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Abstract Knowledge of flame responses to acoustic perturbations is of utmost importance to predict thermoacoustic instabilities in gas turbine combustors. However, measuring transfer functions linking acoustic quantities upstream and downstream of flames is very challenging in practical systems and these measurements can significantly deviate from state-of-the-art models. Moreover, there is a lack of studies investigating the effect of hydrogen enrichment on the response of natural gas (NG) flames. In this work, measurements of flame transfer matrices (FTM) of turbulent H2/NG flames in an atmospheric combustor featuring an axial swirler burner have been performed, allowing us to unravel the transition between FTM in fully premixed (FP) and in technically premixed (TP) conditions. Furthermore, imaging of OH* chemiluminescence and OH-Planar Laser Induced Fluorescence are obtained for characterizing the topology of the flame for varying H2 fraction and mixing conditions. Transfer matrices are measured using the multi-microphone method for H2 fractions ranging from 12% to 43% in power. Afterwards, the flame transfer functions (FTF), which linearly relate the coherent fluctuations of the heat release rate to the acoustic velocity oscillations, are obtained from the FTM by using the Rankine-Hugoniot jump conditions across the flame. Using the OH* chemiluminescence intensity as a surrogate for the heat release rate, the FTF based on this optical measurement is also extracted and compared to the one exclusively obtained with the multi-microphone method. As expected, the two different methods are in very good agreement for the FP case and significantly differ for the TP case. Indeed, chemiluminescence fluctuations cannot be directly linked to heat release rate fluctuations when the acoustic forcing induces equivalence ratio fluctuations at the flame, making the optical method unusable for TP configurations. We also show that the two methods agree in the high end of the explored excitation frequency range and we provide an explanation to this intriguing finding. Moreover, we investigate the sensitivity of the FTM measurement to the estimate of the speed of sound in the rig in FP conditions. Finally, the measured FTFs are fitted with FTF models based on multiple distributed time delays. This allows us to explain the frequency dependence and the hydrogen fraction dependence of the gain and the phase in FP and TP conditions.

Abstract Knowledge of flame responses to acoustic perturbations is of utmost importance to predict thermoacoustic instabilities in gas turbine combustors. However, measuring transfer functions linking acoustic quantities upstream and downstream of flames is very challenging in practical systems and these measurements can significantly deviate from state-of-the-art models. Moreover, there is a lack of studies investigating the effect of hydrogen enrichment on the response of natural gas (NG) flames. In this work, measurements of flame transfer matrices (FTM) of turbulent H2/NG flames in an atmospheric combustor featuring an axial swirler burner have been performed, allowing us to unravel the transition between FTM in fully premixed (FP) and in technically premixed (TP) conditions. Furthermore, imaging of OH* chemiluminescence and OH-Planar Laser Induced Fluorescence are obtained for characterizing the topology of the flame for varying H2 fraction and mixing conditions. Transfer matrices are measured using the multi-microphone method for H2 fractions ranging from 12% to 43% in power. Afterwards, the flame transfer functions (FTF), which linearly relate the coherent fluctuations of the heat release rate to the acoustic velocity oscillations, are obtained from the FTM by using the Rankine-Hugoniot jump conditions across the flame. Using the OH* chemiluminescence intensity as a surrogate for the heat release rate, the FTF based on this optical measurement is also extracted and compared to the one exclusively obtained with the multi-microphone method. As expected, the two different methods are in very good agreement for the FP case and significantly differ for the TP case. Indeed, chemiluminescence fluctuations cannot be directly linked to heat release rate fluctuations when the acoustic forcing induces equivalence ratio fluctuations at the flame, making the optical method unusable for TP configurations. We also show that the two methods agree in the high end of the explored excitation frequency range and we provide an explanation to this intriguing finding. Moreover, we investigate the sensitivity of the FTM measurement to the estimate of the speed of sound in the rig in FP conditions. Finally, the measured FTFs are fitted with FTF models based on multiple distributed time delays. This allows us to explain the frequency dependence and the hydrogen fraction dependence of the gain and the phase in FP and TP conditions.

Statoil's history since 2001 has been turbulent and transformative. The company's partial privatization in 2001 attuned its management more to investors than to the state. An unprecedented rise in oil prices between 2004 and 2014 and the merger with Norsk Hydro's oil and gas division in 2007 buoyed the company's rapid internationalization, transforming it from a Norwegian company into a global one. And the impending climate crisis forced the company to consider a world without oil and gas, transforming it into an energy company under a new name, Equinor.Navigating these turbulent global events, Statoil met with success and failure. Major strategic shifts into unconventional oil and gas and offshore wind proved particularly vexing, exposing a recurring tension in Statoil's governance between public expectations and capital market demands. On the one hand, Statoil's management felt the pressure from investors to become a global oil and gas company. On the other, management had to navigate public demands to become a greener company. Out of that conundrum emerged Equinor as a somewhat more global and greener company than Statoil was in 2001 but still with deep roots in Norway and in oil and gas.

Statoil's history since 2001 has been turbulent and transformative. The company's partial privatization in 2001 attuned its management more to investors than to the state. An unprecedented rise in oil prices between 2004 and 2014 and the merger with Norsk Hydro's oil and gas division in 2007 buoyed the company's rapid internationalization, transforming it from a Norwegian company into a global one. And the impending climate crisis forced the company to consider a world without oil and gas, transforming it into an energy company under a new name, Equinor.Navigating these turbulent global events, Statoil met with success and failure. Major strategic shifts into unconventional oil and gas and offshore wind proved particularly vexing, exposing a recurring tension in Statoil's governance between public expectations and capital market demands. On the one hand, Statoil's management felt the pressure from investors to become a global oil and gas company. On the other, management had to navigate public demands to become a greener company. Out of that conundrum emerged Equinor as a somewhat more global and greener company than Statoil was in 2001 but still with deep roots in Norway and in oil and gas.

Rising temperatures, increasingly frequent extreme weather events and sea level rise are playing a growing role in shaping displacement, rural-urban migration, circular movements but also voluntary and forced immobilities. The debate on climate mobilities – the interplay between climate change and human mobility – is currently moving centre stage in migration studies. Migration theory, on the other hand, does not necessarily reflect sufficiently on the role of the environment in mobility patterns. Including an understanding of the complex nature of climate mobilities avoids assuming climate change related mobility as new or exceptional per se, and offers understanding of the plural, multi-causal, and political ways in which climate change and human im/mobilities intersect.

Rising temperatures, increasingly frequent extreme weather events and sea level rise are playing a growing role in shaping displacement, rural-urban migration, circular movements but also voluntary and forced immobilities. The debate on climate mobilities – the interplay between climate change and human mobility – is currently moving centre stage in migration studies. Migration theory, on the other hand, does not necessarily reflect sufficiently on the role of the environment in mobility patterns. Including an understanding of the complex nature of climate mobilities avoids assuming climate change related mobility as new or exceptional per se, and offers understanding of the plural, multi-causal, and political ways in which climate change and human im/mobilities intersect.

The large thermal potentials with geothermal gradient of abandoned wells provide the possibility and opportunity for carbon-neutrality transition of district heating systems, whereas energy harvesting from abandoned geothermal wells is full of challenges, due to the considerable initial investment in economic cost, system performance degradation, and so on. In this chapter, a systematic and comprehensive review on the application techniques of abandoned wells is presented, in terms of advanced thermal/power conversions, renewable integrations for district heating, and strategies for performance enhancement. Discussions on real applications have been conducted and future prospects presented, from perspectives of lifetime system performance, techno-economic feasibility analysis, and potential assessment of abandoned wells for carbon-neutrality transition. The results of this chapter can provide preliminary knowledge and cutting-edge technologies on renewable integrations with abandoned wells, so as to demonstrate techno-economic-environmental potentials of abandoned wells and contributions toward carbon-neutrality transition. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Design & Construction Management