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.

Linear-quadratic Gaussian with loop-transfer recovery methodology for the F-100 engine

Abstract: The design of a multivariable feedback control system for the F-100 turbofan jet engine is a challenging task for control engineers. This paper employs a linearized model of the F-100 engine to demonstrate the use of the newly developed linear-quadratic Gaussian with loop-transfer recovery design methodology that adopts an in- tegrated frequency and time-domain approach to multivariable feedback control synthesis so as to meet stability robustness, command following, and disturbance rejection specifications. ODERN turbofan jet engines represent an important multiple-input/multiple-output (MIMO) control ap- plication area since the dynamic coordination of fuel flow and several engine geometry variables can lead to improved performance and efficiency, while maintaining safe fan and compression stall margins. Indeed, the MIMO feedback con- trol of turbofan and turboshaft engine has received a great deal of attention in the past few years.1"8 The F-100 turbofan engine was used as a main design exam- ple for which different MIMO control methodologies were employed. The so-called linear-quadratic-regulator (LQR) ap- proach9'10 was the basis of engineering designs and evaluations1"4 that required the feedback of several F-100 state variables. In the past five years significant advances have been made in integrating time-domain optimization-based approaches (such as LQR and linear-quadratic Gaussian (LQG)) with fre- quency domain approaches. Such an integrated frequency- domain and state-space approach to MIMO control systems design was pioneered by Stein and his colleagues11"14 and has culminated to the so-called linear-quadratic Gaussian with loop-transfer recovery (LQG/LTR) methodology for MIMO feedback control synthesis. The primary objective of this paper is to illustrate the LQG/LTR design methodology using a four-input/fou r- output linear model of the F-100 engine. Specifically, we stress how MIMO command following and disturbance rejection performance specifications, as well as stability robustness specifications are naturally posed in the frequency domain us- ing the singular values of suitably defined loop-transfer matrices. Then, we demonstrate how the LQG/LTR design procedure is used to meet the posed specifications. Further-

Turbofan engine control design using robust multivariable control technologies

Abstract: A unified robust multivariable approach to propulsion control design has been developed at NASA Glenn Research Center. The critical elements of this unified approach are: a robust H/sub /spl infin// control synthesis formulation; a simplified controller scheduling scheme; and a new approach to the synthesis of integrator windup protection gains for multivariable controllers. This paper presents results from an application of these technologies to control design for linear models of an advanced turbofan engine. The objectives of the study were to transfer technology to industry and to identify areas of further development for the technology. The technology elements and industrial development of tools to implement the steps are described with respect to their application to a GE variable-cycle turbofan engine. A set of three-input/three-output three-state linear engine models was used over a range of power levels covering engine operation from idle to maximum unaugmented power. Results from simulation evaluation are discussed and insight is provided into how the design parameter choices affect the results.

Auxiliary power and thrust unit

Abstract: An improvement to an aircraft is provided in the form of an aircraft auxiliary power and thrust unit located in the tail cone of the aircraft. The unit includes a turbofan engine, an air intake opening, an inlet duct extending between the air intake opening and the turbofan engine, a transmission assembly, and various auxiliary equipment. The engine includes a forward-facing main turbine shaft. The air intake opening is located in the tail cone at a body station location forward of the engine. The transmission assembly includes a drive shaft mounted axially to the main turbine shaft and extends forward through the inlet duct through a sealed opening in the inlet duct. The auxiliary equipment is also located in the tail cone, forward of the turbofan engine. The transmission assembly is releasably connected to the auxiliary equipment. In a first operating mode, the engine is operated at a low setting to power the auxiliary equipment. In a second operating mode, the turbofan engine is used to provide thrust and operate auxiliary equipment.

Operation of Gas Turbine Engines in Volcanic Ash Clouds

Abstract: Results are reported for a technology program designed to determine the behavior of gas turbine engines when operating in particle-laden clouds. There are several ways that such clouds may be created, i.e., explosive volcanic eruption, sand storm, military conflict, etc. The response of several different engines, among them the Pratt & Whitney JT3D turbofan, the Pratt & Whitney J57 turbojet, a Pratt & Whitney engine of the JT9 vintage, and an engine of the General Electric CF6 vintage has been determined. The particular damage mode that will be dominant when an engine experiences a dust cloud depends upon the particular engine (the turbine inlet temperature at which the engine is operating when it encounters the dust cloud), the concentration of foreign material in the cloud, and the constituents of the foreign material (the respective melting temperature of the various constituents). Further, the rate at which engine damage will occur depends upon all of the factors given above, and the damage is cumulative with continued exposure. An important part of the Calspan effort has been to identify environmental warning signs and to determine which of the engine parameters available for monitoring by the flight crew can provide an early indication of impending difficulty. On the basis of current knowledge, if one knows the location of a particle-laden cloud, then that region should be avoided. However, if the cloud location is unknown, which is generally the case, then it is important to know how to recognize when an encounter has occurred and to understand how to operate safely, which is another part of the Calspan effort.