Aircraft Engine Oil Flow Control for Cold Start Torque Reduction
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Solution Overview
Problem
Existing aircraft engine starting systems face significant mechanical losses and require overdimensioned starters due to high viscosity of lubricating oil at low temperatures, leading to increased mass and space requirements, and preheating solutions are not suitable for all conditions, especially in helicopters.
Innovation Solution
A method and system for controlling the oil flow profile in the lubrication circuit based on oil temperature and engine operating mode, using variable displacement pumps, electro-valves, mechanical decoupling, or rotating electric machines to optimize oil flow and pressure during engine start-up, eliminating unnecessary mechanical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the starter is dimensioned to provide torque for extreme cold conditions, then the engine can start at low temperatures, but the starter and power electronics become overdimensioned, increasing mass and space requirements
Solution Approach 1:
The patent applies preliminary action by preheating the lubricating oil before engine start-up using an oil heater when the oil temperature is below a threshold. This reduces the oil viscosity in advance, thereby reducing the starting torque requirement of the starter, allowing the starter to be dimensioned for normal conditions rather than extreme cold conditions.
Solution Approach 2:
The patent changes the physical parameter of oil temperature through heating. By increasing the oil temperature before start-up, the oil viscosity decreases, which directly reduces the resistive torque on the starter, enabling a smaller starter to provide sufficient starting torque.
2Reliability
If the starter is dimensioned to provide torque for extreme cold conditions, then the engine can start at low temperatures, but significant mass and space requirements are incurred
Solution Approach 1:
The patent applies preliminary action by preheating the lubricating oil before engine start-up using an oil heater when the oil temperature is below a threshold. This reduces the oil viscosity in advance, thereby reducing the starting torque requirement of the starter, allowing the starter to be dimensioned for normal conditions rather than extreme cold conditions.
Solution Approach 2:
The patent changes the physical parameter of oil temperature through heating. By increasing the oil temperature before start-up, the oil viscosity decreases, which directly reduces the resistive torque on the starter, enabling a smaller starter to provide sufficient starting torque.
3Reliability
If preheating is performed at low speed, then oil temperature increases gradually, but the process takes 8-10 minutes which is too long for emergency situations
Solution Approach 1:
The patent applies dynamics by making the oil pump operation variable rather than static. The oil pump is controlled to operate at high flow rates during preheating to quickly raise oil temperature, then transitions to normal operation. This dynamic control allows the preheating process to be completed much faster than the conventional 8-10 minutes.
Solution Approach 2:
The patent uses periodic action by controlling the oil pump in distinct phases: a high-flow preheating phase followed by a normal operation phase. This periodic control strategy enables rapid oil temperature increase followed by sustained lubrication, reducing the overall time required.
4Loss of energy
If the oil pump operates at low engine rotation, then oil pressure is reduced, but mechanical losses remain significant and require overdimensioned starter
Solution Approach 1:
The patent applies preliminary action by preheating the oil before start-up, which reduces oil viscosity and thereby reduces the mechanical losses in the oil pump during engine starting, allowing the starter to be smaller while maintaining starting capability.
Solution Approach 2:
The patent changes the physical parameter of oil temperature through heating, which reduces oil viscosity. This parameter change directly reduces the mechanical losses in the oil pump, as the pump requires less torque to move the less viscous oil.
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
Enables efficient engine start-up under varying conditions without overdimensioning starters, reducing mechanical losses and optimizing lubrication for improved performance and reliability.
Implementation Method 1
measuring an oil temperature, said measurement step being performed by a temperature detection device
Implementation Method 2
a lubrication circuit being constructed and arranged to circulate oil in said engine
Implementation Method 3
using variable displacement pumps, electro-valves, mechanical decoupling, or rotating electric machines to optimize oil flow and pressure
Implementation Method 4
using variable displacement pumps, electro-valves, mechanical decoupling, or rotating electric machines to optimize oil flow and pressure
Data Source
AI summary
A method for starting an aircraft engine in which the engine is coupled to a lubrication circuit including an oil pump system, the lubrication circuit being constructed and arranged to circulate oil in the engine, and in which an operating mode of the engine includes a stop mode and a standby mode, the starting method including, during a starting phase, measuring an oil temperature, the measurement being performed by a temperature detection device; depending on the temperature measured, compared to a threshold temperature, and depending on the operating mode of the engine, select a starting oil flow profile to be applied in said engine, the selection being performed by a calculator, and applying the selected starting oil flow profile by the oil pump system, the oil pump system being controlled by the calculator.