Ziaul Huque

Optimization of Wind Turbine Airfoil Using Nondominated Sorting Genetic Algorithm and Pareto Optimal Front

A Computational Fluid Dynamics (CFD) and response surface-based multiobjective design optimization were performed for six different 2D airfoil profiles, and the Pareto optimal front of each airfoil is presented. FLUENT, which is a commercial CFD simulation code, was used to determine the relevant aerodynamic loads. The Lift Coefficient () and Drag Coefficient () data at a range of 0° to 12° angles of attack () and at three different Reynolds numbers (, 479, 210, and 958, 422) for all the six airfoils were obtained. Realizable turbulence model with a second-order upwind solution method was used in the simulations. The standard least square method was used to generate response surface by the statistical code JMP. Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) was used to determine the Pareto optimal set based on the response surfaces. Each Pareto optimal solution represents a different compromise between design objectives. This gives the designer a choice to select a design compromise that best suits the requirements from a set of optimal solutions. The Pareto solution set is presented in the form of a Pareto optimal front.

Assessment of Bioethanol Applications on Transportation Vehicles in Houston

A large amount of emissions from area industry and transportation causes severe air pollution problems in the Houston metro area in Texas. Bioethanol has been added in gasoline for many years in the US and the aim is to not only reduce the consumption of the fossil fuels, but also to improve air quality. Life cycle assessment is carried out to evaluate energy and water use, and emissions from transportation vehicles fueled with gasoline and blended fractions of bioethanol in Houston metro area. The emissions examined include greenhouse gases (GHG), VOC, SOx, CO, NOx and PM2.5 and PM10. Some blends of gasoline and bioethanol derived from corn, such as E0, E10, E20, high octane fuel (HOF) E25, HOF E40, E50, E85 and E100 were investigated to study the effects of the blends on the criteria emissions. The emissions were analyzed for three pathways, well-to-pump, pump-to-vehicle and wellto- wheel using the GREET 1 2015 model. The well-to-pump analysis generally showed that only GHGs emissions reduce with the increase of bioethanol blend rates, not other pollutants. The pump-to-vehicle study verified that HOF E25 and HOF E40 are excellent for the vehicles equipped with traditional SI engines and E85 is better for Fuel flexible vehicles (FFV). The well-to-wheel study showed that GHG and CO emissions are reduced with the increase of the bioethanol in the fuel blends; the use of energy and water increases at higher bioethanol ratios; and HOF E25 and HOF E40 are competing fuels to E10 with excellent performance, lower CO2 emissions and slightly increase of other emissions.

A Study of Aerodynamics Force Evaluation of Horizontal Axis Wind Turbine (HAWT) Blade Using 2D and 3D Comparison

The main purpose of the paper is to use Computational Fluid Dynamics (CFD) in 3-D analysis of aerodynamic forces of a Horizontal Axis Wind Turbine (HAWT) blade and compare the 3-D results with the 2-D experimental results. The National Renewable Energy Laboratory (NREL) Phase VI wind blade profile is used as a model for the analysis. The results are compared with the experimental data obtained by NREL at NASA Ames Research Center for the NREL Phase VI wind turbine blade. The aerodynamic forces are evaluated using 3-D Computational Fluid Dynamics (CFD) simulation. The commercial ANSYS CFX and parameterized 3-D CAD model of NREL Phase VI are used for the analysis. The Shear Stress Transport (SST) Gamma-Theta turbulence model and 0-degree yaw angle condition are adopted for CFD analysis. For the case study seven varying wind speeds (5 m/s, 7 m/s, 10 m/s, 13 m/s, 15 m/s, 20 m/s, 25 m/s) with constant blade rotational speed (72 rpm) are considered. To evaluate the 3-D aerodynamic effect sectional pressure coefficient (Cp) and integrated forces about primary axis such as normal, tangential, thrust and torque are evaluated for each of the seven wind speed cases and compared with the NREL experimental values. The numerical difference of values on wind blade surface between this study and 3-D results of NREL wind tunnel test are found negligible. The paper represents an important comparison between the 3-D lift & drag coefficient with the NREL 2-D experimental data. The results shows that though the current study is in good agreement with NREL 3-D experimental values there is large deviation between the NREL 2-D experimental data and current 3-D study which suggests that in case of 3-D analysis of aerodynamic force of blade surface it is better to use NREL 3-D values instead of 2-D experimental values.Copyright

Propagation of Shock on NREL Phase VI Wind Turbine Airfoil under Compressible Flow

The work is focused on numeric analysis of compressible flow around National Renewable Energy Laboratory (NREL) phase VI wind turbine blade airfoil S809. Although wind turbine airfoils are low Reynolds number airfoils, a reasonable investigation of compressible flow under extreme condition might be helpful. A subsonic flow (mach no. ) has been considered for this analysis and the impacts of this flow under seven different angles of attack have been determined. The results show that shock takes place just after the mid span at the top surface and just before the mid span at the bottom surface at zero angle of attack. Slowly the shock waves translate their positions as angle of attack increases. A relative translation of the shock waves in upper and lower face of the airfoil are presented. Variation of Turbulent viscosity ratio and surface Y

Air Quality Impact of Biomass Co-Firing with Coal at a Power Plant in the Greater Houston Area

The Houston-Galveston-Brazoria (HGB) area of Texas is a moderate nonattainment region for ozone, and has a history of severe summer ozone episodes. W. A. Parish power plant (WAP) located in the greater Houston area is the largest coal and natural gas based electricity generating unit (EGU) in Texas. Forest residue is an abundant renewable resource, and can be used to offset coal usage at EGUs. This study evaluates the impact of co-firing 5%, 10%, and 15% (energy-basis) of forest residue at WAP on the air quality of the HGB area. Photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx) was conducted to investigate the air quality at three air quality monitoring sites (C696, C53, C556) in the HGB area, under two source scenarios (all-sources, point + biogenic sources). Significant reduction of SO2 and O3 was observed for 10% and 15% co-firing ratios at monitoring station (C696) close to WAP. The maximum reduction of ozone observed for 15% co-firing is 4.7% and 6.3% for all-sources and point + biogenic sources scenarios respectively. The reduction in other criteria air pollutants is not significant at all locations. The overall results from this study indicate that biomass co-firing at WAP would not lead to a significant reduction in ozone concentrations in the region during periods of peak ozone.

Long-term meteorologically independent trend analysis of ozone air quality at an urban site in the greater Houston area

ABSTRACT The Houston-Galveston-Brazoria (HGB) area of Texas has a history of ozone exceedances and is currently classified under moderate nonattainment status for the 2008 8-hr ozone standard of 75 ppb. The HGB area is characterized by intense solar radiation, high temperature, and high humidity, which influence day-to-day variations in ozone concentrations. Long-term air quality trends independent of meteorological influence need to be constructed for ascertaining the effectiveness of air quality management in this area. The Kolmogorov-Zurbenko (KZ) filter technique, used to separate different scales of motion in a time series, is applied in the current study for maximum daily 8-hr (MDA8) ozone concentrations at an urban site (U.S. Environmental Protection Agency [EPA] Air Quality System [AQS] Site ID: 48-201-0024, Aldine) in the HGB area. This site, located within 10 miles of downtown Houston and the George Bush Intercontinental Airport, was selected for developing long-term meteorologically independent MDA8 ozone trends for the years 1990–2016. Results from this study indicate a consistent decrease in meteorologically independent MDA8 ozone between 2000 and 2016. This pattern could be partially attributed to a reduction in underlying nitrogen oxide (NOx) emissions, particularly lowering nitrogen dioxide (NO2) levels, and a decrease in the release of highly reactive volatile organic compounds (HRVOCs). Results also suggest solar radiation to be most strongly correlated to ozone, with temperature being the secondary meteorological control variable. Relative humidity and wind speed have tertiary influence at this site. This study observed that meteorological variability accounts for a high of 61% variability in baseline ozone (low-frequency component, sum of long-term and seasonal components), whereas 64% of the change in long-term MDA8 ozone post 2000 could be attributed to NOx emission reduction. Long-term MDA8 ozone trend component was estimated to be decreasing at a linear rate of 0.412 ± 0.007 ppb/yr for the years 2000–2016 and 0.155 ± 0.005 ppb/yr for the overall period of 1990–2016. Implications: The effectiveness of air emission controls can be evaluated by developing long-term air quality trends independent of meteorological influences. The KZ filter technique is a well-established method to separate an air quality time series into short-term, seasonal, and long-term components. This paper applies the KZ filter technique to MDA8 ozone data between 1990 and 2016 at an urban site in the greater Houston area and estimates the variance accounted for by the primary meteorological control variables. Estimates for linear trends of MDA8 ozone are calculated and underlying causes are investigated to provide a guidance for further investigation into air quality management of the greater Houston area.

Impacts of Biodiesel Applied to the Transportation Fleets in the Greater Houston Area

Houston, the fourth largest metropolis in the US, currently experiences severe air pollution. Major pollutants, such as VOCs, CO, , PM, , CH4, and CO2, are released from the transportation fleets. To decrease fossil fuel use and greenhouse gas emissions from fleet vehicles, more and more biodiesel is used in vehicles in the Houston metropolis. The GREET model was used for simulating the fuel cycle emissions of diesel vehicles using different biodiesel blends in Houston. The fuels examined were diesel-biodiesel blends of B0, B5, B20, B50, B80, and B100. The energy and water use and emissions from vehicles fueled with the blends were investigated. The study shows that the reductions in GHG emissions are significant at the Well-to-Pump stage, and all the emissions, except GHGs and , reduce at the Pump-to-Wheel stage. The overall Well-to-Wheel analysis shows that biodiesel is beneficial for both passenger cars and heavy duty trucks. However, the benefits are more pronounced for passenger cars compared to heavy duty vehicles. When 50% of diesel passenger cars and HDDTs are switched to B20 in the Greater Houston area in 2025, the daily GHG emissions will be reduced by 2.0 and 712.1 CO2-equivalent tonnes, respectively.

Relative Contribution of Different Source Categories to Ozone Exceedances in the Houston-Galveston-Brazoria Area

The goal of this study is to analyze the relative contribution of different emission source categories to ozone in the Houston-Galveston-Brazoria (HGB) area of Texas. Emission Processing System (EPS3) is used to prepare the emission files for five different source combination cases (Base case, Biogenic, Area + Biogenic, Mobile + Biogenic, Low-level Point + Biogenic). These emission files are used to perform photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx), and the results are analyzed with Visual Environment for Rich Data Interpretation (VERDI) tool. The daily maximum ozone concentrations and individual contributions of the source categories were analyzed over a 15-day study period between June 1-15, 2012, at three locations (University of Houston-Sugarland, Bayland Park and Conroe). Biogenic sources contributed an average of 49.7% ± 12.8%, 43.1% ± 12.0%, and 39.9% ± 9.28% at Sugarland, Bayland Park and Conroe sites respectively, indicating the significance of isoprene emissions from the vegetation in northeast Houston. On peak ozone days, contribution of Mobile + Biogenic source category averages about 80.1% ± 12.6%, 79.9% ± 6.50%, and 75.9% ± 10.9% at Sugarland, Bayland Park and Conroe sites respectively, indicating the dominance of mobile source NOX emissions and the necessity for regulatory focus on mobile source emissions control.

Transitional Effect on Turbulence Model for Wind Turbine Blade

This paper presents the computational predictions of NREL Phase VI rotor using SST Gamma Theta turbulence model. All models were performed using the commercial CFD software, ANSYS Workbench CFX. Exactly the same geometry as NREL blades was built. Around 14 million unstructured mesh elements and 3.7 million nodes have been applied during the simulation. To deal with the boundary effect, 18 inflation layers were constructed around the boundary wall. The comparison of torque and thrust between several turbulent models and the experimental data were performed. For the overall performance, a better agreement with the NREL Experimental data was obtained with SST Gamma Theta model. After these verifications, the first, second SST blending function and transition blending function for seven distinct wind speeds were performed. It has been observed that SST Gamma Theta method can simulate the transition effect appropriately.Copyright

A Study on Various Aerodynamic Effects of Pointed Tip Blade

A wind turbine blade performance depends on various parameters of which the shape of the blade is one of the most important one. In this work the shape of the tip of original NREL Phase-VI blade (S809 airfoil) has been modified to determine the changes in the blade aerodynamic performance. The chord length of new blade is kept similar to the original NREL blade up to 90% of the span. Last 10% was modified to a pointed tip at the pitch axis. This paper presents a comparative study of the effect of pointed tip on aerodynamic loads. CFD simulations were performed on both original NREL shape and pointed tip shape blades. The simulation results of pointed tip blade were compared with both experimental and simulation results of original blade. Ansys geometry modeler was used to draw the geometry and to generate the grids. Ansys CFX solver and post processor were used for simulation and calculation of the results. To predict the near wall transitional effect SST Gamma Theta turbulence model was used. Results of pressure coefficient along the chord at various blade sections of the pointed tip blade were found to be almost similar to the original NREL blade CFD results. Tangential and normal force along the span of pointed tip blade at different wind speeds showed some similarity in results compared with CFD results of original NREL blade. From the velocity contour the separation of flow with the increase of wind speed can clearly be observed. Thrust and torque effects are also observed at various wind speeds. The torque values for the pointed tip blade were found to be higher in the pre-stall and stall region but slightly lower in post-stall region. But compared to the torque values the difference in thrust at the same region is found to be negligible. Pointed tip thrust values are in better agreement at high wind speeds with respect to the experimental data. The flow separation at high wind speed is also found to be less with pointed tip blade compared to the original blade.Copyright