To investigate the wall-approaching film formation (WAFF) mechanism of water injected during the compression process of single screw compressor, then to realize reasonable control of water injection parameters, a numerical simulation of water and steam two-phase flow inside the compression chamber during the compression process was carried out. The WAFF characteristics of water injected inside the compression chamber and the influence laws of the key parameters such as water injection angle (IA), injection velocity (IV), injection mass flow rate (IMFR), screw rotor rotational speed (SRRS) and injection hole spatial position (IHSP) on the WAFF characteristics were analyzed. The results show that the water injected into the chamber forms a water film by approaching the wall. With the increase of IA and IV, the effective water film average thickness (EWF-AT) and surface area (EWF-SA) show an increasing trend. In the process of IMFR growth, EWF-AT and EWF-SA exhibit maximum values. Considering the goal of minimizing the injection power consumption, the IA of 70 degrees, IV of 30 m.s(-1) and IMFR of 0.3 kg.s(-1) were determined as the optimal water injection parameters. Selecting the appropriate IMFR, SRRS and IHSP will effectively increase EWF-AT and EWF-SA, then to prevent leakage.
Carbon dioxide capture and storage is an important technological pathway to achieve climate change response goals based on ensuring energy security,and is an important strategic choice for achieving carbon reduction in the power as well as industrial sectors.However,high energy consumption and accompanying issues are key to the limit the development of carbon capture and storage at scale.In this paper,the load-cycling performance and exergy distribution of coal-fired power plants integrated with full flue gas carbon capture systems are investigated,and the variable working conditions performance of two turbine configurations of low carbon emission coal-fired units is compared.The results show that the energy consumption of the carbon capture system is 3.9 GJ·t-1 CO2 for full flue gas carbon capture,and the large irreversibility of the absorption and desorption processes leads to low efficiency of the absorber and stripper.After integrating the carbon capture system into the coal-fired power station,the efficiency of the configuration with the heat recovery turbine exhaust system is 1.5％higher than that with the medium-pressure cylinder exhaust,and the efficiency of the unit with the heat recovery turbine exhaust system.
Under the influence of secondary flow, the film cooling deviates from the flow direction on the turbine blade, which directly results in undesirable uneven film coverage. On the pressure side, the film appears divergent, while on the suction side, it is bunched. To solve this problem, a kind of subregional compound angle is proposed, in which the angle in the spanwise direction is different in different regions depending on the strength and direction of the secondary flow. Four rows of film holes with five kinds of subregional compound angles are provided on the pressure side, while two rows of film holes with different subregional compound angles are provided on the suction side. The Reynolds Average Navier-Stokes (RANS) method of the SST k-omega turbulence model is chosen to solve the above blade arrangement. The results show that a significant improvement can be achieved by the introducing subregional compound injection of the film coolant compared to the case of simple injection. In compound injection, the injectant maintains sufficient momentum to prevent the coolant from being swept away by the secondary flow. This was found to be largely the case for most holes on the pressure side, and some holes on the suction side. However, for holes near the downstream section of the suction surface of the blade, where the passage vortex is strongest, no value is found for the compound angle that could redirect the coolant along the blade profile without radial deviation. In some cases, excessive values of the compound angle led to jet liftoff rather than spreading the film along the surface.
Recently, artificial neural networks (ANNs) have been frequently embedded in computational fluid dynamics (CFD) solvers as surrogate tools for solving chemical reaction kinetics, thereby accelerating the computation of chemical reaction source terms. Compared with other chemical acceleration methods, such as mechanism reduction and tabulation, ANNs have the potential to simultaneously save computational cost and preserve mechanisms' high fidelity. However, conventional data-driven ANNs highly rely on the training data for solving combustion reaction kinetics, and non-physical prediction errors can hardly be avoided. This paper proposes a physics-informed neural network for solving combustion reaction kinetics (CRK-PINN), which regularizes the ANN through physical principles, including the laws of mass action, Arrhenius, enthalpy conservation, element conservation, and mole fraction conservation. In the absence of training data, CRK-PINN can independently solve chemical reaction kinetics, reconstruct the combustion process, and infer intermediate species and temperature. Under the supervision of training data and physical principles, CRK-PINN significantly suppresses the non-physical errors of data-driven ANNs and presents lower data dependence. This is demonstrated by the 0-D autoignition prediction and direct numerical simulation (DNS) of laminar and turbulent flames. Compared with the direct integration method, CRK-PINN results in an acceleration of 6.0 similar to 14.6 times for solving a 10- species 21-step H2-Air chemical mechanism. This further leads to a 2.3 similar to 4.9 times speedup for simulations of reacting flows with satisfactory accuracy based on the OpenFOAM toolbox. Novelty and significance statement We propose a novel Combustion Reaction Kinetics Physics-Informed Neural Network (CRK-PINN) for solving detailed combustion reaction kinetics with features of multiscale and high stiffness. Soft constraints of physical losses have been developed in PINNs to solve ordinary differential equations (ODEs). Data preprocessing methods such as logarithm and normalization are commonly used to alleviate the multiscale issue. However, these techniques have not been effectively integrated to properly address detailed combustion reaction kinetics. Our CRK-PINN incorporates logarithmic-normalized combustion reaction kinetics ODEs and several conservation equations as physical constraints into a neural network, highlighting both technical challenges and our novelty. By incorporating comprehensive physical constraints, CRK-PINN can independently solves detailed combustion reaction kinetics without relying on training data. Compared with data-driven ANNs, CRK-PINN offers a surrogate model with improved physical completeness, error reduction, and low data dependence. Compared with the direct integration method, CRK-PINN provides satisfactory accuracy and evident computational acceleration.
Two-phase flow in non-circular cross-section flow channels such as micro-heat sinks and micro-channel heat exchangers has received extensive attention due to its heat-enhancing properties. In this paper, under the boundary of constant heat flux, an experimental investigation of the heat transfer properties of gas–liquid two-phase flow in horizontal channels with cross-sections of 4 × 4 mm and 8 × 3 mm is carried out using air and water as working fluids. The effects of different inlet gas and liquid inlet Reynolds numbers on the wall temperature and Nusselt number are discussed. The results show that the effects of the liquid Reynolds number and the gas phase Reynolds number on the heat transfer coefficient of the square tube and the rectangular tube are different. Under the same gas–liquid Reynolds number, the Nusselt number of the gas–liquid two-phase flow in the square-section tube can be increased by 3.2 times compared with that in the single-phase flow, while the Nusselt number of the gas–liquid two-phase flow in the rectangular tubes can be increased by 1.87 times. The results of this paper provide a reference for the design of microchannel heat exchangers and the establishment of mathematical models for Taylor flow heat transfer in rectangular and square tubes.
