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
7. Apparatus
7.1 General - This test method uses an integrated automated analytical measurement system (see Fig. 1) comprised of:
7.1.1 Combustion Chamber - A cylindrical block having a volume of 0.60 L +/- 0.03 L, with external heating elements, heat shield, and electrically actuated intake and exhaust valves. There is an opening at one end ofthe chamber to accommodate insertion of the fuel injection nozzle assembly and an opening at the other end of the chamber to accommodate insertion of intake, exhaust, and various

7.1.2 Fuel Injection System - A pneumatically actuated fuel injection system with fuel injection pump, injector nozzle assembly and associated sample reservoir to assure for proper and repeatable injection of calibration, QC material, and test specimens into the combustion chamber. The system includes:
7.1.2.1 Fuel Sample Reservoir - A metal reservoir having a nominal volume of 100 mL.

7.1.2.2 Fuel Injector Nozzle - A standard one-hole nozzle conforming to the requirements of DIN 73372. The nozzle is assembled to the body that incorporates a spring-loaded needle extension with screw and lock nut for adjusting the nozzle opening pressure setting; a fuel bleed passage connecting to an external bleed valve for bleeding fuel from the nozzle and nozzle body; and a positions motion sensor mounted in an adjustable housing near the injector nozzle needle extension pin, to determine when the nozzle needle lifts to initiate the start of injection.

7.1.3 Coolant System - A closed-loop circulating coolant system to control the temperature of the combustion injector nozzle. The system includes an auxiliary heat exchanger with built-in circulating pump and flow control valves.

7.1.4 Instrument Sensors - Sensors used to measure and either indicate the value of a variable or transmit the condition for control or data acquisition purposes such as:
7.1.4.1 Combustion Chamber Static Pressure Sensor (P0) - A sensor installed to measure the static pressure within the combustion chamber before and after each combustion cycle.

7.1.4.2 Combustion Chamber Dynamic Pressure Sensor (P1) - A sensor installed to measure the pressure within the combustion chamber during each combustion cycle. The pressure sensor is fitted with an integrated temperature sensor to record the operating temperature (T3) at the sensor.

7.1.4.3 Injection Actuator Air Pressure Regulator (P2) - A calibrated pressure regulator installed between the pneumatic air supply and the fuel injection pump actuator.

7.1.4.4 Combustion Chamber Inner Wall Temperature Sensor (T2) - A type K thermocouple with stainless steel sheath, inserted in a well fastened to the inner surface of the chamber.

7.1.4.5 Chamber Charge Air Temperature Sensor (T1) - A type K thermocouple with stainless steel sheath, inserted in the combustion chamber.

7.1.4.6 Fuel Injection Pump Temperature Sensor (T4) - A PT100 temperature sensor with stainless steel sheath, inserted into the fuel injection pump body.

7.1.4.7 Injector Nozzle Cooling Jacket Temperature Sensor (T5) - A PT100 temperature sensor with stainless steel sheath, inserted in the injector nozzle coolant passage.

7.1.4.8 Injector Nozzle Motion Sensor (N1) - A motion sensor, that can be adjusted to provide a suitable gap between its sensing surface and the end of injector nozzle needle extension pin to detect the start of fuel injection.

7.1.5 Computerized Control, Data Acquisition, Data Analysis andReporting System - A microprocessor controlled system connected to a computer with keyboard for manual entry of operating instructions, a monitor for visual observation of all testing functions, and a printer for printed copy output of test results. The computer-based system provides automated control of the relevant combustion analyzer and sub-system component functions and to collect and process all relevant signals from the injector nozzle needle motion sensor, and temperature and pressure sensors.

7.2 Refer to the instruction manual of the manufacturer 9 for detailed information.

7.3 Compressed Gas Pressure Regulators:
7.3.1 Charge Air Regulator - A two-stage regulator capable of controlling the downstream pressure to a minimum pressure of 2.40 MPa.

7.3.2 Pneumatic Air Regulator - A two-stage regulator capable of controlling the downstream pressure to a minimum pressure of 0.75 MPa.

7.4 Auxiliary Apparatus:
7.4.1 Diesel Fuel Oil Sample Filter - A single-use glass fiber, polytetrafluorethylene (PTFE), or nylon filter with a nominal pore size of 3 µm to 5 µm (micrometers) for use with a glass syringe.

7.4.2 Syringe - A glass syringe of a minimum volume of 100 mL.

8. Reagents and Materials
8.1 Calibration Reference Materials:
8.1.1 Heptane - With a minimum purity of 99.5 volume percent. The assigned IDARV for this material and this method is 3.15 ms (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.)

8.1.2 Methylcyclohexane - With a minimum purity of 99.0 volume percent. The assigned IDARV for this material and this method is 10.1 ms (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.)

NOTE 2 - Experience has found some MCH meeting the purity specification but which does not meet ignition delay ARV (typically 1 s to 1.5 ms shorter). It is recommended that new material be qualified prior to use.

8.2 Check Standard:
8.2.1 Heptane - With a minimum purity of 99.5 volume percent (see 8.1.1).

8.3 Quality Control Sample - A stable and homogeneous diesel fuel oil having physical and chemical properties similar to those of typical sample fuels routinely tested (Warning - Combustible. Vapor Harmful.)

8.4 Charge Air - A compressed air containing 20.9 % +/- 1.0 % by volume oxygen (O2), less than 0.5 mg/kg CO, less than 1.0 mg/kg CO2, less than 5 mg/kg H2O, less than 0.1 mg/kg NOX , less than 0.1 mg/kg SO2, and less than 0.1 mg/kg Total Hydrocarbon Content (THC). (Warning - Compressed gas under high pressure that supports combustion.)

NOTE 3 - This grade air is typically referred to as Continuous Emissions Monitoring Grade Air (CEM).

8.5 Coolant System Fluid - A 50:50 volume mixture of water and commercial ethylene glycol-based antifreeze (Warning - Poison. May be harmful or fatal if inhaled or swallowed.)
8.5.1 Antifreeze - A commercial automotive cooling system ethylene glycol-based solution.

8.5.2 Water - A distilled or reagent-grade, conforming to Specification D1193, Type IV.

8.6 Pneumatic Air - An oil free compressed air having less than 0.1 volume percent water (Warning - Compressed gas under high pressure that supports combustion.)