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Domain discretisation in three dimensions using hexahedral elements for inlet stator, outlet stator, and rotor channels
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Wave rotors are unsteady flow machines that exchange energy through pressure waves. This has the potential for enhancing efficiency over a wide spectrum of applications, ranging from gas turbine topping cycles to pressure-gain combustors. This paper introduces an aerodynamic shape optimisation of a power generating non-axial microwave rotor turbine...
Citations
... Researchers such as Tüchler used a hybrid algorithm of PSO and genetic algorithm to optimize the rotor shape profile, wall thickness, and number of channels of a wave rotor. This confirmed that the numerical optimization method has more advantages compared to traditional methods (Tüchler and Copeland, 2021). Guo and other scholars analyzed the optimization model of surface roughness and cutting force using multi-objective PSO to achieve the accuracy and speed of nickel based hightemperature alloy processing. ...
The five axis linkage Computer Numerical Control machine tool for integral impeller can achieve blade machining through side milling, which is of great significance for improving the machining accuracy, production efficiency, and long-term stability of integral impeller blades. This study is based on non-uniform rational B-spline curves and aims to reduce the surface over cutting or under cutting of integral turbine blades. The path planning of non deployable ruled surfaces was analyzed in depth through side milling, and the path planning model of the side milling cutter axis was solved through a fusion algorithm of simulated annealing algorithm and particle swarm optimization algorithm, in order to find the optimal path through iterative process. As the number of iterations increased, the error values of particle swarm optimization algorithm and simulated annealing particle swarm optimization fusion algorithm gradually decreased, with convergence times of about 7 and 6, respectively. The stable error value of the fusion algorithm was 0.253, which is 30.45% lower than that of the particle swarm optimization algorithm. The optimal number of iterations for solving the model using particle swarm optimization algorithm and fusion algorithm was the 7th, with range values of 0.0213 and 0.0165 mm, respectively. The tool axis trajectory surface optimized by the fusion algorithm was closer to the tool axis motion state compared to the initial tool axis trajectory surface. The range of the sum of mean squared deviations for single and global cutting was 0.0011–0.0198 and 0.046–0.0341, but the overall error value was relatively small. This study effectively reduces the envelope error of machining tools and improves machining accuracy, thereby solving the principle error of non expandable ruled surfaces in the motion trajectory of the blade axis of the integral turbine. This provides new research ideas for the intelligent development of Computer Numerical Control machining technology.
... Constant-volume combustion (CVC) systems that achieve pressure gain have the potential to significantly reduce fuel consumption in a gas turbine and improve the overall thermal efficiency [1][2][3][4]. A wave rotor can combine unsteady flow with steady flow components, making it suitable for use as a dynamic pressure exchanger integrated into gas turbines [5][6][7][8][9][10]. The wave rotor combustor (WRC) incorporates pressure gain and combustion, and due to its periodic cycle and the utilization of multiple combustion channels, it is better suited for turbomachines than other pressure gain combustors [11][12][13][14][15]. Therefore, the WRC holds significant potential for application in advanced gas turbine systems. ...
The pressure gain combustion in wave rotors has the potential to significantly enhance the performance of gas turbine engines. Wave rotor design focuses on understanding the complex behavior of rotating channels, which is challenging due to high rotational speeds. To investigate the influence of different working conditions on the unsteady process within the wave rotor combustor, a simplified 24-channel model was established to study both the unsteady flow and the wave dynamics. The calculations indicate that, for the current port position adopted and a rotor speed of 4000 rpm, backflow occurs at the inlet port for various inlet pressures. By analyzing the working sequence of the wave rotor combustor, it is found that the inlet port does not close in time when the pre-compression wave returns. This delay results in reflected expansion waves or compression waves moving within the channel, which affect a portion of the pressure gain, leading to a damped sinusoidal trend in the pressure profiles within the channel. The optimal pre-pressurization effect can be achieved at a rotor speed of 2000 rpm for the test conditions considered, and the total pressure gain achieved was 6.3%. By adding hot-jet ignition, it is found that the shock wave and flame interact at least five times in the current simulation. The shock–flame interaction can greatly accelerate the process of chemical reactions. After the fourth interaction, the shock wave achieved local coupling with the flame, forming a local high-pressure area of 4 bar, verifying the effectiveness of the wave rotor as a constant-volume supercharging device.
... Gas-particle flows in a microscale shock tube and collection efficiency in the jet impingement on a permeable surface 3 Ilyoup Sohn (손일엽), 4 Byoung Jae Kim (김병재), 2,a) and R. S. Myong (명노신) 5,a) AFFILIATIONS 1 ...
We investigate the flow physics of non-equilibrium gases in interaction with solid particles in a microscale shock tube and the collection efficiency in the jet impingement on a permeable surface. One interesting application of flows in shock tubes at low pressures or micro-shock tubes is needle-free injection technology where drug particles are delivered by shock waves. To investigate such problems, a new two-fluid model system coupled with second-order Boltzmann–Curtiss-based constitutive relationships for modeling a non-equilibrium gas was developed. We were specifically interested in how rarefaction affects the complex wave patterns observed in dusty gas flows and the role of bulk viscosity in diatomic and polyatomic gases exposed to moving shocks. Simulation results demonstrated how significantly the bulk viscosity can affect the topology of the solution in the Sod shock tube problem. Counter-intuitive flow features were noted, resulting from bulk viscosity effects and the incapability of the first-order theory, even when Stokes' hypothesis was abandoned (i.e., the Navier–Fourier model). After detailed analyses in one-, two-, and three-dimensional space for simplified flow problems, a case was designed to represent a needle-free injection device. In addition, a new concept of “collection efficiency” was introduced that quantifies the efficiency of drug delivery in the two-phase jet impingement on the skin. We also derived a new “vorticity transport equation” that takes the bulk viscosity and multiphase effects into account. Based on the new equation, the time evolution of vorticity growth rates was analyzed for all the contributing terms in the equation.
... Xu et al. [20] also optimized the impeller of a high-speed magnetic drive pump using the optimal Latin hypercube sampling method combined with the response surface methodology surrogate model. Tüchler et al. [21] introduced an aerodynamic shape optimization method for a micro-wave rotor turbine using the CFD model and hybrid algorithm. Furthermore, references [22,23] also optimized the compressor using the surrogate model. ...
The centrifugal fan is widely used in converting mechanical energy to aerodynamic energy. To improve the pressure of the multi-blade centrifugal fan used in an air purifier, an optimization process was proposed based on extreme learning machine (ELM) combined with particle swarm optimization (PSO). The blade definition position parameter and blade definition radian parameter were designed using the full-factor simulation experimental method. The steady numerical simulation of each experimental point was carried out using ANSYS CFX software. The total pressure of the multi-blade centrifugal fan was selected as the optimization response. The optimized ELM combined with the PSO algorithm considering the total pressure response value and the two multi-blade centrifugal fan parameters were built. The PSO algorithm was used to optimize the approximation blade profile to obtain the optimum parameters of the multi-blade centrifugal fan. The total pressure was improved from 140.6 Pa to 151 Pa through simulation experiment design and improved surrogate optimization. The method used in the article is meant for improving multi-blade centrifugal total pressure. The coupling optimization of impellers, volutes, and air intakes should be comprehensively considered to further improve the performance of centrifugal fans.
... Computational fluid dynamics (CFD) simulation methods have been developed to simulate the two-dimensional flow filed [31] and to assess the shaft work [32] of wave rotors. Design methods [33] and optimization methods [34] have also been developed for the wave rotors in recent years. ...
Supercritical carbon dioxide Brayton cycle is emerging as a solution to effective and clean power resources, and the pressure exchanger is a critical part of such cycle. While turbomachinery is the conventional technology of such pressure exchangers, it sustains high shaft work and suffers from especially high rotational speed, which is a key challenge. This work proposed a wave rotor for supercritical carbon dioxide pressure exchanger as an alternative technology of the turbomachinery. Numerical simulation results demonstrate that a wave rotor compresses and expands supercritical carbon dioxide with unsteady pressure waves, so it does not take a high rim speed to do the compression or expansion work like turbomachinery, and a low rotational speed and a low shaft work are available then. According to the design results for a practical compression ratio at 1.93 and a massflow rate at 2.30 kg/s, the wave rotor reduces the rotational speed to 8 % and the shaft work to 4 % of equivalent turbomachines, and the wave rotor has comparable efficiency and size to equivalent turbomachines. This work provides the special advantage and suitability of the wave rotor as a pressure exchanger of the supercritical carbon dioxide Brayton cycle.
... Pearson [8] and General Electric (GE) company [9] designed and experimentally studied a wave rotor turbine in the 1980s, which indicates the potential of wave rotors to extract shaft power like a turbine. Jagannath et al. [10], Tüchler et al. [11][12][13][14], and Liu et al. [15] recently developed wave rotors with the cambered, or curved, channels. Tüchler et al. experimentally validated that their wave rotors succeeded in power extraction of the rotor [13]. ...
... In recent years, the work of Jagannath et al. [10] mentioned geometry models of staggered channels, but did not mention flow-field results of the staggered channels. The works of Tüchler et al. [14] and Liu et al. [15] on channel geometry optimization were on general geometries of cambered and staggered channels, but did not distinguish the effects of a cambered geometry from the effects of a staggered geometry. Therefore, the contribution of the staggered geometry to wave rotor optimization remains unclear. ...
A wave rotor optimizes the use of energy resources by enhancing thermodynamic cycles, and further optimization of wave rotor geometry is emerging as an attractive research area. Among the geometric features, the stagger angle of channels lacks sufficient study in spite of its important effects. To address this question, this work developed and applied the velocity triangle models to modify the basic geometry of wave rotors for different stagger angles, and investigated the flow fields with two-dimensional numerical methods. Results showed that: (1) different stagger angles worked out similar unsteady pressure wave systems and kept nearly constant compression and expansion ratios of the wave rotor; (2) increased stagger angle made the inlet and outlet flows turn toward the axial direction, which was beneficial to compact and light-weighted integration of the wave rotor to a gas turbine; (3) increased stagger angle made the wave rotor consume more shaft power, but even the maximum shaft power was small. This work revealed a critical mechanism how the velocity variation across an unsteady pressure wave produced rim work in a staggered channel, and made a recommendation to comprehensive optimization of wave rotor geometry for better integration in a gas turbine and acceptable shaft power consumption.
... For this purpose, they used Gaussian radial basis function in combination with an improved genetic algorithm (NSGA II) to optimize the parameterized shape of the turbine rotor system. Hybrid genetic algorithm investigations performed by Copeland et al. [15] sought to couple an evolutionary algorithm with a surrogate model in the application of aerodynamic shape optimization aiming at enhance micro-wave rotor turbine efficiency. In addition to wave rotors, a hybrid of genetic algorithm with the Nelder-Mead method have been used in the preliminary design of organic rankine cycle (ORC) axial turbine to improve the flow efficiency [16]. ...
The SCO2 turbine machines exchange energy through supercritical carbon dioxide. Their impeller has the features of high-temperature and −speed to enhance energy conversion efficiency, but the rotor needs to be cooled to be compatible with bearings and seals. The paper introduces a pivotal parameter optimization of a concentrating solar SCO2 turbine rotor and seeks to control the harmonic response amplitude while preserving the distance between the critical speed and the working speed. The optimization considers several parameters including bearing span, stiffness, effective mass and damping of the bearing hub, and gas film stiffness coefficients of the cooler. The optimization is accomplished using a multi-objective and −scale quantum harmonic oscillator algorithm (mMQHOA) that couples an information interaction algorithm and transfer matrix model. The application of information interaction accelerates the convergence speed of the objective functions. The verification results from the three-dimensional finite element (3D-FE) indicate that the non-dominant design reduces resonance amplitude of the disc by approximately 71.91%, while the critical frequency increases by about 34.33% in the direction away from the operating frequency, and imply a trade-off relationship between harmonic response amplitude and critical speed. It is further reveal that the increased gas film stiffness of cooler in the primary level interval (
... Numerical simulations can be used to derive the physical eld distribution of the complex unsteady ow in the rotor channels that cannot be reliably and thoroughly monitored via current experiments. The numerical simulation method is currently widely used in wave rotor technology, 13,37 and its accuracy and efficiency have been praised by academics and engineering technicians. In this research, the CFD commercial soware FLUENT was used to carry out the relevant numerical calculations. ...
Gas wave ejectors (GWEs) utilize pressure waves to efficiently transfer energy between gases, and they have broad applications in the chemical industry. In order to improve the performance of GWEs, the influence of bending angles on GWE performance was studied and experiments involving a GWE equipped with curved channels were carried out for the first time in this study. The research results show that when the exhaust angle difference (φ dout) is ≤-3.9° and the incident angle difference (φ din) is >5.0° or ≤-5.0°, the equipment performance decreases with an increase in the absolute values of the angle differences. The maximum efficiency of the backward-curved-channel device is 61.6% within the experimental range. The experimental efficiency of the curved-channel device and the static-pressure proportion of the total pressure of the medium-pressure gas are enhanced in comparison with a traditional straight-channel device, and the operating power consumption is relatively reduced. Due to the difference between the gas incident and exhaust angles, the manner in which the performance of the curved-channel device varies with the rotation speed is different depending on the working conditions.
... Additionally, WRCs do not require a detonation process to achieve a pressure gain if combustion is fast enough [67]. Recently, several works on the feasibility, design, and thermodynamic analysis of the combustion cycle of WRCs have been performed [68,69]. Design and experimental testing of a WRC achieved stable operations at near-atmospheric inlet conditions over a wide range of overall equivalence ratios [70]. ...
The effects of climate change and global warming are arising a new awareness on the impact of our daily life. Power generation for transportation and mobility as well as in industry is the main responsible for the greenhouse gas emissions. Indeed, currently, 80% of the energy is still produced by combustion of fossil fuels; thus, great efforts need to be spent to make combustion greener and safer than in the past. For this reason, a review of the most recent gas turbines combustion strategy with a focus on fuels, combustion techniques, and burners is presented here. A new generation of fuels for gas turbines are currently under investigation by the academic community, with a specific concern about production and storage. Among them, biofuels represent a trustworthy and valuable solution in the next decades during the transition to zero carbon fuels (e.g., hydrogen and ammonia). Promising combustion techniques explored in the past, and then abandoned due to their technological complexity, are now receiving renewed attention (e.g., MILD, PVC), thanks to their effectiveness in improving the efficiency and reducing emissions of standard gas turbine cycles. Finally, many advances are illustrated in terms of new burners, developed for both aviation and power generation. This overview points out promising solutions for the next generation combustion and opens the way to a fast transition toward zero emissions power generation.
