| 摘要 |
Apparatus 4 is to measure the calorific value and/or Wobbe index of a fuel gas supplied in direction A along pipe 2. A control 22 can operate outlet valves 32 and 36 and can cause inlet valve 20 to be locked in a closed position or unlock it to allow it to open which it normally is until the gas pressure in a chamber 6, of predetermined volume, reaches a predetermined pressure difference above the pressure in the pipe 2. Under direction of control 22, pump 18 pumps fuel gas from pipe 2 in the chamber 6 whilst valves 32 and 34 are closed. On the pressure in chamber 6 attaining the predetermined difference above that in the pipe 2, the valve 20 closes automatically and is then held locked closed by the control. Now the values of certain properties of the gas into the chamber 6 are measured and corrected to standard temperature and pressure. Those properties can be the speed of sound in the gas, and/or the thermal conductivity, and/or specific heat capacity. Then valve 32 is opened and the gas from chamber 6 discharges back to pipe 2 through an orifice plate 34 and conduits 12, 16. This allows the control to measure the value of the property of density of the gas corrected to standard temperature and pressure. Valve 32 is closed again and valve 20 is unlocked so it opens automatically. The pump 18 pumps another sample of gas into the chamber 6 until the gas pressure therein attains the predetermined value above the pressure in the pipe 2 and valve 20 again closes automatically and is then again locked in the closed position. Now valve 36 is opened to allow the gas from chamber 6 to discharge to pipe 2 through a capillary passage 38 and conduits 14, 16. This discharge allows the control 22 to measure the value of the property of the viscosity of the gas at standard temperature and pressure. Stored in the control are sets of prederived values of the different properties each set correlated to a particular calorific value and/or Wobbe index of the gas. The control compares the measured values with those in the sets to establish which set has values nearest to the measured ones and thereby the control infers the calorific value and/or Wobbe index of the gas in pipe 2. <IMAGE> |
