DYNAMOMETER AND POWER MEASUREMENT

Question 1

a device for simultaneously measuring the torque and rotational speed (RPM) of an engine, motor or other rotating prime mover so that its instantaneous power may be calculated

Answer 1

dynamometer

Question 2

used to provide simulated road

loading of either the engine or full powertrain

Answer 2

dynamometer

Question 3

can be used as part of a testbed for a variety of engine development activities, such as the calibration of engine management controllers, detailed investigations into combustion behavior, and tribology.

Answer 3

dynamometer

Question 4

are used for routine
screening of grip and hand strength, and the initial and ongoing evaluation of patients
with hand trauma or dysfunction. They are also used to measure grip strength in
patients where compromise of the cervical nerve roots or peripheral nerves is
suspected.

Answer 4

dynamometer

Question 5

are used for measuring the back, grip, arm, and/or leg strength of athletes, patients, and
workers to evaluate physical status, performance, and task demands. Typically, the
force applied to a lever or through a cable is measured and then converted to a moment
of force by multiplying by the perpendicular distance from the force to the axis of the
level.

Answer 5

dynamometer

Question 6

applies variable load on the prime mover (PM) and measures the PM’s ability to move or hold the RPM as related to the “braking force” applied. It is
usually connected to a computer that records applied braking torque and calculates
engine power output based on information from a “load cell” or “strain gauge” and a speed sensor.

Answer 6

brake dynamometer

Question 7

provides a fixed inertial mass load, calculates the power
required to accelerate that fixed and known mass, and uses a computer to record RPM
and acceleration rate to calculate torque. The engine is generally tested from somewhat
above idle to its maximum RPM and the output is measured and plotted on a graph.

Answer 7

inertia dynamometer`

Question 8

dynamometer provides the features of a brake dyno system, but in addition,
can “power” (usually with an AC or DC motor) the PM and allow testing of very small
power outputs (for example, duplicating speeds and loads that are experienced when
operating a vehicle traveling downhill or during on/off throttle operations).

Answer 8

motoring dynamometer

Question 9

where the engine is held at a specified RPM (or series of usually
sequential RPMs) for a desired amount of time by the variable brake loading as
provided by the PAU (power absorber unit). These are performed with brake
dynamometers.

Answer 9

Steady state

Question 10

the engine is tested under a load (i.e. inertia or brake loading), but allowed
to “sweep” up in RPM, in a continuous fashion, from a specified lower “starting” RPM to
a specified “end” RPM. These tests can be done with inertia or brake dynamometers.

Answer 10

Sweep test:

Question 11

usually done with AC or DC dynamometers, the engine power and
speed are varied throughout the test cycle. Different test cycles are used in different
jurisdictions. Chassis test cycles include the US light-duty UDDS, HWFET, US06,
SC03, ECE, EUDC, and CD34, while engine test cycles include ETC, HDDTC, HDGTC,
WHTC, WHSC, and ED12.

Answer 11

Transient test:

Question 12

Types of sweep tests

Answer 12

Inertia sweep, Loaded sweep

Question 13

provides a fixed inertial mass flywheel and
computes the power required to accelerate the flywheel (the load) from the starting to
the ending RPM. The actual rotational mass of the engine (or engine and vehicle in the
case of a chassis dyno) is not known, and the variability of even the mass of the tires
will skew the power results.

Answer 13

Inertia sweep:

Question 14

Loaded sweep, of the brake dyno type, includes

Answer 14

Simple fixed load sweep:, Controlled acceleration sweep:,Controlled acceleration rate: sweep test, steady state testing

Question 15

a fixed load - of somewhat less than the output of the engine -
is applied during the test. The engine is allowed to accelerate from its starting RPM to
its ending RPM, varying at its own acceleration rate, depending on power output at any
particular rotational speed.

Answer 15

Simple fixed load sweep:

Question 16

similar in basic usage as the (above) simple fixed load
sweep test, but with the addition of active load control that targets a specific rate of
acceleration. Commonly, 20fps/ps is used.

Answer 16

Controlled acceleration sweep:

Question 17

used is controlled from low power to
high power engines, and overextension and contraction of “test duration” is avoided,
providing more repeatable tests and tuning results.

Answer 17

Controlled acceleration rate:

Question 18

will almost always be suspect, as many “sweep” users ignore the
rotating mass factor, preferring to use a blanket “factor” on every test on every engine
or vehicle. Simple inertia dyno systems aren’t capable of deriving “inertial mass”, and
thus are forced to use the same (assumed) inertial mass on every vehicle tested.

Answer 18

sweep test

Question 19

Transient test characteristics

Answer 19

Aggressive throttle movements, engine speed changes, and engine motoring

Question 20

A dyno that is coupled directly to an engine is known as

Answer 20

engine dyno

Question 21

A dyno that can measure torque and power delivered by the power train of a vehicle
directly from the drive wheel or wheels without removing the engine from the frame of
the vehicle), is known as

Answer 21

chassis dyno.

Question 22

provide a quick load change rate for rapid
load settling. Most are air cooled, but some are designed to require external water-
cooling systems.

Answer 22

Eddy current type absorber

Question 23

require an electrically conductive core, shaft, or disc
moving across a magnetic field to produce resistance to movement. Iron is a common
material, but copper, aluminum, and other conductive materials are also usable.

Answer 23

Eddy current dynamometers

Question 24

is similar to an eddy current dynamometer, but a fine magnetic
powder is placed in the air gap between the rotor and the coil. The resulting flux lines
create “chains” of metal particulate that are constantly built and broken apart during

rotation, creating great torque.

Answer 24

powder dynamometer

Question 25

use a magnetic rotor, sometimes of AlNiCo alloy, that is
moved through flux lines generated between magnetic pole pieces. The magnetisation
of the rotor is thus cycled around its B-H characteristic, dissipating energy proportional
to the area between the lines of that graph as it does so.

Answer 25

Hysteresis dynamometers

Question 26

are a specialized type of adjustable-speed
drive. The absorption/driver unit can be either an alternating current (AC) motor or a
direct current (DC) motor. Either an AC motor or a DC motor can operate as a generator
that is driven by the unit under test or a motor that drives the unit under test.

Answer 26

Electric motor/generator dynamometers

Question 27

used to blow air to provide engine load. The torque absorbed by a fan brake
may be adjusted by changing the gearing or the fan itself, or by restricting the airflow
through the fan. Due to the low viscosity of air, this variety of dynamometer is inherently
limited in the amount of torque that it can absorb.

Answer 27

Fan brake

Question 28

has a series of friction discs and steel plates similar to the clutches in
an automobile automatic transmission. The shaft carrying the friction discs is attached
to the load through a coupling. A piston pushes the stack of friction discs and steel
plates together creating shear in the oil between the discs and plates applying a torque.

Answer 28

Force lubricated oil shear brake

Question 29

consists of a hydraulic pump (usually a gear-type pump), a
fluid reservoir, and piping between the two parts. Inserted in the piping is an adjustable
valve, and between the pump and the valve is a gauge or other means of measuring
hydraulic pressure. In simplest terms, the engine is brought up to the desired RPM and
the valve is incrementally closed.

Answer 29

Hydraulic brake

Question 30

Invented by British engineer William Froude in 1877 in response to a request by the
Admiralty to produce a machine capable of absorbing and measuring the power of large
naval engines,[4] water brake absorbers are relatively common today.

Answer 30

Water brake-type absorber

Question 31

are symmetrical; a 300 kW AC dynamometer
can absorb 300 kW as well as motor at 300 kW. This is an uncommon requirement in
engine testing and development. Sometimes, a more cost-effective solution is to attach
a larger absorption dynamometer with a smaller motoring dynamometer.

Answer 31

Compound dynamometers