In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is pr...In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation（FFT）, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal（1L） acoustic mode can be excited easily and is hard to be damped. The axial position of the central constantvolume bomb has little influence on the amplitude and damping capacity of the First Radial（1R） and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential（1T） mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber.展开更多
Constant-volume heat capacities of supercritical (SC) CO2, SC CO2-n-pentane, and SC CO2-n-heptane mixtures were determined at 308.15 K in the pressure range from 6 to 12 MPa. It was found that there is a maximum in ea...Constant-volume heat capacities of supercritical (SC) CO2, SC CO2-n-pentane, and SC CO2-n-heptane mixtures were determined at 308.15 K in the pressure range from 6 to 12 MPa. It was found that there is a maximum in each heat capacity vs pressure curve. Intermolecular interaction in the fluids was studied.展开更多
Laminar flame speed is one of the most important intrinsic properties of a combustible mixture. Due to its importance, different methods have been developed to measure the laminar flame speed. This paper reviews the c...Laminar flame speed is one of the most important intrinsic properties of a combustible mixture. Due to its importance, different methods have been developed to measure the laminar flame speed. This paper reviews the constant-volume propagating spherical flame method for laminar flame speed measurement. This method can be used to measure laminar flame speed at high pressures and temperatures which are close to engine-relevant conditions. First, the propagating spherical flame method is introduced and the constant-volume method （CVM） and constant- pressure method （CPM） are compared. Then, main groups using the constant-volume propagating spherical flame method are introduced and large discrepancies in laminar flame speeds measured by different groups for the same mixture are identified. The sources of discrepancies in laminar flame speed measured by CVM are discussed and special attention is devoted to the error encountered in data processing. Different correlations among burned mass fraction, pressure, temperature and flame speed, which are used by different researchers to obtain laminar flame speed, are summarized. The performance of these correlations are examined, based on which recommendations are given. Finally, recommendations for future studies on the con- stant-volume propagating spherical flame method for laminar flame speed measurement are presented.展开更多
Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamat...Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline·H_2O (o-phen·H_2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE^(3+) coordinated with six sulfur atoms of three PDC^- and two nitrogen atoms of o-phen·H_2O. It was assumed that the coordination number of RE^(3+) is eight. The constant-volume combustion energies of the complexes, Δ_cU, were determined as (-16937 88±9 79 ), (-17588 79±8 62 ), ((-17747 14±)8 25 ) and (-17840 37±8 87 ) kJ·mol^(-1), by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, Δ_cH~θ_m, and standard molar enthalpies of formation, Δ_fH~θ_m, were calculated as (-16953 37±9 79), (-17604 28±8 62), (-17762 63±8 25), (-17855 86±8 87) kJ·mol^(-1) and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ·mol^(-1).展开更多
The ternary solid complex was synthesized with sodium diethyldithiocarbamate (NaEt_2dtc), 1,10-phenanthroline (phen) and low hydrated dysprosium chloride in absolute ethanol by improved method of reference. The title ...The ternary solid complex was synthesized with sodium diethyldithiocarbamate (NaEt_2dtc), 1,10-phenanthroline (phen) and low hydrated dysprosium chloride in absolute ethanol by improved method of reference. The title complex was identified as the general formula of Dy(Et_2dtc)_3(phen) by chemical and elemental analyses. IR spectrum of the complex shows that the Dy^(3+) coordinated with six sulfur atoms of three NaEt_2dtc and two nitrogen atoms of phen. It is assumed that the coordination number of Dy^(3+) is eight.The enthalpy change of liquid-phase reaction of formation, Δ_rH~θ_m(l), is determined as (-19.091±0.015) kJ·mol^(-1) at 298.15 K by a microcalorimeter, and the enthalpy change of the solid-phase reaction of formation, Δ_rH~θ_m(s), is calculated as (139.641±0.482) kJ·mol^(-1) on the basis of a thermochemical cycle. The thermodynamic of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex, Δ_cU, is determined as (-16730.21±9.25) kJ·mol^(-1) by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpies of combustion, Δ_cH~θ_m, and standard enthalpies of formation, Δ_fH~θ_m, are calculated as (-16749.42±9.25) kJ·mol^(-1) and (-2019.68±10.19) kJ·mol^(-1), respectively.展开更多
This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid ...This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.展开更多
The ternary solid complex has been synthesized with sodium diethyldithiocarbamate (NaEt2dtc?3H2O), 1,10-phenanthroline (o-phen?H2O) and hydrated neodymium chloride in absolute ethanol. The title complex was identifi...The ternary solid complex has been synthesized with sodium diethyldithiocarbamate (NaEt2dtc?3H2O), 1,10-phenanthroline (o-phen?H2O) and hydrated neodymium chloride in absolute ethanol. The title complex was identified as the general formula of Nd(Et2dtc)3(phen) by chemical and elemental analyses. IR spectrum of the complex showed that the Nd3+ coordinated with six sulfur atoms of three NaEt2dtc and two nitrogen atoms of o-phen. It was assumed that the coordination number of Nd3+ is eight.The enthalpy change of liquid-phase reaction of formation, ?rHm (l), was determined as (-12.274±0.050) kJ?mol-1 at 298.15 K by a microcalorimeter, the Θ enthalpy change of the solid-phase reaction of formation, ?rHm (s), was calculated as (149.069±0.314) kJ?mol-1 Θ on the basis of a thermochemical cycle. The thermodynamics of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex, ?cU , was deter- mined as (-18674.22±8.33) kJ?mol-1 by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, ?cHm , and standard enthalpy of formation, ?fHm , were calculated as (-18693.43±8.33) kJ?mol-1 Θ Θ and (-47.03±9.17) kJ?mol-1, respectively.展开更多
In this paper,we design a hydrostatic electroactive soft actuator(HESA)inspired by octopus transverse musculature.We introduce the advantage of laser processing technology in HESA fabrication compared with existing si...In this paper,we design a hydrostatic electroactive soft actuator(HESA)inspired by octopus transverse musculature.We introduce the advantage of laser processing technology in HESA fabrication compared with existing similar actuators and discuss the effect of laser processing on the outer membrane of the actuator.In addition,a mathematical model is established for the single channel of the actuator,and the geometric parameters of the actuator are optimized by mathematical model simulation and experiments.We demonstrate the motion effect of the actuator.Our experiments show that the single piece of the actuator can achieve 32.2%strain in the axial direction and 7.8%strain in the radius direction.Furthermore,we stack three actuators together and describe their motion characteristics at different frequencies.The stacked actuators can realize axial elongation,radial shrinkage,and bend,which covers all the motion modes of the octopus biological transverse musculature.This study may lay a foundation for implementing the biomimetic soft actuator mimicking the octopus’s transverse musculature,which is one less discussed but crucial muscular composition in the octopus-inspired arm research.展开更多
基金Financial support from the National Natural Science Foundation of China (Nos.51676111 and 11628206)
文摘In order to numerically evaluate the acoustic characteristics of liquid rocket engine thrust chambers by means of a computational fluid dynamics method, a mathematical model of an artificial constant-volume bomb is proposed in this paper. A localized pressure pulse with a very high amplitude can be imposed on specified regions in a combustion chamber, the numerical procedure of which is described. Pressure oscillations actuated by the released constant-volume bomb can then be analyzed via Fast Fourier Transformation（FFT）, and their modes can be identified according to the theoretical acoustic eigenfrequencies of the thrust chamber. The damping performances of the corresponding acoustic modes are evaluated by the half-power bandwidth method. The predicted acoustic characteristics and their damping for a special engine combustor agree well with the experimental data, validating the mathematical model and its numerical procedures. A small-thrust liquid rocket engine chamber is then analyzed by the present model. The First Longitudinal（1L） acoustic mode can be excited easily and is hard to be damped. The axial position of the central constantvolume bomb has little influence on the amplitude and damping capacity of the First Radial（1R） and 1L acoustic modes. Tangential acoustic modes can only be triggered by an off-centered constant-volume bomb, among which the First Tangential（1T） mode is the strongest and regarded as the most harmful one. The amplitude of the 1L acoustic mode is smaller, but its damping factor is larger, as a constant-volume bomb is imposed approaching the injector face. These results are contributed to evaluate the acoustic characteristics and their damping of the combustion chamber.
文摘Constant-volume heat capacities of supercritical (SC) CO2, SC CO2-n-pentane, and SC CO2-n-heptane mixtures were determined at 308.15 K in the pressure range from 6 to 12 MPa. It was found that there is a maximum in each heat capacity vs pressure curve. Intermolecular interaction in the fluids was studied.
基金supported by the National Natural Science Foundation of China(51322602)
文摘Laminar flame speed is one of the most important intrinsic properties of a combustible mixture. Due to its importance, different methods have been developed to measure the laminar flame speed. This paper reviews the constant-volume propagating spherical flame method for laminar flame speed measurement. This method can be used to measure laminar flame speed at high pressures and temperatures which are close to engine-relevant conditions. First, the propagating spherical flame method is introduced and the constant-volume method （CVM） and constant- pressure method （CPM） are compared. Then, main groups using the constant-volume propagating spherical flame method are introduced and large discrepancies in laminar flame speeds measured by different groups for the same mixture are identified. The sources of discrepancies in laminar flame speed measured by CVM are discussed and special attention is devoted to the error encountered in data processing. Different correlations among burned mass fraction, pressure, temperature and flame speed, which are used by different researchers to obtain laminar flame speed, are summarized. The performance of these correlations are examined, based on which recommendations are given. Finally, recommendations for future studies on the con- stant-volume propagating spherical flame method for laminar flame speed measurement are presented.
基金Project supported by the Natural Science Foundation of China (2047104) and the Natural Science Foundation of Shaanxi Province (2003B19)
文摘Four solid ternary complexes of RE (C_5H_8NS_2)_3(C_(12)H_8N_2) (RE=Eu, Gd, Tb, Dy) were synthesized in absolute ethanol by rare earth chloride low hydrate with the mixed ligands of ammonium pyrrolidinedi-thiocarbamate (APDC) and 1, 10-phenanthroline·H_2O (o-phen·H_2O) in the ordinary laboratory atmosphere without any cautions against moisture or air sensitivity. IR spectra of the complexes show that the RE^(3+) coordinated with six sulfur atoms of three PDC^- and two nitrogen atoms of o-phen·H_2O. It was assumed that the coordination number of RE^(3+) is eight. The constant-volume combustion energies of the complexes, Δ_cU, were determined as (-16937 88±9 79 ), (-17588 79±8 62 ), ((-17747 14±)8 25 ) and (-17840 37±8 87 ) kJ·mol^(-1), by a precise rotating-bomb calorimeter at 298.15 K. Its standard molar enthalpies of combustion, Δ_cH~θ_m, and standard molar enthalpies of formation, Δ_fH~θ_m, were calculated as (-16953 37±9 79), (-17604 28±8 62), (-17762 63±8 25), (-17855 86±8 87) kJ·mol^(-1) and (-857.04±10.52), (-282.43±9.58), (-130.08±9.13), (-55.75±9.83) kJ·mol^(-1).
文摘The ternary solid complex was synthesized with sodium diethyldithiocarbamate (NaEt_2dtc), 1,10-phenanthroline (phen) and low hydrated dysprosium chloride in absolute ethanol by improved method of reference. The title complex was identified as the general formula of Dy(Et_2dtc)_3(phen) by chemical and elemental analyses. IR spectrum of the complex shows that the Dy^(3+) coordinated with six sulfur atoms of three NaEt_2dtc and two nitrogen atoms of phen. It is assumed that the coordination number of Dy^(3+) is eight.The enthalpy change of liquid-phase reaction of formation, Δ_rH~θ_m(l), is determined as (-19.091±0.015) kJ·mol^(-1) at 298.15 K by a microcalorimeter, and the enthalpy change of the solid-phase reaction of formation, Δ_rH~θ_m(s), is calculated as (139.641±0.482) kJ·mol^(-1) on the basis of a thermochemical cycle. The thermodynamic of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex, Δ_cU, is determined as (-16730.21±9.25) kJ·mol^(-1) by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpies of combustion, Δ_cH~θ_m, and standard enthalpies of formation, Δ_fH~θ_m, are calculated as (-16749.42±9.25) kJ·mol^(-1) and (-2019.68±10.19) kJ·mol^(-1), respectively.
基金Project supported by the National Natural Science Foundation of China （Grant No 20673050）.
文摘This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.
基金Project supported by the National Natural Science Foundation of China (No. 20171036) Education Committee of Shaanxi Province (No. 01JK229)the National Natural Science Foundation of Shaanxi Province (No. FF02328) and National State Post Doctoral Fou
文摘The ternary solid complex has been synthesized with sodium diethyldithiocarbamate (NaEt2dtc?3H2O), 1,10-phenanthroline (o-phen?H2O) and hydrated neodymium chloride in absolute ethanol. The title complex was identified as the general formula of Nd(Et2dtc)3(phen) by chemical and elemental analyses. IR spectrum of the complex showed that the Nd3+ coordinated with six sulfur atoms of three NaEt2dtc and two nitrogen atoms of o-phen. It was assumed that the coordination number of Nd3+ is eight.The enthalpy change of liquid-phase reaction of formation, ?rHm (l), was determined as (-12.274±0.050) kJ?mol-1 at 298.15 K by a microcalorimeter, the Θ enthalpy change of the solid-phase reaction of formation, ?rHm (s), was calculated as (149.069±0.314) kJ?mol-1 Θ on the basis of a thermochemical cycle. The thermodynamics of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex, ?cU , was deter- mined as (-18674.22±8.33) kJ?mol-1 by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, ?cHm , and standard enthalpy of formation, ?fHm , were calculated as (-18693.43±8.33) kJ?mol-1 Θ Θ and (-47.03±9.17) kJ?mol-1, respectively.
基金supported by the National Natural Science Foundation of China(92048302,91848206,and T2121003)the National Key R&D Program of China(2019YFB1309600 and 2020YFB1313003).
文摘In this paper,we design a hydrostatic electroactive soft actuator(HESA)inspired by octopus transverse musculature.We introduce the advantage of laser processing technology in HESA fabrication compared with existing similar actuators and discuss the effect of laser processing on the outer membrane of the actuator.In addition,a mathematical model is established for the single channel of the actuator,and the geometric parameters of the actuator are optimized by mathematical model simulation and experiments.We demonstrate the motion effect of the actuator.Our experiments show that the single piece of the actuator can achieve 32.2%strain in the axial direction and 7.8%strain in the radius direction.Furthermore,we stack three actuators together and describe their motion characteristics at different frequencies.The stacked actuators can realize axial elongation,radial shrinkage,and bend,which covers all the motion modes of the octopus biological transverse musculature.This study may lay a foundation for implementing the biomimetic soft actuator mimicking the octopus’s transverse musculature,which is one less discussed but crucial muscular composition in the octopus-inspired arm research.
