Reacting Flow Characteristics and Multifuel Capabilities of a Multi-Nozzle Dry Low NOx Combustor: A Numerical Analysis

Abstract

The fluctuating quality of natural gas (NG) in Peninsular Malaysia (PM) makes it challenging for the gas turbine (GT) combustor to meet the combustion performance requirements from the Original Equipment Manufacturer (OEM). Moreover, the gas quality sensitivity is more apparent in modern dry low NOx (DLN) combustors. Many of the prior combustion investigations were conducted on a modest scale in the laboratory. In actuality, combustion characterizations in complicated DLN combustors are more valuable to the power generation sector. Hence, the current numerical analysis utilized the RANS formulation and a detailed chemistry to examine the impact of ethane (C2H6), carbon dioxide (CO2), and nitrogen (N2) proportions in NG on combustion characteristics in a multi-nozzle DLN (MN-DLN) combustor, with the support of Modified Wobbe Index (MWI) calculations. Validations were performed using the combustor outlet temperature (COT) from the power plant where the actual MN-DLN combustor is operated, which revealed less than 10 % discrepancy. Qualitative validations were carried out by comparing the burn trace from the actual combustor wall to the predicted results, revealing an adequate Structural Similarity Index (SSIM) of 0.43. From numerical results of flame fronts and COTs, the addition of 20 % diluents (CO2 and N2) to NG demonstrated the blowoff risk. When MWIs of Kerteh and the JDA (major NG resources) were used as baselines, MWI ranges of all NG compositions under study surpassed the OEM’s ± 5 % limit. The increase in CO2 proportion results in a wide MWI range, especially when Kerteh is used as the baseline. Therefore, any GTs in PM that have previously been calibrated to use Kerteh's NG are more likely to have combustion instabilities if CO2 levels in NG suddenly increase. The higher MWI range backs up the current numerical results that showed the deleterious effects of a high CO2 composition throughout the combustor firing process. However, increasing the amount of C2H6 by up to 20 % is predicted to have minor effects on combustion characteristics. Overall, the validated numerical model of the MN-DLN combustor provided critical information about combustion characteristics and multifuel capabilities in respect to the NG quality in PM.

Large Eddy Simulation of Hydrogen/Natural Gas/Air Premixed Swirling Flames and CIVB Flashback Risks

“…For convective terms estimation and other spatial derivatives, the linear-upwind interpolation scheme (the second-order upwind scheme) and linear interpolation (second-order central differences) were used, respectively. Previous studies have shown that the probability density function (PDF) and flamelet formulations are adequate for describing the complex turbulence-chemistry interaction within the combustor [13,[14][15]24]. As a result, the current study employed the non-adiabatic steady flamelet model with a detailed chemistry mechanism (GRI Mech 3.0), which computes temperature and species composition through the use of a variable known as the mixture fraction, which reflects the local fuel/oxidizer ratio [25].…”

“…A turbulent flame brush is described by the steady flamelet method as a collection of discrete, steady laminar flamelets known as diffusion flamelets. The diffusion flamelets are then implanted in a turbulent flame using statistical PDF methods, allowing realistic chemical kinetic effects to be incorporated into turbulent flames [13,24]. The pre-processed and tabulated chemistry saves a significant amount of calculation time.…”

“…Therefore, there are still a few key issues that are preventing the GT combustion systems from improving [11]. As a result, the desire to create GTs that can run on a variety of fuels, from natural gas (NG) to NG blended with H 2 , frequently runs into operability problems in the form of the aforementioned instabilities [12][13][14][15].…”

Coal Dust Severity in a Power Plant: In-Situ, Analytical, and Numerical Assessments

“…To obtain good spatial convergence accuracy, the grid independent test was used. Meshes (elements) were created with orthogonal quality and skewness in mind to represent mesh quality because mesh quality influences the level of spatial discretisation error [19]. To ensure adequate mesh qualities, the orthogonal and skewness features of all generated meshes evaluated in the grid independent test were controlled.…”

Oil Palm Wastes Co-firing in an Opposed Firing 500 MW Utility Boiler: A Numerical Analysis

“…Another approach that has the potential to be a dependable and cost-effective strategy in the investigation of OPWs co-firing is numerical modelling (computational fluid dynamics). Numerical modelling has been shown to be an effective technique for diagnosing and resolving flow and combustion issues [24,[26][27][28][29][30][31]. As it can provide insights into the combustion properties of unfamiliar solid fuel blends [6,24], such as OPWs co-firing, it has been widely used to examine the combustion performance of a single coal and multiple solid fuel blends in bench-pilots and full-scale utility furnaces.…”