Michael J Evans

University of South Australia | UniSA · STEM Unit

Moderate or intense low oxygen dilution (MILD) combustion has been the subject of numerous studies in recent years. An issue remains, however, in the definition of the boundaries of the MILD combustion regime with respect to non-premixed configurations without predefined reference temperatures. A flamelet definition is applied to non-premixed confi...

The moderate or intense low oxygen dilution (MILD) combustion regime offers reductions in pollutant emissions and improvements in efficiency. The implementation of MILD combustion in non-premixed systems, however, still requires a significantly improved understanding of the effects of the oxidant stream composition in both the MILD combustion regim...

Moderate or intense low oxygen dilution (MILD) combustion has been the focus of a range of fundamental experimental and numerical studies. Reasonable agreement between experimental and numerical investigations, however, requires finite-rate chemistry models and, often, ad hoc model adjustment. To remedy this, an adaptive eddy dissipation concept (E...

Gaseous and liquid dual-fuel flames present both a practical approach to emissions reduction and a challenge to current state-of-the-art combustion modelling. This paper uses simultaneously imaged temperature and normalised OH signal fields to investigate flame structure and provide experimental data for model validation across a range of swirl-sta...

There is a wealth of existing experimental data of flames collected using laser diagnostics. The primary objective of this review is to provide context and guidance in interpreting these laser diagnostic data. This educational piece is intended to benefit those new to laser diagnostics or with specialization in other facets of combustion science, s...

Hydrogen-fueled aircraft are a promising innovation for a sustainable future in aviation. While hydrogen aircraft design has been widely studied, research on airport requirements for new infrastructure associated with hydrogen-fueled aircraft and its integration with existing facilities is scarce. This study analyzes the current body of knowledge a...

In flames, turbulence can either limit or enhance combustion efficiency by means of strain and mixing. The interactions between turbulent motions and chemistry are crucial to the behaviour of combustion processes. In particular, it is essential to correctly capture non-equilibrium phenomena such as localised ignition and extinction to faithfully pr...

Carbon dioxide (CO 2), also known as R744, is one of the natural substances, which is an environmentally benign, safe and economical refrigerant used for cooling and heating systems. The transcritical CO 2 heat pump water heater has attracted much attention from researchers in recent years, due to that the CO 2 water heater can contribute to a sign...

New understanding of turbulent ethylene (C2H4) jet flames, issuing into a range of preheated coflowing oxidisers with reduced oxygen (O2) concentrations are reported. These conditions emulate moderate or intense low-oxygen dilution (MILD) combustion. To resolve previously reported non-monotonic trends, comparisons are made for coflow O2 concentrati...

This work investigates the effects of ambient and injection parameters on the ignition and combustion characteristics of hydrogen (H2)-methane (CH4) jet (50% H2 by volume, with the remaining CH4) in simulated direct-injection, compression-ignition conditions. Parameter variations include ambient gas temperature (1060-1200 K), ambient oxygen (O2) co...

This paper studies the combined heating and cooling thermal performance of a CO2 heat pump system considering the subcooling effect. For such a system without cold thermal energy storage (CTES), the gas cooler outlet temperature normally needs to be controlled to match the cooling load required. However, the integration of CTES would enable the sys...

Latent heat thermal energy storage systems can regulate the intermittency of electricity generation in a grid powered by renewable energy sources. Such systems could be used in conjunction with Brayton power generation cycles operating at high temperatures (520 °C–750 °C) delivering higher efficiency. However, a trade-off of higher thermal efficien...

In the context of the Montreal Protocol, CO2 is considered as an appropriate natural refrigerant with an Ozone Depletion Potential (ODP) of zero and a Global Warming Potential (GWP) of one. A CO2 heat pump water heater (HPWH) can provide hot water with a relatively high COP and consume significantly less energy than all electric or gas water heater...

Supercritical CO2 has been proposed as a heat transfer fluid for Brayton cycles to achieve a high effectiveness in power generation from concentrated solar power plants. A printed circuit heat exchanger (PCHE) has been considered as an alternative design for a sodium to supercritical CO2 heat exchanger operating at high pressure and temperature (22...

Combustion in hot and low oxygen environments, such as those encountered in practical devices including inter-turbine burners and sequential gas turbines, is not yet fully understood at a fundamental level, particularly in terms of the effects of pressure. To meet this gap in understanding, a confined-and-pressurised jet-in-hot-coflow (CP-JHC) comb...

The structure and stabilisation mechanisms of ethanol and n-heptane spray flames are investigated in this study. The burner configuration involves a dilute spray of dispersed droplets which is produced and transported via a carrier gas stream of air to the reaction zone, where the flames are stabilised by a hot coflow of combustion products. A rang...

The study reveals the effect of interstage pressure with the consideration of gas cooler outlet temperature on the cooling performance of an operating CO 2 heat pump system currently in use at a dairy plant. Based on the numerical model and CO 2 properties, it was found that the maximum mass fraction of liquid allocated for cooling can be achieved...

The configuration of a recently installed CO2 heat pump system with a cooling capacity of 33.5 kW and heating capacity of 35.8 kW used on a dairy farm is presented. This system has been studied in order to determine the optimal performance when used for combined water heating and refrigeration. Furthermore, the effect of the interstage pressure on...

Carbon dioxide (CO2) is a natural substance and an environmentally benign, safe and economical refrigerant that can be used for cooling and heating systems. Unlike a traditional reversible heat pump system that only works either in heating or cooling, the air-to-air transcritical CO2 heat pump system reported in this paper is capable of providing s...

The structural integrity of a lab-scale shell and tube latent heat thermal energy storage under transient conditions was investigated. The system was designed to use sodium at 750 °C as a heat transfer fluid with a high temperature phase change material, melting at 705.8 °C, as the heat storage medium. Stainless steel 347H (SS347H) was used as the...

Report is accessible on https://www.racefor2030.com.au/publications/ This report has been prepared by the authors at the request of the Reliable Affordable Clean Energy for 2030 Cooperative Research Centre (RACE for 2030 CRC). In Australia, industry consumes nearly half of the total end use energy, out of which, 37% is used in process heat, repres...

The combustion of liquid fuels in a hot and low-oxygen environment is commonly encountered in a range of practical situations. To enable investigation of the fundamental combustion processes relating to such applications, liquid fuels were injected into the reaction zone as dilute sprays in this study. Droplets of ethanol, n-heptane, and n-heptane/...

A turbulent n-heptane jet flame in a jet-in-hot-coflow burner is numerically and experimentally investigated, revealing distinct features of this fuel in a jet-in-hot-coflow burner. The RANS k-ε turbulence model is adopted in combination with a dynamic partially-stirred reactor (PaSR) combustion model. The simulation results are used to support new...

Oscillating jet flames in a coflow mimic certain features of turbulent flows in a simplified and controllable way. Our study aims to identify the potential of the HMOM soot model, which is validated in steady laboratory flames to be applied in practical, mostly turbulent flames. The model is found to accurately predict all the measurement parameter...

Flames in hot, low oxygen environments exist in a variety of practical applications. These conditions result in significant mixing between fuel and combustion products, such as water vapour, or diluents included for emissions control. The chemical and physical effects of water vapour as a diluent are investigated in a series of ethylene flames in a...

Adapting hydrogen as a carbon-free fuel for industrial applications requires new, innovative approaches, especially when radiant heat transfer is required. One possible option is to dope hydrogen with bio-oils, containing aromatics that help produce highly sooting flames. This study investigates the potential doping effects of toluene on a hydrogen...

The role that combustion plays in energy systems remains crucial in supplying the world’s ever-increasing power demands [...]

http://anz-combustioninstitute.org/ACS2019/

Rotating detonation engines are a novel device for generating thrust from combustion, in a highly efficient, yet mechanically simple form. This chapter presents a detailed literature review of rotating detonation engines. Particular focus is placed on the theoretical aspects and the fundamental operating principles of these engines. The review cove...

A numerical study of the fluid-chemical interactions in a steady and time-varying laminar non-premixed jet flame was conducted to advance understanding of the complex interplay between the flame chemistry, fluid dynamics and soot evolution. Modelling of the steady flame is performed with two alternative reduced mechanisms and compared with the sign...

The scenario of fuel injected into hot surrounds is found in a range of practical combustion applications. These flame conditions have been emulated using a jet-in-hot-coflow-burner using prevaporised n-heptane and mixtures of n-heptane and toluene, relevant to gasoline and diesel fuel surrogates. This paper reports measurements of six lifted, turb...

Exhaust hoods are commonly used to capture all emissions from stationary combustion systems that are open to the environment, such as residential heaters or stoves. For experimental purposes, emissions are sampled at one, or more, discrete locations downstream in the exhaust duct. Point-wise measurements in the duct are often taken with the assumpt...

This study compares the flame structure of ethanol and dimethyl ether (DME) in a hot and diluted ox- idiser experimentally and computationally. Experiments were conducted on a Jet in Hot Coflow (JHC) burner, with the fuel jet issuing into a 1250-K coflow at three oxygen levels. Planar measurements using OH-LIF, CH2O-LIF, and Rayleigh scattering ima...

Turbulent flames in the moderate or intense low oxygen dilution (MILD) combustion regime have previously exhibited less susceptibility to lift-off than conventional autoignitive flames in a jet-in-hot-coflow (JHC) burner. This has been demonstrated through laser-based diagnostics and examination of CH* chemiluminescence. New experimental observatio...

Distinctive behaviour of turbulent n-heptane jet flames is revealed by conventional photography and laser-induced fluorescence of the hydroxyl radical (OH-LIF) performed in a Jet in Hot Coflow (JHC) burner. Prevaporised n -heptane, carried by air, issues into a hot vitiated coflow at two temperatures (1250 K and 1315 K) with three coflow oxygen lev...

Experiments of autoignitive jet flames in a hot and vitiated coflow have previously shown various flame behaviours, spanning lifted flames to MILD (moderate or intense low oxygen dilution) combustion. To better understand the behaviour of flames in this configuration, regime diagrams and ignition delay results are presented from well-stirred reacto...

The present paper is focused on prevaporised ethanol flames in the transition from conventional combustion to the MILD combustion regime. Photographs and imaging of OH* chemiluminescence reveal a distinctive flame structure when ethanol carried by air burns in a 3% O2 coflow (typical of MILD combustion), differing from that at higher oxygen levels....

In the continual effort to reduce emissions and improve efficiency, moderate or intense low-oxygen dilution combustion has been suggested for aeroengine applications. This new application of moderate or intense low-oxygen dilution combustion requires further insight in applying the knowledge from conventional analyses of well-mixed systems to non-p...

Investigations into efficient, low NOx combustion have highlighted moderate or intense low oxygen dilution (MILD) combustion as a potential candidate for future technologies. Experimental research into MILD combustion has been previously undertaken in jet-in-hot-coflow (JHC) style burners, where the combustion environment is set by a controlled cof...

Moderate or intense low oxygen dilution (MILD) combustion has been the subject of numerous studies in recent years. The boundaries of the MILD regime have, however, only been defined with respect to premixed configurations. These previous definitions have been based on the initial and final states of a perfectly-stirred reactor relative to the fuel...

Combustion in next-generation aero-engines may occur in conditions in, or approaching, moderate or intense low oxygen dilution (MILD) combustion. Under these conditions, fresh fuel is injected into a hot, low oxygen environment. Autoignition delays for ethylene, with detailed chemical kinetics, in three different oxidants are systematically analyse...

Moderate or Intense Low oxygen Dilution (MILD) combustion has been established as a combustion regime with improved thermal efficiency and decreased pollutant emissions, including NOx and soot. MILD combustion has been the subject of numerous experimental studies, and presents a challenge for computational modelling due to the strong turbulence–chemi...

Moderate or Intense Low oxygen Dilution (MILD) combustion is a particular combustion regime which offers improved thermal efficiency and a reduction of nitrogen oxide (NOx) pollutants and soot. In this paper computational fluid dynamics (CFD) is employed to model turbulent jet flames issuing into a hot and diluted coflow stream, with a view to deve...

Moderate or Intense Low oxygen Dilution (MILD) combustion offers improved thermal efficiency and a reduction of NOx pollutants and soot emissions compared to conventional combustion. Previously MILD combustion in the Jet in Hot Coflow (JHC) burner, using methane-based fuels, has been simulated with the Eddy Dissipation Concept (EDC) turbulence-chem...