ODREC is a program for the preliminary design and 1-D regenerative cooling analysis of liquid propellant rocket engines, which is developed using the object-oriented programming in MATLAB.
Please refer to the study (https://doi.org/10.3390/app14010071) for the details on the method/formulation and capabilities of ODREC. Also, if you plan to use ODREC in your study, please cite the study.
There are two prerequisities to use ODREC:
- DimVar tool (https://github.com/tgvoskuilen/MatlabTools)
- MATLAB version of NASA CEA (https://github.com/PurdueH2Lab/MatlabCEA)
To use ODREC, an instance of the class should be created:
Analysis = ODREC(inputs,l_prop,s_prop,v_prop);
where inputs is a struct with the following fields:
- fuel: the name of the fuel
- oxidizer: the name of the oxidizer
- T_o_c: temperature of the oxidizer entering into the combustion chamber in K
- T_f_c: temperature of the fuel entering into the combustion chamber in K
- discretization: an array of 5 elements, each of which denotes the number of sections each thrust chamber part is divided into. The parts are cylindrical combustion chamber part, circularly converging combustion chamber part, small converging nozzle part, fist diverging nozzle part, bell shaped nozzle part. If the user externally gives the thrust chamber profile as an input rather than generating within the ODREC, then discretization should be a scalar denoting the total number of discretization of the thrust chamber, rather than an array.
- eps: roughness of the inner thrust chamber wall in m
- i_c: index of the coolant, 1: fuel, 2: oxidizer
- y: thrust chamber wall thickness at channel base in m
- L_star: characteristic length of the combustion chamber in m
- theta_n: deflection angle of bell nozzle in deg
- theta_e: exit angle of the bell nozzle in deg
- P_c_i: inlet pressure of the coolant in Pa
- T_c_i: inlet temperature of the coolant in K
- k_wall: wall thermal conductivity in W/mK
- P_1: pressure in first table of vapor properties in Pa
- P_l: pressure in last table of vapor properties in Pa
- N_p: number of tables of vapor properties
- P_c: combustion chamber pressure in Pa
- F: thrust in N
- OF: oxidizer to fuel mass flow rate ratio
- Pe: ambient pressure in Pa
- N: number of cooling channels
- w: width of the cooling channels
- h: height of the cooling channels
Some remarks about inputs:
- Only those fuel and oxidizer names that are accepted in NASA CEA website (https://cearun.grc.nasa.gov/) can be used.
- Only those T_o_c and T_f_c values that are accepted in NASA CEA website can be used. For most propellants, these values are the saturation temperatures at the sea level. Note that T_o_c and T_f_c values do not change the analysis much.
- y,w, and h can be given as constants or variables throughout the thrust chamber. If they are variables, they can just be given as an array thoughout the axial position.
- If desired, an additional input field of w_b, which is the rib or channel wall width, can be provided as a constant or a variable. If not given, ODREC will calculate it using the other inputs.
- ODREC generates a thrust chamber profile if it is not given externally. If desired, the user should provide it as follows:
Analysis = ODREC(inputs,l_prop,s_prop,v_prop,geom);
where geom is a matrix storing the axial position versus radial position of the thrust chamber profile:
geom(:,1)=X;
geom(:,2)=Y;
where X is the axial, Y is the radial position.
Some remarks about the coolant properties:
- l_prop: a matrix storing the thermophysical properties of the coolant in liquid form, which includes 5 columns of arbitrary length. The first column is the temperature, and the others are the corresponding density, specific heat, dynamic viscosity and thermal conductivity, respectively. For a healthy estimation, temperature range should approximately cover the working temperature range. The properties could be obtained from NIST (https://webbook.nist.gov/chemistry/fluid/) at a pressure value similar to the working pressure. Note that all properties should be in SI units.
- s_prop: a matrix storing the thermophysical properties of the coolant in liquid form, which includes 12 columns of arbitrary length. The columns are temperature, pressure, saturated liquid density, saturated liquid specific enthalpy, saturated liquid specific heat, saturated liquid dynamic viscosity, saturated liquid thermal conductivity, saturated vapor density, saturated vapor specific enthalpy, saturated vapor specific heat, saturated vapor dynamic viscosity, and saturated vapor thermal conductivity, respectively. Pressure and temperature range should approximately cover the saturation curve.
- v_prop: a 3-dimensional array storing the thermophysical properties of the coolant in liquid form, which includes 5 matrices, each of which has 5 columns of arbitrary length. It should be prepared, for example, as follows:
v_prop(:,:,1)=properties_10bar;
v_prop(:,:,2)=properties_20bar;
and etc where right hand side is an isobaric property tables evaluated at a certain pressure. The number of property table to be used is decided by the user, as well as the pressure values at which the tables are evaluated. However, pressure values should be equidistant.
After the instance of the class is initiated, analysis could be carried out as follows:
Analysis = Analysis.Thermal_Analysis(inputs);
The aim of the fact that the definition of properties and analysis are carried out separately is to accelerate the process especially for optimization studies.
where now the object will have the following properties:
- I_sp: specific impulse in s
- C_F: thrust coefficient
- C_star: characteristic velocity in s
- Tem_c: coolant temperature in K
- p_c: coolant pressure in Pa
- q: wall heat flux in W/m^2
- T_w: wall temperature in K
- Ma: Mach number
- X: axial coordinate of the thrust chamber
- Z: radial coordinate of the thrust chamber
- X_g: vapor fraction
- mdot_c: coolant mass flowrate
Note that an example main code and property data for some example coolants are attached.