Integrated Lifing Analysis Tool for Gas Turbine Components

Comparative performance analysis of combined-cycle pulse detonation turbofan engines (PDTEs)

The purpose of this study is to analyze the large deflection problem of bimodular functionally graded truncated thin conical shells under the transverse mechanical load and non-uniform thermal load, in which two different boundary constraints of the truncated shell with two ends simply supported and fully fixed are considered. It is assumed that the temperature distribution along the thickness direction satisfies the Fourier law of heat transfer, and the material properties change exponentially along the thickness direction while different properties in tension and compression are considered. The geometric equation of the conical shell is established based on the equivalent method of curvature correction of von-Kármán deformation theory, and the analytical solution of the problem is obtained by Ritz method. Numerical simulation of bimodular functionally graded conical shells under the thermal and mechanical loads is carried out by Abaqus, and the numerical solution agrees with the theoretical solution. The results show that the introduction of bimodular functionally graded material will affect the maximum displacement and this effect has different rules under the mechanical load and thermal load. In addition, factors such as the cone apex angle and the truncated distance have a great influence on the maximum displacement and its location of the conical shell.

A physics-based model of residual stress in minimum quantity lubrication (MQL) machining is presented. The stresses resulting from thermal and mechanical loading in the MQL machining process are coupled into an incremental thermal-elastic-plastic model for predicting the final resultant residual stress in the machined workpiece. Comparative analysis is made between the stresses produced by the thermal load and mechanical load in the machining process. Results manifest that for the surface of the machined workpiece, the stress produced by thermal load is on par with the contact stress produced by mechanical load in the magnitude. With the increase of depth into the workpiece, the stress produced by mechanical load is dominant of the total stresses. The rationale demonstrates that thermal load is prone to generate the tensile residual stress at the surface of the machined workpiece, while the mechanical load is prone to generate the compressive residual stress at the surface of the machined workpiece. Finally, the residual stress prediction model is verified by orthogonal cutting of AISI 4130 alloy steel.

The present paper addresses the thermo piezo magneto elastic behavior of a functionally graded piezomagnetic cylinder under thermal, magnetic and mechanical loads. All mechanical, thermal and magnetic properties are graded in the radial direction. The cylinder is subjected to inner pressure, thermal and magnetic loads. Temperature distribution can be obtained using solution of the heat transfer equation with general boundary conditions. Employing the equilibrium relations for both mechanical and magnetic components presents two basic equations for derivation of unknown functions. After solution of the problem, the distribution of the mechanical and the magnetic components can be presented for different values of non homogenous index. The effect of non homogenous index on the mechanical and magnetic distribution presents best optimization for intelligent manufacturing and design of the materials. Used material in this paper can be considered as a sensor for determination of the physical components and as an actuator in the micro positioning. Uniform distribution of the mechanical or the magnetic components can be obtained for special value of non homogeneity. These uniform distributions have many advantageous conditions for designer and manufactures. Key words: piezomagnetic, non homogenous index, solution, root.

Subinterfacial cracks in bimaterial systems subjected to mechanical and thermal loading

The performance and emission from diesel engine using biodiesel from waste coconut oil (WCOO) with and without additives is accessed in this article. WCOO biodiesel is produced from coconuts which are not favorable to be consumed by humans due to degradation. B20, B40, B50, and B100 biodiesel blends of WCOO are prepared and performance and emission testing are done. B20 blend of biodiesel is added with 5%, 10%, and 15% of 1-hepatanol and the tests are repeated. Then, B20 is added with 5% of 1-hepatnol, n-butanol, and iso-butanol as additive and separate analysis for each additive in B20 is carried out in similar way. The injection pressure was kept constant at 225 bar throughout these experiments. Later, B20, B40, B50, and B100 blends of WCOO are used separately for engine performance and emission behavior at 175 injection pressure without adding any additive. Brake specific fuel consumption (BSFC) and brake thermal efficiency are the factors analyzed during engine performance analysis and CO, CO2, HC, and NO x exhaust are recorded during emission analysis. From the comparative study, the engine performance of diesel is seen to be better than any other combination of biofuels at both the pressures. Among blends without additive, B20 performed better than other blends, B20 with n-butanol performed better than B20 without additive, while B20 with iso-butanol did not show any significant advantage. At 175 bar injection pressure 7.5% extra BSFC and approximately 16% more emission is obtained than at 225 bar pressure.

The geometrically nonlinear response of a circular sandwich plate that consists of two face sheets and a compliant (“soft”) core with mechanical properties that may be either independent or dependent of temperature and subjected to both mechanical loads and thermal induced deformations, but remain elastic linear throughout the loading process, is presented. The mathematical formulation follows the principles of the high-order sandwich panel theory (HSAPT) and includes the vertical flexibility of the core in addition to the temperature dependency of the mechanical properties of the core material. The mathematical formulation outlines the set of governing partial differential equations as well the appropriate boundary conditions for a general sandwich layout. The particular case of an axisymmetric circular sandwich plate subjected to axisymmetric mechanical and thermal loads, and with axisymmetric boundary conditions is studied analytically and numerically. The numerical study includes an interaction of mechanical and thermal loads which is presented through results within the plate for various load levels of various structural quantities as well as equilibrium curves of temperatures versus these structural quantities. The results reveal that the combination of mechanical and thermal loads along with a compliant core material with mechanical properties that degrade with increasing temperatures shifts the behavior from a linear and stable (strength controlled) response into a strongly nonlinear response with limit point behavior and associated loss of stability, when large displacements and large rotations (geometrical nonlinearity) are included in the modeling.

Diesel engines have proven over the years important in terms of efficiency and fuel consumption to power generation ratio. Many research works show the potential of biodiesel as a substitute for conventional gasoil. Mainly, previous and recent researches have focused on experimental investigation of diesel engine performance fuelled by biodiesel. Researches on the mathematical description of diesel engine process running on biodiesel are scarce, and mostly about chemical and thermodynamic description of the combustion process of biodiesel rather than performance studies. This work describes a numerical investigation on the performance analysis of a diesel engine fuelled by palm oil biodiesel. The numerical investigation was made using a semi empirical 0D model based on Wiebe’s and Watson’s model which was implemented via the open access numerical calculation software Scilab. The model was validated first by comparing with experimental pressure and performance data of a one cylinder engine at rated speed and secondly by comparing with a six cylinders engine performance data at various crankshaft rotational speeds. Simulations were then made to analyze the engine performance when running on biodiesel. The calculations were made at constant combustion duration and constant coefficient of excess air. Results showed that the model matches the overall experimental data, such as the power output and peak cylinder pressure. The ignition delay was somehow underestimated by the model for the first experiment, which caused a slight gap on in cylinder pressure curve, whereas it predicted the average ignition delay fairly well for the second set of validation. The simulations of engine performance when running on biodiesel confirmed results obtained in previous experimental researches on biodiesel. The model will be further investigated for engine control when shifting to biodiesel fuel.

Influence of inclusion on the stress intensity factors under thermomechanical loads in a PM superalloy

This study deals with the effect of coupled thermal and cyclic mechanical loadings on the viscoelastic response of carbon black filled nitrile rubber. For this purpose, cyclic loading tests were performed at different temperatures by means of Dynamic Mechanical and Thermal Analysis (DMTA). The type and level of the thermomechanical loadings applied were chosen in order to determine the relative contribution of each of the mechanical and thermal loadings (and their coupling) to the viscoelastic response during the cyclic tests. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transformed Infrared spectroscopy (FTIR) analyses were also carried out to track the change in the chemical structure corresponding to the evolution in the viscoelastic response. First, results obtained show that due to the crosslink increase, the storage modulus increases with the number of cycles. It is also observed that temperature amplifies this phenomenon. Second, the cyclic mechanical loading is found to significantly amplify the effect of temperature.

The numerical assessment of elastic-plastic sheets under variable mechanical and thermal loads using a simplified two-surface yield condition

This paper addresses load order effects on elastic-plastic J estimation under combined mechanical and thermal loads for circumferentially cracked pipes. The load order effects, for various thermal gradient types and mechanical loading, are evaluated for a range of magnitudes of the loadings, crack sizes and material hardening. Variations of elastic-plastic J obtained by finite element analysis are compared with existing and proposed methods for use with the R6 defect assessment procedure. The load order effects are presented on the R6 failure assessment diagram (FAD) by calculating the two parameters Kr and Lr from the finite element results. It is shown that there are significant load order effects at large secondary stress cases but these are successfully treated by simplified methods proposed for use with R6.

In this study, the effect of a thermal barrier coating with yttria-stabilized zirconia (YSZ) and aluminum silicate (Al2O3·SiO2) alongside an NiCrAl bond coat on the engine performance and emission analysis was evaluated by using conventional diesel and pure palm oil biodiesel. These materials were coated on the piston alloy via plasma spray coating. The findings demonstrated that YSZ coating presented better engine performances, in terms of brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC) for both fuels. The piston with YSZ coating materials achieved the highest BTE (15.94% for diesel, 14.55% for biodiesel) and lowest BSFC (498.96 g/kWh for diesel, 619.81 g/kWh for biodiesel). However, Al2O3·SiO2 coatings indicated better emission with lowest emissions of NO, CO, and CO2 for both diesel and biodiesel. For the uncoated piston, the results indicated that the engine clocked the highest torque and power, especially on diesel fuel due to the high viscosity and low caloric value, and it recorded the lowest hydrocarbon emission due to the complete combustion of fuel in the engine. Hence, it was concluded that the YSZ coating could lead to better engine performance, while Al2O3·SiO2 showed promising results in terms of greenhouse gas emission.

Microstructural and mechanical characterization of stainless steel 420 and Inconel 718 multi-material structures fabricated using laser directed energy deposition

Advanced optimization of gas turbine aero-engine transient performance using linkage-learning genetic algorithm: Part II, optimization in flight mission and controller gains correlation development