Axial Flow Progressive Cavity Gas Generator Design
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Solution Overview
Problem
Current gas generators in turbomachinery, such as axial flow positive displacement engines, face challenges in achieving lightweight, high efficiency, and reduced part count to minimize manufacturing, installation, refurbishment, and replacement costs while maintaining high specific energy exhaust and mass flow rates.
Innovation Solution
The design incorporates inner and outer bodies with intermeshed helical blades having distinct twist slopes in sections, allowing for constant volume combustion and efficient energy extraction, with the inner body rotatable within the outer body, and both bodies being rotatable in the same direction at different speeds to achieve mechanical or dynamic trapping of air charges for compression and expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional axial flow gas generators are designed to achieve high mass flow rate and continuous fluid flow, then productivity and energy efficiency are improved, but device complexity and part count increase
Solution Approach 1:
The patent combines the compressor and turbine functions into a single integrated axial flow progressive cavity mechanism. The inner body with helical blades serves dual purposes: compressing air in the first section and expanding gases in the second section, eliminating the need for separate compressor and turbine assemblies. This merging reduces part count while maintaining high mass flow rate capability.
Solution Approach 2:
The inner body structure performs multiple functions: it acts as both a compressor element and a turbine element, provides structural support for the intermeshed helical blades, and creates the progressive cavity pattern necessary for continuous fluid flow. This multi-functionality reduces the overall number of components required in the gas generator system.
2Reliability
If the number of helical blade turns is increased to mechanically trap charges of air, then compression efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The helical blades are designed with different local characteristics in different sections: the first section has sufficient turns for mechanical trapping of air charges with specific pitch and twist rates optimized for compression, while the second section has different geometric parameters optimized for expansion. This local differentiation allows each section to perform its function efficiently without requiring the entire structure to be overly complex.
Solution Approach 2:
The design uses dynamic trapping of air charges through the rotating helical blades, where the blades create moving cavities that capture and transport air charges through the compression section. This dynamic approach allows effective compression with fewer blade turns compared to static trapping mechanisms, reducing manufacturing complexity.
3Loss of energy
If constant volume combustion is implemented in the second section, then thermal efficiency is improved, but device complexity increases
Solution Approach 1:
The combustion chamber is integrated directly into the second section of the axial flow progressive cavity structure. The same inner body and helical blades that create the progressive cavity for expansion also define the combustion chamber geometry. This integration eliminates the need for separate combustion chamber components while enabling constant volume combustion through the controlled geometry of the expanding cavity.
Solution Approach 2:
The design uses parameter changes in the helical blade geometry between sections to enable different thermodynamic processes: the first section parameters are optimized for compression, while the second section parameters (including blade pitch, twist rate, and cavity volume) are optimized for constant volume combustion and expansion. These parameter transitions are achieved through continuous geometric variations in the helical blade design.
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 enhances net work output and thermal efficiency, enabling a smaller engine size for the same power requirement, making it suitable for weight and size-sensitive applications.
Implementation Method 1
The inner and outer bodies have intermeshed inner and outer helical blades wound about inner and outer axes respectively... The helical blades in the first section have sufficient number of turns to trap charges of air in the first section during the generator's operation
Implementation Method 2
A combustion section extends axially downstream from the end of the first section through at least a portion of the second section. Constant volume combustion occurs in the second section.
Implementation Method 3
The inner body is rotatable about the inner axis within the outer body. The outer body is rotatable about the outer axis... enabling a smaller engine size for the same power requirement
Data Source
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AI summary
An axial flow positive displacement engine (8) has an inlet (20) axially spaced apart and upstream from an outlet (22). Inner and outer bodies (12, 14) have offset inner and outer axes (16, 18) extend from the inlet (20) to the outlet (22) through first, second, and third sections (24, 26, 28) of a core assembly (15) in serial downstream flow relationship. At least one of the bodies is rotatable about its axis. The inner and outer bodies (12, 14) have intermeshed inner and outer helical blades (17, 27) wound about the inner and outer axes (16, 18) respectively. The inner and outer helical blades (17, 27) extend radially outwardly and inwardly respectively. The helical blades have first, second; and third twist slopes (34, 36, 38) in the first, second, and third sections (24, 26, 28) respectively. The first twist slopes (34) are less than the second twist slopes (36) and the third twist slopes (38) are less than the second twist slopes (36). A combustor section (40) extends axially downstream through at least a portion of the second section (26).