Abstract: The invention makes it possible to measure, in real time, the flow of a fluid that is incompressible while having an unsteady flow. The pressure measuring system is primarily comprised of a negative-pressure element (1) placed within the flow and provided with two wall pressure taps (A, B). A means (2) for measuring a pressure difference connected to the pressure taps (A, B) enables the following formula to be solved: dq(t)/dt+?(q(t))=?×?p(t) directly stemming from fundamental equations of fluid mechanics and/or: ?p(t) represents the pressure difference measured by the sensor; q(t) represents the sought volume flow rate, and; ? represents a function of the geometry of the negative-pressure element, of the fluid and of the flow q(t), the particularity of this formula being the consideration of the direction of flow in the second term of the left member of the formula.

Abstract: The invention makes it possible to measure, in real time, the flow of a fluid that is incompressible while having an unsteady flow. The pressure measuring system is primarily comprised of a negative-pressure element (1) placed within the flow and provided with two wall pressure taps (A, B). A means (2) for measuring a pressure difference connected to the pressure taps (A, B) enables the following formula to be solved: dq(t)/dt+?(q(t))=?X×?p(t) directly stemming from fundamental equations of fluid mechanics and/or: ?p(t) represents the pressure difference measured by the sensor; q(t) represents the sought volume flow rate, and; ? represents a function of the geometry of the negative-pressure element, of the fluid and of the flow q(t), the particularity of this formula being the consideration of the direction of flow in the second term of the left member of the formula.

Abstract: An inlet or exhaust line for a reciprocating machine attenuates the sound level of the machine while being simple and economical to produce. A sensor measures the instantaneous flow rate of gases passing through the line while a restriction device variably restricts the cross-section of the line as a function of the instantaneous flow rate measured by the sensor. Material for absorbing acoustic energy covers the internal wall of the line.