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Showing 3 results for Sensitivity Analysis

A. Kakaee, M. Keshavarz,
Volume 2, Issue 3 (7-2012)
Abstract

In this study it has been tried, to compare results and convergence rate of sensitivity analysis and conjugate gradient algorithms to reduce fuel consumption and increasing engine performance by optimizing the timing of opening and closing valves in XU7/L3 engine. In this study, considering the strength and accuracy of simulation GT-POWER software in researches on the internal combustion engine, this software has been used. In this paper initially all components of engine have been modeled in GT-POWER. Then considering the experimental result, results confirmed the accuracy of the model. After model verification, GT-POWER model with MATLAB-SIMULINK are coupled each other, to control the inputs and the outputs by sensitivity analysis and conjugate gradient algorithms. Then the results compared with experimental results of initial engine too. The results indicated that optimal valve timing significantly reduced brake specific fuel consumption and when is used variable valve system for opening and closing angle of intake and exhaust valves, the mean improvement percentage in brake specific fuel consumption from sensitivity analysis is nearly 5.87 and from conjugate gradient is about 6.69. too, for example with increasing engine speed late closing intake valve causes optimized brake specific fuel consumption and from 3500rpm this trend stops and in 4000rpm and 4500rpm early closing of intake valve results in more optimized brake specific fuel consumption. Then up to 6000rpm again late closing of valve would be favorable. Also results indicated that convergence rate of conjugate gradient algorithm to reaching the optimal point is more than sensitivity analysis algorithm.


Vahid Tavoosi, Dr Javad Marzban Rad, Dr Ramazan Mirzaei,
Volume 8, Issue 2 (6-2018)
Abstract

Vertical dynamics modeling and simulation of a six-wheel unmanned military vehicle (MULE) studied in this paper. The Common Mobility Platform (CMP) chassis provided mobility, built around an advanced propulsion and articulated suspension system gave the vehicle ability to negotiate complex terrain, obstacles, and gaps that a dismounted squad would encounter. Aiming at modeling of vehicle vertical dynamics, basic and geometrical parameters defined and degrees-of-freedom specified on a compromise between accuracy and complexity of two models. Equations of motion provided on two linear and nonlinear 5-degree-of-freedom models using two different modeling methods. There is good agreement between time responses of two presented models. The main differences of two models observed in articulated suspension degrees-of-freedom while the vehicle subjected to high frequency maneuvers that cause severe oscillations on wheels and arms in comparison to vehicle body due to lower mass and inertia properties. The linear model can be used to design a controller and the nonlinear to predict vehicle motion more accurately. Sensitivity analysis of the influential parameters is also presented to specify effects of different parameters. Results of this study may be used to design articulated suspension and making next frequency analyses.
Mr Mohsen Motaharinezhad, Dr. Abbas Rahi,
Volume 9, Issue 1 (3-2019)
Abstract

In internal combustion engines, exhaust valve and its seat gain considerable temperature as the hot gases exit through them. So, the rate of heat transfer should be under control. In this study, the contact heat transfer coefficient has been estimated. An experimental study on an Air-Cooled internal combustion engine cylinder head has been considered. Using the measured temperatures of sensors located in specific locations of the exhaust valve and the seat and the method of linear extrapolation, the surface contact temperatures and constant and periodic contact heat transfer coefficient were calculated. Also, a sensitivity analysis has been done to study the effects of different parameters of contact pressure, contact frequency, heat flux and cooling air speed on thermal contact conductance. The results show that between the major four considered parameters, the thermal contact conductance is more sensitive to the contact pressure, then the contact frequency, heat flux and the cooling air speed are the most affecting parameters on thermal contact resistance.

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