Vent Size Effect on Self-extinction of Pool Fire in a Ceiling Vented Compartment

AbstractThe self-extinction behavior of N-heptane pool fire located in a ceiling-vented compartment is investigated experimentally. The compartment is a rectangular chamber of 1.00 m (L) × 1.00 m (W) × 0.75 m (H) with only a ceiling vent with sizes between 0 and 0.490 m × 0.490 m. Three sizes of pans with the diameters of 0.10 m, 0.141 m and 0.20 m were at the center of the compartment with similar initial fuel thickness. The impact of vent area on fuel consumption and flame extinction time is mainly examined as the result, meanwhile the local oxygen concentration near the fire source and the mass loss rate of fuel are also reported. The result shows that the pool fire burning behavior can be classified into four types according to the ceiling vent size. The extinction time te of first type of fire nearly equals to the closed condition, while it grows sharply with vent size for the second type of fire. When the fire belongs to the third type, te decreases with vent size due to the growth of fuel burning rate, and for the fourth type, te keeps constant again with the well-ventilated/condition. Based on species concentration, the ceiling vent size can be normalized into (ρ∞g1/2Av5/4)/(mF”AF). An empirical exponential relationship between self-extinction time ratio and the dimensionless ceiling vent size was proposed, and the results well ntegrate all the profiles of self-extinction time of different fire sizes

On the Self-extinction Time of Pool Fire in Closed Compartments

AbstractThe self-extinction time of pool fires in closed compartments was studied. Experiments were conducted in two bench-scale compartments with volumes of 0.75 m3 and 17.55 m3. It was found that the fire self-extinction time was proportional to the compartment volume but inversed to the pool area for n-heptane. The fuel mass loss rate in closed compartments was lower than that in the open space. The fire self-extinction occurred when the local oxygen mole fraction in the flame vicinity descended to a level of 10.7-15.3%. The mean remaining oxygen mole fraction at the self-extinction moment was about 14.1%. Based on the mass conservation of the oxygen, a model for predicting the self-extinction time of pool fires in closed compartments was developed. By defining a concept of the dimensionless fire volume, the dimensionless self-extinction time was proposed. The dimensionless self-extinction time is proportional to the difference between the initial and remaining oxygen mass fraction, fuel properties, such as heat of combustion and stoichiometric ratio etc., but inverses to the dimensionless fire volume and the integrated combustion coefficient. The predicted results showed a good agreement with the experimental results. The model also provides a good prediction for the results of NRL's t sts

Calibration of the CMS hadron calorimeters using proton-proton collision data at root s=13 TeV

Methods are presented for calibrating the hadron calorimeter system of theCMSetector at the LHC. The hadron calorimeters of the CMS experiment are sampling calorimeters of brass and scintillator, and are in the form of one central detector and two endcaps. These calorimeters cover pseudorapidities vertical bar eta vertical bar ee data. The energy scale of the outer calorimeters has been determined with test beam data and is confirmed through data with high transverse momentum jets. In this paper, we present the details of the calibration methods and accuracy.Peer reviewe

Research status of warship fire safety engineering

The theory of warship fire safety engineering is the basis of damage control engineering. According to the public safety triangle and the characteristics of ship damage protection engineering, this paper proposes a theoretical framework system for ship fire safety engineering, including ship fire development, ship fire damage and ship fire protection. The progress of these three parts are summarized in such aspects as enclosed fire dynamics, open space fire dynamics, fire damage mechanisms for personnel, equipment and structures, fire smoke control, fire elimination technology and new fire extinguishing technology. By optimizing the theoretical system of warship fire safety engineering and improving fire prevention and control technology, the survivability of warships will be enhanced

Blended-fuel based EDC combustion model and its application in heptane-ethanol fire simulation

The blended-fuel based eddy-dissipation-concept combustion model was newly developed in the FireFOAM framework, and applied to simulate 30 cm×30 cm heptane-ethanol pool fire. Comparison was made of fire height, centerline temperature against experimental measurements, which shows that they match very well with each other. However, further studies are needed to examine the validation of this model in fire simulations with various scales

An optimization method for the distance between exits of buildings considering uncertainties based on arbitrary polynomial chaos expansion

The distance between exits is an important design parameter in fire safety design of buildings. In order to find the optimal distance between exits under uncertainties with a low computational cost, the surrogate model (i.e. approximation model) of evacuation time is constructed by the arbitrary polynomial chaos expansion. Through a two-stage nested Monte Carlo simulation of this surrogate model, the optimal distance between exits under uncertainty is found efficiently. In order to demonstrate the proposed method, a single room with two exits is presented as a fire compartment and uncertainties of occupant density and child-occupant load ratio are also considered

Massive Spatial Well Clustering Based on Conventional Well Log Feature Extraction for Fast Formation Heterogeneity Characterization

AbstractRecent enhancements in computational capacity provide an opportunity for harnessing the enormous amount of reservoir data already acquired and extracting useful information for hydrocarbon exploration, development, and production. This article reports a three-step clustering technique to determine well groups based on subsurface geological heterogeneity using feature extraction, hierarchical ensemble clustering, and spatial mapping. The first step of the presented methodology is to group the wells into different clusters based on the formation rock composition and property features extracted from well logs using the expectation maximization algorithm. The one-dimensional (1D) stacking pattern of each well log curve is expressed through a two-dimensional (2D) transformation scheme. Thus, the clustering can capture the vertical stacking patterns of well logs, which is essential for reservoir heterogeneity characterization. This base clustering process generated a feature matrix which is further grouped through the hierarchical ensemble clustering in a latent space of well logs in the second step. Through the ensemble clustering, different clustering proposals obtained from the base clustering are integrated corroboratively to reflect a comprehensive feature of all studied logs. In the third step, the spatial clustering is performed based on the ensemble results, considering the spatial distances between well locations in the target area. The results of the 2D spatial map may provide insights into the sedimentary depositional environment in terms of the lateral geological heterogeneity features. Therefore, the proposed clustering technique can present a fast geological modeling method to integrate geological heterogeneity features presented in multiple well logs, which is not yet fully utilized in traditional geomodeling approaches. The results can also support further reservoir studies, such as petrophysical modeling, reservoir modeling, and fluid flow simulation studies

Research on Material Removal Mechanism of C/SiC Composites in Ultrasound Vibration-Assisted Grinding

C/SiC composites are the preferred materials for hot-end structures and other important components of aerospace vehicles. It is important to reveal the material removal mechanism of ultrasound vibration-assisted grinding for realizing low damage and high efficiency processing of C/SiC composites. In this paper, a single abrasive particle ultrasound vibration cutting test was carried out. The failure modes of SiC matrix and carbon fiber under ordinary cutting and ultrasound cutting conditions were observed and analyzed. With the help of ultrasonic energy, compared with ordinary cutting, under the conditions of ultrasonic vibration-assisted grinding, the grinding force is reduced to varying degrees, and the maximum reduction ratio reaches about 60%, which means that ultrasonic vibration is beneficial to reduce the grinding force. With the observation of cutting debris, it is found that the size of debris is not much affected by the a p with ultrasound vibration. Thus, the ultrasound vibration-assisted grinding method is an effective method to achieve low damage and high efficiency processing of C/SiC composites