Performance Parameters of Jet Engines

Abstract

The designer of an aircraft engine must recognize the differing requirements for take-off, climb, cruise, and maneuvering. The relative importance of these being different for civil and military applications and for long-and short-haul aircrafts. In the early aircrafts, it was common practice to focus on the take-off thrust. This is no longer adequate for later and present day aircrafts. For long-range civil transports like Boeing 747, 777, 787 and Airbus A 340, A380 (the world's truly double-deck airliner), A350 XWB (extra wide body), the fuel consumption through some 10 or more flight hours is the dominant parameter. Military aircrafts have numerous criteria like the rate of climb, maneuverability for fighters, short take-off distance for aircrafts operating from air carriers, maximum ceilings for high altitude reconnaissance aircrafts like SR-71 Blackbird aircrafts. For civil and military freighter airplanes, the maximum payload is its main requirement.In all types of aircrafts, the engines are requested to provide efficiently the thrust force necessary for their propelling during different flight phases and at different operating conditions including hottest/coldest ambient temperature and rainy/ windy/snowing weather.This chapter resembles a first window for air breathing engines. It starts by a derivation for the thrust force or the propelling force generated in the direction opposite to the flow of air entering the engine in accordance with Newton's laws of motion. Consequently, all jet engines including rocket motors belong to the class of power plants called reaction engines. It is the internal imbalance of forces within the gas turbine engines that give all reaction engines their names. The propulsive force developed by a jet engine is the result of a complex series of actions and reactions that occur within the engine. The thrust constituents and the different factors affecting the thrust are next explained. Some of these factors are related to the engine, others are related to the medium in which the engine operates.

Investigation of the Relationship between Degradation of the Coating of Gas Turbine Blades and Its Surface Color

“…Furthermore, the proposed approach allows for a non-invasive indirect assessment of the technical condition of operational blades without having to remove them from the turbine and deconstructing them, thus extending their service life or decommissioning them before they cause engine failure. Blades are often made of nickel-based alloys, which are characterized by good microstructure stability as well as good mechanical and thermal properties [14][15][16]. However, these alloys are stable only to a certain average temperature, and when it is exceeded, their desired mechanical properties start to decline [17][18][19].…”

“…The value of the total temperature depends on the static temperature, the square of the velocity of exhaust gas flow, enthalpy, and the gas constant of these exhaust gases [37]. Blades are often made of nickel-based alloys, which are characterized by good microstructure stability as well as good mechanical and thermal properties [14][15][16]. However, these alloys are stable only to a certain average temperature, and when it is exceeded, their desired mechanical properties start to decline [17][18][19].…”

“…To prevent blades from reaching this temperature, heat-resistant coatings exhibiting resistance to high-temperature corrosion, low thermal conductivity, and high structural stability [20][21][22] as well as possessing internal cooling systems [23][24][25] are frequently used. Blade operating conditions force designers to use nickel alloys that are resistant to high heat and high-temperature creep, high-temperature sulfuric corrosion, thermal wear, overheating, and especially creep [14,15,26,27]. Various phenomena that can deteriorate the condition of blades can occur within the operational process.…”

Assessing the Condition of Gas Turbine Rotor Blades with the Optoelectronic and Thermographic Methods

“…The technical condition of turbine blades in the operating process of aviation turbojet engines is of decisive importance for the reliability and durability of a turbine and the entire engine [1,2]. The main reason gas turbine blades get damaged is overheating of their material as well as thermal fatigue [3][4][5].…”