This research work aims to improve our knowledge of fire. We use a range of experimental and theoretical methods to build our understanding.

Contact person: Professor Ivar Ståle Ertesvåg

Gas turbine engines are incredibly widely used, both for aircraft propulsion and for land-based power generation. The high power to weight ratio of these engines, together with the high energy density of their fuel makes them difficult to replace for long haul aircraft flight. Similarly, the ability to rapidly scale their power output makes land-based gas turbines an ideal partner to intermittent renewable energy sources in terms of power generation.

However, the climate crisis requires that society transitions to sustainable energy sources, which result in zero net emission of carbon dioxide (CO2), while also controlling the emission of other harmful pollutants such as nitrous oxides (NOx). Our research focusses on the technical challenges of switching to zero net carbon fuels, such as hydrogen and ammonia, which have very different combustion properties and performance.

Static flame stability

The high reactivity and diffusivity of hydrogen mean that it is strongly resistant to aerodynamic strain, making stabilisation challenging. Hydrogen flames have a propensity to propagate upstream from their intended anchoring location, which is known as flashback. In counterpoint, ammonia as a fuel suffers from low reactivity, making it difficult to stabilise flames, which can result in flame blow-off, where the reacting flow exits the combustor, and the flame is extinguished.

Both of these stabilisation phenomena pose significant safety risks in practical devices, and must be eliminated during the combustion system design; a process which requires a better understanding of the fundamental physics involved. Our research includes the study of blow-off and ignition in simple gas turbine relevant configurations.

Dynamic flame stability

Changes to the operating condition or fuel type can change the time delay between fresh reactants entering the combustor and heat being released. Badly tuned time-delays can result in a problematic coupling between the unsteady heat release rate and the acoustics of the combustion chamber, resulting in a phenomenon which is known as combustion or thermoacoustic instability.

Combustion instabilities can result in very large pressure oscillations, which can damage the engine or promote flashback. Again, these must be eliminated at the design stage, which requires a better understanding of the fundamental physics involved. In particular, our research focusses on simple gas turbine relevant single and multiple flame systems, including full annular and can-annular setups.

Methods

We use a range of cutting edge experimental and theoretical methods to build our understanding. The Turbulent Combustion Lab is a state-of-the-art research facility dedicated to improving our fundamental understanding of fluid mechanics and combustion phenomena. We use high speed laser and camera system to capture the flame unsteady heat release response, either through natural chemiluminescence from intermediate combustion products, or through Planar Laser Induced Fluorescence (PLIF). We use microphones and pressure sensors to characterize the acoustics, and Particle Image Velocimetry (PIV) to capture the velocity field.

Contact persons: Professor James Richard Dawson, Professor Jonas Moeck and Professor Nicholas Worth. 

Whilst there is a great drive for electrification of the automotive sector, it is agreed that there are many applications that internal combustion engines will remain the primary source of motive power for many years to come. These include larger compression engines found in trucks or off highway application, power generation and shipping. The implementation of new, alternative fuels for internal combustion engines is highly important in reducing global CO2 emissions and reducing harmful local emissions. These fuels include biofuels, e-fuels, ammonia and hydrogen blends. Questions over their ability to fully mitigate CO2 persist, as well as their impact on land use and food competition. These concerns are driving the research on their performance and emission reduction potential in realistic combustion environments. 

Focus of our work

The work conducted is primarily concerned with investigating new fuels in a compression ignition type engine. This includes studying fuel injection processes, injection strategies, mixing and emissions formation. In conjunction with numerical work, experimental work is conducted to examine possible chemical surrogates that may be used to provide a simplified model for combustion of reference diesel fuel, biodiesel type fuels as well as ammonia and hydrogen blends. Due to the complex nature of the multi-phase dynamics of spray combustion present in a compression ignition engine, the work involves examining turbulent reacting flows under high pressure conditions using state-of-the-art numerical and experimental techniques.

Methods

The Motorlab is equipped with a series of different experimental facilities. An optically accessible compression ignition combustion chamber (OACIC), consisting of a modified cylinder head on top of a large bore single cylinder engine is used to investigate injection, spray and combustion at high pressures. With the use of high-speed cameras and image intensifiers with high power LED illumination systems, in-flame soot, spray and ignition characteristics are examined. A fully instrumented, large automotive (3,2 liter) compression ignition engine is fitted with Horiba gas analyzer and Cambustion DMS 5000 to give a full emission spectrum for any new fuel. The engine is fitted with control system that allows user control of much of the engine’s operation. 

Experimental work is accompanied by numerical simulations using a cascade of numerical tools enabling the detailed studies of turbulent reacting flows. When employing detailed chemical models for reliable emissions predictions, 0D stochastic reactor tools are used based on statistical treatment of the turbulent flows. This enables full scale simulations over a wide range of conditions. For capturing spray interaction, spray break-up and thermodynamic features such as cavitation and flash boiling inside the injector, advanced multi-phase flow simulations are conducted based on computational fluid dynamics (CFD) tools using simplified and reduced chemical models. 

Contact person: Professor Terese Løvås

In the circular economy, waste turns from a burden to a valuable resource. In Waste-to-Energy applications, waste streams provide different forms of usable energy: heat for district heating networks and industrial processes, electricity, or fuel substitute for energy-intensive industries. New methods aim to upgrade waste streams into functional resources for material production in so-called Waste-to-Value processes. Examples are (bio-)methanol synthesis for chemical feedstock and thermo-chemical plastic recycling. Together, these strategies contribute to advancing the principles of the circular economy, aiming to minimize waste and maximize resource efficiency. Moreover, they assist in gradually reducing dependence on fossil fuels within industrial process chains and actively support the green transition.

Focus of our work

The design of the incinerator unit in Waste-to-Energy plants encompasses a range of technologies, from large-scale grate furnaces and rotary kilns to fixed and fluidized bed reactors. We aim to develop and employ computationally efficient numerical tools by combining computational fluid dynamics with stochastic reduced-order modeling techniques. Coupling these models with elemental resolved descriptions of feedstock composition and chemical reaction kinetics allows us to investigate fuel- and air-borne emissions and the formation of fouling gases.

Thermo-chemical Plastic Recycling

Thermochemical Plastic Recycling involves the pyrolysis or gasification of plastic waste, converting it into gas species that are then synthesized into base chemicals and new mono- and polymers. This method offers a solution for plastic wastes that are unsuitable for traditional mechanical recycling due to their complex composition. Our research aims to understand and predict the thermochemical decomposition of multi-composite plastics comprehensively. This knowledge informs the design of necessary cleaning and upgrading systems, thereby enhancing the overall efficiency of plastic recycling processes.

Methods

Our methods involve understanding fundamental aspects and translating these findings into models to develop practical engineering solutions. These methods combine a spectrum of techniques, ranging from fundamental high-fidelity multiphase simulations, characterizing waste feedstocks at their atomic level and particle-interaction models via conducting emission analyses through large-scale computational fluid dynamics simulations to fast reduced-order and chemical reactor modeling to optimize industrial processes. The connecting threads are detailed chemical mechanisms that resolve product speciation and predict emission formation.

Contact person: Associate Professor Corinna Schulze-Netzer