## 1 Introduction
They showed that the discharge coefficient of nozzle orifics and the mass flow rate depend on the Reynolds number. Additionally, spray droplets become smaller with increasing injection pressure and oil temperature, which effectively decreases oil viscosity as the major contributing factor to the improved break up of the spray. [PERSON] et al. [11] conducted single-shot injection experiments with a pump-line-nozzle injection system in an optically accessible constant volume combustion chamber filled with inert gas, N\({}_{2}\), at a maximum pressure of 80 bar and temperature of 150 \({}^{\circ}\)C. They studied the influences of physical fuel properties, engine speed and in-cylinder conditions on the injection pressure, needle lift, spray length, cone angle and atomization using diesel fuel, rapeseed biodiesel, rapeseed oil, palm oil and animal fats. The higher bulk modulus of straight vegetable oil and animal fat resulted in an earlier and faster needle lift, while higher density led to longer injection duration, slightly faster spray penetration and worse atomization compared to diesel and RME with similar spray angles for different fuels. [PERSON] et al. [12] found that the higher viscosity and surface tension of castor oil, neem oil and sunflower oil increases the Sauter mean diameter values 2.4, 1.4 and 1.1 times and on the contrary, decreases the cone angle of the spray in comparison to petroleum diesel fuel at the injection pressure of 200 bar and air density of 25 kg/m\({}^{3}\). Vice versa, the lower viscosity of oxygenated fuels plays a positive effect on the atomization quality; therefore, these fuels show larger spray cone angles and shorter spray tip penetration (STP). While biodiesel shows longer STP, larger peak velocity of the spray tip and smaller SCA compared to diesel [13]. This may happen because biodiesel's relatively higher density and viscosity are not conducive to improving the liquid spray and promoting the mixture. [PERSON] et al. [14] investigated the spray characteristics of different blends of biodiesel derived from drainage oil and diesel BD20, BD50, BD80, and BD100 under different injection (60-100 MPa) and ambient (0.1-0.9 MPa) pressures using CR system equipped with a constant volume chamber. They found that as increased injection pressure was increased, spray tip penetration, spray angle, spray area and spray volume increased. Increased ambient pressure led to the spray angle increasing, but the spray tip penetration and the peak of average tip velocity decreased. Viscosity and surface tension were the main physical properties affecting liquid jet breakup and atomization. Tests of Residual Fuel Oil (RFO) showed that the spray area and its volume are not affected by changes in the fuel viscosity and surface tension, these parameters increase with the injection time mainly [15]. The higher viscosity of RFO than that of diesel increased penetration length, while the spray cone angle decreased at higher viscosity values for both fuels. Further investigations by [PERSON] et al. [16] showed that low fuel temperature causes longer injection delays, shorter injection duration, lower mass flow rate and less fuel mass injected. The low fuel temperature can effectively suppress the occurrence of cavitation, which accelerates the transition from cavitating to turbulent flow and then to laminar flow with a decrease in injection pressure. The discharge coefficient was affected more by the fuel viscosity at low temperature (\(-18~{}^{\circ}\)C) than by the injector's structure, but the low temperature and injection pressure changed the laminar flow and, thus, the discharge coefficient decreased. [PERSON] et al. [17] conducted an experimental and computational investigation in a CR DI system to evaluate the influence of the physical properties of biodiesel (RME) on the injection process (mass flow rate) and the behavior of the system under multi-injection strategies.