US2252368A - Regulating apparatus and method - Google Patents

Description

Aug. 12, 1941.

W. E. GERMER REGULATING APPARATUS AND METHOD Filed Sept. 6, 1938 2 Sheets-Shee t l Ina/enter WzZ/ze/rrziGezwzer Patented Aug. 12, 1 941 UNITED STATES PATENT OFFICE.

REGULATING APPARATUS AND METHOD Wilhelm E. Germer, Berlin-Charlottenburg,

Germany Application September 6, 1938, Serial N0.-228 ,711

In Germany February 23, 1937 7 Claims.

This invention'relates to a regulating apparatus and method and more particularly to the pendent of the amount of air infiltration (after gases leave boiler) contained in the flue gas as regulation of steam boilers or the like to maintain them at maximum efiiciency at all times;

One of the objects of the invention is to provide a regulating apparatus and method for boilers or the like in which the ratio of fuel and air supplied to the boiler is variedunder different .conditions of operation to maintain the boiler at its maximum operating efliciency.

Another object of the invention is to provide a regulating apparatus and method in which the fuel-air ratio is varied in accordance with variations in efliciency.

Yet another object is to provide a boiler regulating system including control elements for the fuel and air in which the fuel and air controls are individually modified in accordance with the boiler fficiency.

Other objects, advantages and novel features of the invention will be apparent from the following description when read in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic viewoi a boiler equipped with a regulating system embodying the invention;

Figure 2 is a diagram of a modified circuit for use in the system of Figure 1; and I Figure 3 is a diagram of another system according to the invention.

The efficiency of a steam boiler is represented by the percentage of the total heat put in the fuel which is converted to useful energy in the steam. The heat input may be divided into three parts; that flowing out in the steam, that flowing out the stack in the gasfand that lost through radiation and in the ash pit, etc. Expressing it mathematically? where E is thetotal heat, E1. is the heat flowingout in the gas, E2 is the heat flowing out in the steam, and E is. the heat lost through the ash pit, radiation, etc. In the case of incomplete combustion a fourth factor.E4 enters in representing the heat lost through unburned gases flowing out the flue.

The factor E1 may beexpressed E1=RM( -Rt-t) cpm 1 where RM is the quantity of gas flow, Rt is the gas' temperature, If is the temperature of air in the boiler room, and cpm is the specific heat of the flue gas. It will be noted that this is indetion,

this air increases the quantity of flow and simulshoe-4s) where D is thequantity of steam flow, 2' is the .heat capacity of the steam, and ts is the feedwater temperature. The heat capacity 2 of saturated steam is substantially constant regardless of pressure and the changes in heat capacity of superheated steam are substantially compensated by errors in an ordinary uncorrected steam flow meter so that a constant mean value of i can be used with very accurate results. Changes in feedwater temperature are small and infrequent and may be taken care of by manual adjustment of a flowmeter or other mechanism operated thereby. Therefore for practical purposes E2 may be said to be equal to the steam flow indication D of an uncorrected flowmeter.

The heat losses E3 are substantially constant for a given boiler and are relatively small.

,They may be determined partly by ash analysis and partly empirically and may! thereafter be corrected for by calibration or adjustment of the instrument.

If n is the boiler efliciency in percent, Va the heat loss in the gas in percent, 'and a. the sum of'the constant losses in percent From this equation and the previous equation the following relation may be derived:

equation may be The factor a is also substantially constant so the boiler efliciency becomes a function of the variable quotient RM(Rt-t) and can be determined by measuring the'se factors. As the boiler room temperature t does not vary widely nor frequently it can be set manually by adjustment or calibration of the instrument.

This method of determining the boiler efliciency and, suitable apparatus for carrying it out are more fully disclosed and claimed in copending applications Serial No.- 174,173, now abandoned, filed November 12, 1937, of which this application is a continuation in part and Serial No. 227,136, filed August 27, 1938.

In operating a boiler it has been found that the maximum efliciency may be difierent at different ratings and that in order to operate the boiler at maximum efliciency at all times it may be necessary to change the fuel-air ratio as the boiler rating changes. According to the present method the eiliciency curve of the boiler is determined and the fuel-air ratio is varied according to this curve as the rating changes.

In carrying out the method of the invention the fuel supply to the boiler is controlled in any desired manner in accordance with steam flow or pressure and the fuel-air ratio is varied according to the maximum efficiency curve ofthe boiler. In some cases this may be substantially constant while in other cases it may vary considerably with the boiler rating depending upon the characteristics of the particular boiler.

As shown in Figure 1 a boiler I8 is formed with an air inlet l2 having a damper l4, a gas outlet or flue I6 and a steam outlet l8. Fuel may be supplied by a stoker 28 or other suitable fuel supply means controlled bysuitable regulators or the like, not shown. Y

The flow of steam through pipe I8 is measured by placing in the pipe an orifice 22 whose opposite sides are connected to a standard uncorrected flow meter 24 which operates a rod 26 proportionally to variations in flow through the pipe i8. Since the flow meter is uncorrected, move- .ments of the rod 26 will be proportional to the quantity of heat in the steam as pointed out above.

The gas flow is measured by placing a venturi or the like28 in the flue l6 and connecting it to a standard flow meter 38 which operates a logarithmic cam 22. Thermometer 84 is preferably inserted in the venturi 28 and is connected to a relay mechanism 86 which operates a logarithmic cam 88. Preferably the connection between the instrument I8 and the cam 88 is adjusted to compensate for the temperature in the boiler room corresponding to the factor it. A bar 48 carries rollers engaging the cams 82 and 88 and is connected at its center to a rod 42 so that the rod will be moved proportionally the sum of the logarithms of the gas flow and the gas temperature.

The ratio of the steam flow to the product of gas flow and gas temperature to obtain an indication the variable quotient set out above is obtained by an electrical circuit including variable resistances 44 and 46 connected to a coil 48 which is movable in the field of a magnet 58. A battery 52 is connected to wipers 54 and 56 movable over the resistances 44 and 46 respectively and connected respectively to the rods 26 and 42. The resistance 46 is preferably a logarithmic resistance arranged to take the antilogarithm of the movement of the wiper 56 so as to give resistance values directly proportional to the product of gas flow and gas temperature. This arrangement provides a balanced circuit effecting a division of the two factors to obtain the quotient to which boiler efllciency is proportional.

The coil 48 forms part of a relay mechanism and operates a contact 58 adapted to engage contacts on aline 68 or a line 62. The lines 68 and 62 are connected to a reversible electric motor 64 which is connected to the damper i4 to operate it. I Current is supplied to the motor from a suitable power line,-one side, of which is connected directly to the motor and the other side of which is connected to the switch arm 58.

In operation the arm 58 is moved by'the coil 48 in accordance with variations in the efliciency of the boiler. If the boiler is not operating, at

its maximum efficiency, the pointer 58 will closea circuit through one or the other of lines 68 and 62 to increase or decrease the supply of air vto the boiler until the correct amount of air is supplied to produce operation at maximum efflciency.

Figure 2 illustrates a modification. of the circuit of Figure 1 in which three variable resistances are combined in a bridge circuit. As shown, a resistance 66 is adjusted by the gas flow meter 38, a resistance 681is adjusted by the steam flowmeter 24 and a resistance 78 is ad- .iusted through a cam 12 by the temperature instrument 36. A fourth fixed resistance 74 completes a bridge circuit and may be constant or if desired may be made variable to adjust for the constant losses in the boiler. A battery IS-is connected across the circuit and a galvanometer or the like I8 is connected across the resistances to operate a contact pointer 88. The pointer 88 is connected to one side of a power line 82 and is adapted to engage lines 84 and 86 leading to a motor 88 which is connected to the other side of the power line.

When the boiler is operating at maximum in which the boiler is normally controlled by a master controller such as shown for example in Smoot Reissue Patent 16,507 and in which the fuel air ratio is changed as the rating changes to maintain the boiler at maximum efliciency.

As shown, a casing III has one face closed by a flexible wall I82 andis connected through a pipe I84 to the steam outlet pipe or steam header of the boiler. Steam pressure urging the flexible wall I02 upwardly is opposed by a plunger I06 engaging the wall and urged downwardly by springs I00. The plunger I is connected to one end of a lever IIO carrying at its other end a cup valve 2 which controls the bleeding of air or the like from a casing I I4. If desired, a dash pot IIG maybe connected to the cup valve to prevent fluttering thereof. Fluid under presthe air regulator is connected to a restriction I30 in an air conduit I32 and has a power element connected to a damper I34 in the conduit. The

fuel regulator is similarly connected across an orifice I38, in a fuel control element I40. The

arrangement shown is particularly adapted for regulating fluid fuel such as gas or oil but. it will be understood that the fuel regulator might equally well control a stoker, a powdered fuel mill or the like as will be appreciated-by those skilled in the art.

The loading pressure supplied to the regulators I20 through pipes I26 are preferably bled down in the box I24 by suitable bleed valves I42. The bleed valves I42 are carried by a lever I44 fulcrumed at its center on a fixed pivot I46. One end of lever I44 is connected to a second lever I48 fulcrumed at its center and carrying a roller engaging a cam I50 which is operated by a steam flowmeter I52. The cam I50 is formed according to the eillciency curve of the boiler, that is, according to the curve of fuel-air ratio for maximum eillciency plotted against boiler rating and serves to move the valves I42 to change the fuel air ratio in response tovariations in boiler rating as indicated by steam flow. Thus with this arrangement, the boiler is atall timles operated at the correct fuel-air ratio for maximum efliciency.

While several embodiments of the invention have been shown and described in detail, it will be understood thatnumerous changes might be made therein and it is not intended to limit the scope of the invention to the exact form shown nor otherwise than by the terms of the appended claims. g

What is claimed is: I I

1. The method of regulating a steam boiler or the like which comprises measuring the flow of steam from the boiler, controllingthe flow of gas through the boiler in accordance with variations in the "steam flow, measuring the flow of gas and the temperature of the gas leaving the boiler, and modifying the gas flow control in accordance with variations in the product of gas flow and gas temperature to increase the gas flow as said product increases and decrease the gas flow as said product decreases.

2. The method of regulating a steam boiler or the like which comprises measuring the flow of steam from the boiler, measuring the flow of gas from the boiler, measuring the gas temperature. multiplying the last two measurements to obtain a product proportional to the quantity of heat leaving the boiler in the gas, combining this product with the steam flow to obtain a quotient indicative of boiler emciency, and varying the ratio offuel and air supplied to the boiler in accordance with said quotient.

3. The method of regulating a steam boiler or the like which comprises measuring the flow of steam from the boiler, measuring the flow of gas from the boiler, measuring the gas temperature, multiplying the last two measurements to obtain a product proportional to the quantity of heat leaving the boiler in the gas,- combining this product with the steam flow to obtain a quotient indicative of boiler efficiency, and varyin the. flow of air through the boiler in accordance with said quotient.

4. Apparatus for regulating a steam boiler or the like comprising means for measuring the flow of steam from the boiler, means to vary the ratio of fuel and air supplied to the boiler, a connection from the first named means to the last named means, and means in said connection for modifying the control of the fuel-air ratio of the boiler in accordancewith the product of gas flow and gas temperature to decrease said ratio as said product increases and to increase said ratio as .said product decreases.

5. Apparatus for regulating a steam boiler or v the like comprising an electric control circuit v to the flow of steam from the boiler for adjusting having two adjustable devices for changing the circuit characteristics, a flowmeter responsive to the flow of steam from the boiler for adjusting one of said devices, a flowmeter responsive to the flow of gas from the boiler, means for measuring the gas temperature, means for multiplyingthe gas flow by the gas temperature and for adjusting the other device according to the product, and means operated by said circuit for varying the ratio of fuel and air supplied to the boiler. 6. Apparatus for regulating a steam boiler or the like comprising an electric control circuit' having two adjustable devices for changing the circuit characteristics, a flowmeter responsive one of said devices, a flowmeter responsive to the flow of gas from the boiler, means for measuring the gas temperature, means for multiplying the gas flow by the gas temperature and for adjusting the other device, according to the product. and means operated by said circuit for controlling the suppl of air to the furnace.

'l'. The method of regulating a steam boiler or the like which comprises measuring the rate of gas flow from the boiler, measuring the gas temperature, multiplying said measurements to obtain a product proportional to the quantity of heat leaving the boiler in the gas, and varying the rate of air supply to the furnace in accordance with said product.

wmnmm E. Gamma

Images