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

CFD Letters ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 21-34
Author(s):  
Mohammad Nurizat Rahman ◽  
Mohd Fairus Mohd Yasin ◽  
Mohd Shiraz Aris
Keyword(s):  
Numerical Analysis ◽  
Similarity Index ◽  
Flow Characteristics ◽  
Peninsular Malaysia ◽  
Combustion Characteristics ◽  
Numerical Results ◽  
Firing Process ◽  
Reacting Flow ◽  
Outlet Temperature ◽  
The Impact

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.

Flow Characteristics of Contra- and Co-Rotating Swirler Arrangements of an Industrial Combustor

2014 ◽  
Author(s):  
X. Wu ◽  
E. R. Norster ◽  
Gang Xie
Keyword(s):  
Temperature Distribution ◽  
Numerical Model ◽  
Vortex Flow ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Outlet Temperature ◽  
Gas Turbine Combustor ◽  
Mean Velocity ◽  
Split Ratio ◽  
The Impact

This paper describes the investigation of the flow characteristics of two double radial inflow swirlers configured for use in a gas turbine combustor. The only difference between the two swirlers is in the contra- and co-rotating flow of air in the inner nozzle arrangement. The isothermal vortex flow field created by the double swirlers has been examined using numerical Model 1. The model also includes a cylinder reaction zone downstream of the swirler. The comparison of flow characteristics is carried out by examination of the spatial resolution of three mean velocity components. The contra- and co-rotating configurations show some discrepancy in terms of total loss factor and mass split ratio between the two swirlers. The comparison of flow fields also indicate that there is almost no remaining swirl further downstream in the contra-rotating configuration, while a significant amount of remaining swirl exists for the co-rotating option. The development of Model 1 to include a typical dilution zone and transition duct leads to numerical Model 2, which was used to investigate the impact on downstream mixing with the dilution air and the emerging temperature distribution at the transition duct exit. Comparing the temperature field for both configurations, the dilution effectiveness increases significantly with dilution jet penetration depth and reduces with spread along the circumferential direction. These effects lead to the central hot core persisting along the transition duct to the combustor outlet for the co-rotating option due to the combination of initial cross flow and a strong swirl, resulting in a considerable difference in the predicted outlet temperature distribution factors (OTDF) of 10.8% and 17.7% for the contra- and co-rotating arrangements, respectively.

Flow and Combustion Characteristics of Annular Advanced Vortex Combustor

2016 ◽  
Author(s):  
Yangbo Deng ◽  
Luohan Zheng ◽  
Fengmin Su ◽  
Chenshuo Ma
Keyword(s):  
Shear Layer ◽  
Computational Study ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Combustion Characteristics ◽  
Reacting Flow ◽  
Drag Effect ◽  
Injection Angle ◽  
Blunt Bodies

To provide an optimized configuration of an annular advanced vortex combustor (AVC), a combined experimental and computational study was carried out about the flow characteristics of an AVC in a rectangular channel under the non-reacting flow condition. A detailed analysis was carried out about the flow through the AVC in a rectangular channel. On this basis, annular AVC model burning hydrogen was designed and consisted of an annular channel which was circumferentially arranged 18 pairs of blunt bodies between two cylinders. A numerical simulation study was conducted to provide understanding of the combustion characteristics of the annular AVC model. The results show: (1) By placing after-bodies, the wake shedding vortex of the flow behind fore-bodies can be effectively controlled and the resistance of the flow can be reduced in a rectangular channel; (2) The injection in the cavities reduces the drag effect depth of the shear layer on the flow in the cavities so that the vortex cores of the main vortexes shift outward the cavity in the AVC in a rectangular channel; (3) With the spacing between fore-body and after body increasing, the state of the main flow is basically kept unchanged and the drag effect of the shear layer on the flow in the cavities is enhanced in the AVC in a rectangular channel; (5) A reasonable configuration of an annular AVC can sustain steady combustion, and keep a low emission level, as the equivalence ratio of the premixed hydrogen and air is between 0.5 and 0.65. (6) Comparing the annular AVC with injection to that without injection, the vortex structures with injection are more symmetrical, the combustions are more stable, and the temperature distributions are more homogeneous. (7) The vortex structure in the annular AVC is almost not changed and the temperature distribution at the outlet alters into less uniformity with injection angle increasing.

An improved de Laval nozzle experiment

2021 ◽  
pp. 030641902110341
Author(s):  
Nicholas Goodman ◽  
Brian J Leege ◽  
Peter E Johnson
Keyword(s):  
Data Acquisition ◽  
Laval Nozzle ◽  
Flow Characteristics ◽  
Data Acquisition System ◽  
Isentropic Flow ◽  
Hands On ◽  
De Laval Nozzle ◽  
Physical Phenomena ◽  
The Impact ◽  
The Relationship

Exposing students to hands-on experiments has been a common approach to illustrating complex physical phenomena that have been otherwise modelled solely mathematically. Compressible, isentropic flow in a duct is an example of such a phenomenon, and it is often demonstrated via a de Laval nozzle experiment. We have improved an existing converging/diverging nozzle experiment so that students can modify the location of the normal shock that develops in the diverging portion to better understand the relationship between the shock and the pressure. We have also improved the data acquisition system for this experiment and explained how visualisation of the standing shock is now possible. The results of the updated system demonstrate that the accuracy of the isentropic flow characteristics has not been lost. Through pre- and post-laboratory quizzes, we show the impact on student learning as well.

The flow characteristics around bridge piers under the impact of a ship

2020 ◽  
Vol 32 (6) ◽  
pp. 1165-1177
Author(s):  
Yan-fen Geng ◽  
Hua-qiang Guo ◽  
Xing Ke
Keyword(s):  
Flow Characteristics ◽  
Bridge Piers ◽  
The Impact

scholarly journals Quality assurance of radiotherapy in the ongoing EORTC 1420 “Best of” trial for early stage oropharyngeal, supraglottic and hypopharyngeal carcinoma: results of the benchmark case procedure

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
J-J Stelmes ◽  
E. Vu ◽  
V. Grégoire ◽  
C. Simon ◽  
E. Clementel ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Early Stage ◽  
Prospective Trial ◽  
Similarity Index ◽  
Phase Iii ◽  
Current Phase ◽  
Hypopharyngeal Carcinoma ◽  
Transoral Surgery ◽  
Swallowing Function ◽  
The Impact

Abstract Introduction The current phase III EORTC 1420 Best-of trial (NCT02984410) compares the swallowing function after transoral surgery versus intensity modulated radiotherapy (RT) in patients with early-stage carcinoma of the oropharynx, supraglottis and hypopharynx. We report the analysis of the Benchmark Case (BC) procedures before patient recruitment with special attention to dysphagia/aspiration related structures (DARS). Materials and methods Submitted RT volumes and plans from participating centers were analyzed and compared against the gold-standard expert delineations and dose distributions. Descriptive analysis of protocol deviations was conducted. Mean Sorensen-Dice similarity index (mDSI) and Hausdorff distance (mHD) were applied to evaluate the inter-observer variability (IOV). Results 65% (23/35) of the institutions needed more than one submission to achieve Quality assurance (RTQA) clearance. OAR volume delineations were the cause for rejection in 53% (40/76) of cases. IOV could be improved in 5 out of 12 OARs by more than 10 mm after resubmission (mHD). Despite this, final IOV for critical OARs in delineation remained significant among DARS by choosing an aleatory threshold of 0.7 (mDSI) and 15 mm (mHD). Conclusions This is to our knowledge the largest BC analysis among Head and neck RTQA programs performed in the framework of a prospective trial. Benchmarking identified non-common OARs and target delineations errors as the main source of deviations and IOV could be reduced in a significant number of cases after this process. Due to the substantial resources involved with benchmarking, future benchmark analyses should assess fully the impact on patients’ clinical outcome.

scholarly journals Virus Transmission Risk in Urban Rail Systems: Microscopic Simulation-Based Analysis of Spatio-Temporal Characteristics

2021 ◽  
pp. 036119812110101
Author(s):  
Jiali Zhou ◽  
Haris N. Koutsopoulos
Keyword(s):  
Public Transportation ◽  
Virus Transmission ◽  
Flow Characteristics ◽  
Transportation Systems ◽  
Transmission Risk ◽  
Microscopic Simulation ◽  
Spatial And Temporal Patterns ◽  
Subway System ◽  
Public Transportation Systems ◽  
The Impact

The transmission risk of airborne diseases in public transportation systems is a concern. This paper proposes a modified Wells-Riley model for risk analysis in public transportation systems to capture the passenger flow characteristics, including spatial and temporal patterns, in the number of boarding and alighting passengers, and in number of infectors. The model is used to assess overall risk as a function of origin–destination flows, actual operations, and factors such as mask-wearing and ventilation. The model is integrated with a microscopic simulation model of subway operations (SimMETRO). Using actual data from a subway system, a case study explores the impact of different factors on transmission risk, including mask-wearing, ventilation rates, infectiousness levels of disease, and carrier rates. In general, mask-wearing and ventilation are effective under various demand levels, infectiousness levels, and carrier rates. Mask-wearing is more effective in mitigating risks. Impacts from operations and service frequency are also evaluated, emphasizing the importance of maintaining reliable, frequent operations in lowering transmission risks. Risk spatial patterns are also explored, highlighting locations of higher risk.

scholarly journals Remote Sensing to Study Mangrove Fragmentation and Its Impacts on Leaf Area Index and Gross Primary Productivity in the South of Peninsular Malaysia

2021 ◽  
Vol 13 (8) ◽  
pp. 1427
Author(s):  
Kasturi Devi Kanniah ◽  
Chuen Siang Kang ◽  
Sahadev Sharma ◽  
A. Aldrie Amir
Keyword(s):  
Remote Sensing ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Primary Productivity ◽  
Peninsular Malaysia ◽  
Area Index ◽  
Mangrove Area ◽  
The Mean ◽  
Shape Complexity ◽  
The Impact

Mangrove is classified as an important ecosystem along the shorelines of tropical and subtropical landmasses, which are being degraded at an alarming rate despite numerous international treaties having been agreed. Iskandar Malaysia (IM) is a fast-growing economic region in southern Peninsular Malaysia, where three Ramsar Sites are located. Since the beginning of the 21st century (2000–2019), a total loss of 2907.29 ha of mangrove area has been estimated based on medium-high resolution remote sensing data. This corresponds to an annual loss rate of 1.12%, which is higher than the world mangrove depletion rate. The causes of mangrove loss were identified as land conversion to urban, plantations, and aquaculture activities, where large mangrove areas were shattered into many smaller patches. Fragmentation analysis over the mangrove area shows a reduction in the mean patch size (from 105 ha to 27 ha) and an increase in the number of mangrove patches (130 to 402), edge, and shape complexity, where smaller and isolated mangrove patches were found to be related to the rapid development of IM region. The Moderate Resolution Imaging Spectro-radiometer (MODIS) Leaf Area Index (LAI) and Gross Primary Productivity (GPP) products were used to inspect the impact of fragmentation on the mangrove ecosystem process. The mean LAI and GPP of mangrove areas that had not undergone any land cover changes over the years showed an increase from 3.03 to 3.55 (LAI) and 5.81 g C m−2 to 6.73 g C m−2 (GPP), highlighting the ability of the mangrove forest to assimilate CO2 when it is not disturbed. Similarly, GPP also increased over the gained areas (from 1.88 g C m−2 to 2.78 g C m−2). Meanwhile, areas that lost mangroves, but replaced them with oil palm, had decreased mean LAI from 2.99 to 2.62. In fragmented mangrove patches an increase in GPP was recorded, and this could be due to the smaller patches (<9 ha) and their edge effects where abundance of solar radiation along the edges of the patches may increase productivity. The impact on GPP due to fragmentation is found to rely on the type of land transformation and patch characteristics (size, edge, and shape complexity). The preservation of mangrove forests in a rapidly developing region such as IM is vital to ensure ecosystem, ecology, environment, and biodiversity conservation, in addition to providing economical revenue and supporting human activities.

scholarly journals Airflow Characteristics According to the Change in the Height and Porous Rate of Building Roofs for Efficient Installation of Small Wind Power Generators

2021 ◽  
Vol 13 (10) ◽  
pp. 5688
Author(s):  
Jangyoul You ◽  
Kipyo You ◽  
Minwoo Park ◽  
Changhee Lee
Keyword(s):  
Wind Speed ◽  
Wind Power ◽  
Turbulence Intensity ◽  
Flow Characteristics ◽  
High Porosity ◽  
Power Generators ◽  
Speed Reduction ◽  
Reduction Effect ◽  
Wind Power Generators ◽  
The Impact

In this paper, the air flow characteristics and the impact of wind power generators were analyzed according to the porosity and height of the parapet installed in the rooftop layer. The wind speed at the top was decreasing as the parapet was installed. However, the wind speed reduction effect was decreasing as the porosity rate increased. In addition, the increase in porosity significantly reduced turbulence intensity and reduced it by up to 40% compared to no railing. In the case of parapets with sufficient porosity, the effect of reducing turbulence intensity was also increased as the height increased. Therefore, it was confirmed that sufficient parapet height and high porosity reduce the effect of reducing wind speed by parapets and significantly reducing the turbulence intensity, which can provide homogeneous wind speed during installation of wind power generators.

Simulation of a Free Standing Riser Model and Validation With Experimental Results

2014 ◽  
Author(s):  
Marcio Yamamoto ◽  
Sotaro Masanobu ◽  
Satoru Takano ◽  
Shigeo Kanada ◽  
Tomo Fujiwara ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Previous Experiment ◽  
Numerical Results ◽  
Experimental Results ◽  
Previous Article ◽  
Scale Model ◽  
Analysis Software ◽  
Free Standing ◽  
Reduced Scale

In this article, we present the numerical analysis of a Free Standing Riser. The numerical simulation was carried out using a commercial riser analysis software suit. The numerical model’s dimensions were the same of a 1/70 reduced scale model deployed in a previous experiment. The numerical results were compared with experimental results presented in a previous article [1]. Discussion about the model and limitations of the numerical analysis is included.

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