JPS601530B2 - Air-fuel ratio proportional control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an air-fuel ratio proportional control method that allows the air-fuel ratio to be kept constant even when a resistor such as a heat exchanger that has a condition where pressure and flow rate are not in a relative relationship is installed. It is related to.

For example, when a heat exchanger or the like is provided on the air side of an air-gas combustion device to generate heat, air resistance increases as the heat temperature rises, the air flow rate decreases, and the air-fuel ratio changes.
To prevent this, various methods have been proposed in the past, but they have various drawbacks such as large pressure loss, small flow rate adjustment range (i.e. turndown ratio), and high equipment cost. . In the present invention, a flow rate regulating valve is provided in each of the air line and the fuel line, and the particle quantity regulating valve is configured to be able to freely adjust the relationship by interlocking so that the respective flow coefficients are proportional. By controlling the pressure in the fuel line and the pressure in the air line to be equal at all times using pressure equalizing valves on the and downstream sides, the pressure and flow rate of the heat exchanger etc. installed on the downstream side of the flow rate adjustment valve can be adjusted. The gist of this system is to maintain a constant air-fuel ratio at all times regardless of resistors that have unrelated conditions, completely eliminating the drawbacks of the conventional system and reducing pressure loss. However, it has the characteristics of widening the flow rate adjustment range, improving accuracy, and being able to supply it at low cost. Hereinafter, the method of the present invention will be explained in detail based on the drawings showing one embodiment. In the figure, A indicates an air line, and F indicates a fuel line, and the air line A and the fuel line F' are provided with flow control valves 1 and 2, respectively.

The flow rate regulating valves 1 and 2 are constructed so that their respective flow coefficients are proportional to each other and can be freely adjusted. the flow rate control valve 1;
The valve 2 may be of any structure or type, such as a butterfly valve, and the structure for interlocking the flow rate regulating valves 1 and 2 may include a link mechanism, a gear mechanism, etc., so that the respective flow coefficients are proportional to each other. Any other mechanism may be used as long as it is adjustable. Reference numerals 3 and 4 indicate resistors, such as heat exchangers, which are installed downstream of the flow control valves 1 and 2, respectively, and have a condition in which the pressure and flow rate are not in a relative relationship, and 5 indicates a burner. In the figure, the heat exchangers 3 and 4 are provided in both the air line A and the fuel line F, but it is also possible to provide them only in either the air line A or the fuel line F. Of course. code 6,7
is a pressure equalizing valve that controls so that the pressure in the fuel line F and the pressure in the air line A are always equal on the upstream and downstream sides of the flow control valves 1 and 2, respectively. The pressure equalizing valves 6, 7
In the figure, it is installed in the fuel line F to control the pressure in the fuel line F to be equal to the pressure in the air line A, but conversely, it is installed in the air line A to control the pressure in the air line A. Of course, the pressure may be controlled to be equal to the pressure of the fuel line F. In addition, symbols 8 and 9 are setting valves, 1
0,11 indicates branching to other burners. In this configuration, when the pressure in the fuel line F and the pressure in the air line are equalized by the pressure equalizing valves 6 and 7 on the upstream and downstream sides of the flow rate control valves 1 and 2, respectively, the flow rate control valve 1 ，
Since the differential pressures of the two flow control valves 1 and 2 are equal to each other, the flow control valves 1 and 2
The flow rate ratio of air and fuel passing through the flow control valves 1 and 2 is
is equal to the ratio of flow coefficients.

Since the flow rate coefficients of the flow control valves 1 and 2 are always constant, even if one or both of the air and fuel is heated by the heat exchangers 3 and 4 and the resistance increases, the respective flow coefficients are constant. The flow rate ratio of air and fuel passing through the flow control valves 1 and 2, that is, the air-fuel ratio, is always kept constant. In such a case, in the method of the present invention, the opening degrees of the flow rate regulating valves 1 and 2 can be adjusted, since the flow rate regulating valves 1 and 2 are linked so that the respective flow coefficients are proportional, and the opening degree can be freely adjusted. Even if the flow rate passing through the pressure equalizing valves 6 and 7 is changed,
Since the differential pressure is equal, the air-fuel ratio is always kept constant, and therefore the air-fuel ratio can be kept constant by simply adjusting the opening degrees of the flow control valves 1 and 2 of the air and fuel supplied to the burner 5. You can increase or decrease it very easily while maintaining it. For this reason, the flow rate control range (i.e. turndown ratio) can be changed to a range where the flow rate coefficients of the flow rate regulating valves 1 and 2 can be linked under the condition of a constant ratio, which is a very large range and reduces pressure loss. be able to. For this reason, the normal working pressure of the air or fuel is sufficient, and costs can be reduced. In addition, as described above, in the method of the present invention, the flow rate regulating valves 1 and 2 provided in the air line A and the fuel line F' are configured so that their opening degrees can be freely adjusted by interlocking them so that their respective flow coefficients are proportional. The gas may be liquid as well as the gas, and the large diameter air line A
There are also effects that can be easily applied. As described above, the method of the present invention provides a flow rate control valve in each of the air line and the fuel line. By controlling the pressure in the fuel line and the pressure in the air line to be equal at all times using pressure equalizing valves on the upstream and downstream sides of the system, there is no difference in the air-fuel ratio due to heat exchangers, etc., and a wide flow control range is achieved. This has the effect of making it possible to perform highly accurate air-fuel ratio calculations over a period of time.

[Brief explanation of drawings]

The figure is a system explanatory diagram showing one embodiment of the method of the present invention. Code, 1, 2...Flow control valve, 3, 4...Heat exchanger, 5...Burner, 6,7...Pressure equalization valve, 8,9...
Setting valve, 10, 11...branch, A...air line,
F...Fuel line.

Claims (1)

[Claims] 1. A flow rate control valve is provided in each of the air line and the fuel line, and the flow rate control valve is configured so that the opening degree can be freely adjusted in conjunction with each other so that the respective flow coefficients are proportional, and the flow rate control valve is configured such that the opening degree can be freely adjusted. By controlling the pressure in the fuel line and the pressure in the air line to be always equal using the pressure equalization valve in each of the above, the relative relationship between the pressure and flow rate of the heat exchanger etc. installed downstream of the flow rate control valve is maintained. An air-fuel ratio proportional control method that maintains an air-fuel ratio constant regardless of a resistor having conditions that are not met.