A robust and reliable optical trace oxygen sensor

This paper describes recent progress towards the development and qualification of a highly distributed, multi-point, all optical pressure and temperature compensated, fiber optic oxygen sensor (FOxSense™) system for closed-loop monitoring and safety of the oxygen ullage environment inside fuel tanks of military and commercial aircraft. The alloptical FOxSense™ system uses a passive, multi-parameter (O2/T&P) fiber optic sensor probe with no electrical connections leading to the sensors install within the fuel tanks of an aircraft. The all optical sensor consists of an integrated multi-parameter fiber optic sensor probe that integrates a fuel insensitive fluorescence based optical oxygen optrode with built-in temperature and pressure optical optrodes for compensation of temperature and pressure variants induced in the fluorescence response of the oxygen optrode. The distributed (O2/T&P) fiber optic sensors installed in the fuel tanks of the aircraft are connected to the FOxSense optoelectronic system via a fiber optic cable conduit reaching to each fuel tank in the aircraft. A multichannel frequency-domain fiber optic sensor read-out (FOxSense™) system is used to interrogate the optical signal of all three sensors in real-time and to display the fuel tank oxygen environment suitable for aircraft status and alarm applications. Preliminary testing of the all optical fiber optic oxygen sensor have demonstrated the ability to monitor the oxygen environment inside a simulated fuel tank in the range of 0% O2 to 40% O2 concentrations, temperatures from (-) 40°C to (+) 60°C, and altitudes from 0-ft to 40,000-ft.

This paper presents the development of a novel luminescence-based trace oxygen sensor that will eventually lead to the production of a commercial sensor for use in gaseous sensing applications. The proprietary sensing formulation provides the means of a robust and stable sensor using a metalloporphyrin complex as the luminescent indicator that is efficiently quenched by oxygen. The spectroscopic properties of the oxygen sensitive layer have been carried out and appropriate optical components and electronics sourced and built into a low cost, compact, miniaturized device. This novel oxygen sensor operates in the 0-10,000 parts per million (ppm) range and offers an alternative to traditional trace oxygen sensors, such as galvanic electrochemical, zirconia and other luminescence-based ppm sensors.

Underground Coal Gasification is a method used to convert underground coal seams into a gaseous product commonly called synthetic gas through a flammable chemical process without going through a conventional mining process. The UCG concept was first developed in England which was then continued by the Soviet Union in field trials of UCG which was used as a power plant. In Indonesia, Tekmira has begun to research UCG, but there are very few publications on UCG. Therefore, it is necessary to conduct research on laboratory scale UCG for analysis of gas products to support the study of renewable energy. UCG testing begins with sample preparation followed by laboratory-scale coal gasification testing. There is a sample of coal used in the test, namely Subbituminous Coal from Tanjung Enim, South Sumatra. Initial combustion is carried out by flowing propane gas into the reactor tube using a burner. Furthermore, a mixture of oxygen gas and compressed air is used to keep the coals burning. After obtaining the gas from the combustion, then gas sampling is carried out using a suction pump which will be stored in a tedlar gas bag. Combustion gas products will be checked for syngas concentration using a Gas Chromatography tool to determine the concentration of CH4, CO2 and O2 gases. From the tests that have been carried out, the gas concentrations of O2 are 3.67%, CO2 41.51%, and CH4 6.93%. Coal in the confined test conditions has good conditions with indications of seeing the concentration of CH4, O2, and CO2 gas.

Preparation of a high stability optical fiber oxygen sensor based on the bilayer sensitive membrane

Fast pesticide detection inside microfluidic device with integrated optical pH, oxygen sensors and algal fluorescence

Air-fuel ratio, a major parameter of petrol engineer, directly affects the power, economy and indicators of exhaust emission of engine. To make the air-fuel ratio in the best state, the air flow entering into cylinder must be measured accurately. Due to gaseous property of air itself, the flow detection is greatly interfered by temperature and pressure. In the article, we used surface acoustic wave(SAW) technique combined with temperature and pressure compensation and made a detection device for engine intake, which was less interfered by temperature and pressure with high accuracy and wide measuring range. The paper introduced the working principle of SAW air flow sensor and its mathematic model, and discussed the development, signal detection and error processing of sensor. The results showed that SAW sensor could better overcome the interference of temperature and pressure, and then accurately got the air flow value of engine with preferable repeatability and reliability.

The moisture content was a key factor affecting the permeability of the sintering granulation and the bed layer, and it promoted denitrification and combustion. This study investigated the influence of moisture content on denitrification, bed permeability, and the emissions of O2 and CO in the sintering process through industrial trials on-site. By analyzing sintering reaction mechanisms and SPSS data, and combining CHEMKIN simulation, the mechanism of moisture content on NO emissions during sintering was obtained. The results showed that the moisture content of the sintering mixture could affect the emission of NO in the sintering flue gas by influencing the permeability of the bed and the O2 and CO in the flue gas. As the moisture content of the mixture increased, the NO content in the sintering flue gas first decreased and then increased, while the permeability and CO content showed an initial increase followed by a decrease, and the volume fraction of O2 in the flue gas gradually decreased. Eight factors, including permeability index, O2 concentration, CO concentration, negative pressure, water vapor volume fraction, flue gas temperature, sintering trolley speed, and dust concentration, were significantly correlated with NO emissions, and a generalized linear model with NO emissions as the dependent variable was established. For a specific sintering industrial production, the moisture content of the sintering mixture determined the permeability. Apart from O2 concentration, permeability had the greatest impact and was negatively correlated with NO emissions. Water vapor in the flue gas could promote the CO-NO reaction, and the higher the water vapor volume fraction, the higher the reduction rate of NO, but excessively high levels were detrimental to permeability. Taking into account the permeability of the sintering bed, O2 and CO in the flue gas, the optimal moisture content (mass fraction) of the sintering mixture for denitrification during the sintering process ranged between 6.71% and 8.04%. In actual industrial sintering production, a water vapor volume fraction in the flue gas between 16% and 18% was most favorable for denitrification during the sintering process. These findings provided theoretical references for denitrification processes during sintering.

Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica

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OPTIMALIZATION OF OXYGEN LEVELS IN ROOT SYSTEMS AS EFFECTIVE CULTIVATION TOOL

Li-CO2/O2 battery operating at ultra-low overpotential and low O2 content on Pt/CNT catalyst

The typical response characteristics of most optical oxygen sensors include downward curving Stern–Volmer plots and often multi-exponential luminescence decay profiles in the absence and presence of oxygen. The wide range of different response features exhibited by optical oxygen sensors is usually attributed to different degrees of heterogeneity in the sensor films. This heterogeneity is described in this paper by a log-Gaussian distribution in the natural luminescent lifetime of the oxygen-quenchable lumophore, τo, and the quenching rate constant, kq. A ‘log-Gaussian distribution in τo and kq’ model is used to generate theoretical response profiles which exhibit the same disparate range of features as real optical oxygen sensors. However, unlike other models, such as the ‘two-site’ model, the ‘log-Gaussian distribution in τo and kq’ model generates model parameter values which are physically plausible and consistent at all partial pressures of oxygen, pO2. The model is used to fit successfully the Stern–Volmer plots and luminescent decay profiles reported for a number of different optical oxygen sensors. For each of the real sensors examined, the values of the model parameters KSV,mdl, ρ1, ρ2 and τo,mdl which give the best fit to the observed data are reported. The latter data allows prediction of the response features of the associated optical oxygen sensor at any value of pO2

Sterilization is a physical or chemical process that eliminates microbial life from a surface, equipment, medication, etc. Because of the severity of the process to meet the sterilization criteria and definition there is no singular sterilization applicable to all healthcare and other products including drugs, polymers, devices and materials. The sterility of sensors used in medical applications, for biochemical investigations, operation of biotechnological reactors, etc., is a necessary but difficult-to-achieve prerequisite for the use of sensors. There is a lack of reliable data about effects of different sterilization procedures on optical sensors. Therefore, the influences, effects and compatibility of diverse sterilization procedure on optical polymer oxygen sensors were investigated. Before and after sterilization, the absorption/emission spectra and the response of the sensor to different concentrations of oxygen were measured and Stern–Volmer plots were calculated. Based on the obtained results from measurements the compatibilities of the different sterilization procedures and polymer oxygen sensors were determined.

Optical fiber evanescent wave sensor for oxygen deficiency detection

The paper analyzes the dielectric breakdown properties of N2–O2 mixtures at different O2 concentrations and gas pressures, taking into account electron detachments from negative ions. The reduced effective ionization coefficients α(eff)/N in N2–O2 mixtures at different O2 concentrations and gas pressures were calculated and analyzed, by considering electron detachments. The critical reduced electric fields (E/N)cr and the critical electron temperature Tb were then determined. The result indicates a clear enhancement of α(eff)/N by collisional detachments, which causes a reduction in the (E/N)cr. In addition, a synergistic effect in the N2–O2 mixture was also observed in both (E/N)cr and Tb. The value of Tb was decreased by the increase of pd product, however, Tb tended to be constant at relatively high pd products.