Muammer Ozkan

A Comparative Study on Energy and Exergy Analyses of a CI Engine Performed with Different Multiple Injection Strategies at Part Load: Effect of Injection Pressure

In this study, a four stroke four cylinder direct injection CI engine was run using three different injection pressures. In all measurements, the fuel quantity per cycle, the pre injection and main injection timing, the boost pressure and the engine speed were kept constant. The motor tests were performed under 130, 140 and 150 MPa rail pressure. During the theoretical part of the study, combustion, emission, energy and exergy analysis were made using the test results. An increase in the injection pressure increases combustion efficiency. The results show that combustion efficiency is not enough by itself, because the increase in the power need of the injection pump, decreases the thermal efficiency. The increase in the combustion temperature, increases the cooling loss and decreases the exergetic efficiency. In addition, the NOx emissions increased by 12% and soot emissions decreased 44% via increasing injection pressure by 17%. The thermal and exergetic efficiencies are found inversely proportional with injection pressure. Exergy destruction is found independent of the injection pressure and its value is obtained as ~6%.

Comparison of EGR ratios determined by four different methods for electronic re-circulation gate control

In this study, low pressure systems have been applied for exhaust gas recycling (EGR), which is applied in certain operating conditions. Induction air, exhaust gas flow, amount of exhaust gas added to the induction air, amount of carbon dioxide (CO2) in the exhaust gas, and amount of carbon dioxide in the induction air mixed with the exhaust gas, have been measured and the EGR ratio has been determined using four different calculation methods. The obtained results have been compared, and it has been noted that all the four methods have given similar results, and the deviation among them has been noted to be 1% at most. Deviations among the results have been explained. In the concluding section, a relation has been formed between the variables chosen as basic parameters, electronic re-circulation gate control, and variables utilised in EGR ratio determination methods.

Experimental study of the effect of top-ring clearance volume on unburned hydrocarbon concentrations

The clearance volume between the piston, the cylinder and the top compression ring in an internal combustion engine has a significant effect on the unburned hydrocarbon concentration. The high heat transfer from the burning mixture to the cylinder surface extinguishes the flame front, and this is the main reason for increased unburned hydrocarbon concentrations. The heat transfer between the mixture and the clearance volume surface is affected by the ratio of coolant surface to the clearance volume. In this study the effect of the ratio of the coolant surface to the clearance volume on the unburned hydrocarbon concentration was investigated using three different purpose-built pistons. A decrease of this ratio reduced the unburned hydrocarbon concentration by 40%.