Mechanical Engineering

Compressor characteristics, being representations of the compressor pressure ratio as a function of gas flow through the compressor have been studied. Compressors are used in turbochargers to increase the pressure of air and also its density greater than ambient. Choosing the right compressor is very important in obtaining best power output of engine by turbocharging, so it is important to have compressor map for matching turbocharger with a particular engine. Compressor map is drawn by running compressor at varying speeds and mass flows. In this paper compressor characteristics were investigated through CFD analysis.

In metal machining process turning operation of cylindrical parts are machined on CNC turning machine. Present work includes the machining of cylindrical component having non-concentric shape. Rotary fixture is designed for machining on CNC turning machine. To avoid unbalancing of fixture, fixture must be balanced by adding the counterweight on rotary fixture to minimize machining rejection. The fixture can be balanced by dynamic balancing machine. In project work rotary fixture will balance by Computer Aided Mass Balancing (CAMB) methodology. The methodology for balancing rotary fixture will use to calculate counterweight to be added on rotary fixture along with its position.

This paper presents an embedded modeling approach for estimating the crack size in a rotating beam by predicting the vibrations of the cracked beam. The model embeds a non-linear switching function into a finite element model of the beam to characterize the effect of crack breathing on the local stiffness of the beam. Solving the model enables the prediction of the vibrations of the cracked beam and the evaluation of the modal frequencies of the vibrating signal using Chirp-z transform. Inputs to the model include the vibrations of the un-cracked beam to calibrate the model at the beginning, i.e., no need for run-to-fail tests. The model is validated and refined utilizing experimental data.

In this paper, a helical coil tube in tube heat exchanger was designed and used in carbon dioxide solar assisted heat pump system (SAHP) to provide hot water for domestic applications and to operate an air gap membrane desalination (AGMD) unit. Both theoretical and experimental studies to investigate the performance of the gas cooler with Glycol Ethylene 50% and water as coolants were performed. The experimental part to study the behavior of the carbon dioxide in the supercritical region was conducted on the R744 heat pump test rig located at Department of Energy and Process Engineering – NTNU. On the other hand, FEA using ANSYS Fluent 18.1 was used to conduct the theoretical analysis. The study includes effect of inlet temperature of both coolants, effect of discharge pressure, effect of mass flow rate of water, and logarithmic mean temperature difference (LMTD). Good agreements between Experimental and simulation results were achieved. Results showed that the outlet temperature of the refrigerant from the gas cooler decreased from 81 oC to 40 oC, with 0.085 bar average pressure drop due to the heat rejection process. The outlet temperature of the refrigerant from the gas cooler in case of water is 8 oC lower than with ethylene glycol 50%. The outlet temperature of water reached 57 oC which is enough for domestic applications and to operate the AGMD unit to produce fresh water. It is observed that the pressure drop in the refrigerant by using water as coolant is higher by 0.2 bar than when ethylene glycol 50% used. Results also revealed that the value of LMTD of the gas cooler using ethylene glycol 50% is 24.3 % higher than the LMTD value when using water.

In this work, an experimental study to obtain the fatigue endurance limit for an aluminum alloy7075-T651 were carried out at stress ratio R=-1 and rotary bending tests. The fatigue tests were performed at RT and 250 °C in order to establish the S–N curve equations. The fatigue endurance limits for the alloy at different temperature conditions were calculated at 107 cycles from the empirical S-N curve equations. It was found that the fatigue endurance limit decrease with increasing the temperature. Also The effect of shot peening on the rotating bending fatigue behavior of 7075-T651 was studied. The fatigue strength of specimens tested at250oC at 107cycles is reduced about 12%. The fatigue strength of specimens tested at250oC prior to (10 min.) SP at 107cycles is increased by 7.2%. The roughness of the samples increases after shot peening which leads to the deterioration of the fatigue strength, because the surface of the samples become prone to nucleation of cracks.

Shot-peening is a cold-working process primarily used to improve the fatigue life and strength of metallic structural components. In this work, the shot-peening time (SPT) effect on fatigue life of 7075-T651 Al-alloy was investigating at room temperature stress ratio R=-1 and reversed bending. An increase in shot-peening time (SPT) resulted in an increase in fatigue life improvement percentage (FLI %). For 5 SPT, reducing the applied stress, increasing (FLI%) while at 10 and 15 SPT reducing the applied stress reducing the (FLI%).

In this work , an experimental study to obtain the fatigue endurance limit for two aluminum alloy , 2024 and 5052 , were carried out at stress ratio R=-1 and rotary bending tests . The fatigue tests were performed at RT, 100 °C, 200 °C and 300 °C in order to establish the S–N curve equations. The fatigue endurance limits for both alloys at different temperature conditions were calculated at 107 cycles from the empirical S-N curve equations. It was found that the fatigue endurance limit decrease with increasing the temperature. Also the reduction percentage in fatigue endurance limit for 5052 Al. alloy was higher than that of 2024 Al. alloy.

In this work, an experimental study was carried to obtain the fatigue damage for aluminum alloy, 2024-T4 under rotating bending loading and stress ratio R= -1. The experiments were done at RT(room temperature) ,25oC ,and 200oC. A modified damage stress model was suggested to predict the fatigue life under elevated temperature which has been formulated to take into account the damage at different load levels. The microstructure and hardness of aluminium alloy after fatigue-creep interaction testing have been investigated. Attention has been paid to the role of the microstructure and hardness on the fatigue-creep strength of aluminum alloy. It has been shown that, there is a little effect of microstructure in the cyclic response of aluminum alloy, while the hardness has a significant effect on the fatigue-creep strength. This is described numerically.