Electric Propulsion Engine Tip Speed Ratio for Drag Reduction
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Solution Overview
Problem
Conventional aircraft propulsion systems face inefficiencies due to drag, which is not adequately addressed by existing boundary layer ingestion systems that often result in nonuniform airflow and efficiency losses in turbofan jet engines.
Innovation Solution
An electric propulsion system with a fan and electric machine is configured to maintain a specific tip speed ratio relative to fan pressure ratio, optimizing efficiency and power density by operating within 20% of the equation 1.01×RFP−0.311, and incorporating a boundary layer ingestion fan to reduce drag and enhance thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If boundary layer ingestion systems are used to route slow moving air into turbofan jet engines, then drag on the aircraft is reduced, but the relatively slow moving flow with nonuniform velocity profile causes efficiency loss in the engines
Solution Approach 1:
The patent replaces conventional mechanical turbofan jet engines with electric propulsion systems that use electric machines (motors) to directly drive fans. This substitution eliminates the complex mechanical systems including combustors, turbines, and shafts, allowing for optimized fan blade designs that can efficiently process boundary layer air with nonuniform velocity profiles while maintaining high propulsive efficiency and reducing drag.
Solution Approach 2:
The patent changes the operating parameters of the propulsion system by using electric machines that can precisely control fan speed, torque, and blade pitch. This allows the system to optimize performance across varying flight conditions and efficiently ingest boundary layer air without the efficiency penalties associated with conventional turbofan engines operating at non-optimal conditions.
2Stability of the object's composition
If conventional turbofan jet engines are mounted separately from the wing and fuselage to interact with freestream airflows, then turbulence in the inlet airflow is reduced, but drag on the aircraft increases
Solution Approach 1:
The patent replaces conventional turbofan engines with electric propulsion systems that can be integrated into the aircraft structure. The electric machines drive fans that can be positioned to ingest boundary layer air from the fuselage and wings, converting what was previously a harmful drag-inducing boundary layer into a useful resource for propulsion, thereby reducing overall aircraft drag.
Solution Approach 2:
The patent converts the harmful boundary layer air flow, which normally increases drag when disrupted, into a beneficial resource by using electric propulsion fans to ingest and accelerate this air. The electric fans are designed to efficiently process the nonuniform boundary layer flow and convert it into useful thrust, thereby reducing the net drag on the aircraft while maintaining or improving propulsion efficiency.
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 configuration enhances the efficiency and power density of the electric propulsion engine across various fan and motor sizes, effectively reducing drag and increasing net thrust while minimizing engine efficiency losses.
Implementation Method 1
an electric machine defining an electric machine tip speed during operation of the propulsion engine... a fan rotatable about the central axis of the propulsion engine by the electric machine
Implementation Method 2
a fan rotatable about the central axis of the propulsion engine by the electric machine. The fan defines a fan pressure ratio (RFP) and includes a plurality of fan blades
Implementation Method 3
boundary layer ingestion systems to route a portion of relatively slow moving air forming a boundary layer across, e.g., the fuselage and/or the wings, into the turbofan jet engines
Data Source
AI summary
A propulsion system for an aircraft is provided having a propulsion engine configured to be mounted to the aircraft. The propulsion engine includes an electric machine defining an electric machine tip speed during operation. The propulsion system additionally includes a fan rotatable about a central axis of the electric propulsion engine with the electric machine. The fan defines a fan pressure ratio, RFP, and includes a plurality of fan blades, each fan blade defining a fan blade tip speed. The electric propulsion engine defines a ratio of the fan blade tip speed to electric machine tip speed that is within twenty percent of the equation, 1.01×RFP−0.311, such that the propulsion engine may operate at a desired efficiency.