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The difficulties encountered in quantitative analysis by gas chromatography are discussed, with particular reference to detection systems. The properties of an ideal detector for quantitative analysis are listed. A description is given of the mode of operation of detectors for gas chromatography, and the extent to which they are suitable for quantitative work is assessed. It was concluded that no one detector possessed all the properties required or an ideal detector. In particular a qualitative knowledge of the sample for analysis was required by all detectors; and calibration was required by the majority of detectors. The extent to which the Brunel mass detector overcomes these limitations was assessed. It is shown that the response of the mass detector depends solely on weight changes caused by adsorption of materials eluted from the chromatographic column thus completely eliminating the need for calibration and qualitative information. The response of the detector is integral, so that the problems associated with peak area measurement do not arise. The sensitivity of the detector is of a similar order to conventional hot wire detectors. The detector gave a quantitative response to all materials analysed, covering a wide boiling range: the upper limit was determined by the maximum column operating temperature, and the lower limit by the extent to which the detector was cooled. The detector responded quantitatively to water. At room temperature the detector responded on a qualitative basis to organic and inorganic gases. The detector was used for the calibration of other detector, and was operated in conjunction with the Martin gas density balance to determine the molecular weights of eluted materials.

This master`s thesis summarizes methods of measurement of natural gas density used in natural gas flow measuring system during transport and distribution of the gas. Concretely the direct measurement of natural gas density by gas density transducer and methods of determining natural gas density using pTZ methods. Experimental part is focused on effect of ambient temperature on value of measurement by gas density transducer.

A study of exhaust gas composition at various engine speeds, loads, and cooling water temperatures was made on an International Harvester UD-6 Diesel Engine. Simultaneously, smoke density was measured with a smokemeter, the principle of which was based on the obstruction of light. Exhaust gases were analyzed with a Fisher Precision Gas Analyzer. The components analyzed were carbon dioxide, oxygen, illuminants, carbon monoxide, hydrogen, and methane. The results of this study have led the investigators to the following conclusions. 1. The exhaust gas composition was chiefly a function of fuel-air ratio. 2. The effect of cooling water temperature on exhaust gas composition was not conclusive over the range of temperature investigated. (120 to 160 degrees Fahrenheit) 3. The so-called “chilling of direct oxidation reactions” were experienced at maximum brake horsepower check. 4. Smoke density increased with an increase in fuel-air ratio at ratios above .04. The cooling temperature effect was negligible. 5. There was a relationship between smoke density and free, or unburned carbon in the exhaust. 6. A higher precision method of gas analysis would be required for any study of the mechanics of combustion inside the combustion chamber. / Master of Science

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Le développement actuel des moteurs doit répondre à une volonté de réduction de la consommation et à des normes de plus en plus sévères. Les moteurs Diesel, bien que performants, présentent des émissions trop importantes d'oxydes d'azote (NOx) et de particules de suies. Ces émissions polluantes proviennent essentiellement de l'existence de zones riches en carburant ne permettant pas une combustion optimale. La préparation du mélange air / carburant, fortement conditionné par l'entraînement d'air par le spray est donc essentielle. La Vélocimétrie par Images de Particules sur traceurs Fluorescents, associée à un traitement spécifique des champs de vitesses instantanés de la phase gazeuse externe sont utilisés afin d'obtenir des mesures en proche frontière du spray. Dans la zone quasi statique du spray, un effet important de la densité ambiante sur le taux de mélange est mis en évidence. D'autre part, la diminution du diamètre de trou d'injecteur améliore sensiblement le taux de mélange local. Pour compléter cette analyse, un gain du taux de mélange entre les deux injecteurs est calculé pour chaque densité ambiante. Pour les fortes densités, le gain issu de la réduction du diamètre de trou peut at! teindre une valeur importante (> 60%). La phase gazeuse latérale dans la zone instationnaire du spray est ensuite investiguée et la méthodologie de la F-PIV est transposée à cette zone. Un lien entre la longueur de pénétration du spray et des longueurs d'entraînement est défini. La densité ambiante n'a pas d'effet sur ces longueurs d'entraînement. La diminution du diamètre de trou engendre une augmentation du gaz entraîné à une distance plus courte du nez de l'injecteur. Cependant, cette étude montre que les deux sprays n'engendrent pas un entraînement de gaz similaire. / The actual development of the engine must reply to a will of fuel consumption reduction and to stricter norms concerning the pollutant emissions. Although the Diesel engines are competitive, the NOx and soot particle emissions mainly come from the existence of wealthy fuel zone preventing an optimal combustion. Therefore, the air / fuel mixing preparation, highly controlled by the air entrainment in spray, is essential. Particle Image Velocimetry on fluorescent tracers, associated with a specific processing of the instantaneous velocity fields have been applied to obtain measurements in the near vicinity of the spray edge. In the "quasi- teady" region of the spray, the important effect of the ambient density on the mixing rate has been pointed out. On the other hand, an orifice diameter decrease significantly improves the local air / fuel ratio. To complete this analyse, a gain in mixing rate between two different injectors has! been calculated for each gas density. For high densities, the gain due to a reduction of the hole diameter can reach important value (> 60%). Then, lateral gaseous phase in no stationary zone of spray is studying and F-PIV method is transposed to this zone. A link between the penetration length and entrainment lengths is defined. Ambient density has not effect on entrainment lengths. The hole diameter decrease generates entrained gas increase at shorter distance of injector nozzle. However, this study shows two sprays do not generated the same gas entrainment

Ces travaux de thèse tentent de répondre à un besoin de surveillance fiable et durable de la concentration d’hydrogène dans un environnement radioactif. Dans ces travaux, nous proposons l’étude et le développement d’un capteur physique d’hydrogène à base de micropoutres résonantes en silicium. La particularité de ce type de capteur vient du fait qu’il ne contient pas de couche sensible et est donc moins sujet au vieillissement que les capteurs chimiques à base de couche sensibles. Compte tenu de la faible masse volumique de l’hydrogène par rapport à celle de l’air et de la bonne sensibilité des micropoutres résonantes aux propriétés physiques du gaz environnant (masse volumique et viscosité), l’utilisation de micropoutres résonantes pour le suivi de la concentration de l’hydrogène dans l’air est tout à fait possible. L’objectif de ces travaux de recherche est l’amélioration de la sensibilité et de la limite de détection de ce type de capteur. Tout d’abord, une étude des méthodes de suivi de faibles variations de la fréquence de résonance a été effectuée. Ceci a permis de déterminer la méthode ayant le meilleur rapport signal sur bruit, permettant ainsi d’améliorer la limite de détection en termes de variation de fréquence de résonance. Dans une seconde partie, une étude de l’influence de la géométrie et des dimensions sur la sensibilité vis-à-vis des variations de la masse volumique du gaz environnant a été réalisée. A l’issu de cette étude, des critères géométriques et dimensionnels permettant l’optimisation de la sensibilité ont été dégagés. D’autres aspects visant à améliorer les performances (sensibilité et limite de détection) de ces capteurs ont été étudiés, comme l’influence du courant d’actionnement et des tensions de polarisation (actionnement électromagnétique et détection piézorésistive) et l’utilisation des modes supérieurs de résonance. Par ailleurs, l’étude de l’influence des paramètres environnementaux (température et pression) sur le comportement des micropoutres résonantes a été établie. / These PhD research tries to meet a need for a reliable and a sustainable hydrogen concentration monitoring in a radioactive environment. In this work, we propose the study and development of resonant silicon microcantilever-based physical hydrogen sensors. The special feature of this sensor is that it does not contain any sensitive and consequently the reliability is improved, compared to devices with sensitive coating. In view of the low density of hydrogen compared to that of air, and the good sensitivity of a resonant microcantilever to the physical properties of the surrounding gas (density and viscosity), the use of vibrating uncoated microcantilever for monitoring hydrogen concentration in air is therefore possible. The objective of this research is to improve the sensitivity and the limit of detection of such sensors. First of all, a study of methods for monitoring small changes in resonant frequency has been conducted in order to determine the method having the best signal to noise ratio, thus, allowing improvement of its resolution in terms of resonant frequency variation measurement. In a second part, a study of the influence of microcantilever geometries and dimensions on their sensitivity to the gas density variation has been performed. As a result, geometrical and dimensional criteria for optimizing the sensitivity to the gas density have been identified. Other factors in a view of improving performance (sensitivity and detection limit) of vibrating microbeams have been studied, such as the influence of the actuating current and bias voltages (electromagnetic actuation and piezoresistive detection) and using high resonant modes. Furthermore, the study of the influence of environmental parameters (temperature and pressure) on the sensors behavior has been established.

The paper presents new results concerning the influence of the gas density and porous plug diameter on the nature of liquid steel stirring with an inert gas in the ladle. The tests were carried out on a cold model of a 30t ladle using particle image velocimetry (PIV) with a high-speed camera to analyse the plume zone formed during the supply of argon and helium as a stirring gas. The similarity criteria for the investigation of stirring processes in cold model in the past were discussed and compared. The modified Morton number was used in this paper to relate the gas flow rate in the model with real objects. The presented results constitute complete documentation of the influence of the plug diameter and gas density on the size of formed gas bubbles and the velocity of gas bubbles rising in different zones of the plume, plume, and spout geometry, including the expansion angle, spout height, open eye area, and gas hold-up.