natural graphite, n - in carbon and graphite technology, a material consisting predominantly of graphitic carbon, which forms in the earth’s crust as the result of igneous or metamorphic processes acting on carbonaceous materials.
DISCUSSION - The degree of crystalline perfection in these materials may vary. Natural graphite may contain significant quantities of gangue materials, either attached to or intercalated with graphitic carbon.
naturally aspirated aircraft engine, n - aircraft piston engine that breathes without forced means from either turbochargers or superchargers.
near–isotropic nuclear graphite, n - graphite in which the isotropy based on the coefficient of thermal expansion (25 - 500°C) is 1.10-1.15.
net heat of combustion, Qn (MJ/kg), n - the quantity of energy released when a unit mass of fuel is burned at constant pressure, with all of the products, including water, being gaseous.
DISCUSSION - The fuel can be either liquid or solid, and contain only the elements carbon, hydrogen, oxygen, nitrogen, and sulfur. The products of combustion, in oxygen, are carbon dioxide, nitrogen oxides, sulfur dioxide, and water, all in the gaseous state. In this procedure, the combustion takes place at a constant pressure of 0.1012 MPa (1 atm), and 25°C is the initial temperature of the fuel and the oxygen, and the final temperature of the products of combustion.
net heat of combustion - expressed as megajoules per kilogram. The net heat of combustion at constant pressure of a liquid or a solid fuel containing only the elements carbon, hydrogen, oxygen, nitrogen, and sulfur is the quantity of heat liberated when a unit mass of the fuel is burned in oxygen at a constant pressure of 0.101 MPa (1 atm), the products of combustion being carbon dioxide, nitrogen, sulfur dioxide, and water, all in the gaseous state, with the initial temperature of the fuel and the oxygen and the final temperature of the products of combustion at 25°C. The net heat of combustion6,8 is represented by the symbol Qn and is related to the gross heat of combustion by the following equation:
Qn(net, 25°C) = Qg(gross, 25°C) - 0.2122 x H
where:
Qn(net, 25°C) = net heat of combustion at constant pressure, MJ/kg,
Qg(gross, 25°C) = gross heat of combustion at constant volume, MJ/kg, and
H = mass % of hydrogen in the sample.
Newtonian flow, n - a Newtonian liquid is one that flows immediately on application of even the smallest force, and for which the rate of flow is directly proportional to the force applied.
Newtonian fluid, n - a fluid that at a given temperature exhibits a constant viscosity at all shear rates or shear stresses.
Newtonian oil or fluid, n - an oil or fluid that at a given temperature exhibits a constant viscosity at all shear rates or shear stresses.
NIST, n - acronym for National Institute of Standards and Technology.
NLGI, n - National Lubricating Grease Institute
NLGI number, n - a numerical scale for classifying the consistency range of lubricating greases and based on the Test Method D217 worked penetration.
no-flow point, n - the temperature corresponding to a specified degree of blockage of a screen by separated solids.
no-knock condition, n - for octane rating, where the knock intensity in all cylinders is less than light knock. Refer to Annex A1 for description of knock intensity.
nominal filtration rating, n - (Deprecated term) an arbitrary micrometre value for a filter medium indicated by a filter manufacturer.
nominal filtration rating, n - an arbitrary micrometre value indicated by a filter manufacturer. Due to lack of reproducibility this rating is deprecated.
nonaromatics fraction, n - portion of the sample eluted with n-pentane. The nonaromatics fraction is a mixture of paraffinic and naphthenic hydrocarbons if sample is a straight-run material. If the sample is a cracked stock, the nonaromatics fraction will also contain aliphatic and cyclic olefins.
noncombustive reaction, n - a reaction other than combustion or thermal degradation undergone by certain materials upon exposure to elevated temperatures.
non-compounded engine oil, n - a lubricating oil having a viscosity within the range of viscosities of oils normally used in engines, and that may contain anti-foam agents or pour depressants, or both, but not other additives.
DISCUSSION - In this test method noncompounded oil is also known as build-up oil.
non-graphitizable carbon, n - in carbon and graphite technology, a carbon which cannot be transformed into graphitic carbon solely by heat treatment up to 3000°C under inert atmosphere or reduced pressure (also known as a hard carbon).
non-Newtonian flow, n - a non-Newtonian liquid is one whose viscosity depends on the rate of shear. Some will not flow until the force applied is greater than a definite value called the yield point.
non-Newtonian oil or fluid, n - an oil or fluid that at a given temperature exhibits a viscosity that varies with changing shear stress or shear rate.
non-Newtonian oil or fluid, n - an oil or fluid that exhibits a viscosity that varies with changing shear stress or shear rate.
non-reference oil, n - any oil other than a reference oil, such as a research formulation, commercial oil, or candidate oil.
non-soap thickener (synthetic thickener, inorganic thickener, organic thickener), n - in lubricating grease, any of several specially treated or synthetic materials, excepting metallic soaps, that can be thermally or mechanically dispersed in liquid lubricants to form the lubricating grease structure.
non-standard test, n - a test that is not conducted in conformance with the requirements in the standard test method, such as running on an uncalibrated test stand, using different test equipment, applying different equipment assembly procedures, or using modified operating conditions.
normal distribution, n - the distribution that has the probability function:
nuclear magnetic resonance (NMR) spectroscopy, n - that form of spectroscopy concerned with radio-frequency-induced transitions between magnetic energy levels of atomic nuclei.