Temperature (T) is probably the most fundamental parameter in all kinds of science. Respective sensors are widely used in daily life. Besides conventional thermometers, optical sensors are considered to be attractive alternatives for sensing and on-line monitoring of T. This Review article focuses on all kinds of luminescent probes and sensors for measurement of T, and summarizes the recent progress in their design and application formats. The introduction covers the importance of optical probes for T, the origin of their T-dependent spectra, and the various detection modes. This is followed by a survey on (a) molecular probes, (b) nanomaterials, and (c) bulk materials for sensing T. This section will be completed by a discussion of (d) polymeric matrices for immobilizing T-sensitive probes and (e) an overview of the various application formats of T-sensors. The review ends with a discussion on the prospects, challenges, and new directions in the design of optical T-sensitive probes and sensors.

Luminescent probes and sensors for temperature.

How to effectively utilize low and medium temperature energy is one of the solutions to alleviate the energy shortage and environmental pollution problems. In the past twenty years, because of its feasibility and reliability, organic Rankine cycle has received widespread attentions and researches. In this paper, it reviews the selections of working fluids and expanders for organic Rankine cycle, including an analysis of the influence of working fluids' category and their thermodynamic and physical properties on the organic Rankine cycle's performance, a summary of pure and mixed working fluids' screening researches for organic Rankine cycle, a comparison of pure and mixture working fluids' applications and a discussion of all types of expansion machines' operating characteristics, which would be beneficial to select the optimal working fluid and suitable expansion machine for an effective organic Rankine cycle system.

A review of working fluid and expander selections for organic Rankine cycle

Over the last two decades, our understanding of soot formation has evolved from an empirical, phenomenological description to an age of quantitative modeling for at least small fuel compounds. In this paper, we review the current state of knowledge of the fundamental sooting processes, including the chemistry of soot precursors, particle nucleation and mass/size growth. The discussion shows that though much progress has been made, critical gaps remain in many areas of our knowledge. We propose the roles of certain aromatic radicals resulting from localized π electron structures in particle nucleation and subsequent mass growth. The existence of these free radicals provides a rational explanation for the strong binding forces needed for forming initial clusters of polycyclic aromatic hydrocarbons. They may also explain a range of currently unexplained sooting phenomena, including the large amount of aliphatics observed in nascent soot formed in laminar premixed flames and the mass growth of soot in the absence of gas-phase H atoms. While the above suggestions are inspired, to an extent, by recent theoretical findings from the materials research community, this paper also demonstrates that the knowledge garnered through our longstanding interest in soot formation may well be carried over to flame synthesis of functional nanomaterials for clean and renewable energy applications. In particular, work on flame-synthesized thin films of nanocrystalline titania illustrates how our combustion knowledge might be useful for developing advanced yet inexpensive thin-film solar cells and chemical sensors for detecting gaseous air pollutants.

Formation of nascent soot and other condensed-phase materials in flames

https://backend.orbit.dtu.dk/ws/files/145750384/Nreview_revised.pdf

Modeling nitrogen chemistry in combustion

This paper focuses on the potential use of ammonia as a carbon-free fuel, and covers recent advances in the development of ammonia combustion technology and its underlying chemistry. Fulfilling the COP21 Paris Agreement requires the de-carbonization of energy generation, through utilization of carbon-neutral and overall carbon-free fuels produced from renewable sources. Hydrogen is one of such fuels, which is a potential energy carrier for reducing greenhouse-gas emissions. However, its shipment for long distances and storage for long times present challenges. Ammonia on the other hand, comprises 17.8% of hydrogen by mass and can be produced from renewable hydrogen and nitrogen separated from air. Furthermore, thermal properties of ammonia are similar to those of propane in terms of boiling temperature and condensation pressure, making it attractive as a hydrogen and energy carrier. Ammonia has been produced and utilized for the past 100 years as a fertilizer, chemical raw material, and refrigerant. Ammonia can be used as a fuel but there are several challenges in ammonia combustion, such as low flammability, high NOx emission, and low radiation intensity. Overcoming these challenges requires further research into ammonia flame dynamics and chemistry. This paper discusses recent successful applications of ammonia fuel, in gas turbines, co-fired with pulverize coal, and in industrial furnaces. These applications have been implemented under the Japanese ‘Cross-ministerial Strategic Innovation Promotion Program (SIP): Energy Carriers’. In addition, fundamental aspects of ammonia combustion are discussed including characteristics of laminar premixed flames, counterflow twin-flames, and turbulent premixed flames stabilized by a nozzle burner at high pressure. Furthermore, this paper discusses details of the chemistry of ammonia combustion related to NOx production, processes for reducing NOx, and validation of several ammonia oxidation kinetics models. Finally, LES results for a gas-turbine-like swirl-burner are presented, for the purpose of developing low-NOx single-fuelled ammonia gas turbine combustors.

Science and technology of ammonia combustion

Studies of aromatic hydrocarbon formation mechanisms in flames: Progress towards closing the fuel gap

On surface temperature measurements with thermographic phosphors: A review

Effects of a sampling quartz nozzle on the flame structure of a fuel-rich low-pressure propene flame

Several temperature measurement techniques were compared for the investigation of fuel-rich, premixed, flat, low-pressure flames of propene, acetylene, and cyclopentene with maximum temperatures around 2400 K. Vibrational Stokes/anti-Stokes Raman measurements with a KrF excimer laser using CO, H2, and H2O as temperature indicators were examined at 50 and 200 mbar for different flame stoichiometries. Also, laser-induced fluorescence (LIF) of OH in the A-X band was used, and complementary lifetime measurements were performed to account for a variation of fluorescence quantum yield with rotational quantum number. LIF using seeded NO (0.2–1.0%) was applied both in point-wise and 1D temperature measurement in spite of the anticipated interaction of NO with the fuel-rich flame chemistry. Furthermore, thermocouple measurements were performed in the preheat zone. These techniques were compared with respect to accuracy and the potential for routine applications under fuel-rich low-pressure conditions.

Temperature measurement in fuel-rich non-sooting low-pressure hydrocarbon flames

Laminar premixed flat cyclopentene/oxygen/argon Barnes with different stoichiometries (C/O = 0.6. 0.77, and 0.94) were studied at 50 mbar under fuel-rich non-sooting conditions. This study was motivated by the scarcity of information on C-5 fuel combustion which is ill contrast with the potential importance of C-5 species reactions in benzene formation. Concentrations as a function of height above the burner were measured for more than 30 stable and radical species using molecular beam mass spectrometry Temperature was measured in the unperturbed flame with laser-induced fluorescence of seeded NO. Stable species concentrations in the burned gases were found in good agreement with equilibrium calculations. For information on the flame structure in the reaction zone, species profiles for intermediates of relevance in the formation of aromatics were inspected regarding in particular several CxHy compounds with 2 less than or equal to x less than or equal to 10. The measured data was analyzed with respect to the formation of C-6 species, in particular of benzene as a key species in the soot formation mechanism. A reaction flow analysis has been performed which reveals striking differences to other fuels, including acetylene and propene. It does not seem feasible to rely on a single dominant pathway to benzene in cyclopentene flames. Reactions of C5H5 and C5H6 were found of importance, that of C5H6 + CH3 being of similar influence on C6H6 formation as the propargyl recombination, a result of interest for detailed flame modeling.

Burak Atakan

Papers

Studies of aromatic hydrocarbon formation mechanisms in flames: Progress towards closing the fuel gap

On surface temperature measurements with thermographic phosphors: A review

Effects of a sampling quartz nozzle on the flame structure of a fuel-rich low-pressure propene flame

Temperature measurement in fuel-rich non-sooting low-pressure hydrocarbon flames

Fuel-rich flame chemistry in low-pressure cyclopentene flames