Engine core speed reducing method and system

A turbine active clearance controller for an engine system, comprising:

• a processor;
• and
• a controller,
• wherein the processor is configured to receive sensed engine parameters indicative of operation of the engine system and to determine a condition of the engine system based on the engine parameters,
• wherein the processor is configured to compare the sensed engine parameters with predetermined thresholds,
• wherein the processor is configured to obtain the condition of the engine system based on compared results,
• wherein the controller is configured to influence an engine core speed by controlling an engine turbine clearance based on the condition of the engine system,
• wherein the turbine active clearance controller is configured to bias open the engine turbine clearance by a bias amount,
• wherein the bias amount is an amount of the engine turbine clearance,
• wherein, when the exhaust gas temperature is less than a predetermined temperature threshold and the engine core speed is larger than a predetermined first speed threshold, the engine system is determined to be in a first condition, and
• wherein:
• if the engine core speed is not larger than a predetermined higher second speed threshold, the bias amount of the engine turbine clearance is determined by a predetermined bias clearance multiplied by a ratio of a difference between the engine core speed and the predetermined first speed threshold and a difference between the predetermined second speed threshold and the predetermined first speed threshold, and
• if the engine core speed is larger than the predetermined second speed threshold, the bias amount is the predetermined bias clearance.

A method for reducing an engine core speed via a turbine active clearance controller, the turbine active clearance controller comprising:

• a processor;
• and
• a controller,
• wherein the processor is configured to receive sensed engine parameters indicative of operation of the engine system and to determine a condition of the engine system based on the engine parameters,
• wherein the processor is configured to compare the sensed engine parameters with predetermined thresholds,
• wherein the processor is configured to obtain the condition of the engine system based on compared results,
• wherein the controller is configured to influence an engine core speed by controlling an engine turbine clearance based on the condition of the engine system,
• wherein the turbine active clearance controller is configured to bias open the engine turbine clearance by a bias amount,
• wherein the bias amount is an amount of the engine turbine clearance,
• wherein, when the exhaust gas temperature is less than a predetermined temperature threshold and the engine core speed is larger than a predetermined first speed threshold, the engine system is determined to be in a first condition,
• wherein:
• if the engine core speed is not larger than a predetermined higher second speed threshold, the bias amount of the engine turbine clearance is determined by a predetermined bias clearance multiplied by a ratio of a difference between the engine core speed and the predetermined first speed threshold and a difference between the predetermined second speed threshold and the predetermined first speed threshold, and
• if the engine core speed is larger than the predetermined second speed threshold, the bias amount is the predetermined bias clearance,
• the method comprising:
• determining the condition of the engine system during operation of the engine system;
• and
• controlling an engine turbine clearance based on the condition of the engine system to influence the engine core speed.