scholarly journals CFD Assessment of a Wet, Low-NOx Combustion System for a 3MW-Class Industrial Gas Turbine

Author(s):  
Peter A. Liever ◽  
Clifford E. Smith ◽  
Geoffrey D. Myers ◽  
Lorenzo Hernandez ◽  
Tim Griffith

A wet low-NOx combustion system being developed for the AlliedSignal ASE40 industrial gas turbine is assessed using advanced 3-D CFD analysis. A PDF combustion-turbulence interaction model was modified to allow analysis of simultaneous injection of water with gaseous or liquid fuel. To the authors’ knowledge, such a CFD analysis is unique in the open literature. Analyses of the wet low-NOx combustion system were performed with and without water injection at full power engine conditions. Good qualitative agreement between engine emission data and predictions was seen. NOx reductions of 58% and 77% were measured for water-to-natural gas mass ratios of 0.5 and 1.0, respectively, compared to 75% and 93% for CFD calculations. Corresponding CO levels were measured to increase by factors of 3 and 9, compared to CFD predictions of 4 and 7. Similar trends were predicted for water injection with DF-2 diesel fuel. Predicted overall flow patterns were not significantly changed with water injection. NOx reductions were caused by a reduction in maximum flame temperatures in the primary and intermediate zones when water was injected. CO increases were caused by a reduction of CO oxidation downstream of the dilution zone (in the turn-around duct) due to lower gas temperatures with water injection.

Author(s):  
Matthew E. Thomas ◽  
Mark J. Ostrander ◽  
Andy D. Leonard ◽  
Mel Noble ◽  
Colin Etheridge

CFD analysis methods were successfully implemented and verified with ongoing industrial gas turbine engine lean premix combustion system development. Selected aspects of diffusion and lean premix combustion modeling, predictions, observations and validated CFD results associated with the Solar Turbines Mars™ SoLoNOx combustor are presented. CO and NOx emission formation modeling details applicable to parametric CFD analysis in an industrial design environment are discussed. This effort culminated in identifying phenomena and methods of potentially further reducing NOx and CO emissions while improving engine operability in the Mars™ SoLoNOx combustion system. A potential explanation for the abrupt rise in CO formation observed in many gas turbine lean premix combustion systems is presented.


Author(s):  
R. A. Wenglarz ◽  
C. Wilkes ◽  
R. C. Bourke ◽  
H. C. Mongia

This paper describes the first test of an industrial gas turbine and low emissions combustion system on coal-water-slurry fuel. The engine and combustion system have been developed over the past five years as part of the Heat Engines program sponsored by the Morgantown Energy Technology Center of the U.S. Department of Energy (DOE). The engine is a modified Allison 501-K industrial gas turbine designed to produce 3.5 MW of electrical power when burning natural gas or distillate fuel. Full load power output increases to approximately 4.9 MW when burning coal-water slurry as a result of additional turbine mass flow rate. The engine has been modified to accept an external staged combustion system developed specifically for burning coal and low quality ash-bearing fuels. Combustion staging permits the control of NOx from fuel-bound nitrogen while simultaneously controlling CO emissions. Water injection freezes molten ash in the quench zone located between the rich and lean zones. The dry ash is removed from the hot gas stream by two parallel cyclone separators. This paper describes the engine and combustor system modifications required for running on coal and presents the emissions and turbine performance data from the coal-water slurry testing. Included is a discussion of hot gas path ash deposition and planned future work that will support the commercialization of coal-fired gas turbines.


Author(s):  
V. Vassiliev ◽  
S. Irmisch ◽  
S. Florjancic

The key aspects for the reliable CFD modelling of exhaust diffusers are addressed in this paper. In order to identify adequate turbulence models a number of 2D diffuser configurations have been simulated using different turbulence models and results have been compared with measurements. An automated procedure for a time- and resource-efficient and accurate prediction of complex diffuser configuration is presented. The adequate definitions of boundary conditions for the diffuser simulation using this procedure are discussed. In the second part of this paper, the CFD procedure is being applied to investigate the role of secondary flow on axial diffusers. Prediction results are discussed and compared with available measurement data.


Author(s):  
Scott Keller ◽  
Afzal Pasha Mohammed ◽  
Khalid Oumejjoud

One of the common issues within the industrial gas turbine fleet is the susceptibility of a can-annular combustors’ fuel manifold cover (support housings) to develop embedded cracks. These cracks, located in the assembly joint of cover plates that create internal passages for fuel delivery to the combustion system, have enough of a driving force to propagate to the surface of the component. Once a crack propagates to the surface, gas has the potential to leak into the enclosure, posing a potential fire and safety risk. Furthermore, cracked fuel manifold covers are prone to increased NOx levels and excessive dynamics. Consequently, operators have the potential for a forced outage due to the failure of the fuel manifold. Currently, the existing solution is to replace the support housings with new or refurbished housings, with prior analyses requiring near perfect fusion. An ultrasonic inspection procedure has been developed to inspect a combustor’s fuel manifold cover for embedded cracks, which are not currently detectable with FPI or X-ray methods. Through this method, the amount of fusion in the assembly joint is readily obtained, including the ability to understand if the crack is partial-thickness or through-thickness. Parametric fracture analyses, utilizing experimental material test data calibrated to service-exposed components, are conducted to predict the residual life. Coupled with the engine operating data, including the use of cold- or heated-fuels, a recommendation for the remaining useful operation of the support housings can be provided. Ultimately, by completing the ultrasonic inspection and analysis on the support housing/fuel manifold, both the risk of an unplanned outage in the future and the lifecycle management cost to the operator is reduced.


Author(s):  
S. Hubbard ◽  
A. P. Dowling

A theory is developed to describe low frequency acoustic waves in the complicated diffuser/combustor geometry of a typical industrial gas turbine. This is applied to the RB211-DLE geometry to give predictions for the frequencies of the acoustic resonances at a range of operating conditions. The main resonant frequencies are to be found around 605 Hz (associated with the plenum) and around 461 Hz and 823 Hz (associated with the combustion chamber), as well as one at around 22 Hz (a bulk mode associated with the system as a whole).


Author(s):  
Kenneth O. Smith ◽  
Leonard C. Angello ◽  
F. Richard Kurzynske

The design and initial rig testing of an ultra-low NOx gas turbine combustor primary zone are described. A lean premixed, swirl-stabilized combustor was evaluated over a range of pressures up to 10.7 × 105 Pa (10.6 atm) using natural gas. The program goal of reducing NOx emissions to 10 ppm (at 15% O2) with coincident low CO emissions was achieved at all combustor pressure levels. Appropriate combustor loading for ultra-low NOx operation was determined through emissions sampling within the primary zone. The work described represents a first step in developing an advanced gas turbine combustion system that can yield ultra-low NOx levels without the need for water injection and selective catalytic reduction.


Author(s):  
H. Matsuzaki ◽  
I. Fukue ◽  
S. Mandai ◽  
S. Tanimura ◽  
M. Inada

This paper describes the cold flow tests and low pressure combustion tests which were conducted for the development of a 1500°C-class low NOx combustion system. In the cold flow tests, the effect of vane angle and the momentum ratio of fuel to air flow on mixing characteristics inside the premixing nozzles was investigated. The stabilization of the flow field inside the combustor was confirmed by measurement of the axial velocity distribution and observations by using a tuft of soft thread. Combustion characteristics in terms of emissions and stability were investigated initially by low pressure combustion tests, and the gas temperature distribution inside the combustor was measured. NOx emissions for a 1500°C-class gas turbine as low as 50ppm at 15% oxygen at design pressure were demonstrated.


Author(s):  
O. C. Schoeppner

Low first cost and little need for maintenance assure the industrial gas turbine an important place for many applications where the lower thermal efficiency as compared with other prime movers is not a decisive factor. The simplicity of the gas turbine finds its best expression in the compact integrated single shaft design featuring a single compressor-turbine rotor supported in two bearings, the whole including the combustion system being contained in a common casing structure. The recognized need for simplicity together with reliability has been the main consideration in the design of the unit presented in the following description. At present, an intensive test program is under way and it is expected that the new Clark gas turbine will soon be ready for installation.


Author(s):  
Urmila C. Reddy ◽  
Christine E. Blanchard ◽  
Barry C. Schlein

Pratt & Whitney has developed a novel water-injected Industrial Gas Turbine (IGT) combustor liner design that has demonstrated significant reduction in CO emissions when compared to typical film cooled combustor designs. The CO reduction demonstrated in a prototype test shows that the CO quenching due to cooler film temperatures near the liner wall is a significant source of CO emissions in a conventional water-injected combustor operating on natural gas fuel. This finding paved the way for a combustor design that reduces CO emissions while still maintaining low levels of NOx emissions. This design also has potential for lower NOx since the low CO emissions characteristic enables increased water-injection. This paper presents the emissions characteristics measured on prototype hardware and the design of the engine hardware for future validation. Significant reduction in gaseous emissions was demonstrated with the testing of a prototype at the United Technologies Research Center in East Hartford, CT. This reduction in emissions compared to the baseline film-cooled design for a given operating condition has many benefits to the customer, including reduced need for exhaust catalyst cleanup and extended operating times while still meeting site permits specified in CO tons per year. Other benefits may include the ability to guarantee lower NOx emissions through increased water injection for the current CO emissions output.


2002 ◽  
Vol 124 (3) ◽  
pp. 489-495 ◽  
Author(s):  
K. Mathioudakis

The effect of water injection in the combustion chamber of an industrial gas turbine is studied by means of analytic relations. Equations for the estimation of changes in the main performance parameters are provided. The relations are derived on the basis of an order of magnitude analysis and taking into account variation of gas properties due to water injection as well as changes in the interrelation of component performance parameters. It is shown that water/fuel ratio is the main parameter on which performance deviations depend. Data from the performance testing of an industrial gas turbine are used to check the validity of the proposed relations. The comparison of the predictions to the test data shows that the mechanisms of performance deviations are well modeled by the analysis presented.


Sign in / Sign up

Export Citation Format

Share Document