The present invention is directed to a method for adapting the performance of a combustion system having at least one burner by controlling and/or regulating the fuel/air mixture of the supplied fuel in the burner corresponding to the quality and/or the caloric content of a standard fuel. The invention is also directed to a combustion system having the burner, a fan and at least one air feeder and at least one fuel feeder, a burner discharge, a burner shaft leading from the fan to the burner discharge, a nozzle situated in the burner shaft for injecting at least one fuel or fuel/air mixture and an ignitor downstream of the nozzle, which system is used with a cooking device having a cooking chamber heated by the combustion system.
Gases having different compositions within a three-gas family, which is composed of city gas, natural gas and liquefied gas, and these are distributed in the domestic and industrial gas supplies. City gas is that gas which has been manufactured, such as by a gasification process of coal, and is sometimes referred to as xe2x80x9ccoal gasxe2x80x9d. As a result, the performance of a combustion system fluctuates corresponding to the quality of the respectively used gas, which is essentially determined by the caloric content of the gas. Therefore, the performance normally is adapted by manually post-adjusting the gas flow, by exchanging the nozzle or measuring the ionization current with a back-coupling with respect to a gas/air compound system. The latter, hitherto, functions only in a restricted fashion within the family of natural gases.
For example, German 198 24 521 discloses a regulating method for gas burners for providing a gas/air mixture, namely for supplying gas current and combustion air current to a burner, wherein an ionization signal of a sensor is used in order to adapt the gas/air mixture to different gas qualities.
An object of the present invention is to further develop a method so that the disadvantages of the prior art can be overcome and to particularly enable an automatic performance adaptation given combustion systems that are operated with fluid.
This object is inventively achieved by designing the combustion system for a specific quality and/or a specific caloric content of a second fuel, acquiring the quality and/or the caloric content of the first fuel and supplying air and/or at least a third fuel, dependent on the determined quality and dependent on the caloric content of the first fuel, to bring the first fuel up to a point at which the specific quality and/or specific caloric content of the fuel reaches that of the second fuel.
It can be provided that the quality and/or caloric content of the first fuel is acquired by measuring at least a chemical property, an optical property and/or a physical property of the first fuel and/or of an exhaust composition of the burner.
It is inventively provided that the heat enthalpy is determined particularly from temperature differences being measured when a test body is heated by a pilot flame.
A first preferred embodiment of the invention can be characterized by a fuel being selected as a second fuel that is of less quality and/or has a lower caloric content than the first fuel. When using the first fuel, the combustion air system is preferably controlled and regulated given the first fuel being of a higher quality to bring the first fuel into comparison with the second fuel, such as by dilution.
A second embodiment of the invention is characterized in that the fuel, which is selected as a second fuel, has a higher quality and a higher caloric content than the first fuel, and in that a third fuel is of an even higher quality and/or higher caloric content compared to the second fuel and is supplied to with the first fuel so as to raise the quality and/or caloric content of the first fuel up to the level of the second fuel.
In addition, the invention also provides a combustion system having a burner, a fan, at least one air feeder, at least one fuel feeder, a burner discharge, a burner shaft leading from the fan to the burner discharge, a nozzle situated in the burner shaft for injecting at least one first fuel and/or a fuel/air mixture and an ignitor downstream of the nozzle. The inventive method is used for adapting the performance of the combustion system and, dependent on the quality and/or the caloric content of the second fuel selected for designing the combustion system, the air can be supplied upstream of the fan, downstream of the fan, upstream of the nozzle, downstream of the nozzle and/or downstream of the burner discharge or at least a third fuel can be supplied upstream of the fan, downstream of the fan, upstream of the nozzle, downstream of the nozzle and/or upstream of the burner discharge.
At least one chamber is provided leading to the fan, to the burner shaft, upstream or downstream of the nozzle, to the nozzle and to the burner discharge and which preferably is fashioned as an external premix chamber for premixing the first fuel and/or the third fuel with air.
The invention also suggests further developments being characterized by a device for determining the quality and/or caloric content of the first fuel, whereby the device for determining the quality and/or the caloric content of the first fuel preferably has a test body, which can be heated by a pilot flame within or outside of the burner, a smell sensor, a viscosity sensor and/or an exhaust sensor.
Finally, the invention relates to a cooking device having a cooking chamber which can be heated via the inventive combustion system.
Therefore, the invention is based on the surprising knowledge that the combustion system can be designed for a specific fuel, for example for the lowest-caloric gas of the three-gas family, namely the city gas or manufactured gas. Given the feeding of a fuel of a higher order, such as natural gas or liquified gas, the air is supplied to the combustion system at different locations up to a point at which the heat content of the fuel/gas mixture corresponds again to the basic design of the combustion system. It can also be inventively provided that the combustion system is designed for a high-caloric fuel, such as a natural gas, and that a high-caloric fuel, such as liquified gas or natural gas, is added when a lower-caloric fuel, such as manufactured or city gas, is used. For the first time, the performance, thus, can be automatically adapted given combustion systems that are operated by gas, in particular.
The fuel quality, particularly the gas quality, is to be automatically recognized, for example by measuring the heat enthalpy by means of a pilot flame, which is fashioned separately or as a component of the burner and which heats up a test body, so that the temperature differences occurring as a result of the heating can be evaluated in order to determine the heat enthalpy. Furthermore, the gas can be recognized via a smell sensor, a viscosity sensor os such. The quality of the gas basically can also be determined by measuring the composition of the exhaust.