To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. E...To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. Experiments have been conducted over a range of nozzle pressure ratios from 3.0 to 6.0. Flow field issued from the new nozzle is quantitatively visualized by the rainbow schlieren deflectometry and compared with that from a conventional nozzle. Density fields in the free jets are reconstructed by the Abel inversion method for the schlieren images with the horizontal rainbow filter. The density values at the exit of the conventional nozzle obtained by the rainbow schlieren are compared with the analytical results by the flow model proposed in the past. In addition, Pitot probe surveys along the jet centerline were made to obtain the impact pressure distributions. The Mach number and velocity distributions along the jet centerline are obtained from a combination of the density and Pitot pressure data to clarify the fundamental flow structure of leek peeler nozzle jets.展开更多
An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when th...An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when the sampling is stopped. CFD simulations using the commercial software Ansys CFX were carried out for single phase gas flow to analyze the non-standard design. Pitot tube velocity calculations and isokinetic sampling conditions were studied. The predicted results were compared against theoretical velocity profiles from the literature and with gas single phase experimental data acquired in a horizontal 49 m long steel pipeline with an internal diameter of 69 mm. The experiments were done by using a dense gas (SF6) at 7 bara. An asymmetry of the experimental velocity profiles reproduced with the numerical simulations. The CFD simulations made it possible to verify the design and predict and correct an installation problem.展开更多
Pitot probes enable a simple and convenient way of measuring mean velocity in air flow. The contrastive numerical simulation between free supersonic airflow and pitot tube at different positions in supersonic air flow...Pitot probes enable a simple and convenient way of measuring mean velocity in air flow. The contrastive numerical simulation between free supersonic airflow and pitot tube at different positions in supersonic air flow was performed using Navier-Stokes equations, the ENN scheme with time-dependent boundary conditions （TDBC） and the Spalart-Allmaras turbulence model. The physical experimental results including pitot pressure and shadowgraph are also presented. Numerical results coincide with the experimental data. The flow characteristics of the pitot probe on the supersonic flow structure show that the measure- ment gives actually the total pressure behind the detached shock wave by using the pitot probe to measure the total pressure. The measurement result of the distribution of the total pressure can still represent the real free jet flow. The similar features of the intersection and reflection of shock waves can be identified. The difference between the measurement results and the actual ones is smaller than 10%. When the pitot probe is used to measure the region of L=0-4D, the measurement is smaller than the real one due to the increase of the shock wave strength. The difference becomes larger where the waves intersect. If the pitot probe is put at L=SD-10D, where the flow changes from supersonic to subsonic, the addition of the pitot probe turns the original supersonic flow region subsonic and causes bigger measurement errors.展开更多
A conceptual coaxial Pitot tube （PT） has been developed using fiber optic sensors combined with actuators to monitor and maintain its correct operation under different environmental conditions. Experiments were perf...A conceptual coaxial Pitot tube （PT） has been developed using fiber optic sensors combined with actuators to monitor and maintain its correct operation under different environmental conditions. Experiments were performed showing that the dynamic and static tubes can be cleared of ice. It was also demonstrated that the dynamic tube could be cleared of dust and sand which was not the case for the static tube in the coaxial configuration. An approach was proposed to overcome this problem involving a conventional configuration where the static tube was operated independently orthogonal to the dynamic tube, and a second set of sensors and actuators was used. Sensors and associated actuators were developed for temperature and intensity for a linear PT. The aim of this work is to propose a solution for a problem that has caused the loss of the lives of many passengers and crew of aircraft. Resources were not available to test a full implementation of a PT incorporating the proposed modifications.展开更多
文摘To optimize the leek peeling performance, a new nozzle has been developed in which the nozzle has a design Mach number of 1.68, an inner diameter of 2.0 mm at the throat, and an inner diameter of 2.3 mm at the exit. Experiments have been conducted over a range of nozzle pressure ratios from 3.0 to 6.0. Flow field issued from the new nozzle is quantitatively visualized by the rainbow schlieren deflectometry and compared with that from a conventional nozzle. Density fields in the free jets are reconstructed by the Abel inversion method for the schlieren images with the horizontal rainbow filter. The density values at the exit of the conventional nozzle obtained by the rainbow schlieren are compared with the analytical results by the flow model proposed in the past. In addition, Pitot probe surveys along the jet centerline were made to obtain the impact pressure distributions. The Mach number and velocity distributions along the jet centerline are obtained from a combination of the density and Pitot pressure data to clarify the fundamental flow structure of leek peeler nozzle jets.
文摘An isokinetic sampling probe is designed and constructed to measure entrained liquid droplet fluxes in separated gasliquid pipe flows. This probe also has the capability of working as a non-standard Pitot tube when the sampling is stopped. CFD simulations using the commercial software Ansys CFX were carried out for single phase gas flow to analyze the non-standard design. Pitot tube velocity calculations and isokinetic sampling conditions were studied. The predicted results were compared against theoretical velocity profiles from the literature and with gas single phase experimental data acquired in a horizontal 49 m long steel pipeline with an internal diameter of 69 mm. The experiments were done by using a dense gas (SF6) at 7 bara. An asymmetry of the experimental velocity profiles reproduced with the numerical simulations. The CFD simulations made it possible to verify the design and predict and correct an installation problem.
基金supported by the National Natural Science Foundation of China (Grant No. 30970822)
文摘Pitot probes enable a simple and convenient way of measuring mean velocity in air flow. The contrastive numerical simulation between free supersonic airflow and pitot tube at different positions in supersonic air flow was performed using Navier-Stokes equations, the ENN scheme with time-dependent boundary conditions （TDBC） and the Spalart-Allmaras turbulence model. The physical experimental results including pitot pressure and shadowgraph are also presented. Numerical results coincide with the experimental data. The flow characteristics of the pitot probe on the supersonic flow structure show that the measure- ment gives actually the total pressure behind the detached shock wave by using the pitot probe to measure the total pressure. The measurement result of the distribution of the total pressure can still represent the real free jet flow. The similar features of the intersection and reflection of shock waves can be identified. The difference between the measurement results and the actual ones is smaller than 10%. When the pitot probe is used to measure the region of L=0-4D, the measurement is smaller than the real one due to the increase of the shock wave strength. The difference becomes larger where the waves intersect. If the pitot probe is put at L=SD-10D, where the flow changes from supersonic to subsonic, the addition of the pitot probe turns the original supersonic flow region subsonic and causes bigger measurement errors.
文摘A conceptual coaxial Pitot tube （PT） has been developed using fiber optic sensors combined with actuators to monitor and maintain its correct operation under different environmental conditions. Experiments were performed showing that the dynamic and static tubes can be cleared of ice. It was also demonstrated that the dynamic tube could be cleared of dust and sand which was not the case for the static tube in the coaxial configuration. An approach was proposed to overcome this problem involving a conventional configuration where the static tube was operated independently orthogonal to the dynamic tube, and a second set of sensors and actuators was used. Sensors and associated actuators were developed for temperature and intensity for a linear PT. The aim of this work is to propose a solution for a problem that has caused the loss of the lives of many passengers and crew of aircraft. Resources were not available to test a full implementation of a PT incorporating the proposed modifications.
