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

The transition to low-carbon fuels introduces new challenges for the design of energy systems based on internal combustion engines. This paper addresses the effects of ammonia as one of the prime fuels for highly efficient two-stroke engines, e.g., based on MAN high-pressure injection technology. Even if these prime movers can maintain a high effective efficiency over a wide load range, the thermodynamic features of the ammonia combustion have a strong impact on the waste heat pattern. The analysis indicates that the lower adiabatic flame temperature and the chemical composition of the exhaust gases reduce the exhaust temperature, while variations in the specific heat capacity of the exhaust mixture reduce the exergy. This phenomenon is directly related to a reduced potential of working fluid generation in waste heat recovery (WHR) systems. The paper concludes that to maintain high overall plant energy efficiency, advanced technologies, such as organic Rankine cycles (ORC), have to be applied to compensate for the loss of the thermal potential, especially at off-design load conditions.

The escalating global demand for sustainable and efficient energy solutions has spurred increased exploration into waste heat recovery technologies. Among these, the integration of Organic Rankine Cycle (ORC) systems with diverse industrial processes stands out as a promising avenue for effectively harnessing low-grade waste heat. This integration not only holds the potential to significantly improve overall energy efficiency but also plays a crucial role in mitigating the environmental impact associated with industrial operations.
Recognizing this potential, the primary focus of this research lies in the meticulous design, optimization, and performance evaluation of a modular Flue Gas Waste Heat Exchanger (FGWHE). This modular FGWHE is strategically crafted to seamlessly integrate with ORC systems across a spectrum of applications, offering versatility and adaptability to varying industrial settings. This paper further extends the exploration of this research through a comprehensive presentation of Computational Fluid Dynamics (CFD) simulations. These simulations delve into the intricacies of a specifically designed modular FGWHE tailored for Organic Rankine Cycle systems. Through detailed CFD analyses, the performance characteristics, heat transfer efficiencies, and fluid dynamics within the modular FGWHE are rigorously examined. The simulation outcomes provide valuable insights into the thermal behavior and overall effectiveness of the modular FGWHE under various operating conditions.

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.