## 1 Introduction
However, the injection and spray macroscopic characteristics of pure RO and its blends with commercial diesel fuel are among the most important factors playing a critical role in diesel engine performance and emissions. The primary purpose of atomization is to increase the surface area of the biofuel and thereby enhance its intensity of evaporation which is vital for achieving the desired rates of heat and mass transfer from the surrounding gases to the fuel. [PERSON] and [PERSON] [5] also emphasize that the properties of a liquid most relevant to atomization are surface tension, viscosity, and density. These fuel properties may have an impact on the flow rate, the velocity of the liquid jet and the parameters of fuel spray patterns as well. A fully turbulent jet breaks up into a multiplicity of small drops when the consolidating surface tension forces are overcome by aerodynamic or pressure forces. The spray attributes include cone angle, penetration, and radial and circumferential liquid distribution. [PERSON] [PERSON] et al. [6] studied the injection process of three fatty acid esters and diesel fuel on a CR system. They found that the injection rate increased with the injection pressure ranging from 45 to 100 MPa due to the enhanced flow capacity. Methyl laurate, and methyl and ethyl oleates produced lower volumetric injection quantities, but their higher density ensured a greater mass cycle injection quantity than diesel. [PERSON] et al. [7] studied the behavior of diesel fuel and RO in a tractor diesel engine with an in-line fuel injection pump for various fuel heating temperatures, engine loads and speeds. They observed that the injection pressure rises earlier before TDC with decreasing fuel temperature due to faster propagation of pressure waves that partially compensate for long ignition delay at lower loads and advances the start of combustion at higher loads. Peak injection pressures were higher for heated (70-80 \({}^{\circ}\)C) RO than for diesel fuel at the same (10%) load and nearly comparable at full (100%) engine load. The earlier start of injection (SOI) and higher injection pressures have the potential to offset the poorer atomization and evaporation of RO at lower loads. [PERSON] et al. [8] evaluated rapeseed oil (R100) as a renewable fuel for agricultural machinery based on long-term operation behavior and emissions of a fleet of tractors over more than 50,000 operation hours under Bavarian farm conditions. The tractors demonstratedtheir full functionality, and no serious engine failures were observed, while minor malfunctions and repairs occurred just occasionally. The reliability of the tractors running on rapeseed oil was comparable to that of tractors running on diesel fuel, with no indication of engine deterioration. The 18 tractors running on R100 saved about 220 tonnes of CO2 eq per year on average from 2015 to 2017. RO is biodegradable, non-toxic, safe to store and handle, and especially suitable for agricultural applications. Low kinematic viscosity, high cetane number diethyl carbonate (DEC) as low price and renewable nature oxygenated additive (solvent) can be used to adjust the viscosity of diesel fuel and castor oil (CO) or sunflower oil (SVO) blends, improve the ignition quality, operating properties of a diesel engine on double DEC/SVO and triple D/DEC/SVO fuel blends, achieve low emissions and reduce smoke density by nearly 92-95% [9]. This method can improve the poor atomization of crude vegetable oil and reduce the formation of deposits in the cylinder. However, blending fuels of various origins and the increased aging process during storage of these blends can provide some difficulties in practical aspects. [PERSON] and [PERSON] [10] investigated the atomization of liquids within the viscosity range of 55.9-134.9 mm\({}^{2}\)/s (involving that of crude rapeseed oil) through swirl hydraulic atomizers to evaluate the changes in the mass flow rate, the discharge coefficient, and the atomization quality.