Fuel Influence on Single-Piston Common Rail Pump Performance

Alternative and renewable fuels play a fundamental role in research and development activities aimed at reducing the environmental impact of internal combustion engines. The possibility of using alternative fuels, whether they are pure or blended, is linked to the flexibility of the injection system, whose behavior depends on the fuel features. In this context, the article reports an investigation on a high-pressure pump for common rail diesel injection systems. Investigations have considered a single-piston pump, widely adopted in the field of light duty diesel engines. The experimental activity has been conducted on an instrumented test rig, equipped with a fluid thermoregulation system. Moving from a conventional fluid (commercial diesel) to a waste cooking oil (WCO) biodiesel, the influence of such alternative fuel on pump behavior has been investigated and discussed, highlighting the link between pump performance (in terms of torque- and volumetric-efficiency) and fuel type. The investigations allow to characterize the performance of the current generation of a single-piston pump, operating with pure fuels (diesel and biodiesel) and their blends (B20 and B40). The impact of operating conditions and fuel type is analyzed on a wide pump operating range, both in terms of shaft speed and delivery pressure; the results show how the pump behavior reflects the mechanical features of the fuels (viscosity and compressibility modulus), and that a significant increase in pump efficiency is obtained when using a limited biodiesel content in mixture (B20).