ECM egrCAN, Инструкция по эксплуатации, Страница: 5 / 52

1
Introduction
egrCAN is a modular, multichannel, exhaust gas recirculation (EGR) ratio measurement
system. egrCAN is scalar. The basic system (see Figure 1) consists of three modules: one
measuring ambient air (the “air module”), one measuring the intake charge (the “intake
module”), and one measuring the exhaust of the engine (the “exhaust module”). More
intake and exhaust modules can be added to measure EGR in different locations in the intake
manifold (to study EGR distribution) or to measure %EGR in multi-stage EGR systems.
Additionally, all egrCAN systems report engine %O2
1
, Lambda (AFR, FAR, Equivalence
Ratio) and absolute pressure at each measurement location.
egrCAN is a CAN-based system. Thus, all communication with the system is via CAN. A
supplied PC Configuration Tool is used to configure the modules, observe module outputs,
record module outputs, and produce a .dbc file. dashCAN displays can be added to egrCAN
systems to display system parameters.
Figure 1 shows a basic egrCAN system. Each module outputs information that is used to
calculate %EGRv (volume based %EGR) via the formula:
%EGR = 100 · (O2air - O2int) / (O2air – O2exh) [Equation 1]
where:
O2air = Parameter O2 (%O2) output by the “air” module.
O2int = Parameter O2 (%O2) output by an “intake” module. An egrCAN system can have
multiple intake modules. Thus multiple %EGRs can be reported for different
locations (for EGR distribution studies) or stages (for multi-stage EGR
systems).
O2exh = Parameter O2 (%O2) output by an “exhaust” module.
The %EGR calculated via Equation 1 is numerically equivalent to the commonly used
definition of volume-based definition of:
%EGRv = 100 · ve / (va + ve) [Equation 2]
where:
%EGRv = volumetric (molar) exhaust gas recirculation, percent
ve = volume of exhaust gas inducted into the engine
va = volume of air from the atmosphere inducted into the engine
Note that the calculation (Equation 1) of the various %EGRv must be performed by the
host’s data acquisition system. egrCAN provides the required O2s (ie. O2air, O2int, O2exh)
for the calculations.
egrCAN will make available EGR information at a much higher bandwidth than with
classical sampling systems. Averaging of the calculated %EGR information can be
performed in the host data acquisition system.
1
To match the appearance of parameter names, O
2
will be written as O2 (no lower case 2).