Аннотация:

The present paper deals with the problems of computer-aided design of a centrifugal impeller, screw and pump volute of a liquid rocket pump with the use of a program complex ANSYS. Parametric possibilities of geometry building were used while carrying out optimization calculations of the given values. The possibilities of hydrodynamic characteristics optimization based on the results of the work done were considered. The rotating and the stationary flow parts were obtained, providing optimal hydraulic and cavitation characteristics.

Ключевые слова:

turbopump, screw, centrifugal pump, hydrodynamic characteristics optimization

Основной текст труда

At present it is difficult to imagine the design of a new unit without a preliminary forecast of parameters it can provide. While designing a preliminary project it is necessary to give a general view of the unit, its operation principle and its demands accordance with the customer.

More and more often the designer faces complicated and nontrivial tasks which are extremely difficult to be solved using conventional analytical techniques [1, 2] because of a wide range of variables and boundary conditions being taken into account. The work of a designer can be facilitated to a great extent by finding units optimal characteristics due to the use of engineering analyses program complexes [3–6].

In the paper a general approach to the vane-type unit optimal parameters calculation is given. To solve the given task the engineering complex ANSYS was used which allowed to carry out a modelling and calculations of a liquid flow in the centrifugal impeller of a fuel pump of a turbopump unit under investigation. The calculations were performed for a screw-centrifugal pump under the periodic condition and with the assumption that a working flow in other vane screw and centrifugal impeller channels is identical.

To realize the given approach it was necessary to get the screw and impeller geometry first according to the given parameters (rotational angular velocity, volume flow rate, head, working medium). The meridian cross section is defined with the use of Blade Design module. The “raw” impeller geometry modelling was carried out in the standard module Geometry, Flow Path calculated area and Blade geometry being used. The data parametrization responsible for the blade profile and the quantity, made it possible to get the final centrifugal impeller geometry, corresponding to the optimal static pressure distribution along the meridian crossing profile in accordance with the calculation results in module Vista TF.

In its turn the screw geometry was developed with the use of internal CAD — ANSYS DesignModeler, in which not a finite screw geometry was formed but the volume occupied by the working liquid. The screw geometrical parameters optimization was realized in ANSYS CFX.

The main requirement to be met in the meshes, generated in module Mesh for screw and casing, as well as in TurboGrid for impeller is qualitative resolution of physical effects, occurring during calculated area flow purging.

After finishing preparations for calculations all the objects were introduced into ANSYS CFX, in which flow area model was being developed, taking into account impeller surface periodicity. For boundary surfaces connectivity the Stage function was used, the latter resulting in calculation parameters averaging in the rotation direction. The assumption made it possible to carry out flow calculation without neighboring blades wakes action modelling.

When considering boundary conditions the flow mode with heat transfer was not taken into account, as the hydraulic machines were not supposed to be concerned with this parameter, and the model *k* – ε was determined to be used as a turbulent model. For final calculations total input pressure and output volume flow rate were assigned as boundary conditions at the input and output from the flow region. However, some serial calculations were carried out under total input pressure and output static pressure, but in this case the results validity was also controlled according to the integral flow parameters.

As a result the impeller, screw and pump volute modelling was performed by ANSYS apparatus, rather than external CAD programs. Parametric possibilities of geometry building were used while carrying out optimization calculations of the given values.

The possibilities of hydrodynamic characteristics optimization based on the results of the work done were considered. The rotating and the stationary flow parts were obtained, providing optimal hydraulic and cavitation characteristics.

Литература

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