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[en] The conventional background-oriented schlieren (BOS) technique is an image-based technique that can calculate the density field in fluids using two static images [i.e., an undistorted background image (reference image) and a distorted background image due to the density change in fluids (target image)]. This paper proposes the smartphone BOS (SBOS) technique, which offers the measurement of the density gradient using the high-speed imaging feature of the smartphone being carried with a moving observer. The conventional BOS with a fixed camera visualizes the density gradient by comparing the reference image and the target image. In contrast, SBOS can obtain the time difference of the density gradient field. A reference image in SBOS is a target one at a previous time step. The movement of the smartphone is canceled using a registration technique for image accurate alignment. Three demonstrations are conducted to perform SBOS. First, in a static situation, the density field of heated air by a gas burner is visualized by comparing between SBOS and conventional BOS. Second, the local displacement of density field and the error displacement is estimated quantitatively when the smartphone is moving. Third, SBOS using an embossed wallpaper to visualize the density field is performed in the mobile condition. These achievements suggest that SBOS is an effective system to visualize the density field using only the smartphone, and is expected to be a useful tool such as a preliminary experiment in the laboratory and a teaching tool for general smartphone users.
[en] Estimation of operating conditions for fossil fuel boiler heat exchangers is often required due to changes in working conditions, design modifications and especially for monitoring performance and failure diagnosis. Regular heat exchangers in fossil fuel boilers are composed of tube banks through which water or steam flow, while hot combustion (flue) gases flow outside the tubes. This work presents a top-down approach to operating conditions estimation based on field measurements. An example for a 350 MW unit superheater is thoroughly discussed. Integral calculations based on measurements for all unit heat exchangers (reheaters, superheaters) were performed first. Based on these calculations a scheme of integral conservation equations (lumped parameter) was then formulated at the single tube level. Steady state temperatures of superheater tube walls were obtained as a main output, and were compared to the maximum allowable operating temperatures of the tubes material. A combined lumped parameter - CFD (Computational Fluid Dynamics, FLUENT code) approach constitutes an efficient tool in certain cases. A brief report of such a case is given for another unit superheater. We conclude that steady state evaluations based on both integral and detailed simulations are a valuable monitoring and diagnosis tool for the power generation industry
[en] Mean velocities and turbulence characteristics in the swirling flow of a gun-type gas burner (GTGB) were measured with a triaxial hot-wire probe (T-probe) and compared with previous data measured with an X-type hot-wire probe (Xprobe). Vectors and axial mean velocity data obtained by the measurement of the two types of probes in the horizontal plane and in the cross section differ in magnitude, but have very similar shape in overall distribution. Axial mean velocity components show especially wide differences around the slits and outer part of the swirl vanes within the range of X/R=2. Also, various turbulence intensities appear in a similar trend to axial mean velocity components within the range of X/R=2. The radial component of turbulence intensity around the slits and the outer part of swirl vanes above the range of X/R=2 has an opposite phenomenon. On the whole, the T-probe's measurements appear smaller than the X-probe's. This shows that the X-probe is better than the T-probe, especially on the swirling flow because it is much easier to use
[en] Economy calculations are nearly exclusively made by computers. Undisputed advantage is apart from the high speed in which even complex calculations are made the 'document character' of the printout. Disadvantageous is that apart from the soft manufacturer almost nobody knows the calculation formulations, basic assumptions and logical connections. One can only accept the result without being able to prove the 'correctness'. There is also hardly the possibility to gain knowledge as the reason for certain results is not explained. Based on known terms of boiler economy many questions arising in practice can be answered with sufficient accuracy. Excessive accuracy is with the many unknown or only estimated operating data anyhow not reasonable. (orig.)
[de]Wirtschaftlichkeitsbetrachtungen werden fast nur noch per Computer durchgefuehrt. Unbestrittener Vorteil ist neben der schnellen Ausfuehrung komplexer Berechnungen der 'Dokumenten-Charakter' des Ausdrucks. Nachteilig ist, dass ausser dem Software-Hersteller kaum jemand die Rechenansaetze, Grundannahmen und logischen Verknuepfungen kennt. Das Ergebnis muss man akzeptieren, ohne die 'Richtigkeit' nachvollziehen zu koennen. Man hat auch kaum die Chance, etwas an Erkenntnis hinzuzugewinnen, da die Ursachen fuer bestimmte Ergebnisse nicht aufgedeckt werden. Ausgehend von bekannten Begriffen der Kesselwirtschaftlichkeit, koennen viele in der Praxis auftauchende Fragen ausreichend genau beantwortet werden. Eine uebertriebene 'Genauigkeit' ist bei den vielen unbekannten oder nur schaetzbaren Betriebsdaten sowieso nicht angebracht. (orig.)
[en] A new style of oil burner has been developed for use on exploration platforms offshore. The design improves oil combustion through enhanced air induction, producing stable flames in the clean burn region which do not generate smoke and oil fallout. Successful tests have led to it now being ready for commercial exploitation. (UK)
[en] In order to realize liquid (oil etc.) atomized and to improve the combustion efficiency, the atomization or adding moisture is required by atomized nozzle in the oil burner and some power driven thrusters. Based on physics model and some suitable hypothesizes, the 3-D mathematical models for rotary atomized nozzle with micro-expanded tangent channel at low pressure are presented, and the same time, the various simulation tests are taken with the k-ε/RNG models and SIMPLE method, the tests results shown: The angle(Θ) of the micro-expanded tangent channel plays an important role for the fluid characteristics, if Θ<0, the circum-fluence at the exit of the nozzle is obviously, and Θ>0, the solid cone in nozzle are formed easily, but its energy loss is bigger. While the initial pressure p0=0.3 Mpa, Ux,0=0, Uy,0=0, Uz,0=-0.2 m/s, the circum-fluence at the exit of the nozzle is not exactly formed with Θ=5.8 and the energy loss is reduced and the atomized angle can get 80 deg.. The nozzle can be widely adequate to the medium atomized instrument about the oil burner and some power driven thrusters. (authors)
[en] The feasibility of determining the location of a metal target within a gas flame with the aid of a laser rangefinder was theoretically analysed. The effect of the gas flame composition and the combustion regime on the optical parameters of the flame, on the possibility of extracting the signal from the target against the background of the signal reflected from the flame, and also on the accuracy of determination of the target location inside the flame is taken into account.
[en] A new gas burner developed by Radian Corporation and manufactured by Todd Combustion can attain NOx emission levels of less than 10 ppm. By going back to the fundamentals of the combustion process, it has come up with a burner which gives NOx levels previously attainable only with selective catalytic reduction. (author)
[en] This study aims to develop a low-temperature catalytic burner using propane and toluene alternately as a fuel and to apply it to the drying of acrylic coatings on textiles. Pt catalysts deposited on ceramic fibres (Al2O3) were employed. For propane, the diffusive catalytic burner was used. The combustion efficiency of the diffusive catalytic burner deteriorated rapidly when it was installed in downward position. Two concepts of forced diffusion combustion and premixed combustion were introduced to improve the downward placed diffusive catalytic burner. The combustion efficiency was enhanced with these modifications, but the forced diffusion was preferred since premixed combustion raised the temperature of the catalyst above 700degC leading to sintering of the catalysts. For the toluene catalytic burner the premixed combustion mode was adopted. Its optimum operation conditions were obtained by analysing the temperature within the catalyst layer and by adjustment of the toluene mixture. Field tests were performed on the drying acrylic coatings using the catalytic burners. The results showed that the use of catalytic burners had several benefits such as energy savings and less pollutant emissions. (Author)
[en] The use of the natural gas in the rational combined production of electrical energy and heat for space heating or industrial processes allows a relevant energy saving and a decrease in the air pollution level as a direct consequence of lower fuel consumption. This article surveys natural gas fired cogeneration systems marketed in Italy and provides brief notes on their relevant technical/economic and normative aspects