ASTM D6890 Standard Test Method for Determination of Ignition Delay and Derived Cetane Number (DCN) of Diesel Fuel Oils by Combustion in a Constant Volume Chamber
7. Apparatus
7.1 General - This test method uses an integrated automated analytical measurement system comprised of: (1) a constant volume compression ignition combustion chamber with external electrical heating elements, suitable insulation and pneumatically actuated intake and exhaust valves, (2) a heated, pneumatically actuated fuel injection system with pump, injector nozzle assembly, and associated sample reservoir, (3) a coolant system with a liquid-to-air heat exchanger, filter, circulating pump and flow control valves, (4) temperature thermocouples, pressure gages and sensors, an injector nozzle needle motion sensor, compressed gas pressure regulators, control valves, pneumatic actuator components, and solenoid valves, and (5) a computer to control test sequencing, acquire and accumulate sensor signal data, provide processing calculations, and automatically output a printed report of some important test parameters (see Fig. 1).
7.2 See Annex A2, Combustion Analyzer Equipment Description and Specifications, for detailed information.
7.3 Compressed Gas Pressure Regulators:
7.3.1 Charge AirRegulator, a two-stage regulator capable of controlling the downstream pressure to a minimum pressure of 2.2 MPa.
7.3.2 Actuator Utility Compressed Air Regulator, a two-stage regulator capable of controlling the downstream pressure to a minimum pressure of 1.3 MPa.
7.3.3 Fuel Reservoir Utility Compressed Nitrogen Regulator, a single or two-stage regulator capable of controlling the downstream pressure to a minimum pressure of 350. kPa.
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 for use with a positive pressure delivery device such as a glass syringe or glass-lined metal syringe.
7.4.2 Positive Pressure Delivery Device, a non-reactive positive pressure delivery device such as a glass syringe or a glass-lined metal syringe.
8. Reagents and Materials
8.1 Calibration Reference Materials:
8.1.1 Heptane (n-heptane), with a minimum purity of 99.5 volume percent. The assigned IDARV for this material is 3.78 ms. (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.)
8.1.2 Methylcyclohexane (MCH), with a minimum purity of 99.0 volume percent. The assigned IDARV for this material is 10.4 ms. (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.)
NOTE 3 - Experience has found some MCH meeting the purity specification but which does not meet Ignition DelayARV (typically 1 millisecond to 1.5 milliseconds shorter). It is recommended that new material be qualified prior to use.
8.2 Check Standard:
8.2.1 Heptane (n-heptane), with a minimum purity of 99.5 volume percent. The assigned IDARV for this material is 3.78 ms. (Warning - Flammable. Vapor harmful. Vapor may cause flash fire.)
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, compressed air containing 19.9 volume percent to 21.9 volume percent oxygen, less than 0.003 volume percent hydrocarbons, and less than 0.025 volume percent water. For charge air cylinders supplied with a blend of oxygen and nitrogen, it is required that a quality control test be performed after an air cylinder has been changed. (Warning - Compressed gas under high pressure that supports combustion.)
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, commercial automotive cooling system ethylene glycol-based solution.
8.5.2 Water, distilled or reagent-grade, conforming to Specification D1193, Type IV.
8.6 Actuator Utility Compressed Air, oil free compressed air having less than 0.1 volume percent water supplied at a minimum sustained pressure of 1.5 MPa. (Warning - Compressed gas under high pressure that supports combustion.)
8.7 Fuel Reservoir Utility Compressed Nitrogen, compressed nitrogen having a minimum purity of 99.9 volume percent. (Warning - Compressed gas under high pressure.)
