Research of Organic Rankine Cycle Energy Characteristics at Operating Modes of Marine Diesel Engine

Abstract

The publication examines one of the most effective ways to decarbonize marine transport, specifically the secondary heat sources utilization in the cogeneration cycle of the main engines. The research focuses on the optimization of Organic Rankine Cycle (ORC) performance parameters by combining them with the exhaust energy potential of a medium speed four-stroke main diesel engine in ISO8178 (E3) load cycle modes. Significant advantages were not found between the evaluated Wet-, Isentropic-, and Dry-type liquids (R134a, R141b, R142b, R245fa, Isopentane) in terms of ORC energy performance with a 10% difference. The use of a variable geometry turbogenerator turbine with Dry-type (R134a) working fluid is characterized by the highest ORC energy efficiency up to 15% and an increase in power plant (including turbogenerator generated mechanical) by 6.2%. For a fixed geometry turbine, a rational control strategy of the working fluid flow (Gd.sk − πT) is determined by the priorities of the power plant in certain load modes. The influence of the overboard water temperature on the ORC energy indicators does not exceed ±1%; however, it influences the thermodynamic saturation parameters of the working fluid condensation and, in connection with that, the fluid selection.

Complex Use of the Main Marine Diesel Engine High- and Low-Temperature Waste Heat in the Organic Rankine Cycle

“…Additionally, it involved studying the principles of heat regeneration and power turbine regulation in the WHR cycle, with a rational adaptation to ship propulsion plant, as well as experimental numerical variation studies. These findings are presented in the authors' publication [53].…”

“…Comparative studies were conducted based on the use of this secondary heat source to assess different types of working fluids, identifying a more rational choice based on ship conditions. The research also aimed to evaluate energy efficiency and performance, considering different power turbine designs and control aspects [53]. Building on the resolved aspects of rational ORC utilization, the second stage of the research, presented in the author's publication, is dedicated to comprehensive studies on different combinations of secondary heat sources (exhaust gases, internal cylinder cooling circuit, and scavenge air cooler) for ORC implementation.…”

“…Based on the previously conducted research by the authors [53], Freon R134a was chosen as the working fluid, which demonstrated the highest energy efficiency among the tested wet, dry, and isentropic working fluids (Freon products R134a, R141b, R142b, R245fa, and Isopentane). The selection of Freon R134a refrigerant among all assessed working materials is based on the operational reliability of the cycle's technological system concerning the fluid's saturation pressure and temperature [53]. Also, the provisions of EU and IMO regulatory regulations on the use of Freon products in refrigeration technology and conditioning systems were taken into account.…”

“…Based on the results of the initial research stage [53], for the operation of the KC, a "wet" type working fluid, Freon R134a, was chosen, and its properties are provided in Table 1.…”

Thermo-economic optimization of an ORC system for a dual-fuel marine engine

“…According to the results, the pay-back period of the system is calculated as 5.2 years. Lebedevas and C ˇepaitis 13 conducted an optimization study for an exhaust gas-driven ORC WHR system of a marine four-stroke diesel engine. They stated that variable turbine geometry with R134a shows the best thermodynamic performance.…”