Heated Turbine Outlet Diffuser for Aircraft Ice Prevention
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Solution Overview
Problem
Conventional air cycle machines in aircraft environmental control systems face ice formation issues at the turbine outlet, leading to reduced aerodynamic performance and thermodynamic losses due to suboptimal ice protection methods that either compromise turbine geometry or introduce unnecessary heat, resulting in complex and costly solutions.
Innovation Solution
A turbine outlet heated diffuser with an annular cavity positioned downstream of the turbine, receiving heated compressor discharge air to prevent ice formation on the diffuser walls, which is then directed into the turbine inlet plenum, maintaining optimal geometry and minimizing thermodynamic losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the turbine inlet plenum is extended to incorporate the diffuser structure and use turbine inlet air for heating, then ice formation is prevented, but turbine aerodynamic performance is reduced due to non-optimal turbine outlet geometry
Solution Approach 1:
The heating function is segmented from the main flow path by creating a separate annular cavity that receives heated air from the compressor discharge. This allows the main turbine outlet geometry to remain optimal while providing dedicated heating capability through the cavity structure.
Solution Approach 2:
A separate heated air flow from the compressor discharge acts as an intermediary heating source, delivered through the annular cavity to the diffuser wall. This intermediary heating mechanism prevents direct contamination of the optimal turbine outlet geometry while still achieving ice prevention.
2Reliability
If hot air is delivered directly into the turbine outlet cavity, then ice formation is prevented, but thermodynamic performance is degraded due to pressure loss and unnecessary heat addition
Solution Approach 1:
Heating is applied locally and selectively only to the diffuser wall surface where ice formation occurs, rather than heating the entire turbine outlet flow. The annular cavity confines the heated air to contact only with the diffuser wall, providing precise local heating with minimal thermodynamic penalty.
Solution Approach 2:
Instead of heating the entire flow path, only the necessary portion (the diffuser wall surface) is heated. The heated air flow is limited to what is needed for ice prevention, avoiding excessive heat addition that would degrade thermodynamic performance.
3Reliability
If heated air flow is delivered through complicated plumbing schemes to ice protection features, then ice formation is prevented, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The ice protection heating function is merged with the existing compressor discharge flow path. The annular cavity is integrated into the diffuser structure itself, eliminating the need for separate plumbing schemes by using the compressor discharge as the heating source through a unified structure.
Solution Approach 2:
The system uses its own compressor discharge flow as the heating source, eliminating the need for external heating systems or complex plumbing. The annular cavity structure allows the heated air to serve dual purposes: maintaining diffuser wall temperature and being recirculated back to the turbine inlet.
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 solution effectively prevents ice formation at the turbine outlet without reducing aerodynamic performance and maintains overall thermodynamic efficiency by using simple, cost-effective heating that recovers heat energy within the system, ensuring reliable operation.
Implementation Method 1
passing a supply of heated flow into a cavity of the turbine outlet heated diffuser such that at least a portion of a radially inner wall surface of the turbine outlet heated diffuser is heated
Data Source
AI summary
The turbine outlet heated diffuser may include a cavity positioned immediately downstream of an air cycle machine turbine. The turbine outlet heated diffuser may be designed to prevent or reduce ice formation at the turbine outlet by heating the diffuser wall. The cavity may receive a heated flow from an air cycle machine compressor discharge and provide a cavity outlet flow to a turbine inlet plenum. The design of the heated diffuser is such to minimize the cycle performance impact that results from the addition of an air cycle machine icing protection feature.