Bottoming cycle power system
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Solution Overview
Problem
Inverted Brayton bottoming cycle power systems face challenges in efficiently reducing the volume and mass of exhaust gas flow before compression, leading to high compressor work requirements due to the presence of water vapor and energy consumption by cooling systems.
Innovation Solution
A two-stage cooling process using an absorption chiller system with a generator and evaporator section, which removes heat and condenses water vapor from the exhaust gas, reducing its volume and mass before compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional cooling systems are used to reduce exhaust gas volume before compression, 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 cooling process is divided into two distinct stages: a primary cooling stage using a conventional heat exchanger, and a secondary cooling stage using an ejector-based cooling system. This segmentation allows each stage to operate optimally for its specific function, with the ejector handling the most energy-intensive volume reduction without requiring external power input
Solution Approach 2:
The patent replaces mechanically-driven cooling systems (requiring pumps and motors) with an ejector-based cooling system that uses fluid dynamics and pressure differentials to achieve cooling. The ejector uses the kinetic energy of a motive fluid (refrigerant) to create a vacuum and draw in exhaust gas, eliminating the need for mechanical pumps and significantly reducing energy consumption
2Power
If the exhaust gas is cooled to reduce volume before compression, then the compressor work is reduced, but the cooling systems consume significant energy
Solution Approach 1:
The ejector-based cooling system replaces mechanical compression and pumping systems with a fluid dynamic system. The ejector uses a high-velocity motive fluid to create a low-pressure zone that draws in and cools the exhaust gas through heat exchange, eliminating the need for energy-consuming mechanical components while still achieving the necessary volume reduction to minimize compressor work
Solution Approach 2:
The system utilizes phase transitions of the refrigerant fluid within the ejector. The refrigerant undergoes expansion and phase change from liquid to vapor, absorbing heat from the exhaust gas in the process. This phase transition mechanism provides efficient cooling without requiring external energy input, as the heat absorption is inherent to the thermodynamic cycle of the refrigerant
3Quantity of substance
If water vapor is present in the exhaust gas, then the exhaust gas contains significant energy, but the water vapor has high specific volume and mass causing unwanted burden on compression work
Solution Approach 1:
The ejector system extracts and separates water vapor from the exhaust gas stream during the cooling process. As the exhaust gas is cooled in the ejector, water vapor condenses and is separated from the gas phase, effectively removing it from the compression burden. This extraction of water vapor reduces the specific volume and mass that the compressor must handle, decreasing the required compression work
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
Significantly reduces the work required by the compressor, enhancing the overall efficiency of the bottoming cycle power system by minimizing energy consumption and condensing water vapor, thereby increasing net power generation.
Implementation Method 1
The generator section removes heat from the flow of exhaust gas and uses it to further cool the same flow of exhaust gas
Implementation Method 2
The evaporator section is operable to remove heat from the exhaust gas as the exhaust gas passes through the second heat exchanger
Data Source
Figure 1
Figure 2
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.