Pub Date : 2023-07-10DOI: 10.1177/09576509231188555
Asif Ali, S. Shuja, BS Yilbas
Inclusion of porous structures in micro-channels enhances heat transfer rates in energy harvesting devices, which signifies as the working fluid becomes a nanofluid. The present study compares the thermal performance of CuO-water, TiO2-water and graphene-water nanofluids in a sinusoidal channel with a porous insert. The flow and heat transfer characteristics are simulated and the effects of volumetric fraction of nanofluids, Reynolds number ( Re), porous insert width, and its permeability on the flow and temperature fields are examined. The findings reveal that CuO-water nanofluid results in higher heat transfer rates than those of other nanofluids considered. Graphene-water nanofluid gives rise to lower performance than that of CuO-water nanofluid in terms of convection heat transfer despite the fact that graphene has higher thermal conductivity than CuO. In this case, a decrease in Nusselt number of as much as 6.34% is observed for CuO-water nanofluid among all the cases considered for the Reynolds number of 100. Increasing the permeability of the porous insert slightly enhances (∼0.24%) the average Nusselt number. The porous insert with a small width in the channel improves the heat transfer rates (2.25% increase in Nusselt number), i.e. the average Nusselt number reduces as the porous insert width increases.
{"title":"Thermal performance of nanofluids in a sinusoidal channel with embedded porous region","authors":"Asif Ali, S. Shuja, BS Yilbas","doi":"10.1177/09576509231188555","DOIUrl":"https://doi.org/10.1177/09576509231188555","url":null,"abstract":"Inclusion of porous structures in micro-channels enhances heat transfer rates in energy harvesting devices, which signifies as the working fluid becomes a nanofluid. The present study compares the thermal performance of CuO-water, TiO2-water and graphene-water nanofluids in a sinusoidal channel with a porous insert. The flow and heat transfer characteristics are simulated and the effects of volumetric fraction of nanofluids, Reynolds number ( Re), porous insert width, and its permeability on the flow and temperature fields are examined. The findings reveal that CuO-water nanofluid results in higher heat transfer rates than those of other nanofluids considered. Graphene-water nanofluid gives rise to lower performance than that of CuO-water nanofluid in terms of convection heat transfer despite the fact that graphene has higher thermal conductivity than CuO. In this case, a decrease in Nusselt number of as much as 6.34% is observed for CuO-water nanofluid among all the cases considered for the Reynolds number of 100. Increasing the permeability of the porous insert slightly enhances (∼0.24%) the average Nusselt number. The porous insert with a small width in the channel improves the heat transfer rates (2.25% increase in Nusselt number), i.e. the average Nusselt number reduces as the porous insert width increases.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74394611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-27DOI: 10.1177/09576509231182227
Jiefeng Wang, Jianwu Li, Yujuan Zhao, Jianming Li, Rong Li, Liangmou Li
This paper numerically investigates the vortex and film composite cooling performance under rotating conditions. The cooling performance of the adiabatic and conjugate models is compared under the range of 0–4000 r/min. The conjugate model contains the fluid region: the cascade, the film holes, and the internal vortex cooling chamber, as well as the solid region: the blade material between the internal flow and the mainstream flow. The adiabatic model is established by removing the blade material part in the conjugate model. The dimensionless temperature θ inversely proportional to the temperature is adopted. Results show that the blade leading edge temperature doesn’t vary linearly with the rotating speed. The stagnation line of the mainstream flow on the blade leading edge moves from the pressure surface to the suction surface. The maximum θ appears at 1500 r/min when the stagnation line stays certainly on the row of film holes located on the pressure surface and is 7.86% higher than the minimum θ. The minimum θ appears at 2500 r/min when the stagnation line stays on the position between the rows of film holes. The distribution of θ is much uniform, and the value of θ is much higher in the conjugate cases than the adiabatic cases due to the heat conduction through the blade material. The highest aerodynamic parameter appears at 2000 r/min due to its relatively low blade leading edge temperature and low coolant consumption and is 41% higher than the aerodynamic parameter at 0 r/min.
{"title":"Numerical investigation on conjugate heat transfer characteristics of film and vortex composite cooling under rotating conditions","authors":"Jiefeng Wang, Jianwu Li, Yujuan Zhao, Jianming Li, Rong Li, Liangmou Li","doi":"10.1177/09576509231182227","DOIUrl":"https://doi.org/10.1177/09576509231182227","url":null,"abstract":"This paper numerically investigates the vortex and film composite cooling performance under rotating conditions. The cooling performance of the adiabatic and conjugate models is compared under the range of 0–4000 r/min. The conjugate model contains the fluid region: the cascade, the film holes, and the internal vortex cooling chamber, as well as the solid region: the blade material between the internal flow and the mainstream flow. The adiabatic model is established by removing the blade material part in the conjugate model. The dimensionless temperature θ inversely proportional to the temperature is adopted. Results show that the blade leading edge temperature doesn’t vary linearly with the rotating speed. The stagnation line of the mainstream flow on the blade leading edge moves from the pressure surface to the suction surface. The maximum θ appears at 1500 r/min when the stagnation line stays certainly on the row of film holes located on the pressure surface and is 7.86% higher than the minimum θ. The minimum θ appears at 2500 r/min when the stagnation line stays on the position between the rows of film holes. The distribution of θ is much uniform, and the value of θ is much higher in the conjugate cases than the adiabatic cases due to the heat conduction through the blade material. The highest aerodynamic parameter appears at 2000 r/min due to its relatively low blade leading edge temperature and low coolant consumption and is 41% higher than the aerodynamic parameter at 0 r/min.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90536524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-21DOI: 10.1177/09576509231184921
Wanting Sun, Min Li, Yuewei Fan, Bo Zhu
It is widely concerned that the non-ideal design of characteristic parameters of throat pipe of jet pump leads to the low pumping efficiency. The paper studies the pumping efficiency of jet pump under different characteristic parameters through numerical calculation to determine the influences of single parameter on pumping efficiency. And the coupling influences of parameters are predicted through XGBoost technology. The research shows that the coupling relation between the pumping efficiency of jet pump and multiple characteristic parameters can be predicted with the accuracy of 98.83%. The reasonable choice of characteristic parameters can improve pumping efficiency by 23.6%. The research will help designers to look for the best coupling of jet pump parameters accurately through numerical calculation and machine learning technologies.
{"title":"Exploration of the mechanism and prediction of jet pump feature structure optimization for the enhanced pumping performance","authors":"Wanting Sun, Min Li, Yuewei Fan, Bo Zhu","doi":"10.1177/09576509231184921","DOIUrl":"https://doi.org/10.1177/09576509231184921","url":null,"abstract":"It is widely concerned that the non-ideal design of characteristic parameters of throat pipe of jet pump leads to the low pumping efficiency. The paper studies the pumping efficiency of jet pump under different characteristic parameters through numerical calculation to determine the influences of single parameter on pumping efficiency. And the coupling influences of parameters are predicted through XGBoost technology. The research shows that the coupling relation between the pumping efficiency of jet pump and multiple characteristic parameters can be predicted with the accuracy of 98.83%. The reasonable choice of characteristic parameters can improve pumping efficiency by 23.6%. The research will help designers to look for the best coupling of jet pump parameters accurately through numerical calculation and machine learning technologies.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136354513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-19DOI: 10.1177/09576509231181547
Cheikh Brahim Abed, V. Nguyen, S. Khelladi, M. Deligant, A. Danlos, F. Bakir
The use of a counter-rotating rotor in turbomachines can be a solution to improve performances by allowing reduction in size and weight, especially compared to multistage configuration. The present study aims are to demonstrate another advantage of the counter-rotating rotors: their application to expand the operating range of centrifugal compressors toward extremely low flow rates based on an active control method. This method was performed on two different counter-rotating configurations. The principle of the active control method is to adjust independently the rotation speed of each rotor to push back the instability appearance. Experimental results show that reducing the rotation speed of the upstream-rotor while fixing the speed of the downstream rotor can push the instability phenomenon toward a lower mass flow rate while decreasing the pressure rise and efficiency. Co-rotating mode is applied to push further the stable region toward low mass flow rates allowing a significant extension of the operating range. The experimental results reveal that the map width is shifted by about 50% over the studied range toward a lower mass flow rate for both counter-rotating centrifugal compressors when using the control method. This can be achieved when the absolute value of the upstream-rotor speed is within the range of 48%–61% of the rotational speed of the downstream rotor.
{"title":"A novel experimental control method to suppress instability in a centrifugal compressor with two counter and co-rotating rotors","authors":"Cheikh Brahim Abed, V. Nguyen, S. Khelladi, M. Deligant, A. Danlos, F. Bakir","doi":"10.1177/09576509231181547","DOIUrl":"https://doi.org/10.1177/09576509231181547","url":null,"abstract":"The use of a counter-rotating rotor in turbomachines can be a solution to improve performances by allowing reduction in size and weight, especially compared to multistage configuration. The present study aims are to demonstrate another advantage of the counter-rotating rotors: their application to expand the operating range of centrifugal compressors toward extremely low flow rates based on an active control method. This method was performed on two different counter-rotating configurations. The principle of the active control method is to adjust independently the rotation speed of each rotor to push back the instability appearance. Experimental results show that reducing the rotation speed of the upstream-rotor while fixing the speed of the downstream rotor can push the instability phenomenon toward a lower mass flow rate while decreasing the pressure rise and efficiency. Co-rotating mode is applied to push further the stable region toward low mass flow rates allowing a significant extension of the operating range. The experimental results reveal that the map width is shifted by about 50% over the studied range toward a lower mass flow rate for both counter-rotating centrifugal compressors when using the control method. This can be achieved when the absolute value of the upstream-rotor speed is within the range of 48%–61% of the rotational speed of the downstream rotor.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73880037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-16DOI: 10.1177/09576509231183037
Varun Goel, A. Dwivedi, A. Choudhary
Solar air heaters (SAHs) are widely accepted and used for drying and heating purposes. Numerous methodologies are available for augmentation of the performance of a SAH but the application of artificial roughness underside the absorber plate is reported to bean efficient one. This study aims to present the effects of using hybrid artificial roughness combining the transverse ribs along with discrete inclined ribs, on the thermo-hydraulic performance of roughened SAH. The response surface methodology (RSM) is utilized for the design of experiments to investigate the influence of relative roughness height (0.018 ≤ e/ D ≤ 0.036), relative roughness pitch (5 ≤ p/ e ≤ 15), attack angle (45° ≤ α ≤ 75°), and Reynolds number (1,900 ≤ Re ≤ 20,300) as input parameters. The empirical equations are developed for Nusselt number, friction factor, and thermo-hydraulic performance parameter based on the regression analysis. An integrated analytical hierarchy process-based weighted aggregated sum product assessment (AHP-WASPAS) method is used to evaluate an optimal parametric combination ( e/ D = 0.036, p/ e = 15, α = 75°, and Re = 20,300). The results are supported by the corresponding experimental outcomes. Also, the sensitivity analysis and rank reversal tests performed as qualitative assessment procedures for the results obtained from the proposed strategy. The proposed decision framework is reported to be very sensitive to several criteria weight fluctuations with maximum and least deviations of 15.41% and 2.56% for δWjp = +50% and δWjp = −10%, respectively. Further, the obtained results confirm the robustness of aopted decisional scheme with just one rank reversal.
太阳能空气加热器(SAHs)被广泛接受并用于干燥和加热目的。有许多方法可用于增强SAH的性能，但据报道，在吸收板下面应用人工粗糙度是一种有效的方法。本研究旨在展示混合人工粗糙度结合横向肋和离散斜肋对粗糙SAH热水力性能的影响。利用响应面法(RSM)进行实验设计，研究相对粗糙度高度(0.018≤e/ D≤0.036)、相对粗糙度间距(5≤p/ e≤15)、攻角(45°≤α≤75°)和雷诺数(1,900≤Re≤20,300)作为输入参数的影响。在回归分析的基础上，建立了Nusselt数、摩擦系数和热工性能参数的经验方程。采用基于综合层次分析法的加权总和产品评价(AHP-WASPAS)方法对最优参数组合(e/ D = 0.036, p/ e = 15， α = 75°，Re = 20,300)进行评价。所得结果得到了相应实验结果的支持。此外，灵敏度分析和等级反转测试作为从拟议策略中获得的结果的定性评估程序进行。据报道，所提出的决策框架对几个标准权重波动非常敏感，δWjp = +50%和δWjp = - 10%的最大和最小偏差分别为15.41%和2.56%。进一步，所得结果证实了所采用的决策方案在一次秩反转情况下的鲁棒性。
{"title":"Parametric optimization of hybrid artificial roughness used in solar air heaters using multiple criteria decision making techniques","authors":"Varun Goel, A. Dwivedi, A. Choudhary","doi":"10.1177/09576509231183037","DOIUrl":"https://doi.org/10.1177/09576509231183037","url":null,"abstract":"Solar air heaters (SAHs) are widely accepted and used for drying and heating purposes. Numerous methodologies are available for augmentation of the performance of a SAH but the application of artificial roughness underside the absorber plate is reported to bean efficient one. This study aims to present the effects of using hybrid artificial roughness combining the transverse ribs along with discrete inclined ribs, on the thermo-hydraulic performance of roughened SAH. The response surface methodology (RSM) is utilized for the design of experiments to investigate the influence of relative roughness height (0.018 ≤ e/ D ≤ 0.036), relative roughness pitch (5 ≤ p/ e ≤ 15), attack angle (45° ≤ α ≤ 75°), and Reynolds number (1,900 ≤ Re ≤ 20,300) as input parameters. The empirical equations are developed for Nusselt number, friction factor, and thermo-hydraulic performance parameter based on the regression analysis. An integrated analytical hierarchy process-based weighted aggregated sum product assessment (AHP-WASPAS) method is used to evaluate an optimal parametric combination ( e/ D = 0.036, p/ e = 15, α = 75°, and Re = 20,300). The results are supported by the corresponding experimental outcomes. Also, the sensitivity analysis and rank reversal tests performed as qualitative assessment procedures for the results obtained from the proposed strategy. The proposed decision framework is reported to be very sensitive to several criteria weight fluctuations with maximum and least deviations of 15.41% and 2.56% for δWjp = +50% and δWjp = −10%, respectively. Further, the obtained results confirm the robustness of aopted decisional scheme with just one rank reversal.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86594880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pumped storage power plants are doomed to play a more important role in peak-valley shifting hence the demand for operation stability is gradually regarded as an equal important criterion as high efficiency. In our paper, new concepts, namely “swept,” “bowed (lean),” and “twisted” are introduced to systematic innovative design the geometry of high-pressure side (HPS) of a pump-turbine runner. Thereafter, a multi-objective optimization process, which consists of design of experiment (DoE), meta model generation, multi-objective genetic algorithm (MOGA), self-organization map (SOM) and takes both high efficiency and stability discipline into account is produced. The final optimization plan is selected and testified numerically. Compared to the original runner, the efficiency is improved from 91.7% to 91.9% at pump mode and improved from 92.3% to 92.8% at turbine mode. Moreover, the S margin is increased from 89.34° to 90.23° at small GVO and increased from 79.56° to 80.29° at large GVO. Besides, hump unsteady region is completely eliminated. Moreover, the flow characteristic comparation is conducted based on local hydraulic loss rate (LHLR) method. For design points, the optimized runner obviously decreases the hydraulic loss in hub and middle part of runner domain for turbine mode and slightly decrease the hydraulic loss in stay vane region for pump mode. For unsteady characteristics, HPS can better adjust the hydraulic loss distribution in corresponding discharge operating points, largely decreasing S unsteady characteristic in turbine mode and eliminating hump unsteady characteristic in pump mode. We believe that the methods proposed in our paper can bring the design of hydraulic machinery to a new level.
{"title":"Optimization on high-pressure side of pump-turbine runner based on high efficiency and stability criterion via multi-objective genetic algorithm method","authors":"Yonglin Qin, Deyou Li, Hongjie Wang, Zhansheng Liu, Xianzhu Wei, Xiao-hang Wang, Yongjian Song","doi":"10.1177/09576509231181933","DOIUrl":"https://doi.org/10.1177/09576509231181933","url":null,"abstract":"Pumped storage power plants are doomed to play a more important role in peak-valley shifting hence the demand for operation stability is gradually regarded as an equal important criterion as high efficiency. In our paper, new concepts, namely “swept,” “bowed (lean),” and “twisted” are introduced to systematic innovative design the geometry of high-pressure side (HPS) of a pump-turbine runner. Thereafter, a multi-objective optimization process, which consists of design of experiment (DoE), meta model generation, multi-objective genetic algorithm (MOGA), self-organization map (SOM) and takes both high efficiency and stability discipline into account is produced. The final optimization plan is selected and testified numerically. Compared to the original runner, the efficiency is improved from 91.7% to 91.9% at pump mode and improved from 92.3% to 92.8% at turbine mode. Moreover, the S margin is increased from 89.34° to 90.23° at small GVO and increased from 79.56° to 80.29° at large GVO. Besides, hump unsteady region is completely eliminated. Moreover, the flow characteristic comparation is conducted based on local hydraulic loss rate (LHLR) method. For design points, the optimized runner obviously decreases the hydraulic loss in hub and middle part of runner domain for turbine mode and slightly decrease the hydraulic loss in stay vane region for pump mode. For unsteady characteristics, HPS can better adjust the hydraulic loss distribution in corresponding discharge operating points, largely decreasing S unsteady characteristic in turbine mode and eliminating hump unsteady characteristic in pump mode. We believe that the methods proposed in our paper can bring the design of hydraulic machinery to a new level.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85582632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-04DOI: 10.1177/09576509231180421
Zhiyuan Li, Kai Zhang, Zhigang Li, Jun Li
The turbine vane inlet downstream of the lean premixed combustor presents nonuniform distributions of velocity and temperature. For obtaining swirling inflow profiles close to reality, the simulated non-reacting combustor is designed firstly. Applying these profiles as inflow boundary conditions, the effects of realistic swirling inflow on the turbine vane endwall aerothermal characteristics and film cooling performance are numerically investigated through solving the three-dimensional Reynolds-Averaged Navier-Stokes equations coupled with the shear stress transfer ([Formula: see text]) turbulence model. Two swirling orientations (anticlockwise and clockwise) and five swirling core pitch-wise positions (aligned with vane 1 to vane 2) are considered in the current work. The results indicate that the residual vortices in the vane passage are strengthened and move with the swirling core along the pitch-wise direction. The migration of the horseshoe vortex is controlled by this movement. The shrinkage or expansion of the separation line of the horseshoe vortex can be observed under the anticlockwise and clockwise swirling inflow conditions respectively. The anticlockwise swirling inflow results in a larger aerodynamic loss by a 10%–35% increase of the laterally [Formula: see text]. The high Nu region near the pressure side surface enlarges and the area-averaged Nu at [Formula: see text] increases from 2337.9 to 2878.3. For the cases with clockwise swirling inflow, the area of the hot ring is enlarged and the Nu downstream of the row 3 film holes is decreased. As for the film cooling performance, the endwall coverage area shrinks and the phantom cooling area enlarges when the anticlockwise swirling core is aligned with vane 2. The endwall loses the protection from the row 3 film holes and the cooling failure ([Formula: see text]) occurs at [Formula: see text] when the swirling core is aligned with the vane passage. This is an extremely bad phenomenon that should be avoided. Among all cases, the highest endwall area-averaged [Formula: see text] (0.122) is obtained when the clockwise swirling core is aligned with vane 1. The largest endwall coverage area is achieved when the clockwise swirling core is aligned with vane 2.
稀薄预混燃烧室下游涡轮叶片入口呈现速度和温度的非均匀分布。为了获得更接近实际的旋流流型，首先设计了模拟非反应燃烧室。将这些剖面作为流入边界条件，通过求解三维reynolds - average Navier-Stokes方程，结合剪切应力传递(公式见文)湍流模型，数值研究了现实涡旋流入对涡轮叶片端壁气动热特性和气膜冷却性能的影响。在目前的工作中，考虑了两个旋转方向(逆时针和顺时针)和五个旋转核心螺距方向位置(与叶片1到叶片2对齐)。结果表明，叶片通道内的残余涡增强，并随旋流芯沿节距方向移动。这种运动控制了马蹄形涡的迁移。在顺时针和逆时针旋流入流条件下，分别观察到马蹄涡分离线的收缩和扩张。逆时针旋流的流入导致了更大的气动损失，横向增加了10%-35%[公式:见文]。靠近压力侧面的高Nu区增大，面积平均Nu在[公式见文]处由2337.9增大到2878.3。顺时针旋流情况下，热环面积增大，第3排膜孔下游的Nu减小。在气膜冷却性能方面，当逆时针旋流芯与叶片2对齐时，端壁覆盖面积缩小，幻象冷却面积增大。端壁失去了对第3排膜孔的保护，当旋心与叶片通道对齐时，冷却失效([公式:见文])发生在[公式:见文]。这是一个非常糟糕的现象，应该避免。在所有情况中，顺时针旋转芯与叶片1对齐时，端壁平均面积最大[公式见文](0.122)。当顺时针旋转的核心与叶片2对齐时，实现了最大的端壁覆盖面积。
{"title":"Turbine vane endwall aerothermal and film cooling performance considering realistic swirling inflow conditions","authors":"Zhiyuan Li, Kai Zhang, Zhigang Li, Jun Li","doi":"10.1177/09576509231180421","DOIUrl":"https://doi.org/10.1177/09576509231180421","url":null,"abstract":"The turbine vane inlet downstream of the lean premixed combustor presents nonuniform distributions of velocity and temperature. For obtaining swirling inflow profiles close to reality, the simulated non-reacting combustor is designed firstly. Applying these profiles as inflow boundary conditions, the effects of realistic swirling inflow on the turbine vane endwall aerothermal characteristics and film cooling performance are numerically investigated through solving the three-dimensional Reynolds-Averaged Navier-Stokes equations coupled with the shear stress transfer ([Formula: see text]) turbulence model. Two swirling orientations (anticlockwise and clockwise) and five swirling core pitch-wise positions (aligned with vane 1 to vane 2) are considered in the current work. The results indicate that the residual vortices in the vane passage are strengthened and move with the swirling core along the pitch-wise direction. The migration of the horseshoe vortex is controlled by this movement. The shrinkage or expansion of the separation line of the horseshoe vortex can be observed under the anticlockwise and clockwise swirling inflow conditions respectively. The anticlockwise swirling inflow results in a larger aerodynamic loss by a 10%–35% increase of the laterally [Formula: see text]. The high Nu region near the pressure side surface enlarges and the area-averaged Nu at [Formula: see text] increases from 2337.9 to 2878.3. For the cases with clockwise swirling inflow, the area of the hot ring is enlarged and the Nu downstream of the row 3 film holes is decreased. As for the film cooling performance, the endwall coverage area shrinks and the phantom cooling area enlarges when the anticlockwise swirling core is aligned with vane 2. The endwall loses the protection from the row 3 film holes and the cooling failure ([Formula: see text]) occurs at [Formula: see text] when the swirling core is aligned with the vane passage. This is an extremely bad phenomenon that should be avoided. Among all cases, the highest endwall area-averaged [Formula: see text] (0.122) is obtained when the clockwise swirling core is aligned with vane 1. The largest endwall coverage area is achieved when the clockwise swirling core is aligned with vane 2.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75644999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-01DOI: 10.1177/09576509231176623
M. Kumar, Jeevanjyoti Chakraborty, P. K. Das
In the present study, the combined effect of the temperature difference across the electrode-electrolyte interface and the finite size of ions non-idealities on the cation interdiffusion is investigated using a mathematical model. Here, we build on and add significantly to our previous work 1 where the study was limited only to the finite effect of ions. Considering each non-ideality/effect separately, the diffusion of manganese (Mn3+) ions decreases about 50 nm for a temperature difference (∆ T) of 50 K, and 31 nm for a finite size parameter ( ν) of 1.826. However, it is decreased by 54 nm considering both effects combindly for ∆ T = 50 K and ν = 1.75. Further, under individual effects, the highest electric potential drop is 0.32 for a ∆ T = 50 K and 0.27 for a ν = 1.75. Under combined effects, the electric potential drop is about 0.85 for ∆ T = 50 K and ν = 1.75. A significant variation is observed in the diffusion of Zr4+, Y3+ and Mn3+ ions and the overall electric potential. It is anticipated that the consideration of these effects/non-idealities will help in the better understanding of cation interdiffusion, and contribute towards performance enhancement of SOFCs.
{"title":"Combined effect of temperature difference across interface and finite size of the ions on interdiffusion in SOFC","authors":"M. Kumar, Jeevanjyoti Chakraborty, P. K. Das","doi":"10.1177/09576509231176623","DOIUrl":"https://doi.org/10.1177/09576509231176623","url":null,"abstract":"In the present study, the combined effect of the temperature difference across the electrode-electrolyte interface and the finite size of ions non-idealities on the cation interdiffusion is investigated using a mathematical model. Here, we build on and add significantly to our previous work 1 where the study was limited only to the finite effect of ions. Considering each non-ideality/effect separately, the diffusion of manganese (Mn3+) ions decreases about 50 nm for a temperature difference (∆ T) of 50 K, and 31 nm for a finite size parameter ( ν) of 1.826. However, it is decreased by 54 nm considering both effects combindly for ∆ T = 50 K and ν = 1.75. Further, under individual effects, the highest electric potential drop is 0.32 for a ∆ T = 50 K and 0.27 for a ν = 1.75. Under combined effects, the electric potential drop is about 0.85 for ∆ T = 50 K and ν = 1.75. A significant variation is observed in the diffusion of Zr4+, Y3+ and Mn3+ ions and the overall electric potential. It is anticipated that the consideration of these effects/non-idealities will help in the better understanding of cation interdiffusion, and contribute towards performance enhancement of SOFCs.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82293283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For the purpose of studying the effect of structural changes in the dilution zone on the main performance evaluation parameters of the combustor, a can-type combustor of a micro gas turbine containing 16 dilution holes was used as the original structure. Seven optimization cases were designed by adjusting the number of dilution holes and the area of single hole in the range of hole numbers from 8 to 28 while keeping the total area of dilution holes. The main conclusions obtained by the numerical simulation study are as follows. The total flow of the dilution zone decreases with the number of holes reduce but due to the increase of single hole flow with the area, the airflow rigidity is significantly enhanced, so the entire airflow is disturbed more strongly and the dilution effect is strengthened. In general, the total pressure loss of the combustor presented an increasing trend with the decrease in the number of holes, and the pressure loss reaches a minimum value of 3400 Pa when the number of holes is 14. The combustion efficiency decreased as the number of holes increased, when the hole numbers increased to 20, the combustion efficiency dropped abruptly below 95%. The variation tendency of outlet temperature distribution factor (OTDF) is generally consistent with the combustion efficiency, and the minimum OTDF is 0.29 for the number of holes of 28. In summary, compared with the original structure with 16 holes, the OTDF decreases by 7.69%, the NOx concentration decreases by 16.67%, and the combustion efficiency increases by 3.1% when the number of holes is 8. Although the total pressure loss is increased by 8%, it is still within a reasonable range. Therefore the combustor with 8 holes can be considered a better optimized case.
{"title":"Cooling characteristics of dilution holes in can-type combustor of micro gas turbine","authors":"Luyu Wang, Jiange Liu, Yunyun Wang, Zaiguo Fu, Peifen Weng","doi":"10.1177/09576509231176927","DOIUrl":"https://doi.org/10.1177/09576509231176927","url":null,"abstract":"For the purpose of studying the effect of structural changes in the dilution zone on the main performance evaluation parameters of the combustor, a can-type combustor of a micro gas turbine containing 16 dilution holes was used as the original structure. Seven optimization cases were designed by adjusting the number of dilution holes and the area of single hole in the range of hole numbers from 8 to 28 while keeping the total area of dilution holes. The main conclusions obtained by the numerical simulation study are as follows. The total flow of the dilution zone decreases with the number of holes reduce but due to the increase of single hole flow with the area, the airflow rigidity is significantly enhanced, so the entire airflow is disturbed more strongly and the dilution effect is strengthened. In general, the total pressure loss of the combustor presented an increasing trend with the decrease in the number of holes, and the pressure loss reaches a minimum value of 3400 Pa when the number of holes is 14. The combustion efficiency decreased as the number of holes increased, when the hole numbers increased to 20, the combustion efficiency dropped abruptly below 95%. The variation tendency of outlet temperature distribution factor (OTDF) is generally consistent with the combustion efficiency, and the minimum OTDF is 0.29 for the number of holes of 28. In summary, compared with the original structure with 16 holes, the OTDF decreases by 7.69%, the NOx concentration decreases by 16.67%, and the combustion efficiency increases by 3.1% when the number of holes is 8. Although the total pressure loss is increased by 8%, it is still within a reasonable range. Therefore the combustor with 8 holes can be considered a better optimized case.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88027870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-25DOI: 10.1177/09576509231177104
Xianghua Cheng, Qiumei Yu, W. Ji, Junmei Wu, Yaochang He, W. Tao
For the blades of gas turbine, the traditional internal ribs have a great impact on the film cooling heat transfer of blade external surface. In this study, SST k-ω turbulence coupled with transition model is adopted to study the effects of angled ribbed passages on external flow and heat transfer characteristics. The detailed flow characteristics were analyzed for two vertically placed flat-plate channels with the blowing ratios of 0.5∼2. The computational model includes a single film hole ( D = 20 mm) with a jet angle of 35°. Four different rib orientations in the secondary flow channels are designed. They are no rib, oblique rib 1 (30° angle from the horizontal line), oblique rib 2 (symmetrical to oblique rib 1), and straight rib. Compared with ribless channel, the average adiabatic film cooling effectiveness of straight rib, Oblique rib 1, Oblique rib 2 are 2.3, 2.2, and 1.9 times higher at different Reynolds numbers, respectively. Taking the film hole as the origin, Oblique rib 2 can greatly improve the overall cooling effectiveness. Oblique rib 1 can improve the cooling effectiveness of the farther downstream wall surface. The comparison of film cooling efficiency, coolant coverage area, flow behavior inside the film hole and that in the downstream, heat transfer and transition behavior for different channels are also analyzed separately. Through the investigations, it helps to understand the effects of internal rib angle on the flow, friction factor and heat transfer outside the film holes.
{"title":"Numerical study on the effect of different internal angled ribs on the external film cooling performance","authors":"Xianghua Cheng, Qiumei Yu, W. Ji, Junmei Wu, Yaochang He, W. Tao","doi":"10.1177/09576509231177104","DOIUrl":"https://doi.org/10.1177/09576509231177104","url":null,"abstract":"For the blades of gas turbine, the traditional internal ribs have a great impact on the film cooling heat transfer of blade external surface. In this study, SST k-ω turbulence coupled with transition model is adopted to study the effects of angled ribbed passages on external flow and heat transfer characteristics. The detailed flow characteristics were analyzed for two vertically placed flat-plate channels with the blowing ratios of 0.5∼2. The computational model includes a single film hole ( D = 20 mm) with a jet angle of 35°. Four different rib orientations in the secondary flow channels are designed. They are no rib, oblique rib 1 (30° angle from the horizontal line), oblique rib 2 (symmetrical to oblique rib 1), and straight rib. Compared with ribless channel, the average adiabatic film cooling effectiveness of straight rib, Oblique rib 1, Oblique rib 2 are 2.3, 2.2, and 1.9 times higher at different Reynolds numbers, respectively. Taking the film hole as the origin, Oblique rib 2 can greatly improve the overall cooling effectiveness. Oblique rib 1 can improve the cooling effectiveness of the farther downstream wall surface. The comparison of film cooling efficiency, coolant coverage area, flow behavior inside the film hole and that in the downstream, heat transfer and transition behavior for different channels are also analyzed separately. Through the investigations, it helps to understand the effects of internal rib angle on the flow, friction factor and heat transfer outside the film holes.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88856553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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