Prop changes for motor integration

gpkitmodels/GP/aircraft/prop/propeller.py

@@ -2,18 +2,24 @@
 from numpy import pi
 from gpkit import Model, parse_variables, SignomialsEnabled, SignomialEquality
 
+
 class Propeller(Model):
     """ Propeller Model
 
     Variables
     ---------
-    R          10           [m]         prop radius
-    W          .01          [lbf]        prop weight
-
+    R                               [ft]            prop radius
+    W                               [lbf]           prop weight
+    K           4e-4                [1/ft^2]        prop weight scaling factor
+    T_m_static   40.                [lbf]           prop max static thrust
     """
     def setup(self):
         exec parse_variables(Propeller.__doc__)
 
+        constraints = [W == K*T_m_static*R**2]
+
+        return constraints
+
     def flight_model(self,state):
         return Propeller_Performance(self, state)
 
@@ -22,7 +28,7 @@ class Propeller_Performance(Model):
 
     Variables
     ---------
-    T                       [N]         thrust
+    T                       [lbf]       thrust
     Tc                      [-]         coefficient of thrust
     etaadd     0.7          [-]         swirl and nonuniformity losses
     etav       0.85         [-]         viscous losses
@@ -34,8 +40,11 @@ class Propeller_Performance(Model):
     CT                      [-]         thrust coefficient
     CP                      [-]         power coefficient
     Q                       [N*m]       torque
-    omega                   [RPM]       propeller rotation rate 
-
+    omega                   [rpm]     propeller rotation rate 
+    omega_max    10000           [rpm]     max rotation rate
+    P_shaft                 [kW]        shaft power
+    M_tip       .5          [-]         Tip mach number
+    a           295         [m/s]       Speed of sound at altitude
     """
 
     def helper(self, c):
@@ -46,15 +55,20 @@ def setup(self,parent,  state):
 
         V       = state.V
         rho     = state.rho
-        R       = parent.R        
+        R       = parent.R
+
 
         constraints = [eta <= etav*etai,
                 Tc == T/(0.5*rho*V**2*pi*R**2),
                 z2 >= Tc + 1,
                 etai*(z1 + z2**0.5/etaadd) <= 2,
                 lam == V/(omega*R),
                 CT == Tc*lam**2,
-                #CP == Q*omega/(.5*rho*(omega*R)**3*math.pi*R**2),
-                #eta == CT*lam/CP, #Is this the same eta? check 
+                CP == Q*omega/(.5*rho*(omega*R)**3*pi*R**2),
+                eta == CT*lam/CP, 
+                omega <= omega_max,
+                P_shaft == Q*omega,
+                (M_tip*a)**2 >= (omega*R)**2 + V**2
+
                 ]
-        return constraints
+        return constraints, state