An engine system for an aircraft includes a first gas turbine engine, a second gas turbine engine, and a control system. The control system is configured to operate the first gas turbine engine with an idle fuel burn schedule in a taxi mode of the aircraft and operate the second gas turbine engine with a sub-idle fuel burn schedule in the taxi mode of the aircraft. The sub-idle fuel burn schedule includes a reduction of the idle fuel burn schedule. A fuel flow of the first gas turbine engine and the second gas turbine engine is increased above the idle fuel burn schedule prior to takeoff of the aircraft.

A duct for a gas turbine engine, the duct has a wall defining a flow passage for an airflow, the wall defining a baseline surface, the duct comprising an off-take port for drawing a portion of the airflow out of the duct, the off-take port including a projected portion projecting away from the baseline surface into the flow passage, a conduit opening defined within the projected portion for receiving the portion of the airflow, and an off-take conduit communicating with the conduit opening for directing the portion of the airflow away from the duct, the projected portion having a hump upstream of the conduit opening relative to a direction of the airflow and a scoop downstream of the opening relative to the direction of the airflow.

A duct for a gas turbine engine, the duct has a wall defining a flow passage for an airflow, the wall defining a baseline surface, the duct comprising an off-take port for drawing a portion of the airflow out of the duct, the off-take port including a projected portion projecting away from the baseline surface into the flow passage, a conduit opening defined within the projected portion for receiving the portion of the airflow, and an off-take conduit communicating with the conduit opening for directing the portion of the airflow away from the duct, the projected portion having a hump upstream of the conduit opening relative to a direction of the airflow and a scoop downstream of the opening relative to the direction of the airflow.

A control method for controlling an air intake system for an engine of a vehicle; the intake system has a main air intake coupled to an air filter provided with a heating device. The control method comprises the steps of: determining a pressure difference between upstream and downstream of the air filter; determining a variation speed of the pressure difference between upstream and downstream of the air filter by calculating the first derivative in time of the pressure difference between upstream and downstream of the air filter; and turning on and/or turning off the heating device based on the variation speed of the pressure difference between upstream and downstream of the air filter.

A control method for controlling an air intake system for an engine of a vehicle; the intake system has a main air intake coupled to an air filter provided with a heating device. The control method comprises the steps of: determining a pressure difference between upstream and downstream of the air filter; determining a variation speed of the pressure difference between upstream and downstream of the air filter by calculating the first derivative in time of the pressure difference between upstream and downstream of the air filter; and turning on and/or turning off the heating device based on the variation speed of the pressure difference between upstream and downstream of the air filter.

Operating coal fired energy systems. A method of operating a coal fired energy system comprises operating a coal fired steam generator comprising a coal feed system and a main air feed system to provide a coal-air mixture as a heating source for a boiler for generating steam. The method includes operating an auxiliary air compression system comprising a fueled engine coupled to a compressor for providing an auxiliary supply of compressed air to a soot blower of the coal-fired steam generator. The method comprises injecting the auxiliary supply of compressed air along walls of the boiler to remove soot and ash buildup from the boiler.

Operating coal fired energy systems. A method of operating a coal fired energy system comprises operating a coal fired steam generator comprising a coal feed system and a main air feed system to provide a coal-air mixture as a heating source for a boiler for generating steam. The method includes operating an auxiliary air compression system comprising a fueled engine coupled to a compressor for providing an auxiliary supply of compressed air to a soot blower of the coal-fired steam generator. The method comprises injecting the auxiliary supply of compressed air along walls of the boiler to remove soot and ash buildup from the boiler.

A system and method for increasing power output of a gas turbine. A method of increasing a power output of a gas turbine comprises providing an auxiliary system configured to be coupled to the gas turbine. The auxiliary system includes a natural gas engine, a compressor, and a heat exchanger fluidly coupled to the compressor. The method includes fluidly coupling the auxiliary system to a combustor case of the gas turbine. The method comprises operating the natural gas engine to drive the compressor to compress air to form compressed air and directing exhaust of the natural gas engine to the heat exchanger. The method includes heating the compressed air in the heat exchanger using the exhaust of the natural gas engine to form heated compressed air and injecting the heated compressed air into the combustor case of the gas turbine.

A system and method for increasing power output of a gas turbine. A method of increasing a power output of a gas turbine comprises providing an auxiliary system configured to be coupled to the gas turbine. The auxiliary system includes a natural gas engine, a compressor, and a heat exchanger fluidly coupled to the compressor. The method includes fluidly coupling the auxiliary system to a combustor case of the gas turbine. The method comprises operating the natural gas engine to drive the compressor to compress air to form compressed air and directing exhaust of the natural gas engine to the heat exchanger. The method includes heating the compressed air in the heat exchanger using the exhaust of the natural gas engine to form heated compressed air and injecting the heated compressed air into the combustor case of the gas turbine.

An assembly is provided for a turbine engine with an axial centerline. This assembly includes a turbine engine structure and a valve assembly. The turbine engine structure includes an outer duct wall, an inner duct wall, a first flow path and a second flow path. The inner duct wall is radially inward of the outer duct wall. The first flow path is radially inward of the inner duct wall. The second flow path is radially outward of the inner duct wall and is radially inward of the outer duct wall. The valve assembly includes a valve element and a valve actuator. The valve element is configured to regulate flow of fluid between the first flow path and the second flow path. The valve actuator is configured to move the valve element. The valve actuator is positioned entirely radially outward of the outer duct wall.