Page 7 - FANS. Aerodynamic _Selection Meethod__Combine_part2

Zhdanov. Part II. The author of the text and the developer: engineer
Zhdanov V.P. Minsk, Belarus.

NEW THEORY OF PRESSURE DISTRIBUTION

FOR SELECTING A CENTRIFUGAL FAN

Part II.

Note: All graphs of the centrifugal aerodynamic characteristics

fans (hereinafter referred to as fans) and ventilation networks

(hereinafter - ventilation networks) are depicted on a linear scale.

A. Criticism of the existing theory and the existing
method of fan selection

The existing fan selection method and the estimate of the total pressure
developed by it are related to the equation Pt = Ps + Pv (or under other
symbols Pv = Psv + Pdv; Pp = Pc + Pd; Pt = Ps + Pv.o; Ft = Fs + Fvpo) and

reflected on the aerodynamic characteristics of the fan.

In the text, the designations of the equation Pt = Ps + Pv are accepted (see
Fig.1), where:

0-4 –the characteristic of the ventilation network;

0-5 is the calculated curve of the dynamic pressure of the fan Pv (quadratic
parabola) at the discharge pipe of the fan;

3-1 — total pressure Pt developed by a fan, equal to the impedance of the
ventilation network;

2-1 is the value of the static pressure of the fan Ps;

3-2 –the value of the dynamic pressure of the fan Pv for t.1 (“operating
point”);

0-11 – possible actual curve of the dynamic pressure of the fan;

1– “fan operating point” (ventilation unit);