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.

Engine cycle and exhaust configuration for quiet supersonic propulsion

Abstract: The thermodynamics and acoustics of a fixed-cycle, bypass ratio 3 supersonic engine with an innovative noise suppression scheme is explored. The silencing method entails installation of variable turning vanes in the bypass exhaust of a separate-flow turbofan engine. During noise-sensitive segments of flight, the vanes impart a slight downward tilt to the bypass plume relative to the core plume, thus thickening the bypass stream on the underside of the jet. This results in a reduction of the convective Mach number of instability waves that produce intense downward sound radiation. Subscale experiments show that, relative to the mixed-flow exhaust, the coaxial separate-flow exhaust with vanes reduces the peak overall sound pressure level by 8 dB and the effective perceived noise level by 7 dB. The noise-equivalent specific thrust on takeoff is reduced from 490 to 390 m/s. Compared to a current-generation low-bypass turbofan engine, the bypass ratio 3 engine is estimated to be 13 dB quieter with the mixed-flow exhaust and 20 dB quieter with the aforementioned suppression scheme. The vane configuration of this study is estimated to cause a thrust loss of 1% at takeoff and 0.25% at supersonic cruise.

Measurements of Turbulent Flow Field in Separate Flow Nozzles with Enhanced Mixing Devices - Test Report

Abstract: As part of the Advanced Subsonic Technology Program, a series of experiments was conducted at NASA Glenn Research Center on the effect of mixing enhancement devices on the aeroacoustic performance of separate flow nozzles. Initial acoustic evaluations of the devices showed that they reduced jet noise significantly, while creating very little thrust loss. The explanation for the improvement required that turbulence measurements, namely single point mean and RMS statistics and two-point spatial correlations, be made to determine the change in the turbulence caused by the mixing enhancement devices that lead to the noise reduction. These measurements were made in the summer of 2000 in a test program called Separate Nozzle Flow Test 2000 (SFNT2K) supported by the Aeropropulsion Research Program at NASA Glenn Research Center. Given the hot high-speed flows representative of a contemporary bypass ratio 5 turbofan engine, unsteady flow field measurements required the use of an optical measurement method. To achieve the spatial correlations, the Particle Image Velocimetry technique was employed, acquiring high-density velocity maps of the flows from which the required statistics could be derived. This was the first successful use of this technique for such flows, and shows the utility of this technique for future experimental programs. The extensive statistics obtained were likewise unique and give great insight into the turbulence which produces noise and how the turbulence can be modified to reduce jet noise.

Turbofan engine thrust reverser

Abstract: A turbofan engine thrust reverser comprising a plurality of pivotally mounted duct members forming an integral part of the engine cowl. These members redirect the exhaust air of the fan forward and outward at such velocity and angle that the suction of the engine inlet is insufficient to cause reingestion.

Aligned and Unaligned Coherence: A New Diagnostic Tool

Abstract: The study of combustion noise from turbofan engines has become important again as the noise from other sources like the fan and jet are reduced. A method has been developed to help identify combustion noise spectra using an aligned and unaligned coherence technique. When used with the well known three signal coherent power method and coherent power method it provides new information by separating tonal information from random process information. Examples are presented showing the underlying tonal structure which is buried under broadband noise and jet noise. The method is applied to data from a Pratt and Whitney PW4098 turbofan engine.

Integrated fan/low pressure compressor rotor for gas turbine engine

Abstract: This invention concerns a turbofan gas turbine engine with an integrated fan and low pressure compressor rotor which is mounted to a forward end of the shaft immediately upstream of a one piece engine support structure (20). The fan blade portion (30) and compressor blade portion (31) have aerodynamically aligned lateral airfoil surfaces and platforms enabling a single integrated rotor to replace prior art separate blades thereby simplifying the engine design and reducing the axial length of the engine.