Open AccessThe knowledge of features of viscous fluid effluent through the sharp-edged orifices and nozzles is necessary when calculating the heat engine fuel feed systems, device designs of chemical production, as well as in designing the components of hydraulic actuators and hydraulic control systems.
Process of fluid effluent through the round shape orifices is rather well studied: in technical publications experimental values of fluid effluent coefficients and their dependence on Reynolds's number are widely presented. The process of fluid effluent through the sharp-edged nonround shape orifices is a little studied, and there is no quantitative assessment of the orifice shape influence on the fluid effluent coefficients. This work to some extent fills shortage of information in issue under consideration.
As an object of study, conditionally sharp-edged equilateral, triangular, square, rectangular, and crosswise orifices were chosen. The inversion process effects on the shape of stream outflowing through the non-round orifice: this process is caused by interaction of surface tension force, aiming to minimize the external surface area of a stream, and force of inertia aimed at momentum conservation of the fluid particle mass being on the trajectory of an elementary stream. Unevenness of field of radial stream rates leaking towards the orifice has essential impact on the shape of the inverted stream.
To raise a flow rate capacity of the non-round shape orifices, was used an external tubular non-expanding nozzle representing a short pipe section the length of which is about three - four diameters of the orifice. Control of the absolute pressure value in the camera of open external tubular non-expanding nozzle with a triangular intake orifice allows us to change its flow rate capacity in the certain, rather narrow range. Pressure in the camera of tubular non-expanding nozzle was changed through its regimented opening to atmosphere using an adjustable precision throttle. A controlled absolute pressure in the camera of open external tubular non-expanding nozzle provides a stream rate control depth to 13%.
As a result of the conducted pilot studies it was shown that the flow rate of studied nonround shape orifices with fluid effluent to atmosphere is more than the flow rate capacity of the round orifice, and a value of the flow rate coefficient of equilateral triangular orifice 10% exceeds the value of the flow rate coefficient of the round orifice.
Use of non-round shape orifices as a part of external tubular non-expanding nozzles to increase their flow rate capacity was of essential interest.
The experiment has shown that the physics of hydrodynamic processes in the tubular nonexpanding nozzles of the open and closed type is not identical.
Calculated values of a flow rate coefficient of external tubular non-expanding nozzle with non-round shape intake orifice are well in compliance with experimental data. The amount of pressure loss with expanding stream in the sleeve of external tubular non-expanding nozzle can be assumed to be equal to the loss of pressure with a suddenly increasing channel diameter, according to Bord's formula. Comparison of calculated and experimental values of flow rate coefficients of external tubular non-expanding nozzles allowed to accept values of coefficient of hydraulic resistance of intake orifice and rate coefficient for the free and flooded streams to be equal and independent on the shape intake orifice.
The reason of increasing flow rate capacity of non-round shape orifices can be considered as that of caused by features of a field of the radial stream rates leaking towards the intake orifice and defining increase of the relative area of a stream.