Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report October 1 1994 December 31 1994 written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report October 1 1996 December 31 1996 written by and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The viability of matching hydrodynamic conditions in a hot bubbling fluidized bed (BFB) combustor and a cold BFB model are being evaluated. Similitude parameters are being matched in a 20.32 cm diameter BFB combustor and a 5.08 cm diameter cold BFB. In addition, tests are planned to investigate the effect loaded solids above the L-valve have on the flow rate.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Quarterly Technical Progress Report January 1 1995 March 31 1995 written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 774 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report July 1 1995 September 30 1995 written by and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report October 1 1995 December 30 1995 written by and published by . This book was released on 1996 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimentation was conducted to determine the nature of bubbling fluidized bed (BFB) pressure fluctuations. The goal of the experiments was to explain the physical phenomena that governs the structure of pressure fluctuations. A study of the effect of the differential pressure tap spacing was conducted. The results confirmed the hypothesis that spatial aliasing can significantly distort expected fluctuation structure. The behavior of bubbling bed fluctuations was compared to previously published theories that predicted the natural frequency of incipiently fluidized beds. A modified theory was derived for fluidized systems which better predicts the observed frequency in shallow fluidized beds. This theory not only predicts the natural frequency of bed oscillations, but also explains the second order system behavior observed in bubbling fluidized bed Bode plots. The effect of bubble coalescence in deep bed acts both to decrease the frequency of bed oscillations and to complicate the observed frequency response with multiple peaks.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report January 1 1996 March 31 1996 written by and published by . This book was released on 1996 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Additional pressure fluctuation data was recorded from the ISU power plants two CFB boilers. Absolute pressure fluctuations were measured immediately above the distributor nozzles and near the top of the CFB boilers. The fluctuations measured near the bottom of the bed exhibit a highly oscillatory (0.25-0.3 Hz) phenomena. This {open_quotes}square wave{close_quotes} pressure signal is observed at all times of the day and under different boiler loadings. Steps were taken to insure that abasing was not the cause of the observed pressure dynamics. It is hypothesized that these fluctuations are the result of the coal feed system, and are not related to the CFB hydrodynamics. Pressure fluctuations measured near the top of the bed do not show this dominant periodic behavior attributed to the coal feed system. The Bode plots of pressure fluctuations in this region show a near -40 dB/decade roll-off and a cornering frequency of around 0.07 Hz. This result suggests that the pressure dynamics in industrial scale CFBs may be governed by a wave phenomenon similar to that observed in the laboratory scale circulating fluidized beds. This result cannot be confined until more is known about the boiler control dynamics, and more extensive boiler instrumentation is available.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1995 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report July 1 1996 September 30 1996 written by and published by . This book was released on 1996 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: By studying pressure fluctuations using a system identification approach, it is hypothesized that circulating fluidized bed (CFB) pressure fluctuations are indicative of CFB hydrodynamics in two ways. First, the frequency phenomenon that is observed in the lower regions of the CFB under conditions of high solids loading is the result of lower dense bed voidage oscillations. Our results suggest that a surface wave phenomena inversely proportional to the square root of the bed diameter is also be observed in CFB pressure fluctuations under most conditions. By matching revised similitude parameters between two CFBs a number of conclusions can be drawn. First, spectral analysis of pressure fluctuations, if properly applied, can be used to verify that similitude has been achieved. To do this, not only must the Bode plot characteristics important for hydrodynamics be identified, but the pressure fluctuation structure at all elevations of the CFB must be similar. The set of similitude parameters defined by Glicksman is not sufficient to establish hydrodynamic similitude. The solids flux as typically measured in the downcomer does not contain information on the solids hold-up in the riser, or the amount of solids that progress downwards in the annulus rather than exit the riser. It is better to use the total mass contained in the riser as the important ''solids'' parameter for the establishment of similitude, rather than the solids flux. This measurement can be made more accurately, monitored continuously, and is a much simpler measurement to perform in most CFB systems. Even with this new set of dimensionless parameters, the differences in the coefficient of restitution of particle/bed collisions may make a significant difference in the CFB hydrodynamics. The effects of particle collisions with the riser top-plate must be considered in similitude studies.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report April 1 June 30 1995 written by and published by . This book was released on 1995 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first phase of experimentation for the comprehensive similitude study on the two laboratory scale cold-model circulating fluidized beds has been completed. This first phase required the acquisition and analysis of pressure fluctuation data from a 2.0 inch diameter pressurized circulating fluidized bed. The second phase required the matching of each of the 20 experiments in a cold-model twice the size of the smaller 2.0 inch circulating fluidized bed model using similitude relations. Problems of excessive electrostatic buildup were encountered in this second phase. To alleviate these problems, the large model had to be redesigned and reconstructed. The focus of the research this past quarter has been devoted to these modifications. Currently, the new sections have been constructed and the modified circulating fluidized bed is in the process of reassembly. Two related projects were undertaken while the large circulating fluidized bed model was being modified. A bubbling bed was constructed such that pressure fluctuation data could be measured in both bubbling and turbulent fluidization regimes. The purpose of such tests was to relate pressure fluctuation structure in the lower sections of the circulating fluidized bed with phenomena observed in bubbling/turbulent regimes. Two probes designed to measure heat transfer coefficients in the large and small circulating fluidized bed models were completed and initially tested under bubbling bed conditions. These tests insured the validity and accuracy of the bed to surface heat transfer coefficient measurement. The two probes were constructed as an additional means of validating similitude relations in circulating fluidized beds in addition to pressure fluctuations.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds Technical Progress Report April 1 June 30 1996 written by and published by . This book was released on 1996 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The pressure fluctuations in the transition regime between bubbling fluidization and fast fluidization were investigated using system identification techniques. The results show that the voidage waves and surface eruption effects seen in bubbling fluidized beds are also observed in the transition regime fluctuations. In addition, a third frequency phenomenon is observed in the spectrum which is hypothesized to be a surface wave phenomenon analogous to surface waves in water. The validity of previously derived similitude parameters for bubbling fluidized beds (BFB) was investigated using spectral analysis of pressure fluctuations. When BFB similitude parameters are matched in two different beds, the pressure dynamics are similar under most conditions, suggesting that the correct similitude parameters have been defined for BFBs.
Download or read book Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1994 with total page 1144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1975 with total page 996 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scaling of Pressurized Fluidized Beds Quarterly Report July September 1994 written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pressure Fluctuations as a Disgnostic Tool for Fluidized Beds written by and published by . This book was released on 1997 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The validity of using bubbling fluidized bed (BFB) similitude parameters to match a hot BFB to a cold BFB is being studied. Sand in a BFB combustor and copper powder in cold BFB model have been analyzed and found to be out of similitude. In the analysis process, it was determined that the condition of the screen covering the pressure tap affects the quality of pressure data recorded. In addition, distributor plate design and condition will affect the hydrodynamics of the bed. Additional tests are planned to evaluate the validity of similitude concepts in BFB.
Download or read book The Analysis and Modeling of Pressure Fluctuations in a Fluidized Bed written by David Thomas Falkowski and published by . This book was released on 2003 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this research was to evaluate different pressure probe techniques used to measure the pressure fluctuations in a fluidized bed, to determine the effect of bed parameters on the power spectrum, and to develop a second-order model that describes the spectrums. This work's motivation is to increase the knowledge of fluidized bed pressure phenomena and further the understanding of such fluidized bed research areas as similitude, chemical processes, and pressure diagnostic tools. Pressure fluctuations in a fluidized bed were measured with four pressure probe techniques (static-absolute, dynamic-absolute, static-differential, and dynamic-differential) to determine if differences existed. Testing showed that the absolute and differential techniques produced drastically different results under certain conditions. Comparison of dynamic and static techniques showed that their results were very similar in most situations. The probe arm position was an important testing parameter for all techniques. Pressure data at different bed heights, fluidization velocities, particle sizes/densities, and bed temperatures were taken to determine each parameter's effect on the spectrum. The relationship between bed height and dominant frequency agreed with the literature, but secondary peaks were a function of position in the bed and not affected by bed height. Through the Bode plot, the shifting of frequency peaks with fluidization velocity was documented as a continuous growth. Large-diameter, high-density particles (Group D) exhibited harmonic behavior, while small-diameter, low-density particles (Group A) yielded power spectrums with first-order characteristics. For temperatures up to 512°C, spectrums varied little when velocity ratios were kept nearly constant. Multiple-peak phenomena were associated with bubble coalescence, surface effects, and distributor jetting effects. A second-order model that describes the dominant peak's location and magnitude was developed. An equation for the natural frequency as a function of bed height was developed from experimental data and agreed with the literature. An equation for the damping ratio as a function of bed height was developed from experimental data and agreed with a new theoretical damping ratio presented here. Using these equations, the model was developed such that its output was a function of bed height, and the model qualitatively described the experimental spectrums adequately.
