A thermodynamic cycle operating at low pressure using a radial turbine
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Solution Overview
Problem
The high cost and complexity of designing and producing axial multi-stage turbines for thermodynamic cycles, such as the C3 process, make them impractical for efficient electricity generation from low-value heat streams, despite their suitability for high pressure ratios, whereas radial turbines offer a more economical and efficient alternative when optimized for specific performance parameters.
Innovation Solution
A single-stage radial turbine is employed in the C3 thermodynamic cycle, utilizing a unique design that eliminates the need for bearings on the exit side, integrates a diffuser with the absorption chamber, and controls rotational frequency to optimize pressure, allowing for efficient electricity generation at lower costs, and incorporates features like balancing holes and hydrostatic bearings to manage condensing liquids and reduce mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If axial multi-stage turbines are used to achieve high pressure ratios, then pressure ratio capability is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent changes the operating parameters by operating the radial turbine at low pressure ratios (below atmospheric pressure on the cold side) rather than high pressure ratios. This parameter change allows a simple single-stage radial turbine to achieve the required pressure differential without the complexity of multi-stage axial turbines.
Solution Approach 2:
Instead of using the conventional approach of multi-stage axial turbines for high pressure ratios, the patent inverts the approach by using a single-stage radial turbine with reversed pressure conditions (low pressure on the cold/absorption side below atmospheric pressure), achieving the same functional result with simpler equipment.
2Stress or pressure
If axial multi-stage turbines are used for high pressure ratios, then pressure ratio capability is improved, but manufacturing cost increases prohibitively
Solution Approach 1:
By changing the pressure operating parameters to low pressure ratios with sub-atmospheric pressure on the cold side, the patent enables the use of simple single-stage radial turbines that are much cheaper to manufacture than multi-stage axial turbines, while still achieving the required pressure differential for the C3 process.
Solution Approach 2:
The patent employs a simple single-stage radial turbine design that is significantly cheaper to manufacture and replace if needed, trading potential durability for substantial manufacturing cost savings, which is acceptable given the overall system economics of electricity generation from low-value heat streams.
3Device complexity
If radial turbines are used to reduce cost and complexity, then device complexity is reduced, but pressure ratio capability may be insufficient
Solution Approach 1:
The patent resolves this contradiction by changing the pressure operating parameters to low pressure ratios with the cold/absorption side operating below atmospheric pressure. This parameter change allows a simple single-stage radial turbine to achieve the functional equivalent of much higher pressure ratios that would be required with conventional atmospheric-pressure operation.
4Stress or pressure
If high pressure ratios are achieved through multi-stage turbines, then pressure ratio is improved, but turbine efficiency may decrease due to multiple stages
Solution Approach 1:
By changing to low pressure ratio operation with sub-atmospheric pressure on the cold side, the patent enables efficient single-stage radial turbine expansion, avoiding the energy losses associated with multiple stages while still achieving the required pressure differential for the thermodynamic cycle.
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
This configuration significantly reduces the cost of electricity generation, enhances turbine efficiency by 2-4 points, minimizes air leakage, and extends turbine lifespan by preventing condensation and corrosion, while using cheaper materials and eliminating the need for shaft seals and scalloping, achieving performance comparable to axial turbines.
Implementation Method 1
high pressure gas... enters the turbine and acts on blades... allowing high pressure gas to escape the bearing space towards the low pressure regime
Implementation Method 2
A labyrinth 2 reduces gas flow from the high pressure side to the top side of the turbine and the bearing space
Implementation Method 3
At least one hole 1, but typically a plurality roughly in z-direction, allows high pressure gas to escape the bearing space towards the low pressure regime
Data Source
Figure 1
AI summary
This invention concerns useful expansion machines in thermodynamic cycles operating at low pressures, i.e. below 10 bar maximum pressure. In order to be commercially competitive, any component of a thermodynamic cycle needs to operate as close as possible to maximum performance level. In an iterative process, the interplay between components including gas generator, expansion machine, heat exchangers and pressure reduction device (absorber or condenser) is optimized, resulting in configurations operating at the lowest achievable cost level. Surprisingly, it was found that a single stage radial turbine characterized by a pressure ratio of 5-10, a dimensionless speed of about 0.7 and a loading coefficient of 0.7 is the highly preferred expansion machine for the C3 thermodynamic Climeon cycle and its variations, e.g. involving CO2 gas as working fluid and amines as reversible, temporary CO2 absorbents as disclosed earlier, or other working fluids. In other words, surprisingly, the disclosed processes for energy generation allow such radial turbines to operate close to their optimum design specification and highest efficiency level. Methods to handle liquids which may condense within or inside the turbine are also disclosed, as well as methods to handle axial pressure on bearings and methods to protect lubricant in bearings.