نشریه تحقیقات موتور
پیاپی 67 (تابستان 1401)

Today, with the help of simulation models, engine performance can be modelled with a high level of precision, and thereby various strategies for the improvement of engine performance including the use of dual-fuel mixtures can be investigated. In the present study, a multi-zone thermodynamic simulation-code in Gasoline-Natural Gas (NG) mode with a Blow-by sub-model and a NO predicting-mechanism was developed. Then using a single-cylinder research-engine, experimental data were collected from various cycles via the use of skip < /span>-fire technique at the compression ratio of 10 for the dual-fuel mixtures of 100%, 90%, 75% and 60% Gasoline and the rest NG. From the obtained experimental data, two 200-cycle series of motoring and combustion without residual-gases were provided to verify the simulation code. In the motoring mode, the results of the simulating code equipped with Blow-by sub-model were compared with the experimental results. Then in the combustion mode, the results of the simulation code were compared with the average of pressure-crank angle experimental data in each dual-fuel mode. The performance of the simulation code was confirmed with an error of less than 4%. Finally, the sub-model for the prediction of NO emission revealed that NO emission decreased with the increase of NG fraction.

Belt tensioner is one of the main components in timing mechanism of IC engines. This component has an angular motion to adjust the timing belt tension and ensure the continuous connection between crankshaft and camshafts. This angular motion is one of the important parameters in design of the belt tensioner, which is evaluated during validation tests. The present paper, with the aim of using in modern validation tests, presents a new method for measuring the kinetic characteristics of the belt tensioner. The proposed method is a machine vision system that uses a deep neural network to track the movement of the belt tensioner indicator and then obtain its motion characteristics including angular displacement, velocity and acceleration. To this end, the engine test was designed and performed so that the belt travels its entire stroke. Simultaneously the movement of the belt tensioner was captured with a camera. The results showed that the tensioner indicator was correctly tracked with about 80% accuracy during the whole test. The maximum angular displacement of this component reached 14 degrees at the end of the test. The results also showed that the belt tensioner under study moved with the maximum angular speed and acceleration of 1 rad/s and 61 rad/s2. In addition, it was found that the frequency of the belt tensioner movement reached about 10 Hz. The results showed that the proposed method could be an appropriate alternative to conventional methods to measure the tensioner movement.

Al-Si alloys are widely used in the automotive industry. The most important microstructural factor, the changes of which have a great impact on the physical and mechanical properties of cast aluminum composites, is the distance between the dendritic arms. In this study, the effect of applied shear force on the morphology of dendritic arms of composites made by traditional casting, squeeze and semi-solid casting methods has been investigated. The effect of applied shear force, time and temperature of compositing and their effect on dendritic arm morphology have also been investigated. According to the obtained results, the best globular temperature and time for this type of composite in semi-solid state has been calculated. When stirring with a 70 amp electromagnetic current for about 60 seconds, the smallest spherical and smallest α particles are obtained at the same time, which can be expected to have the best mechanical and abrasive properties.

Today, cars play an important role in people's daily lives. Therefore, ensuring the safe operation of car parts and their connections that are affected by high oscillating stresses is very important. since considering the fatigue strength is the requirement to make sure the quality and safety of the cars. Due to this reason, in this paper, the interference fit of the bushing in Triangle suspension was evaluated using a stair case fatigue test and finite element simulation. The finite element simulation of the ​​different interference fit was performed and evaluated according to Gerber and Goodman criteria. Experimental results showed that the durability life for parts with an interference fit ​​of 0.22, 0.15, and 0.30 mm is equal to 1.41, 1.17, and 1.17 times the applied force in the vehicle. Also, the average Gerber safety coefficient calculated from the finite element simulation results is 1.16, 1.12, and 1.07, respectively. According to Goodman and Gerber, the highest reliability interference of 0.22 mm was estimated, which was also consistent with the results of the experimental test. Therefore, it can be said that with small changes in the amount of interference fit of parts in the joints, the fatigue life of the parts can be effectively improved, which is completely consistent with the results of the references

Due to the limited resources of fossil fuels and the pollution caused by them, the use of clean fuels seems necessary. In this regard, the development of electric or hybrid vehicles has great importance. In recent years, research areas related to autonomous electric vehicles have attracted the attention of automotive researchers and industrialists. These cars have different categories in terms of capabilities, including intelligent vehicle speed control. In this paper, dynamic modeling and longitudinal speed control of a level-one autonomous electric vehicle using GT-SUITE and MATLAB are investigated. Also, the model created in GT-SUITE software is validated with the help of data obtained from open-loop experimental tests. Then, after connecting the two software, the proportional-integral controller is designed to control the longitudinal speed of the vehicle and its parameters are adjusted.  Finally, the performance of the designed controller in controlling the vehicle speed in the presence of various conditions (road slope, wind blowing, and different velocity reference inputs) is evaluated.

The performance of the impeller of a radial flow compressor is highly affected by its geometric uncertainties. The geometrical characteristics of the impeller may change slightly during the manufacturing process or as a result of long-term operation, resulting in deviations from design performance curves. In this research, the performance sensitivity to each geometric parameter is determined using global sensitivity analysis, and the performance deviation interval is extracted using uncertainty quantification by the Kriging surface response method. For this purpose, initially, three categories of databases with a different number of impellers are created using geometric characteristics deviating from the original sample. For different geometries, the flow simulation in the impeller is performed using computational fluid dynamics in a viscous three-dimensional turbulent solver. A surrogate model which uses the Kriging method for each database to quantify the uncertainty more quickly is utilized. The results show that in 95.5% of cases, the pressure ratio and total to total efficiency and total to static efficiency fluctuate by 1.88%, 1.03%, and 1.56% around the predicted value, respectively. Moreover, the impeller's outlet radius is the most sensitive geometric parameter.