High-Pressure Fan Design for Biogas Plants
High-pressure fans for thermal power generation stations, especially biogas plants, usually operate in a spiral casing at high pressures of about p=12,000 - 15,000 Pa and low flow rates of around Q=100 - 600m³/s. The motor drive has a constant speed of 3,000l/min. This corresponds to specific speeds of nq=3 - 6 min-l, which is already beyond the conventional range of single-stage radial machines.
Nowadays these fans for biogas plants usually operate at higher flow rates than specified or are multiple stage radial fans. Therefore a new class of radial impellers has been developed. These single-stage impellers have a unique high pressure at a low flow rate operating point.
In this work several impellers of this new class have been designed and validated with a commercial Navier-Stokes solver (ANSYS CFX). The design process is described in detail. It is based on a new extended analytical and numerical design method. It is shown that the prescribed unusual operating point can be achieved with single-stage radial impellers. An in-detail flow analysis is given showing the fundamental flow physics of these impellers.
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