Organic Rankine Cycle systems represent a promising solution for the recovery of waste heat in Internal Combustion Engines. In such systems a great amount of thermal energy is wasted at different temperature levels in the environment which can be further recovered to increase the overall efficiency. The main focus of this thesis was the characterization of a sliding vane expander thought for an ORC-based power unit recovering heat from the exhaust gases of a Diesel Engine. The potentialities of a novel intake system consisting in an additional adduction port properly located on the stator have been assessed, analyzing the performances through experimental and numerical activities. The conducted investigation allowed the definition of the advantages and drawbacks of the proposed solution, giving at the same time a thorough description of the fluid-dynamic phenomena characterizing this kind of devices. The contents of the manuscripts have been divided in the following way: In chapter 1 an introduction on global warming issues has been presented. A special attention has been given to the on the road transport sector focusing on regulations and potential improvement of Internal Combustion Engines through innovative technologies. Chapter 2 is a thorough review of most relevant studies on Organic Rankine cycles. Main aspects related to working fluid selection criteria, plant layout and components have been investigated. Special attention has been given to evaporators and expanders technologies. Chapter 3 describes the layout used for the experimental activities. Characteristics of the ORC unit, the engine and measurement instruments have been detailed. Chapter 4 reports the results of the experimental activity conducted with the original expander and after the modification introduced for the investigation on the novel intake system. For both options, efficiencies, indicated and mechanical power have been compared. Chapter 5 describes the numerical model calibrated with the dataset obtained through the experimental campaigns. This instrument has been used to investigate source of losses and analyze the leakage paths contributing to the volumetric efficiency reduction. In Chapter 6 the numerical model has been used as a design software platform. A new design methodology is proposed for sliding vane rotary expanders with an auxiliary port, showing potential advantages related to the possible downsizing of the machine. The results of this work show that sliding vane expander performances can be increased through the modifications of the intake of the device. This solution can improve also the reliability and range of operation of the machine, lowering the unit maximum pressure and allowing to elaborate a greater working fluid mass flowrate. An additional advantage can be obtained initially designing a sliding vane expander with a dual port. In this way a sensible downsizing of the device can be achieved reducing weight, size and volume of the machine.

Thermal energy recovery via ORC-based power units. Experimental and numerical analyses using sliding vane rotary expanders and novel technological advancements / DI BARTOLOMEO, Marco. - (2021 Jul 28).

Thermal energy recovery via ORC-based power units. Experimental and numerical analyses using sliding vane rotary expanders and novel technological advancements

DI BARTOLOMEO, MARCO
2021-07-28T00:00:00+02:00

Abstract

Organic Rankine Cycle systems represent a promising solution for the recovery of waste heat in Internal Combustion Engines. In such systems a great amount of thermal energy is wasted at different temperature levels in the environment which can be further recovered to increase the overall efficiency. The main focus of this thesis was the characterization of a sliding vane expander thought for an ORC-based power unit recovering heat from the exhaust gases of a Diesel Engine. The potentialities of a novel intake system consisting in an additional adduction port properly located on the stator have been assessed, analyzing the performances through experimental and numerical activities. The conducted investigation allowed the definition of the advantages and drawbacks of the proposed solution, giving at the same time a thorough description of the fluid-dynamic phenomena characterizing this kind of devices. The contents of the manuscripts have been divided in the following way: In chapter 1 an introduction on global warming issues has been presented. A special attention has been given to the on the road transport sector focusing on regulations and potential improvement of Internal Combustion Engines through innovative technologies. Chapter 2 is a thorough review of most relevant studies on Organic Rankine cycles. Main aspects related to working fluid selection criteria, plant layout and components have been investigated. Special attention has been given to evaporators and expanders technologies. Chapter 3 describes the layout used for the experimental activities. Characteristics of the ORC unit, the engine and measurement instruments have been detailed. Chapter 4 reports the results of the experimental activity conducted with the original expander and after the modification introduced for the investigation on the novel intake system. For both options, efficiencies, indicated and mechanical power have been compared. Chapter 5 describes the numerical model calibrated with the dataset obtained through the experimental campaigns. This instrument has been used to investigate source of losses and analyze the leakage paths contributing to the volumetric efficiency reduction. In Chapter 6 the numerical model has been used as a design software platform. A new design methodology is proposed for sliding vane rotary expanders with an auxiliary port, showing potential advantages related to the possible downsizing of the machine. The results of this work show that sliding vane expander performances can be increased through the modifications of the intake of the device. This solution can improve also the reliability and range of operation of the machine, lowering the unit maximum pressure and allowing to elaborate a greater working fluid mass flowrate. An additional advantage can be obtained initially designing a sliding vane expander with a dual port. In this way a sensible downsizing of the device can be achieved reducing weight, size and volume of the machine.
Thermal energy recovery via ORC-based power units. Experimental and numerical analyses using sliding vane rotary expanders and novel technological advancements / DI BARTOLOMEO, Marco. - (2021 Jul 28).
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/169675
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