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A new combustion system, which consists of an evaporator and a tubular flame burner with multi-stage inlets, has been developed to meet the growing concerns over the fuel flexibility and flame stability of gas turbines. In the evaporator, a flash-boiling atomization technology was adopted to enhance atomization, evaporation, and fuel-air mixing to...
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... Mie scattering light came from scattering of liquid droplets ( Yang et al. 2013;Zeng et al. 2012; Zigan, Trost, Leipertz 2016), it is reasonable to use the intensity of Mie scattering (represented by color in Figure 6) as the indicator for the residual quantity of liquid phase in the spray. The experiment conditions for validation of flash boiling effects on atomization and evaporation are presented in Table 1. ...Context 2
... Mie scattering light came from scattering of liquid droplets ( Yang et al. 2013;Zeng et al. 2012; Zigan, Trost, Leipertz 2016), it is reasonable to use the intensity of Mie scattering (represented by color in Figure 6) as the indicator for the residual quantity of liquid phase in the spray. The experiment conditions for validation of flash boiling effects on atomization and evaporation are presented in Table 1. ...Similar publications
A general multi-component model is presented here that builds on currently available models to include non-ideal vapour liquid equilibrium (VLE) and internal droplet liquid diffusion. Both of these effects can influence droplet lifetime estimates, particularly when there are oxygenated components in the fuel mixture, as is current industry practice...
Citations
... More intense energy and better heat distribution are achieved by properly controlling the mixing process [2]. Several techniques have been used to control the mixing process and flame stability: swirl [3][4][5][6][7][8], recirculation [9], transverse jets [10], co-axial flow [11,12], bluff-body stratified [2,13], and staged flow [14]. Control of the mixing process also improves the combustion of renewable gaseous fuels [15]. ...
In most practical combustion devices, the actual combustion process occurs within different mixture in-homogeneity levels. Investigating the mixture fraction field upstream of the reaction zones of these flames is an essential step toward understanding their structure, stability, and emission formation. In this study, the mixture fraction fields were measured for turbulent non-reacting inhomogeneous mixtures immediately downstream from the slot burner exit, using Rayleigh scattering imaging. The slot burner had two concentric slots. The inner air slot can be recessed at distances upstream from the exit of the outer fuel slot, allowing various degrees of mixture inhomogeneity. Mixture fraction field statistics and the two-dimensional gradient were utilized to characterize the impact of the air-to-fuel velocity ratio, global equivalence ratio, fuel composition, Reynolds number, and the premixing length on the mixture mixing field, and thus flame stability. These impacts were evaluated by tracking the normalized mean mixture fraction and mixture fraction fluctuation transition across the regime diagram for partially premixed flames. The results showed that the air-to-fuel velocity ratio was the critical parameter affecting the mixture fraction field for the short premixing length. Stability results showed that the level of mixture inhomogeneity mainly influenced the flame stability. High flame stability is achieved if a large portion of the inhomogeneous mixture fraction is within the fuel flammability limits.
... This trapped vapor will produce a radial flow that causes the spray plumes to bend from their original direction and generate the interstitial streams [45]. However, as the spray developed the interstitial streams are no longer exist along with the spray streams are indistinguishable and the spray appears as a single block looks like a full circle due to the perfect collapse of the spray toward the spray center forming a single plume [46,47]. Fig. 17.a shows the effect of the ratio of ambient pressure to saturation pressure (Pa/Ps) on the spray cone angle for the tested fuels. ...
The present study is geared towards the investigation of the impact of fuel temperature, ambient pressure, and fuel properties on the spray characteristics of a 6-hole gasoline direct injector. High speed imaging is employed to verify the spray structural variation of various fuels including iso-octane, gasoline, methanol, and ethanol over wide range of operating conditions in an optical vessel. These structural parameters were correlated to the ratio of the ambient to saturation pressure ratio (Pa/Ps) that represents the superheated degree. At a constant pressure of 150 bar the fuel was injected, and the fuel temperature ranged between 25 and 120 °C, whilst the ambient pressure ranged from 0.1 to 1 bar. The results indicated that for all the fuels, the spray width was reduced, and the adjacent plumes collapsed into single bulk as the (Pa/Ps) decreased. Furthermore, at very low (Pa/Ps = 0.065), the spray getting longer, and for iso-octane the fuel spray shrinkage toward the injector centreline and shaped like a Fish with sharpen spray tip. The spray cone angle for ethanol, methanol, and gasoline was reduced when the Pa/Ps ratio was decreased from 1 to 0.16 with the exception that at Pa/Ps = 0.54 for ethanol the cone angle was increased and then decreased with the reduction of Pa/Ps. Then a massive increase in the cone angle was noticed by reducing the Pa/Ps ratio reduced from 0.16 to 0.065. For iso-octane, the behaviour is chaotic and not follow any specific trend with the reduction of Pa/Ps. Furthermore, the appearance of interstitial streams in the gaps between the original spray streams was noticed at Pa/Ps ratio ≤ 0.28. Phase Doppler data showed for the Pa/Ps ratios of 0.85, 0.54, and 0.28, that the interstellar streams consistently had a lower mean droplets velocity and a very narrow head stage compared to that of spray main streams. Moreover, reducing the Pa/Ps ratios of 0.85, 0.28, resulted in a significant reduction in Sauter mean diameter with approximately 49.5%.
... A model for tangential injection has also been developed to examine the tubular flame characteristics [9]. A variety of configurations from micro-combustor to large size (12 in.) tubular flame burner [10] have been developed to meet industrial demands, including power generation [11][12][13], emissions reduction [14,15], flame stabilization [4] and flame synthesis [16]. ...
This study experimentally examined the response of a lean premixed methane/air swirl tubular flame to the longitudinal acoustic perturbations. Experiments were conducted by varying the acoustic frequency (f0), acoustic power (P0) and inlet air flow rate (QA) to systematically study the acoustic-excited flame dynamics, including the flame stability, flame structure, heat release rate and acoustic pressure fluctuations. The results demonstrated that the lean tubular flame was much sensitive to longitudinal perturbations below 210 Hz. Even at low power of P0, the flame was forced to oscillate intensively when the perturbation was operated in two discontinuous frequency ranges of f0 = 150 - 200 and f0 = 50 - 100 Hz, while a weakened oscillation regime was observed in the middle range of f0 =100 - 150 Hz; a lower frequency (less than 50 Hz) would extinguish the flame. An increase in P0 intensified the flame oscillation under the perturbations of 50 - 100 Hz, and even resulted in flame lift-off and blow off with f0 between 150 and 200 Hz. In comparison to f0 and P0, the effects of air flow rate (QA) seemed to be weaker. The proper orthogonal decomposition (POD) analysis was performed to interpret the contributions from the mean mode and fluctuating axial and circumferential modes that led to combustion instability. It was found that as the energy fraction of the axial mode exceeded 5.0%, the flame lift-off appeared in the lean swirl tubular configuration.
... A model for tangential injection has also been developed to examine the tubular flame characteristics [9]. A variety of configurations from micro-combustor to large size (12 in.) tubular flame burner [10] have been developed to meet industrial demands, including power generation [11][12][13], emissions reduction [14,15], flame stabilization [4] and flame synthesis [16]. ...
... To solve these problems and promote this technology in practical application, a multistage tubular flame (MSTF) burner was proposed by changing the fuel/air mixing mode (Feng et al. 2019). The newly developed burner has one cylindrical tube with two pairs of tangential inlets installed tangentially to the tube, i.e. the burner body. ...
... In this arrangement, the mode of fuel/air mixing has been changed significantly, as shown in Figure 1. From our previous research (Feng et al. 2019), the MSTF burner shows much better flame stability and a wider range of extinction limits compared to the conventional RMTF burners. However, the mechanism behind these combustion characteristics of MSTF burner has not been clarified yet. ...
... The jet fuel was pressurized by a nitrogen-actuated piston accumulator to 5 MPa and preheated to a certain temperature using a pipe heating coil before injected into the evaporator. It has been confirmed in previous work (Feng et al. 2019) that the complete evaporation of liquid fuel can be realized by adopting the flash-boiling technique. ...
To solve problems of the low burn-off rate and the flame instability in a conventional rapidly mixed tubular flame (RMTF) burner and problems of the flashback and the narrow extinction limits in a premixed tubular flame burner, a new fuel/air mixing mode with multi-staged inlets was proposed and applied to a tubular flame burner, called the multi-staged tubular flame (MSTF) burner. To understand the mechanism of the fuel/air mixing mode of MSTF burner and their effects on the combustion, a series of experiments and simulations were carried out in comparison with the RMTF burner, operating on RP-3 jet fuel in this work. High-speed photography was applied to examine the flame characteristics of the two burners based on the flame irradiance intensity and flame morphology analysis combined with statistic methods. The results show that the tubular flames can be established stably without flashback for both two burners in a wide range of equivalence ratios. The lean extinction limits can be extended to a global equivalence ratio as low as Ф g = 0.26 for MSTF burner, while Ф g = 0.40 for RMTF burner. Planar laser induced fluorescence (PLIF) measurements and 3D CFD simulations were also conducted to see the difference in fuel/air distributions for the two mixing modes of MSTF and RMTF burners at cold conditions. One of the findings is that the MSTF burner has better flame stability and wider extinction limits than the RMTF burner. The physics is that there stably forms a fuel-rich zone in the upstream of the inlet section which increase the resident time of rich fuel/air mixtures. The reveal of this mechanism for the multi-staged mixing mode is important as it has swept the main hurdles for the burner to find more applications to the industries.
This study aims to investigate the advantage of using flash boiling atomization as a new method of feedstock injection in suspension plasma spraying (SPS) and compare the results with continuous jet injection at ambient temperature that is currently used in SPS. In conventional methods, clogging is the main obstacle for the injection of suspension with concentrations beyond 40 wt.%. In this work, we demonstrate that flash boiling atomization enables the injection of suspensions with solid concentrations up to 70 wt.%. The chosen suspension was water based, and the average diameter for the dispersed titania particles was 500 nm. Coating characterization, phase composition, deposition efficiency, deposition rate and thickness per pass were investigated for different suspension concentrations. It was shown that using suspensions with high solid contents leads to a significantly higher deposition weight per pass and thickness per pass and results in a different coating microstructure.
This study proposes an efficient technique to burn ethanol spray in an intense swirling air flow and investigates the mechanism of flame lift-off. On the basis of typical tubular burners for gaseous fuels, ethanol spray was axially induced and mixed with the tangentially injected air under room temperature, yielding the ethanol spray tubular flames under various operating conditions. The results show that from an ultra-lean condition of global equivalence ratio of 0.1 to the rich condition, two typical flames, namely attached and lifted tubular flames, were established. Then, the structure of the ethanol spray tubular flame was specified by temperature measurements, OH-PLIF imaging, indicating its overwhelming aerodynamic and thermal stability with low pollutant emissions. Meanwhile, a flue gas analyzer was used to characterize the gas composition in the hot exhaust. It is found that the burner can achieve very low emissions of both CO and NOx, illustrating high combustion completeness under both attached and lifted flame conditions. To give a better understanding and make fully utilization of spray tubular flames, a parametric study was carried out to investigate the effects of the tangentially swirling air flow, the flow rate and oxygen concentration of atomizing gas, and the flow rate of liquid ethanol. Generally, an attached flame is lifted under a higher tangential velocity of air flow; increasing oxygen concentration of the atomizing gas flow leads to the height decrease of the flame lift-off, even the reattachment of the lifted flame; by raising the ethanol flow rate to exceed a critical value, the flame also lifts off. Furthermore, the evaporation time of droplets, residence time and chemical reaction time were calculated to quantify the flame lift-off behavior. The lifted flame can be established only when the evaporation time is larger than both the reaction time and the residence time.
