Various embodiments of the teachings herein include a mixer disposed in a fuel gas combustion system and mixing air and fuel gas to form flammable mixed gases. The mixer may include: a Venturi tube having an air inlet, a fuel gas inlet, a gas mixture outlet, a central axis direction, and a throat positioned between the air inlet and the gas mixture outlet in the central axis direction, wherein the fuel gas inlet is disposed at the throat; and an adjustment component disposed in the Venturi tube downstream of the throat, the adjustment component drivable to move towards or away from the throat in the central axis direction, thereby changing a flow area of gas in the Venturi tube. The adjustment component comprises a conical valve plug with a conical outer surface thereof at a side facing towards the throat and fitting an inner surface of the Venturi tube.

The disclosed technology includes a device for extending the turndown ratio of a gas-fired burner system. The device can comprise a variable area device configured reduce the amount of fuel and air passed to the burner during low output conditions by adjusting the cross-sectional area of the passage between the blower and the burner. The variable area device can be controlled by an actuator that adjusts the position of the variable area device. The actuator can be manually controlled, mechanically controlled, or electronically controlled.

A double swirl burner including an annular air nozzle, an annular fuel nozzle coaxially disposed within the annular air nozzle, and a central air nozzle coaxially disposed within the annular fuel nozzle. An annular air nozzle may include at least one first inlet port on a peripheral wall of the annular air nozzle, where the first inlet port may be configured to allow for tangentially injecting a first air stream into the annular air nozzle. A first air stream may be tangent to a circular cross-section of the exemplary annular air nozzle, and a first axial inlet that may be configured to allow for axially injecting a second air stream into the annular air nozzle along a centerline of the annular air nozzle.

Apparatus for controlling the flow of air through an air inlet in a solid fuel burner comprises: a mechanical temperature sensor for sensing the temperature within the solid fuel burner, the sensor comprising first and second elongate parts having different coefficients of linear thermal expansion and arranged such that a first end of the first elongate part moves linearly relative to a first end of the second elongate part in response to a change in the sensed temperature; a movable valve member for controlling the flow of air through the air inlet; and a mechanism for coupling the first end of the first elongate part to the movable valve member so as to close or restrict the air inlet as the sensed temperature increases.

A fluid heating system including a burner unit is operated based on feedback control loops. The fluid heating system comprises a burner unit configured to heat a fluid, a sensor configured to sense a characteristic of the appliance, and a controller coupled to the burner unit and the sensor. The controller includes an electronic processor and a memory. The controller is configured to receive a first signal corresponding to the characteristic from the sensor, determine, based on the first signal, a first feedback loop control, control combustion of the burner unit based on the first feedback loop control, determine, based on the first feedback loop control, a second feedback loop control, and control combustion of the burner unit based on the second feedback loop control.

A method for evaluating a quasi-stationary pressure difference detectable by a sensor at a gas boiler. The gas boiler has a mixing device (4), a fan (5), a main flow regulator (3), .a control valve (2) and a safety valve (1). The sensor detects a differential pressure between a pressure (p2) at a measuring point upstream of the main flow regulator (3) and downstream of the control valve (2) and a reference pressure (p0, p1) at a reference measuring point. The sensor transmits a signal to an electronic evaluation system. The electronic evaluation system compares the differential pressure during a pre-purge phase, wherein the safety valve (1) is closed, with the differential pressure after the pre-purge phase and detects an error by the comparison.

A gas appliance comprises a combustion device, an ignitor, a gas valve, a blower, a detecting device, and a control device. A control method thereof comprises: the control device is operated in a detection mode in which the control device controls the ignitor to ignite and controls the gas valve as well as the blower to provide a fixed gas flow and a fixed air flow to the combustion device. After igniting the flames, the control device determines burning states detected by the detecting device; if matching a first state, the control device controls the gas valve and the blower in correspondence to a first control data of the first natural gas; if matching the second state, the control device controls the gas valve and the blower in correspondence to a second control data of the second natural gas. In this way, the gas appliance is suitable for burning natural gas generating various heating values.

A premixing apparatus that mixes a fuel gas with air and supplies an air-fuel mixture in a burner through a fan includes a control device that is configured to carry out a third control that: calculates and memorizes a lower limit of a rotational speed of a fan, at which an increase of an opening degree of a variable throttle valve becomes necessary, as a first threshold; and when the rotational speed of the fan increases to the first threshold or faster next time, immediately changes the opening degree of the variable throttle valve to an increased opening degree, which is larger than a predetermined standard opening degree and is obtained by multiplying a deviation of the rotational speed of the fan from the first threshold by a predetermined coefficient.

A stove for indoor use includes a housing having a bottom wall, a top wall and one or more side walls defining a combustion chamber adapted to retain a fire, and an air supply system for supplying air to the combustion chamber. The air supply system includes a primary air conduit for supplying air to the combustion chamber from below through the bottom wall and a secondary air conduit for supplying air to the combustion chamber from above. A valve is arranged in the primary air conduit or in a branching between the primary and secondary air conduits. The valve is controlled by a bimetal whereby the valve is in a maximum open position when the prevailing temperature is below a first predetermined temperature during start-up of a fire and in a maximum closed position when the prevailing temperature is above a second predetermined temperature after start-up of the fire.

A combustion air proving (CAP) system for a burner assembly having a burner for providing heated air to a location, a controller, and a back plate, where outside air is fed to the burner via a conduit. The CAP system is connected to an inlet of the system. An outlet of the system is connected to the burner via the back plate. A damper within the system is translatable between open and closed positions for allowing and blocking air flow, respectively. A sensor measures an air flow parameter of air flow to the burner. The sensor communicates with the controller, which shuts down the burner if the parameter measured by the sensor meets a predetermined threshold value. An assembly installer may test for proper sensor and controller functions by translating the damper to the closed position and blocking outside air flow.