Off-Line Engine Oil Warming for Cruise Restart
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Solution Overview
Problem
During cruise flight, shutting down one engine in a multi-engine aircraft can lead to prolonged engine restart times due to cold oil viscosity issues, especially at high altitudes and low temperatures.
Innovation Solution
The method involves periodically or continuously cranking the off-line engine without starting it, using a starter-generator or electrical oil-circulation pump, to circulate and warm the engine oil. This can be done using a heat exchanger that transfers heat from the operating engine or electrical heaters in the oil tank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If one engine is shut down during cruise flight to improve fuel efficiency, then fuel consumption is reduced, but engine restart time increases due to cold oil viscosity
Solution Approach 1:
The patent applies preliminary action by cranking the off-line engine before a restart is needed, which circulates and warms the engine oil in advance. This preliminary warming action prevents the oil from becoming too cold and viscous, thereby reducing the actual restart time when the engine needs to be started again during cruise flight.
Solution Approach 2:
The patent uses an intermediary approach by introducing a heat exchanger that transfers heat from the operating engine to the off-line engine's oil system. This heat transfer mechanism serves as a mediator to warm the off-line engine's oil without requiring the engine to be fully restarted, thus resolving the contradiction between fuel efficiency and restart time.
2Loss of time
If engine oil is warmed by continuous cranking of the off-line engine, then engine restart time is reduced, but energy consumption increases
Solution Approach 1:
The patent applies periodic action by cranking the off-line engine at intervals rather than continuously. The system monitors oil temperature and cranks the engine periodically to maintain the oil above a threshold temperature, which reduces energy consumption compared to continuous cranking while still achieving the goal of reducing restart time.
Solution Approach 2:
The patent uses feedback control by monitoring the oil temperature of the off-line engine and adjusting the cranking operation accordingly. When the oil temperature reaches a predetermined threshold, the cranking stops; when the temperature drops below the threshold, cranking resumes. This feedback mechanism optimizes energy consumption while maintaining effective oil warming.
3Productivity
If heat exchanger is used to transfer heat from operating engine to off-line engine oil, then engine oil warming efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the heat exchanger to serve multiple functions: it transfers heat from the operating engine to the off-line engine's oil system, and can also be used for cooling the operating engine's oil system. This multi-functionality justifies the added device complexity by providing versatile thermal management capabilities across both engines.
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 approach reduces engine restart times by maintaining a warmer engine oil viscosity, thus improving fuel efficiency and operational safety during cruise flights.
Implementation Method 1
The engine oil may also or alternatively be warmed using a heat exchanger operable to transfer heat from a heat source to the engine oil, wherein the heat source is associated with the second engine
Implementation Method 2
The lubrication system may include a heat exchanger operable to transfer heat from a heat source to the lubricant. The heat source may be bleed air from the second engine or exhaust from an oil cooler, an electrical generator, or another air-cooled component on the second engine
Implementation Method 3
The first engine may be cranked using a start-generator automatically operated
Data Source
AI summary
Embodiments are directed to operating a multi-engine aircraft during a cruise flight condition. A first engine is put off-line during flight while allowing a second engine to continue operating. The second engine provides sufficient power to maintain the multi-engine aircraft in the cruise flight condition. An outside air temperature, a first engine temperature, and/or an engine oil temperature is monitored and, when the temperature is below a predetermined threshold, the engine oil for the off-line first engine is warmed. The off-line engine oil may be warmed by continuously or periodically cranking the first engine without restarting the first engine. Alternatively, the engine oil may be warmed using a heat exchanger, such as an air-to-oil or oil-to-oil heat exchanger, or by using electronic heaters on an oil tank.