Turbine Nozzle Overlapping Flaps for Core Stream Mixing
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Solution Overview
Problem
Turbine engine nozzles with confluent streams face issues with ventilation during idling, where the reduced energy of the core stream leads to poor suction, potentially causing hot gas ingestion into the bypass channel, and at cruising speeds, vortex generators increase head loss due to residual gyration of the core stream.
Innovation Solution
The nozzle design incorporates an annular core cowl with overlapping flaps that create mixing zones, allowing the core stream's azimuth component to increase turbulence during idling while avoiding these zones at cruising speeds, minimizing head loss, by positioning one side edge internally and the other externally for each flap, and using winglets or undulations to enhance mixing without increasing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vortex generators are positioned in the primary channel to enhance mixing between core and bypass streams, then mixing quality improves, but head loss increases significantly during cruising flight
Solution Approach 1:
The core cowl flaps are designed to be dynamically responsive to the direction of residual gyration of the core stream. During idling, the flaps create mixing zones that interact with the core stream's azimuth component to enhance mixing. During cruising, the flaps are positioned to be aligned with the core stream flow, minimizing interference and head loss. This dynamic adaptation to different operating conditions resolves the contradiction between mixing quality and head loss.
Solution Approach 2:
The mixing zones are created locally at specific positions where the core cowl flaps overlap, rather than using vortex generators along the entire primary channel. This localized approach enhances mixing only where needed during idling while minimizing the overall impact on head loss during cruising flight.
2Use of energy by moving object
If the core stream energy is reduced during idling, then fuel consumption decreases, but suction capability deteriorates leading to hot gas ingestion into the bypass channel
Solution Approach 1:
The invention converts the harmful effect of reduced core stream energy during idling into a beneficial effect. The residual gyration of the core stream, which would normally reduce suction capability, is instead utilized to drive the core stream through the mixing zones created by the overlapping flaps. This passive utilization of residual gyration enhances mixing and prevents hot gas ingestion without requiring additional energy input.
Solution Approach 2:
The core stream's own residual gyration is used to drive it through the mixing zones during idling, eliminating the need for external energy input or active control mechanisms. The system serves itself by utilizing the inherent rotational momentum of the core stream to achieve the desired mixing and ventilation effects.
3Reliability
If residual gyration of the core stream is present during idling, then ventilation is compromised, but the same residual gyration causes mismatching with vortex generators during cruising
Solution Approach 1:
The core cowl flaps are designed to adapt their configuration based on the direction of residual gyration, which changes with operating speed. During idling, the flaps create mixing zones that exploit the residual gyration to enhance ventilation. During cruising, the flaps are positioned to be aligned with the reversed residual gyration direction, avoiding mismatch and maintaining compatibility. This dynamic adaptation resolves the contradiction between ventilation performance and adaptability.
Solution Approach 2:
The overlapping flap structure serves multiple functions across different operating conditions: during idling, it creates mixing zones that enhance ventilation using residual gyration; during cruising, it aligns with the flow to minimize head loss. This multi-functionality allows the same structure to effectively handle both idling and cruising conditions despite the reversal of residual gyration direction.
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 effectively reduces the risk of hot gas ingestion during idling and minimizes head losses during cruising, improving mixing between core and bypass streams while optimizing engine performance across different operating speeds.
Implementation Method 1
the core stream on entry into the nozzle possesses an azimuth component driving residual gyratory movement of the core stream... increase turbulence, thereby enhancing mixing between the streams
Implementation Method 2
the nacelle of the engine is ventilated by a stream of air flowing in the bypass channel and that is sucked in by the core stream in the confluence zone by a jet pump effect
Data Source
AI summary
A turbine engine nozzle having confluent streams, the nozzle including a core cowl arranged around an annular central body and co-operating therewith to define a core annular channel for passing a flow of a core stream, the core stream on entry into the nozzle possessing an azimuth component driving residual gyratory movement of the core stream in two opposite gyratory flow directions corresponding to two operating speeds of the engine, the core cowl having an annular upstream portion that is extended downstream by an annular terminal portion having longitudinal cuts forming a plurality of flaps that overlap radially in pairs via their respective side edges in such a manner that, for each flap, one of the two side edges of the flap is positioned internally relative to the corresponding side edge of one of the adjacent flaps, while the other side edge of the flap is positioned externally relative to the corresponding side edge of the other adjacent flap.