Grid Plate Flame Stabilizer for High Intensity Gas Turbine Combustion: The Influence of the Method of Fuel Injection on Mixing, Flame Development and NOx Emissions

Grid plate flame stabilizers for low NOx emissions have renewed interest in recent years due to their use in low NOx hydrogen gas turbine combustors. For non-premixed grid plate combustion, the difference in flame stabilizer design is in how the grid plate air flow is fueled. In the present work a simple four hole grid plate is investigated using CFD with three methods of fueling the air holes: radially inward fuel injection using 8 fuel nozzles per air hole (Grid Mix, GM 1 and Micromix); central fuel injection (FLOX method); and through a fuel annulus around each air hole (GM2). ANSYS FLUENT CFD predictions for GM2 are compared with axial gas composition traverses inside the combustor and with the mean combustor exit plane emissions. The three methods of fuel injection are also compared using isothermal CFD to determine which of the three methods offer the best mixing quality, which controls the relative NOx emissions. The predictions were for an equivalence ratio of 0.624 for the combustion stage and 0.5 for the isothermal study, using industrial propane. CFD modelling used RANS simulation with Realizable k-epsilon turbulence model, non-premixed combustion with the Steady Laminar Flamelet model. The temperature and mixing profiles obtained for GM2 were in reasonable agreement with the experiments and the other two fuel injection methods were then compared with GM2.

A new type of bionic grid plate—The compressive deformation and mechanical properties of the grid beetle elytron plate

To develop lightweight and biomimetic structural materials, in this paper, the compressive deformation and mechanical properties of the grid beetle elytron plate (GBEP) with the same core volume as the end-trabecular beetle elytron plate (EBEP) under compression were investigated for the first time. (1) The B-type deformation mode of trabeculae is clarified, which is a higher stage of independent deformation than the Φ-type deformation mode in the beetle elytron plate (BEP). Additionally, the four deformation modes of the BEP are divided into three stages in succession from easy to difficult: C-type, Φ-type and S (B)-type deformation. This paper verifies that the compressive strength and energy absorption capacity of the GBEP increase by 35% and 87%, respectively, relative to those of the grid plate (GP) with the same volume. (2) Although the number of trabeculae of the GBEP is significantly less than that of the EBEP, each trabecula in the GBEP has one more honeycomb wall constraint than each trabecula in the EBEP. The increase range of the compressive properties of the GBEP relative to the GP is greater than that of the EBEP relative to the honeycomb plate (HP). This confirms the prediction that the compressive properties can be effectively improved by appropriately increasing the constraints on the trabeculae. This paper deepens and enriches the knowledge regarding the biomimetic application system of BEPs, lays the foundation for GBEPs, whose preparation is convenient, and accelerates the applications of GBEPs.

Enhancing Flow Field Performance of a Small Circulating Water Channel Based on Porous Grid Plate

Low-cost and high-efficiency circulating water channels are widely used in the hydrodynamic tests of an underwater device. The current research mainly focuses on obtaining a better velocity uniformity of the test section by optimizing the curve function of the boundary in the contraction section. While, for small underwater device, their hydrodynamic characteristics are sensitive to turbulence. Thus, the circulating water channel, which can obtain the required turbulence characteristics, is urgently needed. A small circulating water channel, which can reduce the turbulence intensity based on a porous grid plate and can be used to test the hydrodynamic characteristics of a small underwater device, is designed. The relationships between porosities and resistance coefficients of a porous grid plate are established. The effects of the honeycomb (porosity and thickness); screen (porosity, number of layers, and spacing); and pumping flow rate on the turbulent characteristics of the test section are studied. The relationships between the parameters and the turbulent characteristics of the test section are established, and the methods to achieve the required flow characteristics of the test section are proposed. Experiments are carried out, and the validity of the obtained results is verified. In this work, the turbulence intensity of the fluid field in the test section can be restrained to 0.0491, which is enough to meet the turbulence requirements for the hydrodynamic test of a small underwater device. This work can provide references for the construction of a hydrodynamic test platform for small underwater devices.

Numerical simulation and experimental study of electrocoagulation grid flocculation tank

In recent years, electrocoagulation has been extensively studied on the removal of refractory pollutants. However, the application of electrocoagulation in actual flocculation tank is limited because of its high energy consumption, especially under the condition of large electrode plate spacing. In this study, the computational fluid dynamics (CFD) software – ANSYS Fluent had been used to simulate the flow state of grid flocculation tank, for the purposes of optimizing the design parameters. The simulation results showed that vortex velocity gradient was stronger, the grid plate spacing was smaller when the velocity was 0.13 m s−1, perforation size was 25 × 25 mm, porosity was 31.25%. And the optimal grid plate spacing was 250 mm. Moreover, in order to prove the reasonableness of simulation results, the humic acid wastewater was treated by electrocoagulation process in the specific device which was built based on simulation results. The results showed that the optimal condition of orthogonal test were as follows: the initial pH was 8, the concentration of sodium chloride was 5 mmol L−1, the voltage was 15 V; and the power time was 60 min. This study greatly narrowed the grid plate spacing, optimized design parameters under the circumstances of strong turbulent intensity and provided a theoretical basis for the combination of electrocoagulation and hydraulic flocculation.