Abstract: The present invention relates to a method for controlling thermal processes, whereby measuring devices measure at least two process parameters at least once within a time interval in which a parameter change occurs that is not negligible for the process sequence, the recorded parameters are fed into a control unit, and the control unit regulates the process parameters in the thermal process by means of quantities obtained from the measurements of process parameters.

Abstract: Apparatus provides an air/fuel mixture to a fully premixed burner and comprises means for providing fuel at a variable flow rate to the burner, means for supplying air at a variable flow rate to the fuel to form the mixture, means for sensing aeration of the fuel combustion products and control means for controlling the fuel flow rate in dependence upon a heat output demand and the air flow rate in dependence upon both the fuel flow rate and the sensed aeration in such a way that the air flow rate is sufficient to maintain the aeration at a predetermined value, the controller, in use, maintaining the fuel flow rate at one of a number of predetermined values and the air flow rate at a corresponding one of a number of differing predetermined values, each set of predetermined values being characterized by a constant value of the ratio between successive values.

Abstract: A power regulating system make it possible to switch on a plurality of power stages with different air flow rates and different fuel flow rates on the burner of the heater. In addition, noise level is optimized, since the blower that maintains the air flow rate turns with a constant output and only the fuel flow rate is modified to regulate the heating power.

Abstract: Information relating to combustion conditions within a fossil-fueled boiler that includes a plurality of burners adapted to produce flames combining to form a fireball is provided by acquiring data relating to the physical and temperature characteristics of the fireball with at least one imaging camera having optical and temperature measuring capabilities; receiving, storing and processing data received from the camera to provide data representative of the NO.sub.x content of the hot gases produced by the fireball; and transmitting the processed data from the processor to a monitor for display. Transmitted, processed data may include current, historical and target information relating to the physical appearance and temperature profile of the fireball.

Abstract: Systems and methods for controlling a draft inducer for use with a furnace. The draft inducer includes a fan for inducing a draft in the furnace combustion chamber that causes a pressure drop across a heat exchanger assembly for moving exhaust combustion chamber gases. The heat exchanger assembly has a plurality of heat exchanger elements which determine furnace capacity wherein the pressure drop across the heat exchanger assembly is affected by the furnace capacity. A motor drives the fan in response to a motor control signal and a memory stores information defining a relationship between motor speed, motor torque and parameters defining motor operation. A processor determines the speed and torque of the motor and retrieves from the memory the parameters corresponding to the determined motor speed and motor torque. The processor is responsive to the retrieved parameters for defining at least one set of speed/torque curves corresponding to a desired pressure drop across the heat exchanger assembly.

Abstract: Systems and methods for controlling a draft inducer for use with a furnace. The draft inducer includes a motor for driving a fan for inducing a draft in the furnace that causes a pressure drop across the heat exchanger of the furnace. A memory stores information including a table of predefined speed/torque values for defining a set of speed/torque curves for operating the motor. A pressure switch provides a pressure signal representative of a reference pressure across the heat exchanger and a processor determines the speed and torque of the motor when the pressure drop corresponds to the reference pressure. In response to the determined motor speed and motor torque, the processor retrieves a parameter defining at least one delta value from the memory. The processor adapts the predefined speed/torque values as a function of the delta value thereby to define the speed/torque curves corresponding to a desired pressure drop.

Abstract: A high efficiency gas furnace utilizes a unique premix design in combination with a pressurized/high velocity combustion process. The combustion process occurs in a combustion chamber and the high temperature high velocity products of combustion follow a circuitous route from the combustion chamber through finned tubular conduits to an exhaust. Heat from the high temperature high velocity products is transferred to the finned tubular conduits. An air blower assembly forces air across the finned tubular conduits and the combustion chamber to remove the heat from the finned tubular conduits and transfer this heat to a building or an enclosed portion thereof.

Abstract: A method and system for controlling and providing guidance in reducing the level of NO.sub.x emissions based on controllable combustion parameters and model calculations while maintaining satisfactory plant performance and not causing other harmful consequences to the furnace. To implement such a system, boiler control values of flow, pressure, temperature, valve and damper positions in addition to emission sensors for data associated with the production of NO.sub.x, O.sub.2, CO, unburned carbon and fuel. This information is received from standard sensors located throughout a boiler which are connected either to a distributed control system (DCS), or another data acquisition system which is time coordinated with the DCS. The DCS passes this information to a computing device which then processes the information by model based optimization simulation programs, also referred to as the NO.sub.x Emissions Advisor.

Abstract: A burner control system for controlling loads such as a blower motor and an electronic pump of a burner which comprises a drive voltage regulating circuit for varying the drive voltages corresponding to the loads to thereby vary the amount of heat being generated from the burner in the actuated condition. A microprocessor outputs a plurality of load control signals. A drive signal generating circuit for initiating in response to the plurality of load control signals received from the microprocessor generates a plurality of drive signals for driving the loads. A driving circuit powers the loads in accordance with the plurality of drive signals from the drive signal generating circuit.

Abstract: With the constantly varying atmospheric conditions, in order nevertheless to achieve constantly a perfect, near stoichiometric combustion with extremely low power consumption and virtually without noise, one supplies solely the instantaneous quantity of air, which is absolutely necessary for combustion, depending on the quantity of fuel supplied, regulated in an exactly metered manner, to the atomization region of an ultrasound fuel atomizer. The air supplied in this way is mixed in the fuel outlet region of the fuel atomizer with the fuel atomized in this way and this mixture is burnt in an adjoining combustion chamber.

Abstract: A burner assembly includes a burner housing having a combustion chamber defined therein and a fuel injection nozzle secured to the burner housing and communicating with the combustion chamber. A fuel control device is provided for controlling the amount of fuel flowing through the nozzle. The fuel control device includes a valve chamber including a bore and a valve seat and a needle valve adapted to reciprocate in the valve chamber. An adjusting device is provided for adjusting a range of motion of the needle valve in the valve chamber. The adjusting device includes a control rod secured at one end to the needle valve and a bimetallic assembly for regulating the motion of the control rod. The bimetallic assembly includes a pair of legs which are operably connected to the control rod and are exposed to the heat produced by the burner assembly.

Abstract: An air-fuel ratio programmable control method for a fuel burner installation, and a fuel burner installation adapted to operate by the control method. In the method, an error (Ep) is determined by subtraction of an input (Po) representative of the existing firing rate and an input (Pn) representative of the required firing rate; depending on whether Ep is positive or negative, fuel and air supplies to the burner are modulated in either air-led or fuel-led manner, respectively, to set the firing rate to the desired value (Pn); in addition, the error (Ep) is compared to a predetermined breakpoint (Xp) so that if Ep exceeds Xp fuel and air supplies to the burner can be modulated simultaneously for fast control action.

Abstract: In a gas furnace designed for operation with natural gas, the use of propane as a fuel is facilitated by increasing the inducer speed by a factor which is obtained by comparing the higher inducer speed necessary to bring down the heat exchanger temperature to an acceptable level, with the original lower inducer speed that had caused the temperature to exceed the allowed limit. Provision is made for electronically applying the multiplying factor by simply operating a gas selector switch.

Abstract: A plurality of burners, e.g., steam boiler burners, are provided with air and fuel through separate conduits. A separate air volume regulator is provided for each burner, but only a single fuel volume regulator is provided for all burners. After one burner has been ignited, a signal representative of the air volume associated therewith is supplied to an additional burner, whereby substantially the same volume of air is supplied to the additional burner. To ignite the additional burner, it is then only necessary to double the volume of fuel being supplied, and divide that fuel volume equally among the burners.

Abstract: An airflow control system generates a compensating output which is combined with the normal damper control output in a damper operating device when a pole change motor driving a blower changes speed so that the damper is changed to compensate for the change in blower speed to avoid a large change in airflow. This overcomes the delay in the normal integrating damper control which produced unwanted fluctuation in airflow when the motor speed was changed.

Abstract: A combustion control system for an oil burner capable of precisely and positively carrying out adjustment of combustion to accomplish complete combustion during combustion operation when a variation in combustion has been carried out. The combustion control system is constructed to detect the rotation speed of the air fan 34 to detect an actual air feed rate and then determine an appropriate fuel feed rate depending upon the actual air feed rate, so that combustion may be stably and efficiently accomplished.

Abstract: In a combustion system, the economic optimum efficiency is achieved by periodically computing a relative index of combustion efficiency using the combustion chamber as a real-time, on-line calorimeter. This is accomplished by first determining the combustion chamber inputs and outputs required to calculate a relative index of performance (including measuring the amount of heat released or work performed at the present air/fuel ratio including the stack losses, without oxygen and/or carbon monoxide sensors), sequentially comparing the latest relative index value with the previous value, then adjusting the air/fuel ratio to achieve an improved index value.

Abstract: For continuous combustion air control in a hazardous waste incinerator, two signals are generated which totalize the air required on a fuel supplied basis. One signal is responsive to measured totalized fuel flow and this total can include fuel flow signals which are limited to the fraction of available air which corresponds to the fuel flow. The other signal is responsive to the totalized fuel flow that is commanded for maintaining an incinerator condition. In use the signal which requires the greater air flow is selected as the actual control signal for combustion air, and this control signal is biased to increase the air flow to obtain complete combustion of the hazardous waste by a controller acting on the measured amount of oxygen in the flue gas. In this manner the combustion air is manipulated in parallel with the waste fuel and if the fuel flow is limited by the available air, the air flow is limited to match the limited fuel flow.

Abstract: There is disclosed an environmental control system for a large volume structure (one horizontal dimension of at least 60 feet) having an air tempering unit including a horizontal cylindrical duct of about three feet diameter with an axial flow propeller fan and motor placed in one end to draw air through the duct and a gaseous fuel burner upstream from the fan with oxygen supplied from the air stream and with combustion products thereof being propelled through the fan. A series of propeller-fan air movers are placed in the structure near ceiling level with the first of the air movers placed about 25 to 50 feet in front of the air tempering unit. The air tempering unit and the air movers are operated by a control unit in response to a cycle timer and various sensor elements including an air velocity sensor for outside air supplied to the air tempering unit and an internal air temperature sensor.

Abstract: Disclosed is a heating system having a combustion air blower, a fuel valve for providing fuel to a burner, and an exhaust stack for exhausting combustion products. Also disclosed is flow sensor apparatus operatively associated with the stack for providing control signals to a furnace control, the control signals being related to flow conditions in the stack.

Abstract: A self-correcting control system and method is provided for a furnace to correct certain operating conditions that exceed normal limits. Upon sensing insufficient air flow as a function of the pressure drop across the heat exchangers, the control system and method cause the inducer motor to increase in speed, thereby to increase the flow of combustion air. Similarly, upon sensing that the flow of air to be heated exceeds a predetermined temperature, the control system and method will increase the speed of the air blower to increase the flow rate of air to be heated through the furnace, thereby resulting in lowering the temperature of the air to be heated below the predetermined temperature. Upon sensing a gas flow leak through the gas regulator, the control system and method will recycle the gas regulator to properly seat a gas flow control valve therein. If none of the self-correcting features correct the particular occurring problem, the control system and method will shut down the furnace.

Abstract: A furnace is operated such that the air-fuel ratio and the temperature rise are maintained constant so that the efficiency remains constant over the range of operation.

Abstract: A means and method for optimizing the efficiency of combustion devices such as furnaces, boilers, ovens, stoves, and the like which automatically tests for and controls the amount of input air utilized by the combustion device to optimize combustion efficiency. The method constantly increases or decreases the amount of input air and monitors the output of the combustion device to see if the change in input air increases or decreases efficiency. If efficiency is increased, the amount of input air is continued to be changed in that direction. If the efficiency is decreased, the change of excess air is reversed. By continuously testing for optimal air fuel ratios, optimal efficiency is reached. The means to accomplish the method include an output monitor, an air input control means, and recording means for recording the output of the combustion device as it presently exists compared to its former reading.

Abstract: A dual-valve controller having a single rotary control element for concurrently adjusting both an air-control valve and a gas-control valve to supply an air/gas combustible mixture to a gas-fired burner. Applied to the inputs of the controller valves are pressurized streams of air and a gaseous fuel. These streams are conducted through the respective valves into a common mixing chamber to provide an output air-gas mixture in a predetermined ratio which is fed into the burner to produce a heating flame. When the control element is manually turned by an operator or automatically by a control motor, it acts to more or less open the valves to corresponding degrees to concurrently adjust the volumetric flow rate of the air and gas, thereby changing the intensity of the flame without, however, altering the air-gas ratio which is set for optimum combustion efficiency.

Abstract: Three burners are supplied with pulverized fuel entrained in air from a splitter and are brought to combustion under optimum conditions by adjustment of the secondary air flow to each. The rates of flow of primary and secondary air are determined and signals from these, and a representation of the total fuel supply are supplied to a computer by which the amount of fuel flowing to each burner is deduced from the ratio of the air supplied to the burners.

Abstract: A temperature compensator for a pressure operated fuel regulator is used in combination with a heat recuperator to regulate fuel flow. In the recuperator, air to be used for combustion of the fuel is heated. Some of the heated air is supplied to the compensator, which comprises a housing having an opening for bleeding air therethrough. The rate of bleeding through of the air, and consequently the pressure drop across the compensator, is dependent on the temperature of the air supplied to the compensator.

Abstract: An air fuel ratio control system comprises a first valve provided in a fuel pipe through which a fuel is supplied to a burner, a second valve provided in an air pipe through which air is supplied to the burner, a varying circuit for varying responsive to a preset flow rate of fuel a valve opening degree of each of the first and second valves while maintaining a constant ratio between the valve opening degrees of the first and second valves, so that an air fuel ratio of a flow rate of fuel flowing through the first valve and a flow rate of air flowing through the second valve assumes a value greater than a theoretical air fuel ratio, a first sensor for detecting a flow rate of fuel flowing through the fuel pipe, a second sensor for detecting a flow rate of air flowing through the air pipe, a fuel bypass pipe provided in the fuel pipe for bypassing the first valve, a third valve provided in the fuel bypass pipe, and a control circuit supplied with output signals of the first and second sensors for controlling a

Abstract: A furnace (A) defines a combustion chamber (10) in which a pair of burners (B) are mounted for oxidizing the fuel to heat the combustion chamber. An air blower (12) supplies air to the burners at a rate controlled by a rate control valve (18). A frequency modulated burner control system (C) controls the duty cycle of the burners, i.e. cyclically actuates the burner at a fixed burn rate and then deactuates them. The burner control system varies the actuation to deactuation ratio in each cycle to vary the thermal input to the combustion chamber. The burners provide two - stage combustion wherein a fuel rich mixture is partially oxidized in a first stage combustion area (44). Additional air which is thereafter introduced through air passages (50, 52) completes the combustion.

Abstract: A method and apparatus for controlling the combustion of multiple fuels, especially fuels having diverse combustion air requirements. A heating rate demand signal indicative of the heating rate desired is generated and is compared with a fuel based fuel heating rate signal. The larger of the two signals is selected to be an air demand signal that serves as set point for a combustion air controller. The flow rates of each of the fuels being burned is monitored and the resulting signals are scaled and summed to produce the heating rate signal. The fuel signals are also scaled by factors reflecting the combustion air requirements of the fuels. The signals are summed and combined with the fuel heating rate signal to produce a feedforward signal which in turn is combined with a signal reflecting the measured combustion air flow to produce an equivalent air heating rate signal.

Abstract: An improved combustion control system for a jackshaft controlled boiler or the like utilizes a second power actuator, a linkage biasing mechanism and a function generator which provides a position control signal as a function of the boiler load in order to position the linkage biasing mechanism to obtain an automatically calibrated, near optimum relationship between fuel and air. An alternative embodiment of this invention includes a flue gas analysis system where the position control signal is modified to further enhance combustion efficiency. This invention also includes a method for programming a programmable combustion control system according to this invention.

Abstract: The well-known "jackshaft" positioning or two-point parallel combustion control system has been modified to include a linkage strut length adjustor apparatus with a remote actuator apparatus. The adjustor apparatus includes an overload protection system to prevent damage to the linkage and control members of the combustion control system.

Abstract: Disclosed is a fuel gas control for controlling the delivery of fuel gas. The present gas control comprises an inlet chamber having an inlet for receiving a supply of gas and an outlet chamber having an outlet for providing a supply of gas. The inlet and outlet chambers are connected by a valve opening. A valve is operatively associated with the opening. The valve has a closed position for preventing the flow of gas through the opening and an open position for permitting the flow of gas through the opening. The present control further comprises control chamber means for moving the valve between its open and closed positions in response to pressure variations within the control chamber means. The present control further comprises apparatus for directly connecting the control chamber means to a pressure signal from a power combustion air blower so that the valve is positioned in response to the pressure signal from the combustion air blower.

Abstract: An integrated, closed loop system for controlling the fuel to air ratio in an induced draft combustion chamber which has a control pilot through which a draft is induced so that the fuel to air ratio in the control pilot chamber has a predetermined ratio to the fuel to air ratio in the primary combustion chamber.

Abstract: The invention concerns a control device for gas boilers. The overall functions involving control and safety are ensured by a control box (26) with microprocessor which centralizes data collected from the ambient thermostat (27), the temperature sensor (28) on the duct (21) for heating water return, the air output sensor (19), the drawing contact (31), the extraction fan (6) speed sensor (30), and the lighter (24), and it converts them into digital signals that are made to operate the lighter, the circulation pump (19), the gas inlet electrovalve (12) and the extraction fan according to the control data that the microprocessor has memorized. Application for forced draft steamtight gas boilers.

Abstract: A two-stage starved air furnace system is controlled to simultaneously achieve desired temperatures and percent stoichiometric air operation in the primary stage by modulating transformation relay functions acting upon measured temperature deviations to change both primary combustion air and primary auxiliary burner operation. At the set-point value of percent stoichiometric air, the relay functions are modulated in reverse direction to satisfy changing heat demands.

Abstract: A burner having an air intake at atmospheric pressure, a gas (fuel) supply line and a combustion chamber in which gas from the latter line burns in the presence of atmospheric air drawn in from the intake, is provided with a swingable or rotatable flap-type valve member which controls the volume rate of flow of the air to the combustion site. According to the invention, the position of the valve member is controlled by a parameter generated by the air stream and in response to the pressure in the gas supply line to maintain the air factor (ratio of air to gas) substantially constant. To this end a membrane type pressure detector responds to the pressure in the gas supply line and is connected by a mechanical force transmission mechanism to the flap or other valve element.

Abstract: A method for controlling combustion of atomized fuel in industrial furnaces, in which flame radiation and temperature distributions in a furnace are controlled into optimum conditions in terms of heat efficiency by adjusting a feed rate of an atomizing medium and/or a distal end position of a burner.

Abstract: A control device controls the air ratio in a combustion apparatus constructed so that combustion fuel supplied via a combustion fuel supplying pipe is burned with oxygen-enriched air obtained by drawing air through an oxygen permeable selective membrane by means of a vacuum pump provided at the downstream side of the oxygen permeable selective membrane and supplied via an air supplying pipe. The control device has an air flow meter and an oxygen concentration analyzer, both provided at the air supplying pipe, and a fuel flow meter provided at the combustion fuel supplying pipe. The air ratio is calculated from the values of the flow rate of of air, the oxygen concentration and flow rate of the combustion fuel. The amount of air drawn by the vacuum pump is controlled so that the actual air ratio is equal to an predetermined air ratio.

Abstract: An improved combustion control system for a jackshaft controlled boiler or the like utilizes a second power actuator, a linkage biasing mechanism and a function generator which provides a position control signal as a function of the boiler load in order to position the linkage biasing mechanism to obtain an automatically calibrated, near optimum relationship between fuel and air. An alternative embodiment of this invention includes a flue gas analysis system where the position control signal is modified to further enhance combustion efficiency. This invention also includes a method for programming a programmable combustion control system according to this invention.

Abstract: The well-known "jackshaft" positioning or two-point parallel combustion control system has been modified to include a linkage strut length adjustor apparatus with a remote actuator apparatus. The adjustor apparatus includes an overload protection system to prevent damage to the linkage and control members of the combustion control system.

Abstract: A variable firing rate burner with a throttle valve assembly that regulates fuel and air intake while maintaining a substantially constant fuel/air ratio over a wide fuel/air flow rate range. The throttle valve assembly includes a pivotally mounted throttle plate that seats on an input manifold, the throttle plate being moved by a driver between low and high firing rate positions. Fuel and air are drawn through the throttle valve assembly and into a mixing chamber by a blower and directed to a flameholder where ignition occurs.

Abstract: A system for marginally adjusting the fuel flow to a burner to maintain the proper oxygen content in the exhaust from the burner is disclosed. The burner is of the type where both the fuel and air flow rates are adjusted in a substantially fixed ratio in response to load changes on the system with the fuel being adjusted by a fuel control valve mounted in a fuel supply line. A self-operating pressure regulating valve having an actuator responsive to the differential pressure across the fuel control valve is mounted in the fuel line upstream of the fuel control valve. A set point adjustment mechanism is mounted on the regulating valve actuator to adjust the set point of the regulating valve in response to an oxygen controller which senses the oxygen content in the stack gases. The set point adjustment mechanism has a cam assembly which continously adjusts the set point of the regulator actuator by varying the compression on a spring loaded diaphragm therein.

Abstract: The efficiency of a furnace is substantially maximized by manipulating the amount of oxygen supplied to the combustion process in the furnace so as to provide a desired oxygen concentration in the flue gas which will result in substantially maximum furnace efficiency. Feed forward control based on the fuel flow rate may also be utilized to enable the control based on oxygen concentration in the flue gas to respond more quickly to a change in the fuel flow rate.

Abstract: The invention relates to a method for operating a gasification (or vaporizing) burner/heating boiler installation and has the objective to develop such an installation in such a manner that it can be operated controllably. According to the invention, the required burner output is determined for this purpose from the outside air temperature, and then the mass flows of the heating oil and the air are controlled as a function of the demanded burner output, deviations from the stoichiometric ratio between the heating oil and the air being leveled-out by means of a lambda-probe arranged in the exhaust gas stream.

Abstract: A burner having an air intake at atmospheric pressure, a gas (fuel) supply line and a combustion chamber in which gas from the latter line burns in the presence of atmospheric air drawn in from the intake, is provided with a swingable or rotatable flap-type valve member which controls the volume rate of flow of the air to the combustion site. According to the invention, the position of the valve member is controlled by a parameter generated by the air stream and in response to the pressure in the gas supply line to maintain the air factor (ratio of air to gas) substantially constant. To this end a membrane type pressure detector responds to the pressure in the gas supply line and is connected by a mechanical force transmission mechanism to the flap or other valve element.

Abstract: A method and an apparatus for dosing the air-fuel mixture in burners of the type which is formed with an evaporator tube (9) through which fuel and some amount of combustion air is introduced in the combustion chamber (1) and in said combustion chamber is mixed with further combustion air and is inflamed. The optimum amount of combustion air is determined for different amounts of fuel and for different reference temperatures in a predetermined point of the evaporator tube (9) adjacent the mouth (10) thereof in the combustion chamber (1), and the temperature of the air-fuel mixture is measured by means of a thermo element (41) in the said point of the evaporator tube (9).

Abstract: A method and apparatus for controlling combustion in a process heater provides for efficient control of the combustion with a minimum of components. The apparatus includes means for generating a signal from a condition of a process such as temperature, or pressure in the case of a boiler. In one embodiment the milliampere signal is presented in series to a resistor to provide an instant proportional voltage signal. This instant voltage signal is then fed into an R-C network to provide a ramp voltage signal. These two voltages are fed into voltage comparator switches which direct the instant voltage signal and the ramp voltage signal to one of two output amplifiers. The output amplifiers control the output signal to the external control devices. The external control devices adjust the flow of fuel and combustion air. The outputs are controlled so as to always provide a fuel-lean mixture during a change in the operating conditions of the process.

Abstract: An induced draft combustion apparatus and its associated control system has a blower located in the exhaust stack or vent which is used to induce the movement of air and combustion products into, through and out of the combustion chamber. A flow-restricting orifice in the exhaust stack near the blower causes a region of higher pressure to exist upstream from the orifice with a region of lower pressure downstream from the orifice. An exhaust gas pressure signal representative of the exhaust gas volume flow rate is sensed on one side of the orifice and is fed back to a modulating gas valve which controls the outlet gas flow from the valve to be proportional to the magnitude of the exhaust gas volume flow rate. By controlling blower speeds and exhaust gas volume flow capacities as related to a selected orifice size, various firing rates for the furnace can be selected, from the design maximum down to various derated levels.

Abstract: A heating system of the type having a combustion chamber with a fuel burner, an inlet for combustion air and an exhaust stack is improved by adding a variable-speed induced draft blower, a flow-restricting stack orifice and a fuel valve sensitive to the exhaust gas flow rate through the stack orifice. The fuel valve turns on at a first predetermined exhaust gas flow rate and turns off at a second predetermined exhaust gas flow rate, which is lower than the first predetermined rate. The fuel valve also supplies fuel at a rate proportional to the exhaust gas flow rate. Sensing of the differential pressure across the stack orifice is used to determine the exhaust gas flow rate.

Abstract: The invention has for its object to provide a control unit for the air choke in an oil burning installation which affords good fuel economy and is simple in construction, while being at the same time easy to mount and adjust. The control unit is composed of a piston cylinder (14) the pressure side of which is connected to the pressure side of the fuel pump (22) of the plant in such a manner that its piston (24) performs a working stroke when the pump starts and returns to the starting position when the pump stops. The piston rod (18) of the piston cylinder unit is coupled to a throttle which opens as a result of said working stroke and closes on the return movement.