FLOW-OPTlMlZED FLUlD MODULES

De velo pment Auxiliary Systems
Flow-Optimized Fluid Modules
Lubricating oil, coolant and fuel circuits cause flow losses and therefore have an influence on the
fuel consumption and CO2 emissions of internal combustion engines. Hengst describes innovative
manufacturing methods for producing fluid modules with flow-optimised ducts and reduced weight.
36
A u t ho r s
Dipl.-Ing., Dipl.-Wirtsch.-Ing.
(university of applied
sciences) Marian Baum
is Director of Development for Filters
and Modules at Hengst SE & Co. KG
in Münster (Germany).
Dipl. Wirtsch.-Ing. (FH)
Daniel Baumhöver
is Program Manager Sales OE Hengst
Industrial (Engines) at Hengst SE &
Co. KG in Münster (Germany).
Dipl.-Ing. Ingo Brunsmann
is Group Vice President for Original
Equipment at Hengst SE & Co. KG in
Münster (Germany).
Dipl.-Ing. (FH)
Cornelia Lehmann
is Project Engineer in the Testing
Department at Hengst SE & Co. KG in
Münster (Germany).
12I2014 Volume 75
Reduce Flow Resistance
The fluid circuits for oil, coolant and fuel
are components of the “energy consumers” in internal combustion engines, particularly through their flow losses. Flow
resistance in the lubricating oil, coolant
and fuel circuits must be overcome by
their respective pumps. Moreover, with
increasing differential pressure, the use
of energy for fluid delivery increases. As
such, as a component of fluid circulation,
a flow-optimized design of the filter
housing or the filter module can make a
contribution to increasing the efficiency
of engines. For example, a reduction in
pressure loss in the oil circuit by 1 bar
could allow for a reduction in fuel consumption in a diesel engine of the compact (golf) class (four-cylinder, 1.6 l
engine displacement) by up to 1.5 %.
In the design of filter housings (oil,
coolant, fuel), the state of the art is
­comprised of functional integration and
module formation, with the goals of
en­abling the shortest direct fluid flow
and reducing the number of interfaces.
Thereby, a high degree of functional
density and an efficient use of installation space are possible. Typical production methods for this purpose, which are
advantageous and suitable for large
series, are conventional aluminum die
casting and conventional plastic injection molding. With both of these methods, tool design (on/off tools) and realizable sliding directions (straight and
in­clined slides) do not always lead to
flow-optimized channel geometries, as
draft angles reduce channel cross-sections, and linear sliding geometries that
hit against each other typically produce
hard deflections. In addition, certain
design constraints may make elaborate
(and possibly several) cross-slides, underfloor slides, etc. necessary, resulting in
increased tool complexity. In addition,
the channels that are produced in such
a manner frequently must also be sealed
in a fluid-tight manner, from the direction of sliding. This requires additional
process steps, such as machining and
the installation of waterproofing and
sealing elements. In addition, the areas
to be sealed tend to involve risks of leaks,
such as those caused upon the machining of exposed shrink holes in the sealing surfaces.
Furthermore, this type of design
restrictions does not always lead to the
lowest possible use of materials, and, as
such, has effects on component weights,
which in turn affect the fuel consumption of the engine and/or the vehicle. In
addition, engine spaces that are becoming more and more tight demand the compact design of add-on components (such
as filter housings), taking into consideration the interfaces provided by the engine.
This leads to geometries that are no
longer able to be represented using conventional manufacturing methods. Some
options for overcoming such restrictions
are to be illustrated in this article.
Flow-Optimized Fluid Module
The three innovative design concepts, or
manufacturing methods, featured here
enable free channel flow shapes, thus
the shortest flow-optimized fluid channels. Thereby, the differential pressure
behavior of such a filter module, when
compared to a conventionally manufactured component, can be reduced. In
addition to the possibility of integrating
channels into tight installation spaces,
these methods offer the potential for
additional weight reduction through the
omission of any necessary sealing elements for demolding channels. Moreover, the shortest paths of fluid flow mean
less housing material, and thus a lighter
module weight. Furthermore, the three
manufacturing methods presented here
reduce or eliminate, to the greatest possible extent, the additional costs of machin­­
ing and assembly outlined above.
3D Free-Form Channels With
Salt Core Technology
The so-called “3D free-form method with
salt core technology” is presented here
as a first opportunity for optimizing
channel flow. This comprises a special
aluminum die-casting method, with
which the shaping occurs through the
combination of a standard die-casting
tool (on/off tool with linear slides) with
salt cores that are forfeited inserted in
this tool. The salt cores produced from
the liquid molten salt in a die-casting
tool represent the negative of the channel
geometry, and, subsequent to the casting
process, are flushed out of the aluminum
die-casting component. In addition to
free channel shapes, this enables good
surface qualities, which are likewise
important for flow-optimized fluid flow.
37
De velo pment Auxiliary Systems
Details on this manufacturing method
are shown in [1].
In order to show and evaluate the
potential of this manufacturing option of
free-from channels in relation to differential pressure, as an example, a simply
held oil filter housing has been designed
for an examination (large passenger car
up to a small commercial vehicle engine).
This was carried out in the two versions
of “free-form channel”, ❶, and “conventional die casting” with an on/off diecasting tool with linear slides, ❷. The
interfaces of oil inlet and outlet, the
screw connection points and the maximum installation space correspond to a
typical demand on an oil module. With
the variant for conventional die casting,
this brings about the fact that the shortest and thus most flow-optimized channel cannot always be presented; rather,
unfavorable and sharp deflections arise
in the channel geometry.
Moreover, with the “conventional die
casting” model, it is perceptible that,
upon the use of conventional slides, there
is a need for sealing elements. These
steel screw plugs used here represent a
weight disadvantage, in comparison to
the model in the 3D free-form method
(152 g). In addition, the housing with the
conventional die casting features a weight
of approximately 900 g; with the salt
core model, this is approximately 800 g,
which gives rise to another weight
advantage for the 3D free-form method
of the salt core model.
A comparative CFD calculation was
generated for these two oil modules. The
following were assumed as input boundary conditions for the calculation: SAE
15W40 medium engine oil, oil temperature of 120 and 30 °C, oil flow rate of 70 l/
min). The pressure loss in the channels
was evaluated. The comparative flow calculation of the two models of “free-form
channels” and “conventional die casting”
is summarized in ❸ and shows the potential offered by salt core technology for
reducing flow resistance. With the provided connection dimensions, solely
through the modified channel flow, an
improvement of 0.56 bar with a typical
operating point with a 120 °C oil temperature could be obtained, which can be
expressed in a fuel savings of up to 0.84 %
with the example of a diesel engine of the
golf class. At lower operating temperatures, such as upon a cold start, the presented effect of flow optimization through
free-form channels is even more effective,
due to the higher oil viscosity (1.08 bar at
30 °C oil temperature). In principle, the
shown advantages also apply to the methods described below.
3D Free-Form Channels in
Half-Shell Construction
The so-called “3D free-form method in
half-shell construction” represents an
additional option for the optimization of
channel flow. This comprises the joining
together of two conventional aluminum
die-casting components, where each of
the two die-casting components forms
one-half of the channel. ❹ shows an
application in shell construction made of
aluminum die casting. The fluid management module conducts both oil and
coolant, and distinguishes itself by its
low level of differential pressure.
Various processes are available for the
joining together of the two shells. When
screwing together or shrinking, the shell
halves are connected to each other
through connection elements such as
screws or rivets. Depending on the application, a seal in the form of a metal
beaded gasket, a metal carrier seal or a
profile surface seal is necessary. Welding
the shell halves represents an additional
method. An additional sealing element
may be thereby omitted. A gluing of the
shell halves is also possible; no additional
sealing is required in this case. The shell
construction may also be ap­­plied in the
plastic injection molding process. Compared to the conventional primary shaping method, the primary shaping tools
for the half-shells can be structured very
simply, as no cross-slides, or fewer crossslides, are required for the realization of
channels.
3D Free-Form Channels
with the Gas/ Water Injection
Technique
The gas/water injection technique
(GIT-WIT) is a special injection molding
❶Oil filter housing in 3D free-form channel salt
core technology for CFD calculation (0.13 bar
­differential pressure input and output channel at
120 °C and 70 l/min)
❷Oil filter housing in conventional die casting
for CFD calculation (0.69 bar differential
pressure input and output channel at 120 °C
and 70 l/min)
38
Pressure distribution (dark: low
pressure, bright: high pressure)
Pressure distribution of output
channel (green: low pressure,
red: high pressure)
Differential pressure Input and
output channel at 30 °C and
0.36
1.44
70 l/min [bar]
Pressure distribution of input
channel (blue: low pressure,
red: high pressure)
Pressure distribution of output
channel (blue: low pressure,
red: high pressure)
❸Comparative flow calculation of the two models of “3D free-form channel salt core technology” (left) and
“conventional die casting” (right)
method, and enables the manufacturing
of components with free-form channels
made of thermoplastic material, but also
during first studies made of zinc, magnesium or aluminum. In the first operating step, the molten mass is injected
into a primary shaping tool under high
pressure. Subsequently, in the second
step, water with an upstream gas bub-
ble of a compressible medium is
injected into the tool. The formation of
the channel takes place through the
controlled displacement of the molten
mass into secondary cavities opened
after the filling. Even asymmetrical Y
channels with high tolerance requirements can be realized. This method
enables good surface qualities on the
inside of the channel, which realizes
further potential with regard to the
reduction in differential pressure.
Depending on the application, complete fluid management modules can be
produced with this method. An example
of this is the multifunctional plastic
module shown in ❺, which is mounted
inside the V space of the Audi V6 engine
block beneath the intake system. In a
small installation volume, the highly
integrated component combines a crankcase cover, free-form channels for the
distribution of the coolant, a crankcase
pressure control valve, a ventilation system and an oil mist separator with a
multi-cyclone and pressure relief valve.
GIT-WIT components may also be integrated with other thermoplastic parts.
The hybrid design represents a special
construction. This means the joining
together of two components of different
materials. This enables, for example,
combining the advantage of a GIT-WIT
component with the advantages of an
aluminum die-cast component.
Conclusion and Outlook
Simply the CFD calculation of the sim­
plified model of an oil filter, as shown
above, could indicate the advantages of
salt core technology in reference to the
reduction in pressure loss. For the
method described here, this applies to
shell construction and GIT-WIT in a
comparable scope. If, in the next step,
there is a closer look into complete filter
systems, which may contain, in addition
to the fluid filtration function, many
additional components and functions,
such as oil cooling through a heat
❹Application of fluid management module in shell construction
12I2014 Volume 75
39
De velo pment Auxiliary Systems
exchanger, pressure controls
regarding output resetting
or bypass valves, temperature control through
thermostat valves,
etc., the
❺Multifunctional plastic module
with the gas/water injection technique
(GIT-WIT)
40
great potential of optimized channel
geometries through new manufacturing
options becomes even more clear, since
all such individual functions in the overall system of the fluid module can be
connected to each other in the shortest
paths.
With the advanced method for aluminum die casting and plastic injection
molding presented here, the designers
are given new design freedom to
integrate the fluid flow of oil,
coolant or fuel in the “shortest paths,” and thus realize a design that is
optimized for differential pressure and
weight. This is an
important contribution for a fuelsaving design of
engine components. In
addition, there are further potentials in
fluid delivery, fluid flow and fluid clean-
ing in the optimization and electrification of pumps and valves, in the optimization of filter media and filter inserts,
and of heat exchangers, and in the
increasing use of material combinations
in the so-called “hybrid design”.
Reference
[1] Kallien, L.; Böhnlein, C.; Dworog, A.; Müller, B.:
Results from the 3-D free-form research project –
media-conveying channels in die casting. In:
Giesserei (100) 2013, No. 12, pp. 36-44
Thanks
The authors would like to thank all employees
of Hengst SE & Co. KG who have contributed
to this article.