ASTM D7170 Standard Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel Oils - Fixed Range Injection Period, Constant Volume Combustion Chamber Method
9. Sampling and Test Specimen Preparation
9.1 Sampling:
9.1.1 Collect diesel fuel oil samples in accordance with Practices D4057 or D4177.
9.1.1.1 Warning - Collect and store diesel fuel oil samples in a suitable container such as a dark brown bottle, a metal can, or a minimally reactive plastic container to minimize exposure to UV emissions.

9.1.2 Refer to Practice D5854 for appropriate information relating to the mixing and handling of diesel fuel oil samples.

9.2 Test Specimen Preparation:
9.2.1 Sample Fuel Temperature - Condition the diesel fuel oil sample before opening the storage container, so that it is at room temperature, typically 18 °C to 32 °C.

9.2.2 Filtration - Samples may be filtered through a Type I, Class A filter paper at room temperature and pressure before testing (see Specification E832), or through a nominal 3 µm to 5 µm porosity filter element using a syringe.
9.2.2.1 Collect the specimen in a dark brown bottle, metal can or minimally reactive plastic container.

10. Basic Apparatus Settings and Standard Operating Conditions
10.1 Installation of the apparatus requires placement on a level surface and connection of all utilities. Engineering and technical support for this function is required, and the user shall be responsible to comply with all local and national codes and installation requirements.

10.2 Operation of the combustion analyzer, associated equipment, instrumentation, and computer system requires setting a series of testing variables to prescribed specifications. Some of these settings are established by component specifications, others are operating conditions that are monitored or controlled by the computer software or by operator adjustment.

10.3 Settings Based on Component Specifications:
10.3.1 Injector Nozzle Opening Pressure - Each time the nozzle assembly is reassembled or replaced, or both, set the pressure-adjusting nut to release fuel in conformance with the requirements of the manufacturer, using a pressure sensor connected to the nozzle housing through an appropriate adapter. For additional details, refer to the instruction manual of the manufacturer.

10.3.2 Injector Nozzle Motion Sensor Position - Verify Sensor positioning using the appropriate function of the apparatus software. If required, manually adjust the position of the motion sensor by referring to the instruction manual of the manufacturer, using the appropriate function of the apparatus software.

10.3.3 Combustion Chamber Leakage Rate - Shall be less then 2.0 kPa/s, as measured during the automated check of the sealing integrity of the combustion chamber.

NOTE 4 - After the warm-up sequence (see 12.1.1) is finished, the computer system initiates an automatic diagnostic procedure consisting of zero-adjustment of the chamber dynamic pressure sensor (P1) and a chamber sealing integrity check. The chamber leakage rate is continuously monitored by the computer system throughout the test and in between tests.

10.4 Standard Operating Conditions:
10.4.1 Chamber Static Pressure (P0) - The average of 25 combustion cycles for Chamber Static Pressure is required to be within 2.40 MPa +/- 0.02 MPa.

10.4.2 Chamber Charge Air Temperature (T1), 510 °C +/- 50 °C.

10.4.3 Chamber Inner Wall Temperature (T2) - Initially set by the manufacturer, the surface temperature set-point is monitored and controlled by the computer. Operator adjustment of the controller set-point is required, in accordance with the calibration procedure.
10.4.3.1 The difference in temperature (T2max - T2min ) as determined and recorded by the computer, shall be less than 2.5 °C during a 25 combustion cycle measurement determination.

10.4.4 To ensure proper heat distribution and guard against malfunctioning of the heater element the temperature difference (T2 − T1) shall be within the tolerances, as referred to in the instruction manual of the manufacturer 9 for each of the 25 combustion cycles. The difference (T2 − T1) is monitored by the computer.

10.4.5 Fuel Injection Pump Temperature (T3), 35 °C +/- 2 °C.

10.4.6 Injector Nozzle Coolant Jacket Temperature (T4) - Set the coolant reservoir temperature (T5) to achieve an injector nozzle coolant passage temperature (T4) of 30.0 °C +/- 0.5 °C. T4 is determined and recorded by the computer. A temperature outside the range given during a 25 combustion cycle measurement indicates a possible malfunctioning of the cooling system.

10.4.7 Injection Actuator Air Pressure (P2), 0.75 MPa +/- 0.05 MPa.

10.4.8 Injection Period (IP):
10.4.8.1 The average injection period over 25 combustion cycles: 5.00 ms +/- 0.25 ms.

10.4.8.2 The individual injection period for each of the 25 combustion cycles: 5.00 ms +/- 1.00 ms.

10.4.8.3 Each individual injection period and the updated average is continuously monitored and recorded by the computer. If necessary, to comply with these requirements, the rack setting on the fuel pump can be adjusted manually.

11. Calibration and Quality Control Testing
11.1 Calibration - Calibrate the combustion analyzer (1) after it is installed and commissioned, (2) after replacement of critical parts or components of combustion chamber assembly, fuel injection system or instrument sensors, (3) after calibration of the injection actuator air pressure, chamber static pressure, or chamber dynamic pressure sensors, or (4) whenever check standard or QC sample determinations are not in statistical control, and the assignable causes for QC non-compliance have been suitably addressed.

11.2 Pre-calibration Procedures:
11.2.1 Start and warm-up the combustion analyzer (see 12.1.1).

11.3 Calibration Procedure - Two calibration reference materials are tested: (1) heptane to affirm that the combustion chamber charge air temperature setting produces ignition delay measurements for this material that are within specification limits and, (2) methylcyclohexane to affirm that the measurement sensitivity of the combustion analyzer produces ignition delay measurements for this material that are within specification limits.
11.3.1 Heptane Calibration Reference Material - Perform three consecutive ignition delay determinations.
11.3.1.1 To be an acceptable data set, each single result is required to be within 3.15 ms +/- 0.04 ms.

11.3.1.2 The average of three acceptable ID results is required to be within 3.15 ms +/- 0.02 ms.

11.3.1.3 If any of the three results is outside the limits, a system malfunction is suspected and diagnostic procedures to determine and remedy the problem are recommended before performing a new calibration. Refer to the instruction manual of the manufacturer.

11.3.1.4 If the average ID is outside the limits, the combustion chamber inner surface temperature controller set-point requires adjustment to cause a change in the combustion chamber charge air temperature.

NOTE 5 - ID increases when the combustion chamber inner surface temperature decreases and vice versa.

11.3.1.5 If the temperature controller set-point adjustment from the previous setting exceeds +/- 4 °C, a system malfunction is suspected and diagnostic procedures to determine and remedy the problem are recommended. Refer to the instruction manual of the manufacturer.

NOTE 6 - After a change of charge air cylinders, a temperature controller set-point adjustment beyond 4 °C can accommodate the extreme limits of the 20.9 % +/- 1.0 % by volume oxygen.

11.3.1.6 After a temperature controller set-point adjustment, wait at least 10 min before initiating a new calibration so that the combustion analyzer attains thermal equilibrium. Adequate temperature stability is determined and automatically controlled by the computer.

11.3.2 Methylcyclohexane Calibration Reference Material - Perform two consecutive ignition delay determinations.
11.3.2.1 To be an acceptable data set, each single result is required to be within 10.1 ms +/- 0.6 ms and the average of the two results is required to be within 10.1 ms +/- 0.5 ms.

11.3.2.2 If either of the two single results or the average of the two results is outside the respective limits, system performance is unacceptable and it is recommended that diagnostic procedures be used to determine and remedy the problem before performing a new calibration. Refer to the instruction manual of the manufacturer.

11.3.3 The combustion analyzer calibration is complete when both heptane and methylcyclohexane data sets are acceptable.

11.4 Quality Control (QC Testing) - Conduct a regular statistical quality assurance (quality control) program in accordance with the techniques of Practice D6299 or equivalent.
11.4.1 This test method requires quality control testing at the beginning of each operating period by a single ignition delay determination for both the check standard (heptane) and one QC sample.

11.4.2 The QC sample is a typical diesel fuel oil having an ignition delay that represents the primary range of use for the combustion analyzer.
11.4.2.1 If the combustion analyzer is used for testing fuels having a very wide range of ignition delay, it may be useful to have a second QC sample of a different ignition delay.

11.4.3 For locations using blends of oxygen and nitrogen as the source for charge air, conduct a QC test whenever there is a change from one cylinder to another.

NOTE 7 - The oxygen content of the new oxygen and nitrogen blend may differ from that of the previous source and can have a significant effect on ID measurements.

11.5 Check Standard - Perform a single ignition delay determination for heptane.
11.5.1 This determination is acceptable if it satisfies the limits protocol specified in Practice D6299 or equivalent.

11.5.2 Prior to having established ignition delay tolerances for heptane in accordance with Practice D6299 or equivalent, use warning limits of +/- 0.04 ms and action limits of +/- 0.06 ms, based on the average of the three acceptable ID results for heptane, as per 11.3.1.

11.6 QC Sample - Perform a single ignition delay determination for the QC sample.
11.6.1 This determination is acceptable if it satisfies the limits protocol specified in Practice D6299 or equivalent.

11.7 The combustion analyzer is fit-for-use when both the check standard (heptane) and the QC sample ignition delay determinations are acceptable. If the ignition delay determination for either material is not acceptable, conduct a new calibration before performing further ignition delay determinations.