Diesel Injector Fuel Injector 0445110502 Bosch for Uaz Hunter/Patriot 2.0CD 08

Transient states analysis of CI engine injectors with the use of optical methods

Abstract.

The main aim of research was to define real injection time delay against the time of
electrical control signal for piezoelectric and electromagnetic diesel fuel injectors. The second
objective of this work was the evaluation of influence of typical injection parameters on this
delay. The analysis was focused on the occurrence of appropriate control signals recorded with
the use of fast-varying data acquisition system and compared with the data recorded by high
speed camera. The tests were conducted in constant volume chamber for different injector types
used in combustion engines with direct injection of diesel fuel. The tests were performed under
variable conditions: different fuel pressure, air back-pressure and injection duration time.
1. Introduction
High pressure injection of liquid fuel realized by common rail system requires high precision in fuel
quantity delivered into combustion chamber by injector. Currently there are two main types of injectors
commonly used for both compression ignition and spark ignition engine: electromagnetic and
piezoelectric. Although operational fuel pressure in gasoline injection systems is much lower in
comparison to diesel fuel systems, but injector opening times are almost the same for both types of
construction. That fact makes the requirements similar for CI and SI injectors. These devices should be
characterized by possibly fast response to proper control signals for both opening and closing operation.
Payri et al. [1] investigated the influence of the electromagnetic and piezoelectric technologies on
injection process for indirect-acting piezoelectric and solenoid injectors. In that aspect hydraulic
characteristics were prepared for both designs and then compared with each other. In this research the
fuel rate indicator based on Bosch method was applied. The achieved results showed faster actuation of
piezo-injectors compared the solenoid ones. What it means is that their hydraulic delay is smaller. The
differences were increasing inversely proportional to the injection pressure. Second observation from
that test was the higher flow speed of fuel for piezo-injector compared to the other design with similar
hole diameter.
Similar research was conducted by Yu et al. [2], but in that case fuels selected for investigations were
kerosene and diesel fuel. Based only on control signals and variation of fuel flow rate from injector
nozzle, the injection delay against the time of electrical opening signal was obtained. The values of this
parameter were constant independently of injection pressure (in this case 60 and 100 MPa) and the delay
times were respectively 0.45 ms for piezo- and 0.55 ms for solenoid injector. Additionally, faster flow
from injector nozzle for lower injection pressures was observed. That fact gives significant benefits to
combustion engine operation such as better atomization and evaporation of fuel. The said authors used