Shape Optimization of a Regenerative Blower Used for Building Fuel Cell System ()
1. Introduction
Shape optimization of a regenerative blower used in a building fuel cell system has been performed to enhance the performance of a blower in the present study. A regenerative blower is widely used in the industrial fields: flow circulator of waste water in a sewage disposal tank, BOP of a fuel cell system, core part of medical equipment, and so on. The blower needs high pressure and constant flow rates. According to the shapes of blower’s impellers, the blower has two types of impellers: the open and side channel type. Open channel type impeller is widely selected in the industrial fields due to relatively lower manufacturing costs. Design of a high efficient blower is very important to get higher exit pressure.
Optimal shape design of a regenerative blower is recently introduced to enhance the performance of a regenerative blower [1-3]. Characteristic of design parameters was reported by some researchers [1,3]. They showed that optimal shape design on an impeller and a casing could increase the performance of the blowers.
Recently optimal design method using response surface method (RSM) [4] combined with three-dimensional Navier-Stokes solver is widely used to find optimum shapes of a blower. The RSM is global optimization and can find easily optimal position using the results. The method also can utilize information collected from various sources, thus effective for both of singleand multidisciplinary optimization problems [5].
In the previous study, Jang and Han [2] tried to optimize the shape of impeller for two stage ring blower by RSM combined with numerical simulation.
In the present study, the response surface method (RSM) is introduced to find optimal shape of a regenerative blower used in a building fuel cell system. Two design variables determining extension angle and blade number are used. Pressure and efficiency of the blower are selected as an objective function. Detailed internal flow analysis is also performed and compared with the reference blower.
2. Regenerative Blower
A regenerative blower used for a building fuel cell system is introduced in the present study. The detailed specifications of the blower are summarized in Table 1.
A flow coefficient (F) and a pressure coefficient (Y) are defined as
(1)
(2)
where Q is the volume flow rate, ∆P is the pressure rise, Ut is the impeller tip speed, ρ is the density, and A is the outlet duct area of a blower. The inlet and outlet duct diameter of the impeller used in the present study is 51 mm. The perspective view of the test blower is shown in Figure 1.
The blower mainly consists of a casing (housing) and an impeller. As shown in the figure, impeller blade has an open channel type, and the number of an impeller blade is 54.
3. Experimental Apparatus
Figure 2 shows the schematic view of the experimental set-up, which is an open-loop facility. The facility consisted of a flow control valve, a fan driving motor, nozzle and auxiliary fan. The experimental apparatus was designed according to AMCA 210 [6].
Figure 3 shows the performance curve of the test fan. Pressure linearly decreases as flow rate increases. At the design flow condition, pressure coefficient is 8.43.