Turbomachine Nacelle Ventilation Using Jet Pump Ejector
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Solution Overview
Problem
Turbine engine nacelles, especially those with low or zero Mach number, face challenges in ventilation due to lack of dynamic pressure, leading to excessive temperatures that can reduce service life, particularly in turboprop engines with unducted and contra-rotating propellers.
Innovation Solution
The implementation of a jet pump-type ejector with two parallel nozzles in the duct, which creates a mixer and diffuser to circulate air within the nacelle, utilizing the Venturi effect to ensure ventilation even at low Mach numbers, while reducing bulk and maintaining efficiency by optimizing the duct length and cross-sectional area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single nozzle ejector is used for nacelle ventilation, then the device bulk is reduced, but the ventilation efficiency and yield are insufficient
Solution Approach 1:
The single nozzle is segmented into two parallel nozzles within the same ejector device. This segmentation allows each nozzle to contribute to the Venturi effect, collectively generating sufficient negative pressure for effective ventilation while maintaining a compact overall structure that reduces total bulk compared to using multiple separate ejectors.
Solution Approach 2:
Two nozzles are merged into a single ejector housing with a shared duct structure. The nozzles are positioned parallel to each other and spaced at a specific distance (π/2·R2) to optimize their combined effect. This merging approach achieves the ventilation yield of multiple ejectors while consolidating the bulk into one device.
2Productivity
If the duct length is increased to improve mixing of primary and secondary air flows, then the ventilation efficiency is improved, but the ejector bulk and installation space requirements increase
Solution Approach 1:
The mixer geometry transitions from a conventional linear extension to a three-dimensional configuration with curved surfaces. The side walls with semi-circular cross-sections create a compact volumetric mixing chamber that achieves sufficient mixing length without excessive axial extension, effectively utilizing spatial dimensions to reduce overall bulk.
Solution Approach 2:
The mixer incorporates curved side walls with semi-circular cross-sections instead of straight cylindrical walls. This curvature optimizes flow patterns and mixing efficiency while compacting the mixer volume. The bending radius R2 is specifically designed to center on the nozzle axis, creating an optimized curved flow path that enhances mixing within a reduced volume.
3Reliability
If the ejector is oversized to ensure adequate output cross-section for safety, then the ventilation reliability is improved, but the installation space requirements and device complexity increase
Solution Approach 1:
The key geometric parameter—the center-to-center distance between nozzles—is optimized to π/2·R2. This specific parameter value ensures that the combined output cross-section of two nozzles provides adequate ventilation capacity and safety margin while maintaining a compact overall ejector尺寸. The parameter optimization allows reliable ventilation performance without oversizing the device.
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 solution effectively ventilates the nacelle, reducing temperature-related stress on equipment and extending service life by maintaining a high yield and preserving the diameter:length ratio of the mixer, even when the aircraft is on the ground.
Implementation Method 1
The operation of an ejector of the jet pump type is well known to a person skilled in the art and is based on the principle of the Venturi effect. The primary fluid which is ejected into the duct expands in the diffuser, creating a negative pressure and forcing the passage of secondary fluid from the input as far as the output of the duct
Implementation Method 2
The primary fluid which is ejected into the duct expands in the diffuser, creating a negative pressure and forcing the passage of secondary fluid from the input as far as the output of the duct, the secondary fluid then being mixed with the primary fluid in the duct
Data Source
AI summary
A jet pump type ejector for a turbomachine, including a duct through which a secondary ventilation air flow passes, and a first end of which forms an air intake and a second end of which forms an air outlet, the two nozzles for spraying a primary air flow being mounted in the duct which defines a mixer and a diffuser downstream from the nozzle, the two nozzles being parallel and adjacent to one another, the mixer including two substantially planar longitudinal walls, bottom and top respectively, connected to one another by two side walls having a semicircular cross-section, in which the radius of curvature R2 is centered on the axis of a nozzle, the center-to-center distance of the nozzles being substantially equal to Π/2 times R2 or (Π/2)R2.