Abstract: A device for controlling the flow rate of a fuel gas/air mixture, and/or the ratio between the fuel gas and air in such a mixture. The device includes a body having an air inlet, a fuel gas inlet, a fuel gas/air mixture outlet, a gas-control passage in the body, with the cross-sectional area of the gas-control passage being variable via a control device for controlling the flow of fuel gas through the device, and an adjustable air-control passage for adjusting the flow of air through the device. The air-control and gas-control passages are configured and disposed in the body in such a way that they cooperate to also form an area within the body where said controlled fuel gas and air flows are combined and mixed.

Abstract: A process and apparatus for the combustion-less measurement and/or regulation of the feeding of quantities of heat to gas combustion devices, particularly natural-gas combustion devices. A fuel gas or a partial stream of the fuel gas is fed through a fuel gas line containing at least one flow resistor which produces a laminar flow and a pressure drop. The gas volume flow and/or the pressure drop over at least one flow resistor is measured by a volume flow metering device and a difference pressure regulator, respectively, the pressure drops and/or volume flows which are not measured being maintained constant. A device compensates for the influence of temperature on the system is compensated. The measured value(s) in accordance with the formula described in the specificationf (H)=a+b.multidot.n.sup.c .multidot..rho..sup.dis a measure of the heat content of the flowing gas and results in a signal which serves for measurement and/or regulation.