Location

Rolla, Missouri

Session Dates

11 Jun 1999 - 17 Jun 1999

Keywords and Phrases

Ventilation; fan stations; stability; fans; ventilation networks; unsteady states; computer simulation

Abstract

Ventilation systems with fans operating in parallel may have multiple operating points. The submitted paper presents a method which enables to reduce the number of points which should be taken into consideration. The concepts of a fan system containing: the fan, inlet duct, regulation door subsystem and its total characteristics were introduced. The analysis of local stability of equilibrium points of the system of ordinary differential equations describing unsteady incompressible flow in a simplified network ventilated by 2 fans in parallel leads to formulation of a simple condition of stability. For fans operating in parallel this condition refers to the slopes of fan systems characteristics, excluding the possibility of stable parallel operation when all fan subsystems operate such that their operating points are on the rising parts of characteristics. To satisfy this requirement at least one fan system must operate on a sufficiently falling part of its characteristics when the remaining ones have their operating points on the rising part. Some graphic examples of construction of ventilation systems characteristics are presented. Results of calculations were graphed to show time variations of flow quantities and pressure during transients caused by the loss of stability.

Department(s)

Mining and Nuclear Engineering

Meeting Name

8th U.S. Mine Ventilation Symposium

Publisher

University of Missouri--Rolla

Document Version

Final Version

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Jun 11th, 12:00 AM Jun 17th, 12:00 AM

On Criteria of Stability of Fans Operating in Parallel

Rolla, Missouri

Ventilation systems with fans operating in parallel may have multiple operating points. The submitted paper presents a method which enables to reduce the number of points which should be taken into consideration. The concepts of a fan system containing: the fan, inlet duct, regulation door subsystem and its total characteristics were introduced. The analysis of local stability of equilibrium points of the system of ordinary differential equations describing unsteady incompressible flow in a simplified network ventilated by 2 fans in parallel leads to formulation of a simple condition of stability. For fans operating in parallel this condition refers to the slopes of fan systems characteristics, excluding the possibility of stable parallel operation when all fan subsystems operate such that their operating points are on the rising parts of characteristics. To satisfy this requirement at least one fan system must operate on a sufficiently falling part of its characteristics when the remaining ones have their operating points on the rising part. Some graphic examples of construction of ventilation systems characteristics are presented. Results of calculations were graphed to show time variations of flow quantities and pressure during transients caused by the loss of stability.