This study cooperated the KOH anisotropic etching with the laser machining to fabricate small sonic nozzles in the shape of a pyramidal convergent inlet followed by a conical diffuser with a divergent angle of 5°. Three different diffuser lengths were made for the nozzles. The throat diameters were around 100 µm. Experiments were performed to obtain discharge coefficients and critical back pressure ratios in Reynolds numbers ranging from 5.8 × 10² to 4.5 × 10³. The critical back pressure ratio for one of the nozzle type examined reached 0.486 at Re = 4.4 × 10³. Numerical simulations were also implemented to discover the flow fields at an upstream pressure of 203 kPa. The simulation results revealed that, besides flow separation, the first set of oblique shocks appeared in the nozzle jet could lead to tremendous pressure loss. The weaker of the oblique shocks, the higher the critical back pressure ratio would be obtained.

Because of the low uncertainty and very good long term stability the application of critical nozzles became very important especially for test rigs. The majority of nozzles are used in the so-called “suck mode” using atmospheric air as test medium. In order to use nozzles for the generation of different flow rates as well as to generate gas flows with different kinds of gases the application with increased input pressure became more important. An other field of extended application is the usage for small flow rates. Nozzles which have a shape in accordance to ISO 9300 are available with throat diameters down to 80 µm. Below this value the shapes have to be simplified. Even for simplified shapes the mechanical manufacturing of nozzles allows at the time being throat diameters of d = 15 µm.
In order to extend the flow rates to values smaller than the flow rates possible with a single nozzle the use of two nozzles in series is a possible approach. The paper shows that the properties of nozzles, especially the very high reproducibility, is the main precaution for this solution.
The paper will describe an arrangement of two micro nozzles in series. The throat diameters are d₁ = 15 µm and d₂ = 25 µm, respectively. The generated flow rates are compared with LFE measurements. The main source of uncertainty is the reproducibility of the pressure transducers. A nozzle bridge and its potential to decrease this source of uncertainty will be proposed and discussed.
Gas mixtures for the calibration of sensors are usually manufactured by gravimetric methods. The so called dynamic generation is based on the mixture of two ore more flows of gas components with known flow rates. The arrangement of two nozzles in series is an interesting approach for two-component mixtures. The flow rate of the main component is given by the flow rate of the upstream nozzle. The second component is inputted at the connection point of the two nozzles. The amount of this additional flow can be determined by the pressure change at the inlet of the second nozzle. The application of two nozzles in series for generating nitrogen-methane mixtures will be described using a third nozzle for calibrating the mixing unit. In order to get experience with this kind of application the generated mixtures were compared with measurement results of a commercially available gas analyser. The results show the feasibility of this kind of application.

In calibration technique validation, reliability and the traceability of all are very important issues during operation. According to the currently applied rules the traceability or Key Comparison (KC) usually takes place every three-six months. But it’s also obvious, that in the case of relocation KC needs to be performed immediately. For such KC the so-called Youden-Analysis was used, which made the collection of very acceptable results at this ambiance possible.

Generally the construction costs of a calibration facility for hydrocarbons are very high and it is difficult to cover every kind of hydrocarbon and all flow rate ranges required at industry. So far, at the primary standard in Japan, the calibration liquids are limited to kerosene and light oil, in spite of the demands from the industry for other hydrocarbons such as gasoline and heavy oil. Therefore the expansion techniques from the present primary standard to other liquids such as gasoline and heavy oil using flowmeters have been developed. Furthermore the standard flow has expanded to large flow rate range using flowmeters as accurately as possible at calibration laboratories. Consequently the traceability system for hydrocarbon flow using flow standard has been established.

This paper presents a laboratory facility for calibration and testing of flow meters and measurement systems components for oil and liquid petroleum derivatives newly built in Brazil. The laboratory is installed in a fully air-conditioned four floors building with a total area of 700 m². The set of flow meter working standards is composed of two five path ultrasonic meters and two Coriolis master meters, calibrated by the laboratory reference standard, an especially designed 6 tons diverting type gravimetric system. The measurement uncertainties attainable with the test facility lie between 0.04 % and 0.05 % depending on the flowrate and the product used for the tests. The calibration and testing lines were designed to allow the assembling of pipes up to 16 inches diameter and straight pipes runs up to 35 meters long capable of delivering well conditioned flow profiles to the meters, as well as enabling the assemblage and reproduction of practically any type of non-ideal pipe configuration used in custody transfer stations or metering skids installed onshore and in offshore platforms. Three types of oils with low, medium and high viscosity are used to simulate the operation of flow meters and components with different products. Additionally, an electronic temperature control system stabilises the test oil temperature to precisely define its viscosity during a test or calibration, making possible the simulation of the original operating conditions of the metering system in the field. Furthermore, based on its unique characteristics and capabilities, installation and operating conditions can be stressed to a maximum to evaluate the performance of metering systems under such non-ideal circumstances. The laboratory infrastructure is complemented by a trucked mobile calibration unit composed of an 18" compact prover associated to an 8" helical turbine master meter that enables meter provings to be performed at their own operating location. The laboratory was conceived with the main purpose of building not only a traditional flowmeter calibration laboratory, but also an installation capable of carrying out tests and researches in order to assure the accuracy and reliability of the metrological activities performed under the fiscal, legal and commercial scopes, fulfilling the needs of the Brazilian oil industry and the national regulatory bodies.