a clean fuel: “ultra-low nox hydrogen micromix combustion systems for lh2 … · 2020-04-20 ·...

This project has received funding from the EU Horizon 2020 research

and innovation programme under GA n° 769241

A Clean Fuel: “Ultra-low NOx Hydrogen Micromix Combustion Systems for LH2-fuelled aircraft”

9th EASN Conference on Innovation in Aviation and Space3rd – 6th September 2019, Athens, Greece

Dr. Xiaoxiao Sun - ENABLEH2 Micromix Work Package leader

Research Fellow in Hydrogen Micromix Combustion,

Propulsion Engineering Centre, Cranfield University

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GA no. 769241

• Research gaps

• ENABLEH2 Micromix work scope

• Micromix injector design and down-selection

• Test cases and facility

• Lessons learnt from Numerical analysis up to date

9th EASN Conference on Innovation in Aviation and Space

3rd – 6th September 2019, Athens, Greece2

Contents

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GA no. 769241

• Injector and combustion system design and manufacture

➢Trade-offs between conflicting objectives

➢Manufacturing techniques

• Modelling

➢Predictive capability of SOA CFD software for hydrogen micromix combustion (and emissions) modelling

➢ Identify specific challenges

• Research scope (numerical and experimental)

➢ Injector array (Phase 1)

➢Full scale annular combustor segment (at combustor inlet conditions representative of cruise) (Phase 2)

➢Altitude relight (Phase 3)

• Thermoacoustic Assessments

➢ Implications of less dilution air available for damping

➢How lean can we go?

➢Can fuel scheduling alleviate TA problems?



Hydrogen Micromix Combustion:Research Gaps and Contribution of ENABLEH2

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GA no. 7692419th EASN Conference on Innovation in Aviation and Space


Phase 1 Research Overall Methodology

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Stage 1: Preliminary Injector Selection

Selection of injector geometries and spacing based on performance assessments using CFD results. Further simulations

for a range of inlet conditions on selected geometries

Stage 2: Flame Characteristics Experiments

Experimental campaign to generate data of flow and flame characteristics and dynamics over a wide range of inlet conditions

Stage 4: Rigorous Injector Design Space Exploration

Further design space exploration using calibrated STARCCM+ CFD models and down selection of the final preferred injector

geometry and spacing

Stage 5: Final Experimental Assessment

Injector array tests with final selected geometry and spacing to assess performance characteristics and further evaluate

STARCCM+ prediction capability

Numerical Analysis Experimental Analysis

Stage 3: CFD Models Evaluation, Calibration & Validation

Compare CFD model prediction capabilities among ANSYS, STARCCM+ and AVBP Code. Evaluate, calibrate and validate

STARCCM+ CFD models

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Micromix injector design

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• Hydrogen Offset Distance (0.5mm – 5mm)

• Mixing Distance (0.5mm –2.5mm)

• Hydrogen Inlet Diameter (0.3mm)

• Air Feed Dimensions

➢ Air Feed Height (1mm – 2.4mm)

➢ Air Feed Diameter (1mm -2.5mm)

➢ Aspect Ratio (1- 2)

Momentum Flux

Ratio ~ 0.85 - 40

H2 Injection Diameter

Air InletH2 Inlet

H2/Air Offset Mixing Distance

d

h

Aspect Ratio = h/d

Image adapted from [1]

25mm

42mm30mm

5mm

10mm

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Anticipated Micromix flow structure

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• Two symmetric inner recirculation zones obtained for

two hydrogen jets sharing same feeding arm

• Similar size of recirculation zones from two separate

feeding arms

• Corner recirculation limited to the recessed part only

• Relatively stabilised flow

• Acceptable temperature near window/wall

Contour of OH mass fraction by LES (L: instantaneous, M: averaged) and RANS (R)

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Selected injectors for rig test

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Current analysis focus on the effect of

• Momentum flux ratio (Air gate and hydrogenfeed dimensions)

• Air gate shape

• H2/air mixing distance

• H2/air offset distance

D (Air)

mm

Air Gate

Height (mm)

Aspect

Ratio

Momentu

m Flux

Ratio

Hydrogen

Offset Distance

(mm)

Hydrogen

Mixing Distance

(mm)

Baseline 1.50 2.25 1.50 2.24 1.50 1.50

Design 14 1.18 1.77 1.50 0.85 0.84 1.42

Design 23 2.16 2.85 1.33 7.32 4.75 0.86

Design 33 2.50 3.25 1.30 17.31 2.00 2.00

• Highest Momentum Flux Ratio (Penetration of H2 inthe air stream)

• Significant flame-flame interaction (attachment)between two H2 injections with the same feed arm

• No flame-flame interaction with the same feed arm

• Increased mixing distance

• Increased H2/air offset distance

Injector Design Selection Criteria

Example of flame patterns at with low (L) and high (R) hydrogen penetration

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Proposed Test Cases

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• Compressor

➢ In-house Ingersoll Rand (Max P ~ 15bar)

• Heater options

➢ Immersion heater (Max T ~ 650K @ 110g/s)

➢ Pebble bed heater (Max T ~ 800K @ ~3kg/s)

• Cases to investigate effect of

➢ Air Temperature (300-600K)

➢ Pressure (1-15bar)

➢ Equivalence ratio (LBO-0.5)

➢ Injector designs

Temperature contour at varying air inlet conditions

15bar

10bar

1bar

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Pebble Bed Facility

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• The facility is able to provide high mass flow of non-vitiated air at high pressures (fed by compressor)

and high temperatures to reproduce representative GT combustor inlet conditions

• By varying the combination of pebble bed and dilution air flow rate, a wide range of test section inlet

mass flow and temperature can be produced

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Proposed Phase 1 Rig design

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Position of ignitor

Optical windows

Air Chamber Upstream pressure

transducers

Downstream pressure

transducersAir channels

Hydrogen

channelsHydrogen feeds

Air Flow

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Heat transfer and influence on emissions

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Air H2

Solid

Material

15bar

600K

Boundary Parameter Value

Air Inlet Temperature (K) 600

Hydrogen Inlet Temperature (K) 300

Combustor Inlet Pressure (bar) 15

• Conjugate Heat Transfer between

hydrogen injector plate and flow

• Material: Stainless Steel 316L

Temperature

Mass fraction NO

• High wall temperature at low

momentum flux ratio

• NOx dependent on both momentum

flux ratio than global equivalence ratio

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Influence of rig configurations

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Altered injector

symmetry

3 rows of fuel arm

(baseline: 4 rows)

Reduced number of

burning injectors

N=24

(baseline: 32)

Increased test

section size

D=48mm

(baseline: 42mm)

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GA no. 769241

• Numerical

Evaluate, validate and calibrate hydrogen combustion models by further investigating specific peculiar

characteristics of hydrogen/air mixing and combustion, e.g.

➢Hydrogen molecular diffusivity

➢Hydrogen reaction rate and flamelet thickness

➢NOx prediction capability

• Experimental

➢Manufacturing of sub-mm injector orifice

➢Rig capability for high T and P

➢ Full annular segment and altitude relight tests

• Delivery of a lower order NOx emissions model for micromix combustion and its

environmental importance on meeting and exceeding FP2050 goal



Conclusions and next steps

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This project has received funding from the EU Horizon 2020 research and innovation programme under GA n° 769241

Thank [email protected]

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The ENABLEH2 project is receiving funding from the

European Union’s Horizon 2020 research and

innovation programme under grant agreement No769241

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3rd – 6th September 2019, Athens, Greece1520.04.2020

Hydrogen Micromix CombustionWhy Hydrogen?

No CO/UHC/Soot

Wider stability limits

Leaner combustion

Lower flame

temperature

Lower

thermal NOx

Higher reaction rate

Lower residence time

Higher diffusivity

Faster mixing

Shorter

combustor

No Carbon

Less Luminous

Radiation

Higher burning velocity

Better liner

durability

Ziemann J, Mayr A, Anagnostou A, Suttrop F, Lowe

M, Bagheri SA, et al. Potential use of hydrogen in air

propulsion. EQHHPP, Phase III.0-3. Final report,

submitted to European Union (contract no. 5077-92-

11 EL ISPD).

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Hydrogen Micromix CombustionWhy Micromix?

• Mixing length scale minimised while mixing intensity maximised

• Diffusion flame - reduces risk of flashback

• More flexibility for customised fuel scheduling:

▪ Tailor outlet temperature distribution (without dilution zone)

▪ Control of thermoacoustic instabilities

Funke, Harald H-W., et al. "Development and Testing of a Low NOx Micromix

Combustion Chamber for an Industrial Gas Turbine."

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Methodology and Work Scope for WP3

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Task breakdown

• Task 3.1. Definition of measurement requirements/techniques, selection of injector additive

manufacturing technique, down selection of preferred injector designs

• Task 3.2. Single injector and injector array experimental and analytical studies

• Task 3.3. Multi-injector, full-scale, annular combustor segment experimental and analytical studies

• Task 3.4. Sub-atmospheric, altitude relight experimental, numerical analyses

• Task 3.5. High-fidelity LES CFD modelling of the H2 micromix injector annular combustor segment

and delivery of a lower order NOx emissions prediction model

• Task 3.6. Thermoacoustic risk assessment of micromix combustion concepts using experimental

and analytically derived flame properties with a lower order thermoacoustic analysis code

(OSCILOS)

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CFD models:Selection of hydrogen reaction mechanisms

Mechanism

IDRef

Species

Number

Reactio

n

Number

RD2010 [x] 9 25

GRI-Mech 3.0 [x] 53 325

DRM 1.2 [x] 22 104

Numerical Analysis• RANS Simulations

• k-ω SST turbulence model

• FGM for combustion kinetics modelling

• Thermal NOx post processed using

extended Zeldovich mechanism of

frozen flow field

Results• RD2010 mechanism has been down selected

based on the optimum number of species and

the reaction steps finite rate EDC simulations

• GRI-Mech 3.0 and DRM 1.2 have been highly

optimised for natural gas combustion

• The reason for these uncertainties are highly

debatable. Experimental validations to be

carried out to further evaluate these

uncertainties

Boundary Parameter Value

Air Inlet Temperature (K) 860

Hydrogen Inlet Temperature (K) 300

Combustor Inlet Pressure (bar) 20.5

Phase 1 Rig Schematic

Main measurement• Flame visulisation• Emissions• Pressure loss

a clean fuel: “ultra-low nox hydrogen micromix combustion systems for lh2 … · 2020-04-20 ·...

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