Combustor Design Trends for Aircraft Gas Turbine Engines

1996 ◽  
Author(s):  
G. J. Sturgess
Keyword(s):  
Gas Turbine ◽  
Considerable Importance ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Enabling Technology ◽  
Commercial Aircraft ◽  
Combustion Dynamics ◽  
Performance Trends ◽  
Air Mixing

Advanced performance trends are surveyed for possible future gas turbine engines to power several classes of military and commercial aircraft. The resulting combustor trends are enumerated. Examples of enabling technology are given. Combustion considerations are discussed, and many commonalities between applications are discovered; fuel/air mixing and combustion dynamics emerge as topics of considerable importance.

Fuel Interchangeability for Lean Premixed Combustion in Gas Turbine Engines

2008 ◽  
Author(s):  
Don Ferguson ◽  
Geo. A. Richard ◽  
Doug Straub
Keyword(s):  
Natural Gas ◽  
Dynamic Response ◽  
Gas Turbine ◽  
Turbine Engines ◽  
Nox Emissions ◽  
Gas Turbine Engines ◽  
Lean Premixed Combustion ◽  
Combustion Dynamics ◽  
Rijke Tube ◽  
Fuel Blends

In response to environmental concerns of NOx emissions, gas turbine manufacturers have developed engines that operate under lean, pre-mixed fuel and air conditions. While this has proven to reduce NOx emissions by lowering peak flame temperatures, it is not without its limitations as engines utilizing this technology are more susceptible to combustion dynamics. Although dependent on a number of mechanisms, changes in fuel composition can alter the dynamic response of a given combustion system. This is of particular interest as increases in demand of domestic natural gas have fueled efforts to utilize alternatives such as coal derived syngas, imported liquefied natural gas and hydrogen or hydrogen augmented fuels. However, prior to changing the fuel supply end-users need to understand how their system will respond. A variety of historical parameters have been utilized to determine fuel interchangeability such as Wobbe and Weaver Indices, however these parameters were never optimized for today’s engines operating under lean pre-mixed combustion. This paper provides a discussion of currently available parameters to describe fuel interchangeability. Through the analysis of the dynamic response of a lab-scale Rijke tube combustor operating on various fuel blends, it is shown that commonly used indices are inadequate for describing combustion specific phenomena.

Computer-Aided Manufacturing of Laminated Engineering Materials (CAM-LEM) and its Application to the Fabrication of Ceramic Components Without Tooling

1997 ◽  
Author(s):  
James D. Cawley
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Solid Freeform Fabrication ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Enabling Technology ◽  
Freeform Fabrication ◽  
Design Changes ◽  
Ceramic Components ◽  
Engineering Materials

Advanced ceramics such as alumina, silicon carbide and silicon nitride (monolithics and composites) have properties that suggest application in gas turbine engines. However, the production of components from these materials is very different from that typical of superalloys and this has limited the range of applications for ceramics in gas turbines. The manufacturing freedom offered by the recently developed technologies termed “rapid prototyping,” RP, or equivalently, “solid freeform fabrication,” SFF, may enable a much wider range of applications to be served in the future. RP was developed to allow production of form-and-fit models without the need for tooling and has proven to be a key assel in the design of new components as well as for the implementation of design changes to existing ones. Direct SFF using engineering materials to prototype components is undergoing continued development and is expected to provide an enabling technology that promises to change design philosophies for components made from ceramics (and other powder-based materials). In this paper, the opportunities for SFF in gas turbine applications are discussed, a brief state-of-the-art overview of RP and its application to engineering ceramics is provided, and a particular process, CAM-LEM, is highlighted.

Active Combustion Control by Fuel Forcing at Non-Coherent Frequencies

2007 ◽  
Author(s):  
Chukwueloka O. Umeh ◽  
Leonardo C. Kammer ◽  
Corneliu Barbu
Keyword(s):  
Gas Turbine ◽  
Pressure Fluctuations ◽  
Open Loop ◽  
Turbine Engines ◽  
Nox Emissions ◽  
Gas Turbine Engines ◽  
Combustion Control ◽  
Combustion Dynamics ◽  
Loop Control ◽  
Active Combustion Control

One impediment to substantially further the reductions in NOx emissions for aviation gas turbine engines is thermal-acoustic instabilities, also referred to as combustion dynamics. Dynamics arise due to the coupling of heat and pressure fluctuations in such systems. Numerous passive and semi-active control schemes, including performance de-rating and fuel staging, have been developed for land-based gas turbine engines. However, many of these schemes are not well suited to aviation engines, as a result of their weight and bulk. Observations of several combustors operating on either gaseous or liquid fuels show that the dominant dynamic frequencies have a special relation to specific non-coherent lower frequencies. Experiments show that combinations of two of these non-coherent frequencies form the dominant tones of the combustor. As part of NASA’s intelligent engines program, active combustion control is used to mitigate dynamics, as the combustor’s bulk fuel-air ratio (FAR) is made leaner in an effort to reduce NOx emissions by about 85% below the Committee on Aviation Environmental Protection (CAEP) 6 limit. In the feedback control scheme suggested in this paper, a small percentage of the overall fuel flow is pulsed at a given non-coherent frequency and with varying amplitude. The effectiveness of the dynamics reduction approach has been demonstrated via preliminary open loop control tests on a liquid-fuelled partially premixed high-pressure combustion test rig at GE Aviation in Evendale, Ohio.

CO Emission and Combustion Dynamics Near Lean-Blowout in Gas Turbine Engines

2004 ◽  
Author(s):  
S. Menon
Keyword(s):  
Gas Turbine ◽  
Flame Length ◽  
Pollutant Emission ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Combustion Dynamics ◽  
Lean Blowout ◽  
Power Operations ◽  
Model Adjustment ◽  
Full Power

Lean-Blowout (LBO) is a phenomenon that occurs in both land-based premixed and propulsion liquid-fuelled gas turbine engines when the effective equivalence ratio is reduced close to the lean flammability limit. Small perturbations in the flame or flow can result in local quenching that can subsequently lead to total extinction (LBO). Prediction of pollutant emission (e.g., CO) and combustion dynamics near LBO is very complicated since physics at many interacting scales have to be resolved. Here, LES studies of both premixed and liquid-fuelled gas turbine engines are reported using a subgrid linear-eddy mixing (LEM) model. In the premixed study, comparison is made with a thin-flame model and it is shown that the flame length can be changed by adjusting the parameters in this model, whereas the flame length is actually predicted in the LEMLES approach. Results of spray combustion in a full-scale liquid-fuelled gas turbine are also discussed for startup and full power operations. It is shown that the LEMLES is able to anchor the flame at the proper location without requiring any model adjustment.

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