Collector

The collector of a centrifugal compressor can take many shapes and forms. When the diffuser discharges into a large empty chamber, the collector may be termed a Plenum⁸. When the diffuser discharges into a device that looks somewhat like a snail shell, bull's horn or a French horn, the collector is likely to be termed a volute or scroll⁹. As the name implies, a collector’s purpose is to gather the flow from the diffuser discharge annulus and deliver this flow to a downstream pipe.

1. inlet – входное (впускное) отверстие

2. impeller – импеллер, лопастное колесо, крыльчатка

3. diffuser – диффузор, распылительvanes/airfoils – лопасти/крылья

4. blade – лопасть

5. vaned – крыльчатый

6. solidity – твёрдость, плотность

7. plenum – заполненное веществом пространство

8. volute or scroll – спираль или свиток

Text № 6 Fictitious Centrifugal Force

Centrifugal force¹ is often confused with centripetal force². Centrifugal force is most commonly introduced as an outward force apparent in a rotating frame of reference³. It is apparent (fictitious) in the sense that it is not part of an interaction but is a result of rotation - with no reaction-force counterpart⁴. This type of force is associated with describing motion in a non-inertial reference frame⁵, and referred to as a fictitious or inertial force (a description that must be understood as a technical usage of these words that means only that the force is not present in a stationary or inertial frame).

There are three contexts in which the concept of fictitious centrifugal force arises when describing motion using classical mechanics:

In the first context, the motion is described relative to a rotating reference frame about a fixed axis at the origin of the coordinate system. For observations made in the rotating frame, all objects appear to be under the influence of a radially outward force that is proportional to the distance from the axis of rotation and to the square of the rate of rotation (angular velocity) of the frame.

The second context is similar, and describes the motion using an accelerated local reference frame attached to a moving body, for example, the frame of passengers in a car as it rounds a corner. In this case, rotation is again involved, this time about the center of curvature of the path of the moving body. In both these contexts, the centrifugal force is zero when the rate of rotation of the reference frame is zero, independent of the motions of objects in the frame.

The third context arises in Langrangian mechanics⁶, and refers to a subset⁷ of generalized forces that often are not equivalent to the vector forces of Newtonian mechanics.

1. centrifugal force – центробежная сила

2. centripetal force – центростремительная сила

3. frame of reference – система отсчёта, система координат

4. counterpart – контршаблон, дубликат, копия

5. non-inertial reference frame – неинерциальная система координат

6. Langrangian mechanics – механика Лагранжа

7. subset – подмножество

Text № 7