LES modelling of explosion propagating flame inside vented chambers with various built-in solid obstructions

This paper presents large eddy simulations (LES) of the transient interaction between propagating turbulent premixed flames and solid obstructions mounted inside a laboratory scale combustion chamber. Interactions between the flame movement and the obstacles found to create both turbulence by vortex shedding and local wake/recirculation whereby the flame is wrapped in on itself, increasing the surface area available for combustion and the rate of local reaction rate. Accounting the influence of such local events in order to predict overall flame spreading speed, flame behaviour and the generated overpressure as a measure of reaction rate are extremely useful in combustion analysis in order to develop new models. The rise in the reaction rate due to the local nature of the flow and the increase in overall pressure due to the enhanced turbulence flame interactions as the flame travels through the unburned fuel air mixture are presented and discussed. The main focus of the current work is to establish the LES technique as a good numerical tool to calculate turbulent premixed propagating flames of propane/air mixture having equivalence ratio of 1.0, which is of practical importance in analysing explosion hazards and gas turbine combustors

Measurements and LES calculations of turbulent premixed flame propagation past repeated obstacles

This article was published in the journal, Combustion and Flame [© The Combustion Institute. Published by Elsevier Inc.] and the definitive version is available at: http://dx.doi.org/10.1016/j.combustflame.2011.05.008Measurements and large eddy simulations (LES) have been carried out for a turbulent premixed flame propagating past solid obstacles in a laboratory scale combustion chamber. The mixture used is a stoichiometric propane/air mixture, ignited from rest. A wide range of flow configurations are studied. The configurations vary in terms of the number and position of the built-in solid obstructions. The main aim of the present study is two folded. First, to validate a newly developed dynamic flame surface density (DFSD) model over a wide range of flow conditions. Second, to provide repeatable measurements of the flow and combustion in a well-controlled combustion chamber. A total of four groups are derived for qualitative and quantitative comparisons between predicted results and experimental measurements. The concept of groups offers better understanding of the flame-flow interactions and the impact of number and position of the solid baffle plates with respect to the ignition source. Results are presented and discussed for the flame structure, position, speed and accelerations at different times after ignitions. The pressure-time histories are also presented together with the regimes of combustion for all flow configurations during the course of flame propagation

Evaluation of partnership working within a community planning context

Partnership working has become an increasingly popular way of delivering public services. It is essential, however, that partnership working actually leads to the delivery of improved public services and evaluation will be required to ensure this is happening. This paper outlines efforts to evaluate the performance of a Community Planning Partnership in the East of Scotland. Community Planning Partnerships were instigated to try to reintegrate the public services in a local authority area which had previously been fragmented. Research on process issues with the partners using a partnership assessment tool and interviews suggest that the partnership is working satisfactorily. Unfortunately outcome evaluation based on focus groups from residents associations suggested serious difficulties and perceptions that services had not improved. As a result of the evaluation, meetings took place between partners and service users and significant progress was made towards resolving these difficulties