The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning cal...The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.展开更多
In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volu...In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.展开更多
Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operat...Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operating conditions such as bleeding.This eventually determines the operation and cost efficiency of the borehole heat exchanger system.The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding.For this,a thermal response test rig was established with line-source theory.The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger.The thermal response test was performed with an additional constant input heat source.Effective thermal conductivity and thermal resistance were obtained from the measured data.From the measurement,the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied.The thermal resistance also increases by 1.58 times compared to a non-bleeding case.This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function.Bleeding,therefore,could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.展开更多
Bronchogenic cyst occurring in the diaphragm is rare and thoracoscopic cyst resection is mainly effective treatment. The coronary artery bleeding after video-assisted thoracoscopic surgery(VATS) has never been describ...Bronchogenic cyst occurring in the diaphragm is rare and thoracoscopic cyst resection is mainly effective treatment. The coronary artery bleeding after video-assisted thoracoscopic surgery(VATS) has never been described; here we report a case of left coronary artery injury after thoracoscopic itradiaphragmatic bronchogenic cyst resection, which may be caused by metallic troca or chest tube.展开更多
A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-s...A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-sustained decomposition.Due to the low temperature near the burning surface,the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs,and a partly pre-mixed diffusion flame structure-leading edge flame(LEF)is formed.The effects of pressure,chemical reaction rate and AP particle size on diffusion flame structure in the range from 20 atm to 100 atm are discussed.The Peclet number increases from 6.64 at 20 atm to 21.91 at 100 atm when AP particle size is 140 mm.The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number.The chemical reaction rate is enhanced and the diffusion mixing is inhibited as Damkohler number increases.The chemical heat release is more concentrated and the chemical reaction zone becomes narrow when Damkohler number changes from 330 at20 atm to 4700 at 100 atm.When AP particle diameter is decreased to 60 mm,the diffusion time scale is reduced due to the reduced diffusion length scale.So the diffusion mixing is enhanced and a more pre-mixed flame is formed.The burning rate increases because the more pre-mixed heat release increases the heat feedback to the HTPB binder.展开更多
文摘The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.
基金supported by National Nature Science Foundation of China(Grant No.51176076)
文摘In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.
基金Project supported by the Second Stage of Brain Korea 21 Projects and Changwon National University in2011-2012
文摘Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy.The thermal performance is affected by many different design parameters and different operating conditions such as bleeding.This eventually determines the operation and cost efficiency of the borehole heat exchanger system.The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding.For this,a thermal response test rig was established with line-source theory.The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger.The thermal response test was performed with an additional constant input heat source.Effective thermal conductivity and thermal resistance were obtained from the measured data.From the measurement,the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied.The thermal resistance also increases by 1.58 times compared to a non-bleeding case.This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function.Bleeding,therefore,could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.
文摘Bronchogenic cyst occurring in the diaphragm is rare and thoracoscopic cyst resection is mainly effective treatment. The coronary artery bleeding after video-assisted thoracoscopic surgery(VATS) has never been described; here we report a case of left coronary artery injury after thoracoscopic itradiaphragmatic bronchogenic cyst resection, which may be caused by metallic troca or chest tube.
基金the financial support provided by the National Natural Science Foundation of China(No.51176076)
文摘A complex multiple flame structure is formed during the combustion of AP/HTPB base bleed propellant.The AP monopropellant flame is concentrated in a thin zone above the burning surface of AP crystal to maintain self-sustained decomposition.Due to the low temperature near the burning surface,the diffusion between the decomposition products of AP and the pyrolysis products of HTPB occurs,and a partly pre-mixed diffusion flame structure-leading edge flame(LEF)is formed.The effects of pressure,chemical reaction rate and AP particle size on diffusion flame structure in the range from 20 atm to 100 atm are discussed.The Peclet number increases from 6.64 at 20 atm to 21.91 at 100 atm when AP particle size is 140 mm.The high temperature zone is blown away from the burning surface because the convective transport rate increases with the increase in Peclet number.The chemical reaction rate is enhanced and the diffusion mixing is inhibited as Damkohler number increases.The chemical heat release is more concentrated and the chemical reaction zone becomes narrow when Damkohler number changes from 330 at20 atm to 4700 at 100 atm.When AP particle diameter is decreased to 60 mm,the diffusion time scale is reduced due to the reduced diffusion length scale.So the diffusion mixing is enhanced and a more pre-mixed flame is formed.The burning rate increases because the more pre-mixed heat release increases the heat feedback to the HTPB binder.
