Diffuser (thermodynamics)

About: Diffuser (thermodynamics) is a research topic. Over the lifetime, 6731 publications have been published within this topic receiving 54738 citations.

The Experimental Study of Matching Between Centrifugal Compressor Impeller and Diffuser

Abstract: The centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system, consisting of the diffuser and scroll, showed that there were four possible combinations of characteristics of impeller pressure ratio and diffusing system pressure ratio. The flow rate, Q P , where the impeller achieved maximum static pressure ratio, was surge flow rate of the centrifugal compressor determined by the critical flow rate. In order to operate the compressor at a rate lower than Qp, the diffusing system, whose pressure recovery factor was steep negative slope near Q P , was needed. When the diffuser throat area was less than a certain value, the compressor efficiency deteriorated ; however, the compressor stage pressure ratio was almost constant. In this study, by reducing the diffuser throat area, the compressor could be operated at a flow rate less than 40 percent of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off-design speeds showed that the irregularities in surge line occurred when the component that controlled the negative slope on the compressor stage pressure ratio changed.

Pressure recovery improvement in a conical diffuser with swirling flow using water jet injection

Abstract: The variable demand of the energy market forces that hydraulic turbine to work at different regimes, which includes the regimes far from and the best efficiency point. In particular, for fixed-pitch blades runners, the efficiency of the turbine rapidly deteriorates at off-design operating points. Moreover, in the discharge cone downstream the runner a precessing helical vortex (called vortex rope) is developed, with associated severe pressure fluctuations. This vortex rope produces large vibrations in the hydraulic system, breakdowns of the runner blades or leads to power swing phenomenon. A novel method to mitigate the vortex rope was introduced by Resiga et al., by injecting an axial water jet from the runner crown downstream into the draft tube cone. The experimental and numerical investigations presented in this paper clearly show that the jet injection approach significantly increases the pressure recovery in the conical diffuser with swirling flow while reducing the hydraulic losses.

Centrifugal compressor with rotating vaneless diffuser powered by leakage flow

Abstract: The high velocity leakage flow escaping tangentially through the annular clearance space between the impeller and rotating vaneless diffuser in a centrifugal compressor is employed to drive a turbine device attached to the diffuser back wall member, thereby self-powering the rotating diffuser and reducing the leakage flow. Either a turbine blade row sector with a partial arc of admission or a full admission turbine blade row can be used.

Description and preliminary calibration of a low-density, hypervelocity wind tunnel

Abstract: : A small, low-density, hypervelocity, continuous wind tunnel operating at total temperatures from 2000 to 4000 K is described, and initial experiments designed to determine the characteristics of the flow are discussed Effects of low Reynolds numbers on impact-pressure probes and static-pressure probes are shown Preliminary work with a probe for measuring local mass-flow rate is outlined, and results are shown to be in agreement with impact and static pressure measurements Axial and transverse surveys of flow in the nozzle are presented to illustrate the extent of boundary-layer growth and the useable core of flow A diffuser is proved to be advantageous, even though very low Reynolds numbers are typical of the tunnel A comparison of data on drag of spheres, including measurements from the new wind tunnel, is presented