Method and an installation for adjusting the flow rate of air in a network of ducts

• US 5,269,660 A
• Filed: 02/26/1992
• Issued: 12/14/1993
• Est. Priority Date: 07/02/1990
• Status: Expired due to Fees

• Current Assignee: Compagnie Generale DES Etablissements Michelin SCA
• Original Assignee: Compagnie Generale DES Etablissements Michelin SCA
• Inventors: Pradelle, Bernard
• Primary Examiner(s): Bertsch, Richard A.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/836,016
• Time in Patent Office: 657 Days
• Field of Search: 417/18, 417/20, 417/45, 417/53, 417/63
• US Class Current: 417/18
• CPC Class Codes: E21F 1/00 Ventilation of mines or tunnels; Distribution of ventilating currents ventilating rooms or spaces in general F24F
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: F05D 2270/335 Output power or torque
• CPC Class Codes: F24F 11/72 for controlling the supply of treated air, e.g. its pressure
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: G05D 7/0682 using a plurality of flow sources
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

The installation serves to adjust the flow rate of air in a network of ducts such as a mine. It comprises a fan (10) provided with an electric motor (16) powered at a variable frequency. The installation also includes a converter having an adjustable output frequency and measuring means (12, 22) for measuring the flow rate and the total pressure supplied by the fan. It also includes a processor (20), a memory (26) for storing in digital form at least one total-pressure/flow-rate characteristic curve, and optionally a pressure/flow-rate characteristic curve of the fan at at least one predetermined speed; means (30) for displaying said curves; and data input means enabling a reference value (Q_c) to be given to the flow rate to be conveyed by the network, the central calculation unit (14) being designed to calculate the resistance (R) of the network and the flow rate (Q) flowing therethrough at a given instant on the basis of signals provided by the measuring means, and being designed to calculate the speed to be given to the fan by interpolation on the basis of the results of the preceding calculation and of the reference value for the flow rate.

Claims

1. A method of adjusting air flow rate in a network of ducts by controlling the speed of at least one rotary fan (10) for causing air to flow, the fan being provided with an electric motor (16) whose speed is a function of the frequency delivered by an adjustable frequency converter controllable by a central calculation unit, the method being characterized in that:

a) at least one characteristic curve of total pressure as a function of flow rate at at least one predetermined speed is stored in the central calculation unit (14);

b) at least the flow velocity and the total pressure (H_t) supplied by the fan are measured under steady operating conditions and the flow rate at a current instant and the resistance of the network are deduced therefrom by calculation by means of the central unit;

c) the reference flow rate to be supplied by the fan (10) is input into the calculation member, and the theoretical total pressure to be supplied by the fan (10) is deduced therefrom by calculation by the central unit (14);

d) the speed to be given to the fan is determined by interpolation between the characteristic curves as stored and as deduced by calculation, and the converter (18) is set to the corresponding frequency by means of the central calculation unit; and

e) the velocity and the total pressure measurements are repeated to determine the resulting real flow rate, and the set frequency of the converter is optionally corrected to obtain the required reference flow rate.

2. An installation for adjusting the air flow rate in a network of ducts, the installation comprising:

at least one air flow fan (10) provided with an electric motor (16) whose speed is a function of the frequency of the electricity supplied thereto;

a converter (18) supplying electricity at an output frequency that is adjustable by a control signal applied to the converter; and

measuring means (12,

     22) for measuring the total pressure supplied by the fan, the flow rate in the network, and optionally the electrical power (Pe) absorbed by the motor of the fan;

the installation being characterized in that it also includes a central calculation unit (14) having;

a processor or computer (20);

a memory (26) provided to store in digital form at least one characteristic curve of total pressure as a function of flow rate, and optionally a characteristic curve of power as a function of flow rate of the fan, at at least one predetermined speed;

means (30) for displaying said curves; and

data input means enabling a reference value (Q_c) to be set for the flow rate through the network, the central calculation unit (14) being designed to calculate the resistance (R) of the network and the flow rate (Q) passing therethrough at a given instant, on the basis of the signals provided by the measuring means, and being designed to calculate the speed to be given to the fan by interpolation on the basis of the results of the preceding calculation and of the reference value for the flow rate, and to control the converter in such a manner as to achieve said speed.

3. An installation according to claim 2, characterized in that said measuring means include analog-to-digital converters providing digitized samples to the central unit.

4. An installation according to claim 3, characterized in that the central unit (14) is designed to take account of mean values of the total pressure and of the flow rate.

5. An installation according to claim 2, characterized in that the means for measuring the flow rate include means for measuring the dynamic head in the duct, on the basis of which the central unit determines the flow rate.

6. An installation according to claim 2, characterized in that it includes display means for showing the current characteristic curves as a function of the flow rate.

7. An installation according to claim 2, characterized in that the central unit is designed to compare the reference flow rate with the current flow rate and to readjust the speed of the fan at regular intervals or whenever the difference between the flow rates exceeds a predetermined threshold.

8. An installation according to claim 2 having a plurality of fans disposed in parallel, the installation being characterized in that the central unit is designed to distribute the reference flow rate and variations in said flow rate evenly between the fans.