A valve opening degree determination device includes an object operating state acquisition unit configured to acquire an object operating state which is an operating state of a gas turbine before control, and a valve opening degree calculation unit configured to calculate the valve opening degree such that a disk cavity temperature after control is equal to or lower than a target temperature, based on the object operating state. The valve opening degree calculation unit is configured to determine an input value of the valve opening degree such that a prediction value of the disk cavity temperature is equal to or lower than the target temperature as the valve opening degree, based on a prediction model generated based on a plurality of previous data in which the operating state, the disk cavity temperature, and an actual opening degree of the cooling-air adjustment valve previously acquired are associated with each other.

A method of mitigating contrails produced by an aircraft having a set of gas turbine engines, comprises the steps of (i) for each engine in a first subset of the engines, reducing the operating efficiency of the engine to produce a reduction in thrust provided by that engine and (ii) for each engine in a second subset, increasing the fuel flow to the engine to increase the thrust provided by that engine, the set of at least two gas turbine engines consisting of the first and second subsets. The method provides for contrail mitigation action by means of engine operating efficiency reduction to be directed to a first subset of engines for which contrail mitigation per unit engine operating efficiency reduction is greatest, the resulting reduction in thrust provided by such engines being at least partially compensated by increasing fuel flow to engines of the second subset.

A secondary air system (SAS) of an aircraft engine that produces secondary airflow from a source of secondary air includes a hollow strut and one or more SAS feed pipes upstream thereof. The hollow strut extends radially through the main gas path of the engine and defines therein a strut conduit extending between a strut inlet and a strut outlet at opposite ends of the hollow strut. The strut outlet is in fluid flow communication with a buffer cavity for feeding the secondary airflow to the engine core. The SAS feed pipe includes an inlet receiving the secondary airflow from the source of secondary air, and an outlet in fluid flow communication with the strut inlet to feed the secondary airflow into the strut conduit. The SAS feed pipe has a sonic orifice therein, between the inlet and the outlet thereof.

A gas turbine engine includes a compressor section, a combustor section, and a turbine section operably coupled to the compressor section. A primary flow path is defined through the compressor section, the combustor section, and the turbine section. An engine case surrounds the compressor section, the combustor section, and the turbine section. The gas turbine engine also includes a means for providing an active variable cooling flow through a bypass duct external to the engine case to a secondary flow cavity of the turbine section.

A multi-engine system includes a first gas turbine engine that includes a first compressor and a first turbine. The multi-engine system may further include a second gas turbine engine that has a second compressor and a second turbine. Still further, the multi-engine system may include a first crossover cooling network configured to route a first crossover airflow from the first compressor of the first gas turbine engine to the second turbine of the second gas turbine engine and a second crossover cooling network configured to route a second crossover airflow from the second compressor of the second gas turbine engine to the first turbine of the first gas turbine engine.

The auxiliary duct can branch radially outwardly from the bypass duct, have a proximal end fluidly connecting the bypass duct and a distal end, a valve can be activatable to selectively open and close the auxiliary passage, and a structure can protrude partially from the auxiliary duct into the auxiliary passage, the structure spaced apart from the proximal end, between the proximal end and the valve, the structure generating lesser pressure losses when flow in the auxiliary passage is directed towards the distal end than when the flow is directed towards the proximal end.

The auxiliary duct can branch radially outwardly from the bypass duct, have a proximal end fluidly connecting the bypass duct and a distal end, a valve can be activatable to selectively open and close the auxiliary passage, and a structure can protrude partially from the auxiliary duct into the auxiliary passage, the structure spaced apart from the proximal end, between the proximal end and the valve, the structure generating lesser pressure losses when flow in the auxiliary passage is directed towards the distal end than when the flow is directed towards the proximal end.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.

In accordance with at least one aspect of this disclosure, there is provided a system for an aircraft engine. In embodiments, the system includes an accessory box and a fuel accessory located in an interior space within the accessory box, where a vent is defined through a wall of the accessory box. In embodiments, the vent includes a plurality of holes or slots in an outer wall of the accessory box for passage of gaseous fuel from the interior space. In embodiments, the vent is configured for passive ventilation of the interior space.