abolfazl mohammadebrahim

The vortex shedding from a bluff body can provoke structural vibrations known as flow-induced vibrations (FIV), which characterize an intrinsic phenomenon in the design of cylindrical structures. There are numerous passive and active methods to suppress FIV, among which suction and/or blowing on a cylinder surface is one of the most common approaches. In this work, different configurations of simultaneous suction and blowing are considered at two different Reynolds numbers corresponding to the galloping and frequency synchronization ranges. The parameters studied include the number of slots for suction and blowing, their length, and the velocity of the sucked and blown flow. The design of experiments method (DOE) is used to find the required simulation elements. The simulation results show that the dominant parameter in the reduction of galloping and vortex-induced oscillations and mass flow rate is the flow velocity in the areas of blowing and sucking. In addition, regression analysis is used to derive a relationship between various influencing parameters and performance parameters.

Considering the importance and the effect of the rotating flows inside the cylinder on the performance of internal combustion engines and the direct effect of these flows on reducing the amount of greenhouse gas emissions and reducing fuel consumption, it is essential to investigate the characteristics of these flows. Therefore, the issue of ensuring the performance of the swirl meters and the accuracy of the results obtained from the measurement becomes essential. Due to the lack of a specific and standard reference and the loss of performance of the swirl meter over time, it is necessary to have a method and means for its verification and calibration. The present study was carried out to validate the performance of the paddle wheel swirl meter and design a new and easy method for its calibration. The results simulation performed by the dynamic mesh method are very close to the results obtained from the experimental test and have high accuracy, because it directly simulates the performance of the paddle wheel swirl meter, but on the other hand, it requires a very high computational cost. According to the results obtained from the numerical solution and experimental test, the simultaneous use of the calibration equipment along with the correlation relationship is suggested as a fast and high-precision method.

In this paper, while examining the use of fuel cells in vehicles and past research, modeling of vehicles equipped with fuel cells with GT-SUITE software has been performed. In this modeling, various details have been considered and the specifications of a model vehicle have been used. In the following, the effect of effective parameters on the performance of the polymer membrane fuel cell is investigated. The simulation conditions are obtained by considering the existence of battery management system. The obtained results showed that with increasing the number of fuel cells and the surface area of the fuel cells, the output power of the fuel cell increases. Also, according to the simulation performed, with increasing the thickness of the fuel cells, the output power of the fuel cell remains constant. Although some results have been qualitatively predictable, it is important to know the impact of these parameters on the design. Then, the effect of load transfer coefficient and mass transfer coefficient of fuel cell mass was investigated. The results show the sensitivity of each parameter on the performance of the fuel cell and it was found that the effect of the parameters of the number of fuel cells and the surface area of the fuel cells is more pronounced than other parameters. Also, in these simulations the effect of changes made on the average temperature of the fuel cell was evaluated.

Flow-induced instabilities are one of the major challenges in the design of aerospace structures. Numerous passive and active control methods have been used to reduce the flow-induced oscillations of square cross-section cylinder as the basic geometry for structures with sharp corners. The suction and blowing flow control method are one of the most effective approaches for controlling the flow and consequently reducing the vibrations resulting from the aerodynamic forces, which so far are not considered for an elastically-mounted square cylinder which fluctuates freely in the transverse direction. Therefore, in this paper, suction and blowing flow control methods have been used separately to suppress flow-induced oscillations. In the suction-based method, a slut is placed on the front surface of the cylinder and in the blowing-based method another slot is inserted on the back surface of the cylinder. In the present study, the effect of suction and blowing velocities as well as the effect of suction and blowing slut lengths on the efficiency of the flow control approach was evaluated. According to the flow-structure interaction simulations, it is observed that the applied flow control method has been able to reduce flow-induced vibrations appropriately.

This paper is about the application of instantaneous angular speed (IAS) signal in a 3-liter six-cylinder gasoline engine. The study is in continuation of former work in which a measurement system was developed for this signal on a rotating machine. The future trend of the research is to measure IAS in an I.C. engine. Therefore, the objective of the current work is to provide a verified software tool which can run simulated experiments with IAS signal output under healthy/faulty conditions. An engine model with detailed crankshaft elements is established in the GT-SUITE[1]</sup> software. Under the GT-SUITE environment, IAS signal output is obtained through simulated experiments. In order to validate the tool, the first torsional natural frequency of the crankshaft obtained from frequency analysis on the IAS signal is compared with the result of modal analysis on the crankshaft structure using the F.E. method. Also, the value is compared with the prediction from the GT CrankAnalysis module. A good match is found, which shows the validity of the developed software tool. Faulty condition of misfiring in one cylinder is simulated using this tool, and expected observations on the IAS output signal are verified to address the future trend of the research using the developed tool in this study.

Vibration is a key factor of abrasion and destruction in the internal combustion engine. In internal combustion engines, the main causes of vibration is combustion pressure, connecting rod weight, piston weight and inertial forces. This vibration create corrosion and fracture in main part of engine such as crankshaft, camshaft and cylinder block in long time. This corrosion and fracture is effective on engine performance. Therefore is trying reduce or remove this vibrations for better engine performance. In multi cylinder engine, Counterweights are fitted on the crankshaft to eliminate the unbalance of forces and moments. In single and three-cylinder engines, the effects of inertia forces and moments cannot be completely eliminated using by counterweights. So balancer shaft is used to completely remove these effects. For the first time, the balancing shaft and flywheel is design with analytic equation and compare with result of simulation for one-cylinder diesel engine. (B112 of KIASA Company)

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 the design of the intake port of an internal combustion engine, investigation of the flow coefficient and the swirl ratio is important, simultaneously. They are effective on the volumetric efficiency and combustion efficiency, respectively. Steady flow testing of cylinder heads is one of the methods to measure the flow coefficient and the swirl ratio. In this study, at first, two different methods of swirl measurement are introduced and governing equations is presented. In the following, experimental tests with both methods are performed on the cylinder head and the results of them are investigated. Swirl measurement consist measurement of the rotational speed of paddle wheel or the torque is applied to a honeycomb to take into account the swirl ratio. The paddle wheel mechanism gives lower measured swirl ratio.