Keywords

Combustion, ammonia, hydrogen, flame, thermodynamics, turbomachinery

Abstract

As the world faces global conflict and energy crises, major efforts are underway to find sustainable engineering solutions to reduce industrial dependence on fossil fuels and minimize climate impacts from carbon emissions. Research in the combustible fuel sector is crucial to address economic reliance on cheap carbon-based fuels for increased energy capacity and reduced greenhouse gas emissions. Ammonia (NH₃) offers high energy potential and zero carbon emissions (CO and CO₂) while serving as an effective hydrogen (H₂) carrier in power and transportation applications. Turbine-combustion research on NH₃ and H₂ fuels has been conducted to identify combustion performance parameters for high-pressure, sustainable turbomachinery. Studies on NH₃ and H₂ performance capabilities have revealed sources of thermodynamic instabilities, such as uncontrolled flames or flashback, by assessing fuel laminar burning speed (LBS) with optical data. LBS is a key combustion parameter that informs turbine design engineers about combustion physiochemistry, flashback, and efficiency. State of the art literature shows that H₂ enhances the LBS of NH₃ (φ = 1.0, SL = 5.0 – 21 cm/s) for all equivalence ratios at 1 atm and 298 K. However, H₂ dilution to NH₃ results in excess N₂O and NOx emissions, which are toxic to biological systems. Thus, further efforts are needed to reduce toxic gas emissions and identify thermodynamic engineering controls to maintain stable NH₃-H₂ flames. In this work, NH₃ and H₂ mixtures were ignited at an initial temperature and pressure of 293 – 323 K and 5 – 10 atm to understand their performance properties. The LBS was calculated using a multizone, constant volume combustion model. Experimental results showed that H₂ dilution enhances the LBS of NH₃, and chemical-kinetic sensitivity analyses identified reactions facilitating this effect. Additional flame stabilization studies investigating the Lewis number of experimental mixtures revealed that helium (He) effectively mitigates thermal-diffusion, as shown by Schlieren optical measurements.

Completion Date

2024

Semester

Summer

Committee Chair

Vasu, Subith

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Thermofluids

Format

application/pdf

Identifier

DP0028633

URL

https://purls.library.ucf.edu/go/DP0028633

Language

English

Rights

In copyright

Release Date

August 2025

Length of Campus-only Access

1 year

Access Status

Masters Thesis (Campus-only Access)

Campus Location

Orlando (Main) Campus

Accessibility Status

Meets minimum standards for ETDs/HUTs

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Restricted to the UCF community until August 2025; it will then be open access.

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