In this paper, under-expanded impinging jets issued from converging circular and rectangular nozzles were investigated. The ratio of the distance between the nozzle exit and the plate L to the diameter D was set at 2,...In this paper, under-expanded impinging jets issued from converging circular and rectangular nozzles were investigated. The ratio of the distance between the nozzle exit and the plate L to the diameter D was set at 2, 3, 4 for the circular nozzle and 2, 3 for the rectangular nozzle. Two-dimensional temperature and static pressure distributions on the impinging plate were measured using an infrared camera and a semi-conductor pressure sensor and flow fields were visualized by means of schlieren method. Three-dimensional numerical calculations were also conducted by solving the three-dimensional compressible Euler equations and compared to the experimental results. As a result, it is found that the numerical calculations for the circular and the rectangular nozzles are in good agreement with the experiments. In the experiments, it is found that the stagnation temperature on the plate depends on the pressure in the settling chamber and the distance between the nozzle exit and the plate. The temperature and pressure distributions in the experiments illustrate that even in the case of the circular nozzle, the distributions on the impinging plate are non-axisymmetric, which is confirmed by the three dimensional calculations. The calculation for the rectangular nozzle indicates that two circulating regions occur immediately upstream of the plate.展开更多
The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the t...The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the two-dimensional temperature distribution on an inclined plate surface and the relation between the temperature distribution and some shock waves formed in the flow field. In this study, the measurement of temperature distribution on an inclined plate surface and the now visualization has carried out for various conditions using the thermo-sensitive liquid crystal sheet and the schlieren method. The two dimensional temperature distribution on the plate surface is clearly obtained by the thermo-sensitive liquid crystal sheet. The relation between the temperature distribution on an inclined plate surface and some shock waves reached at a plate surface is discussed. In this paper, the characteristics of the temperature distribution and the maximum temperature, and some other experimental evidences are presented.展开更多
In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the mass-averaged implicit Navier-Stokes equations ...In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the mass-averaged implicit Navier-Stokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.5 to 20.0. The standard k- ε turbulence model was employed to close the governing equations. Numerical calculations were carried out for some combinations of the multiple orifice configurations. The present CFD data showed that the orifice systems, which have been applied to incompressible flow regime to date, could not be used for the high operating pressure ratio flows. The orifice interval did not strongly affect the total pressure drop, but the orifice area ratio more than 2.5 led to relatively high pressure drops. The total pressure drop rapidly increased in the range of the operating pressure ratio from 1.5 to 4.0, but it nearly did not increase when the operating pressure ratio was over 4.0. In the compressible pipe flows through double and triple orifice systems, the total pressure drop was largely due to shock losses.展开更多
The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ide...The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ideal gas law However, when the critical nozzle measures the mass flow rate of a real gas such as hydrogen at a pressure of hundreds bar, the discharge coefficient exceeds unity, and the real gas effects should be taken into account. The present study aims at investigating the flow features of the critical nozzle using high-pressured hydrogen gas. The axisymmetric, compressible Navier-Stokes computation is employed to simulate the critical nozzle flow, and a fully implicit finite volume method is used to discretize the governing equation system. The real gas effects are simulated to consider the intermolecular forces, which account for the possibility of liquefying hydrogen gas. The computational results are compared with past experimental data. It has been found that the coefficient of discharge for real gas can be corrected properly below unity adopting the real gas assumption.展开更多
文摘In this paper, under-expanded impinging jets issued from converging circular and rectangular nozzles were investigated. The ratio of the distance between the nozzle exit and the plate L to the diameter D was set at 2, 3, 4 for the circular nozzle and 2, 3 for the rectangular nozzle. Two-dimensional temperature and static pressure distributions on the impinging plate were measured using an infrared camera and a semi-conductor pressure sensor and flow fields were visualized by means of schlieren method. Three-dimensional numerical calculations were also conducted by solving the three-dimensional compressible Euler equations and compared to the experimental results. As a result, it is found that the numerical calculations for the circular and the rectangular nozzles are in good agreement with the experiments. In the experiments, it is found that the stagnation temperature on the plate depends on the pressure in the settling chamber and the distance between the nozzle exit and the plate. The temperature and pressure distributions in the experiments illustrate that even in the case of the circular nozzle, the distributions on the impinging plate are non-axisymmetric, which is confirmed by the three dimensional calculations. The calculation for the rectangular nozzle indicates that two circulating regions occur immediately upstream of the plate.
文摘The Phenomena of the interaction between a supersonic jet and an obstacle is a very interesting and important problem relating to the industrial engineering. This paper aims to investigate the characteristics of the two-dimensional temperature distribution on an inclined plate surface and the relation between the temperature distribution and some shock waves formed in the flow field. In this study, the measurement of temperature distribution on an inclined plate surface and the now visualization has carried out for various conditions using the thermo-sensitive liquid crystal sheet and the schlieren method. The two dimensional temperature distribution on the plate surface is clearly obtained by the thermo-sensitive liquid crystal sheet. The relation between the temperature distribution on an inclined plate surface and some shock waves reached at a plate surface is discussed. In this paper, the characteristics of the temperature distribution and the maximum temperature, and some other experimental evidences are presented.
文摘In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the mass-averaged implicit Navier-Stokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.5 to 20.0. The standard k- ε turbulence model was employed to close the governing equations. Numerical calculations were carried out for some combinations of the multiple orifice configurations. The present CFD data showed that the orifice systems, which have been applied to incompressible flow regime to date, could not be used for the high operating pressure ratio flows. The orifice interval did not strongly affect the total pressure drop, but the orifice area ratio more than 2.5 led to relatively high pressure drops. The total pressure drop rapidly increased in the range of the operating pressure ratio from 1.5 to 4.0, but it nearly did not increase when the operating pressure ratio was over 4.0. In the compressible pipe flows through double and triple orifice systems, the total pressure drop was largely due to shock losses.
文摘The mass flow rate measurement using a critical nozzle shows the validity of the inviscid theory, indicating that the discharge coefficient increases and approaches unity as the Reynolds number increases under the ideal gas law However, when the critical nozzle measures the mass flow rate of a real gas such as hydrogen at a pressure of hundreds bar, the discharge coefficient exceeds unity, and the real gas effects should be taken into account. The present study aims at investigating the flow features of the critical nozzle using high-pressured hydrogen gas. The axisymmetric, compressible Navier-Stokes computation is employed to simulate the critical nozzle flow, and a fully implicit finite volume method is used to discretize the governing equation system. The real gas effects are simulated to consider the intermolecular forces, which account for the possibility of liquefying hydrogen gas. The computational results are compared with past experimental data. It has been found that the coefficient of discharge for real gas can be corrected properly below unity adopting the real gas assumption.
