Browsing by Author "Wiranegara, Raditya Yudha"

Now showing 1 - 4 of 4
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    Co-firing of hydrogen and natural gas in a practical DLN combustor model
    (American Society of Mechanical Engineers, 2023-09-28) Zhao, Rang; Igie, Uyioghosa; Abbott, David; Wiranegara, Raditya Yudha
    To reduce carbon dioxide emissions, the combustion of natural gas-hydrogen blends in a lean premix gas turbine combustor has been investigated. Previous studies have mostly investigated the fuel blends at relatively low pressure (up to 5 bar) with relatively low hydrogen concentrations (up to 50vol%) on lab-scale or generic burner configurations. However, the influence of higher pressure and higher hydrogen content (over 50vol%) has not been widely studied, particularly on a practical industry-scale lean premixed burner as presented in this study. Such an operation is more challenging as it increases the turbulent flame speed gradient, which is an important factor in determining the likelihood of boundary layer flashback. A preliminary RANS-based Computational Fluid Dynamics (CFD) study has been conducted using ANSYS Fluent 2021R1, employing the Realizable K-Epsilon turbulence model and the Flamelet-Generated Manifold (FGM) combustion model. The combustor consists of a diffusion pilot and premixed main fuel nozzles. Methane-hydrogen blends of up to 90vol% hydrogen were investigated at a fixed fuel energy input. 100vol% methane at 15 bar pressure was taken as the baseline reference case. To investigate the flame characteristics, contour plots of OH mass fraction, equivalence ratios and temperatures (at different planes) are presented. This study shows that the expected reduction in the flame length with increasing hydrogen concentration occurs up to 40vol%. Significantly different flame shapes (as indicated by OH contours) were seen at higher hydrogen content. For this model, the flashback occurred at 90vol% H2 as indicated by a premature development of the flame within the nozzle of the main fuel burner. NOx emissions are shown to progressively rise with increasing hydrogen content up to 60vol% but reduce as the hydrogen content increases to 70vol%. The decrease appears to be related to an improvement in the quality of fuel-air mixing. It is important to note that the apparent rate of increase in NOx with increasing hydrogen is dependent on the reporting approach used. When reporting conventionally (parts per million by volume corrected to 15% O2 on a dry basis) the increase is significantly greater than when reporting on a mass per fuel energy input basis (gram per Joule). Reporting in the conventional manner disadvantages hydrogen because of the impact of oxygen consumption and water production on the corrections.
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    Minimum environmental load extension through compressed air extraction: numerical analysis of a dry low NOx combustor
    (Elsevier, 2023-02-17) Wiranegara, Raditya Yudha; Igie, Uyioghosa; Ghali, Pierre; Abudu, Kamal; Abbott, David; Hamilton, Richard
    The operational flexibility of gas turbine (GT) engines is a key requirement to coexist alongside increasing renewable energy that is often intermittent. One of the GT flexibility criteria is the Minimum Environmental Load (MEL). This is the lowest load the engine can be operated, without infringing on emissions limits (particularly CO) and is relevant to periods when there is a priority to renewable generation or low power demand. This study along with a series of related works of the authors proposes compressor air extraction for MEL extension. Here, a stand-alone three-dimensional numerical dry low NOx combustor demonstrates the technical viability concerning combustor performance and emissions. In addition, supplemented with low-order models for durability and stability evaluations. For the first time, there is evidence to show that the combustor can handle the 18% compressed air extraction to sustain a new MEL. This operation is characterised by a 12.3% reduction in CO through an increase of the fuel split ratio by 2% after design exploration cases. However, at the expense of a smaller overall rise in NO emissions by 5%. The durability analysis focused on the wall liner temperature assessments, which show no unusually high temperature rise for the new MEL. Similarly, the thermoacoustic instability frequencies and gains are around the normal operation mode. When benchmarked against previous related engine-level analysis, the evidence shows that the new MEL is a 7% points reduction of load.
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    Numerical study of radiation and fuel-air unmixedness on the performance of a dry low NOx combustor
    (American Society of Mechanical Engineers (ASME), 2022-11-11) Wiranegara, Raditya Yudha; Igie, Uyioghosa; Ghali, Pierre; Zhao, Rang; Abbott, David; Hamilton, Richard
    The development of gas turbine combustors is expected to consider the effects of radiation heat transfer in modelling. However, this is not always the case in many studies that neglect this for adiabatic conditions. The effect of radiation is substantiated here, concerning the impact on the performance, mainly the emissions. Also, the fuel-air unmixedness (mixing quality) influenced by the combustor design and operational settings has been investigated with regards to the emissions. The work was conducted with a Mitsubishi-type Dry Low NOx combustor developed and validated against experimental data. This 3D computational fluid dynamics study was implemented using Reynolds-Averaged Navier Stokes simulation and the Radiative Transfer Equation model. It shows that NO, CO and combustor outlet temperature reduces when the radiative effect is considered. The reductions are 17.6% and below 1% for the others respectively. Thus, indicating a significant effect on NO. For unmixedness across the combustor in a non-reacting simulation, the mixing quality shows a direct relationship with the Turbulence Kinetic Energy (TKE) in the reacting case. The most significant improvements in unmixedness are shown around the main burner. Also, the baseload shows better mixing, higher TKE and lower emissions (particularly NO) at the combustor outlet, compared to part-load.
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    Power augmentation and Ramp-Up rate improvement through compressed air Injection: a dry low NOx combustor CFD analysis
    (Elsevier, 2024-02-09) Wiranegara, Raditya Yudha; Igie, Uyioghosa; Szymanski, Artur; Abudu, Kamal; Abbott, David; Sethi, Bobby
    Gas turbines play a key role in accelerating the transition towards more environmentally friendly power generation. This role includes backup of renewable generation that is intermittent, providing grid inertia as well as other ancillary services for grid stability. For quick backup power, the ramp-up rate of gas turbines can be improved through air injection at the back of the compressor, facilitated by integrating compressed air energy storage. Published works have mostly focused on low-fidelity engine system analysis of air injection overall effects. No study has focused on the detailed combustor performance presented in this study. The work shows the impact of air injection on the emissions, thermoacoustic stability and liner wall durability. These yardsticks in assessing the operability of the combustor have also been used for air power augmentation and ramp-up analysis. ANSYS software was used in the computational fluid dynamics (CFD) analysis of the three-dimensional dry low NOx combustor. Low-order models were used for the thermoacoustic stability and durability analysis. For the power augmentation study, the NO and CO emissions produced at 15 % air injection are below the maximum values of the combustor in design operations. Also, the stability and durability were within limits. The ramp-up investigation indicates up to 10 % air injection is allowed and the emissions are similarly acceptable. However, the thermoacoustic analysis shows a potential for combustion instabilities at high frequencies above 1800 Hz. Generally, there was no unusual wall liner durability in these two studies. When benchmarked against previous engine-level analysis, the ramp-up rate can be potentially improved by 54 % if the small concern on thermoacoustic instability is resolved.