Surface Heat Exchanger Fixed Flaps Flow Control
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Solution Overview
Problem
Surface heat exchangers in turbomachines face challenges in aerothermal performance due to excessive convergence of downstream parts, leading to pressure losses and reduced thermal exchange efficiency, especially in aircraft applications where cooling requirements are increasing.
Innovation Solution
A surface heat exchanger design featuring a support wall, a panel with inclined downstream parts and fixed flaps that create additional outlets, allowing for better control of air flow and reducing the convergence effect, thereby preventing air flow disconnection and ensuring uniform air flow speed across the heat exchanger height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the downstream wall has a convergent profile to accelerate air flow leaving the heat exchanger, then the air flow speed is improved, but the air flow becomes turbulent in a recirculation zone causing pressure losses
Solution Approach 1:
The patent divides the downstream wall into multiple segments: a first portion with a convergent profile to accelerate air flow, and a second portion with a less convergent or divergent profile to prevent turbulence. This segmentation allows each portion to perform its specific function optimally without the negative effects appearing in the other regions.
Solution Approach 2:
Different portions of the downstream wall are given different geometric profiles tailored to their specific locations and flow conditions. The first portion (closer to the heat exchanger) uses a more convergent profile for acceleration, while the second portion (further downstream) uses a gentler profile to maintain laminar flow and prevent recirculation zones.
2Loss of energy
If the convergence of the outlet wall is reduced to prevent turbulent flow, then pressure losses are reduced, but the central space of the heat exchanger is reduced penalizing heat exchanges
Solution Approach 1:
The downstream wall is segmented into multiple portions with different convergence characteristics. The first portion maintains sufficient convergence to preserve central space for heat exchange, while the second portion has reduced convergence to prevent turbulent flow and pressure losses downstream.
Solution Approach 2:
The patent extends the solution into the longitudinal dimension by creating a multi-portion downstream wall rather than a single uniform profile. This allows the wall to perform multiple functions at different locations along the flow path.
3Temperature
If the convergence of the outlet wall is increased to improve heat exchange space, then heat exchange efficiency is improved, but air flow acceleration becomes premature causing drag increase
Solution Approach 1:
The downstream wall is divided into portions with different convergence profiles. The first portion has higher convergence to maximize heat exchange space, while the second portion has lower convergence to prevent premature air flow acceleration and reduce drag.
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 enhances air flow management, reducing pressure losses and improving thermal exchange efficiency while maintaining the structural constraints of the turbomachine, thus optimizing the turbomachine's performance and fuel efficiency.
Implementation Method 1
The secondary air flow is guided along fins carried by this surface part and whose role is to increase the contact surface with the secondary air flow and to extract calories
Implementation Method 2
the upstream wall has a divergent profile making it possible to slow down the air flow entering a heat exchange space of the heat exchanger
Implementation Method 3
the downstream wall has a convergent profile making it possible to accelerate the air flow leaving the heat exchanger
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The surface heat exchanger (20) for an aircraft turbomachine (1) comprises a support wall (21), a panel (22) arranged substantially parallel to the support wall (21), partitions (23) connecting the wall (21) to the panel (22) that define between one another channels (24) in which an air flow (F1) flows and fins (25) situated in the channels (24). The panel has a central part (26) parallel to the wall (21) and a downstream part (29) that is inclined with respect to the wall (21), having an upstream end (29A) connected to the central part (26) and a downstream end (29B) that is situated at a distance (D2) from the wall (21) and delimits with the latter a main outlet (SP) of the channels (24). The downstream part (29) has fixed flaps (30i) disposed one after another so as to delimit between one another additional outlets (Sj) of the channels (24).