Papers by Aji Putro Prakoso
International journal of thermofluids, Apr 1, 2024
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, Feb 4, 2024
Cross-flow turbines (CFT) have evolved since the first investigation in 1949. After some use of c... more Cross-flow turbines (CFT) have evolved since the first investigation in 1949. After some use of computational fluid dynamics (CFD) simulations in CFT development, it is known that there might be a recirculation vortex inside the CFT. At the CFT internal flow, some significant turbulent flow occurred, which is indicated by a higher value of turbulence kinetic energy (TKE). However, the effect of the turbulence inside this turbine still evokes many questions. This study ran Several CFD simulations on three CFT blade designs. One of them has already been tested experimentally, and the others are the modifications of the first design. There are two scenarios for the simulations: run in a traditionally two-phase condition or in a submerged state to maximize the usage of the potential head. This study found that the existing configuration has a contradirectional permanent recirculation, dead area, and high turbulency spot, which induce a higher loss. Meanwhile, all those phenomena could be minimized under the modified blade condition. The modification improves multiphase CFT performance by relatively 22.2% efficiency and 16.6% relative escalation for the submerged condition. However, the expected recirculation flow found in the prior study was still not found in this study. Another modification is still needed.
Deleted Journal, Jul 24, 2023
Several agricultural areas in Indonesia are classified as underdeveloped rural areas, and challen... more Several agricultural areas in Indonesia are classified as underdeveloped rural areas, and challenging to acquire electricity from the primary grid. On the other hand, some pico hydropower potentials can be found in agriculture, especially at the irrigation dam spillway flows. However, no such technology can convert the energy inside the water open-channel flow through dam spillways into electricity. Crossflow turbines (CFT) are expected to utilize dam spillways' power due to their ability to convert the kinetic energy of water. Prior studies found that airfoil profile could slightly increase CFT efficiency and affect the interaction between water and turbine. Using planar two-dimensional computational fluid dynamics (CFD) numerical simulation analysis, the current study investigated the energy conversion phenomenon inside different openchannel CFT blade profiles. This study simulates CFT working at 3 meters of total head and 0.04 m3/s of water discharge put into the dam spillway's downstream. The turbine blade profiled with the National Advisory Committee of Aeronautics (NACA) standard airfoil numbered 9405, 9503, and 9506 are being compared and investigated in the present study. CFD numerical analysis results show that the forward direction NACA airfoil profiled blades deliver better efficiency than the reversed one. These findings contradict the prior study's results which tested airfoil profiled CFT working as usual with nozzle. This phenomenon indicated differences in the energy transfer process between open channel CFT and the ordinary CFT with a nozzle. Furthermore, current work finds that forward NACA-9503 CFT has a higher efficiency than other tested airfoil profiles, with 57.05% efficiency. In addition, the present study finds that the NACA-95XX airfoil has a more suitable chamber curve with the original CFT blade's curve than the NACA-94XX airfoil by velocity triangle analysis. Then, the NACA-9503 profile is thinner than the NACA-9506 profile, which eases water flowing through the turbine blades.
CFD Letters, Sep 29, 2023
Breastshot water wheels have very good simplicity, efficiency, and low head working range which i... more Breastshot water wheels have very good simplicity, efficiency, and low head working range which is suitable for use in tropical rainforest villages in Indonesia. One of the weaknesses of the breastshot water wheel is that it has a very slow rotational speed which makes it need a high transmission ratio to be coupled with the generator. This study investigates the performance of a breastshot water wheel at smaller diameters and modifying the bucket inlet angle (36°, 49°, 71°, and 90°) by the computational fluid dynamics (CFD) method. In this case, the breastshot waterwheel's diameter ratio is equal to the head. Based on CFD results, the new configuration (this study) allowed us to increase the rotational speed to 30 to 35 rpm, higher than typical rotational speeds of breastshot water wheels of less than 10 rpm. Then, the bucket inlet angle and wheel rotation affect the performance of the breastshot waterwheel and are expressed using empirical law. Based on the empirical law approach, the 49° bucket is recommended because it has a stable efficiency above 60% and a wide operating range; the large discharge fluctuations do not change the turbine performance significantly.
Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, Feb 4, 2024
Harvesting the kinetic energy from the small dam's spillway downstream flow in agricultural areas... more Harvesting the kinetic energy from the small dam's spillway downstream flow in agricultural areas is interesting. On the other hand, a cross-flow turbine (CFT) is a unique impulse turbine because it works at a higher specific speed, which means this turbine works at a lower head and higher water flow rate. Thus, there is an opportunity to use a CFT to harvest the energy in the spillway. There are two possible scenarios: at the flat horizontal and the 30° slop flow. Several computational fluid dynamics (CFD) simulations were conducted to test the hypothesis. The simulations were performed with five variations of the ratio between the cross-sectional depth parameter of the spillway's flow before approaching the turbine for each scenario. The total head in the present study case is 3.0 meters with 120 l/s of water discharge. The simulations used ANSYS® Fluent™ for 2D CFD simulation. The tests found that the CFT could attain 80.36% efficiency. Moreover, some water flows over the turbine at a higher rotational speed, leading to a significant loss in turbine performance, called potential loss. This finding indicates that the CFT could harvest the spillway's flow kinetic energy when the flow is not too deep.
TOWARD ADAPTIVE RESEARCH AND TECHNOLOGY DEVELOPMENT FOR FUTURE LIFE
TOWARD ADAPTIVE RESEARCH AND TECHNOLOGY DEVELOPMENT FOR FUTURE LIFE
Civil Engineering Journal
A pico-hydro-type crossflow turbine (CFT) with an off-grid system configuration is a suitable opt... more A pico-hydro-type crossflow turbine (CFT) with an off-grid system configuration is a suitable option to increase the electrification ratio in remote or rural areas because it has a simple shape and can be applied in run-of-river conditions. Yet, a comprehensive study is necessary for the CFT to be applied to run-of-river conditions (low head and extreme fluctuation discharge), since this is categorized as an impulse turbine. One solution to optimize the CFT’s performance in this context is to increase the lift force. Hence, this study investigated the effect of the upper blade of the CFT with convex and curved configurations using the computational fluid dynamics (CFD) method. The CFD transient approach uses a moving mesh feature, and the solver is pressure-based in low-head conditions (5 m pressure). The CFD results and analysis of variance (ANOVA) calculation results from this study reveal that the upper CFT affects the performance of the turbine. The relationship of the CFT perfo...
Prosiding Applicable Innovation of Engineering and Science Research, 2020
Krisis ketenagalistrikan di pedesaan terpencil merupakan isu yang sangat krusial di Indonesia. Di... more Krisis ketenagalistrikan di pedesaan terpencil merupakan isu yang sangat krusial di Indonesia. Dibandingkan dengan opsi lain, turbin cross-flow piko hidro or pico hydro cross-flow turbine (CFT) adalah opsi yang lebih baik dalam menyediakan tenaga listrik untuk daerah pedesaan yang terisolasi. Studi untuk meningkatkan kinerja CFT dapat dilakukan secara analitik, numerik, eksperimental, atau kombinasi dari metode-metode tersebut. Namun perkembangan teknologi komputer membuat studi simulasi numerik menjadi semakin sering dilakukan. Artikel ini menjelaskan pemanfaatan pendekatan computational fluid dynamic (CFD) dalam CFT. Penelitian ini telah menghasilkan model turbulensi k-ε Renormalization Group (RNG) yang direkomendasikan untuk simulasi CFD CFT karena kesalahan relatif absolutnya lebih rendah dari standar k-ε dan Transitional Shear Stress Transport (SST). Tingkat kesalahan relatif absolut untuk model turbulensi RNG k-ε 3,08%, standar k-ε 3,19%, dan SST transisi 3,10%. Sedangkan untuk pendekatan unsteady, enam derajat kebebasan (6-DoF) dianggap lebih akurat daripada moving mesh. Kesalahan relatif absolut untuk 6-DoF sebesar 3,1% dan mesh bergerak sebesar 9,5%. Dengan demikian, berdasarkan kajian tersebut, model turbulensi RNG k-ε dan 6-DoF diusulkan untuk studi CFD CFT piko hidro. Kata Kunci: Pico hydro; Turbin aliran silang; CFD; RANS; Pendekatan 6-DoF ABSTRAK: Crisis electricity in the isolated rural area was a very crucial issue to resolve the electrification ratio problem in Indonesia. Compared to other options, pico hydro cross-flow turbine (CFT) is the better option to provides electrical power for isolated rural areas. Studies to improve CFT performance can be undertaken analytically, numerically, experimentally, or a combination of those methods. However, the development of computer technology makes numerical simulation studies have become increasingly frequent. This paper describes the utilization of the computational fluid dynamic (CFD) approach in the pico hydro CFT method. This review has resulted that the recommended Renormalization Group (RNG) k-ε turbulence model for CFT CFD simulation because its absolute relative error is lower than standard k-ε and transitional Shear Stress Transport (SST). The absolute relative error for the RNG k-ε turbulence model of 3.08%, standard k-ε of 3.19%, and transitional SST of 3.10%. While for the unsteady approach, the six-degrees of freedom (6-DoF) are considered because more accurate than moving mesh. The absolute relative error for 6-DoF of 3.1% and moving mesh of 9.5%. Thus, based on the review, the RNG k-ε turbulence model and 6-DoF are proposed for the pico hydro CFT CFD study.
Indonesian Journal of Engineering and Science, 2021
Energy crisis in particular, electricity in the isolated rural areas of Indonesia is a very cruci... more Energy crisis in particular, electricity in the isolated rural areas of Indonesia is a very crucial issue that needs to be resolve through electrification . Compared to other options, pico hydro cross-flow turbine (CFT) is the better option to provides electrical power for the isolated rural areas. Studies to improve CFT performance can be undertaken analytically, numerically, experimentally, or a combination of those methods. However, the development of computer technology makes numerical simulation studies have become increasingly frequent. This paper describes the utilization of the computational fluid dynamic (CFD) approach in the pico hydro CFT method. This review has resulted that the recommended Renormalization Group (RNG) k-ε turbulence model for CFT CFD simulation because its absolute relative error is lower than standard k-ε and transitional Shear Stress Transport (SST). The absolute relative error for the RNG k-ε turbulence model of 3.08%, standard k-ε of 3.19%, and tran...
Penanganan peralatan yang berada di laut memerlukan perhitungan yang cermat. Kapal yang diperguna... more Penanganan peralatan yang berada di laut memerlukan perhitungan yang cermat. Kapal yang dipergunakan untuk survei seringkali harus melepas jangkar atau melepaskan peralatan ke dalam laut. Untuk peralatan yang mahal biasanya harus dapat kembali diambil dan diangkat ke atas kapal tanpa ada kerusakan. Sebagai contoh sensor tertentu harus ditinggal di dalam atau dasar laut dan ditinggal oleh kapal. Namun alat/sensor tersebut harus tetap dapat dikendalikan dan tidak boleh hilang. Oleh karena itu diperlukan mekanisme untuk tetap menjaga peralatan terhubung secara fisik ke kapal. Cara yang paling masuk akal adalah mengikat peralatan dengan tali. Yang menjadi tantangan tali tersebut dapat terbentang hingga ratusan kilometer. Pada beberapa kasus, tali tersebut harus dapat menahan beban berupa sensor misalnya, kemudian berat tali itu sendiri, terpaan ombak, dan hal-hal lain yang tidak terduga terkait alam. Banyak sekali mekanisme untuk menarik atau mengulur tali. Mekanisme tersebut biasanya b...
Journal of the Brazilian Society of Mechanical Sciences and Engineering
Energy Reports
Breastshot waterwheels are suitable for low head conditions in power plants because they have mor... more Breastshot waterwheels are suitable for low head conditions in power plants because they have more stable efficiency than other types of turbines do. In some cases, computational fluid dynamics (CFD) methods have been utilised for the performance prediction, geometry optimisation or determination of physical phenomena of a breastshot waterwheel because such approaches offer efficiency in terms of energy, time and cost. However, the dynamic approach of the CFD method is different from that in real conditions. For improving the accuracy of CFD simulation results, a feature of 6-degrees of freedom (6-DoF) can be an alternative. This study presented the CFD method using the 6-DoF feature in a breastshot waterwheel. Based on the grid convergence index (GCI) and timestep convergence index (TCI) concepts, 123 000 elements of mesh and a timestep size of 0.002 s were used in this simulation because these parameters fulfilled the GCI and TCI maximum thresholds. The preload values were varied in the simulation, with levels of 75 N•m, 150 N•m, 225 N•m and 300 N•m. Based on the results, the rotation and torque produced by the wheel resulted in a transient period until they naturally became steady. (The rotation and torque were stable). This is the real-world phenomenon of the energy conversion process in a breastshot waterwheel, which cannot be calculated by other features in the CFD method. Thus, the 6-DoF feature can be a suitable option for breastshot waterwheel turbine simulations for performance prediction, geometry optimisation or studying physical phenomena. c
Journal of Energy Mechanical Material and Manufacturing Engineering
Crisis electricity was a crucial issue in the rural area. Crossflow turbine (CFT) in pico in pico... more Crisis electricity was a crucial issue in the rural area. Crossflow turbine (CFT) in pico in pico scale is the best option for electricity provider for rural areas. Due to its usefulness and development of computer technology, computational fluid dynamics method application for CFT study becomes increasingly frequent. This paper compiles the implementation of the computational fluid dynamic (CFD) approach for CFT on a pico scale. Based on the literature, the Renormalization Group (RNG) turbulence model is recommended to predict the flow field that occurs in CFT because its error is lower than others turbulence models, the RNG error of 3.08%, standard of 3.19%, and transitional SST of 3.10%. Furthermore, six-degrees of freedom (6-DoF) is recommended because it has an error of 3.1% than a moving mesh of 9.5% for the unsteady approach. Thus, based on the review, the RNG turbulence model and 6-DoF are recommended for the CFT on the pico scale.
Tujuan penelitian ini adalah untuk mendapatkan data performa dari turbin pelton dengan kapasitas ... more Tujuan penelitian ini adalah untuk mendapatkan data performa dari turbin pelton dengan kapasitas kecil (jumlah 9 sudu dan panjang 29,6 cm) yang digunakan sebagai penggerak turbin. Penelitian ini dilakukan dengan metode eksperimen dan pengukuran secara aktual serta perhitungannya. Metode pengujian meliputi pengaruh dari turbin pelton setelah dirubah sudunya menjadi sudu lengkung pada ketinggian yang berbeda yaitu 1,5 meter, 1 meter dan 0,5 meter dan menggunakan transmisi rantai untuk meneruskan ke generator untuk dirubah menjadi energi listrik. Hasil yang didapat dari pengujian turbin pelton yaitu putaran turbin meningkat dari 38,3 Rpm menjadi 41,7 Rpm pada ketinggian 1,5 meter. Disisi lain beda potensial/tegangan yang dihasilkan juga meningkat dari 0,128 Volt menjadi 0,198 Volt pada ketinggian 1,5 meter. Daya optimum terjadi di ketinggian 1,5 meter yaitu dari 0,0512 watt menjadi 0,0792 watt. Nilai effisiensi tertinggi yaitu 81% pada ketinggian 0,5 meter.
Crisis electricity was a crucial issue in the rural area. Crossflow turbine (CFT) in pico in pico... more Crisis electricity was a crucial issue in the rural area. Crossflow turbine (CFT) in pico in pico scale is the best option for electricity provider for rural areas. Due to its usefulness and development of computer technology, computational fluid dynamics method application for CFT study becomes increasingly frequent. This paper compiles the implementation of the computational fluid dynamic (CFD) approach for CFT on a pico scale. Based on the literature, the Renormalization Group (RNG) k − ɛ turbulence model is recommended to predict the flow field that occurs in CFT because its error is lower than others turbulence models, the RNG k − ɛ error of 3.08%, standard k − ɛ of 3.19%, and transitional SST of 3.10%. Furthermore, six-degrees of freedom (6-DoF) is recommended because it has an error of 3.1% than a moving mesh of 9.5% for the unsteady approach. Thus, based on the review, the RNG k − ɛ turbulence model and 6-DoF are recommended for the CFT on the pico scale.
Studieksperimen pengujian kinerja coolingtowerinduceddraftcounterflow dengan bahan pengisi bambu.... more Studieksperimen pengujian kinerja coolingtowerinduceddraftcounterflow dengan bahan pengisi bambu. Coolingtower yang diuji terbuat dari tong plastik dengan tinggi 93 cm dan diameter dalam 58 cm. Pada tutup tong dipasang sebuah fan yang berfungsi untuk menarik udara panas dan udara lingkungan yang masuk ke dalam coolingtower. Bahan pengisi terbuat dari bambu yang di belah dengan lebar 2 cm, tebal 0,5 cm dan jarak pemasangannya dirapatkan. Ini bertujuan untuk mencari kinerja maksimal dari coolingtower dengan variasi waktu pengujian pada pagi, siang dan malam serta untuk mengetahui beda temperatur yang terjadi pada heater karena adanya beban pemanasan. Berdasarkan nilai approach yang didapatkan bahwa kinerja maksimal terjadi pada coolingtower yang menggunakan filler, karena nilai approachnya lebih rendah daripada coolingtower yang tanpa filler dengan nilai approach rata – rata pada pagi, siang, dan malam hari masing–masing sebesar 13,42 °C, 13 °C, dan 12,9 °C. Pada studi ini, didapatk...
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Papers by Aji Putro Prakoso