Abstract
The thermal usage of liquid fuels implies their combustion, which is a process strongly influenced by the performance of the atomizer, which disrupts the fuel into drops of the required sizes. The spray quality of the twin-fluid atomizers with internal mixing (IM-TFA) is primarily influenced by the two-phase flow pattern inside the mixing chamber. We studied the performance of the four types of the IM-TFA nozzles by the optical diffraction system (Malvern Spraytec) to answer the question of how the mixing chamber design influences the spray quality at low atomizing gas consumption. We tested the effervescent atomizer in outside-in-liquid (OIL) and outside-in-gas (OIG) configurations, the Y-jet nozzle and new nozzle design, and the CFT atomizer when spraying model liquids with the viscosities comparable to the common fuels (μ=60and143 mPa· s). We found that the effervescent atomizer performance was strongly influenced by the configuration of the inlet ports. Although the OIL configuration provided the best spray quality (D32 = 72 μm), with the highest efficiency (0.16%), the OIG nozzle was characterized by unstable work and poor spray quality. Both the devices were sensitive to liquid viscosity. The Y-jet nozzle provided a stable performance over the liquid viscosity spectrum, but the spray quality and efficiency were lower than for the OIL nozzle. Our findings can be used to improve the performance of the common IM-TFA types or to design new atomizers. The results also provide an overview of the tested atomizers’ performances over the wide range of working conditions and, thus, help to define the application potential of the tested nozzle designs.
Highlights
The combustion of liquid fuels is a process of high industrial importance
Drop size is an important marker of spray quality, atomization efficiency is relevant for an evaluation of the energy consumption of the entire technological process
We examined four atomizers, spraying two highly viscous liquids with a set of operating conditions to provide a comparison of their spraying abilities in order to define the advantages, disadvantages and potential applications for the spraying of liquid fuels
Summary
The combustion of liquid fuels is a process of high industrial importance. Even when the number of oil-burning furnaces is continuously reduced due to environment protection reasons, it still takes place in furnaces in central heating systems or industrial furnaces. The spray quality worsens rapidly when internal flow changes to the plug or slug regime [10] This fact contradicts to the requirement for efficient work, as the annular flow is usually linked with high gas content in the mixture. We were able to achieve annular internal flow with the OIL device and good spray quality even with lowest gas consumption, while the performance of the OIG nozzle was poor at the same working regimes due to the plug/slug internal flows. The internal flow of this device is created by injection of liquid into a high-speed gas stream In contrast to this atomizer, the OIG and the OIL nozzles (Figure 1b) use fluid-mixing at low velocities. This makes its design more compact and suitable for applications where a small atomizer body is required
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