AU8586782A - Method and device for controlling the pressure of a fluid and/or the amount per unit of time of a flow - Google Patents

Description

Method and device for controlling the pressure of a fluid and/or the amount per unit of time of a flow.

The invention relates to a method of controlling a pressure in a chamber, containing a liquid or gaseous fluid.

Controlling the pressure of a liquid or gas contai¬ ned in a chamber is performed by adjusting a flow section. The magnitude of this flow section is dependent on the pres¬ sure of the fluid contained in the chamber and on the magni¬ tude of an adjustable spring tension. An example of this is a reduction valve. A disadvantage of this known method is the fact, that a variation of the selected pressure is only pos- sible by varying the spring tension. Expensive control mem¬ bers are required when applying this method in an,automatic control system.

The invention has the object of reducing the disad¬ vantages of the known method. To this aim said chamber com- prises at least one supply or discharge member, which is fre¬ quently opened and closed alternatively. In this way the pressure prevailing in the chamber can be increased or de¬ creased. As the amount of fluid per unit of time can be con¬ trolled easier by periodically opening and closing said supply or discharge member than by a continuous variation of a flow section, a useful method of controlling the pressure of liquid or gases is obtained. The frequency of opening and closing and/or the duration of opening said member can be selected in dependance on the prescribed pressure. The method according to the invention can be used with burners, in which the amount of gaseous or liquid fuel per unit of time supplied to the burner is controlled. In this way the heat per unit of time delivered by the burner can be controlled exactly by controlling the pressure in the chamber in dependance on the temperature which is decisive for the produced heat.

The invention will be illucidated with reference to the accompanying scheme. The measured value of the process 1 to be controlled, e.g. a gas burner, is picked up by a tem-

OMPI perature sensor 2. The difference between this measured value and a value adjusted by means of a manually operated adjus¬ ting member 3 is supplied to a modulator 4 generating the signals for controlling the supply member 5. In the chamber 6 a pressure will be obtained which is decisive for the amount of gas per unit of time flowing through the nozzle 7 of the burner.

The chamber 6 may have an outlet with a fixed cross section. A flow having a selected amount per unit of time flows through this outlet. This selected amount is the deter¬ mined amount required for producing the required quantity of heat for the process1. This amount per unit of time is depen¬ dent on the selected pressure in the chamber 6 when having a constant flow section of the outlet. The pressure in the chamber 6 is determined by the amount of fluid supplied to the chamber 6 through the supply member 5 constituted by a control member. This control member 5 is a valve which is periodically completely opened and completely closed. The amount of fluid per unit of time is adjusted by selecting the frequency of opening, and closing this valve during a deter¬ mined period of time or by selecting a period of time during each cycle of opening and closing the value when operating the valve with a fixed frequency.

With an alternative embodiment of the device accor- ding to the invention, the outlet of the chamber 6 may have an adjustable flow section.

The supply member 5 may consist of a pump, e.g. a plunjer pump, the number of strokes per unit of time and/or the output per stroke being adjustable. in case the fluid is a liquid the chamber 6 prefe¬ rably comprises a cushion of air or gas constituting a spring.

Claims (9)

1. Method of controlling a pressure in a chamber, containing a liquid or gaseous fluid, characterized in that said chamber comprises at least one supply or discharge mem¬ ber, which is frequently opened and closed alternatively.

2. Method as claimed in claim 1, characterized in that the frequency of opening and closing said member is se¬ lected in dependance on a predetermined pressure.

3. Method as claimed in claim 1, characterized in that the duration of opening said member is selected in dependance on a predetermined pressure.

4. Method as claimed in any one of the preceding claims, characterized in that at least one supply or dis¬ charge member has a constant flow section.

5. Method as claimed in any one of the claims 1-3, characterized in that a discharge member is connected to a fuel nozzle of a burner for liquid or gaseous fluid.

6. Method as claimed in any one of claims 1-3, cha¬ racterized in that the supply or discharge member is consti¬ tuted by a pump.

7. Method of controlling the amount of fluid per unit of time of a flow, characterized in that fluid is supplied to a chamber through a periodically excitated con¬ trol member and is discharged from said chamber through an outlet as a flow having a selected amount of fluid per unit of time due to adjusting the pressure in the chamber at a selected pressure by repeatedly supplying a selected amount of fluid per cycle to said chamber and/or by repeatedly supplying determined amounts of fluid during a selected num¬ ber of cycles per unit of time.

8. Device for carrying out the method as defined in any one of the preceding claims, characterized by a chamber having at least one supply or discharge member provided with means for repeatedly opening and closing said member.

9. Device for controlling the amount per unit of

OMPI time of a flow, characterized by a chamber for receiving a fluid and by a control member connected to said chamber and being excitated periodically for periodically supplying fluid to said chamber, said chamber having a fluid outlet for dis- charging a flow having a selected amount per time unit from said chamber.

OMPI