2013 Vol. 33, No. 4
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2013, 33(4): 337-343.
doi: 10.11883/1001-1455(2013)04-0337-07
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Abstract:
A simplified jet-flow model was proposed to understand the impact effects of underwater explosion-induced gas bubbles on the structures near explosive charges. The simplified jetflow model was based on the assumption that the displacement of the bubble around a cylindrical shell structure consisted of the buoyancy-induced displacement in a free field and the pull-induced displacement by the cylindrical shell structure. And the proposed model was used to investigate the damage effect of the cylindrical shell structure subjected to jet impact and the damage mode was analyzed. The results are helpful for the study on the damage of submarines impacted by underwater explosioninduced gas bubbles.
A simplified jet-flow model was proposed to understand the impact effects of underwater explosion-induced gas bubbles on the structures near explosive charges. The simplified jetflow model was based on the assumption that the displacement of the bubble around a cylindrical shell structure consisted of the buoyancy-induced displacement in a free field and the pull-induced displacement by the cylindrical shell structure. And the proposed model was used to investigate the damage effect of the cylindrical shell structure subjected to jet impact and the damage mode was analyzed. The results are helpful for the study on the damage of submarines impacted by underwater explosioninduced gas bubbles.
2013, 33(4): 344-350.
doi: 10.11883/1001-1455(2013)04-0344-07
Abstract:
By taking the engineering geology of the Fe-Zn polymetallic ore in Chaobuleng mine as an example, based on the blast damage theory of rock, the FLAC-3D software was adopted and ultrasonic tests were carried out to systematically explore the cumulative damage development in the surrounding rock of the re-exploited tunnel. In the above investigation, the surrounding rock was impacted by blasting for many times in the section excavation process. And the re-exploitation of the tiberium spike under the mined-out area adjacent to the re-exploited tunnel was numerically simulated. Thereby the stability of the surrounding rock of the mined-out area was analyzed. It is helpful for engineering application.
By taking the engineering geology of the Fe-Zn polymetallic ore in Chaobuleng mine as an example, based on the blast damage theory of rock, the FLAC-3D software was adopted and ultrasonic tests were carried out to systematically explore the cumulative damage development in the surrounding rock of the re-exploited tunnel. In the above investigation, the surrounding rock was impacted by blasting for many times in the section excavation process. And the re-exploitation of the tiberium spike under the mined-out area adjacent to the re-exploited tunnel was numerically simulated. Thereby the stability of the surrounding rock of the mined-out area was analyzed. It is helpful for engineering application.
2013, 33(4): 351-356.
doi: 10.11883/1001-1455(2013)04-0351-06
Abstract:
Aimed at the problem of gas explosion in coal mine after sealing the fire zone, experiments were conducted to analyze the impact factors of gas explosion limits including temperature, pressure, combustible gas (CO) and inert gas (N2 and CO2). The experimental results show that at normal temperature and pressure, the lower gas explosion limit is at the methane volume fraction of 5 percent and the upper gas explosion limit is at the methane volume fraction of 13.5 percent. And CO2 has greater inerting effect than N2. According to the experimental data, a new explosion triangle of mixed inflammable gases is rebuilt and the inerting regions were newly divided, which can provide a new method to prevent gas explosion after sealing the fire region. Amount of inert gas which needed to ensure against explosion can be calculated by the explosion triangle. Meanwhile, properly controlling the impact factors can decrease the risk of gas explosion.
Aimed at the problem of gas explosion in coal mine after sealing the fire zone, experiments were conducted to analyze the impact factors of gas explosion limits including temperature, pressure, combustible gas (CO) and inert gas (N2 and CO2). The experimental results show that at normal temperature and pressure, the lower gas explosion limit is at the methane volume fraction of 5 percent and the upper gas explosion limit is at the methane volume fraction of 13.5 percent. And CO2 has greater inerting effect than N2. According to the experimental data, a new explosion triangle of mixed inflammable gases is rebuilt and the inerting regions were newly divided, which can provide a new method to prevent gas explosion after sealing the fire region. Amount of inert gas which needed to ensure against explosion can be calculated by the explosion triangle. Meanwhile, properly controlling the impact factors can decrease the risk of gas explosion.
2013, 33(4): 357-362.
doi: 10.11883/1001-1455(2013)04-0357-06
Abstract:
Two common powders in coal mine laneways, coal dust and rock dust, were spread evenly at the experimental tube bottoms, respectively. Subtle thermocouples and flame photoelectric sensors were adopted to obtain the premixed methane-air flame parameters including transient temperature, flame front position and flame propagating velocity in the tube. And the influencing mechanisms of the two powers on flame propagation were preliminarily analyzed. The experimental results show that the coal dust can accelerate the flame propagation in the tube, and the rock dust can suppress the flame propagation, but the mechanisms of acceleration or suppression are essentially different. When the coal dust is spread in the tube, the flame transient temperature curves at test points take on obvious twin-peak structural waves and the reaction zones widen. It reveals that the methane-coal dust composite flame is formed between the reactive coal dust and the methane. When the rock dust is spread in the tube, the transient temperatures at test points all decrease, and the temperature half-peak widths narrow. It can explain that spreading rock powder in coal mine laneways can prevent or mitigate the methane-coal dust explosion hazards to a certain extent.
Two common powders in coal mine laneways, coal dust and rock dust, were spread evenly at the experimental tube bottoms, respectively. Subtle thermocouples and flame photoelectric sensors were adopted to obtain the premixed methane-air flame parameters including transient temperature, flame front position and flame propagating velocity in the tube. And the influencing mechanisms of the two powers on flame propagation were preliminarily analyzed. The experimental results show that the coal dust can accelerate the flame propagation in the tube, and the rock dust can suppress the flame propagation, but the mechanisms of acceleration or suppression are essentially different. When the coal dust is spread in the tube, the flame transient temperature curves at test points take on obvious twin-peak structural waves and the reaction zones widen. It reveals that the methane-coal dust composite flame is formed between the reactive coal dust and the methane. When the rock dust is spread in the tube, the transient temperatures at test points all decrease, and the temperature half-peak widths narrow. It can explain that spreading rock powder in coal mine laneways can prevent or mitigate the methane-coal dust explosion hazards to a certain extent.
2013, 33(4): 363-368.
doi: 10.11883/1001-1455(2013)04-0363-06
Abstract:
An experimental device was established and it included a test pipeline with 89-mm diameter, 4.5-mm wall thickness and 300-mm length. By choosing the stoichiometric premixed C2H2-air gas as the objective, the established device was used to experimentally explore the suppression effect of the premixed gas flame propagation and explosion overpressure by the different-length aluminum silicate wool at the different positions in the pipeline. The results demonstrate that when the length of the aluminum silicate wool surpasses the critical length for the flame speed, the aluminum silicate wool can suppress the flame speed. When the length of the aluminum silicate wool surpasses the critical length for the pressure, the aluminum silicate wool can suppress the explosion overpressure. The critical length of the aluminum silicate wool for the flame speed is related to the flame speed at the inlet, whereas the critical length of the aluminum silicate wool for the explosion overpressure is relevant to the explosion overpressure at the inlet. The critical length for the pressure is smaller than that for the flame speed. It can display that the aluminum silicate wool can suppress the pressure waves more efficiently.
An experimental device was established and it included a test pipeline with 89-mm diameter, 4.5-mm wall thickness and 300-mm length. By choosing the stoichiometric premixed C2H2-air gas as the objective, the established device was used to experimentally explore the suppression effect of the premixed gas flame propagation and explosion overpressure by the different-length aluminum silicate wool at the different positions in the pipeline. The results demonstrate that when the length of the aluminum silicate wool surpasses the critical length for the flame speed, the aluminum silicate wool can suppress the flame speed. When the length of the aluminum silicate wool surpasses the critical length for the pressure, the aluminum silicate wool can suppress the explosion overpressure. The critical length of the aluminum silicate wool for the flame speed is related to the flame speed at the inlet, whereas the critical length of the aluminum silicate wool for the explosion overpressure is relevant to the explosion overpressure at the inlet. The critical length for the pressure is smaller than that for the flame speed. It can display that the aluminum silicate wool can suppress the pressure waves more efficiently.
2013, 33(4): 369-374.
doi: 10.11883/1001-1455(2013)04-0369-06
Abstract:
Dynamic splitting tests were carried out by using a split Hopkinson pressure bar (SHPB) for the expanded polystyrene (EPS) concrete with the different volume fractions of EPS. An empirical formula was proposed to describe the relationship between the splitting strength and the stress rate of the EPS concrete. And the proposed empirical formula can be suitable for both static and dynamic stress rates. Based on the experimental results，the parameters for the formula were fitted. The influences of the volume fraction and the bead size of EPS on the splitting strength and the dynamic increase factor of the EPS concrete were analyzed. The experimental results show that carbon fibers have obvious reinforcing effect on dynamic splitting strength，especially for the concretes with the small bead sizes of EPS. The effects of the stress rates on the dissipated energies of the specimens were discussed. It can be found that the dissipated energies of the specimens increase with the increase of the stress rates in the case of increasing the EPS volume fractions in the concrete specimens. So the EPS beads can toughen the concrete specimens and improve their energyabsorbing performances.
Dynamic splitting tests were carried out by using a split Hopkinson pressure bar (SHPB) for the expanded polystyrene (EPS) concrete with the different volume fractions of EPS. An empirical formula was proposed to describe the relationship between the splitting strength and the stress rate of the EPS concrete. And the proposed empirical formula can be suitable for both static and dynamic stress rates. Based on the experimental results，the parameters for the formula were fitted. The influences of the volume fraction and the bead size of EPS on the splitting strength and the dynamic increase factor of the EPS concrete were analyzed. The experimental results show that carbon fibers have obvious reinforcing effect on dynamic splitting strength，especially for the concretes with the small bead sizes of EPS. The effects of the stress rates on the dissipated energies of the specimens were discussed. It can be found that the dissipated energies of the specimens increase with the increase of the stress rates in the case of increasing the EPS volume fractions in the concrete specimens. So the EPS beads can toughen the concrete specimens and improve their energyabsorbing performances.
2013, 33(4): 375-380.
doi: 10.11883/1001-1455(2013)04-0375-06
Abstract:
To explore the influences on quasistatic pressure by the chemical reactions between explosion products and oxygen in constraint space after explosions, based on the energy conservation and ideal gas state equations, a formula was proposed to calculate the quasistatic pressures after explosion in constraint space by making the isobaric assumption in the detonation product expansion process. And the following analyses were carried out for the relation of the quasistatic pressure in constraint space with the chemical reactions undergone by the explosion products of TNT. The results show that for the different explosive massvolume ratios, the calculated quasistatic pressures are in good agreement with the existent experimental data. This investigation can be applied to other explosives.
To explore the influences on quasistatic pressure by the chemical reactions between explosion products and oxygen in constraint space after explosions, based on the energy conservation and ideal gas state equations, a formula was proposed to calculate the quasistatic pressures after explosion in constraint space by making the isobaric assumption in the detonation product expansion process. And the following analyses were carried out for the relation of the quasistatic pressure in constraint space with the chemical reactions undergone by the explosion products of TNT. The results show that for the different explosive massvolume ratios, the calculated quasistatic pressures are in good agreement with the existent experimental data. This investigation can be applied to other explosives.
2013, 33(4): 381-386.
doi: 10.11883/1001-1455(2013)04-0381-06
Abstract:
Charpy pendulum impact tests were carried out on S30408 austenitic stainless steel base and weld metals at -196 ℃. The modified compliance changing rate method was used to obtain the crack initiation point of the base metal specimen. The analyses show that the results obtained by the improved method are more accurate than those by the traditional compliance changing rate method. Based on the experimental loaddisplacement curves, the Schindler procedure and key curve method were combined to achieve the dynamic crack growth resistance curve of the base metal. According to the loaddisplacement curves of the weld metal and its fracture characteristics, the dynamic fracture toughness of the weld metal was calculated by the linear elastic fracture mechanics approach.
Charpy pendulum impact tests were carried out on S30408 austenitic stainless steel base and weld metals at -196 ℃. The modified compliance changing rate method was used to obtain the crack initiation point of the base metal specimen. The analyses show that the results obtained by the improved method are more accurate than those by the traditional compliance changing rate method. Based on the experimental loaddisplacement curves, the Schindler procedure and key curve method were combined to achieve the dynamic crack growth resistance curve of the base metal. According to the loaddisplacement curves of the weld metal and its fracture characteristics, the dynamic fracture toughness of the weld metal was calculated by the linear elastic fracture mechanics approach.
2013, 33(4): 387-393.
doi: 10.11883/1001-1455(2013)04-0387-07
Abstract:
Based on the research about the flying-plate motion features of the single-layer explosive reactive armor, those of the double-layer explosive reactive armor were systematically analyzed and a model was developed to describe the flyingplate motion features of the double-layer wedged explosive reactive armor. By applying the developed model, the flying-plate motion features of single-layer, double parallel and double-layer wedged explosive reactive armors were theoretically explored and the corresponding action times of the applied fields were calculated, respectively. And the calculated results were verified by flash X-ray tests. The calculated results are in agreement with the experimental results. The applied field action time of the double-parallel explosive reactive armor is five times longer than that of the single-layer explosive reactive armor. And the applied field action time of the double-layer wedged explosive reactive armor is 38 percent longer than that of the double-parallel explosive reactive armor.
Based on the research about the flying-plate motion features of the single-layer explosive reactive armor, those of the double-layer explosive reactive armor were systematically analyzed and a model was developed to describe the flyingplate motion features of the double-layer wedged explosive reactive armor. By applying the developed model, the flying-plate motion features of single-layer, double parallel and double-layer wedged explosive reactive armors were theoretically explored and the corresponding action times of the applied fields were calculated, respectively. And the calculated results were verified by flash X-ray tests. The calculated results are in agreement with the experimental results. The applied field action time of the double-parallel explosive reactive armor is five times longer than that of the single-layer explosive reactive armor. And the applied field action time of the double-layer wedged explosive reactive armor is 38 percent longer than that of the double-parallel explosive reactive armor.
2013, 33(4): 394-400.
doi: 10.11883/1001-1455(2013)04-0394-07
Abstract:
A cook-off simulation model for composite charge (interior JO-9159/exterior JB-9014) was established to investigate the characteristics of explosive thermal reaction at different heating rates. The thermal responses of the composite charges with different structures were calculated by the finite element program LS-DYNA3D. The simulation results were verified by the experiments. Based on the available model, the calculations were conducted to simulate the cook-off tests for the composite charges at heating rates of 5 K/h, 3 K/min and 10 K/min. The results show that the heating rate and charge structure have great effect on the ignition time and position for the composite charge explosive. The ignition time decreases and the ignition position moves from the center to the two ends of the cylinder edge with the increase of the heating rate. The thermal stability depends on the interior high explosive when the heating rate is relatively low. The thermal stability is similar to the single insensitive explosive when the heating rate is relatively high. Therefore, only at higher heating rate, this kind of composite charge structure can improve the explosive power and thermal stability.
A cook-off simulation model for composite charge (interior JO-9159/exterior JB-9014) was established to investigate the characteristics of explosive thermal reaction at different heating rates. The thermal responses of the composite charges with different structures were calculated by the finite element program LS-DYNA3D. The simulation results were verified by the experiments. Based on the available model, the calculations were conducted to simulate the cook-off tests for the composite charges at heating rates of 5 K/h, 3 K/min and 10 K/min. The results show that the heating rate and charge structure have great effect on the ignition time and position for the composite charge explosive. The ignition time decreases and the ignition position moves from the center to the two ends of the cylinder edge with the increase of the heating rate. The thermal stability depends on the interior high explosive when the heating rate is relatively low. The thermal stability is similar to the single insensitive explosive when the heating rate is relatively high. Therefore, only at higher heating rate, this kind of composite charge structure can improve the explosive power and thermal stability.
2013, 33(4): 401-407.
doi: 10.11883/1001-1455(2013)04-0401-07
Abstract:
To explore the spallation in ceramic impacted by an aluminum flyer, the modified SPH method was used to simulate the stress wave propagation in ceramic. The results show that the simulated free-surface velocity histories are in agreement with the experimental ones when the discrete particles are distributed non-uniformly. The precision of the results by the modified SPH method is higher than that by CSPM. And a damage evolution equation for ceramic was proposed to numerically simulate the spallation process of laminated ceramic-steel armor plates under pulse loading. The results display that the wave impedance in ceramic is much higher than that in steel and the spallation induced by tension stress is primary. Even though an elastic compression wave propagates in ceramic, the unloading wave reflected by the ceramic-steel interface can also lead to ceramic spallation.
To explore the spallation in ceramic impacted by an aluminum flyer, the modified SPH method was used to simulate the stress wave propagation in ceramic. The results show that the simulated free-surface velocity histories are in agreement with the experimental ones when the discrete particles are distributed non-uniformly. The precision of the results by the modified SPH method is higher than that by CSPM. And a damage evolution equation for ceramic was proposed to numerically simulate the spallation process of laminated ceramic-steel armor plates under pulse loading. The results display that the wave impedance in ceramic is much higher than that in steel and the spallation induced by tension stress is primary. Even though an elastic compression wave propagates in ceramic, the unloading wave reflected by the ceramic-steel interface can also lead to ceramic spallation.
2013, 33(4): 408-414.
doi: 10.11883/1001-1455(2013)04-0408-07
Abstract:
The current major simulation methods for building structure collapse were summarized and these methods were grouped under four heads: pre-specified damage and failure criteria, implicit finite element method, explicit finite element method and discrete element method. The corresponding development histories were introduced, respectively. And the defects and problems were discussed which appearing in the building simulation by these methods. Based on the basic principle and characteristic of the discrete element method for particle materials, its advantages were analyzed in the simulation of structure collapse. Then by taking a 3-span, 10-floor senior frame structure under horizontal strong impact as an example, a program based on PFC2D was written and a particle flow model was developed to simulate the whole dynamic process from structural member cracking, fracture and failure to part collapse of structure and whole collapse. In the end, the directions and problems to the further study were brought forward.
The current major simulation methods for building structure collapse were summarized and these methods were grouped under four heads: pre-specified damage and failure criteria, implicit finite element method, explicit finite element method and discrete element method. The corresponding development histories were introduced, respectively. And the defects and problems were discussed which appearing in the building simulation by these methods. Based on the basic principle and characteristic of the discrete element method for particle materials, its advantages were analyzed in the simulation of structure collapse. Then by taking a 3-span, 10-floor senior frame structure under horizontal strong impact as an example, a program based on PFC2D was written and a particle flow model was developed to simulate the whole dynamic process from structural member cracking, fracture and failure to part collapse of structure and whole collapse. In the end, the directions and problems to the further study were brought forward.
2013, 33(4): 415-419.
doi: 10.11883/1001-1455(2013)04-0415-05
Abstract:
Based on the theoretical analyses, a set of experimental equipment, which consisting of a 20-litre closed spherical container, a gas distribution system, an ignition system, a heating system and a data acquisition system, was adopted to experimentally investigate the effects of the different environmental temperatures on the gas explosion pressure and the maximum pressure rise rate. The experimental results show that when the other conditions remain unchangeable, the maximum explosion pressure gradually decreases with the increase of the environmental temperature and its attenuation is linear with the reciprocal of the environmental temperature. With the increase of the environmental temperature, the chemical reaction rate quickens, and the time that the explosion pressure reaches its peak shortens. The maximum pressure rise rate of the gas explosion is nonlinear with the increase of the environmental temperature, but it basically remains unchanged in the 298-473 K environmental temperature range.
Based on the theoretical analyses, a set of experimental equipment, which consisting of a 20-litre closed spherical container, a gas distribution system, an ignition system, a heating system and a data acquisition system, was adopted to experimentally investigate the effects of the different environmental temperatures on the gas explosion pressure and the maximum pressure rise rate. The experimental results show that when the other conditions remain unchangeable, the maximum explosion pressure gradually decreases with the increase of the environmental temperature and its attenuation is linear with the reciprocal of the environmental temperature. With the increase of the environmental temperature, the chemical reaction rate quickens, and the time that the explosion pressure reaches its peak shortens. The maximum pressure rise rate of the gas explosion is nonlinear with the increase of the environmental temperature, but it basically remains unchanged in the 298-473 K environmental temperature range.
2013, 33(4): 420-424.
doi: 10.11883/1001-1455(2013)04-0420-05
Abstract:
A high-resolution computational framework is established to solve the shaped charge jet. An expression which can be used in the Eulerian code, considering temperature rises caused by both shock waves and plastic work, is proposed. The selfdeveloped code is validated by a benchmark test, which is the detonation of a TNT slab. The numerical simulations of shaped charge jets are carried out. The processes of the explosive detonation, the collapse of the liner and the formation of the jet are numerically simulated. The influences of the liner configurations on the jet shape, velocity and temperature are analyzed. It is found that the jet is shorter and has lower velocity with a larger apex angle, but more liner material becomes jet. During the initial stage of the explosive loading, the smaller the apex angle, the higher the liner temperature. After the jets are formed, the temperatures of the jets with different liner shapes are close to each other.
A high-resolution computational framework is established to solve the shaped charge jet. An expression which can be used in the Eulerian code, considering temperature rises caused by both shock waves and plastic work, is proposed. The selfdeveloped code is validated by a benchmark test, which is the detonation of a TNT slab. The numerical simulations of shaped charge jets are carried out. The processes of the explosive detonation, the collapse of the liner and the formation of the jet are numerically simulated. The influences of the liner configurations on the jet shape, velocity and temperature are analyzed. It is found that the jet is shorter and has lower velocity with a larger apex angle, but more liner material becomes jet. During the initial stage of the explosive loading, the smaller the apex angle, the higher the liner temperature. After the jets are formed, the temperatures of the jets with different liner shapes are close to each other.
2013, 33(4): 425-429.
doi: 10.11883/1001-1455(2013)04-0425-05
Abstract:
The AUTODYN-2D hydrocode was applied to numerically simulate the penetration process of the 1.6-m-diameter cylindrical concrete target with the length of 2 m by a 3.0-caliber-radius-head, ogive-nose projectile with the diameter of 75 mm and the length of 225 mm. And the Lagrangian elements were used to describe the projectile and target. The hydro and principal stress tensile failure modes were adopted to analyze the influences of the different mesh sizes of the concrete target and the different erosion criterions of the concrete finite elements on the penetration depth and frontface crater. The results indicate that the above three factors all evidently influence the simulated results. The simulated results are reasonable when the size of the concrete target elements is 5.0 mm. For the two failure modes, when the erosion strain is set at 1.5, the simulated results are close to the experiments. And for the hydro tensile failure mode, when the erosion strain is set at 2.0, the simulated results are in good agreement with the experiments.
The AUTODYN-2D hydrocode was applied to numerically simulate the penetration process of the 1.6-m-diameter cylindrical concrete target with the length of 2 m by a 3.0-caliber-radius-head, ogive-nose projectile with the diameter of 75 mm and the length of 225 mm. And the Lagrangian elements were used to describe the projectile and target. The hydro and principal stress tensile failure modes were adopted to analyze the influences of the different mesh sizes of the concrete target and the different erosion criterions of the concrete finite elements on the penetration depth and frontface crater. The results indicate that the above three factors all evidently influence the simulated results. The simulated results are reasonable when the size of the concrete target elements is 5.0 mm. For the two failure modes, when the erosion strain is set at 1.5, the simulated results are close to the experiments. And for the hydro tensile failure mode, when the erosion strain is set at 2.0, the simulated results are in good agreement with the experiments.
2013, 33(4): 430-437.
doi: 10.11883/1001-1455(2013)04-0430-08
Abstract:
Flame distortion induced by shock waves frequently occurs in natural and man-made phenomena. To deeply understand the characteristics of flame distortion and the resulting variations of mixing and combustion, a two-dimensional numerical study of a spherical flame distortion induced by a planar incident shock wave and its reflected wave was carried out by using the Navier-Stokes equations coupled with a single-step chemical reaction and the high resolution of grid. The numerical results are in agreement with the experimental results. It can be found that before the interaction of reflected shock wave with flame, the distortion and crinkle of flame are mainly affected by the induction of incident shock wave, which means the physical process plays an important role; while after the interaction between reflected shock wave and distorted flame, the reaction heat release rate and the effective area and edge length of flame increase quickly, the controlling mechanism of flame distortion is transforming from the physical process to the chemical reaction (combustion) process; in the later stage of the evolution of distorted flame, enhanced combustion can weaken the crinkle of flame interface, and therefore inhibit the mixing process between unburned and burned gases. It is concluded that the mixing between unburned gas and burned gas is promoted via the distortion of flame, which can strengthen the combustion process, however, the enhanced combustion inhibits the mixing in the later stage. It is significant for understanding the relationship between mixing and combustion in using or controlling the shock-flame interactions.
Flame distortion induced by shock waves frequently occurs in natural and man-made phenomena. To deeply understand the characteristics of flame distortion and the resulting variations of mixing and combustion, a two-dimensional numerical study of a spherical flame distortion induced by a planar incident shock wave and its reflected wave was carried out by using the Navier-Stokes equations coupled with a single-step chemical reaction and the high resolution of grid. The numerical results are in agreement with the experimental results. It can be found that before the interaction of reflected shock wave with flame, the distortion and crinkle of flame are mainly affected by the induction of incident shock wave, which means the physical process plays an important role; while after the interaction between reflected shock wave and distorted flame, the reaction heat release rate and the effective area and edge length of flame increase quickly, the controlling mechanism of flame distortion is transforming from the physical process to the chemical reaction (combustion) process; in the later stage of the evolution of distorted flame, enhanced combustion can weaken the crinkle of flame interface, and therefore inhibit the mixing process between unburned and burned gases. It is concluded that the mixing between unburned gas and burned gas is promoted via the distortion of flame, which can strengthen the combustion process, however, the enhanced combustion inhibits the mixing in the later stage. It is significant for understanding the relationship between mixing and combustion in using or controlling the shock-flame interactions.
2013, 33(4): 438-443.
doi: 10.11883/1001-1455(2013)04-0438-06
Abstract:
The tensile plasticity flow properties of high-strength structural steel DH36 were systematically studied at the temperature range from 293 to 800 K and the strain-rate range from 0.001 to 0.1 s-1 by using a quasi-static testing machine. And the high-strength structural steel DH36 underwent the strain over 25%. Then, the microstructures of the DH36 samples were analyzed by applying the scanning electron microscopy before and after deformation. The experimental results show that the third-type dynamic strain-aging (SA) phenomenon disappears in the test temperature range at the strain rates of 0.001 and 0.1 s-1, and the SA temperature rises with the increase of strain rate. And the disappearance of the third-type dynamic (SA) phenomenon is relevant to the precipitation strengthening of the alloy metals at grain boundaries and in grains. Finally, through systematically analysing the test data, a uniform constitutive model including the third type SA effects was built for DH36 steel. The results predicted by the built model are in agreement with the test data. It displays the built model can well predicate the plastic flow stresses of DH36 steel in the wide ranges of temperatures and strain rates.
The tensile plasticity flow properties of high-strength structural steel DH36 were systematically studied at the temperature range from 293 to 800 K and the strain-rate range from 0.001 to 0.1 s-1 by using a quasi-static testing machine. And the high-strength structural steel DH36 underwent the strain over 25%. Then, the microstructures of the DH36 samples were analyzed by applying the scanning electron microscopy before and after deformation. The experimental results show that the third-type dynamic strain-aging (SA) phenomenon disappears in the test temperature range at the strain rates of 0.001 and 0.1 s-1, and the SA temperature rises with the increase of strain rate. And the disappearance of the third-type dynamic (SA) phenomenon is relevant to the precipitation strengthening of the alloy metals at grain boundaries and in grains. Finally, through systematically analysing the test data, a uniform constitutive model including the third type SA effects was built for DH36 steel. The results predicted by the built model are in agreement with the test data. It displays the built model can well predicate the plastic flow stresses of DH36 steel in the wide ranges of temperatures and strain rates.
2013, 33(4): 444-448.
doi: 10.11883/1001-1455(2013)04-0444-05
Abstract:
A central igniter tube was designed according to engineering requirements and firing tests were completed. By considering the large length-to-diameter ratio and consolidated charge of the designed igniter tube, a one-dimensional, two-phase flow model was developed to numerically simulate the combustion process of the gas-solid two-phase flow. The simulated results are consistent with the measured ones. So the developed two-phase flow model can correctly describe the actual physical process and the parameters used in the program are reasonable. The calculation program can provide a theoretical guidance for the ignition performance analysis and optimal design of the igniter tube in different construction measurements and charge conditions. The ignition performances of the igniter tube were also analyzed on the basis of the computational results, which providing reference for the optimal design in further work.
A central igniter tube was designed according to engineering requirements and firing tests were completed. By considering the large length-to-diameter ratio and consolidated charge of the designed igniter tube, a one-dimensional, two-phase flow model was developed to numerically simulate the combustion process of the gas-solid two-phase flow. The simulated results are consistent with the measured ones. So the developed two-phase flow model can correctly describe the actual physical process and the parameters used in the program are reasonable. The calculation program can provide a theoretical guidance for the ignition performance analysis and optimal design of the igniter tube in different construction measurements and charge conditions. The ignition performances of the igniter tube were also analyzed on the basis of the computational results, which providing reference for the optimal design in further work.
