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It is possible to increase the heat conduction in the engine by mixing nano-sized metal particles into the liquid coolant. In this study, the temperature changes in the cooling system of the engine operated at 1000, 2000, 3000, and 4000 rpm were investigated by adding 0.1% and 0.2% SiO2, TiO2, Al2O3 nanofluids to the base coolant in the engine cooling system of a vehicle. In addition, the changes in CO2, HC, CO, NOx, and O2 exhaust emissions at these speeds were also investigated. It was observed that the heat conduction increased as the ratio of nanofluids added to the base fluid increased, but the heat conduction decreased at 3000 and 4000 rpm. The positive heat conduction effect seen in all nanofluid mixtures studied for lowtemperature values was not observed when the coolant temperature values increased with the increase in engine speed. Therefore, it was determined that nanofluid mixtures did not improve heat conduction under all conditions. With the increase in the particle ratio, it has observed that the engine coolant remained at lower temperature values, resulting in an improvement in heat conduction. For CO2, HC, CO, and O2 emissions, there were no significant differences in the exhaust emission values compared to the base fluid. It has been determined that there are decreases of approximately 28%, 27%, 25%, and 21%, respectively, in NOx emission values for different engine speeds. In general, the best results in temperature and emission measurements were obtained with 0.2% SiO2 nanofluid. [ABSTRACT FROM AUTHOR]

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Cooling of internal combustion engines are necessary to prevent reaching high temperatures that would damage the engine block. For this reason, studies on more efficient cooling of internal combustion engines are frequently encountered in the literature. This becomes even more important if the internal combustion engine is supercharged. These engines are mostly cooled by liquid fluids, while some are cooled by air. Considering this point, in this theoretical study, effect of using of water, water + Al2O3, water + CuO, ethylene glycol, water + ethylene glycol, water + ethylene glycol + Al2O3 or water + ethylene glycol + CuO in the cooling system of a diesel engine on the amount of heat removed is investigated, respectively. In daily life, considering that the freezing temperature of water is relatively higher than the freezing temperature of ethylene glycol, water + ethylene glycol mixture is used instead of single water in engine cooling systems. Considering this situation, in this study, usage of water-ethylene glycol mixture and usage of single water or usage of various nano-fluids are thermally compared. For this aim, primarily, the effect of nano-particle volumetric ratio in the mixtures on the thermophysical properties such as density, specific heat, and thermal conductivity of the related nano-fluid is investigated. Then, using these new thermophysical properties, the effect of fluid or nano-fluid on the amount of heat to be removed from the engine block is investigated. According to this; among the examined fluids, the fluid with the highest density is 47.5% water + 47.5% ethylene glycol + 5% CuO, while water has the highest specific heat. The highest value among the thermal conductivity values that are calculated using various relations belongs to 49.75% water + 49.75% ethylene glycol + 0.5% CuO fluid according to the Wasp Model. The fluid with the highest mass flow rate is 47.5% water + 47.5% ethylene glycol + 5% CuO fluid which has the highest density. According to these data, the usage of nano-fluids provided an increase nearly as 15% in the amount of heat removed from the engine block thanks to increasing in density and specific heat. [ABSTRACT FROM AUTHOR]

In this study, using the finite-time thermodynamics method, a simulation model has been created for Otto-cycle engines. In the model, it has been assumed that there are irreversibilities, heat, combustion, and friction losses, and also that the specific heat changes depending on the temperature, the cycle initial temperature changes depending on the residual gas temperature, and the working fluid is composed of the fuel-air-residual gas mixture. The effects of compression ratio, equivalence ratio, and stroke/bore ratio on engine performance were examined. Thermal efficiency, specific fuel consumption, specific fuel cost, and power density are used for performance analysis. Performance loss factors were used for engine heat balance. The characteristics of a single-cylinder spark-ignition engine have been used as a reference in the model. As a result of the numerical study, it was observed that when the volumetric efficiency decreased by 10% in LPG use, the power density decreased by 12%. Although the specific fuel consumption of LPG is higher than gasoline, the specific fuel cost of LPG is considerably lower than gasoline due to the LPG/gasoline price ratio. The loss of performance decrease as the compression ratio increases and the stroke/bore ratio decreases. Also, performance losses increase when the equivalence ratio is greater than 1. It is seen that LPG performance can be eliminated by increasing the volumetric efficiency or increasing the compression ratio. When the LPG/gasoline price ratio is 0.54, it is determined that the engine running on LPG is 24% more economical compared to working with gasoline. When the LPG/gasoline price ratio is 0.67, it has been observed that LPG has no economic advantage. Significant results have been obtained especially for engine designers. [ABSTRACT FROM AUTHOR]

In this study, a single cylinder β-type Stirling engine with the swept volume of 192 cc was manufactured and performance tests were conducted. Experiments were performed at 800, 900 and 1000°C heater temperatures and I. 1 .5. 2, 2.5 and 3 bar charge pressures. Air was used as the working fluid. Torque and power variations were obtained for different engine speeds, heater temperatures and charge pressures. Maximum output-power was obtained as 14 W at 344 rpm engine speed, at the heater temperature of 1000°C and 2.5 bar charge pressure. [ABSTRACT FROM AUTHOR]