Turbine Rotor Deceleration via Electrical Braking
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Solution Overview
Problem
Turbine shut-down procedures are inefficient, leading to prolonged deceleration times, mechanical and thermo-mechanical stress, and increased costs due to auxiliary power consumption, as the turbine rotor takes around 30 minutes to reach stand-still after flame off, causing unavailability for immediate restart, potential damage from resonance frequencies, and excessive thermal transients.
Innovation Solution
Engaging an electric motor with the turbine rotor to apply negative torque through a braking system, transforming kinetic energy into electric energy, thereby reducing deceleration time and vibrational loading, and optimizing the braking torque based on rotation speed and other parameters to manage thermal and vibrational stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the turbine rotor is allowed to decelerate freely after flame off, then the mechanical complexity is reduced, but the deceleration time becomes excessively long (approximately 30 minutes)
Solution Approach 1:
The patent replaces the passive mechanical deceleration system with an active electrical braking system. The generator is controlled to operate as a brake, converting the rotational kinetic energy of the turbine rotor into electrical energy that can be dissipated or recovered, thereby dramatically reducing deceleration time from 30 minutes to a much shorter duration.
Solution Approach 2:
The patent changes the operational parameters of the generator from power generation mode to braking mode. By controlling the generator to absorb kinetic energy and convert it to electrical energy, the system transforms the deceleration process from a slow passive mechanical dissipation to an active controlled electrical braking process.
2Strength
If the turbine rotor decelerates slowly over 30 minutes, then mechanical stress is reduced, but the turbine becomes unavailable for immediate restart and auxiliary power consumption increases
Solution Approach 1:
The patent replaces passive mechanical deceleration with active electrical braking, enabling controlled and rapid energy dissipation. This allows the turbine to be brought to a stop much faster, improving availability for immediate restart while the control system manages stress through regulated braking torque application.
Solution Approach 2:
The turbine's own generator is utilized to provide the braking function, eliminating the need for external auxiliary power sources or batteries. The kinetic energy that would otherwise be wasted is converted to electrical energy, which can be dissipated in resistors or fed back to the grid, making the system self-sufficient and reducing auxiliary power consumption.
3Loss of time
If the turbine rotor passes through resonance frequencies during slow deceleration, then the deceleration time is extended, but vibrational loading and potential damage accumulate
Solution Approach 1:
The patent applies electrical braking to rapidly reduce the rotor speed, enabling the system to quickly pass through critical resonance frequency ranges. By controlling the braking torque, the system minimizes the time spent in vulnerable speed ranges where resonance could cause excessive vibrational loading and potential damage.
Solution Approach 2:
The replacement of passive mechanical deceleration with active electrical braking provides precise control over the deceleration profile. This allows the system to manage vibrational loading by adjusting braking intensity, particularly when approaching resonance frequencies, thereby reducing cumulative damage from vibration while maintaining short deceleration times.
4Temperature
If the turbine cools down during the 30-minute run-down, then thermal stress is reduced, but subsequent immediate restart causes substantial thermo-mechanical stresses
Solution Approach 1:
The patent uses electrical braking to rapidly reduce rotor speed and minimize the run-down time. This approach prevents excessive cooling of the turbine components during deceleration, thereby maintaining thermal conditions that allow for immediate restart without causing substantial thermo-mechanical stresses, while the control system manages thermal transitions.
5Reliability
If larger clearances are set to accommodate thermal transients during run-down, then the risk of rotor blocking is reduced, but the overall engine performance deteriorates
Solution Approach 1:
The patent implements rapid controlled deceleration using electrical braking, which significantly reduces the duration of thermal transients during run-down. By minimizing the time over which cooling occurs, the system reduces the magnitude of thermal contraction and clearance changes, allowing smaller clearances to be used while maintaining reliability and improving engine performance.
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
The method significantly reduces deceleration time by up to a third, minimizes vibrational loading, reduces thermal stresses, and enhances the turbine's availability for immediate restart, while also reducing the cost impact of auxiliary power consumption by recovering kinetic energy.
Implementation Method 1
transforming kinetic energy into electric energy
Data Source
Figure 1
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AI summary
The present invention relates to a method of decelerating a turbine rotor (12) of a turbine engine (1), wherein at least one electric motor (30) is engaged with the turbine rotor (12), wherein a braking system (40), preferably the starting system, is engaged with the at least one electric motor (30), preferably the generator of the turbine engine (1), so as to use the at least one electric motor (30) to apply a negative (braking) torque on the turbine rotor (12). The method is characterized in that, after flame off, the braking system (40) is used for dissipating kinetic energy available in the turbine engine (1) after flame off by means of the at least one electric motor (30).