City-level decision-making requires timely access to a wide range of relevant and comprehensible data and information.Although a wide range of research on energy and cities is on-going across the social, engineering and natural sciences, it cannot be taken for granted that the questions being asked and the way questions are structured reflect practitioner perspectives and requirements. This paper discusses the ways in which research questions are formed and interpreted by actors in academic research and research user communities. We also report a set of research questions produced via an initial trial of a two stage, participative process consisting of (a) a survey targeted at city-focussed practitioners in the United Kingdom (UK) with an interest in lower carbon energy futures; and (b) a workshop integrating practitioner and academic perspectives. Comparing the set of research questions identified with themes in the academic literature, we find that research and practitioner communities concur on the importance of reducing energy demand and also on a number of cross-cutting issues. However, we also find that academic research places a greater emphasis on the interfaces between the energy system and other urban systems. We conclude that the two stage, participative process followed can serve to generate and legitimate city-related research questions through collaboration between stakeholders and academic researchers.

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Freely propagating laminar premixed flames of stoichiometric mixtures of gasoline surrogate and iso-octane with air are computed using three chemical kinetics mechanisms of varied complexity and detail. A good agreement of the computed burning velocities with past experimental data is observed. The burning velocities of these mixtures at temperature of 850 ≤ T ≤ 950 decrease with pressure up to about 3 MPa and starts to increase beyond this pressure. This contrasting behavior is related to the role of pressure dependent reaction involving OH and the influence of this radical on the fuel consumption rate. The results suggest that the overall order of the combustion reaction is larger than two at pressures higher than 3 MPa. Hence, one must be cautious in extending the commonly used laminar flame speed correlation with pressure to thermo-chemical conditions of interest for future engines.

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Direct numerical simulation (DNS) data of freely propagating turbulent premixed flame of stoichiometric hydrogen air mixture inside a closed vessel is analysed to study a sub-grid combustion closure based on unstrained flamelet approach. This modelling framework needs closures for the sub-grid scale (SGS) reaction rate and scalar dissipation rate. The results show that the closure models for these two SGS quantities work quite well. The dissipation rate closure involves a scale dependent parameter, β c , which is related to the flame curvature induced effects. The reactivity of reactant mixture increases with time in isochoric combustion because the mixture temperature and pressure increases with time. This also influences the parameter β c and thus the dynamic evaluation of this parameter is investigated using the DNS data.