Division 6.6.2.3 General procedure for developing infrequent regeneration adjustment factors (IRAFs)

The manufacturer shall declare the normal parameter conditions under which the regeneration process occurs (soot load, temperature, exhaust gas back-pressure, etc.). The manufacturer shall also provide the frequency of the regeneration event in terms of number of tests during which the regeneration occurs. F1The exact procedure to determine this frequency shall be agreed by the approval authority based upon good engineering judgement.

For a regeneration test, the manufacturer shall provide an exhaust after-treatment system that has been loaded. Regeneration shall not occur during this engine conditioning phase. As an option, the manufacturer may run consecutive tests of the applicable cycle until the exhaust after-treatment system is loaded. Emissions measurement is not required on all tests.

Average emissions between regeneration phases shall be determined from the arithmetic mean of several approximately equidistant tests of the applicable cycle. As a minimum, at least one applicable cycle as close as possible prior to a regeneration test and one applicable cycle immediately after a regeneration test shall be conducted.

During the regeneration test, all the data needed to detect regeneration shall be recorded (CO or NO_x emissions, temperature before and after the exhaust after-treatment system, exhaust gas back-pressure, etc.). During the regeneration process, the applicable emission limits may be exceeded. The test procedure is schematically shown in Figure 6.1.

The average specific emission rate related to the test runs conducted according to points 6.6.2.1 or 6.6.2.2 [g/kWh or #/kWh] shall be weighted by means of equation (6-9) (see Figure 6.1):

Where:

n

is the number of tests in which regeneration does not occur,

n _r

is the number of tests in which regeneration occurs (minimum one test),

$\bar{e}$

is the average specific emission from a test in which the regeneration does not occur [g/kWh or #/kWh]

${\bar{e}}_r$

is the average specific emission from a test in which the regeneration occurs [g/kWh or #/kWh]

At the choice of the manufacturer and based on upon good engineering judgment, the regeneration adjustment factor k _r, expressing the average emission rate, may be calculated either multiplicative or additive for all gaseous pollutants, and, where there is an applicable limit, for PM and PN, by means of equations (6-10) to (6-13):

• Multiplicative

  $k_{\mathrm{ru,m}}=\frac{{\bar{e}}_w}{\bar{e}}$	(upward adjustment factor)	(6-10)
  $k_{\mathrm{rd,m}}=\frac{{\bar{e}}_w}{{\bar{e}}_r}$	(downward adjustment factor)	(6-11)

• Additive

  $k_{\mathrm{ru,a}}=\overline{e_w}-\bar{e}$	(upward adjustment factor)	(6-12)
  $k_{\mathrm{rd,a}}=\overline{e_w}-\overline{e_r}$	(downward adjustment factor)	(6-13)