Measuring and testing – Simulating operating condition – Marine
Patent
1998-02-12
2000-11-21
Patel, Harshad
Measuring and testing
Simulating operating condition
Marine
73202, 732025, G01F 168
Patent
active
061486639
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a device for measuring the mass of a flowing medium. DE-OS 44 07 209 has already disclosed a device that has a temperature-dependent measurement element that is accommodated in a measurement conduit. The measurement conduit extends in the device from an inlet to an outlet which is adjoined by an S-shaped deflection conduit. The deflection conduit is composed of a first section piece and a second section piece. The first section piece has a right-angled bend and transitions into the second section piece at an edge face. The flowing medium first flows from the outlet of the measurement conduit into the first section piece of the deflection conduit, which has a greater flow cross section than the measurement conduit, so that there is an abrupt flow transition in the form of a step in relation to the first section piece. Then the medium, having been deflected by the first section piece, travels from the corner along the edge face of the first section piece into the laterally adjoining second section piece of the deflection conduit and exits from this out of an outlet opening in order to mix once again with the medium flowing past the device.
In an internal combustion engine, the opening and closing of the inlet valves of the individual cylinders produce considerable fluctuations or pulsations of the flow, whose intensity is a function of the intake frequency of the individual pistons or is a function of the speed of the engine. The pulsations of the flow propagate from the inlet valves via the intake line, to the measurement element in the measurement conduit, and beyond. The pulsations result in the fact that depending on the intensity of the pulsations, due to a thermal inertia and directional insensitivity of the measurement element, it produces a measurement result that can deviate considerably from the flow speed prevailing in the center of the measurement conduit and the intake air mass of the engine that can be calculated from it. The measurement conduit and the deflection conduit are matched to each other in their dimensions in such a way that with a pulsating flow in the intake line, the false indication of the measurement element that occurs due to the flow fluctuations is minimal. Nevertheless, at high pulsation frequencies and significant pulsation amplitudes, due to flow-acoustic processes in the deflection conduit, a false indication of the intake air mass can occur. In particular, this false indication is produced by virtue of the fact that with a pulsating flow downstream of the measurement element at the step between the outlet of the measurement conduit and the corner on the first section piece of the deflection conduit, a pressure wave can be produced which is reflected at the edge face of the deflection conduit at the bend so that the measurement signal of the measurement element experiences interference due to a feedback effect.
ADVANTAGES OF THE INVENTION
The device according to the invention for measuring the mass of a flowing medium, has the advantage over the prior art that a uniformly precise measurement result can be achieved virtually independent of a fluctuating or pulsating flow. This is advantageously possible without in the process having to change the distance between the edge face of the first section piece of the deflection conduit to the outlet of the measurement conduit so that the modulation of the overall conduit comprised of the measurement conduit and the deflection conduit is not impaired, by means of which a compact construction of the device can be maintained.
A flow connection provided in the deflection conduit is for external flow and is disposed in the intake line in the form of an opening, by means of which a residual interference of the pressure wave in the deflection conduit, which could still exist, can be completely eliminated, thus producing a further improvement of the measurement result. Furthermore, the device has markedly reduced measurement signal noise, which can be generated by turbulences that occur in the meas
REFERENCES:
patent: 5355726 (1994-10-01), Zurek et al.
patent: 5696321 (1997-12-01), Igarashi et al.
Konzelmann Uwe
Mueller Wolfgang
Stahl Axel
Greigg Edwin E.
Greigg Ronald E.
Patel Harshad
Robert & Bosch GmbH
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