| 摘要 |
<p>Method and device of acoustic flow measurement for determination of the flow velocities of gases and/or of quantities that can be derived from same. In the measurement pipe (1), at a certain distance (L) from one another in the longitudinal direction of the pipe, two microphones (3a, 3b) have been installed, as well as two loudspeakers (2a, 2b) outside said microphones, which loudspeakers feed sound as wide-band, stationary sequences, Sd(t, T) dowstream and Su(t, T) upstream, to the measurement distance (L) defined by the microphones (3a, 3b). The frequency range of the sequences Sd(t, T) and Su(t, T) has been chosen so that only a base mode that proceeds as a plane-wave front can proceed without attenuation. Moreover, the sequences Sd(t, T) and Su(t, T) have been chosen so that they are orthogonal in relation to one another, i.e. they have no common frequency components different from zero. The detector signals detected by means of the microphones (3a, 3b) are processed by means of a substantially real-time signal-processing system, which produces different correlation functions or Fourier transforms of same. From these the system further, by applying various alternative algorithms, determines the travel times of said sound over the measurement distance (L) downstream and upstream, and from these travel times, and from the density determined by it for the gas, the flow velocity, the volumetric flow, and/or the mass flow.</p> |
