نشریه تحقیقات موتور
پیاپی 43 (تابستان 1395)

The purpose of this study is improvement of tribology properties St37 steel by formation of a surface composite layer containing alumina particles by GTAW welding method. To do this, the steel surface with 10% volume of alumina particles at three different currents of 90, 110 and 130 Amper with this method was covered. Reciprocating wear test, for wear resistance of the samples was carried out and their wear surfaces were examined by scanning electron microscopy. The results show that the coating of this process is having freeze-dendritic structure containing the alumina particles. The presence of these particles with reducing heat input cause increasing hardness and improvement wear behavior of the coatings. The range of increasing hardness the coatings made between 225 to 332 Vickers was measured and the amount hardness of the uncoated sample is about 180 Vickers. The results of the wear behavior of the coatings represent a significant improvement in their wear behavior in presence of the alumina reinforce with reducing heat input. The main mechanism of wear in the uncoated sample and the coated samples is adhesive wear. Finally, with designing and manufacturing of engine parts from mentioned coating in this study, hardness and wear resistance can be increased and thus better efficiency of the engine is achieved.

In this paper, by using of the experimental results and numerical simulation with AVL FIRE software and using of artificial neural network, NOx and soot emissions and fuel consumption of a diesel engine was modeled, that input variables of modeling are, air intake temperature, mass fuel injected, fuel injection timing, injection duration, engine speed and IVC timing. Then by using of ant colony optimization algorithm and based on the obtained models for outputs, values of NOx and soot emissions and fuel consumption has been optimized. For this purpose, by using of experimental data and numerical simulation, the arranging for modeling of performance and output was provided by the ANN.
Artificial neural network with Levenberg-Marquardt training algorithm and using of the experimental and numerical data was applied for modeling and training of relationship between these parameters and this method was applied as a predictive method of ant colony algorithm to find the optimal values and used as a subroutine. Then the design variables that optimized the objective functions were obtained. The results show a fast convergence and good response times and optimizing the control parameters of the ant colony algorithm compared with other metaheuristic algorithms. Due to the rapid and significant convergence of output parameters, combination of artificial neural network (ANN) and ant colony optimization (ACO) can be used as an effective method in intelligent control systems for diesel engines to reduce emissions and fuel consumption.

The aim of the present study was to examine the effect of throttle valve opening positions on the analysis of MVH 418 engine exergy using ethanol-gasoline mixtures ( ¡ ¡ ¡ and ). In so doing, the definitions dealing with exergy and pertinent exergy equations as well as their applications for closed systems were provided. The results of this study showed that the largest share of the irreversibility in the engine was combustion process. In addition, the results showed thermomechanical exergy, burned fuel exergy, exergy with heat transfer and exergy with work transfer, for ¡ and fuels in full throttle valve opening were higher compared to the 25%, 50%, and 75% throttle valve opening positions. Furthermore, it was found that the efficiency of thermodynamic second law in 25%, 50%, and 75% throttle valve opening positions were reduced for 18.7%, 29%, 60.6%, for 21.5%, 32.7%, 61.5%, for 23%, 35.4%, 62.5%, for 22.8%, 35.5%, 63.6%, and for fuel 27%, 40%, 65% respectively compared to 100% position.

Implementing turbocharger is a well-known technology to down-sizing of the internal combustion engine with keeping the torque and power output. But, implementing this technology has some problems such as delays in transient engine operation period, and pressure increment in exhaust pipe. Implementation of electrical supercharger besides the turbocharger is a solution to overcome these problems. In this paper, the use of electrical supercharger on a four-cylinder turbocharged IC engine, has investigated. For this purpose, the well-known engine simulation software, GT-Power has been implemented to evaluate the optimum location of electrical supercharger in the intake air passages. Simulation results show superiority of engine performance is achieved when electrical super charger is located on the upstream of mechanical turbocharger. In the­­ next step, a comparison between the performance of simulated engine and the turbocharged engine, performed. Results of this comparison showed that the use of electric turbocharger dramatically improves transient performance of the engine.

In this paper, a control oriented strategy has been used to manage thermal behaviors in an IC engine. For this purpose, an electrical thermostat along with a special strategy in engine control unit (ECU) is utilized to achieve better engine outputs including torque, emission, fuel consumption and knock targets in different engine thermal fields. Our activities are divided into three main categories: software development, hardware development and analyzing results on NEDC test on vehicle. In the software phase, a model was designed to control the electric thermostat through various working conditions. This model presents proper PWM (Pulse Width Modulation) to electric thermostat to control engine thermal management considering other effective inputs like intake air temperature and cooling fans responses. Hardware development includes installation of single-act and double-act electric thermostat on vehicle cooling system. Furthermore, the control software applies on GCU (Global Control Unit) to connect software to hardware on vehicle. Finally, all important parameters are recorded through NEDC test on vehicle with Single-act, Double-act electrical thermostat and compared with results of standard mechanical thermostat. Results show better achievement in torque, emission, fuel consumption and knock outputs.

Nowadays, one of important parts in combustion engines is the turbo-charger, which could improve the performance. Such this component and especially blades of the turbine, is working at high temperatures. Based on this condition and according to centrifugal forces in blades, one of design parameters is the creep strength of the material. For such condition, nickel-base super-alloy has been utilized. In this article, the hardness of 713C nickel-base super-alloy (which has been used in turbine blades of engines) increased by a typical heat treatment. For this objective, the design of experiments was utilized and the hardness through parallel and vertical lines to the grains direction in the material micro-structure was measured at different values of the solution temperature and time in the heat treatment. Experimental results showed that optimum values for the solution temperature and time are generally 1200˚C and 60 min, respectively, when the hardness increased. The sensitivity analysis indicated that effects of the temperature parameter are more significant in comparison to other parameters.