Different Tests Of Liquid Fuels @ Www.07 Met.TkDocument Transcript
Fuel & Furnaces
“Different Tests of Liquid
Muhammad Arslan Afzal
Mr. Abdul Khaliq Sb.
LIQUID FUEL TESTS
Viscosity is a measure of the resistance of a fluid which is being
deformed by either shear stress or extensional stress. In general terms it
is the resistance of a liquid to flow, or its "thickness". Viscosity describes
a fluid's internal resistance to flow and may be thought of as a measure
of fluid friction.
The word "viscosity" derives from the Latin word "viscum" for mistletoe. A
viscous glue was made from mistletoe berries and used for lime-twigs to
When looking at a value for viscosity, the number that one most often
sees is the coefficient of viscosity. There are several different viscosity
coefficients depending on the nature of applied stress and nature of the
fluid. They are introduced in the main books
on hydrodynamics and rheology
• Dynamic viscosity determines the dynamics of an incompressible
• Kinematic viscosity is the dynamic viscosity divided by the
density for a Newtonian fluid;
• Volume viscosity (or bulk viscosity) determines the dynamics of
a compressible Newtonian fluid;
• Shear viscosity is the viscosity coefficient when the applied stress
is a shear stress (valid for non-Newtonian fluids);
• Extensional viscosity is the viscosity coefficient when the applied
stress is an extensional stress (valid for non-Newtonian fluids).
Shear viscosity and dynamic viscosity are much better known than the
Dynamic viscosity is measured with various types of rheometer. Close
temperature control of the fluid is essential to accurate measurements,
particularly in materials like lubricants, whose viscosity can double with
a change of only 5 °C. For some fluids, it is a constant over a wide range
of shear rates. These are Newtonian fluids.
The fluids without a constant viscosity are called Non-Newtonian fluids.
Their viscosity cannot be described by a single number. Non-Newtonian
fluids exhibit a variety of different correlations between shear stress and
One of the most common instruments for measuring kinematic viscosity
is the glass capillary viscometer.
Viscosity is also measured by three makes of commercial viscometers
1. The Red Wood Viscometer
2. Saybolt Viscometer
3. Engler Viscometer.
In case of viscometers, a fixed volume of a liquid at a fixed temperature is allowed to
flow through a standard capillary tube and the time of flow is noted. The result is
sometimes described in terms of time taken by oil to flow through a particular instrument.
Vibrating viscometers can also be used to measure viscosity. These models such as the
Dynatrol use vibration rather than rotation to measure viscosity.
Extensional viscosity can be measured with various viscometers that apply extensional
stress.Volume viscosity can be measured with acoustic rheometer.
The ignition or autoignition temperature or kindling point of a substance is the lowest
temperature at which it will spontaneously ignite in a normal atmosphere without an
external source of ignition, such as a flame or spark. This temperature is required to
supply the activation energy needed for combustion
Measurement of ignition temperature:
Autoignition temperatures of liquid chemicals are typically measured using a 500 mL
flask placed in a temperature controlled oven in accordance with the procedure described
The ignition temperature of distillate fuel is measured by apparatus which includes a
block having an ignition cavity. The block is heated to an elevated temperature above the
ignition temperature of the fuel and then allowed to cool slowly. As it cools, samples of
fuel are injected into the ignition cavity at times which are controlled by a digital
computer. A pressure transducer and a thermocouple measure the pressure and
temperature, respectively, in the cavity. For each injected sample, the digital computer
measures ignition delay as the time between injection of a sample and ignition as
indicated by a peak in measured cavity pressure or cavity temperature. The ignition delay
is recorded as a function of the cavity temperature prior to fuel injection.
Using the temperature required for a given ignition delay, the octane rating of distillate
fuels may be estimated from a calibration curve established by comparing unit data with
results from the ASTM octane number test. It has been found that the ignition
temperatures of the tested distillate fuels fall on a smooth correlation curve which can be
used to provide octane number estimates for unknown fuels. These are in excellent
agreement with observed ASTM values.
Viscometers for Oil Viscosity Measurement
Viscosity measures a lubricant's resistance to flow (fluid thickness) at
temperature and is considered oil’s most important physical property.
Depending on lube grade, viscosity is tested at 40 and/or 100° Celsius.
Viscosity Measurement is extremely important for hydraulic oils, diesel
Enclosed gears & fuel oils.
Kittiwake supply a range of Viscometers
varying in price & sophisticated from the
Heated Viscometer & Unheated Viscometer,
which form part of the Fuel & Lube Oil
Laboratory equipment, to the more simple
Viscometers in the Oil Test Kit range, listed
DIGI Viscometer - Viscotube FG-K14828-KW
The Kittiwake DIGI Viscometer (or Viscotube)
uses a falling ball technique to measure the
viscosity of oil in centistokes. Three sizes of
ball are included in the kit.
Supplied complete with viscosity calculation The Kittiwake DIGI Viscometer
uses a falling ball technique for
software. viscosity measurement.
Kit also includes DIGI thermometer.
20-600 cSt @ 40°C using 3 sizes of ball.
Lubricating oils, hydraulic oil, warm fuel oil
The flash point of a flammable liquid is the lowest temperature at which
it can form an ignitable mixture in air. At this temperature the vapor
may cease to burn when the source of ignition is removed. A slightly
higher temperature, the fire point, is defined as the temperature at which
the vapor continues to burn after being ignited. Neither of these
parameters is related to the temperatures of the ignition source or of the
burning liquid, which are much higher. The flash point is often used as
one descriptive characteristic of liquid fuel, but it is also used to describe
liquids that are not used intentionally as fuels.
Every flammable liquid has a vapor pressure, which is a function of that
liquid's temperature. As the temperature increases, the vapor pressure
increases. As the vapor pressure increases, the concentration of
evaporated flammable liquid in the air increases. Hence, temperature
determines the concentration of evaporated flammable liquid in the air
under equilibrium conditions. Different flammable liquids require
different concentrations in air to sustain combustion. The flash point is
that minimum temperature at which there is a sufficient concentration of
evaporated fuel in the air for combustion to propagate after an ignition
source has been introduced. Flash point is basically the lowest
temperature at which there is enough fuel vapour to ignite.
Measuring flash point
There are two basic types of flash point measurement:
a) Cleveland Open Cup - ASTM D92
b) Pensky-Martens Closed Cup - ASTM D93
These two methods introduced by ASTM are known as Standard Measuring Methods.
Cleveland Open Cup - ASTM D92
In open cup testers the sample is contained in an open cup which is heated, and at
intervals a flame is brought over the surface. The measured flash point will actually vary
with the height of the flame above the liquid surface, and at sufficient height the
measured flash point temperature will coincide with the fire point.
Pensky-Martens Closed Cup - ASTM D93
Closed cup testers, of which the Pensky-Martens closed cup is one example, are sealed
with a lid through which the ignition source can be introduced periodically. The vapour
above the liquid is assumed to be in reasonable equilibrium with the liquid. Closed cup
testers give lower values for the flash point (typically 5-10 K) and are a better
approximation to the temperature at which the vapour pressure reaches the Lower
Flammable Limit (LFL).
The flash point is an empirical measurement rather than a fundamental physical
parameter. The measured value will vary with equipment and test protocol variations,
including temperature ramp rate (in automated testers), time allowed for the sample to
equilibrate, sample volume and whether the sample is stirred.
Methods for determining the flash point of a liquid are specified in many standards. For
example, testing by the Pensky-Martens closed cup method is detailed in ASTM D93,
IP34, ISO 2719, DIN 51758, JIS K2265 and AFNOR M07-019. Determination of flash
point by the Closed Cup Equilibrium method is specified in ISO 1523:2002.
Specific gravity is defined as the ratio of the density of a given solid or liquid substance
to the density of water at a specific temperature and pressure, typically at 4°C (39°F) and
1 atm (14.7 psi) , making it a dimensionless quantity.
Specific gravity measurement:
Hydrometer is used for determination of specific gravity upto 0.001.for higher values,
specific gravity bottle is used and for the semi solid fuel like tar, indirect mathod is used.
The operation of the hydrometer is based on the Archimedes principle that a solid
suspended in a liquid will be buoyed up by a force equal to the weight of the liquid
displaced. Thus, the lower the density of the substance, the lower the hydrometer will