Combustion of alternative fuels in vortex trapped combustor Chaouki Ghenai a,⇑ , Khaled Zbeeb a , Isam Janajreh b a Ocean and Mechanical Engineering Department, College of Engineering and Computer Science, Florida Atlantic University, Boca Raton, FL 33431, United States b Masdar Institute of Science and Technology, Abu Dhabi 54224, United Arab Emirates article info Article history: Available online xxxx Keywords: Combustion Alternative fuels Trapped vortex combustor CFD Mixture fraction/pdf model abstract Trapped vortex combustor represents an efficient and compact combustor for flame stability. Combustion stability is achieved through the use of cavities in which recirculation zones of hot products generated by the direct injection of fuel and air are created and acting as a continuous source of ignition for the incom- ing main fuel–air stream. Computational Fluid Dynamics analysis was performed in this study to test the combustion performance and emissions from the vortex trapped combustor when natural gas fuel (meth- ane) is replaced with renewable and alternative fuels such as hydrogen and synthetic gas (syngas). The flame temperature, the flow field, and species concentrations inside the Vortex Trapped Combustor were obtained. The results show that hydrogen enriched hydrocarbon fuels combustion will result in more energy, higher temperature (14% increase when methane is replaced with hydrogen fuels) and NO x emis- sions, and lower CO 2 emissions (50% decrease when methane is replaced with methane/hydrogen mix- ture with 75% hydrogen fraction). The NO x emission increases when the fraction of hydrogen increases for methane/hydrogen fuel mixture. The results also show that the flame for methane combustion fuel is located in the primary vortex region but it is shifted to the secondary vortex region for hydrogen combustion. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Next generation turbine power plants will require high effi- ciency gas turbines with higher operating conditions (higher com- bustor pressures and firing temperatures). This increase in gas turbine operating conditions and firing temperature will tend to increase NO x emissions. As the desire for higher efficiency drives combustor pressures and turbine inlet temperatures ever higher, gas turbines equipped with lean premixed and non-premixed com- bustors and catalytic reduction eventually will be unable to meet the new NO x emission requirements. The development of new gas turbine combustors with lower emissions than the current state-of-the-art lean premixed and non-premixed combustors is needed. The Trapped Vortex Combustor (TVC) is a novel combustor geometry which offers stable performance over a wider range of fuel flow rates than current technology. The trapped vortex com- bustor maintains a vortex of burning fuel and air in a chamber adjacent to the main burner ports. The hot vortex acts as a pilot to the main flame burner. This enables the combustor to operate at leaner premixed fuel with improved stability and lower NO x . Fig. 1 shows a two dimensional TVC combustor with air and fuel flows, the primary and secondary vortex and the wake region [1]. The cavity is obtained by mounting two disks, or bluff bodies, with different size, in tandem. The bigger disk is located upstream of the smaller one and the flow coming from around the first creates a vortex in the cavity between the two. Fuel and primary air are introduced into the cavity generating the pilot flame (Fig. 1). In fact the aim of the system is to supply a stable and continuous source of ignition for the main stream. If the disks and hence the cavity have proper dimensions, a stable vortex establishes inside. The hot products are transported and mixed with the main air flow. The pi- lot flame is able to resist to very high main flow velocity and pos- sess extended lean and rich blowout limits relative to its simple bluff body counterpart. The idea of trapping a vortex for flame stabilization purposes is relatively new, but vortex motion for aerodynamic advantage has interested aerodynamicists for many years [2–4]. By mounting a disk behind the base of a blunt body, Mair [5] has shown that the after a body drag of the blunt object will be reduced. Roshko and Koenig [6] have reported a reduction in drag of blunt fore bodies when disks are placed on spindles ahead of the body. Computational Fluid Dynamics analysis is performed in this study to test the combustion performance and emissions from the vortex trapped combustor when natural gas fuel (methane) is replaced with renewable and alternative fuels such as hydrogen and synthesis gas. The geometry of trapped vortex combustor that was analyzed by Di Nardo et al. [1] is used in this study to compare the experimental results with our CFD analysis. This will enable us 0196-8904/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.enconman.2012.03.012 ⇑ Corresponding author. Tel.: +1 561 297 3943; fax: +1 561 297 2825. E-mail addresses: cghenai@fau.edu (C. Ghenai), ijanajreh@masder.ae (I. Janajreh). Energy Conversion and Management xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Please cite this article in press as: Ghenai C et al. Combustion of alternative fuels in vortex trapped combustor. Energy Convers Manage (2012), http:// dx.doi.org/10.1016/j.enconman.2012.03.012