Richard Carvel

The influence of longitudinal ventilation systems on fires in tunnels

Abstract Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study investigating the influence of forced longitudinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, made by a panel of experts, with data from experimental fire tests in tunnels. Results are presented and the implications are discussed. The influence of longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts’ estimates, causing a fire to grow ten times larger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rate of small pool fires may be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected to be greatly affected by forced ventilation at low ventilation velocities.

Variation of heat release rate with forced longitudinal ventilation for vehicle fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study using a Bayesian methodology to estimate the effect of forced longitudinal ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of car and heavy goods vehicle (HGV) fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that forced ventilation has a great enhancing effect on the HRR of HGV fires, but has little effect on the HRR of car fires.

A BAYESIAN ESTIMATION OF THE EFFECT OF FORCED VENTILATION ON A POOL FIRE IN A TUNNEL

Abstract A Bayesian methodology is used to estimate the effect of longitudinal forced ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of three different sizes of pool fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that for some fires the ventilation would be expected to reduce the HRR and for some fires to increase it. Overall, expert opinions have been found to differ significantly.

Overview of Problems and Solutions in Fire Protection Engineering of Wind Turbines

The wind energy industry is one of today’s leading industries in the renewable energy sector, providing an affordable and sustainable energy solution. However, the wind industry faces a number of challenges, one of which is fire and that can cast a shadow on its green credentials. The three elements of the fire triangle, fuel (oil and polymers), oxygen (wind) and ignition (electric, mechanical and lighting) are represent and confined to the small and closed compartment of the turbine nacelle. Moreover, once ignition occurs in a turbine, the chances of externally fighting the fire are very slim due to the height of the nacelle and the often remote location of the wind farm. Instances of reports about fires in wind farms are increasing, yet the true extent of the impact of fires on the energy industry on a global scale is impossible to assess. Sources of information are incomplete, biased, or contain non-publically available data. The poor statistical records of wind turbine fires are a main cause of concern and hinder any research effort in this field. This paper aims to summarise the current state of knowledge in this area by presenting a review of the few sources which are available, in order to quantify and understand the fire problem in wind energy. We have found that fire is the second leading cause of catastrophic accidents in wind turbines (after blade failure) and accounts for 10 to 30% of the reported turbine accidents of any year since 1980’s. In 90% of the cases, the fire leads to a total loss of the wind turbine, or at least a downtime that results in the accumulation of economic losses. The main causes of fire ignition in wind turbines are (in decreasing order of importance): lighting strike, electrical malfunction, mechanical malfunction, and maintenance. Due to the many flammable materials used in a wind turbine (eg. fiberglass reinforced polymers, foam insulation, cables) and the large oil storage used for lubrication of mechanical components, the fuel load in a turbine nacelle is commonly very large. The paper finishes with an overview of the passive and active protection options and the economics (costs, revenue and insurance) of wind turbines to put in context the value of a loss turbine compared to the cost and options of fire protection. We hope that this paper will encourage the scientific community to pursue a proper understanding of the problem and its scale, allowing the development of the most appropriate fire protection engineering solutions.

Modelling Fire Size and Spread in Tunnels

The heat release rate (HRR) of a fire in a tunnel is a crucial factor, both in terms of fire spread and smoke production. Key factors which influence the HRR are: {1} the nature of the burning item, {2} the tunnel geometry, {3} the ventilation conditions and {4} vehicle separation. This paper reports on work which has been undertaken over a number of years to model the dependence of HRR on these factors; the work is continuing. Specifically, Bayesian probabilistic models have been devised to model the dependence of the HRR of a fire on tunnel geometry and longitudinal forced ventilation and deterministic models have been devised to model fire spread from one item to another in a tunnel similar to the Channel Tunnel; again with longitudinal ventilation. Key interim results are presented.

Effects of Fire Retardants and Nanofillers on Fire Toxicity

Four polymers, polyamide 6, polypropylene, ethylene vinyl acetate and polybutylene terephthalate have been prepared with fire retardants, nanofillers, (both separately and together). The toxic product yield of each material has then been measured under different fire conditions. The influence of polymer nanocomposites and fire retardants in the formulations, on the yields of toxic products from fire, have been studied using the ISO 19700 steady state tube furnace, and it was found that under early stages of burning more carbon monoxide may be formed in the presence of nanofillers and fire retardants, but, under the more toxic under-ventilated conditions, there was a relative reduction in the toxic product yields. In general, the differences between the samples containing fire retardants and nanofillers are very small compared to the differences obtained under different fire conditions or in the presence of certain heteroelements, such as nitrogen or halogens.