Metin Gumus

Energy and Exergy Analyses Applied to a CI Engine Fueled with Diesel and Natural Gas

In this study, energy and exergy analysis of a direct injection compression ignition engine converted into dual fuel systems using different composition of mixed fuel formed from natural gas and diesel were performed. Effects of parameters, such as composition of mixed fuel, engine load, and speed, on various energetic and exergetic performance parameters of the engine were evaluated and compared with each other. The irreversibilities of mixed fuel and diesel were comparable at high engine speed but at low engine speed the irreversibility of mixed fuel was higher than that of diesel fuel.

Numerical Evaluation by Models of Load and Spark Timing Effects on the In-Cylinder Heat Transfer of a SI Engine

The aim of this study is to examine numerically the effects of spark timing and load parameters on the in-cylinder heat transfer of a SI engine by using experimental engine test data. For the investigation, a four-stroke, air-cooled, single-cylinder SI engine was tested at different spark timings and loads at a single engine speed of 2000 rpm. Woschni, Hohenberg, and Han models were employed to estimate the in-cylinder heat transfer coefficient in the case of different test conditions because of being favorable models on the SI engine operations. The evaluations show that the in-cylinder heat transfer characteristics of the air-cooled SI engine strongly depend on the load while they slightly depend on the spark timing.

Power and Efficiency Analysis of Brayton Cycles with Internal Irreversibility

Abstract In this article, power and efficiency analysis of irreversible Brayton cycle, which is one of the well-known heat engine cycles by the undergraduates, are carried out based on alternative criteria. Power, power density, and efficient power optimizations are also realized and the thermal efficiencies of the cycle are determined at maximum power and efficiency outputs. The efficient power is relatively new criterion and defined as the multiplication of power by efficiency. Therefore, this criterion considers not only the power output but also the cycle efficiency. Maximizing the efficient power function gives a compromise between power and efficiency. The effects of the external irreversibilities on the performances are investigated for various cycle parameters.