Materials Selection for Dynamic Variable Geometry Turbocharger Flow Control Application | Author : Apostolos Pesiridis, Srithar Rajoo, Kishokanna Paramasivam, Ricardo Martinez-Botas, Robert Macnamara | Abstract | Full Text | Abstract :This paper investigates material candidates for use in a turbocharger turbine technology known as the active control turbocharger (ACT) which is a distinct technology to the Variable Geometry Turbine (VGT) for turbochargers but broadly based on this technology. This concept involves the use of an actuated nozzle mechanism that is oscillated to provide a more active change of the turbine inlet area to the turbine resulting in response to incoming instantaneous exhaust gas flow pulsating characteristics to provide greater extraction of exhaust gas pulse energy. Careful materials selection is required for this highly dynamic application to overcome the creep, fatigue, oxidation and high temperature challenges associated with the diesel engine exhaust conditions to which this technology is exposed to. The investigation of materials suitability for this application was conducted for steady and transient flow conditions. It was found that the vane undergoes cyclical loading at a maximum stress of 58 MPa for 109 cycles of operation at an inlet temperature of 800oC and pressure of 240 kPa. The vane experiences maximum stresses in the closed position which occurs at a vane angle of 70o. It has been found that the implementation of ACT technology is possible using currently available materials. Using the information obtained from the transient analysis, a material selection process was developed to incorporate the specific application requirements of the ACT application. A two tiered weighting decision process was applied; first to analyse the relative importance of various material properties to each application requirement and then to the properties of individual materials. Materials Nimonic 90 and IN X750/751 obtained the highest overall scores from the selection process and were shown to be capable of withstanding the creep requirements to a minimum safety factor of 2, a failure mechanism of primary concern to the high temperature application. Nimonic 80A, although receiving a final rating 8% lower than Nimonic 90, also showed promising potential to offer a solution, with superior corrosion properties to both Nimonic 90 and IN X750/751. In addition to the specific results, a significant contribution of this work has been in providing a foundation for future numerical and material selection analyses for ACT development. |
| A Comparison of Variable Valve Strategies at Part Load for Throttled and Un-Throttled SI Engine Configurations | Author : Apostolos Pesiridis, Matt Barber, Alasdair Cairns | Abstract | Full Text | Abstract :The presented work concerns the study of the fuel consumption and emissions benefits achieved at part load by employing a fully variable valve train in a 1.6L SI gasoline engine. The benefits achieved when using variable valve timing alone, and combined with an early intake closing strategy for un-throttled operation were explored. In addition, particular interest was given to the presence of internal Exhaust Gas Recirculation (EGR) and its ability to reduce pumping loss at part load. An engine model employing multiple sub models to handle variable valve operation was constructed using a commercial gas dynamics engine code, allowing detailed analysis of three valve strategies. Using the engine model, a theoretical study was carried out to study key valve timing cases. A detailed breakdown of the mechanisms present in each case allowed a comprehensive understanding of the influence of valve timing on gas exchange efficiency and fuel consumption. |
| MFFNN and GRNN Models for Prediction of Energy Equivalent Speed Values of Involvements in Traffic Accidents | Author : Ali Yilmaz, Cigdem Aci, Kadir Aydin | Abstract | Full Text | Abstract :Accident reconstruction is a scientific study field that depends on analysis, research and drawing. Scientific reconstruction of related traffic accident on computer eliminates making decisions depending on initiative or experience of the expert and yields impartial decisions and evidences especially on events like matter for the courts or forensic investigations. In this study, data collected from accident scene (police reports, skid marks, deformation situation of involvements, crush depth etc.) were inserted properly into the software called “vCrash” which is able to simulate the accident scene in 2D and 3D. Then, 784 parameters, related to calculating Energy Equivalent Speed (EES) with a prediction error, were prepared according to several accidents. These parameters were also used as teaching data for the Multi-layer Feed Forward Neural Network (MFFNN) and Generalized Regression Neural Network (GRNN) models in order to predict EES values of involvements, which give idea about severity and dissipation of deformation energy corresponding to the observed vehicle residual crush, without requirement of performing simulation for probable accidents in future. Using 10-fold cross validation on the dataset, standard error of estimates (SEE) and multiple correlation coefficients (R)of both models are calculated. The GRNN-based model yields lower SEE whereas the MFFNN-based model yields higher R. |
| Structural and Thermal Analysis of Different Piston Materials with Cooling (Due to Combustion Pressure) Using Finite Element Analysis | Author : Puran Singh, Debashis Pramanik | Abstract | Full Text | Abstract :Piston is a cylindrical component fitted into the cylinder forming the moving boundary of the combustion system. It fits perfectly into the cylinder providing gas tight space with the piston rings and the lubricant. It forms the first link in transmitting the gas forces to the output shaft. Piston is a simple machine element which forms the combustion chamber as well as it is the one which receives the combustion thrust which is to be transferred to the crankshaft via connecting rod. Piston transfers the gas load from cylinder to the connecting rod which in turn transfers the load to the crankshaft in order to obtain mechanical energy [4, 5, 6]. In this research, we will be taking three different types of IC engines piston namely flat, bowled and shallow. These pistons will be made up of three different types of materials Alloy steel-1040, aluminium alloy-6061 and cast iron. Structural analysis will be carried out on all these three designs made up of these different materials to see if they can take the gas load on simulation software ANSYS. After that, thermal simulation of the piston will be done with cooling to see that feasibility of the piston to conduct necessary amount of heat on simulation software ANSYS. Then we will compare the result of structural and thermal analysis and decide the best design and also optimize the final design. |
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