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Introduction
Midhat Talibi's research focus is on experimental combustion and alternative energy vectors (hydrogen, ammonia, e-fuels) across a range of energy systems. His PhD on hydrogen-diesel combustion was followed by post-doctoral research on novel fuels for ultra-low emission ICEs and hydrogen-enriched fuels for low emission GTs. He currently holds the prestigious UKRI Future Leaders Fellowship, and is working with industry to develop hydrogen technologies for powerand aero-propulsion applications.
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Publications
Publications (52)
The demand to reduce carbon emissions has prompted research into alternative fuels that can replace conventional fuels like diesel in industrial gas turbines. Among different potential biofuels and e-fuels, methanol emerges as a sustainable and high-performance alternative to diesel for gas turbine applications. It is well established that the fuel...
The transition to a decarbonised energy future relies on identifying the most suitable alternative fuels that can meet the needs of various energy sectors. While both ammonia and hydrogen are zero-carbon energy vectors, their physical properties and burning characteristics sit on either side of that of natural gas. Hence, mixtures of ammonia and hy...
Hydrogen is a promising zero-carbon fuel for decarbonised energy and transportation sectors. While carbon emission is not a concern for hydrogen combustion, its higher adiabatic flame temperature poses challenges of mitigating thermal NOx emissions. The wide flammability limits of hydrogen allow a fuel-lean operation, which can reduce NOx emissions...
In line with the global drive to decarbonise energy systems, there is an urgent need to develop new dry low-NOx (DLN type) combustion concepts to enable efficient utilisation of alternative fuels, such as hydrogen. New combustor configurations require a detailed study of flame behaviour, including stabilisation, structure and dynamics, as well as o...
The transition to a decarbonised energy future relies on identifying the most suitable alternative fuels that can meet the needs of various energy sectors. While both ammonia and hydrogen are zero-carbon energy vectors, their physical properties and burning characteristics sit on either side of that of natural gas. Hence, mixtures of ammonia and hy...
In this study, the thermoacoustic instabilities of partially premixed hydrogen flames in a lean direct injection (LDI) multi-cluster combustor are characterised using dynamical systems theory. The combustor is operated at a range of bulk velocities (30 - 90 m/s) and equivalence ratios(0.2-0.6), and time-resolved pressure oscillations and integrated...
The demand to reduce carbon emissions has prompted research into alternative fuels that can replace conventional fuels like diesel in industrial gas turbines. Among different potential biofuels and e-fuels, methanol emerges as a sustainable and high-performance alternative to diesel for gas turbine applications. It is well established that the fuel...
Rapidly decreasing urban air quality and the resultant health impacts are of increasing global concern, with an estimated 7 million premature deaths worldwide attributable to airborne pollutants. Many European and North American cities are increasingly implementing emissions monitoring and control schemes, however, those in the Middle East, Africa,...
Hydrogen has immense potential as a future energy vector for power and propulsion applications. However there are several challenges, including flame stability, flashback and emissions, that impede its widespread use in modern energy systems. Hydrogen systems are required to be operated at fuel-lean conditions to avoid high NOx emissions and flashb...
Thermoacoustic oscillations continue to be a major problem affecting combustor performance and operation in gas turbines. Acoustic forcing is often employed to simulate dynamical states in a combustor, however reproducing intermittent-like behaviour can be difficult. This paper, for the first time, reports a forced intermittent behaviour in a labor...
Hydrogen continues to show significant promise as a zero-carbon energy carrier in the pursuit of global decarbonisation targets. Hydrogen has wide flammability limits which means it can operate at considerably leaner conditions for reduced NOx emissions. However, fuel-lean operation makes these systems more susceptible to thermoacoustic instabiliti...
Can and can-annular (can-type) combustors are widely employed in stationary gas turbines. While majority of combustion instability research so far has focused on single can combustors, studying combustion dynamics in multi-can configurations holds more practical relevance. In can-type combustors, the annular gap between the transition ducts and fir...
Predicting the response of swirling flames subjected to acoustic perturbations poses significant challenges due to the complex nature of the flow. In this work, the effect of swirl number on the Flame Describing Function (FDF) is explored through a computational study of four bluff-body stabilised premixed flames with swirl numbers ranging between...
The development of gas turbines using 100% hydrogen as fuel is an important step towards the development of new energy and propulsion technologies using zero carbon fuels. This chapter reviews some elements of combustion science and engineering that can help with these developments. Stable and low-NOx hydrogen combustors face significant challenges...
Ammonia/hydrogen fuel blends have recently emerged as a promising solution to the de-carbonization of the energy and transport sectors. However, concerns over performance and, more importantly, NOx emissions have impeded their progress so far. Before effective NOx mitigation strategies can be developed, the fundamental chemical mechanisms involved...
Renewable alternatives to fossil diesel (FD) including fatty acid methyl ester (FAME) biodiesel have become more prevalent. However, toxicity of exhaust material from their combustion, relative to the fuels they are displacing has not been fully characterised. This study was carried out to examine particle toxicity within the lung epithelium and th...
An effective Lagrangian Planar Interferometric Tracking (PIT) processor is proposed to track the size and path of multiple droplets, with spray droplet diameters (20–150 µm) and volumetric concentrations ( $$\approx$$ ≈ 300 drops/cm $$^3$$ 3 ) consistent with industrial applications, produced by an ultrasonic atomiser in evaporating conditions. A t...
The utilisation of hydrogen with conventional hydrocarbons offers an excellent opportunity to decarbonise current energy systems without significant hardware upgrades. However, this presents fresh scientific challenges, one of which is the difficulty in effective control of pollutant soot emissions due to complex reaction kinetics of hydrogen enric...
The recirculation zone created through vortex breakdown mechanisms in swirling flows plays a vital role for aerodynamic stabilization of turbulent flames in practical combustion systems. This zone interacts with the central recirculation zone (CRZ) of an upstream bluff body and this leads to a complex flow behavior that depends on the blockage rati...
Biofuels may reduce road transport carbon intensity; however, it is uncertain whether displacing fossil diesel would alter the engine-derived particulate toxicity. The primary objective of this work was to determine whether there is a fuel effect on the comparative in vitro toxicity of biodiesel exhaust particulates relative to those from fossil di...
Pyrolysis provides a route for the conversion of lignocellulosic biomass into solid, liquid and gaseous energy vectors or platform chemicals. Polycyclic aromatic hydrocarbons (PAHs) generated in the vapour phase of the biomass pyrolytic reaction may condense to form tars, which are difficult to further upgrade and cause process inefficiency. Contro...
Advanced combustion strategies for gas turbine applications, such as lean burn operation, have been shown to be effective in reducing NOx emissions and increasing fuel efficiency. However, lean burn systems are susceptible to thermo-acoustic instabilities which can lead to deterioration in engine performance. This paper will focus on one of the com...
Hydrogen is receiving increasing attention as a versatile energy vector to help accelerate the transition to a decarbonised energy future. Gas turbines will continue to play a critical role in providing grid stability and resilience in future low-carbon power systems; however, it is recognised that this role is contingent upon achieving increased t...
Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic pollutants emitted by diesel engines, both in the gas phase and adsorbed onto the surface of particulate matter (PM). There remains limited understanding of the complex and dynamic competing mechanisms of PAH formation, growth and oxidation in the gas phase, and their adsorption o...
An investigation into the exhaust emissions of carcinogenic polycyclic aromatic hydrocarbons (PAHs) from a diesel engine was reported. The study is reinforced by the experimental results obtained from a tube reactor aimed at examining the PAH formation processes from these fuels. The paper cantered on the 16 priority PAHs suggested by the United St...
This paper reports an experimental investigation into the effects of fuel composition on the exhaust emission of toxic polycyclic aromatic hydrocarbons (PAHs) from a diesel engine, operated at both constant fuel injection and constant fuel ignition modes. The paper quantifies the US EPA (United State Environmental Protection Agency) 16 priority PAH...
Increasing demand for energy and the need for diversification of fuels used in gas turbine power generation is continuing to drive forward the development of fuel-flexible combustion systems, with particular focus on biomass derived sustainable fuels. The technical challenges arising from burning sustainable fuels are largely associated with the ch...
To reduce reliance on fossil fuels there has been a global push to minimise fuel consumption, and incorporate the use of bio-derived fuels. In practical combustion systems that use liquid fuels, observing the spray behaviour of these biofuels is key in understanding fuel performance; in particular, droplet size distribution is known to have a stron...
Liquid fuel spray characterisation is essential for understanding the mechanisms underlying fuel energy release and pollutant formation. Careful selection of operating conditions can promote flow instabilities in the fuel spray which can enhance atomisation and fuel mixing, thereby resulting in more efficient combustion. However, the inherent insta...
While lean combustion in gas turbines is known to reduce NOx, it makes combustors more prone to thermo-acoustic instabilities, which can lead to deterioration in engine performance. The work presented in this study investigates the effectiveness of secondary injection of hydrogen to imperfectly premixed methane and ethylene flames in reducing heat...
Polycyclic aromatic hydrocarbons (PAHs) are the carcinogenic components of soot. Detailed understanding of PAH formation characteristics is required for development of effective strategies to curtail PAH formation and reduce soot in combustion devices. This study presents an experimental methodology to analyse PAH formation characteristics of a non...
Concerns as to the adverse effects of diesel engine exhaust on urban air quality have resulted in increasingly stringent emissions legislation, with the prospect of many major global cities potentially banning diesel vehicles. Emissions of nitrogen oxides (NOx) and particulate matter (PM) are linked to increases in premature mortality, and the simu...
The co-combustion of diesel fuel with H2 presents a promising route to reduce the adverse effects of diesel engine exhaust pollutants on the environment and human health. This paper presents the results of H2-diesel co-combustion experiments carried out on two different research facilities, a light duty and a heavy duty diesel engine. For both engi...
Lignocellulosic materials have been identified as potential carbon–neutral sources of sustainable power production. Catalytic conversion of lignocellulosic biomass results in liquid fuels with a variety of aromatic molecules. This paper investigates the combustion characteristics and exhaust emissions of a series of alkylbenzenes, of varying number...
Sustainable future fuels are likely to be produced by a wide range of processes, and there exists the opportunity to engineer these fuels so that they burn more efficiently and produce fewer harmful emissions. Such potential is especially important within the context of reducing the emissions of both greenhouse gases (GHG) and toxic pollutants that...
The conversion of lignocellulosic biomass to liquid fuels presents an alternative to the current production of renewable fuels for IC engines from food crops. However, realising the potential for reductions in net CO2 emissions through the utilisation of, for example, waste biomass for sustainable fuel production requires that energy and resource i...
Future fuels for compression ignition engines will be required both to reduce the anthropogenic carbon dioxide emissions from fossil sources and to contribute to the reductions in the exhaust levels of pollutants, such as nitrogen oxides and particulate matter. Via various processes of biological, chemical and physical conversion, feedstocks such a...
This paper presents a study undertaken on a naturally aspirated, direct injection diesel engine investigating the combustion and emission characteristics of CH4-CO2 and CH4-CO2-H2 mixtures. These aspirated gas mixtures were pilot-ignited by diesel fuel, while the engine load was varied between 0 and 7 bar IMEP by only adjusting the flow rate of the...
This paper presents a H2-diesel fuel co-combustion study undertaken on a supercharged, direct injection, diesel engine investigating the combustion characteristics and emissions production at a range of engine loads (IMEP), EGR levels and intake air boosting conditions. The utilisation of EGR and intake air boost with H2-diesel fuel co-combustion a...
The paper presents an experimental investigation of combusting methane-hydrogen mixtures, pilot-ignited by diesel fuel, on a naturally aspirated, direct injection compression ignition engine. The tests were performed with two diesel fuel flow rates for pilot-ignition, and the engine was supplied with different quantities of methane-hydrogen mixture...
Development of new fuels and engine combustion strategies for future ultra-low emission engines requires a greater level of insight into the process of emissions formation than is afforded by the approach of engine exhaust measurement. The paper describes the development of an in-cylinder gas sampling system consisting of a fast-acting, percussion-...
The development of novel strategies for improved efficiency and ‘cleaner’ emissions from internal combustion engines requires new insights into the processes of energy release and in-cylinder species formation from future sustainable fuels. This work presents an experimental investigation carried out on a compression-ignition engine to study the co...
The paper presents an experimental investigation of hydrogen-diesel fuel co-combustion carried out on a naturally aspirated, direct injection diesel engine. The engine was supplied with a range of hydrogen-diesel fuel mixture proportions to study the effect of hydrogen addition (aspirated with the intake air) on combustion and exhaust emissions. Th...
In developing future fuels there is an opportunity to make use of advances in many fields of science and engineering to ensure that such fuels are sustainable in both production and utilization. One such advance is the use of synthetic biology to re-engineer photosynthetic micro-organisms such that they are able to produce novel hydrocarbons direct...
