284 publications from this institution
The energy reforms which have taken pla ce in December of 2013 in Mexico allow foreign companies for the first time since the nationalization of the oil in 1938 to operate in the exploration and production sta ge of hydrocarbons. This reform will allow them to tap deep water oil and shale gas, bo th of which until the moment have only just been explored b y the national oil company PEMEX . The experiences of shale gas exploitation from other countries have been studied to carry out an analysis of the measures needed in Mexico to develop shale gas in a responsible and environmentally friendly manner. It also sets out the areas which need special attention due to the particular social and legal conditions which are present in Mexico.
Renewably generated ammonia offers a form of carbon-free chemical energy storage to meet the differences between uncertain supply and fluctuating demand and has the potential to support future energy requirements. The storage/transportation characteristics of NH3 are favorable compared with H2; however, there are combustion research challenges to enhance fuel reactivity while reducing harmful emissions production. The purpose of this work was to evaluate different fuel delivery concepts for a representative gas turbine combustor. An experimental and numerical comparison was made between swirl-stabilized premixed and diffusion NH3–air flames at elevated inlet temperature (473 K). The exhaust NOx and NH3 emissions generated from each concept were quantified to optimize combustor performance. High-speed OH* and NH2* chemiluminescence was employed to characterize the change in flame topology with variation in fuel–air equivalence ratio, and the resultant influence on measured emission concentrations. Chemiluminescence intensities were shown to elucidate changes in sampled exhaust emissions, enabling detailed analysis of intermediate chemistry. A comparison was made between experimental data and kinetic simulations, demonstrating the sensitivity of NOx emissions to premixed fuel–air equivalence ratio. A comparison was also made between exclusive primary airflow, and the staged introduction of secondary air, to quantify the change in NOx production between each configuration and improve fuel burnout. Secondary air loadings were incrementally increased through the combustor. Finally, reactant humidification was employed as a secondary process for NOx reduction, having shown favorable performance with NH3–H2 mixtures, with the efficacy compared for both premixed and diffusion configurations.
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In the cold rolling process of steel strip products, strip breakage is an undesired production failure which can lead to yield loss, reduced work speed and equipment damage. To perform a root cause analysis, conventional physics-based approaches which focus on mechanical and metallurgical principles have been applied in a retrospective manner. With the advancement of data acquisition technologies, numerous process monitoring data is collected by various sensors deployed along this process; however, conventional approaches cannot take advantage of these data. In this paper, a machine learning-based approach is proposed to characterise and model strip breakage in a predictive manner. First, to match the temporal characteristic of strip breakage which occurs instantaneously, historical multivariate time-series data of a cold rolling process were extracted in a run-to-failure manner, and a sliding window strategy was adopted for data annotation. Second, breakage-centric features were identified from three facets – physics-based approaches, empirical knowledge and data-driven features. Finally, these features were used as inputs for strip breakage modelling using recurrent neural networks (RNNs), which are specialised in discovering underlying patterns embedded in time-series data. An experimental study using real-world data collected from a cold-rolled electrical steel strip manufacturer revealed the effectiveness of the proposed approach.
Flame flashback is one of the central combustion instabilities, especially when it appears in the form of boundary layer flashback (BLF) or combustion induced vortex breakdown (CIVB) flashback, some of the most common instabilities in swirl combustors. This paper focuses on mitigating the phenomenon of CIVB and BLF flashback mechanisms using different nozzle configurations while using central air injection. Studies were conducted on a 150-kW tangential swirl burner manufactured and previously characterised at Cardiff University. The effects of different nozzle heights (hn) with and without microstructure on the swirl flow characteristics were investigated experimentally by utilising an LDA system. Different strip heights (hm) of a wire woven mesh have been employed as a liner on the smooth nozzle to change its surface roughness. It was found that longer smooth nozzles (hn/Ro=2.3) led to promotion of stability in the swirl burner by minimising the axial velocity defect while decreasing turbulence downstream the dump plane. Moreover, the average measurements show that the burner nozzles with microstructured surfaces enable improvements in controlling the BLF flashback and hence reduces outflow drag. It was found that the microstructured mesh alters the flow structure near the wall by increasing the velocity adjacent to this region delivering further resistance to BLF. On the other hand, using both central air injection and the nozzle with and without the microstructured surface can affect the operability of the gas turbine combustors.
Combustion instabilities are considered one of the most serious challenges for developing combustion systems through the years. Undesirable issues linked to these phenomena represent a risk for such systems especially in gas turbines and propulsion devices where the propagation of these instabilities can even lead to considerable damages. Flame flashback from the combustion chamber into premixer represents one of the most important combustion instability issue in swirl combustors used in gas turbines. This study proposes an experimental and numerical approach to validate the use of a central air injection in swirl combustors to reduce flame flashback propensity via controlling the turbulence generation at the tip of the flame while pushing the CRZ, thus retarding the appearance of the CIVB, to mitigate the progression of combustion into the system. Results showed the potential of this technique to affect turbulence generation and pushing back the flame into the combustion chamber, increasing operability limits. Very good agreement was achieved between experimental and numerical results, demonstrating that the use of injection through the central core of the system not only controls the position of the recirculation zone but also affects turbulence and mitigates other forms of flame flashback.
In recent decades there has been a strong trend towards the use of lean premixed combustion in order to produce gas turbine systems that are compliant with air quality regulations. Additional growing interest in using alternative fuels has drawn many problems in terms of operational stability, thus there have been extensive investigations to achieve more stable and reliable combustion systems. Flame flashback has been one of the major instability problems that have the potential of causing considerable damage to the combustion system hardware in addition to significant increase of emissions such as CO and NOx. Swirl combustors are proven as effective flame stabilisers over wide range of operation conditions due to swirl structures which provide a low velocity region that enables flame anchoring. However the interaction between swirl structures and swirl burner geometries can considerably alter the stability regime downstream the burner exit plane. Using central injectors either as a central bluff body or to inject fuel diffusively have been used successfully to achieve wide stability limits and prevent upstream flame propagation. However, central injectors in swirl combustors can be subject to large amounts of heat, which can cause flashback, subsequently increasing maintenance cost and reducing the predicted operating life of the system. This paper present a series of experiments using a well-characterised tangential swirl burner to investigate the effect of using diffusive air injection on flow field characteristics and how it can affect the lower instability limits through altering the flashback mechanism by Combustion Induced Vortex Breakdown (CIVB). Results show that using diffusive air stream injection affects flashback trends significantly by providing a wider range of stability limits both in terms of equivalence ratio and mass flow rate which implies the possibility of working at higher power outputs compared to the case when using a central body injector. This technique can be considered a promising technology in terms of flexibility of operation because it enables switching to another air stream diameter while maintaining full load operation as opposed to the use of central body injectors.
