56 DAC

GEnx

CFM56 SAC

Aviation Combustion Technology Evolution

Dual Annular Combustor (DAC)• Lean burning• 47% of CAEP/2 NOx• Shorter combustor• Radial & circumferential staging• 3M+ flight hours

Twin Annular Premixing Swirler (TAPS)• Lean burning• 42% of CAEP/6 NOx• Shorter combustor• Staging within the swirler

Balance reduced emissions with operability, durability, cost and weight

Aviation gas turbine combustion

• Flame imaging

• Flame structure changes with fuel staging

Combustion Development

36GE Title or job number

4/4/2018

Gas Turbine Combustor Design Requirements

Fuel Property Interactions

Complex physics and non-linear interactions

• Huge range of time and length scales

• Trade-offs to achieve design balance and meet product requirements

Balanced Design enabled by Analysis and Validation

Gas Turbine Combustion Challenges

Flame must be anchored in the equivalent of 100 mph wind

Chemical reactions must occur in a fraction of a second as air and fuel flow through the combustor. How fast?

3-25 ms

38 /

Combustor key physics

Turbulent subsonic

flow

Swirling turbulent

flow with heat

release

Fuel-air mixing

Emissions

chemistry

Acceleration to

sonic conditions

Radiant energy

transfer

Combustion

Ignition,

Extinction and

Stability Turbulence-

chemisty

interactions

39 /

Emissions: NOx Fundamentals

NOx Formation Mechanisms• Zeldovich Mechanism (air at high T)

• Prompt-NOx (CHx+N2)

• Fuel-Bound Nitrogen (FBN)

Source: General Electric GER-4211

Fenimore Mechanism

40GE Title or job number

4/4/2018

Prompt NOx Discovery - Charlie Fenimore

CH+N2 HCN + N

Role Model Industrial Research Career

• Discovered “Prompt-NOx”, the reaction of N2 with CH radicals

• Used porous plug burner to create 1D, well-characterized, premixed flames.

• Made it possible to understand at devise pratical approaches to reduction of smoke and other emissions.

Awarded the Combustion Institute Bernard Lewis Gold Medal in 1974 for “brilliant research in the field of combustion, particularly mechanics of elementary reactions.

NOx Control Technologies

Relative Cost Impact

Lean Premixed Combustion is Preferred Solution

Source: EPA 456/F-99-006R

Strategies to Reduce Nox

• Lower Peak Temperature

• Premix Fuel and Air

• Reduce O2 Concentration

• Reduce Residence Time

• Less Time at Temperature

• Cleaner Fuels

• No Fuel-Bound Nitrogen

• Staged Combustion

• Aftertreatment

Combustor Design Approaches to Lower Emissions

Key Constraints

• More fuel injection points

• More air to combustor dome

• Fuel system complexity (staging)

Combustor Operating Window

NOx

CO

Hot Tones

Cold Tones

Acceptable Limits

Op

era

tin

g w

ind

ow

wit

h a

cc

ep

tab

le

em

issi

on

s a

nd

dy

na

mic

s

44 /

Emissions Advances: Gas Turbines

Heavy Duty Gas Turbine

Source: General Electric GER-4194

E-Class: 25 ppm 3 ppm

HA-Class: 25 ppm

F-Class: 25 ppm 5 ppm

Baseline: 100’s of ppm

45 /

Combustor Design & Validation Process

Non-reacting

Simulations

Sub-System

Full Annular Rig

Can Combustor

System

Full Engine

Component

Single Nozzle

Sector Rig

Sub-Component

Non-reacting

Rigs

Reacting

Simulations

0D. 1D

Analysis

46 /

Additive Technology Driving Innovation

• Direct Metal Laser Melting (DMLM)

• Start with a metal powder and form a metal part directly

• Enables fast cycle time from idea to hardware

• Enables novel geometries - part complexity is “free”

Case Study – Fuel Nozzle

Combustion System Technology Drivers

• Fuel Efficiency (Cost, CO2)• Emissions regulations (NOx, PM)• Fuel Type (Resilience)• Durability (Cost, Reliability)• Operability (Flexibility)

Many Drivers and Opportunities to Create New Technology

48 /

Gaps & Opportunities in Combustor Design

Advanced Cycles• Need fundamental combustion data at relevant conditions (>20 bar)• Highly turbulent combustion and super-sonic combustion• Multi-physics design tools (range of time and length scales)

Emissions Regulations• Lean premixed combustion – reaching entitlement• CO2 becoming an “emission”

Fuel Flexibility• Need chemical kinetics for all fuels• Mixed-modes of combustion

Need multi-physics design tools anchored with data

New additive manufacturing enables faster design cycles

49 /

Questions?