نشریه تحقیقات موتور
پیاپی 66 (بهار 1401)

In this study, the combination of biodiesel-diesel, ethanol-diesel, and ethanol-biodiesel-diesel emulsion blends on performance and emissions of a direct injection diesel engine was investigated. High purity ethanol in three levels of 2, 4 and, 6 by volume percent and biodiesel prepared from waste cooking oil in four levels of 5, 10, 15 and 20 by volume percent were mixed with pure diesel. Thus, 11 fuel samples were prepared which were shown with BxEy, that x and y represent the volume percent of biodiesel and ethanol in the prepared mixtures, respectively. The experiments were performed at full load with the change in engine speed from 800 to 1800 rpm, with the interval 200 rpm. The results showed that pure diesel has the lowest specific fuel consumption at all of the speeds compared to other prepared mixtures. Using of B15E6 blend, reduced the emission of carbon monoxide by 40% compared to pure diesel. This mixture also, reduced the emissions of carbon dioxide and hydrocarbon by 27 and 55% compared to pure diesel, respectively.

Nowadays, turbochargers application has been essential to increase the internal combustion engine's power and reduce the emissions while engine size remains unchanged. In this research, the scaling of a centrifugal compressor of a turbocharger is investigated to increase the mass flow rate by 15 percent. In contrast, compressor pressure ratio, efficiency, and performance range should be preserved, and the general dimension will be unchanged to cut the construction costs. This study has focused on the purpose in which the compressor should be compatible with the turbine, so the rotational speed is almost unchanged by the geometrical modification during the investigation. Two scenarios are considered, including reducing the hub radius, increasing the shroud radius, and changing the location of the splitter blade. In the first scenario, the hub radius is decreased by 1.8 mm, and only a 2 percent improvement in mass flow rate is obtained. In the second scenario, in addition to reducing the hub radius, the shroud radius is increased by 1.63 mm. The splitter blade is located at 35 percent of the meridional coordinate. One-dimensional design and three-dimensional simulation show that the mass flow rate is improved by 16.5 percent. The study introduces a reliable analytical-numerical method to scale up a centrifugal compressor without any significant modification on general dimensions, leading to a drastic change in the turbocharger casings and an increase in manufacturing costs). The method is a general way to scale up a centrifugal compressor extended for turbochargers or other applications.

The purpose of this paper is to optimize the gearbox conversion ratios of vehicles and the gearbox gear ratios are calculated in such a way that the engine provides the maximum possible traction, thus providing the maximum slope force with respect to the stability condition. First, the gearbox conversion ratios are determined by considering the type of vehicle and the appropriate calculation method. Then the gear conversion ratios are changed so that, considering the stability condition, the traction force diagram in the gears is as close as possible to the ideal traction force diagram and the uncovered parts are less in the ideal traction force diagram and the actual middle gear diagram. This is done for a two-stage gearbox with two intermediate axles, which is located in the transmission line with a diesel engine. The obtained results show that with the optimization of the gearbox, the rate of improvement of traction force in the maximum case is 17.5%, slope 16.3%, acceleration 17.2% and torque 13.5% in 3rd gear. Comparisons made for validation with a base vehicle also show a good agreement between the base vehicle and the vehicle in this study.

In this applied research, using the breakdown maintenance of the machine engine, a procedure maintenance and preventive maintenance on the fuel system, which was the main cause of the engine breakdown of these machines, was investigated. A case study was conducted on the engine of 80 Bumag BW211D rollers produced by Bumag factory, equipped with Common Rail fueling system, which were working in road construction projects in Fars, Bushehr, Hormozgan, Kohkiluyeh and Boyr Ahmad provinces. First, the data on the amount of damage and imposed costs were collected, and by designing eight service models on the fueling system, which consisted of performing and not performing three periodic services of 250, 500, and 1000 hours on the engine and the fueling system, the life of the injectors of these devices were analyzed completely randomly through the F test with an error level of 1% and the significant effect of the services on the lifetime of the injector needles was observed. Each other and on the life of the injector needles was significant. The significance of the effect of triple services in reducing fuel system costs and increasing the life of injector needles based on engine operating hours covered a low range of 700 hours in case of no service to a high range of 10,000 hours in case of full service. By examining the working hours compared to the increase in the cost-to-income ratio of the machine in case of no service, the inverse relationship between cost and income was drawn with R2=1. At the end, the suggested solutions to increase the life of the injector needles such as using water separator filters and tank drainage from water and sediments were suggested.

The aim of this study was to investigate the effect of magnetic flux density (6000 Gauss) on diesel engine fuel consumption and emissions. Experiments were performed at different distances with respect to the magnet in the fuel line (20, 40 and 60 cm) and at different engine speeds (1800, 2100, 2400 and 2700 rpm). We then selected carbon monoxide (CO), unburned hydrocarbons (UHC), carbon dioxide (CO2), nitrogen oxide (NOX) and fuel consumption as our study traits. According to the findings, the levels combination of 1800 rpm and 40 cm resulted in the greatest reduction of carbon monoxide, which was declined by 67 % compared to the control sample. The least amount of unburned hydrocarbon was observed at 1800 speed and 40 cm distance from the magnet with a value of 131.33. Moreover, the highest amount of nitrogen oxide was found in the 1800-20, 1800-40, 2100-40 levels compounds with 62, 59, 57 and 56 ppm, respectively. Fuel consumption was 3.023, 3.23, and 3.25 (Lit/h) at the maximum engine speed and distances of 20, 40, and 60 cm from the magnet, correspondingly; and dropped by 12, 6.1, and 5.52% compared to the control sample. We recruited response surface methodology to optimize process conditions. Based on the results, the optimal conditions were obtained at 1800 rpm and a distance of 37 cm of magnet on the fuel line. Under these optimal conditions, the amount of carbon monoxide, unburned hydrocarbons, carbon dioxide, nitrogen oxide and fuel consumption were 0.49%V, 128.45 ppm, 1.96%V, 61.3 ppm, and 1.92 (Lit/h) with desirability of 0.7, respectively.

About 30 to 40 percent of the total energy produced in internal combustion engines is converted into useful mechanical work at best, and the rest is transferred to the environment through exhaust gases and engine cooling systems. One effective way to overcome mentioned issue is to recover the exhaust gas heat of internal combustion engines. In the present study, in order to recover the wasted energy from the ICE exhaust gases, use of Stirling engine has been suggested. For this purpose, modeling of the Stirling engine was performed by using the second-order method. To approach operating conditions of the stirling engine to actual state, heat and working losses for each moment of the engine movement were calculated separately and added to the modeling. The modeling of the Stirling engine was performed for three operating pressures in different engine speeds, depending on the thermal energy of the internal combustion engine. The results show that, at best condition, Stirling engine produce 5/8 to 10 horsepower and 20 to 22 N.m of torque. By adding these values to the IC engine, we will see a significant increase in power and torque of the hybrid system. It is also possible to achieve a constant torque over a wide range of engine speeds in hybrid engine by using different operating conditions of stirling engine.