Syngas production from municipal solid waste with a reduced tar yield by three-stages of air inlet to a downdraft gasifier

This paper presents a new variable pitch (VP) approach to increase the peak power coefficient of the straight-bladed vertical-axis wind turbine (VAWT), by widening the azimuthal angle band of the blade with the highest aerodynamic torque, instead of increasing the highest torque. The new VP-approach provides a curve of pitch angle designed for the blade operating at the rated tip speed ratio (TSR) corresponding to the peak power coefficient of the fixed pitch (FP)-VAWT. The effects of the new approach are exploited by using the double multiple stream tubes (DMST) model and Prandtl’s mathematics to evaluate the blade tip loss. The research describes the effects from six aspects, including the lift, drag, angle of attack (AoA), resultant velocity, torque, and power output, through a comparison between VP-VAWTs and FP-VAWTs working at four TSRs: 4, 4.5, 5, and 5.5. Compared with the FP-blade, the VP-blade has a wider azimuthal zone with the maximum AoA, lift, drag, and torque in the upwind half-cycle, and yields the two new larger maximum values in the downwind half-cycle. The power distribution in the swept area of the turbine changes from an arched shape of the FP-VAWT into the rectangular shape of the VP-VAWT. The new VP-approach markedly widens the highest-performance zone of the blade in a revolution, and ultimately achieves an 18.9% growth of the peak power coefficient of the VAWT at the optimum TSR. Besides achieving this growth, the new pitching method will enhance the performance at TSRs that are higher than current optimal values, and an increase of torque is also generated.

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Variable Pitch Approach for Performance Improving of Straight-Bladed VAWT at Rated Tip Speed Ratio

The effect of the installation of a circular cylinder upstream of the returning turbine blade on the performance of the Savonius wind turbine was studied experimentally. The experiments are carried out for Re = 99,000. The circular cylinder with a diameter relative to the blade diameter (d/D) = 0.54 was installed at a distance between the circular cylinder and the returning blade relative to the blade diameter (S/D) varied from 1.4 to 2.2. The experimental results indicate that changes in distance S/D may improve the turbine power coefficient, where the maximum power coefficient occurs at S/D = 1.4, which increases in the power coefficient around 12.2% at a tip-speed ratio of 0.65 relative to the conventional one. However, when the circular cylinder is placed away from the returning blade (S/D > 1.8), there is practically no change in the power coefficient.

Improving the performance of Savonius wind turbine by installation of a circular cylinder upstream of returning turbine blade

Gasification is a potential technology to convert municipal solid waste into energy in the form of syngas. Addition of air to the pyrolysis zone and oxidation was carried out by modifying a single-stage downdraft gasifier into a multistage air inlet. The results showed an increase in the syngas heating value and decreased tar content. To determine the performance, the effects of equivalent ratio, preheated air temperature, and air ratio were studied. When the equivalent ratio is increased, the flammable gas and LHV decrease. The optimum conditions were obtained for the equivalent ratio (ER) of 0.4, where the percentage of CO and H₂ increased at an oxidation temperature of 902 °C. The variation of the air ratio has a stronger influence than the effect of the equivalent ratio because at the same equivalent ratio an increase in pyrolysis temperature of 674 °C is favorable to reforming tar from primary tar to secondary tar. The CO percentage increased significantly from 18.17% to 22.51%. Air preheating is useful to improve gasification performance, which was characterized by an increase in LHV from 5254 to 5976 kJ/kg. The optimum equivalent ratio and air ratio were 0.4 and 40:60, respectively, and effectively reduced the tar content from 50.02 to 27.82 mg/Nm³. The results of this study can be used to optimize multistage gasifier performance using air preheating and a multistage air inlet.

Improved Municipal Solid Waste Gasification Efficiency Using a Modified Downdraft Gasifier with Variations of Air Input and Preheated Air Temperature

Increasing energy demand and environmental regulations around the world provide an adequate framework for developing methods of obtaining energy from renewable sources. Wind force is a resource with a high potential through which green energy can be obtained with no negative impact on the environment. Different turbine typologies have been developed, which can convert the wind force into mechanical and electrical energy through turbine rotational motion. Starting from the classic vertical-axis SAVONIUS rotor model, other models have been designed, which, according to the numerical studies and experimental test results, show higher performance parameters in operation. Such models present specific rotor blade geometries to achieve better operational results in terms of shaft torque and generated power. There are multiple research results from numerical analysis on virtual models or experimental tests that use rotor models in different constructive configurations aiming to improve operation performance. These research activities are related to the rotor blade number, the aspect and overlap ratio values, the blade profile geometry modification, the use of end plates connected to the rotor blades, curtain mounting solutions for directing the air flow on the active blade alone, and rotor constructive variants with deformable blades during operation. Some of the results obtained from the mentioned research activities are shown in this review for special rotor configurations whose performance results in terms of torque or power values are compared to the classical SAVONIUS model.

https://www.mdpi.com/1996-1073/14/7/1962/pdf

Review of Specific Performance Parameters of Vertical Wind Turbine Rotors Based on the SAVONIUS Type

Biomass from palm oil plant waste in the form of palm fronds that are abundant but underutilized. Considering the large and consistent supply, oil palm fronds (OPF) could be a promising source of biomass energy through gasification. This Paper presents an experimental evaluation the quality of the producer gas in a two-stage gasifier, for different operating conditions. Varying the equivalent ratio (ER) to the gasifier and the distribution of gasification air between each gasification stages (ARpir-oks). The gas composition and its lower heating value (LHV) were also determined. Experimental tests were performed varying the operating conditions of the gasifier: the air flow between 17,3 kg/h, 23,1 kg/h, and 28,9 kg/h (the proximate equivalence ratio from 0,3, 0,4 and 0.5) and the air flow ratio in the two stages (ARpir-oks) between 0%, 70%, 80%, and 90%, evaluating the effects of these parameters over the quality of the gas. The results show that a highest CO content (22.1% v) was achieved for airflow 23.1 kg / s (ER 0.4) at AR 90% along with decreasing CH4 (0.97% v) while H2 (16, 27% v) highest achieved at AR 80%. LHV gas shows maximum value at 4542.5 Kj/kg achieved at Air Ratio (AR) 90% with air flow 23.1 kg / s (ER 0.4). Gasification of two-stageair supply increase gas composition and allowed to reduce the tar content in the producer gas. This result can be explained by increasing temperature in pyrolysis and combustion zone. Good stability and performance of pyrolysis and combustion zones, H2O and CO2 formed in this zone and their interaction with charcoal is excellent in endothermicwater-gas reaction and boudouard reaction.Biomass from palm oil plant waste in the form of palm fronds that are abundant but underutilized. Considering the large and consistent supply, oil palm fronds (OPF) could be a promising source of biomass energy through gasification. This Paper presents an experimental evaluation the quality of the producer gas in a two-stage gasifier, for different operating conditions. Varying the equivalent ratio (ER) to the gasifier and the distribution of gasification air between each gasification stages (ARpir-oks). The gas composition and its lower heating value (LHV) were also determined. Experimental tests were performed varying the operating conditions of the gasifier: the air flow between 17,3 kg/h, 23,1 kg/h, and 28,9 kg/h (the proximate equivalence ratio from 0,3, 0,4 and 0.5) and the air flow ratio in the two stages (ARpir-oks) between 0%, 70%, 80%, and 90%, evaluating the effects of these parameters over the quality of the gas. The results show that a highest CO content (22.1% v) was achieved for airflow 23....

The effect of two stage gasifying agent on biomass downdraft gasification to the gasifier performance

Vertical axis wind turbine is a tool that is being developed to generate energy from wind. One cause is still little use of wind energy is the design of wind turbines that are less precise. Therefore in this study will be developed the system design of hybrid vertical axis wind turbine and tested performance with experimental methods. The design of hybrid turbine based on a straight bladed Darrieus turbine along with a double step Savonius turbine. The method used to design wind turbines is by studying literature, analyzing the critical parts of a wind turbine and the structure of the optimal design. Wind turbine prototype of the optimal design characteristic tests in the wind tunnel experimentally by varying the speed of the wind. From the experimental results show that the greater the wind speed, the greater the wind turbine rotation and torque is raised. The hybrid vertical axis wind turbine has much better self-starting and better conversion efficiency.

The system design and performance test of hybrid vertical axis wind turbine

We investigate the capillary effects during droplet formation on pillar surface via a dewetting process. The microdroplet formed from the fluid remains on the top surface of micropillar after the dewetting process. The simulation results show that the ratio of the diameter of microdroplet (Dd) and the diameter of micropillar (Dp) is correlated as 3.26Re0.25 for H/Dp<0.5, where Re is the Reynolds numbers and H is the liquid thickness between the top surface of micropillar and the upper substrate. The analytical solution for growth droplet based on the conservation of energy is provided. The numerical results show that our prediction is consistent with the analytical solution for a large range of Re number.

Capillary Effects during Droplet Formation on the Solid Surface

Renewable energy is an important thing to be concerned since the rapid decrease of natural energy. Wind power is one of renewable energy which can be used to be converted into electrical energy. Darrieus-Savonius wind turbine is a tool used to convert the wind power. The combination of Savonius rotor which has self-starting ability and Darrieus rotor which has high efficiency make this hybrid wind turbine often used in urban area. This numerical study focused on Darrieus-Savonius wind turbine with Savonius rotor placed in the middle of the Darrieus rotor (type-A) and Savonius rotor placed under Darrieus rotor (type-B) at 5 m/s, 10 m/s, and 15 m/s wind velocity. Flow interaction between Savonius rotor and Darrieus rotor occurred in the type-A configuration that caused performance reduction from each rotor. It is proved by the torque generated by type-A configuration is lower than the torque generated by type-B configuration. Generally, in the low tip speed ratio, coefficient of power of type-A wind turbine is higher than the type-B wind turbine. It is caused by the swept area of type-A wind turbine is smaller than the type-B wind turbine.Renewable energy is an important thing to be concerned since the rapid decrease of natural energy. Wind power is one of renewable energy which can be used to be converted into electrical energy. Darrieus-Savonius wind turbine is a tool used to convert the wind power. The combination of Savonius rotor which has self-starting ability and Darrieus rotor which has high efficiency make this hybrid wind turbine often used in urban area. This numerical study focused on Darrieus-Savonius wind turbine with Savonius rotor placed in the middle of the Darrieus rotor (type-A) and Savonius rotor placed under Darrieus rotor (type-B) at 5 m/s, 10 m/s, and 15 m/s wind velocity. Flow interaction between Savonius rotor and Darrieus rotor occurred in the type-A configuration that caused performance reduction from each rotor. It is proved by the torque generated by type-A configuration is lower than the torque generated by type-B configuration. Generally, in the low tip speed ratio, coefficient of power of type-A wind turbine...

Numerical study on a Darrieus-Savonius wind turbine with Darrieus rotor placement variation

Numerical analysis is performed on Savonius turbine rotor with the standard blades and Bach-profile blades. The standard configuration was taken as a half semi-circular cylinder with overlap. Savonius turbine with overlap blades is considered because it gives better performance compared to that without overlap. Meanwhile, the Bach-profile blades tested are varied with arc surface angles of 124° and 135°. The objective of the study is to compare the performance of the Savonius turbine with standard blades with overlap to that with Bach-profile blades, particularly at very low wind speed. Steady, two-dimensional numerical simulations were performed on Savonius rotor turbine. Reynolds-Averaged Navier Stokes solver was used to solve the computations, with the turbulence model of the transition k-kl-ω model. The simulations were run at constant freestream velocities of 4 m/s and 7 m/s, and at various rotor angle positions. Overall, the results show that the rotor with the Bach-profile blade with arc surface angle of 135° has the highest static torque coefficient compared to other profile blades, for both the velocities tested. The self-starting capabilities are approximately similar for all the blade type tested.

Bambang Arip Dwiyantoro

Papers

The effect of two stage gasifying agent on biomass downdraft gasification to the gasifier performance

The system design and performance test of hybrid vertical axis wind turbine

Capillary Effects during Droplet Formation on the Solid Surface

Numerical study on a Darrieus-Savonius wind turbine with Darrieus rotor placement variation

Numerical study of savonius wind turbines with standard and Bach-profile blade variations