Hybrid Gearbox Speed Ratio Control for No-Load Turbine Start

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Solution Overview

Problem

Current train systems face inefficiencies and increased costs due to the need for complex power sources and additional equipment to manage variable speed ratios and start-up loads, particularly when using fixed transmission ratios and single-shaft gas turbines, which lead to sub-synchronous torsional interactions and higher costs for electric motors.

Innovation Solution

A method utilizing a hybrid gearbox with a layshaft gear arrangement and motor-generator units to control the star carrier speed, allowing for continuous adjustment of transmission speed ratios and enabling no-load start-ups, synchronization of driven equipment speed, and efficient operation of power sources like gas turbines and electric motors, while minimizing CO2 production and building spinning reserves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed transmission ratio is used in a system, then the system structure is simpler, but the driver equipment must be capable of changing rotational speed which increases complexity and cost

Engineering Contradiction:

Improvetransmission system complexityVSAvoidspeed variation capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent applies a variable gear ratio gearbox that dynamically changes the transmission ratio between input and output shafts. This allows the system to adapt speed ratios continuously without requiring the driver to vary its rotational speed, thus maintaining simple driver equipment while achieving speed variation capability through the dynamic gearbox mechanism.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The variable gear ratio gearbox acts as an intermediary between the driver and the driven equipment. It mediates the speed and torque transmission, allowing the driver to operate at constant speed while the gearbox adjusts the output speed ratio to meet varying load requirements, thereby avoiding the need for complex variable speed drivers.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a variable-transmission-ratio gearbox is used, then speed adjustment flexibility is improved, but the device complexity and cost increase

Engineering Contradiction:

Improvespeed adjustment flexibilityVSAvoidgearbox structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the variable gear ratio mechanism with a single-shaft gas turbine drive system. By integrating the variable gearbox with the gas turbine directly (without requiring clutches or starter motors), the system achieves speed adjustment flexibility while reducing overall device complexity and eliminating the need for additional starting equipment.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The variable gear ratio gearbox is designed to perform multiple functions: it provides continuous speed ratio adjustment, enables no-load starting of the gas turbine, and allows the system to operate with both fixed and variable speed drivers. This multi-functionality reduces the need for separate specialized components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Device complexity

If direct mechanical connection through fixed speed ratio transmission is used during gas turbine start-up, then the transmission structure is simpler, but the gas turbine cannot start due to torque limitations

Engineering Contradiction:

Improvetransmission structureVSAvoidstart-up capability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

During gas turbine start-up, the variable gear ratio gearbox dynamically adjusts the transmission ratio to provide mechanical advantage. This allows the gas turbine to start under no-load conditions by temporarily modifying the torque multiplication ratio, and then transitions to normal operating ratios once the turbine is running, thereby enabling start-up capability without complex additional equipment.

Inventive Principle:

Principle #15Dynamics

4Adaptability or versatility

If VFD electric motor is used as power source, then speed variation capability is improved, but sub-synchronous torsional interactions occur and CAPEX increases

Engineering Contradiction:

Improvespeed variation capabilityVSAvoidsub-synchronous torsional interactions

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the VFD electric motor system with a mechanical solution using a variable gear ratio gearbox coupled with a constant speed driver (such as a single-shaft gas turbine). This substitution eliminates the electrical controls and power electronics that cause sub-synchronous torsional interactions, while achieving speed variation through pure mechanical means in the gearbox.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12055201B2Method for operating a train system for a mechanical driven equipment

Publication Date: 2024.08.06 NUOVO PIGNONE TECH SRL

AI summary

A method of operating a train system for driving a mechanical driven equipment is disclosed. The train system comprises a hybrid gearbox connected between a power source and a load to be driven. The hybrid gearbox includes a lay shaft gear, which transmission ratio between the power source and the load and a motor-generator unit can be adjusted, to adjust the transmission speed ratio arranged, to balance the power generated by the power source and to improve the efficiency of the train system in a number of operating conditions.