Turbofan Heat Exchanger Vanes with Diffuser Inlets for Low-Loss Cooling
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Solution Overview
Problem
Conventional turbofan gas turbine engines face performance issues due to the use of bypass air or compressor offtake streams as cooling mediums in heat exchangers, leading to reduced specific thrust and increased specific fuel consumption, as well as reduced surge margin.
Innovation Solution
A heat exchanger module with a circumferential array of radially-extending hollow vanes, where the airflow is divided into vane and channel flows, with a diffuser element at the inlet to slow the vane airflow, minimizing aerodynamic losses and enhancing heat transfer efficiency, and optionally featuring convergent exhaust portions and flow modulators to regulate airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bypass air or compressor offtake stream is used as cooling medium in heat exchanger, then heat transfer function is achieved, but specific thrust is reduced and specific fuel consumption increases
Solution Approach 1:
The invention extracts the heat exchanger function from the main engine airflow path by using a separate air intake system. The heat exchanger receives air from a dedicated intake rather than from the compressor offtake or bypass streams, thereby isolating the cooling function from the thrust-generating airflow and eliminating the negative impact on specific thrust
Solution Approach 2:
The invention introduces an intermediary airflow path that connects the ambient air to the heat exchanger through a separate intake system. This intermediary airflow serves as the cooling medium without interfering with the main engine airflow, acting as a mediator between the heat rejection requirement and the thrust generation requirement
2Temperature
If bypass air or compressor offtake stream is used as cooling medium, then heat transfer function is achieved, but surge margin is reduced
Solution Approach 1:
The invention extracts the heat exchanger air supply from the compressor offtake stream, removing the dependency between the cooling system and the compressor airflow. This separation ensures that the heat exchanger operation does not affect compressor stability and surge margin
Solution Approach 2:
A separate air intake system acts as an intermediary, providing cooling air to the heat exchanger independently of the compressor airflow path. This intermediary system prevents any potential negative interaction between the heat exchanger and compressor operation, maintaining surge margin
3Productivity
If high velocity airflow is used through hollow vane, then heat transfer rate increases, but aerodynamic losses increase and heat transfer element damage risk increases
Solution Approach 1:
The invention employs adjustable flow control elements within the hollow vanes that can dynamically regulate airflow velocity. This allows the system to optimize the balance between heat transfer rate and aerodynamic losses by adjusting the flow characteristics according to operating conditions, preventing excessive velocities that would cause high aerodynamic losses
Solution Approach 2:
The invention changes the airflow parameters by using diffuser elements and flow control mechanisms to reduce velocity while maintaining mass flow rate. By changing the velocity parameter independently of the mass flow, the system achieves acceptable heat transfer rates with reduced aerodynamic losses
4Productivity
If high velocity airflow is used through hollow vane, then heat transfer efficiency improves, but risk of damage to heat transfer elements increases
Solution Approach 1:
The invention uses dynamically adjustable flow control elements that can limit maximum airflow velocity through the hollow vanes. This dynamic control protects heat transfer elements from high-velocity damage while maintaining sufficient heat transfer efficiency by optimizing velocity within safe limits
Solution Approach 2:
The invention incorporates flow control mechanisms upstream of the heat transfer elements that preemptively reduce airflow velocity to protective levels. This prior cushioning of the airflow prevents potential damage to heat transfer elements before it can occur, while still maintaining adequate heat transfer performance
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 improves heat transfer efficiency, reduces the risk of damage to heat transfer elements, and enhances the reliability and aerodynamic efficiency of the turbofan engine by optimizing airflow and heat energy rejection, while maintaining or improving engine performance.
Implementation Method 1
The diffuser slows the velocity of the air flow as the air flow enters the hollow vane and minimises the aerodynamic losses during this process
Implementation Method 2
each of the hollow vanes accommodating at least one heat transfer element for the transfer of heat from a first fluid contained within the or each heat transfer element to the corresponding vane airflow passing over a surface of the or each heat transfer element
Implementation Method 3
Since it is the vane air flow passing over a surface of the heat transfer elements that enables the rejection of the heat energy to the vane air flow, a reduction in the velocity of the vane air flow improves the efficiency of the heat transfer process
Data Source
AI summary
A turbofan gas turbine engine includes heat exchanger module, fan assembly, compressor, turbine and exhaust modules. The fan includes a plurality of fan blades. The heat exchanger in fluid communicates with the fan assembly by an inlet duct, and the heat exchanger includes a plurality of radially-extending hollow vanes arranged in a circumferential array, with a channel extending axially between each pair of adjacent hollow vanes. An airflow entering the heat exchanger is divided between a set of vane airflows and a set of channel airflows. Each vane airflow has a vane mass flow rate FlowVane, and each channel air flow has a channel mass flow rate FlowChan. Each hollow vane includes, an inlet, heat transfer, and exhaust portions, with the inlet portion comprising a diffuser element and the heat transfer portion including at least one heat transfer element. The diffuser element causes FlowVane to be lower than FlowChan.