Search Results

Diesel-ethanol dual-fuel combustion has been recognized as an effective alternative to improve efficiency, reduce emissions and substitute part of the fossil fuel. In this regard, the need to improve engine efficiency has continued to drive studies through the understanding of the engine’s thermodynamics. However, the energy analysis based on the first law of thermodynamics does not identify and quantify the system inefficiencies, being insufficient to reveal the best efficiencies of any system. Therefore, the exergy analysis based on the second law of thermodynamics is required to understand and improve the actual efficiencies of the entire system and has higher research significance. Exergy analysis in recent years has been widely used in various thermal systems.

Universal concerns about harmful emissions, strict emission regulations and global warming have motivated research of engines operating with alternative combustion concepts. Low temperature combustion (LTC) is an advanced concept for internal combustion engines, which will be able to replace the conventional combustion modes and have the advantage of using renewable as well as traditional fuels. In this regard, LTC has attracted global attention in recent years, especially the homogeneous charge compression ignition (HCCI) mode. This combustion mode is different from spark ignition and compression ignition, because there is no flame propagation or diffusive flame. Instead, HCCI combustion is governed by chemical kinetics. HCCI engines use highly diluted homogeneous charge and when the mixture reaches chemical activation, auto ignition takes place simultaneously in multiple spots.

In this work an analysis of biodiesel fuel use in stationary engines was made through performance tests in dynamometer. In the tests, the characteristics of torque, power, specific consumption and smoke index were determined for two cylinders diesel engines. Initially, the engines were tested working with diesel, and then the tests were done with the engines working with diesel and biodiesel mixtures specified by B25, B50, B75 and B100. The biodiesel used on the tests was of soy. The results show that the use of biodiesel is feasible, but with loss of power and torque when compared to pure diesel. For pure biodiesel (B100) at 3,000 rpm the power decrease was 4.03% while for B50 the decrease was 0.94%. The results for torque showed a similar behavior with a decrease of 4.08% for B100 and 0.93% for B50 at 3,000 rpm. The specific consumption increased, as expected, 12.25% for B100 and 5.44% for B50.