نشریه تحقیقات موتور
پیاپی 59 (تابستان 1399)

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 Stirling Cycle is one of the thermodynamic cycles that is close to Carnot cycle in term of theory, and these advantages cause to using Stirling engines in wide industries. The main objective of this research is experimental investigation of Stirling Gamma engine for refrigeration. In this investigation, effect of working fluid air and helium, operatring pressure of working fluid and dynamo power on refrigereation generation have been investigated. Results show that with using air fluid with power 520.8 W and operating pressure 3 bar and in 10 minutes could reach to temperature -23°C and with using Helium fluid in power 420 W and operating pressure 6 bar and in 10 minutes could reach to temperature -21°C. In experimental implement has been tried to reach lower than 10 percent error results in various part of engine like, insulation, leaking, belt lash and measurement devise Results show that increasing power of power supply mean gas pressure, time of turning on power supply and using fluid such as air, helium are effective in refrigeration.

Today, due to the various usage of compression ignition engines in urban transportation, as well as the need to reduce exhaust emissions and control fuel consumption, the use of alternative fuels has become common in diesel engines. Gaseous fuel is one of the most common alternative fuels that can be used in diesel engines. The utilization of alternative fuels in compression ignition engines requires the study of the combustion quality and the type of flammable mixture formation in the combustion chamber. Fuel injection parameter play a significant role in the combustion quality of dual-fuel diesel/gas engines. The injection timing and gaseous fuel mixing percentage together are among the parameters associated with fuel injection. In order to investigate the effect of fuel injection timing on the combustion quality of dual-fuel diesel / gas engines, a study was conducted. In this research, dual-fuel diesel engine is evaluated at two different speeds using the CFD method. To this research, three modes were selected for the fuel IT: BTDC 22°, BTDC 18° and BTDC 14° and three modes for gaseous fuel mixing percentage: 90%-10%, 85%-15% and 75%-25%. The results of numerical studies showed that with increasing fuel injection timing in a diesel / gas dual-fuel engine, the combustion chamber temperature and cylinder pressure peak (PCP) was increased. Increasing the IT also increased the ignition delay, diesel Knocking and distanced the PCP curve from TDC. The IMEP and output torque increased by 16% as the PCP increased. As the mass flow rate of pilot fuel increased, the ignition delay decreased, causing the PCP to fall. The output torque and indicator power decreased by 17% and 70% respectively. Reducing the fuel IT at high speed, the indicator power improved and the emission results showed that the IT advancing increased the NOx and CO2 by 31% and 16% respectively, indicating improved combustion quality in the dual-fuel diesel engine.

Electric vehicles and hybrid electric vehicles are a suitable alternative for vehicles with hydrocarbons fuels to reduce pollution and fossil resources. The batteries operate as the driving force for these vehicles. One of the most critical parameters of the battery is computing the state of charge (SOC). The best range for SOC of lithium-ion battery is between 20% and 90%, and charging and discharging cycles outside of this range causes to decrease the battery life-span. Therefore, the battery SOC must be specified during the charging and discharging processes in order to the SOC to be within a safe range. In this paper, a single cell of lithium ion battery during the constant current discharge cycle with the electrochemical-thermal method has been simulated with 3D CFD in AVL FIRE software. First, numerical results are validated with experimental results of voltage and temperature. Then, the electrical potential distribution in the current collector, SOC, the lithium ion concentration in the electrodes, the temperature distribution at the battery surface, and generated heat during the discharge process at different rates are presented. Finally, a charge/discharge cycle with the variable current was simulated, and the output voltage and SOC were calculated.

The combustion processes, engine performance, fuel consumption, exhaust-gas composition, and combustion noise in the diesel engine are closely linked to appropriate mixture of air-fuel in combustion chamber. The fuel-injection parameters such as injection start point, discharge rate curve, injection time and injection pressure are defined by the quality of the mixture formation. The numerical modeling is the common method of investigation of fuel pressure and its effects on the injection quantity in the fuel system. In this study, one-dimensional common rail fuel injection system was simulated in AMEsim software. The simulation results illustrated that the higher injection pressure can lead to higher pressure fluctuations. Because of compressibility of fuel, its density increased with the increase of pressure, resulting in faster propagation of distribution in the whole high pressure tubes. The delay in closing the throat and moving the needle downwards, moreover, led to the difference between Injection time and solenoid stimulation in different pressures. Closing delay, also, increased with increasing pressure.

The scarceness of non-renewable energies, rising fossil fuels prices, as well as strict environmental regulations have forced many researchers to focus on utilizing environmentally friendly renewable energies such as biogas in internal combustion engines. Variety in raw materials and process of biogas production results in different components and percentages of various elements, including methane. These differences make it hard to control the combustion, effectively, in internal combustion engines. In this research, by means of 3D-CFD model, the effect of reformed biogas (R.BG) was investigated on the combustion characteristics, emissions and performance of a RCCI engine. Validation of the model was done on a single-cylinder compression ignition engine in conventional diesel and dual-fuel operations. The combustion model of the RCCI engine was simulated by replacing diesel with 20%, 40% and 60% of R.BG as low reactivity fuel. The results showed that by increasing the R.BG energy share with a constant equivalence ratio of 0.43, the average combustion temperature decreases to 1300 K and the maximum in-cylinder pressure increases up to 22.63%. Instead, it results in 2.3%, 7.9%, and 14.5% engine output losses, respectively. Also, the emission of NOx, against CO, is reduced by 50%. Soot and UHC emissions were found to be slightly decreased while using R.BG more than 40%.