1,721,110 research outputs found
Experimental investigation of the internal flow field of a meso-scale whirl combustor
No full textIn the last decade the interest towards the development of small-scale power generation and propulsion systems based on combustion has grew up. One of the essential requirement to succeed in the development of such micro-power systems is the capability to design very efficient small-scale combustion chamber.
At the Politecnico di Milano a research work on a non-premixed centimeter scale (meso-scale) swirl combustor delivering about 100 W of thermal power has been carried out. The use of a tangential air injection along with a 90° impinging fuel jet has been used to achieve good combustion efficiency and flame stabilization over a wide range of operating parameter. The whirl motion should induce a recirculation zone which improve combustor performances, nevertheless actually no experimental data are available about the internal flow field and its relationship with the combustor performances. The experimental investigation of the internal flow field of the combustor has been carried out by means of laser Doppler velocimetry (LDV). Due to limitation in optical access only the radial and tangential component have been measured. Results evidenced that the vortex core is displaced from the geometrical axis and a quite quiescent low velocity region exists in the center of the combustor chamber
A Comparison of a Classical and a Novel Phase Averaging Technique for Quasi-periodic Flows
No full text
Performance of a mesoscale whirl combustor by means of flame chemiluminescence analysis
No full textThe performance of a meso-scale swirl combustor of 6 mm in diameter, 9 mm in height and having a volume of
about 254 mm 3 have been experimentally investigated. The experimental analysis has been carried out in a range of
mass flow rates higher than those considered in previous works. Spectrally resolved global chemiluminescence
emission from the flame have been also monitored and analyzed. Results evidenced that stability limits and
efficiency of the meso-combustor decreased by increasing the mass flow rates, while under lean condition the ratio
of C 2 and CH global chemiluminescence intensity showed to be well correlated with the chemical efficiency
Behavior of hydrogen-enriched non-premixed swirled natural gas flames
No full textThe effects of hydrogen addition on a lean non-premixed natural gas swirl-stabilized flame were investigated. Fuel mixtures containing a volumetric fraction of hydrogen ranging from 0% up to 100% were burnt at ambient pressure with swirled air within a quartz chamber in a co-flow configuration. Tests were carried out keeping the sum of the volumetric fuels flow rate constant; thus, the fuel mixture mass flow rate, input thermal power and equivalence ratio decreased as hydrogen fraction was increased.
The use of hydrogen-enriched natural gas mixtures allowed the burner to operate at overall leaner stable conditions as compared to the case of burning natural gas only; however, an increase in soot, NO x and CO has also been observed. The flame structure was analyzed by still-color photographs and laser sheet visualization; laser Doppler velocimetry (LDV) and
thermocouples were used to analyze the flow field and temperature distributions. Measurements of CO and NO x were obtained by probing the exhaust gases and using gas analyzers, while soot was directly identified by the yellow luminosity in the flame photographs and estimated through spectral analysis of spontaneous flame emission.
The present results revealed that hydrogen addition produced: (1) a shorter and narrowed blue flame located closer to the burner head, (2) a central highly luminous yellow plume extending above the visible blue zone, (3) a deeper fuel jet penetration inside the recirculating bubble, and (4) a monotonic increase of both CO and NO x emissions for H2 fractions ranging from 0% up to 80%. The latter behavior may be due to quenching of CO oxidation, related to the reduction in the size of the reaction zone, while the temperature increase observed near the flame front and close to the burner head promote the thermal NO x production.
The experimental results revealed that hydrogen addition extended the stability limits of a conventional natural gas non-premixed burner and evidenced a significant change in both the flame structure and the flow field. Improved fuel mixture injection strategies should be explored to improve mixing and minimize pollutant production, without affecting flame stability
- …
