Patent ID: 8065119

Claim:
A computerized method for designing an aerodynamic focusing lens stack, said computerized method comprising: receiving as input in a computer the design parameters of: (1) the particle size range to be considered (d particle (min) , d particle (max) ) and the particle density thereof (ρ particle ); (2) pa characteristics of the gas to be flowed through the aerodynamic focusing lens n stack design, including dynamic viscosity (μ), standard gas mean free path (λ standard ), heat ratio (γ), gas constant (R), molecular mass (M), and flow type, either isothermal flow or isentropic flow; (3) the temperature (T[ 1 ]) and pressure (P[ 1 ]) upstream of a first focusing lens [i=1] of the aerodynamic focusing lens stack design; (4) the flow rate through the aerodynamic focusing lens stack equivalent at atmosphere pressure (Q equ ); and (5) a Stokes number range defining the focusing tightness (Stk min , Stk max ); based on said received design parameters, determining the number of focusing lenses and their respective orifice diameters (d lens [i]) required to focus the particle size range to be considered, and including the steps of: (a) solving for the orifice diameter (d lens [i]) of the i th focusing lens, in the Stokes number equation: FOCUS(T[i], Q[i], P[i], λ standard , μ, d lens [i], d particle [i], ρ particle , Stk max )=0, beginning with the first focusing lens [i=1] where d particle [1]=d particle (max) and Q ⁡ [ 1 ] = Q equ ⁡ ( P atm P ⁡ [ 1 ] ) ; (b) using the value of the orifice diameter (d lens [i]) in step (a) to solve for a new maximum particle size d particle [i+1] to be focused in the next [i+1] th focusing lens, in the Stokes number equation: FOCUS(T[i], Q[i], P[i], λ standard , μ, d lens [i], d particle [i+1], ρ particle , Stk min )=0; (c) determining the pressure drop across the [i] th focusing lens by solving for a pressure P[i+1] downstream of the [i] th focusing lens and upstream of the next [i+1] th focusing lens, in the Prandtl derivation: DROP (T[i], Q[i], P[i], P[i+1], d lens [i], γ, R, M)=0; (d) setting the temperature T[i+1] and flow rate Q[i+1] of the next [i+1] th focusing lens according to: if the flow type is isothermal flow, then T ⁡ [ i + 1 ] = T ⁡ [ i ] ⁢ ⁢ and ⁢ ⁢ Q ⁡ [ i + 1 ] = Q ⁡ [ i ] ⁢ ( P ⁡ [ i ] P ⁡ [ i + 1 ] ) = Q equ ⁡ ( P atm P ⁡ [ i + 1 ] ) ; and if the flow type is isentropic flow, then T ⁡ [ i + 1 ] = T ⁡ [ i ] ⁢ ( P ⁡ [ i + 1 ] P ⁡ [ i ] ) γ - 1 γ and Q ⁡ [ i + 1 ] = Q ⁡ [ i ] ⁢ ( P ⁡ [ i ] P ⁡ [ i + 1 ] ) = Q equ ⁡ ( P atm P ⁡ [ i + 1 ] ) 1 γ ; and (e) setting i=i+1 and iteratively performing steps (a) through (d) using the values for d particle [i+1], P[i+1], T[i+1], and Q[i+1] determined in the previous iteration, until d particle [i+1] in step (b) is less than d particle (min) ; and outputting to a designer the respective orifice diameters of all the number of focusing lens determined to be required to focus the particle size range to be considered.