An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-throughflow, axial transonic fan is presented. Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation, which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three dimensional and swept, with the shock becoming normal to the endwall near the shroud.
An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-through-flow, axial transonic fan is presented. Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three-dimensional and swept, with the shock becoming normal to the endwall near the shroud.
The Goodrich Integrated Mechanical Diagnostics Health and Usage System (IMD-HUMS) 1 , 2 mechanical diagnostics functionality is the integration of disparate subsystems. When the aircraft is in the appropriate capture window, the primary processing unit (PPU) commands the vibration processing unit (VPU) to capture vibration data and a tachometer reference. This time domain data is processed by standard and proprietary algorithms to generate component condition indicators (CI). These CI are statistics, which when used with a priori configuration data, are mapped into component health indicators (HI). The VPU passes the component HI data to both the PPU and the data transfer unit for ground station display. The PPU, taking the HI data for a component, can determine if the component has a degraded health state. If the component is degraded, the PPU can generate an exceedance message to be reviewed during maintenance debrief. After the flight, all CI and HI data are stored in a data base and is available for display against an aircraft, composite component (e.g. line replaceable unit) and the component itself. The acquisition process is complicated by noise from internal sources (non synchronous gears, shafts and bearing not under analysis) and external sources (changes in airspeed, torque, weight, etc). The HI becomes, in essence, a statistical indicator of the components health. As such, the best estimator of component health is calculated using a Kalman filter. This reduces variance in the data prior to display of the component HI to the aircraft operator. This filtered HI is called the DHI (Display Health Indicator). The DHI uses a priori information and sampling theory to build the best available representation of health of the component. 1 1 0-7803-9546-8This paper addresses the system engineering required to integrate the vibration processing, decision algorithms, thresholding and filtering to give the operator the best representation of component health. The integration of the system allows IMD-HUMS to have a high degree of certainty in the information given to the operator. This information could potentially improve maintenance practices, lowing aircraft operating cost while improving aircraft safety. The system engineering insures that the recommendation for component maintenance has a low probability of false alarm while maintaining a high probability of component fault detection.
Seal technology development is an important part of the military senices' activities in the Integrated High Performance Turbine Engine Technology (IHPTET) initiative, the joint DOD, NASA, ARF'A, and industry endeavor to double W i n e engine capabilities by the turn of the century. Significant performance and efficiency improvements can be obtained through reducing engine internal flow system leakage. However, seal environment requirements continue to become more extremc as the engine thermodynamic cycles advance towards the IHPTET goals. The military pursuit of low leakage seal technology has focused on increasing the temperature, speed, and pressure drop capabilities in a manner consistent with the IHPTET needs. The new NASA Advanced Subsonic Technology (AST) Initiative seeks to reduce large and regional commercial turbofan fuel consumption by more than eight percent and ten percent, respectively. The component performance goals for the AST Initiative parallel those of MPTET, in also rcquiring seals to perform under challenging surface speeds and operating temperatures. The technology being developed by the military clearly offers great potential for dual use with thc commercial sector. This paper briefly describes past and current military seal research and development programs, and summarizes seal applications in military demonstrator and developmental engines. v
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.