نشریه تحقیقات موتور
پیاپی 42 (بهار 1395)

In this study, the effect of fuel injection discharge curve and injection pressure simultaneously for upgrading power of heavy duty diesel engine by simulation of combustion process in AVL-Fire software are discussed. Hence, the fuel injection discharge curve was changed from semi-triangular to rectangular which is usual in common rail fuel injection system. Injection pressure with respect to amount of injected fuel and nozzle hole diameter are changed. Injection pressure is calculated by an experimental equation which is for heavy duty diesel engines with common rail fuel injection system. Upgrading power for 1000 and 2000 bar injection pressure are discussed. For 1000bar injection pressure with 188mg injected fuel and 3mm nozzle hole diameter in compare with first state which is semi-triangular discharge curve with 139mg injected fuel and 3mm nozzle hole diameter, upgrading power is about 19% whereas the special change has not been observed in cylinder pressure. On the other hand, both the NOX emission and the Soot emission decreased about 30% and 6% respectively. Compared with first state, for 2000bar injection pressure that injected fuel and nozzle diameter are 196mg and 2.6mm respectively, upgrading power is about 22% whereas cylinder pressure has been fixed and NOX emission and the Soot emission are decreased 36% and 20%, respectively.

The influences of different diesel/biodiesel blends and EGR rate on brake specific fuel consumption (BSFC), exhaust gas temperature, NO, HC, CO emissions, are studied and demonstrated. In this paper a four stroke direct injection, water cooled, diesel engine was used. Biodiesel either in neat form or as a blend with diesel fuel is extensively investigated to solve the twin problem of reduction of fossil fuels and ecological degradation. Exhaust gas recirculation (EGR) is an impressive technique for decreasing NO emissions. When EGR is utilized in engine, NO emission is decreased. If the engine was fueled with biodiesel-diesel blends, the BSFC would increase due to the lower brake power produced and It was found that BSFC increased with increase in EGR rates. Engine power and torque decreases through the use of biodiesel fuel blends. The results showed that B0 stands on the top level of power and B50 is at the lowest level. Reduction in exhaust gas temperature was observed but emissions of HC and CO were found to be increased with usage of EGR.

Vehicle Emission is one of the main causes of environmental damage. Vehicle engines produce carbon dioxide (CO2), hydrocarbon (HC), Nitrogen oxides (NOx) and many other harmful substances. An investigation was conducted using a compression-ignition engine fuelled with different ratios of blends of diesel and biodiesel at different EGR rates. The effects of different ratios of fuel blends and EGR rate on the emission characteristics (unburned hydrocarbon (HC), nitric oxide (NO), carbon dioxide (CO2) and oxygen (O2) were examined. The air-fuel equivalence ratio (λ), oil temperature and intake gas temperature were also analyzed. Results show that the different ratios of blends of diesel and biodiesel decrease HC emissions compared to those of the diesel fuel. The addition of biodiesel can increase NO, CO2 and O2 emissions compared with that of the diesel. EGR can reduce NO emissions in a compression-ignition engine fueled with diesel and biodiesel blends. The results also indicate that fuel consumption and air-fuel equivalence ratio were decreased by 19.2% and 72.9%, respectively, for 20% biodiesel blend with 20% EGR compared to diesel fuel without EGR. Intake gas temperature and oil temperature were also observed to increase by 87.5% and 6.2%, respectively, for 20% biodiesel blend with 20% EGR compared to diesel fuel without EGR.

In modern engines with higher compression ratios, severe pressures and non-uniform heating up is occurred for the engine parts. The piston as the most critical part among all automotive components has been the subject of numerous studies on calculation of temperature distribution, but thermal stress analyses are limited. In this study, the piston of gasoline engine XU7 which is widespread in Iran transport section is considered for thermo-mechanical investigation. A 3D linear static stress analysis is constructed in COSMOS Works to determine the stress distribution during the combustion stroke. The maximum normal stress takes place at the middle surface of the piston crown. The von Mises stress is found to be critical on upper parts of the pin-hole area. Effect of ceramic coating layer on stress distributions are evaluated and compared with results obtained for a traditional uncoated piston. According to the results, the maximum stress can be readily controlled by increasing the thickness of ceramic layer.

Alternative fuels are intensively investigated for the replacement of the diesel fuel. Today the diesel power generators are mostly used in the various industrial companies in Iran. Therefore, it is necessary to estimate the level of performance of the diesel power generators fueled with biofuels. For the first time, in this study, the prediction of the performance of a diesel power generator model CAT3412 is carried out for different neural networks to define how the inputs affect the outputs using the biodiesel blends produced from waste cooking oil. Diesel fuel, B100, and biodiesel blends with diesel fuel, which are B20, B50, and B80, were used to measure the engine performance for different engine loads at the rated engine speed. In this paper, artificial neural network models are proposed for the prediction of brake power, brake torque, BTE and BSFC. The coefficient of multiple determination values are found to be above 0.95 for all the models. It is evident that the ANN models are reliable tools for the prediction of the performance of diesel power generator.

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.