Stirling engine is a heat engine which is enclosed a fixed quantity of permanently gaseous fluid as the working fluid. The free-piston Stirling engine is noted for its high efficiency, quiet operation, long life without maintenance in ten years and the ease with which it can use almost any heat source. Stirling cycle analysis method has been successfully applied to improve the free-piston Stirling engine design by its step-by-step development on order. This study presents the development and application of Stirling cycle analysis method. Discussions about use of multi-dimension CFD software simulating free piston Stirling engine when there’s not any available experimental data for its design will provide. Since it needs less computing resource and time to get 1D simulation results with some accuracy, the application of multi-dimension CFD could be very helpful to improve accuracy of 1D result with the details of the different simplified model parameters used in 1D model. The research demonstrates that with the combination of high order Stirling cycle analysis method, the design of the free-piston Stirling engine with the aid of numerical method could be much more effectively and accurately.
Stop valves are commonly used as fluid flow control equipments in many engineering applications. A numerical study of a three-dimensional, complex geometry, stop-check valve was performed for model validation and improved understanding of valve flow features. This paper has provided a numerical investigation of the fluid flow inside a stop valve, including the modeling and the simulation of the stop valves. According to the simulation result of original valve structure, two cone valve block shape with different gradient are presented to bring some optimization to the stop-valve. CFD simulations were conducted for different structure of the valve to verify the performance of the valve after redesign the internal flow structure. The simulation results show that the pressure drop vortex strength, maximum velocity and velocity nonuniformity of valve outlet had been reduced obviously. Furthermore, the results of the three-dimensional optimization analysis of valve shape can be used in the design of low noise and high efficiency valve for industry.
The Holtrop method, which provides a prediction of the components of surface ships total resistance, is widely used at ships initial design stage for estimating the resistance. In this paper a neural network model which performs the same role as the Holtrop method is presented to predict the residual resistance. A multilayer perceptron has been trained with the data generated by the Holtrop method to learn the relationship between the input (length-displacement ratio, prismatic coefficient, breadth-draft ratio and Froude number) and the target variable (the residual resistance coefficient). The results of this model have been compared against those provided by the Holtrop method and it is found that the quality of the prediction is improved over the entire range of data. The neural network provides an accurate estimation of the residual resistance with the Froude number and the hull geometry coefficients as variables.
The heat transfer and the fluid dynamics characteristics of subsonic gas flows through micro-channels are examined using numerical method. Detailed analysis on the Stirling MEMS device has been examined for the feasibility of the performance. The 1-D Stirling engine design code was utilized to provide basic information to meet the design parameters and criteria. Furthermore a 2-D CFD code has been used to perform a detailed analysis. The simulation results show that the numerical method used here could be used for the prediction of MEMS performance before experimental test and manufacture process start.
Based on CFD technology, flow around a 2-dimentional hydrofoil of highly skewed propeller and NACA series hydrofoils are simulated using 2D incompressible Navier-Stokes equation with Realizable k- turbulence model. In the numerical simulation, the vapor volume fraction is calculated for different cavitation numbers and angles of attack by adding the mixture model. The hydrofoil’s performance and the relationship with hydrofoil parameter are qualitatively analyzed. Special focus is given to the influence of the cavitation numbers and angle of attack on cavitation characteristics.
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