Search results

The purpose of this paper is to explore the ability of capillary‐attached gas sensor (CGS) in detecting components of gas mixtures, including a volatile organic gas and hydrogen in a wide range of concentrations.

Diverse feature extraction and classification techniques were employed to analyze the response of CGS when applied to different mixtures.

It was observed that the response of CGS to the above gas mixtures could be distinguishable. While evaluating the results of the classification technique, it was implied that hydrogen, in the presence of the volatile organic gases, could be detected perfectly by analyzing the response of the CGS. Separating techniques, which yielded a high rate of classification, were used to separate mixtures containing hydrogen and organic gases from other organic gas mixtures without hydrogen.

The results presented in this paper prove the ability of CGS in fabricating an olfactory machine for analyzing the components of gas mixtures.

Under normal conditions, there are different protection objects inside and outside the gas station, so two sets of independent cathodic protection systems are adopted. At the same time, an insulating flange is applied at the position where trunk pipelines access to the gas station, which realizes electrical isolation of the structures inside and outside the station. However, as a result of short distance between the two cathodic protection systems, there will be stray current interference between them. The purpose of this paper was to study on the interference between cathodic protection systems of gas station and long distance trunk pipeline.

Based on the above, in this paper, first, the mathematical model of interference between cathodic protection systems was established and the control equations solved using the boundary element method. Second, the influence of cathodic protection system of gas station on long distance trunk pipeline and the influence of cathodic protection system of long distance trunk pipeline on gas station were studied separately using BEASY software. Finally, a new thought of cathodic protection design for local station was put forward.

It was concluded that there were serious interference problems between the cathodic protection systems of gas station and long distance trunk pipeline. By moving the potential control point to area outside the influence scope of anode ground bed could avoid the influence of cathodic protection system of gas station on long distance trunk pipeline. By moving the auxiliary anodes away from gas station could avoid the influence of cathodic protection system of long distance trunk pipeline on pipelines in gas station. The new thought of cathodic protection design could avoid the interference between the cathodic protection systems effectively.

It is considered that the results can guide cathodic design for gas station and long distance trunk pipeline. The results can also avoid the interference corrosion between the structures in gas station and trunk pipeline.

An approximate graphical method of calculation is presented for evaluation of the flame speed of premixed combustible gases and its relation to the minimum size of burned gas pocket which can propagate a flame. The theory is applied in a semi‐quantitative manner to the problem of the stability limits of a flame anchored to a bluff body in a stream of high velocity gas. Three different approaches to this problem are made, each of which indicates that the velocity of the gas stream at blow‐out should be proportional to the linear dimension of the flame‐holder, the absolute gas pressure, and the square of the laminar flame speed of the combustible gas.

A prototype gas prover was constructed to serve as the Italian primary standard for gas flow rates in the range 0.1 ml/min to 2 l/min. The new prover is used to calibrate high‐quality industrial standards, as well as the MFCs used in microelectronic fabrications and preparation of reference gas mixtures.Design/methodology/approach – The prover measures gas volume transfers caused by displacements of a 120 mm dia. motor‐operated piston, which is introduced into a temperature‐controlled chamber containing up to 3 l of the required working gas at near ambient conditions. Gas delivery is made at constant rate, whereas possibly variable incoming flows are measured at constant pressure. Displacements of the piston are measured by an optical interferometer.Findings – The analysis shows that standard uncertainty ranges between 0.013 and 0.03 percent. Owing to the very accurate control and measurement of both pressures and temperatures, these figures refer equally to volume and mass flowrate. Experimental comparisons with similar national standards at LNE‐France and NIST‐USA confirmed the consistency of measurement results in the three Nations.Research limitations/implications – The gas prover should be used with inert gases only.Practical implications – The national industrial gas standards and the best flow transducers can now be calibrated accurately down to unprecedented flowrate values.Originality/value – The need for measurement of extremely low gas flows is quite recent, therefore possibly less than ten primary national standards are available today worldwide. Several completely different principles and designs have been developed; description of design and performance of each instrument is important to assess their respective merits. The described apparatus is innovative as regards measurement range, accuracy and control techniques.

The output of nearly all non‐dispersive infrared (NDIR) gas sensors deployed in the heating, ventilation, and air conditioning (HVAC) industry today cannot maintain their accuracy specifications within six months to a year. Consequently, all installed NDIR gas sensors must be re‐checked for accuracy over time at great costs. The purpose of this paper is to advance a novel technique for expeditiously recalibrating such installed NDIR gas sensors without the need for using any gas standards.

By recognizing the fact that the calibration curve for absorption biased designed NDIR gas sensors comprises two distinct domains, namely an invariant NDIR absorption physics domain and a variant sensor components characteristics domain. By formulating a novel recalibration procedure which corrects only changes that have taken place in the variant sensor components characteristics domain over time, it is possible to recalibrate the sensor very rapidly and remotely via wireless or infrared means using only the gas concentration level surrounding the sensor as a reasonably accurate gas standard.

Implementation of the currently described recalibration technique to a large number of absorption biased designed NDIR gas sensors has been carried out for over a year in the laboratory. Results of these experiments have unambiguously confirmed the capability and the accuracy of this novel recalibration technique.

The currently presented recalibration technique for absorption biased designed NDIR gas sensors is original and has never been published elsewhere. This technique significantly reduces the maintenance costs, inclusive of labor and material, for installed NDIR gas sensors that require periodic and mandatory accuracy commissioning over time.