## 4 Experimental Setup  
The experimental setup was established to perform the required research and development. A schematic in Figure 13 shows the process and instrumentation diagram of the experimental setup. Table 9 presents details of specification of the experimental apparatus. Figure 11: Static temperature vs. nozzle radius of C3 and C4. Figure 12: Mach number vs. nozzle radius of C3 and C4. GG, along with the injection head and combustion chamber, is shown in Figure 14a. Figure 14b shows an integrated GG with propellant tanks on the test bed along with the required data acquisition systems. A spark plug-based ignition system was used to ignite the propellants for primary combustion. Convergent and divergent parts of the nozzle were water-cooled. Five pressure and three temperature ports were strategically placed to evaluate the experimental performance. Piezoelectric pressure sensors and K-Type thermocouples were used to measure these parameters. Figure 14: (a) Gas generator major components. (b) Gas generator with configured instrumentation. Figure 13: Process and instrumentation layout of the experimental setup. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Apparatus** & **Details** & **Quantity** \\ \hline
1 & Pressure tanks & N2, 152 bar, 90 Liters & 2 \\
2 & Data acquisition & Arduino 2560, ATmega2560, 6–20 V & 2 \\
3 & Ignition mechanism & Spark Plug-Electrical Coil, 12-volts & 1 \\
4 & Flow meter gauges & Pressure 200 bar, Temperature 366.15 K & 5 \\
5 & Emergency stop & Kill ByST-NC, 250 V, Max 338 K & 1 \\
6 & Pressure sensors & HPT300-5, 0 to 600 bar, 308–398.15 K & 5 \\
7 & Temperature sensors & K-Type, 73.15–1623.15 K & 5 \\
8 & Chamber/nozzle & AISI 1018 Carbon St, Melt Temp 1093 K & 1 \\
9 & Primary injectors & Co Axial Plate, Maxdot 0.113 Kg/s & 1 \\
10 & Secondary injectors & Normal, Max Dia 1 mm Each & 4 \\
11 & Fuel tank & Keresne, 150 bar, 20 Liters & 1 \\
12 & First oxidizer tank & LOX, 150 bar, 82.5 Liters & 1 \\
13 & Second oxidizer tank & GOX, 150 bar, 82.5 Liters & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Specifications of experimental apparatus. To obtain data from the sensors, a reliable data acquisition method for collecting and processing information was mandatory. An Arduino was selected for data acquisition from the sensors. Figure 15, depicts two Arduino Mega 2560 hardware components that were integrated and programmed on the Vero Board. Thermocouples, which are electrical devices, were used to obtain the temperature profiles at the aft section of the engine. The most common type of thermocouple is the \"K-Type\" (chromel-alumel) thermocouple, which was used for this experiment. The K-Type is the most commonly used general-purpose thermocouple, with a sensitivity of approximately 41 \(\upmu\)V/\({}^{\circ}\)C. The K-Type thermocouples were readily available in the propulsion lab, and they fulfilled the required range of temperature variation from \(-200\)\({}^{\circ}\)C to +130 \({}^{\circ}\)C (73.15 K to +1623.15 K) needed for the experiment. To measure the pressure profile, piezoelectric pressure sensors \"HPT300-S Universal Pressure Sensors by Holykell Technology\" were used in the experiment. The reason for choosing HPT300-S for measuring pressure is its rugged design. It also provides vibration resistance, and shock resistance, has a wide range of temperature variations, and is suitable for other extreme environmental conditions. At standard conditions (ambient temperature: 25 \({}^{\circ}\)C), the working pressure and temperature of HPT300-S sensors are 0 bar-600 bar and 35 \({}^{\circ}\)C to +125 \({}^{\circ}\)C (308.15 K to +398.15 K), respectively, while the measuring error and accuracy are approximately 1.0 to 3% F.S. The HPT300-S sensors were lightweight, small in size, easy to install and operate, and fulfilled experimental requirements, so they were considered for the experiment. Figure 16, below, shows both thermocouples and pressure sensors. Figure 16: Thermocouples and pressure sensors.