Coralistas amadores: auto-imagem, dificuldades e sintomas na voz cantada

Purpose: to evaluate vocal self-perception, difficulties and presence of negative symptoms after singing of amateur choir singers of different vocal classifications, age and experience. Method: one hundred and twenty five singers answered a questionnaire containing identification data, information about self-perception of the singing voice, difficulties with singing and negative symptoms after singing. Results: the comparison considering vocal classification evidenced greater difficulties with high notes for altos and basses, greater difficulty regarding the transition to high notes for basses and greater vocal fatigue for altos. Comparing the singers by age, both adults and young adults referred more breathiness than the elderly. The adults referred better vocal intensity than the young adults. The young adults referred better timbre than adults. Regarding the experience, the less experienced singers reported self-perception of hoarseness and presence of hoarseness after singing in greater number than the experienced singers. Conclusion: the difficulties with singing are connected to the vocal classification and do not depend on age or experience. Vocal symptoms are related to the vocal classification and to the experience with singing. Negative self-perception is also related the vocal classification and to the experience with singing, and positive self-perception was more reported by experienced singers.

A swirler stabilized combustion chamber for a micro-gas turbine fuelled with natural gas

Micro-gas turbines are a good alternative for on-site power generation, since their operation is very reliable. The possibility of operating with various fuels increases versatility and, as a result, the usage of these devices. Focusing on a performance improvement of a tri-fuel low-cost micro-gas turbine, this work presents investigations of the inner flow of its combustion chamber. The aim of this analysis was the characterization of the flame structure by the temperature field of the chamber inner flow. The chamber was fuelled with natural gas. In the current chamber, a swirler and a reversed flow configuration were utilized to provide flame stabilization. The inner flow investigations were done with numerical analysis, which were compared to experimental data. The analysis of the inner flow was done with numerical simulations, which used the RSM turbulence model. A β-PDF equilibrium model was adopted to account for the turbulent combustion process. Different models of heat transfer were compared. Thermal radiation and specially heat conduction in the liner walls played significant roles on results.

Numerical simulation of an ethanol turbulent spray flame with RANS and diffusion combustion model

A detailed numerical simulation of ethanol turbulent spray combustion on a rounded jet flame is pre- sented in this article. The focus is to propose a robust mathematical model with relatively low complexity sub- models to reproduce the main characteristics of the cou- pling between both phases, such as the turbulence modulation, turbulent droplets dissipation, and evaporative cooling effect. A RANS turbulent model is implemented. Special features of the model include an Eulerian– Lagrangian procedure under a fully two-way coupling and a modified flame sheet model with a joint mixture fraction– enthalpy b -PDF. Reasonable agreement between measured and computed mean profiles of temperature of the gas phase and droplet size distributions is achieved. Deviations found between measured and predicted mean velocity profiles are attributed to the turbulent combustion modeling adopted