Axial compressor

About: Axial compressor is a research topic. Over the lifetime, 12035 publications have been published within this topic receiving 127766 citations.

Physics of Airfoil Clocking in a High-Speed Axial Compressor

Abstract: Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and inviscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, as the Mach number increases the interaction between blade rows can be intensified due to potential effects. In the current study an unsteady, quasi-three-dimensional Navier-Stokes analysis has been used to investigate the unsteady aerodynamics of stator clocking in a 1-1/2 stage compressor, typical of back stages used in high-pressure compressors of advanced commercial jet engines. The effects of turbulence have been modeled with both algebraic and two-equation models. The results presented include steady and unsteady surface pressures, efficiencies, boundary layer quantities and turbulence quantities. The main contribution of the current work has been to show that airfoil clocking can produce significant performance variations at the Mach numbers associated with an engine operating environment. In addition, the growth of turbulence has been quantified to aid in the development of models for the multistage steady analyses used in design systems.

Unitary simple/bootstrap air cycle system

Abstract: 1,204,734. Air turbine, compressor and fan assembly. UNITED AIRCRAFT CORP. May 13, 1968 [June 2, 1967], No.22514/68. Heading F1G. The invention relates to a compressor and turbine assembly, such as used for supplying air to an aircraft cabin, the assembly comprising a shaft rotatably mounted in a bearing assembly, a fan rotor mounted at one end of the shaft, a compressor rotor mounted at the other end of the shaft, a turbine rotor mounted on the shaft between the fan and compressor rotors, the turbine having an axial outlet adjacent the bearing assembly, the turbine outlet being so disposed that the air discharging from the turbine serves to cool the bearing assembly. In the embodiment shown, a shaft is supported in a bearing assembly 24, an axial flow fan rotor 36 being mounted at one end of the shaft, a centrifugal compressor rotor 6 being mounted at the other end of the shaft, and a radial inward flow turbine rotor 18 being mounted adjacent the compressor rotor. Bleed air is supplied from a source 2 to the inlet 4 of the compressor, the air at increased pressure and temperature passing to heat exchanger 12 where it is cooled by flow of ambient air. The cooled air then passes to turbine inlet 16 and is expanded through the turbine 18, the turbine driving the compressor 6 and the fan 36. The air discharging from the turbine at low-pressure and temperature passes to chamber 22 where it serves to cool the bearing assembly 24. The air then passes through line 28 to a point of use such as an aircraft cabin. A portion of air from the source 2 passes through line 32 under control of valve 30 to mix with the air in the space 22 thus preventing formation of ice due to the low temperature of the turbine exhaust air; alternatively air may be taken from the heat exhanger outlet 14 for this purpose. The axial flow fan 36 draws in ambient air at 34 the air passing through heat exchanger 12, through the inlet 40 to the fan and discharges through outlet 44.

Endwall profiling for the reduction of secondary flow in turbines

Abstract: This thesis describes investigations into the use of a technique for improving the efficiency of axial flow turbines. The flow in the turbine component of axial flow machines is complex, with a number of three-dimensional features. In order to extract power from a stream of high pressure and high temperature flow this flow must be turned through a large angle, this high turning introduces a phenomenon know as "secondary flow". This secondary flow introduces additional loss, unsteadiness and regions of high heat transfer into the machine - all of which are undesirable features. Endwall profiling aims to reduce these undesirable features by shaping the end-wall between the turbine blades. The shaping either accelerates the flow which reduces the local static pressure or retards the flow which increases the static pressure. These effects are confined to a region near the endwall so the overall performance of the blade row is not affected. However due to the complexity of the flow it is easy to make things worse rather than better! - careful design is needed. This thesis aims to understand how and why the reductions in may be achieved so that they can be better exploited as well as providing information of the performance of a major engine manufacturers design system. The thesis describes pressure probe measurements inside and outside of the blade passage of a low speed linear cascade with a number of profiled endwall geometries. The aerofoils used in the cascade are already relatively efficient and the overall loss changes are small, accurate measurement is therefore very difficult. The current best profiled endwall reduces secondary loss by 30%±5% compared to the planar case. Hot film measurements have been conducted on the endwalls and suction surface of the blade to determine if these benefits are substantially due to changing the boundary layer state. The results from this thesis indicate that this is not the case. This thesis describes measurements on three generations of profiled endwalls, two of which successfully reduce loss, one does not. The success of the first two endwalls indicates the power of current CFD based design practices, the failure of the third design to reduce loss illustrates some of the shortcomings of current CFD based design practices. The information from this thesis is being used in the design of the next generation of aircraft engines to which non-axisymmetric profiled endwalls are being fitted.