A gas turbine engine for an aircraft includes an engine core including a first, lower pressure, turbine, a first compressor, and a first core shaft connecting the first turbine to the first compressor; and a second, higher pressure, turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor, and a fan located upstream of the engine core and comprising a plurality of fan blades extending from a hub. First and second turbine entrance and exit temperatures are defined as average temperature of airflow at the entrance or exit to the respective turbine at cruise conditions. A low pressure turbine temperature change is defined as:

[00001]$\frac{\mathrm{the}.Math..Math.\mathrm{first}.Math..Math.\mathrm{turbine}.Math..Math.\mathrm{entrance}.Math..Math.\mathrm{temperature}}{\mathrm{the}.Math..Math.\mathrm{first}.Math..Math.\mathrm{turbine}.Math..Math.\mathrm{exit}.Math..Math.\mathrm{temperature}}.$

A high pressure turbine temperature change is defined as:

[00002]

A gas turbine engine has a fan section including a fan, a compressor section including a low pressure compressor and a high pressure compressor, a turbine section including a low pressure turbine and a high pressure turbine, and a gear reduction. The low pressure compressor and the low pressure turbine have a number of blades in each of at least one of a plurality of blade rows. The blades are rotatable at least some of the time at a rotational speed in operation. The number of blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine: 5500(number of bladesrotational speed)/6010000, the rotational speed being in revolutions per minute.

A gas turbine engine (10) comprises a bypass duct cowl (21), an engine core housing (22) defining an engine core inlet, a bypass fan (13) and a plurality of outlet guide vanes (24). Each outlet guide vane 24 extends between a radially inner surface of the bypass duct cowl (21) and a radially outer surface of the engine core housing (22, 23) to define an outlet guide vane span (SPANOGV). The outlet guide vanes (24) are configured to support the engine core housing (22, 23) relative to the bypass duct cowl (21). The bypass fan (13) and an engine core inlet (34) define a bypass ratio between 10 and 17, and a ratio of the outlet guide vane span (OGVSPAN) to a bypass fan radius (RFAN) is between 0.45 and 0.55.

A turbofan engine is provided. The turbofan engine includes a low pressure spool; a fan mechanically coupled with the low pressure spool; a high pressure spool; an accessory gearbox mechanically coupled with the high pressure spool; a hydraulic pump mechanically coupled with the accessory gearbox; and one or more heat exchangers tied to the accessory gearbox, the one or more heat exchangers having a heat exchanger capacity defined by a product raised to a half power, the product being determined by multiplying an average heat exchanger effectiveness of the one or more heat exchangers by a heat conductance factor that relates an accessory gearbox heat load, a hydraulic pump power of the hydraulic pump, a fan diameter of the fan, an engine length of the turbofan engine, and an overall pressure ratio of the turbofan engine.

A turbomachinery engine comprises a ducted fan, a high-pressure compressor, a low-pressure turbine, a gearbox, and a ducted engine correlation parameter (DECP). The DECP is within a range of 0.10-0.25 and is defined as 10*D/GR/N.sub.LPT/N.sub.HPC, where D is a fan blade tip diameter at a leading edge of the ducted fan measured in feet, GR is a gear ratio of the gearbox, N.sub.LPT is a stage count of the low-pressure turbine, and N.sub.HPC is a stage count of the high-pressure compressor.

Systems and methods for improved gas turbine engine performance are disclosed. The method can include receiving an error function for a wide range of fuels. The error function can provide lower heating value (LHV) corrections over the wide range of fuels. The method can include receiving gas turbine engine operation data for a first period of run time on the gas turbine from one or more sensors of the gas turbine engine. The engine operation data can include a performance data points. The method can include determining an optimum LHV based on the engine operation data for the first period of run time and the error function. The method can then include adjusting fuel consumption of the gas turbine engine based on the optimum LHV.

An evaporative cooling pack formed from first and second corrugated media sheets is provided. The evaporative cooling pack cools a flow of air using a cooling fluid. The first and second corrugated media sheets have flutes that extend at different angles relative to a reference line and at such relative angles and have flute pitches that inhibit nesting of the adjacent sheets.

Herein provided are methods and systems for operating a gas-turbine engine comprising a gearbox and a power turbine coupled to the gearbox. A first torque at the gearbox is obtained via a sensor. A second torque at the power turbine is determined based on the first torque. A power at the power turbine is determined based on the second torque. Operation of the engine is controlled based on the power.

A turbomachine engine can include a fan assembly, a vane assembly, a core engine, a gearbox, and an overall engine efficiency rating. The fan assembly can include a plurality of fan blades. The vane assembly can include a plurality of vanes, and the vanes can, in some instances, be disposed aft of the fan blades. The core engine can include a low-pressure turbine. The gearbox includes an input and an output. The input of the gearbox is coupled to the low-pressure turbine of the core engine and comprises a first rotational speed, the output of the gearbox is coupled to the fan assembly and has a second rotational speed, and a gear ratio of the first rotational speed to the second rotational speed is within a range of 2.0-4.0. The overall engine efficiency rating is greater than or equal to 0.35GR.sup.1.5 and less than or equal to 0.7GR.sup.1.5.

A turbomachine engine can include a fan assembly, a vane assembly, a core engine, a gearbox, and an overall engine efficiency rating. The fan assembly can include a plurality of fan blades. The vane assembly can include a plurality of vanes, and the vanes can, in some instances, be disposed aft of the fan blades. The core engine can include a low-pressure turbine. The gearbox includes an input and an output. The input of the gearbox is coupled to the low-pressure turbine of the core engine and comprises a first rotational speed, the output of the gearbox is coupled to the fan assembly and has a second rotational speed, and a gear ratio of the first rotational speed to the second rotational speed is within a range of 2.0-4.0.