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Symmetry
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Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics
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Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: closed (7 June 2024) | Viewed by 25217

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Zheng Xu

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Guest Editor
School of Aerospace, Hangzhou Innovation Institute, Beihang University, Hangzhou 310023, China
Interests: aerospace engine; engineering thermophysics
Special Issues, Collections and Topics in MDPI journals
Dr. Guangze Li

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Guest Editor
School of Aerospace, Hangzhou Innovation Institute, Beihang University, Hangzhou 310023, China
Interests: combustion; engineering thermophysics
Special Issues, Collections and Topics in MDPI journals
Dr. Bin Zhang

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Guest Editor
School of Aerospace, Hangzhou Innovation Institute, Beihang University, Hangzhou 310023, China
Interests: aerospace engine; engineering thermophysics; environmental science and structural strength assessment
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Carbon neutrality and symmetry in power engineering and engineering thermophysics is a hot research topic receiving much attention, and it is rather significant in the development of power systems such as aero-engines and internal combustion engines. In response to global climate change, “carbon peak” and “carbon neutral” have become popular keywords. As one of the main contributors of carbon emissions, power systems are confronted with great challenges in terms of their energy conservation and emissions reduction. For example, improving power system efficiency and developing green alternative fuels are essential ways to reduce carbon emissions. In addition, the symmetrical design of power system structures has important influences on carbon neutrality, as do symmetry or asymmetric fluid properties and lightweight structure, with numerous studies exploring these topics in an attempt to address many novel questions. Given the strict requirements of carbon emission, a breakthrough is needed in the low-carbon technologies of power systems. Therefore, discussing and summarizing the latest outstanding research on carbon neutrality and symmetry in power engineering and engineering thermophysics is of great significance.

The main goal of this Special Issue is to present a collection of manuscripts focused on the frontier research and future challenges of carbon neutrality and symmetry in power engineering and engineering thermophysics. Relevant topics include, but are not limited to:

  • Carbon neutrality and sustainable alternative fuels
  • Aero-engine carbon neutrality and symmetry
  • Carbon neutral technologies for internal combustion engines
  • Combustion carbon neutral and symmetry
  • Multiphase flow carbon neutral and symmetry
  • Carbon neutral and symmetry in heat and mass transfer
  • Airworthiness carbon neutrality and symmetry
  • Particle measurement and characterization in carbon neutrality and symmetry
  • Interdisciplinary issues in carbon neutrality and symmetry

You are also welcome to present your work at “The 1st International Conference on Aerospace Power Engineering and Engineering Thermophysics, Zhongfa Aviation University (APEET, October 2022, Hangzhou, China)” and “Symposium on Transportation Energy and Intelligent Power, (TEIP, Chinese Society for Internal Combustion Engines, October 2022, Beijing, China)”.

Dr. Zheng Xu
Dr. Guangze Li
Dr. Bin Zhang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

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Related Special Issue

Published Papers (13 papers)

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Editorial

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7 pages, 163 KiB  
Editorial
The Optimization of Aviation Technologies and Design Strategies for a Carbon-Neutral Future
by Zheng Xu, Jinze Pei and Yue Song
Symmetry 2024, 16(9), 1226; https://doi.org/10.3390/sym16091226 - 18 Sep 2024
Viewed by 819
Abstract
This Special Issue systematically reviews and summarizes the latest research into carbon neutrality technology and symmetry principles in power engineering and engineering thermophysics [...] Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)

Research

Jump to: Editorial

23 pages, 4091 KiB  
Article
Two-Stage Robust Optimization for Large Logistics Parks to Participate in Grid Peak Shaving
by Jiu Zhou, Jieni Zhang, Zhaoming Qiu, Zhiwen Yu, Qiong Cui and Xiangrui Tong
Symmetry 2024, 16(8), 949; https://doi.org/10.3390/sym16080949 - 24 Jul 2024
Viewed by 1085
Abstract
As new energy integration increases, power grid load curves become steeper. Large logistics parks, with their substantial cooling load, show great peak shaving potential. Leveraging this load while maintaining staff comfort, product quality, and operational costs is a major challenge. This paper proposes [...] Read more.
As new energy integration increases, power grid load curves become steeper. Large logistics parks, with their substantial cooling load, show great peak shaving potential. Leveraging this load while maintaining staff comfort, product quality, and operational costs is a major challenge. This paper proposes a two-stage robust optimization method for large logistics parks to participate in grid peak shaving. First, a Cooling Load’s Economic Contribution (CLEC) index is introduced, integrating the Predicted Mean Vote (PMV) and Sales Pressure Index (SPI). Then, an optimization model is established, accounting for renewable energy uncertainties and maximizing large logistics parks’ participation in peak shaving. Results illustrate that the proposed method leads to a reduction in the peak shaving pressure on the distribution network. Specifically, under the scenario tolerating the maximum potential uncertainty in renewable energy output, the absolute peak-to-valley difference and fluctuation variance of the park’s net load are decreased by 45.82% and 54.59%, respectively. Furthermore, the PMV and the SPI indexes are reduced by 39.12% and 26.36%, respectively. In comparison with the determined optimization method, despite a slight cost increase of 20.06%, the proposed method significantly reduces EDR load shedding by 98.1%. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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16 pages, 5048 KiB  
Article
A Deterministic Calibration Method for the Thermodynamic Model of Gas Turbines
by Zhen Jiang, Xi Wang, Shubo Yang and Meiyin Zhu
Symmetry 2024, 16(5), 522; https://doi.org/10.3390/sym16050522 - 26 Apr 2024
Viewed by 874
Abstract
Performance adaptation is an effective way to improve the accuracy of gas turbine performance models. Although current performance adaptation methods, such as those using genetic algorithms or evolutionary computation to modify component characteristic maps, are useful for finding good solutions, they are essentially [...] Read more.
Performance adaptation is an effective way to improve the accuracy of gas turbine performance models. Although current performance adaptation methods, such as those using genetic algorithms or evolutionary computation to modify component characteristic maps, are useful for finding good solutions, they are essentially searching methods and suffer from long computation time. This paper presents a novel approach that can achieve good performance adaptation with low time complexity and without using any searching method. In this method, the actual component performance parameters are first estimated using engine measurements at different operating conditions. For each operating condition, some scaling factors are introduced and calculated to indicate the difference between the actual and predicted component performance parameters. Afterward, an interpolating algorithm is adopted to synthesize the scaling factors for modifying all major component maps. The adapted component maps are then able to make the engine model match all the gas path measurements and achieve the required accuracy of the engine performance model. The proposed approach has been tested with a model high-bypass turbofan engine using simulated data. The results show that the proposed performance adaptation approach can effectively improve the model’s accuracy. Specifically, the prediction errors can be reduced from about 9% to about 0.6%. In addition, this approach has much less computational complexity compared to other optimization-based counterparts. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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16 pages, 3992 KiB  
Article
Investigation into Detection Efficiency Deviations in Aviation Soot and Calibration Particles Based on Condensation Particle Counting
by Liang Chen, Quan Zhou, Guangze Li, Liuyong Chang, Longfei Chen and Yuanhao Li
Symmetry 2024, 16(2), 244; https://doi.org/10.3390/sym16020244 - 16 Feb 2024
Viewed by 1074
Abstract
Aviation soot constitutes a significant threat to human well-being, underscoring the critical importance of accurate measurements. The condensation particle counter (CPC) is the primary instrument for quantifying aviation soot, with detection efficiency being a crucial parameter. The properties of small particles and the [...] Read more.
Aviation soot constitutes a significant threat to human well-being, underscoring the critical importance of accurate measurements. The condensation particle counter (CPC) is the primary instrument for quantifying aviation soot, with detection efficiency being a crucial parameter. The properties of small particles and the symmetry of their growth pathways are closely related to the detection efficiency of the CPC. In laboratory environments, sodium chloride is conventionally utilized to calibrate the CPC’s detection efficiency. However, aviation soot exhibits distinctive morphological characteristics compared to the calibration particles, leading to detection efficiencies obtained from calibration particles that may not be applicable to aviation soot. To address this issue, a quantitative study was performed to explore the detection efficiency deviations between aviation soot and calibration particles. The experiment initially utilized a differential mobility analyzer to size select the two types of polydisperse particles into monodisperse particles. Subsequently, measurements of the separated particles were performed using the TSI Corporation’s aerosol electrometer and a rigorously validated CPC (BH-CPC). These allowed for determining the detection efficiency deviation in the BH-CPC for the two types of particles at different particle sizes. Furthermore, the influence of the operating temperature of the BH-CPC on this detection efficiency deviation was investigated. The experimental results indicate a significant detection efficiency deviation between aviation soot and sodium chloride. In the range of 10–40 nm, the absolute detection efficiency deviation can reach a maximum of 0.15, and the relative deviation can reach a maximum of 0.75. And this detection efficiency deviation can be reduced by establishing a relevant relationship between the detection efficiency of the operating temperature and the calibration temperature. Compared to the saturated segment calibration temperature of 50 °C, the aviation soot detection efficiency is closer to the sodium chloride detection efficiency at the calibration temperature of 50 °C when the saturated segment operates at a temperature of 45 °C. These studies provide crucial theoretical guidance for enhancing the precision of aviation soot emission detection and establish a foundation for future research in monitoring and controlling soot emissions within the aviation sector. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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28 pages, 11355 KiB  
Article
Nonlinear Dynamic Modeling and Analysis for a Spur Gear System with Dynamic Meshing Parameters and Sliding Friction
by Hao Liu, Dayi Zhang, Kaicheng Liu, Jianjun Wang, Yu Liu and Yifu Long
Symmetry 2023, 15(8), 1530; https://doi.org/10.3390/sym15081530 - 2 Aug 2023
Viewed by 1622
Abstract
The performance of gear systems is closely related to the meshing parameters and sliding friction. However, the time-varying characteristics of meshing parameters caused by transverse vibration are usually not regarded and the sliding friction has always been ignored in previous studies. Therefore, the [...] Read more.
The performance of gear systems is closely related to the meshing parameters and sliding friction. However, the time-varying characteristics of meshing parameters caused by transverse vibration are usually not regarded and the sliding friction has always been ignored in previous studies. Therefore, the influence of the transverse vibration on meshing parameters and sliding friction have not been considered. In view of this, a nonlinear dynamic model for a spur gear system is proposed. The dynamic meshing parameters (pressure angle, backlash, etc.) and the effects of the variations of these parameters on the dynamic mesh force (DMF) and sliding friction are emphasized. The differential equations of motion are derived by the Lagrange method and solved by the Runge–Kutta method. Then, the input speed and friction coefficient are used as control parameters to compare the dynamic responses of the new and previous models. The results show that the meshing parameters and sliding friction are affected by transverse vibration, leading to distinctive nonlinear dynamic responses. This paper can provide a basis for further research and give a better understanding of system vibration control. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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18 pages, 6563 KiB  
Article
Stiffness Characteristics and Analytical Model of a Flange Joint with a Spigot
by Hao Liu, Jianjun Wang, Yu Liu, Zhi Wang and Yifu Long
Symmetry 2023, 15(6), 1221; https://doi.org/10.3390/sym15061221 - 7 Jun 2023
Viewed by 2260
Abstract
Flange joints with spigots are widely used in aero-engines. The spigot will restrict the shear slipping between flanges, which, in turn, affects the stiffness characteristics of the joint. The current model and research on flange joints without spigots may not be suitable for [...] Read more.
Flange joints with spigots are widely used in aero-engines. The spigot will restrict the shear slipping between flanges, which, in turn, affects the stiffness characteristics of the joint. The current model and research on flange joints without spigots may not be suitable for the dynamic characteristics of aero-engines. Moreover, the complexity of contact pairs limits the application of the flange joint finite element (FE) model in aero-engine dynamics analysis. Therefore, a simplified analytical model of a flange joint with a spigot is proposed in this paper. First, the stiffness characteristic of the flange joint with a spigot is studied using the FE method. Second, a corresponding experiment is executed to verify the result of the FE analysis. Furthermore, based on the former FE and experimental analysis, one section of a flange joint is simulated by the Jenkins friction model and a spring. Then, a simplified analytical model of the entire flange joint is built according to the different statuses of each section. Finally, a simulation analysis of the stiffness characteristic is performed. The result shows that the simplified analytical model can be utilized to describe the bending stiffness characteristic of the flange joint with a spigot. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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22 pages, 9784 KiB  
Article
A Multi-Cavity Iterative Modeling Method for the Exhaust Systems of Altitude Ground Test Facilities
by Keqiang Miao, Xi Wang, Meiyin Zhu, Song Zhang, Zhihong Dan, Jiashuai Liu, Shubo Yang, Xitong Pei, Xin Wang and Louyue Zhang
Symmetry 2022, 14(7), 1399; https://doi.org/10.3390/sym14071399 - 7 Jul 2022
Cited by 4 | Viewed by 1743
Abstract
To solve the modeling problem of altitude ground test facility (AGTF) exhaust systems, which is caused by nonlinearity along the gas path and the difficulty of ejection factor calculation, a multi-cavity iterative modeling method is presented. The components of exhaust systems, such as [...] Read more.
To solve the modeling problem of altitude ground test facility (AGTF) exhaust systems, which is caused by nonlinearity along the gas path and the difficulty of ejection factor calculation, a multi-cavity iterative modeling method is presented. The components of exhaust systems, such as the exhaust diffuser and cooler, are built with a series of volumes. It overcomes the disadvantage that traditional lumped-parameter models have, whereby they cannot calculate the dynamic parameters along the gas path. The exhaust system model is built with an iterative method based on multi-cavity components, and simulations are carried out under experimental conditions. The simulation results show that the maximum error of pressure is 2 kPa in the steady state and less than 6 kPa in the transient process compared with experimental data. Closed-loop simulations are also carried out to further verify the accuracy and effectiveness of the multi-cavity iterative exhaust system modeling method. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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17 pages, 4578 KiB  
Article
Generic Modeling Method of Quasi-One-Dimensional Flow for Aeropropulsion System Test Facility
by Jiashuai Liu, Xi Wang, Xitong Pei, Meiyin Zhu, Louyue Zhang, Shubo Yang and Song Zhang
Symmetry 2022, 14(6), 1161; https://doi.org/10.3390/sym14061161 - 5 Jun 2022
Cited by 5 | Viewed by 1968
Abstract
To support the advanced controller design and verification of the Aeropropulsion System Test Facility (ASTF), it is necessary to establish a mathematical model of ASTF with high precision and replace the current lumped parameter model. Therefore, a quasi-one-dimensional flow model of ASTF is [...] Read more.
To support the advanced controller design and verification of the Aeropropulsion System Test Facility (ASTF), it is necessary to establish a mathematical model of ASTF with high precision and replace the current lumped parameter model. Therefore, a quasi-one-dimensional flow model of ASTF is established considering friction, localized losses, heat transfer, etc. Moreover, a generic modeling method is proposed for quasi-one-dimensional flow. With this method, all component models of ASTF are composed of staggered central control volume (CCV) and boundary control volume (BCV) and connected through virtual control volume. Thus, the properties of quasi-one-dimensional flow, such as spatial effect and time delay, can be easily addressed during the modeling process. The simulation results show that the quasi-one-dimensional flow model has higher accuracy than the lumped parameter model. Comparing the simulation results of the quasi-one-dimensional flow model with the test data, the relative errors of flow and pressure are less than 2.2% and 1.4%, respectively, further verifying the correctness of the proposed modeling method. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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22 pages, 8466 KiB  
Article
Investigation on the Formation and Evolution Mechanism of Flow-Resistance-Increasing Vortex of Aero-Engine Labyrinth Based on Entropy Generation Analysis
by Xiaojing Liu, Shuiting Ding, Longtao Shao, Shuai Zhao, Tian Qiu, Yu Zhou, Xiaozhe Zhang and Guo Li
Symmetry 2022, 14(5), 881; https://doi.org/10.3390/sym14050881 - 25 Apr 2022
Viewed by 2313
Abstract
Labyrinth seals are widely employed in the air system of aircraft engines since they reduce the leakages occurring between blades and shrouds, which affect the entropy generation significantly. Excessive leakage flow of the labyrinth may be reduced the efficiency and performance of the [...] Read more.
Labyrinth seals are widely employed in the air system of aircraft engines since they reduce the leakages occurring between blades and shrouds, which affect the entropy generation significantly. Excessive leakage flow of the labyrinth may be reduced the efficiency and performance of the engine. This paper proposes the concept of flow-resistance-increasing vortex (FRIV) on the top of the labyrinth that is based on the flow entropy generation mechanism of the stepped labyrinth and the main flow characteristics that lead to entropy generation. A three-dimensional simulation model of the labyrinth structure was established, and the model was compared and verified with the experimental data of the reference. The relative dissipation strength and vorticity distribution of the FRIV were theoretically analyzed. It was confirmed that the dissipative intensity distribution was the same as the vorticity distribution, and the correlation coefficient was larger in the labyrinth tip region. Therefore, a parametric study was conducted on design parameters related to the FRIV, including the teeth inclined angle, tooth crest width, step inclined angle, and other parameters. The results are beneficial for the construction of a stronger FRIV to reduce the leakage. This research is of great significance for the improvement of engine efficiency and for the reduction of fuel consumption in the future. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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20 pages, 6137 KiB  
Article
An Experimental Investigation into the Thermal Characteristics of Bump Foil Journal Bearings
by Yu Zhou, Longtao Shao, Shuai Zhao, Kun Zhu, Shuiting Ding, Farong Du and Zheng Xu
Symmetry 2022, 14(5), 878; https://doi.org/10.3390/sym14050878 - 25 Apr 2022
Cited by 5 | Viewed by 2231
Abstract
Bump foil journal bearings (BFJBs) are widely used in the superchargers of aviation piston engines (APEs). This paper proposes a method to evaluate the operating state of superchargers by monitoring the bearing temperature. A numerical model with a repeating symmetrical structure in the [...] Read more.
Bump foil journal bearings (BFJBs) are widely used in the superchargers of aviation piston engines (APEs). This paper proposes a method to evaluate the operating state of superchargers by monitoring the bearing temperature. A numerical model with a repeating symmetrical structure in the axial direction is established based on a certain type of supercharger, which solves the temperature field of BFJBs with the non-isothermal Reynolds equation and energy equation. It can be used to analyze the effect of thermal expansion on lift-off speed and stop-contact speed. A new test rig and six various BFJBs were designed to check the temperature characteristics of the BFJBs with variable load and speed. By comparing the numerical results with the experimental results, it was shown that the air film temperature increased almost linearly with the increase in bearing load and speed. However, the temperature increase caused by the rotation speed was significantly greater than the load. The structural parameters of the BFJB affected the bearing support stiffness, which had a nonlinear effect on the lift-off speed and air film temperature. Therefore, the proposed method to evaluate the state of superchargers with BFJBs was effective. These thermal characteristics can be used to guide BFJB design and predict the life cycle of BFJBs. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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18 pages, 10260 KiB  
Article
MoHydroLib: An HMU Library for Gas Turbine Control System with Modelica
by Yifu Long, Shubo Yang, Xi Wang, Zhen Jiang, Jiashuai Liu, Wenshuai Zhao, Meiyin Zhu, Huairong Chen, Keqiang Miao and Yi Zhang
Symmetry 2022, 14(5), 851; https://doi.org/10.3390/sym14050851 - 20 Apr 2022
Cited by 1 | Viewed by 2124
Abstract
Modelica is an open-source, object-oriented equation-based modeling language. It is suitable for describing sophisticated dynamic systems (symmetry/asymmetry) as it uses mathematical acausal equations to express physical characteristics. The hydraulic mechanical units (HMU) of gas turbine engine control systems couple the contents of mechanical, [...] Read more.
Modelica is an open-source, object-oriented equation-based modeling language. It is suitable for describing sophisticated dynamic systems (symmetry/asymmetry) as it uses mathematical acausal equations to express physical characteristics. The hydraulic mechanical units (HMU) of gas turbine engine control systems couple the contents of mechanical, hydraulic, symmetry, and other multidisciplinary fields. This paper focuses on the Modelica description method of those HMU models. The content of this work is threefold: firstly, the division form of basic elements in HMU is defined, and the method for describing these element models with Modelica is proposed; secondly, the organization of the element models is defined by using the inheritance characteristics of Modelica, and a lightweight (small code scale) component model is designed; and finally, the causal/acausal connections are designed according to bond graph theory, and the elements and components are integrated into a prototype modeling library. In this paper, the modeling library is verified by comparing simulation results of five typical HMU subsystem models with commercial modeling and simulation software. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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16 pages, 5122 KiB  
Article
Transient Controller Design Based on Reinforcement Learning for a Turbofan Engine with Actuator Dynamics
by Keqiang Miao, Xi Wang, Meiyin Zhu, Shubo Yang, Xitong Pei and Zhen Jiang
Symmetry 2022, 14(4), 684; https://doi.org/10.3390/sym14040684 - 25 Mar 2022
Cited by 7 | Viewed by 2188
Abstract
To solve the problem of transient control design with uncertainties and degradation in the life cycle, a design method for a turbofan engine’s transient controller based on reinforcement learning is proposed. The method adopts an actor–critic framework and deep deterministic policy gradient (DDPG) [...] Read more.
To solve the problem of transient control design with uncertainties and degradation in the life cycle, a design method for a turbofan engine’s transient controller based on reinforcement learning is proposed. The method adopts an actor–critic framework and deep deterministic policy gradient (DDPG) algorithm with the ability to train an agent with continuous action policy for the continuous and violent turbofan engine state change. Combined with a symmetrical acceleration and deceleration transient control plan, a reward function with the aim of servo tracking is proposed. Simulations under different conditions were carried out with a controller designed via the proposed method. The simulation results show that during the acceleration process of the engine from idle to an intermediate state, the controlled variables have no overshoot, and the settling time does not exceed 3.8 s. During the deceleration process of the engine from an intermediate state to idle, the corrected speed of high-pressure rotor has no overshoot, the corrected-speed overshoot of the low-pressure rotor does not exceed 1.5%, and the settling time does not exceed 3.3 s. A system with the designed transient controller can maintain the performance when uncertainties and degradation are considered. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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25 pages, 17378 KiB  
Article
Quasi-Analytical Solution of Optimum and Maximum Depth of Transverse V-Groove for Drag Reduction at Different Reynolds Numbers
by Zhiping Li, Long He and Yixuan Zheng
Symmetry 2022, 14(2), 342; https://doi.org/10.3390/sym14020342 - 8 Feb 2022
Cited by 7 | Viewed by 1921
Abstract
Reducing the skin-friction drag of a vehicle is an important way to reduce carbon emissions. Previous studies have investigated the drag reduction mechanisms of transverse grooves. However, it is more practical to investigate which groove geometry is optimal at different inflow conditions for [...] Read more.
Reducing the skin-friction drag of a vehicle is an important way to reduce carbon emissions. Previous studies have investigated the drag reduction mechanisms of transverse grooves. However, it is more practical to investigate which groove geometry is optimal at different inflow conditions for engineering. The purpose of this paper is to establish the physical model describing the relationship between the dimensionless depth (H+=Huτ/υ) of the transverse groove, the dimensionless inflow velocity (U∞+=U∞/uτ), and the drag reduction rate (η) to quasi-analytically solve the optimal and maximum transverse groove depth according to the Reynolds numbers. Firstly, we use the LES with the dynamic subgrid model to investigate the drag reduction characteristics of transverse V-grooves with different depths (h = 0.05~0.9 mm) at different Reynolds numbers (1.09×104~5.44×105) and find that H+ and U∞+ affect the magnitude of slip velocity (Us+), thus driving the variation of the viscous drag reduction rate (ην) and the increased rate of pressure drag (ηp). Moreover, the relationship between Us+, ην, and ηp is established based on the slip theory and the law of pressure distribution. Finally, the quasi-analytical solutions for the optimal and maximum depths are solved by adjusting Us+ to balance the cost (ηp) and benefit (ην). This solution is in good agreement with the present numerical simulations and previous experimental results. Full article
(This article belongs to the Special Issue Carbon Neutrality and Symmetry in Power Engineering and Engineering Thermophysics)
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