Abstract
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.
Highlights
The average age of farmers of Japanese agriculture is 66.6 years old in 2017 [1] and aging is expected to accelerate rapidly year by year
In addition to Pitot pressure measurements of jet flow fields, rainbow schlieren techniques [3] [4] are for the first time applied to the free jets issued from the conventional and improved nozzles for quantitative visualization of flow fields at high spatial resolution, and they will enable some progress in the understanding of the fundamental fluid dynamics of jets from leek peeler nozzles, since other properties of the jet flow fields including the Mach number, velocity, and temperature can be estimated from a combination of the density and Pitot pressure data
The Pitot probe was mounted on a two-dimensional traversing device to scan the flow field and Pitot pressure measurements were made at intervals of 1.0 mm along the nozzle axis from z = 0 mm to 50 mm and they were based on continuous sampling while moving the probe along the nozzle axis, allowing enough time to reach steady state at each measuring location
Summary
The average age of farmers of Japanese agriculture is 66.6 years old in 2017 [1] and aging is expected to accelerate rapidly year by year It is obviously a daunting and time-consuming task for old farmers to peel white leeks before the shipment. In addition to Pitot pressure measurements of jet flow fields, rainbow schlieren techniques [3] [4] are for the first time applied to the free jets issued from the conventional and improved nozzles for quantitative visualization of flow fields at high spatial resolution, and they will enable some progress in the understanding of the fundamental fluid dynamics of jets from leek peeler nozzles, since other properties of the jet flow fields including the Mach number, velocity, and temperature can be estimated from a combination of the density and Pitot pressure data. Concerning the practical leek peeling process, jet inclined angles would have some effects on the peeling performance; the flow characteristics of free jets only are investigated as the first phase of the study
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