Design parameters optimization of BORK company consumer fan.
The following task was set up for ECAR engineers in the boundary of this project: to analyze the design of 6-blades consumer fan designed by Bork company engineers and to estimate the possibility to increase significantly the speed of air flow in check point by blade geometry changes.
Due to the fact that type of the fan (6-blades) was already selected by Bork company and dimensions of fan were limited as a consumer technic the task of ECAR engineers was to define optimal parameters of fan blades to receive maximum air flow with maximum fan rotation speed.
Initial data were the following: existing fan geometry, results of measurement tests of air flow speed in the several check points in line with CNS standards which are used for consumer fans.
The proposed for analyzing fan is assembly with blades made from aluminum sheet bended to needed shape similar to aerodynamic profile.
Initial fan blade.
At the beginning of work the special methodology was proposed. It was noted that aerodynamic calculation of fan blade is equivalent to aerodynamic calculation of helicopter main rotor which works on the hovering flight. So it was decided that methodology of aerodynamic calculation of helicopter blades can be used for calculation of consumer fan blades.
The dissertation work of ECAR engineer “The Study of the main rotor blade stress loading and strength of transient flight regimes and maneuvers” was a basis of methodology development because it allows analyzing propellers on all regimes including steady-state regime.
The mathematic algorithm was developed based on the proposed methodology which could describe behavior of existing fan. This algorithm was adjusted with several iterations till the convergence between calculated results and test results in several check points was reached.
In addition to aerodynamic calculation frequency analysis of fan blade was done. It allowed on the stage of shape definition to avoid coincidence of fundamental frequency with work frequencies of fan to prevent resonance and possible vibration during the work.
Implemented preliminary calculations showed that we can’t get significant improvement of air speed if existing shape of fan blades is used with any modifications (shape changes and blade twist). Moreover it was defined that existing blade has a big aerodynamic drag. It is not allow to reach engine maximum rotation speed.
As result ECAR engineers proposed to the customer the variant of fan blades geometry based on the special aerodynamic profile. In addition it was proposed to change material from aluminium to plastic which could produce the blades of needed shape.
Developed design of the fan.
Based on the proposed geometry customer produced fan prototype and all necessary tests were implemented.
It was reached that calculated characteristics were coincident with tests measured. It was achieved increasing of air flow speed without increasing of fan dimensions and electrical engine power with strength and stiffness provision.