Putting engines
through their paces
FPT Motorenforschung
AG is based in the Swiss town of Arbon and develops engines destined
for the vehicles and machinery of CNH Industrial's Powertrain
segment. Some 220 staff work on site to create new FPT products
for commercial vehicles, construction equipment and agricultural
machinery and for use in industrial and marine applications.
The engines are put through their paces on a total of 30 test
benches. To measure their efficiency, FPT Motorenforschung uses
tools such as the Series M5 pressure transmitters from KELLER.
FPT Motorenforschung's development work focuses primarily on
reducing exhaust emissions and achieving a high power density,
low fuel consumption, a long service life and maximum reliability.
An engine's efficiency depends largely on the extent to which
the flow of air into the combustion chamber and that of the exhaust
gases back out again are unimpeded.The pressure here will be
under I 0 bar.The main priority is to get extremely accurate
and highly dynamic measurements using absolute sensors.
KELLER developed its M5 series to meet these specific engine
testing requirements and several of these devices are used at
various places on the engine during tests.To obtain a reliable
analysis of pressure conditions and losses, it is important to
take measurements as close as possible to the individual cylinders
on the inlet side.The varying geometry of the intake manifold
poses an additional challenge as it means that each cylinder
is supplied with a different amount of air, something that has
to be avoided as much as possible.
On the outlet side, too, the combustion gases in the individual
cylinders can cause unwanted interactions between pressure surges
or pulses.The pressure sensors measure these processes on the
inlet and outlet sides locally and with a high level of phase
fidelity.
When testing engines, it is important for the sensors not to
be sensitive to structure-borne noise as the sounds and vibrations
from the engine cannot be allowed to interfere with the measurements.The
measuring slot should be sealable with a plug once measurements
have been taken and should be as resistant as possible to air
flows. This application can also lead to compensating currents
of up to 40 A being generated by the engine battery — these
must not be allowed to influence the sensor-. These requirements
were met in full when the MS sensor was developed.
Other characteristics of the pressure transmitter also give it
an edge in this specific field of use: no bonding wires are needed
in the vicinity of the medium, while there are also no connectors
between the sensor and the electronic system.This removes any
additional contact resistances and sources of faults.The cable
gland is hermetically sealed (IP67) to minimise external influences
on the cable. Most of the electronic system is fitted externally,
enabling it to be positioned in a noise-free area.
THE MS SERIES — ULTRA-FAST MINIATURE PRESSURE TRANSDUCERS
The pressure sensors in the M5 HB series deliver extremely fast
and precise measurements to an accuracy of 0.1%FS up to I 80°C.The
pressure connection to the M5 fine thread is designed for both
static and dynamic measurements such as pressure pulses. Their
miniature size makes these sensors ideal for local measurements.
The sensors main attributes are its very low dead volume and
its good venting capability. It uses a rear-side technology without
a transfer medium that also helps to minimise the attenuation
of the measurement signal. No sealants, adhesives or capillaries
are needed either.
To prevent any unnecessary impact on flow conditions, the process
connection should be as short as possible and, in terms of handling,
able to be installed easily even in narrow tubes.The sensor is
thus also very lightweight and able to withstand rapid acceleration.
The M5 series is available with or without an electronic system.The
KELLER team's top priority when devel- oping its electronic system
was signal fidelity up to the limit frequency of 50 kHz.
The M5 HB pressure transmitters (i.e. with an electronic system)
were optimised in line with FPT Motorenforschung AG's technical
specifications and have been in use for over two years now.
A WIDE RANGE OF POTENTIAL USES IN ENGINE RESEARCH
FPT Motorenforschung uses M5 sensors with electronic systems
on all of its engine test benches. The company takes measurements
inside components such as oil, fuel and water pumps, injector
lines, inter-coolers, heat exchangers and intake and exhaust
ducts. Logging the pressure conditions enables any fluctuations,
peaks or other generally unusual pressure phenomena to be detected.The
engineers can then use these values as a ba- sis for reworking
the design, further optimising the components and parameters
of the ECU (the control unit).
The data obtained makes it easier to extrapolate the dynamic
conditions inside the engines. For instance, a pressure loss
of I Pa at a volume flow of I m3/s — typical values for
the intake air volumes of large HGV engines —translates
into I W of lost performance. In practice, this means that a
50 mbar fall in pressure results in a flow loss of as much as
5 kW Consequently, this value must be kept as low as possible
to make the engine more efficient.
M5 sensors can also be used in the return pipes in injectors.
Because of how they are designed, injectors generate a return
flow through leaking and cooling.The pressure conditions in these
pipes are also measured and optimised, with the pressure range
being from one to five bar. Oil pressure is a further critical
factor in engine efficiency.Whereas it is usually too low in
engines running at low speeds, ft tends to be too high at high
speeds.
Rainer Linsenmeyer, head ofTest Engineering / Electronic Measurement
at FPT Motorenforschung AG, says: "As far as measuring oil
pressure was concerned, it was particularly important to find
a sensor that was small enough.This is because smaller sensors
have less of an impact on the actual flow conditions. Also, there
is often very
little space to install them with this kind of application, meaning
that a standard sensor was never going to be an option.
The M5 sensor ticks all the boxes. One particular benefit is
the fact that, after testing is complete, the openings for the
sensors can be sealed using a simple MS plug almost as if nothing
had changed.This means that any modifications to the system won't
distort the results of other tests. We're delighted that, in
the M5 sensor, we've found a reliable measuring instrument that
can be put to a wide range of uses on our test benches.We've
enjoyed an extremely constructive partnership with KELLER for
many years now. As well as offering good value for money, they
are a reliable and expert port of call if we have any technical
problems. With KELLER's production based in Switzerland, their
quality is as you would expect and we never have to wait long
for deliveries:'
FPT Motorenforschung AG is one of the seven research and development
centres of FPT Industrial, the brand of CNH Industrial group
dedicated to the design, production and sale of powertrains.
FPT Motorenforschung AG is involved in the most important and
pioneering projects of CNH Industrial's powertrain segment, with
a focus on fur- ther improving already existing and developing
fundamentally new technologies. FPT Motorenforschung has been
designing and manufacturing engines to the highest quality standards
in Arbon since 1982. As well as engines, the company also develops
its own testing technology. When choosing a solution for its
pressure measurements, FPT was looking for short delivery channels
and good service alongside high product quality and compliance
with technical specifications.
The company had already enjoyed many years of positive experiences
with KELLER and had found a partner whose products, like FPTs,
were also made in Switzerland: 'We've been using KELLER's X series
for our static and dynamic measurements for a few years now.
Our successful partnership reflects the benefits of having a
user and developer on each other's doorstep and the high degree
of reliability that the experts and KELLER's products both share,'
says Linsenmeyer.
KELLER AG has over 40 years' experience in producing piezoresistive
measurement technology and has been developing customised pressure
sensors for all manner of different applications ever since it
was founded.A further bonus is the company's great flexibility,
which enables requests from customers to be met accordingly.
"Having a close working relationship with our customers
is very important to us.They provide us with some productive
suggestions for improvements and some valuable experience from
actually seeing the applications in use. Of course, it's particularly
nice if they're based nearby like FPT Motorenforschung. It means
that our experts can see the situation for themselves up close
and get involved themselves if there are any technical problems:'
explains Bernhard Vetted, head of Development at KELLER.
July 2020
