According to an aspect, a gas turbine engine includes a turbine section with a turbine case and a plurality of turbine blades within the turbine case. The gas turbine engine also includes an active clearance control system with an active clearance control cooling air supply, a valve pneumatically coupled to the active clearance control cooling air supply, and a controller. The controller is configured to determine an active cooling control schedule adjustment based on a condition of the gas turbine engine, operate the active clearance control system according to an active cooling control schedule as modified by the active cooling control schedule adjustment, apply a decay function to the active cooling control schedule adjustment to reduce an effect on the active cooling control schedule adjustment, and resume operating the active clearance control system according to the active cooling control schedule based on an active cooling control condition being met.

An ignition system for igniting fuel in a gas turbine engine includes a power supply and an energy storage network electrically connected to the power supply. The energy storage network includes a first stage having a first capacitor and a second stage having a second capacitor. The ignition system further includes an engine igniter electrically coupled to the energy storage network.

Aircraft hydrogen fuel systems and methods and systems of starting such systems are described. The aircraft hydrogen fuel systems include a hydrogen burning main engine, a main tank configured to contain liquid hydrogen to be supplied to the main engine during a normal operation, and a starter tank configured to contain gaseous hydrogen to be used during a startup operation of the main engine. Methods and processes for starting and/or restarting such systems are described.

Methods and systems for starting an engine are provided. A cold-start request to start the engine in a first operating condition associated with a predetermined engine temperature range is obtained. In response to obtaining the cold-start request, an amount of boost fuel to provide to the engine is determined, based on at least one second operating condition of the engine. The engine is started by supplementing a baseline fuel flow to the engine with the amount of boost fuel.

Chemical thrusters convert chemical energy predominantly into thermal energy and further into kinetic energy. These conversions are lossy and typically limit the usable thrust to 40-70% of the chemical energy (rockets). The exit velocity is maximized by increasing the temperature. However, temperature cannot be increased at will and can increase losses. Thrusters also have limited controllability under changing external conditions. The options for isochoric or detonative combustion are limited. This concept is intended to increase efficiency and controllability.

Through changes in catalytic loads and electromagnetic dose, combustion is increased and can be selectively regulated. Pressure/temperature are influenced and can be adapted e.g. to the changing external pressure. The achievable thrust increases due to the higher exit velocity. Further advantages exist. The geometry of combustion chambers can be optimized (e.g. smaller, more efficient). The concept is particularly promising for detonation engines or novel supersonic combustors.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

A method of operating a multi-engine system of an aircraft having first and second engines includes accumulating compressed air in a pressure vessel external to the engines, and operating the first and second engines asymmetrically, by controlling the first engine to operate in an active operating condition providing sufficient power and/or rotor speed for demands of the aircraft, and controlling the second engine to operate in a standby operating condition wherein the second engine produces less power output than the first engine. In response to a power demand request, the second engine is accelerated out of the standby operating condition by introducing therein compressed air from the pressure vessel at a location upstream of a combustor of the second engine.

A method of operating a multi-engine system of an aircraft having first and second engines includes accumulating compressed air in a pressure vessel external to the engines, and operating the first and second engines asymmetrically, by controlling the first engine to operate in an active operating condition providing sufficient power and/or rotor speed for demands of the aircraft, and controlling the second engine to operate in a standby operating condition wherein the second engine produces less power output than the first engine. In response to a power demand request, the second engine is accelerated out of the standby operating condition by introducing therein compressed air from the pressure vessel at a location upstream of a combustor of the second engine.

In a one embodiment, a gas turbine system that includes a first pump that supplies distillate fuel to a combustor. A second pump that supplies fuel oil to the combustor. A fuel selection unit that controls a first flow of distillate fuel and a second flow of fuel oil to the combustor. A controller that receives feedback from a sensor and in response to the feedback from the sensor controls the fuel selection unit to start the gas turbine system on the fuel oil.

In a one embodiment, a gas turbine system that includes a first pump that supplies distillate fuel to a combustor. A second pump that supplies fuel oil to the combustor. A fuel selection unit that controls a first flow of distillate fuel and a second flow of fuel oil to the combustor. A controller that receives feedback from a sensor and in response to the feedback from the sensor controls the fuel selection unit to start the gas turbine system on the fuel oil.