International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The article presents a numerical analysis of energy balance of an automotive diesel engine and exergy analysis of exhaust gas and cooling systems. A model of the engine was built in advanced simulation code AVL Boost. In order to validate the model a comparison between estimated and real engine effective power was conducted at full load. Energy balance revealed a maximum engine efficiency of 42.1% at full load and 2000rpm. The highest quantity of lost energy contains the exhaust gas. The maximum estimated exhaust gas enthalpy is 108kW at 4000rpm. At the same operating point the cooling enthalpy more than twice lower – 40.2kW. At the engine speed lower than 2000rpm the lost energy in exhaust gas and cooling system has the same quantity. The exergy analysis revealed that waste heat recovery potential in exhaust gas is much higher than cooling system. The results obtained in this study will be further used in a Rankine-Hirn waste heat recovery system development due to increase overall engine efficiency.

This paper presents numerical analysis of waste heat recovery from engine exhaust gases by means of Rankine cycle and Organic Rankine cycle. Both technologies are widely studied in combustion engines but there are still not solid statements which should be chosen.

The heat source in this study is the exhaust system of a modern diesel engine, developed for passenger car. Firstly, the engine was experimentally studied at stationary operating mode. Thus, exhaust gas parameters such as: mass flow rate, temperature and enthalpy were obtained at seventeen operating points which correspond to real operating mode of vehicle in NEDC. A simulation model of waste heat recovery system was developed. Based on that model, a numerical code was created in Python as CoolProp open-source platform was used to determine working fluid parameters. Lastly, Rankine cycle and Organic Rankine Cycle output power and efficiency were studied. The results revealed that Organic Rankine cycle using R245fa as working fluid provides better efficiency than steam Rankine cycle. Maximum recovered power was estimated to be 1.69kW while for the steam Rankine cycle it was 1.43kW.

In this paper an experimental study of exhaust gas parameters of a modern diesel engine is presented. The engine under study is developed for passenger car. It was used a flexible engine management system based on National Instruments real-time controller and LabVIEW code. However, basic settings of the engine calibration values were used over the test. The engine was tested at seventeen operating points which correspond to real operating mode in NEDC of the vehicle. In order to define the engine speed and load a vehicle driving model was used. Finally, exhaust mass flow and temperature were studied as well as exhaust enthalpy was estimated. The results revealed that waste heat recovery system can be applied in order to reduce fuel consumption in NEDC.

The escalating fuel price and carbon dioxide legislation have renewed the interest in the methods of increasing engine thermal efficiency beyond in-cylinder techniques. The aim of this study is to review the latest technologies of waste heat recovery of exhaust gases in internal combustion engines. These include turbocompounding systems, thermoelectric generators, thermoacoustic systems and closed-loop thermodynamic cycles based on Stirling, Ericsson and Rankine cycles. A number of studies revealed that Rankine cycle is the most perspective waste heat recovery system due to its higher thermal efficiency. Finally, the components of the Rankine cycle (working fluid, evaporator and expander) were studied in detail.