Showing papers on "Thermal mass flow meter published in 1981"

Gas control system for chemical vapor deposition system

Abstract: A gas flow control system in which several constituent gases are mixed and the mixture delivered through controlled injectors to a processing zone. Mass flow controllers control the injector flows with one of the controllers being a master and the other being slaved to provide a selected percentage of the flow through the master controller. The gas mix is regulated by a mass flow controller on one of the constituents and a flow meter on the other, the flow meter producing an error signal which is used to readjust the total flow through the injectors by control of the master injector flow controller.

Measurement of very large flow angles with non-nulling seven-hole probes

Abstract: This paper describes a method for measuring local direction and total and static pressures of a flow by means of a fixed probe, provided that the local air flow does not make an angle of more than 80 degrees with the axis of the probe. The probe is easily manufactured from standard-sized tubing materials. The power series calibration method used with the probe results in explicit polynomial expressions for the desired aerodynamic properties. The calibration method is easily programmed on a data acquisition system. This paper includes an example of a complete incompressible calibration.

Air flow rate measuring device incorporating hot wire type air flow meter

Abstract: The invention relates to an air flow rate measuring device making use of a hot wire type air flow meter and adapted to measure the true intake air flow rate while compensating for the error attributable to the reversing of the air. The device includes an operation unit adapted to accumulate the output from the hot wire type air flow meter to calculate an apparent intake air flow rate Qa =Q1 +Q2, where Q1 is the flow rate during reversing of the air while Q2 represents the flow rate during forward flowing of the air. The apparent flow rate Qa is discriminated by a signal derived from means for detecting the period in which the reversing of intake air takes place into the flow rate Q1 in the reversing or backward direction and the flow rate Q1 in the forward direction, by means of the operation unit. Another operation unit performs the calculation of difference Q2 -Q1 to determine the true air flow rate Qo.

Groundwater flow meter

Abstract: Flow characteristics of a fluid through a permeable solid medium are determined by introducing a predetermined quantity of thermal energy at a highly localized point within the medium and subsequently mapping temperatures around such point to determine the direction and rate of fluid flow through the medium.

Method and apparatus for measuring flow characteristics of a moving fluid stream

Abstract: This invention relates to the measurement of the temperature and/or mass flow rate of a free falling molten stream of material. Previous techniques have not recognized the effects temperature variations of the molten stream of material have on the measurement of the above flow properties. The present invention utilizes a line scan camera (24) having photodiodes disposed in a predetermined array to measure the temperature and mass flow rate of a moving mass of molten material (22). This is accomplished in the present invention by limiting the maximum voltage (26) generated by any one photodiode exposed to light energy of a mass by varying the scan rate and thus the exposure time of the photodiodes in response to a variance in the light intensity and thus the temperature of the molten mass of material.

Hot wire flow meter

Abstract: A hot wire flow apparatus for generating a flow rate signal indicative of the actual flow rate of a pulsating fluid flow The apparatus utilizes a wire element connected with a temperature compensating circuit to generate a flow rate signal indicative of the pulsating fluid flow, but lower in value than the equivalent steady state flow rate A correction circuit is provided to receive the flow rate signal and generate a corrected flow rate signal indicative of the actual flow rate of the pulsating fluid

Air flow measurement techniques for air fuel ratio control

Abstract: Measurement of air flow into an engine is the basis for precision control of the engine air/fuel ratio. Such control is needed both to maximize fuel economy and minimize pollutant emissions. Recent developments have focused on air flow meters for electronic engine controls but the performance specifications which an air flow meter must meet are stringent. The flow range is typically forty to one with the greatest accuracy required at the low end of the flow range. The meter must also be able to accurately follow flow transients. Mass flow measurement is preferred, but volumetric flow measurement may be acceptable in adaptive control systems. Stringent meter specifications make common approaches such as differential pressure techniques or turbine meters undesirable. Three measurement techniques which have been the subjects of development programs are vortex shedding, hot wire anemometry and acoustic velocimetry. These three approaches are analyzed in detail to show strengths and weaknesses. The vortex shedding and acoustic approaches are feasible for volumetric flow measurement and have the potential with further development to become valid air mass flow meters. The hot wire meter is an excellent device, but the fragility of the wire and its susceptibility to contamination may prevent it from being a viable approach for long term underhood operation. A near term approach would be to produce a volumetric meter while pursuing evolution of a mass meter based on the volumetric meter design. Mass air flow measurement continues to be a difficult task requiring further developments.

Device for measuring the mass flow of a flowing medium, in particular for measuring the mass flow of fuel fed to combustion engines

Abstract: A device for measuring the mass flow of a flowing medium is proposed, which has a measurement zone (26) which is located in a flow channel (23) and has at least two gaps (27, 28) running in the flow direction of the medium. The delimiting wall of at least one gap (27) is formed by a carrier (31) on which a hot-layer resistance layer (3) is applied, whose temperature and/or resistance are controlled in dependence on the mass flow of the medium and the control variable is a measure of the mass flow of the flowing medium. On that surface of the carrier (31) facing away from the hot-layer resistance layer (3), a further resistance layer (4) of the bridge circuit may be provided. Further layer resistors of the bridge circuit may be arranged on further carriers (32, 33). A calming zone (36) upstream of the measurement zone (26) serves for calming the medium flow. The device according to the invention ensures stable conditions for exact measurements over a very wide measurement range.

A non-invasive flow monitor for metal pipelines

Abstract: A non-invasive method of monitoring gas flow in pressurised metal pipelines is described. The electrical resistance of a heated section of pipe as a function of gas flow is monitored using low-cost circuitry. The instrument provides accurate timing of pulsed gas flows and may be calibrated to measure flow rate and volume. The system has general applications in monitoring fluid flow in metal pipes of various shapes carrying hazardous and volatile fluids.

Mass flow meter for air in an internal-combustion engine

Abstract: Es wird eine Luftmassenmeseinrichtung bei einer Brennkraftmaschine mit einer im Luftansaugrohr angeordneten Stauklappe und einer damit gekoppelten Signalerzeugerstufe vorgeschlagen, bei der der Signalerzeugerstufe (16) ein Dampfungsglied (21) zugeordnet ist. Dieses Dampfungsglied hat die Aufgabe, bei Lastsprungen durch die Tragheit der Stauklappe verursachte sogenannte Uberschwinger im Ausgangssignal zu dampfen und fehlerhafte Kraftstoffzumessungen zu vermeiden. Zwei Beispiele fur Dampfungsglieder sind angegeben, die beide aus RC-Kombinationen in Verbindung mit einer Diode bestehen und bei denen die gespeicherte Kondensatorladung die Dampfung des Ausgangssignals der Signalerzeugerstufe ubernimmt.