High -pressure lines of the diesel engine are used to connect the TNVD, the fuel battery (in the case of the Common Rail system) and nozzles). If pumps are installed on the engine, then there is no need for high-pressure highways, t.To. TNVD and nozzle are one knot.
The main requirement when connecting a highway to engine units is a high tightness. To achieve such tightness, when connecting highways, they use high -pressure fittings, sealing cones with a rug nut and traverse.
High pressure fittings are installed primarily on power units of heavy trucks with the Common Rail system or individual fuel pumps.Thanks to the use of the fitting, there is no need to lay the fuel highway around the GBC, which significantly reduces its length. Due to the presence of a rod filter in the fittings, impurities insoluble in fuel are delayed in it and do not fall into the nozzle.
Sealing cones with a united nut are used in all injection systems, t.To. have the following advantages:
simplicity and reliability of the structure;
the possibility of frequent assembly and disassembly with the preservation of tightness;
There are no restrictions on the shape of the sealing cone.
High requirements are imposed on the quality of manufacture of the latter. It does not allow narrowing or changing the shape of the holes by which the fuel is supplied under the pressure. Currently, most cones are produced according to the DIN 73365 standard (Injection Pumps for Diesel Engines; Pressure Pipe Connection).
With a lack of space in the engine compartment, a traverse is used on a limited number of models of car diesel engines. Structurally, it consists of a case in which the fittings are mounted for the supply and discharge of fuel. The traverse is pressed by a special bolt to the upper part of the nozzle case, providing the required tightness.
High pressure lines are made of seamless steel tubes of calibrated diameter and wall thicknesses. The thickness of the walls of the tube varies from 1.3 mm (with an outer diameter of 4 mm), up to 7 mm (with an outer diameter of 22 mm). The minimum radius of the bend of the highway is 50 mm. Redig of the moment of injecting (t.To. A wave of pressure created by the pumping unit spreads at a constant speed – the sound speed, which is about 1,500 m/s diesel fuel), losses for throttle and degree of fuel compression depend on its internal diameter. Thus, for each engine model, the optimal length and internal diameter of the line are selected, which should not in the process of maintenance and repair. Also, the failed highways are not repaired, but only replaced with new.
During the engine operation, the pressure waves that occur as a result of injection of pressure and injection spread through the highways in different directions (back and forth), reflected from the connection at the ends. This effect, which is also called the “survey wave effect” increases with an increase in the frequency of rotation of the crankshaft and is used to increase the injection pressure. That is why the length of the highways should be optimally selected for injection parameters.
The highways supplying fuel from the fuel pump (or battery) to each nozzle have the same length. This is achieved by the optimal arrangement of the fuel pump (or battery) relative to the head of the block with additional bends of the highways.
Since during operation, the highways are subject to high fuel pressure, and their gap during the engine can lead to a fire, very stringent requirements are imposed on their mechanical strength. In particular, the mains of the Common Rail systems operating at pressure from more than 1,400 bar, in the final stage of production at a fraction of a second, subjected to pressure of 3800 bar. This helps to identify hidden defects, as well as compact the internal walls of the highway, making it more durable.