Merge pull request #5 from cuspaceflight/dev-DYER

Dev dyer

Author: astro-zilla

.gitignore

@@ -1,2 +1,3 @@
 /venv/
-/.idea/
+/.idea/
+*.pyc

README.md

@@ -1,2 +1,27 @@
-# white-giant-injector
-A repository for m5 injector design engineers to collate code performing analysis on injector flow and efficacy.
+# ***OCTOPUS***
+
+<img src="img/logo.png" alt="logo" width="600"/>
+
+## A repository for m5 injector design engineers to collate code performing analysis on injector flow and efficacy.
+
+### Eventual planned features:
+*   Choice of SPI, HEM and Dyer (with Solomon correction) models
+*   Compressibility corrections
+*   Orifice types - Waxman cavitating, basic
+*   Estimation of orifice discharge coefficients (from empirical data) (?)
+*   Estimation of atomisation performance (from empirical data) (?)
+*   Determine pressure drop, orifice mass flow, element O/F, overall O/F, etc with the above
+*   Determine film cooling mass flow proportion (~20% is said to be sufficient to ignore the core O/F for temperature calculations, need to find the source for this - possibly NASA SP-8089)
+*   Warnings for combustion stability criteria (from empirical data)
+*   Document everything - kill two birds with one stone here and write up all the injector notes in preparation for the new wiki?
+
+### Currently in progress:
+*   Finding specific enthalpy and any other important chemical properties, transport properties
+  * Possibly with multiple source data options / averaging / sense checks
+*   Decisions on classes / where everything should live
+  * Current intended structure: Injector plate --> Manifolds --> Injector elements --> Orifices
+
+### Things that need fixing:
+*   Sure this won't stay empty long...
+
+SI base units used everywhere, except for possibly some final output and graphing.

dev.py

@@ -0,0 +1,30 @@
+from matplotlib import pyplot as plt
+from numpy import linspace
+
+from octopus import Fluid, Orifice, STRAIGHT
+
+
+def main():
+    fluid = Fluid('N2O', T=250, P=18e5)
+    orifice = Orifice(fluid, 0, 15e5, STRAIGHT, 1e-2, 1e-3)
+
+    P_cc = linspace(0, 19e5, 100)
+    SPI = []
+    HEM = []
+    DYER = []
+    for Pcc in P_cc:
+        orifice.P_cc = Pcc
+        SPI.append(orifice.m_dot_SPI())
+        HEM.append(orifice.m_dot_HEM())
+        DYER.append(orifice.m_dot_dyer())
+
+    plt.plot(P_cc, SPI, label='SPI')
+    plt.plot(P_cc, HEM, label='HEM')
+    plt.plot(P_cc, DYER, label='DYER')
+    plt.xlabel('Downstream pressure (Pa)')
+    plt.ylabel('Mass Flow Rate (kg/s)')
+    plt.show()
+
+
+if __name__ == "__main__":
+    main()

img/logo.png

@@ -2,26 +2,57 @@
 import numpy as np
 
 
-def fuel_mass_flow():
-    N = 1000
+def mdot_spi(Cd, A, n, rho, p_chamber):
+    # Calculates and plots a single phase incompressible (SPI) approximation of the mass flow.
 
-    Cd = 0.77                                               # sensible discharge coefficient
-    A = np.pi * 0.5e-3 ** 2                          # area of a 0.5mm radius orifice
-    n = 95                                            # number of orifices
-    rho = 1000                                              # kg/m3
-    p_chamber = 1500000                                     # 1.5MPa, 15bar
+    N = 1000
     dp = np.linspace(0.15 * p_chamber, 0.2 * p_chamber, N)  # 25-20% of chamber pressure
 
-    mdot = n * Cd * A * np.sqrt(2 * rho * dp)                   # aiming for 1.3 kg/s for fuel
+    mdot = n * Cd * A * np.sqrt(2 * rho * dp)  # aiming for 1.3 kg/s for fuel
 
     ax = plt.subplot(1, 1, 1)
     ax.plot(dp, mdot)
     ax.set_xlabel("Pressure Drop [Pa]")
     ax.set_ylabel("Mass Flow Rate [kgs$^{-1}$]")
-    ax.set_title("Fuel Flow Rate (Standard Model)")
+    ax.set_title("Fuel Flow Rate (SPI)")
 
     plt.show()
 
 
+def mdot_hem(A):
+    # produces mass flow given a total area, assuming choked flow in HEM
+
+    h_fgo = 1000 * ((-69.8) - (-355))  # J/kg
+    v_fgo = (1 / 40.11) - (1 / 1014.8)  # m3/kg
+    C_fo = 1915  # J/Kg.K
+    T_o = 273 - 25  # K
+    return (h_fgo / v_fgo) * np.power(C_fo * T_o, -0.5) * A
+
+
+def req_A(mdot):
+    # produces the required total area for a given mass flow using HEM
+
+    h_fgo = 1000 * ((-69.3) - (-345))  # J/kg
+    v_fgo = (1 / 46.82) - (1 / 995.4)  # m3/kg
+    C_fo = 1957  # J/Kg.K
+    T_o = 273 - 20  # K
+    return (v_fgo / h_fgo) * np.power(C_fo * T_o, 0.5) * mdot
+
+
+def delta_p(mdot, A, n, Cd, rho):
+    return np.power(mdot / (A * n * Cd), 2) / (2 * rho)
+
+
 if __name__ == "__main__":
-    fuel_mass_flow()
+    Cd = 0.7  # sensible discharge coefficient
+    A = np.pi * 0.5e-3 ** 2  # area of a 0.5mm radius orifice
+    rho = 995.4  # kg/m3
+    mdot = 4.1
+    p_chamber = 1500000  # 1.5MPa, 15bar
+
+    # mdot_spi(Cd, A, n, rho, p_chamber)
+    calc_A = req_A(mdot)
+    n = int(calc_A / A)
+    dp = delta_p(mdot, A, n, Cd, rho)
+    print(f'required area for {mdot}kg/s: {round(calc_A, 7)}m^2. Assuming 1mm diameter, {n} orifices required')
+    print(f'required pressure drop for {mdot}kg/s over {n} {round(A, 7)}m^2 orifices: {round(dp, 4)}Pa')