Bottoming cycle power system
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Solution Overview
Problem
Inverted Brayton bottoming cycle power systems face inefficiencies due to high work requirements for compressing exhaust gas, primarily because of the high volume and mass of water vapor and low exhaust gas pressure, which limits the recovery of useful work from internal combustion engines.
Innovation Solution
A two-stage cooling process using an absorption chiller system with a generator and evaporator section to condense water vapor and reduce the volume and mass of exhaust gas before compression, enhancing the efficiency of the bottoming cycle by minimizing the work needed for compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If exhaust gas is cooled using conventional cooling systems, then the volume of exhaust gas is reduced, but a significant amount of energy is consumed by pumps and other energy consuming devices
Solution Approach 1:
The exhaust gas itself serves as the cooling medium through the absorption chiller system. The water vapor within the exhaust gas undergoes phase change from vapor to liquid, absorbing heat from the exhaust gas in the process, thereby cooling the exhaust gas without requiring external energy-consuming pumps or cooling devices.
Solution Approach 2:
The absorption chiller system utilizes the phase transition of water vapor from gaseous state to liquid state. This phase change occurs in the absorption chamber where refrigerant absorbs water vapor from the cooled exhaust gas, causing the water vapor to condense and release latent heat, which is then removed from the system, achieving efficient cooling.
2Quantity of substance
If water vapor is removed from exhaust gas, then the mass and volume of exhaust gas are reduced, but the complexity of the system increases
Solution Approach 1:
The absorption chiller system combines multiple functions into a single integrated unit: cooling the exhaust gas, removing water vapor through condensation, and reducing the volume of exhaust gas before compression. This merging of functions achieves multiple objectives simultaneously without requiring separate complex systems for each function.
Solution Approach 2:
The absorption chiller acts as an intermediary device between the exhaust gas and the compressor. It conditions the exhaust gas by cooling and dehumidifying it before compression, using the absorption chamber as a mediator where refrigerant interacts with water vapor to facilitate its removal from the exhaust stream.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The two-stage cooling process significantly reduces the volume and mass of exhaust gas, thereby decreasing the compressor's work load, increasing the overall efficiency of the bottoming cycle power system and enhancing net power generation.
Implementation Method 1
The generator section has a first heat exchanger to receive the flow of exhaust gas from the expander. The generator section is operable to remove heat from the exhaust gas as the exhaust gas passes through the first heat exchanger.
Implementation Method 2
The evaporator section has a second heat exchanger to receive the flow of exhaust gas from the generator section. The evaporator section is operable to remove heat from the exhaust gas as the exhaust gas passes through the second heat exchanger.
Implementation Method 3
The two-stage cooling process may condense out water vapor from the flow of exhaust gas to significantly reduce the volume and mass of the exhaust gas.
Implementation Method 4
The compressor is operable to compress the exhaust gas after the exhaust gas has passed through the second heat exchanger when the expander crankshaft is rotated by the expander.
Data Source
AI summary
A bottoming cycle power system includes an expander disposed on a crankshaft. The expander being operable to receive a flow of exhaust gas from a combustion process and to rotate the crankshaft as the exhaust gas passes through. An absorption chiller system has a generator section having a first heat exchanger to receive the flow of exhaust gas from the expander and to remove heat from the exhaust gas after the exhaust gas has passed through the expander. An evaporator section has a second heat exchanger to receive the flow of exhaust gas from the generator section and to remove heat from the exhaust gas after the exhaust gas has passed through the generator section. A compressor is disposed on the crankshaft and connected to the flow of exhaust gas. The compressor is operable to compress the exhaust gas after the exhaust gas has passed through the second heat exchanger.