## 2 Materials and Methods
### Experimental Setup  
The objective of the experimental research is to evaluate the performance, combustion, and emissions characteristics of a direct injection compression ignition (DICI) engine using a combination of hydrogen and diesel fuel as the power source. The experimental setup included the connection of a diesel engine, with a solitary cylinder, a four-stroke operation, and water cooling equipment to a hydrogen cylinder, as seen in Figure 2. Table 2 presents the configuration features of the diesel engine. The use of an eddy current dynamometer involves its connection to the engine control unit (ECU) for the purpose of regulating a range of engine parameters. Additionally, it is linked to the engine in order to exert a load. The AVL DIGAS-444 (flue gas analyser), AVL India Pvt. Ltd., Gurugram, India, was used to conduct an exhaust emission analysis. Table 3 displays the attributes of the flue gas analyser. The measurement of combustion pressure was conducted using a Piezotronics sensor, while the crank angle was monitored using a Kubler sensor. Additionally, the fuel flow rate was determined using a Yokogawa sensor. Temperature data were collected by means of K-type thermocouples that were strategically placed throughout the engine configuration. The engine speed, as seen on a digital display, was presented in units of revolutions per minute (rpm). The use of a high-pressure pump was implemented in order to provide diesel fuel to the common rail injection system at an elevated pressure. The primary responsibility of the high-pressure pump was to provide diesel to the common rail injection system, irrespective of the system's load conditions. The pump was responsible for extracting diesel fuel from the fuel tank and then filtering it. The solenoid valve regulated the amount of diesel supplied to the loading situation. Two manual procedures, namely the burette and stopwatch, were used to measure the flow rate of the diesel. The burette was directly linked to the fuel tank for this purpose. Following a duration of 10 min at an engine speed of 1500 revolutions per minute, the engine was allowed to attain a state of steady-state combustion. Subsequently, the collection of performance and emission data was conducted at full load (10 kg for the engine). The engine parameters were calculated from data provided by 'enginesoft' software 9.0. Hydrogen energy-share ratios were experimentally examined in conjunction with diesel fuel over a range of engine loads. During the suction stroke, a consistent flow of hydrogen was supplied to the intake manifold, gradually displacing the anticipated volume of air. The intake manifold of the car generated a homogenous blend of hydrogen and air. The pressure regulator was used to decrease the high-pressure hydrogen inside the cylinder to a level of 2 bars. Prior to introducing hydrogen into the system, a flame arrester was put at the intake manifold in order to prevent the occurrence of explosions and backfires. In order to mitigate the accumulation of excessive pressure, the flame arrestor was equipped with a pressure release valve. There exist two distinct categories of non-return valves: the first is positioned before to the entry of the input manifold, while the second is set before the entrance of the flow meter. A hydrogen flow meter is used for the purpose of controlling the magnitude of hydrogen flow. \begin{table}
\begin{tabular}{l c c c} \hline
**Fuel** & **Hydrogen** & **Waste Plastics Oil** & **Diesel** \\ \hline Density (kg/m\({}^{3}\)) & 0.08 & 884.0 & 830 \\ Lower calorific value (MJ/kg) & 120 & 43.0 & 42.5 \\ Kinematic viscosity (mm\({}^{2}\)/s) @40 \({}^{\circ}\)C & 0.0083 & 3.64 & 3.0 \\ Sulphur Content & 00 & 0.03–0.35\% [14] & 10 ppm (–0.001\%) \\ Cetane number & 5–10 & 50 & 48–52 \\ \hline \end{tabular}
\end{table} 
Table 1: Fuel properties of test fuel [12].