3.1    Thermodynamical process in the suction circuit
          Fig.  3 depicts physical constitution of suction system:
sealing, mainbody, and impeller. Under the drive of the centrifugal  fan  impeller  at  high  rotary  speed,  external atmospheric air (state A) flows into the chamber through the sealing component (state B), airflow’s static pressure drops  from  P0  to  P1  as  a  result  of viscous  friction dissipation and dynamic-static pressure conversion through the sealing device. Let the effective coverage area be S0, and adsorption force Fa can be approximately calculated as：
 Fig. 3.    Diagram of air state changes in suction circuit
           Improving  impeller’s  efficiency  means  avoiding  or restraining the energy losses such as local losses, traveling losses, boundary layer separation and frictional secondary flow, on the premise that the impeller’s capacity of doingwork  is  not  affected,  which  requires  a  specific  designmethodology suitable for SWCR robot.
     
3.2    Hydromechanical analysis
   Hydromechanical  analysis  is  committed  to  providing technical solutions, which deduces the relationship between Fa and impeller’s work through a detailed analysis of air flow’s state changes in suction cycle.
    High-speed  airflow  is  concentrated  close  to  the  wallsurface in the chamber, and converges in the center, then bends 90?upward to the inlet of the impeller. The rest part of the chamber is backflow zone with a little effect on adsorption  characteristics.
          That is  important  for  impeller  design,  relatingimpeller’s  aerodynamic  performance  to  Fa.  Its  physical meaning is that effective negative pressure consists of two parts, one is static pressure rise of impeller, and the other is the  part  of  dynamic  pressure  at  the  export  which  is effectively used.

4    Design of Impeller Specific for SWCR

   Design method for SWCR-specific centrifugal impeller is on the basis of that for common centrifugal fans, while the unique characteristics of this method are as follows:
           (1) 7-parameter  method  is  presented,  in  which  theparameters  are  inlet  width  B1,  outlet  width  B2,  inlet diameter D1, outlet diameter D2, inlet installation angle β1A, outlet installation angle β2A, blade number Z, and determine the geometry of impeller, see Fig. 4.
                          
                    Fig. 4. 7-parameter geometric modeling of impeller
(2)  Instead  of  goals  of  preconcerted  flow  rate  and pressure ratio, the method aims at meeting the need of chamber vacuum that produces an appropriate adsorption force for SWCR to adhere and maneuver. Based on Eq. the method properly allocates impeller static pressure and  uses  outlet  kinetic  energy,  and  ultimately  attains  a high-efficiency  impeller  that  creates  adequate  negative pressure in the sucker.
(3) Static pressure rise plays a major role in formation of Fa, so that the impeller with a higher static pressure ratio could obtain the same vacuum at the cost of lower power. In addition, high-static-pressure-ratio impeller has poor ability of doing work, which means that impeller needs a higher speed for the same power capability, but, high rotating speed may lead to excessive relative velocity inside the impeller,  which  lowers  the  efficiency.  Therefore  static pressure ratio should be selected by contrast. Moreover, when static pressure ratio is constant, with β2A increasing, the adaptability to flow rate change is enhanced, which means  vacuum  level  can  be  approximately  maintained when there is a sudden increase in flow rate, however, corresponding  B2  gets  smaller,  and  the  internal  flow velocity  higher,  which  also  brings  energy  loss,  so  β2A  should also be selected after comparison. 滑动爬壁机器人英文文献和中文翻译(4):http://www.youerw.com/fanyi/lunwen_16703.html