Dynamics and stability of lean-premixed swirl-stabilized combustion

Plasma assisted combustion: Dynamics and chemistry

Fuel droplet vaporization and spray combustion theory

Ignition of turbulent non-premixed flames

Flame acceleration and transition to detonation in ducts

Reflecting the developments in gas turbine combustion technology that have occurred in the last decade, Gas Turbine Combustion: Alternative Fuels and Emissions, Third Edition provides an up-to-date design manual and research reference on the design, manufacture, and operation of gas turbine combustors in applications ranging from aeronautical to po

Gas Turbine Combustion: Alternative Fuels and Emissions, Third Edition

The influences of main dimensions and operating conditions of simplex swirl atomizers on the thickness of the annular liquid film formed at the discharge orifice are examined. A general expression for film thickness is derived which, when compared with the experimental measurements reported in the literature, shows very satisfactory agreement over wide ranges of atomizer dimensions and liquid injection pressures. When measured values of Sauter mean diameter (SMD) are plotted against the corresponding values of liquid film thickness t, a relationship between SMD and t is obtained which corresponds closely to the results of previous studies on both airblast and simplex atomizers. The analysis also leads to the development of correlations for flow number and discharge coefficient in terms of the main nozzle dimensions. Predictions of flow number and discharge coefficient based on these equations show satisfactory agreement with the experimental results reported in the literature.

Internal flow characteristics of simplex swirl atomizers

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NO{sub x}), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultralow NO{sub x} has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultralow emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas-turbine-generated pollutants and their mechanisms of formation are described, along with related environmental risk and various issues concerning emissions regulations and recently enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impact so these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basicmore » approaches to the design of dry low-NO{sub x} and ultralow-NO{sub x} combustors are reviewed.« less

The Role of Fuel Preparation in Low-Emission Combustion

The atomizing performance of a novel type of injector is investigated. Essentially, the injector comprises a plain-orifice atomizer with means for injecting air or gas into the liquid upstream of the final discharge orifice. Measurements of mean drop size and drop-size distribution are made using a Malvern spray analyzer. The liquid employed is water, and all tests are carried out at normal atmospheric pressure. Water injection pressures are varied from 34.5 to 690 kPa (5 to 100 psid) and air/liquid ratios from 0.002 to 0.022 by mass. The results obtained with injector orifice diameters of 0.8,1.6, and 2.44 mm show that good atomization can be achieved using only small amounts of atomizing gas at injection pressures down to 34.5 kPa (5 psi). The system appears to have considerable potential for practical applications in which the available gas and liquid pressures are low and in which small holes and flow passages cannot be employed owing to the risk of plugging by contaminants in the liquid.

Spray characteristics of aerated-liquid pressure atomizers

This thesis reports the results of a detailed programme of research on airblast atomization carried out using a specially
designed atomizer in which the liquid is first spread into a thin sheet and then exposed on both sides to high velocity air.
The primary aim of the investigation was to examine the influence of air and liquid properties on atomization quality. The work
was divided into four main phases:-
(1) The first phase was confined to the effects of liquid properties, namely viscosity, surface tension and density on mean drop size. Special liquids were
produced to study the separate effect of each property on atomization quality. They presented a range of values of viscosity from 1.0 to 124 centipoise, while surface tension and density were varied between 26 and 73.5 dynes/cm and 0.8 and 1.8 gm/cm3 respectively. Atomizing air velocities covered the range of practical interest to the designers of continuous combustion
systems and varied between 60 and 125 m/sec.(2) To obtain experimental data on the influence of air properties, notably air density, on mean drop size, the air temperature was varied between 23 and 151°C at atmospheric pressure in one series of experiments, while a separate study on the effect of air pressure on atomization quality was undertaken, where tests were
conducted at constant levels of air velocity and temperature, using a range of liquid flows from 5 to 30 gm/sec, at various levels of air pressure between 1 and 8.5 atm.
(3) In order to provide a comprehensive picture of airb1ast atomizer performance over a wide range of conditions the
separate effects of varying air velocity, liquid flow rate, and hence atomizing air/liquid mass ratio on SMD were examined. This study enabled a better understanding
of the effects of changes in operation on the atomizer's performance.
(4) In all three phases above, velotities of both inner and outer atomizing air streams were kept equal. This last phase was aimed at studying the effect of varying the
velocity between the inner and outer air streams. Best atomization quality was achieved when 65% of the total atomizing air was flowing through the outer stream.
A detailed description of the light-scattering technique for drop size measurement is included. A discussion on the
importance of the results obtained and their direct relevance to the design of airblast atomizers is given.
A dimensional analysis and inspection of all the data obtained on the effects of air and liquid properties on atomization quality showed that over the following range of conditions:
Liquid viscosity 1.0 to 44 centipoise
Liquid surface tension 26 to 73.5 dynes/cm
Liquid density 0.78 to 1.5 gm/cm³
Air velocity 70 to 125 m/sec
Air temperature 20 to 151 °c
Air pressure 1.0 to 8.5 kgf/cm² .
Air/liquid ratio 2 to 6
Cont

/pdf/the-influence-of-air-and-liquid-properties-on-airblast-88cl0tgcc2.pdf

Arthur H. Lefebvre

Papers

Gas Turbine Combustion: Alternative Fuels and Emissions, Third Edition

Internal flow characteristics of simplex swirl atomizers

The Role of Fuel Preparation in Low-Emission Combustion

Spray characteristics of aerated-liquid pressure atomizers

The Influence of Air and Liquid Properties on Airblast Atomization