Effect of the Modification of the Start-Up Sequence on the Thermal Stresses for a Microgas Turbine

Microgas turbines (MGT) are an alternative for small-scale energy production; however, their small size becomes a drawback since it enhances the heat transfer among their components. Moreover, heat transfer drives to temperature gradients which become higher during transient cycles like start-up. The influence of different start-up curves on temperature and thermal stresses of a microgas turbine was investigated. Stationary and rotational blades of the turbine were numerically simulated using CFD and FEM commercial codes. Conjugated heat transfer cases were solved for obtaining heat transfer from fluid toward the blades. Changes of temperature gradients within the blades during the start-ups were calculated under transient state with boundary conditions according to each curve to assess accurate thermal stresses calculations. Results showed that the modification of the start-up curves had an impact on the thermal stresses levels and on the time when highest stresses appeared on each component. Furthermore, zones highly stressed were located near the constraints of blades where thermal strains are restricted. It was also found that the curve that had a warming period at the beginning of the start-up allowed reducing the peaks of stresses making it more feasible and safer for the turbine start-up operation

Zmanjšanje mase in napetosti v gumijastem nosilcu motorja pod vplivom mehanskih vibracij

A rubber engine mount (EM) is a mechanical coupling between the engine and the chassis, and its main function is to diminish, in the chassis, the amplitude of vibrations caused for the engine operation. Such vibrations cause discomfort for vehicle passengers and reduce the EM lifetime. To increase the comfort of vehicle passengers and the lifetime of the EM, this paper presents an EM optimization by means of reducing three main criteria: the EM mass, the displacements transmitted to the chassis, and the mechanical stress in the EM rubber core. For carrying out the EM optimization, the optimum global determination by linking and interchanging kindred evaluators (GODLIKE), assisted by artificial neural networks (ANN) and finite element method (FEM), was used. Because of the optimization process, a reduction greater than 10 % was achieved in the three criteria in comparison with a baseline design. The frequency responses were compared and showed that although the optimization was carried out for the range of 5 Hz to 30 Hz the trend of reduced responses continues beyond this range. These results increased the comfort of vehicle passengers and the lifetime of the EMin addition, the reduction of mass diminishes its production costs

Aerodynamic Study Of The Rear Spoiler Profile Of A Pick-Up Vehicle

Aerodynamic drag in pick-up type vehicles is one of the main issues concerning their high fuel consumption. External devices attached to their body frame, such as spoilers, have been developed to reduce the drag. In this paper, the effect of the profile shape of a rear spoiler on aerodynamics of a pick-up vehicle was numerically investigated. The NACA 6409, NACA 0015 and NACA 4415 profiles were analyzed and compared with a case where any device was used. Results showed that flow and velocity of air were influenced by the addition and the shape of the spoilers. Low-pressure zone behind the vehicle was also affected due to modification of the boundary layer detachment. Analysis of static pressure on the rear surface showed that it was influenced by using the spoilers. On the other hand, drag and lift coefficients were calculated and evaluated for each case of study. Results allowed to identify the performance of the spoiler profiles on the drag of the vehicle

Reduction of Stresses and Mass of an Engine Rubber Mount Subject to Mechanical Vibrations

A rubber engine mount (EM) is a mechanical coupling between the engine and the chassis, and its main function is to diminish, in the chassis, the amplitude of vibrations caused for the engine operation. Such vibrations cause discomfort for vehicle passengers and reduce the EM lifetime. To increase the comfort of vehicle passengers and the lifetime of the EM, this paper presents an EM optimization by means of reducing three main criteria: the EM mass, the displacements transmitted to the chassis, and the mechanical stress in the EM rubber core. For carrying out the EM optimization, the optimum global determination by linking and interchanging kindred evaluators (GODLIKE), assisted by artificial neural networks (ANN) and finite element method (FEM), was used. Because of the optimization process, a reduction greater than 10 % was achieved in the three criteria in comparison with a baseline design. The frequency responses were compared and showed that although the optimization was carried out for the range of 5 Hz to 30 Hz the trend of reduced responses continues beyond this range. These results increased the comfort of vehicle passengers and the lifetime of the EM; in addition, the reduction of mass diminishes its production costs

Effect of Thermal Barrier Coating on the Thermal Stress of Gas Microturbine Blades and Nozzles

Thermal barrier coatings play a key role in the operational life of microturbines because they reduce thermal stress in the turbine components. In this work, numerical computations were carried out to assess new materials developed to be used as a thermal barrier coating for gas turbine blades. The performance of the microturbine components protection is also evaluated. The new materials were 8YSZ, Mg2SiO4, Y3Ce7Ta2O23.5, and Yb3Ce7Ta2O23.5. For testing the materials, a 3D gas microturbine model is developed, in which the fluid-structure interaction is solved using CFD and FEM. Temperature fields and stress magnitudes are calculated on the nozzle and blade, and then these are compared with a case in which no thermal barrier is used. Based on these results, the non-uniform temperature distributions are used to compute the stress levels in nozzles and blades. Higher temperature gradients are observed on the nozzle; the maximum temperature magnitudes are observed in the blades. However, it is found that Mg2SiO4 and Y3Ce7Ta2O23.5 provided better thermal insulation for the turbine components compared with the other evaluated materials. Mg2SiO4 and Y3Ce7Ta2O23.5 presented the best performance regarding stress and thermal insulation for the microturbine components

Método Taguchi para la optimización de parámetros en la simulación numérica del proceso de inyección de plástico

El trabajo plantea el uso de Método Taguchi para la optimización de parámetros en la simulación numérica del proceso de inyección de plástico para reducir el desplazamiento total en el producto. Se identificaron las variables de temperatura de derretimiento, tiempo de enfriamiento, tiempo de llenado, y tiempo de mantención. Se plantea la utilización de diseño de experimentos de Taguchi de tres niveles y cinco factores, que suman un total de 27 iteraciones del experimento. El análisis de señal a ruido determinó que los dos parámetros más influyentes en la disminución de desplazamiento fueron temperatura de derretimiento y tiempo de mantención de presión. Tras el análisis de la varianza y la interpretación de gráficas de señal se plantearon dos experimentos cuyos valores demostraron una mejora de 27 % (5.0349 mm) y 31.43% (4.7485 mm), respectivamente, en comparación a los valores de control (6.9252 mm). Mediante el uso de las herramientas permite. Mediante el uso de Taguchi y SolidWorks plastic se logró disminuir la variación de la deformación y la detección de las principales variables que afectan en el proceso de llenado de la pieza aplicando el método propuesto