Radial Turbine Impeller Hub Shape for Blade Count and Throat Area
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Solution Overview
Problem
Existing radial turbine impellers face challenges in enhancing adiabatic efficiency while ensuring support stiffness and maintaining a sufficient throat area for fluid flow, as increasing blade number or thickness leads to interference and reduced efficiency.
Innovation Solution
A radial turbine impeller design featuring a hub with a conical shape and turbine blades of varying lengths, incorporating a convex part on the hub line to increase inter-blade distance and allow for appropriate fillet curvature, thereby increasing blade count without reducing throat area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of turbine blades is increased to enhance adiabatic efficiency, then the efficiency is improved, but the area of the narrowest part (throat) between the turbine blades becomes small, making it impossible for the fluid to flow with a necessary flow rate
Solution Approach 1:
The turbine blades are divided into two types: first turbine blades (long blades) and second turbine blades (short blades or splitter blades). The short blades are inserted between the long blades at the inlet side where the load is large, while the long blades extend to the outlet side where the load is small. This segmentation allows increasing the number of blades for efficiency without blocking the throat area for fluid flow.
Solution Approach 2:
Different blade lengths are used at different axial positions: short blades are used at the inlet side (leading edge part) where load is large and blade strength is critical, while long blades are used at the outlet side (trailing edge part) where load is small but throat area is critical for flow rate. This local differentiation resolves the contradiction between efficiency and flow rate.
2Strength
If the thickness of each turbine blade is increased to ensure sufficient strength under high load, then the strength is improved, but the area of the narrowest part (throat) between the turbine blades becomes small, reducing the maximum flow rate
Solution Approach 1:
The turbine blade system is segmented into long blades and short blades. The short blades provide structural strength at the inlet where load is high, while the long blades maintain adequate throat area at the outlet where flow rate is critical. This segmentation allows each blade type to optimize for its specific functional requirement.
3Stability of the object's composition
If the radius of curvature of fillets connecting the turbine blade side surface and hub surface is increased to enhance support stiffness, then the support stiffness is improved, but the fillets adjacent to each other in the rotational direction interfere (overlap) with each other, making it difficult to increase the number of turbine blades
Solution Approach 1:
By segmenting the blades into short and long types, the circumferential spacing between adjacent blades can be optimized. The short blades allow for larger fillet radii without interference because they occupy less circumferential space, enabling both high support stiffness and increased blade count.
4Device complexity
If the length of short blades is increased to further increase the number of turbine blades, then the blade count is increased, but fillets with appropriate radius of curvature cannot be formed due to interference, making it difficult to improve efficiency
Solution Approach 1:
The short blades are positioned specifically at the inlet side where they provide necessary blade count for efficiency while maintaining adequate spacing for proper fillet formation. The long blades at the outlet side ensure adequate throat area. This local differentiation of blade functions allows achieving both high blade count and proper fillet geometry.
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 design enhances adiabatic efficiency by increasing blade count while maintaining support stiffness and flow rate, preventing efficiency loss.
Implementation Method 1
The compressed fluid expands in volume and the flow velocity thereof increases when passing the turbine nozzle
Implementation Method 2
the compressed fluid supplied to the turbine impeller rotates the turbine impeller at a high speed
Data Source
AI summary
A radial turbine impeller includes a hub having a substantially conical shape and multiple turbine blades provided on an outer peripheral surface of the hub at intervals in a rotational direction. In a meridian cross section, a hub line formed by the outer peripheral surface of the hub has a diameter that monotonically decreases from an upstream end on a radially outer side to a downstream end on a radially inner side, and includes a convex part that is convex toward a radially outer side.