a. hajiali mohammadi

A multi-objective optimization study and sensitivity analysis of a SI engine piston-rings pack using dynamics analysis software (AVLExcite Piston&Rings) and optimizer software (modeFRONTIER) are presented. The effects of changing the piston rings' tangential force and face profile on the oil and gas flow behavior inside the piston-rings pack are investigated by calculating the lubrication oil consumption, blow-by, and power losses. The feasibility of the simulation model was determined by comparing it to empirical data obtained from experimental testing of the engine to estimate the amount of oil consumption and blow-by gas flow. Using the statistical modeling algorithm SS-ANOVA, multi-objective optimization investigates the individual and interaction effects of the three rings' tangential forces. This method significantly reduces the time and cost required to find the optimal design, an approach not reported in previous studies. The results showed a strong correlation between simulation and experimental test results, indicating an acceptable match during model validation. Furthermore, the predictions show that tangential forces affect sealing performance; thus, modifying the tangential force resulted in a 30% reduction in oil consumption and less than a 0.8 percent increase in friction. Furthermore, the LKZ oil control ring model efficiently reduces oil consumption by 25% while slightly increasing friction (about 10 percent without face coating).

Recently, there have been problems with particulate matter pollution in diesel engines and it has reduced production rate of these engines and also, it has accelerated the development of new technologies for PFI and GDI gasoline engines. The spray characteristics has significant impact on the combustion efficiency, power and emissions on internal combustion engines. In This study, effect of injection pressure on the fuel spray penetration, spray cone angle and separation angle has been investigated for EF7 bi fuel engine and an experimental formulation for spray penetration was introduced. The method of Schlieren Imaging method was used to obtain the geometric characteristics of the fuel spray. The images were processed in MATLAB software and the penetration, cone angle and spray separation angle as geometrical properties were calculated. The Otsu method was used to obtain an appropriate edge threshold of image. Investigation of the injection pressure effect on the penetration concluded an experimental formulation for penetration versus time and injection pressure. This equation was linear according to time and square root of injection pressure with maximum error of 8.4%. The penetration of the two fuel sprays (for both injectors tested) had a little difference at the similar pressures and injection times. It was concluded also the cone angle and spray separation angle increased with increasing injection pressure.

The novel diesel engines with advanced fuel injection systems are equipped with solenoid injectors comprising multiple small nozzle orifices which makes considerable improvement in fuel spray characteristics and engine performance along with providing high pressure fuel injection system. On the other hand, poor fuel quality, impurities and heavy metal elements in the diesel fuel, and high temperature medium in the diesel engines combustion chamber lead to remarkable deposits formation in the small holes of the nozzle. In addition, it results in partial or complete nozzle hole obstruction which is called injector nozzle coking having detrimental effects on discharged spray ideal behavior and proper engine performance. In this work, the analysis of coking phenomenon influences on diesel spray macroscopic characteristics have been done. Initially, the coked injectors with different time operation and deposit amounts are prepared under experimental and specific operating conditions. Then, the images recorded from the spatial and temporal evolution of a diesel spray in various injection and chamber pressures, are processed through the extended code in MATLAB software in order to analyze discharged fuel spray characteristics. The SCHLIEREN Imaging Method with high speed camera has been utilized in a CVC (constant volume chamber) without combustion. Non-Destructive Electron Microscopy Method of SEM (Scanning Electron Microscope) imaging was utilized in order to analyze sediments quantity and construction changes during injector working in the real engine conditions. The results show that, sediments occupy 20, 40, 75 and 90% of the total hole opening surface, respectively in the injectors with 300, 700, 800 and 900 hours operating time. By increasing the injector operation time and accumulated sediment amount on the nozzle, the discharged injector spray exhibits a more inappropriate behavior. Moreover, The Results revealed that coking has considerable effects on the spray tip penetration at low injection pressures. As injection pressure increases, the decreasing rate of the penetration length alleviates gently. In other words, at high injection pressures (1500 bar and higher) the penetration length has minor drop compared with non-utilized injectors even at 900 hours operating time, but the spray projected area can be reduced up to 28% in high chamber pressures.

Bimetallic parts are used in many industries for weight and cost reduction of workpieces, working under high loads and wear. One of the application for this type of composite material is in automotive industry. In this work, the tool wear and cutting forces in the face milling of bimetallic parts made of aluminum and cast iron were investigated. A356 and GG25 alloys that are common materials for bimetallic engine cylinder block were selected as material for aluminum and cast iron samples, respectively.  Machining length was  3.6 meters in the experiments and the tool wear was calculated on the flank face of tool using image processing method (KNN approach). Results indicated that with the machining parameters selected here, the wear of aluminum sample is not significant but the wear for cast iron and bimetallic materials was considered. It was also discovered that the wear and machining force for bimetallic parts are much higher than samples with cast iron material and the analogy was observed between cutting force and tool wear quantities. From this, it can be concluded that instead of time consuming wear tests, the tool wear trend in face milling of bimetallic parts can be predicted from cutting force measurements. It is also conculded that KNN image processing method is very accurate for calculating the tool wear.

In this study, the effect of using of aluminum oxide and silicon oxide nanoparticles simultaneously into dielectric has been investigated in the process of electrical discharge machining of titanium alloy Ti-6Al-4V. After analyzing the parameters affecting the process of the electrical discharge machining using nanoparticles, intensity of the current, concentration, pulse on time, and particle composition were considered as input parameters. The effect of each parameters has been investigated on three levels; the material removal rate (MRR), the tool wear rate (TWR) and the surface roughness (SR) of the work piece. With respect to the development of the industry in the use of environmentally friendly dielectrics, deionized water was used as the dielectric fluid. Also, Design Expert software has been employed for the design of the experiments, analysis of the results and optimization of the parameters. The results showed that the best surface morphology is obtained by machining with the addition of nanoparticles in the relative composition of 50%. In this percentage of the composition, the surface roughness has the least value of the crack and the recast layer. In addition, the maximum value of the MRR and minimum value of TWR can be achieved in 12A of current intensity, 100µs of pulse on time and 75% of relative composition.

In this paper, the short-term creep behavior of the Inconel-713C superalloy after different pre-treatments including the ageing and forging processes has been studied at 850 °C. The ageing heat treatment was heating at 930 °C for 16 hours without solutioning process. The optical microscopy (OM) and the scanning electron microscopy (SEM) techniques were applied for microstructural evaluations. The results showed that although the ageing treatment increased the γ’ phase content, the age-hardened material had a lower creep lifetime (about 40%) with respect to the as-cast alloy. This was related to the decrease in the amount of M23C6-type secondary carbides precipitation. When the Inconel-713C superalloy specimen was forged at 1200 °C, the third stage of the creep curve (strain versus time) increased drastically and shortened the creep lifetime. The small grain size of the forged specimen was responsible for such inverse creep behavior. In addition, fractographs of this specimen indicated intragranular cracks on the ruptured surface. When the forged sample was age-hardened directly without the solutioning treatment, the creep lifetime increased about 4 times as compared to the forged specimen. Inconel-713C Superalloy Short-term Creep Age-hardening Forging Microstructure