JPS596342B2 - Air-fuel ratio proportional control method - Google Patents

Description

Detailed Description of the Invention The present invention provides proportional air-fuel ratio control that allows the air-fuel ratio to be kept constant even when a resistor such as a heat exchanger that has a condition where the pressure and flow rate are not in a relative relationship is installed. It is about the method.

For example, when a heat exchanger or the like is installed on the air side of an air-gas combustion device for preheating, as the preheating temperature rises, air resistance increases, 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 low pressure loss, narrow flow rate adjustment range, and high equipment cost.

The present invention provides a flow rate control valve in each of an air line and a fuel line, and the flow rate control valves are configured so that their respective flow rate coefficients are proportional to each other so that the opening degree can be freely adjusted. By keeping the respective pressures constant, the air-fuel ratio associated with a resistor such as a heat exchanger installed downstream of the flow rate control valve, where the pressure and flow rate are not in a relative relationship, is maintained constant at all times. The main idea is to completely eliminate the drawbacks of conventional methods, reduce pressure loss, widen the flow rate adjustment range, improve accuracy, and improve the air-fuel ratio. Easy to change; 1. It also has the characteristic that it can be supplied 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 opening degrees can be adjusted in conjunction with each other so that their respective flow coefficients are proportional.

The flow rate control valves 1 and 2 may be of any structure or type, such as a butterfly valve, and the structure for interlocking the flow rate control valves 1 and 2 may include a link mechanism, a gear mechanism, etc., so that their respective flow coefficients are proportional. Any other mechanism may be used as long as the opening degree can be adjusted freely in conjunction with each other.

Reference numerals 3 and 4 designate resistors, such as heat exchangers, which are installed downstream of the flow control valve 1.degree. 2 and have conditions in which the pressure and flow rate are not in a relative relationship, and 5 represents a burner.

In the figure, the heat exchangers 3 and 4 are provided in both the air line A and the fuel line F as an example, but it goes without saying that they may be provided only in either the air line A or the fuel line F. be.

Reference numerals 6 and 7 indicate valves that maintain the differential pressures before and after the flow control valves 1 and 2 constant, respectively.

The valves 6 and 7 are, for example, constant differential pressure valves such as an appliance governor having a diaphragm and a spring, and the heat exchanger 3
, 4 in only one of the air line A or the fuel line F, the line on the side where the heat exchanger 3, 4 is not installed (the air line A or the fuel line F)
), or the valve 7 on the fuel line F side when the fuel is liquid, may be a constant pressure valve.

Note that numerals 8 and 9 are setting valves, and 10 and 11 are branches to other burners.

In this configuration, when the differential pressures before and after the corresponding flow rate control valves 1 and 2 are maintained constant by the valves 6 and 7, the flow coefficients of the flow rate control valves 1 and 2 are always at a constant ratio. Therefore, even if one or both of the air and fuel is preheated by the heat exchanger 3.4 and the resistance increases,
The flow rate ratio of air and fuel passing through each of the flow control valves 1 and 2, that is, the air-fuel ratio, is always maintained constant.

In such a case, the system of the present invention is configured such that the opening degree of the flow rate regulating valves 1 and 2 can be adjusted freely by interlocking the flow rate regulating valves 1 and 2 so that their respective flow coefficients are proportional. Even when the flow rate passing through the burner 5 is changed, the differential pressure before and after the valve 6.7 is kept constant, so the air-fuel ratio is always kept constant. The fuel flow rate can be increased or decreased extremely easily by simply adjusting the opening degrees of the flow rate control valves 1 and 2 while keeping the air-fuel ratio constant.

For this reason, the flow rate control range (i.e., turndown ratio) can be changed to a range where the flow rate coefficients of valves 1 and 2 can be linked under the condition of a constant ratio, which is a very large range, and the pressure loss can be reduced. can be reduced.

For this reason, the normal working pressure of the air or fuel is sufficient, and costs can be reduced.

Further, the flow rate of air or fuel passing through the flow rate control valves 1.2 is determined by the flow rate of the air or fuel passing through the flow rate control valves 1.
Since it is proportional to the square root of the differential pressure before and after the valve 6 or 7 provided in the air line A or the fuel line F.
The flow rate passing through the flow control valves 1 and 2, that is, the air-fuel ratio, can be changed very easily by simply adjusting the set pressure of the flow control valves 1 and 2.

In addition, as described above, in the system 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 to be linked so that the respective flow coefficients are proportional, and the opening degree can be freely adjusted. In this case, the gas may be a liquid as well as the gas, and the effect is that it can be easily applied to a large diameter air line A.

Note that when the fuel is liquid, there is almost no change in volume due to preheating, so the valve 7 may be a constant pressure valve instead of the constant differential pressure valve as described above.

As described below, the method of the present invention provides a flow rate control valve in each of the air line and the fuel line, and the flow rate control valves are configured so that their opening degrees can be freely adjusted in conjunction with each other so that the respective flow coefficients are proportional. By keeping the differential pressure before and after the valve constant, there is no deviation in the air-fuel ratio due to heat exchangers, etc., and it is possible to adjust the air-fuel ratio with high precision over a large flow rate control range, and also to change the air-fuel ratio. It has an effect that can be achieved extremely easily.

[Brief explanation of drawings]

The figure is a system explanatory diagram showing one embodiment of the method of the present invention. Symbols 1, 2...flow control valve, 3, 4...heat exchanger,
5...Burner, 6,7...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 adjusted in conjunction with each other so that the respective flow coefficients are proportional, and the differential pressure before and after the flow rate control valve is adjusted. By keeping each of them constant, the air-fuel ratio associated with a resistor such as a heat exchanger installed downstream of the flow rate control valve, where the pressure and flow rate are not in a relative relationship, is kept constant at all times. Air-fuel ratio proportional control method.