Rail Vehicle Running Gear Frame Protrusion for Drag Reduction
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Solution Overview
Problem
High-speed rail vehicles experience increased drag and sound emissions due to airflow detachment from vehicle components, leading to a widening shear layer and turbulence, which induces further drag and noise.
Innovation Solution
The transverse beam lower chord of the running gear frame protrudes forward and rearward beyond the web elements, creating a boundary layer that allows earlier re-attachment of airflow, delaying its detachment and reducing the expansion of the shear layer, thereby minimizing drag and sound emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the transverse beam lower chord protrudes forward and/or rearward beyond the web elements, then the air flow re-attaches earlier and detaches later, reducing shear layer expansion, but the structural complexity of the transverse beam increases
Solution Approach 1:
The transverse beam lower chord is segmented into multiple sections with different longitudinal positions. Specifically, it includes a front section that protrudes forward beyond the front web element and a rear section that protrudes rearward beyond the rear web element, while the middle section remains aligned with the web elements. This segmentation allows the beam to create favorable flow conditions at critical locations without requiring complete redesign of the entire beam structure.
Solution Approach 2:
The protrusion of the transverse beam lower chord is applied locally at specific positions (front and rear sections) rather than uniformly across the entire beam. This local modification creates boundary layers that promote flow re-attachment and delay detachment at critical locations, reducing shear layer expansion and associated drag and noise, while minimizing the overall structural complexity increase.
2Object-affected harmful factors
If the transverse beam lower cord protrudes beyond the web elements by at least 10% of the web element distance, then the shear layer expansion is reduced, but the manufacturing complexity increases
Solution Approach 1:
The invention specifies a quantitative parameter for the protrusion distance (at least 10% of the web element distance, preferably 15-40%) that optimizes the balance between aerodynamic performance and manufacturability. This parameter-based approach provides clear design guidance that simplifies the manufacturing process by establishing standardizable dimensions rather than requiring complex custom calculations for each application.
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 design reduces the expansion of the shear layer, leading to decreased drag and sound emissions by ensuring airflow re-attachment and later detachment over the running gear, resulting in improved aerodynamic performance.
Implementation Method 1
The protrusion of transverse beam lower chord formed in this manner has the advantage over conventional designs, in which the transverse beam lower cord at best protrudes only slightly beyond the web elements, that the incident air flow starting from a leading running gear component (for example a drive motor, gearbox, wheelset or similar) can re-attach earlier at the transverse beam lower chord by forming a further boundary layer
Implementation Method 2
the incident air flow starting from a leading running gear component (for example a drive motor, gearbox, wheelset or similar) can re-attach earlier at the transverse beam lower chord by forming a further boundary layer, while in the region of the trailing protrusion a later detachment of the low drag air flow is achieved
Implementation Method 3
in the region of the trailing protrusion a later detachment of the low drag air flow is achieved. As a result of the earlier re-attachment and later detachment of the air flow, in the area of the transverse beam, a shear layer forms only behind the transverse beam (in the direction of travel)
Implementation Method 4
If this shear layer hits running gear components such as for example the underside of a drive motor or a transverse beam of a running gear frame, further turbulence is induced which leads to an increase in drag and sound emissions
Implementation Method 5
further turbulence is induced which leads to an increase in drag and sound emissions
Data Source
AI summary
A running gear frame for a rail vehicle includes a central transverse beam, and two longitudinal beams connected together in a frame transverse direction via the transverse beam, wherein the transverse beam has at least a front web element, a rear web element and a transverse beam lower chord. The web elements run between the longitudinal beams in the frame transverse direction and in a frame height direction and are connected therewith and are arranged spaced apart in a frame longitudinal direction. The transverse beam lower chord extends on an underside of the transverse beam between the longitudinal beams and is connected with the web elements. Furthermore, the transverse beam lower chord extends beyond the front web element and/or the rear web element by at least 10% of the web element distance.