Gas Composition Sensor Research Articles

An experimental study: Dependence of Schottky diode parameters on Schottky contact area size

We have investigated whether the Schottky barrier diodes (SBD) parameters such as the SB height and ideality factor (IF) change as a function of Schottky contact (SC) area, in the Pt/n-Si (D1Pt) and PtSi/n-Si (D2PtSi). The SC area ranges from 1.000x10−4 cm2 to 1.600x10−3 cm2. The results of this kind of study can help selection of SC dimensions suitable for many purposes in temperature, pressure and atmospheric gas composition sensors, and switching power, high-power, high-temperature and high-frequency devices. The IF and SB height values from the forward bias I–V curves at 296 K have ranged from 1.036 0.7716 eV for 1.00x10−4 cm2 to 1.013 and 0.7819 eV for 1.60x10−3 cm2 in the D1Pt diodes, respectively and from 1.073 and 0.8619 eV for 1.00x10−4 cm2 to 1.020 and 0.8897 eV for 1.60x10−3 cm2 in D2PtSi diodes, respectively. Thus, it has been seen that the SB height value has raised while the IF value has decreased with an increase in the SC area size. It has been concluded in literature that the increase in the SC diameter reveals decreasing periphery effect and absolute value of the built in electric field.

Characterization and performance of an acoustic sensor for fission gas release characterization devoted to JHR environment measurements

For over a decade, the IES laboratory has been working in collaboration with the CEA on the development of acoustic instrumentation in the nuclear field. As part of this collaboration, the IES acoustics team is developing a miniaturized gas composition sensor for in situ measurements of gas composition in a fuel rod. The first experimental use of an acoustic sensor to measure gas composition dates back to 2010 with the REMORA 3 experiment, which estimated the release of fission gas in an experimental fuel rod. Unlike the sensor tested during REMORA 3, this new sensor should be able to operate at 300°C, a performance made possible by the use of a piezoelectric element based on bismuth titanate (NBT). The material is screen-printed onto an alumina substrate. The manufacturing process and initial characterization were presented in the previous version of ANIMMA 2021 [1]. In this article, we will focus on the performance of this type of sensor by characterizing different gas mixtures representative of the gases inside a fuel rod, in order to estimate relative deviations under laboratory conditions.

Algorithm for Determining the Knock Resistance of LNG

This paper reports the development of a next-generation algorithm to calculate the knock resistance for LNG compositions. This so-called PKI Methane Number is developed and tested for a lean-burn, medium-BMEP gas engine. The algorithm itself is a polynomial equation based on thousands of simulations performed using an experimentally verified engine knock model. Comparison of the PKI MN calculated using the gas-input-only algorithm and measurements on the test engine show very good agreement. A comparison with two existing methods for calculating the methane number (AVL and MWM Method as defined in EN 16726) with experimental engine data show reasonable agreement with predictions using AVL method but substantial differences with predictions from MWM method are observed. Additionally, the current methods such as AVL and MWM need a dedicated solver to calculate the methane number. In contrast, the algorithm described here is a polynomial equation that is very easy to implement in gas composition sensors for fast real-time methane number calculations. This opens possibilities for smart-phone methane number calculation during bunkering and fuel-adaptive control systems that could optimize engine performance for a broad range of fuel compositions. Furthermore, given the experimentally verified reliability and ease of implementation of the PKI MN algorithm, we assert that it is an excellent, open-source candidate for international standards for specifying the knock resistance of LNG.

A miniaturized optical gas-composition sensor with integrated sample chamber

A robust and highly miniaturized optical gas sensor based on optical absorption spectroscopy is presented. By using the resonator cavity of a linear variable optical filter (LVOF) also as a gas chamber, a compact and robust optical sensor is achieved. The device operates at the 15th order in 3.2–3.4μm wavelength range for distinguishing hydrocarbons. The physical cavity length at the μm-level is translated into an effective optical absorption path length at the mm-level by the use of highly reflective (R>98%) Bragg mirrors. The optical design using the Fizeau interferometer approach is described. Moreover, the CMOS-compatible fabrication method is explained. In addition to the wideband and single wavelength filter characterization, absorption of methane in the LVOF cavity is demonstrated at 3392nm and 3416.60nm wavelengths.

Gas Composition Sensor for Natural Gas and Biogas

The calorific value of energetic gasses is an important parameter in the quality assessment of gas steams, and can be calculated from the chemical composition of the gas. An array of capacitive sensor electrodes was developed, each functionalized with a gas responsive coating to measure the concentration of methane, ethane, propane, carbon dioxide, water and nitrogen in various gas mixtures. Using the data from six functionalized chips, the calorific value could be measured with 5% accuracy. Part of this error is caused by the noise in the electronics, another part by the non-linearity of the responsive coatings. Future developments aim at improving the response of the coatings and a higher integration of electrodes and will lead to a higher sensitivity and an expected accuracy of 0.5%. The sensor should be implemented in flow equipment, restricting the size to several cubic centimeters.

Vacuum and Residual Gas Composition MEMS Sensor

The paper presents a MEMS-type vacuum and residual gas composition sensor, which in contrast to the other miniature sensors, works in medium and high vacuum (10−5−10Pa). It operates on the principle of ionization of gases inside a silicon-glass microchamber. Pressure is estimated on the basis of the discharge current value, and gas composition − on the basis of spectra of the glowing gases, recorded by a miniature fiber spectrometer.

Azimuthal polarization for Raman enhancement in capillary waveguides

Hollow, metal-lined capillary waveguides have recently been utilized in spontaneous gas-Raman spectroscopy to improve signal strength and response time. The hollow waveguide is used to contain the sample gases, efficiently propagate a pump beam, and efficiently collect Raman scattering from those gases. Transmission losses in the waveguide may be reduced by using an azimuthally polarized pump beam instead of a linearly or radially polarized pump. This will lead to improved Raman signal strength, accuracy, and response time in waveguide-based Raman gas-composition sensors. A linearly polarized laser beam is azimuthally polarized using passive components including a spiral phase plate and an azimuthal-type linear analyzer element. Half-wave plates are then used to switch between the azimuthally polarized beam and the radially polarized beam with no change in input pump power. The collected Raman signal strength and laser throughput are improved when the azimuthally polarized pump is used. Optimization of the hollow waveguide Raman gas sensor is discussed with respect to incident pump polarization.

Persistent regional carbon dioxide anomalies driven by land use

Researchers have traditionally used measurements from remote locations, such as Hawaii's Mauna Loa Observatory and other isolated stations, to determine atmospheric carbon dioxide (CO2) concentrations and estimate the strengths of various carbon sources and sinks. The prevailing wisdom was that attempts to measure regional differences in CO2 over land would end up with signals that were either so small that they were undetectable or that were dominated by high‐frequency variability due to atmospheric turbulence or weather. Measurements drawn from a moderately dense network of atmospheric gas composition sensors distributed across the upper midwestern United States, however, showed that large regional variations in tropospheric CO2 are readily observable. Drawing on measurements made at nine sensors spread over 400,000 square kilometers between 2007 and 2009, Miles et al. found that seasonal variations in atmospheric CO2 depend strongly on the type of ecosystem lying at the foot of each sensor tower.

State Estimation in the Automotive SCR DeNOx Process

Selective catalytic reduction (SCR) of nitrogen oxides (NOx) is a widely applied diesel engine exhaust gas after-treatment technology. For effective NOx removal in a transient operating automotive application, controlled dosing of urea can be used to meet the increasingly restrictive legislations on exhaust gas emissions. For advanced control, e.g. Model Predictive Control (MPC), of the SCR process, accurate state estimates are needed. We investigate the performance of the ordinary and the extended Kalman filters based on a simple first principle system model. The performance is tested through a series of simulation studies reflecting realistic challenges such as under-modelling and few gas composition sensors.

Relative pressure, temperature, and gas composition sensitivity of damping-based resonant sensors

Measurement of the damping in resonant microsystems and nanosystems has been proposed for measurement of pressure, temperature, and gas composition. Because the damping will be a function of all three of these variables, estimating the sensitivity of these transducers requires modeling the effect each of these variables will have on the damping of the system. Using viscous flow theory, the relative sensitivity of damping to pressure, temperature, relative humidity, and the concentration of selected contaminants is computed. These results show that these sensors are accurate as pressure sensors across a range of conditions. Resonators are accurate as temperature sensors only if the relative humidity is known. Resonators are not accurate as humidity sensors, and are accurate as gas composition sensors only under limited conditions.

Assessment of respiratory activity during surface-mould cheese ripening

The present study deals with the respiratory activity of the microbial consortia established on surface-mould cheese. A software sensor was developed, from a model linking the operating conditions established in the ripening room (temperature, relative humidity, carbon dioxide and oxygen concentration) to the cheese mass dynamic. It estimated the respiratory activity of the microbial consortia based on mass measurement only, without atmospheric gas composition sensors or off-line measurements. After some simplifications of the model, this observer can be seen as an integral Luenberger observer, with analytically defined gain values. This approach was validated on two ripening trials. Relative errors between estimated and calculated (from carbon dioxide and oxygen concentration measurements) respiratory activity were equal to 3.02% and 8.83% for Run 1 and Run 2, respectively.

Theory for a gas composition sensor based on acoustic properties

Sound travelling through a gas propagates at different speeds and its intensityattenuates to different degrees depending upon the composition of the gas.Theoretically, a real-time gaseous composition sensor could be based on measuringthe sound speed and the acoustic attenuation. To this end, the speed of soundwas modelled using standard relations, and the acoustic attenuation wasmodelled using the theory for vibrational relaxation of gas molecules. Theconcept for a gas composition sensor is demonstrated theoretically fornitrogen–methane–water and hydrogen–oxygen–water mixtures. For athree-component gas mixture, the measured sound speed and acousticattenuation each define separate lines in the composition plane of two of thegases. The intersection of the two lines defines the gas composition. Itshould also be possible to use the concept for mixtures of more than threecomponents, if the nature of the gas composition is known to some extent.

An Adaptive Fuzzy Algorithm for Domestic Hot Water Temperature Control of a Combi-Boiler

This paper describes an innovative adaptive fuzzy control (AFC) algorithm for regulating the domestic hot water temperature of a combi-boiler or instantaneous hot water heater when using a domestic hot water flow rate sensor. The AFC automatically learns the feedforward relationship between the domestic hot water flow rate and the gas valve position and adapts to process changes such as variations in the inlet water temperature, controller set point, gas composition, and flow sensor miscalibration without requiring additional sensors or a system identifier. Laboratory tests under typical operating conditions show that the AFC reduces the set-point error between 18% and 70% and reduces control effort between 23% and 41% when compared with a conventional proportional-integral-derivative (PID) feedback controller with feed-forward compensation. The AFC's memory and processing requirements are comparable to those for a PID plus feedforward algorithm, so it is a realistic replacement for a conventional PID algorithm with feedforward compensation.

Fluorescence characteristics of Cu-ZSM-5 zeolites in reactive gas mixtures: mechanisms for a fiber-optic-based gas sensor

In situ measurements of the fluorescence spectra, intensity, and response time were made at elevated temperatures (~500 degrees C) for samples of Cu-ZSM-5 exposed to dilute mixtures of O(2) in N(2) and to various O(2)-reductant combinations in N(2). The results of these experiments are interpreted with a physical model of the oxidation/reduction kinetics of the copper ions. The fluorescence signal depends strongly on the gas composition, providing a mechanism for a gas composition sensor. A prototype sensor configuration is described that uses a visible (488-nm) excitation source and a fiber-optic geometry to generate and detect the fluorescence. The results indicate that for a weakly reducing gas the fluorescence signal correlates well with the oxygen concentration, whereas for strongly reducing gases the signal correlates more closely with the reductant-to-oxidant ratio.