scholarly journals Mathematical simulation of transient combustion of melted energetic materials

2019 ◽  
pp. 4-10
Author(s):  
V.E. Zarko
Keyword(s):  
Heat Flux ◽  
Burning Rate ◽  
Energetic Materials ◽  
Burning Surface ◽  
Computer Code ◽  
Problem Formulation ◽  
Chemical Transformations ◽  
Transient Pressure ◽  
Transient Combustion ◽  
Equilibrium Evaporation

The computer code is elaborated for numerical simulation of transient combustion of energetic materials (EM) subjected to the action of time-dependent heat flux and under transient pressure conditions. It allows studying combustion response upon interrupted irradiation (transient pressure) and under action of periodically varied heat flux (pressure) in order to determine stability of ignition transients and parameters of transient combustion. The originally solid EM melts and then evaporates at the surface. It is assumed that chemical transformations occur both in the condensed and gas phases. At the burning surface, the phase transition condition in the form of Clapeyron-Clausius law for equilibrium evaporation is formulated that corresponds to the case of combustion of sublimated or melted EM. The paper contains description of transient combustion problem formulation and several examples of transient combustion modeling. At present time a precise prediction of transient burning rate characteristics is impossible because of the lack of information about magnitude of EM parameters at high temperatures. However, the simulation results bring valuable qualitative information about burning rate behavior at variations in time of external conditions – radiant flux and pressure.

scholarly journals Burning rate of solid homogeneous energetic materials with a curved burning surface

2019 ◽  
Vol 1250 ◽  
pp. 012041
Author(s):  
S.A. Rashkovskiy ◽  
V.G. Krupkin ◽  
V.N. Marshakov
Keyword(s):  
Burning Rate ◽  
Energetic Materials ◽  
Burning Surface

Experimental Measurements and CFD Evaluation of the Onset Flow Boiling at Low Pressure and High Subcooling Flow of R-11 Within Vertical Annulus

2014 ◽  
Author(s):  
Y. Bouaichaoui ◽  
R. Kibboua ◽  
M. Matkovič
Keyword(s):  
Heat Flux ◽  
Liquid Velocity ◽  
Flow Boiling ◽  
Fluid Model ◽  
Computer Code ◽  
Computational Method ◽  
Subcooled Boiling ◽  
Two Phase ◽  
Local Flow ◽  
Wide Range

The knowledge of the onset of subcooled boiling in forced convective flow at high liquid velocity and subcooling is of importance in thermal hydraulic studies. Measurements were performed under various conditions of mass flux, heat flux, and inlet subcooling, which enabled to study the influence of different boundary conditions on the development of local flow parameters. Also, some measurements have been compared to the predictions by the three-dimensional two-fluid model of subcooled boiling flow carried out with the computer code ANSYS-CFX-13. A computational method based on theoretical studies of steady state two phase forced convection along a test section loop was released. The calculation model covers a wide range of two phase flow conditions. It predicts the heat transfer rates and transitions points such as the Onset of Critical Heat Flux.

scholarly journals A New Erosive Burning Model of Solid Propellant Based on Heat Transfer Equilibrium at Propellant Surface

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Yanjie Ma ◽  
Futing Bao ◽  
Lin Sun ◽  
Yang Liu ◽  
Weihua Hui
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Burning Rate ◽  
Rocket Motor ◽  
Solid Rocket Motor ◽  
Erosive Burning ◽  
Computational Data ◽  
And Performance ◽  
Solid Rocket ◽  
Propellant Surface

Erosive burning refers to the augmentation of propellant burning rate appears when the velocity of combustion gas flowing parallel to the propellant surface is relatively high. Erosive burning can influence the total burning rate of propellant and performance of solid rocket motors dramatically. There have been many different models to evaluate erosive burning rate for now. Yet, due to the complication processes involving in propellant and solid rocket motor combustion, unknown constants often exist in these models. To use these models, trial-and-error procedure must be implemented to determine the unknown constants firstly. This makes many models difficult to estimate erosive burning before plenty of experiments. In this paper, a new erosive burning rate model is proposed based on the assumption that the erosive burning rate is proportional to the heat flux at the propellant surface. With entrance effect, roughness, and transpiration considered, convective heat transfer coefficient correlation proposed in recent years is used to compute the heat flux. This allows the release of unknown constants, making the model universal and easy to implement. The computational data of the model are compared with different experimental and computational data from different models. Results show that good accuracy (10%) with experiments can be achieved by this model. It is concluded that the present model could be used universally for erosive burning rate evaluation of propellant and performance prediction of solid rocket motor as well.

Interactions Between Parallel Minichannels During Flow Boiling of R134A

2014 ◽  
Author(s):  
Dolaana M. Khovalyg ◽  
Predrag S. Hrnjak ◽  
Aleksandr V. Baranenko ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Visualization ◽  
Mass Flux ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Transient Pressure ◽  
Correlation Degree ◽  
Channel Relationship ◽  
The Individual

This work focuses on the study of flow boiling of R134a in 0.54 mm square parallel minichannels, with a particular focus on the transient pressure drop of individual channels and their interaction. The individual pressure drop in each passage was analyzed to establish the inter-channel relationship; additionally, the effect of heat and mass flux and the inlet vapor qualities on the flow patterns of each channel was studied based on flow visualization and pressure drop measurements. The mass flux and heat flux in the experiments were varied up to 800 kg/m2s and 10 kW/m2 respectively. The heat flux was controlled and varied independently in each channel. Results illustrate that interaction between channels exists, and the correlation degree depends on the flow boiling dynamics in each passage. The pressure drop oscillation in each channel affects the flow redistribution between channels. A channel subjected to the least heat flux tends to correlate the most with greater heated channels because of the mass flux fluctuations caused by boiling phenomena in other channels.

scholarly journals Observation on a fire whirl in a vertical shaft using high-speed camera and associated correlation derived

2019 ◽  
pp. 266-266
Author(s):  
Hing Hung ◽  
Shousuo Han ◽  
Wan Chow ◽  
Cheuk Chow
Keyword(s):  
Burning Rate ◽  
High Speed ◽  
Tall Buildings ◽  
Burning Surface ◽  
Air Entrainment ◽  
Pool Fire ◽  
Flame Height ◽  
Vertical Shaft ◽  
High Speed Camera ◽  
Fire Whirl

The fire whirl generated by burning a pool fire in a vertical shaft with a single corner gap of appropriate width was studied using a high-speed camera. A 7-cm diameter pool propanol fire with heat release rate 1.6 kW in free space was burnt inside a 145-cm tall vertical shaft model with gap widths lying between 2 cm and 16 cm. The flame height was between 0.25 m and 0.85 m for different gap widths. Photographs taken using a high-speed camera at critical times of swirling motion development were used to compare with those taken using a normal camera. From the experimental observations on flame swirling by a high-speed camera, stages for generating the fire whirl were identified much more accurately. Two flame vortex tubes moving over the horizontal burning surface of the liquid pool were observed. Based on these observations a set of more detailed schematic diagrams on the swirling motion was constructed. From the observed flame heights under different gap widths and using three assumptions on the variation of air entrainment velocity with height, an empirical expression relating the burning rate with flame height and the corner gap width was derived from the observation with high-speed camera. The correlation expression of the burning rate of the pool fire obtained would be useful in fire safety design in vertical shafts of tall buildings.

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