Turbofan

About: Turbofan is a research topic. Over the lifetime, 4114 publications have been published within this topic receiving 39490 citations. The topic is also known as: fanjet & turbofan engine.

Back-up control system for F101 engine and its derivatives

Abstract: A back-up control system is implemented in a single engine aircraft to provide the inactivation of a faulty primary system and engagement of a secondary system, and thereby provide a means of maintaining controllable flight sustaining thrust. The aircraft's hydromechanical main engine control and its companion pressure and temperature sensors can develop faults which can result in the inability of the engine to deliver flight sustaining thrust. The electronic control contains logic functions which indicate failure of the main engine control when all of the following exists for a minimum of three seconds: (a) the power lever is at a position requesting a level of dry thrust which exceeds a predetermned threshold; (b) core engine speed is below that required to deliver the predetermined level of dry thrust; (c) core engine speed is not increasing; and (d) turbine temperature is beneath the maximum allowable limit. The back-up system is used in conjunction with a three position cockpit switch having "normal", "on" and "standby" positions. In the "normal" position the back-up system is off and must be manually activated by switching to the "on" position. In the "standby" position, the back-up system is automaticlly activated when the necessary conditions occur.

Noise suppressor for turbo fan jet engines

Abstract: A noise suppressor for installation on the discharge or aft end of a turbo fan engine. Within the suppressor are fixed annular airfoils which are positioned to reduce the relative velocity between the high temperature fast moving jet exhaust and the low temperature slow moving air surrounding the same. Within the suppressor nacelle is an exhaust jet nozzle which constrains the shape of the jet exhaust to a substantially uniform elongate shape irrespective of the power setting of the engine. Fixed ring airfoils within the suppressor nacelle therefore have the same salutary effects irrespective of the power setting at which the engine is operated.

Modeling Commercial Turbofan Engine Icing Risk with Ice Crystal Ingestion

Abstract: The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As ice crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the ice crystals to melt. It is hypothesized that this allows the ice-water mixture to cover the metal surfaces of the compressor stationary components which leads to ice accretion through evaporative cooling. Ice accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine icing computational tool to simulate the flow through a turbofan engine and assess the risk of ice accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual ice accretion. A commercial turbofan engine which has previously experienced icing events during operation in a high altitude ice crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous ice cloud which are ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was ice accretion in the engine due to ice crystal ingestion, at the same simulated altitude operating conditions as experienced previously in flight. The computational tool was utilized to help guide a portion of the PSL testing, and was used to predict ice accretion could also occur at significantly lower altitudes. The predictions were qualitatively verified by subsequent testing of the engine in the PSL. The PSL test has helped to calibrate the engine icing computational tool to assess the risk of ice accretion. The results from the computer simulation identified prevalent trends in wet bulb temperature, ice particle melt ratio, and engine inlet temperature as a function of altitude for predicting engine icing risk due to ice crystal ingestion.

Approach of modeling continuous turbine engine operation from startup to shutdown

Abstract: A generalized turbine engine start simulation (mathematical model) has been developed and demonstrated. The model, designated as ATEST-V3, is capable of simulating engine operation continuously from near static (zero speed) conditions to maximum engine power including windmill starting, spooldown starting, and starterassisted starting. The enhanced capability to simulate the engine starting process provides the means to characterize and understand engine system operational behavior during critical startup and shutdown operations. ATEST-V3 is based on an aerothermodynamic matching of the major components. The component-matching technique is widely used for steady-state and transient turbine engine simulations that typically exclude subidle and starting operations. The same approach is shown to be applicable to engine starting operations by modeling component behavior continuously from zero to maximum power. The combination of an existing transient engine simulation and a numerically stable component-matching algorithm provided a foundation for extending the simulation capability to subidle engine operation and engine starting. ATEST-V3 was applied to a modern flighttype turbofan engine which demonstrated the capability to simulate windmill, spooldown, and starter-assisted starts at various flight conditions. Finally, a comparison is made between model results and engine test data.