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Experimental Investigation of Asphaltene Precipitation
Published in Francisco M. Vargas, Mohammad Tavakkoli, Asphaltene Deposition, 2018
A. T. Khaleel, F. Wang, E. Song, M. Tavakkoli, F. M. Vargas
Acoustic resonance technique (ART) is based on measuring the response of a fluid, contained in a cylindrical cavity, to applied acoustic stimulation. This nonoptical technology can be used to get an insight on fluid phase behavior or phase transition by studying the state and time evolution of the resonance response of the fluid with changes in pressure, volume, or temperature. It applies to any single-phase fluid. Thus, it applies to crude oils of any type and color (Sivaraman et al. 1998; Kabir et al. 2002). This technique has shown success in measuring the upper AOP onset by some researchers (Sivaraman et al. 1998; Jamaluddin et al. 2001; Kabir et al. 2002; Akbarzadeh et al. 2007). ART uses a PVT cell that is thermally insulated using an air bath. The PVT cell is equipped with an acoustic transducer that transmits sound waves through the fluid. On the other end of the PVT cell, an acoustic receiver detects the generated resonance, where the layout of these standing waves depends on the nature of the fluid and its state. Thus, on changing the pressure, temperature or composition of the system, to induce asphaltene precipitation, the variations in the resonance detected will indicate the onset point (Sivaraman et al. 1998; Jamaluddin et al. 2001).
Basics of Resonance
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
Acoustic resonance phenomenon in an acoustic system that amplifies the sound whose frequency matches with one of the natural frequencies of the system is termed as resonant frequency. Usually, there exist several resonant frequencies for an acoustic system. The change in mass, conductivity, elasticity, and the dielectric properties of the resonant system changes the values of resonant frequencies. This property supports the sensing application using acoustic waves. The acoustic waves generated at the surface of the system are termed as surface acoustic waves, while if these are produced in the bulk of the system then they are called as bulk acoustic waves. In the case of optical sensors, coupling of SP waves and surface acoustic waves is used (Friedt and Francis 2016). For example, in biosensing applications using this configuration, the binding of analyte molecules with the active sites present at the recognition medium causes change in the optical and mechanical properties of the sensing unit. The change in the optical properties is detected by SPR by observing the shift in resonance wavelength/angle in the output spectra, while the change in mechanical properties is detected by observing the change in resonant frequency. Thus, by combining both the phenomena, a highly sensitive sensor can be achieved as it evaluates the actual binding of analytes with the recognition sites.
Introduction
Published in J. R. Coaton, A. M. Marsden, Lamps and Lighting, 2012
While electronic ballasts for fluorescent lamps have been available for a decade or more, electronic ballasts for high-intensity discharge lamps (HID) have only found uses in specialist applications. One of the reasons is that HID lamps can become unstable when driven at frequencies above 1 kHz. This instability is referred to as acoustic resonance. Above this frequency, instantaneous changes in lamp power cause fluctuation in the plasma temperature. Due to the direct relationship between gas temperature and pressure, these temperature fluctuations excite pressure fluctuations and the resulting pressure waves distort the arc. As the arc of the discharge is constrained between the two electrodes, standing waves can be set up (analogous to an organ pipe). Acoustic resonance effects are extremely dynamic and unpredictable; one or two cycles at the appropriate frequency is sufficient to extinguish the arc. Additionally, changes in the shape of the arc alter the chemical balance of the discharge and can result in changes to the lamp’s colour, light intensity and electrical characteristics.
Investigation of combustion instability of propane fuel enriched with oxygen under acoustic enforcement
Published in Petroleum Science and Technology, 2023
Acoustic enforcement that has importance with regard to combustion instability increases the originality of the article. As stated in the experimental section, firstly according to abrupt fluctuation in dynamic pressure, natural acoustic resonance of the combustion chamber was determined. The natural acoustic resonance frequencies are 110, 175 and 330 Hz. Flame images are present in Figures 5–7 under different acoustic excitations at different oxygen ratios. Opon flame, acoustic enforcement in three different acoustic excitations was performed. First of all, propane burned with standard air. The flame was then subjected to acoustic enforcement at 110, 175, and 330 Hz, respectively. Flame brightness increased for all mixtures with increasing oxygen ratio. Under acoustic enforcement, flame height shrank and flame expanded in the radial direction in all mixtures. Propane has a high burning rate compared to natural gas due to its high hydrogen rate. The burning rate increased with oxygen addition. It is clear to understand from images in 24% and 27% under unforced condition. In the first acoustic enforcement (110 Hz), the flame was exposed to more acoustic excitation in terms of dynamic pressure. Flame height decreased significantly during the first acoustic enforcement compared to the second and third acoustic enforcements.
Diffusion Combustion of a Hydrogen Microjet at Variations of its Velocity Profile and Orientation of the Nozzle in the Field of Gravitation
Published in Combustion Science and Technology, 2019
Victor V. Kozlov, Valentin V. Vikhorev, GenrichR. Grek, Yury A. Litvinenko, Andrey G. Shmakov
Experimental data on diffusion combustion of subsonic propane and hydrogen microjets are reported in the works by Kozlov et al. (2013,2015) and Grek et al. (2013). The diffusion combustion of round and plane hydrogen microjets forced transversally by acoustic waves were examined in the work by Kozlov et al. (2014a). As a result, the flame bifurcation was observed in both flow configurations. This phenomenon looks much similar to the flame behavior at the diffusion combustion of propane microjets excited transversally by acoustic oscillations (Kozlov et al., 2014b). The acoustic effect on the emission of nitric oxides and the stability of detached flame of a turbulent hydrogen jet was the focus in the work by Jeongseog Oh et al. (2009). It was shown that the emission of NOx is reduced at the acoustic resonance. Then, Munki Kim et al. (2009) dealt with the dynamics of turbulent flame in the near field of hydrogen jet at the acoustic forcing matching the resonant frequency of a coaxial air flow. The emission of NOx was reduced by 25% as compared to the unforced jet at the same velocity ratio of the coaxial air flow and the jet. The bifurcation of attached flame of round and plane methane microjets was observed in the work by Suzuki et al. (2007). Recently, the splitting of round microjet forced by acoustic waves was found in the case of flame detached from the nozzle exit. Also, we note that the mechanism of bifurcation of the round-jet flame subject to external acoustic oscillations is still not clear (Suzuki et al., 2007 and Krivokorytov et al., 2012).
Structural optimization scheme for acoustic cloaking structures considering general surfaces
Published in Engineering Optimization, 2022
For the sake illustrating DSHS-based metamaterials, Figure 1(a) shows a unit structure of the DSHS acoustic metamaterial above a flat plate and the phase shift curve computed by finite element simulation. The acoustic resonance frequency of the DSHS structure is tuned to the frequency of the incoming wave, in this case 1700 Hz. Utilizing the phase shift of the wave, cloaking of the surface can be achievable (Faure et al.2016). The values of the phase shift make it possible to determine the geometric parameters of the unit cell and realize the cloaking. In other words, by posing one unit cell or multiple unit cells as a metasurface above a rough surface, extraordinary wave reflection can be realized.