| 摘要 |
<p>Method and apparatus for keeping constant the heat load on gas-fired equipment connected to a gas distribution grid which supplies a gas of variable composition. The pressure of the gas supplied is controlled in such a way, that the square root of the pressure difference between the ambient air and the gas, multiplied by the Wobbe-index of the gas supplied, has a constant value. The Wobbe-index is determined by burning a volume-controlled sample flow of the gas with a volume-controlled excess flow of combustion air and measuring the oxygen content of the combustion gases. This oxygen content has a linear correlation to the Wobbe-index if the fuel gas consists mainly of lower hydrocarbons, as is the case with natural gas. Also, the density of the gas supplied is measured and from the density and the oxygen content measured both the Wobbe-index W as well as the gross colorific value H of the gas are calculated. From the momentary values of H and the gas volume consumed the consumption of heat energy by the gas-fired equipment can be determined, e.g. as a basis for financial settlement.</p> |
