Note: Descriptions are shown in the official language in which they were submitted.
103~g~4
The invention relates to liquid cooling systems for
rotary internal combustion engines and, more particularly, li-
quid cooling systems for the housing of the Wankel type rotary
internal combustion engine.
In liquid cooling systems for the housing assembly
of rotary internal combustion engines of the Wankel type, such
as disclosed in the United States Patent No. 2,988,065 which
issued to Felix Wankel on June 13, 1961, it is common practice
to provide in the housing cooling flow passages extending sub-
stantially parallel to the axis of the mainshaft and headerchambers in the housing end walls constructed and arranged to
provide end-to-end interconnection of the passages and thereby
provide serial flow of liquid through those passages. These
conventional cooling systems are exemplified in the U. S. Patents
to Lechler et al, No. 3,691,999 dated September 19, 1972, J.
Steinwart, No. 3,743,452 dated July 3, 1973, Turner et al, No.
3,289,647 dated December 6, 1966, C. Jones, No. 3,572,984 dated
March 30, 1971 and M. Bentele, et al, No. 3,007,460 dated Nov-
ember 7, 1961. It is well recognized that heat transfer to a
liquid at a specified temperature increases with an increase in
the velocity of that liquid and, therefore, it is desirable in
the aforesaid cooling systems to provide a high heat transfer
rate and to accomplish this high heat transfer by circulation of
liquid at high velocity. Thus, cooling systems constructed to
provide flow of a relatively small quantity of liquid at rela-
tively high velocity in a rotary engine would require a thermo-
stat and radiator of a size no larger than is required in the
cooling system of a conventional reciprocating internal combus-
tion of comparable size. To achieve this high velocity, the
present invention contemplates a cooling system in which flow
~ ~,
--2--
10369~
is promoted by convection, which also assists in carrying out
of the cooling passageways entrained bubbles of gas and water
vapor.
Accordingly, it is an object of this invention to
provide a cooling system for the housing of a rotary internal
combustion engine which efficiently effects transfer of heat
from the housing to the liquid coolant.
Another object of the present invention is to provide
a cooling system for the housing of a rotary internal combustion
engine wherein flow of coolant is promoted by convection.
A further object of this invention is to provide a
cooling system for the housing of a rotary internal combustion
engine wherein entrapment of gas and vapor is minimized.
Now, therefore, the present invention contemplates a
novel cooling system in a rotary internal combustion engine of
the Wankel type having a multi-lobe housing cavity wherein com-
bustion occurs in the area adjacent one of the junctures of the
lobes and wherein the normal operative position of the engine is
such that the area of highest heat flux on the housing extends
substantially vertically from a horizontal plane. ~he cooling
system for the housing of such engine comprises a plurality of
first cooling passageways or passes in the housing adjacent the
area of highest heat flux and extending substantially parallel
to the longitudinal axis of the mainshaft of the engine and with
header chambers in the housing end walls arranged to provide
end-to-end connection of the first cooling passageways so that
coolant will serially flow through successive first cooling pass-
ageways. The cooling system also calls for a coolant outlet port
at the top of the housing and a coolant inlet port in the housing
in the lower portion of the housing, the inlet port and outlet
~03~94~
port being in communication with ~aid first cooling passage-
ways to respectively pass coolant into and from the cooling
passageways. The inlet port, outlet port and header chambers
coact to provide for coolant flow through the cooling passage-
ways successively upwardly past the area of highest heat flux
whereby movement of coolant through the passageways from the
inlet port to the outlet port is promoted by convection. The
cooling system may also comprise a by-pass port means in the
housing through which a relatively small amount, as for example
10% of the total amount of cooling flowing through the inlet
port, is diverted into second cooling passageways or passes dis-
posed in the housing adjacent the area of lowest heat flux and
in communication with the outlet port to discharge heated coolant
into the latter.
The cooling system of this invention may also be sum-
marized in the following manner.
A cooling system for the housing of a rotary internal
combustion engine comprising a rotor eccentrically mounted on a
mainshaft so that the rotor planetates within a multi-lobed, sub-
stantially trochoidal-shaped cavity formed within the housing of
the engine. The engine is disposed in its normal operative pos-
ition with the major and minor axes of the cavity respectively
extending substantially vertically and parallel to a horizontal
plane. The combustion in the engine occurs in the area adjacent
one of the lobe junctures so that the area of highest heat flux
extends substantially along one side of the housing parallel to
the major axis of the cavity.
The cooling system for the housing comprises a plural-
ity of first cooling passageways in the housing adjacent the area
where the highest heat flux is produced and extending substantially
~ -4-
~03~
parallel to the longitudinal axis of the mainshaft. A header
means forming chambers in the housing at opposite ends of the
housing provides for connecting the first cooling passageways
together end-to-end to provide for series flow of coolant through
each of the plurality of first cooling passageways from one end
of the housing to the other and upwardly adjacent said area of
highest heat flux. An inlet means is provided in the housing at
a point below the minor axis of the trochoidal cavity and adjacent
the combustion exhaust gas discharge means to communicate the
cooling passageways to a source of coolant to supply the first
cooling passageways with coolant. The housing is also provided
with an outlet means at a point above the minor axis of the tro-
choidal cavity to communicate with the first cooling passageways
and receive heated coolant therefrom. Second cooling passageways
are in the housing adjacent the area where the lowest heat flux
is produced, which passageways extend substantially parallel to
the longitudinal axis of the mainshaft and in communication with
the outlet means. Downstream from the inlet means a bypass means
is provided to pass a portion of the coolant passing through the
first cooling passageways into the second cooling passageways.
The invention will be more fully understood from the
following description when considered in connection with the ac-
companying drawings in which:
Fig. 1 is an exploded isometric view of the housing of
a multi-rotor rotary internal combustion engine having a cooling
system according to this invention, and
Fig. 2 is a schematic drawing of the end view of the
engine of Fig. 1 showing the relationship of the major and minor
axes of the housing cavities to a horizontal plane and the heat
flux (Q/A) to which the housing is subjected during engine oper-
ation.
~ -4a-
'~ ":.
. .
~0369~
Now referring to the drawings and more specifically to
Fig. 1, the reference number 10 generally refers to the housing
of a rotary internal combustion engine of the Wankel type which
engine may be of the one rotor or multi-rotor type. For pur-
poses of illustration only, the invention is shown in Fig. 1 as
-4b-
10369~4
having application to a two rotor rotary internal combustion
engine. The housing 10 comprises two trochoid housing sections
12 and 14 separated by an intermediate wall section 16 and two
opposite end wall sections 18 and 20. These housing components
or sections 12, 14, 16, 18 and 20 are suitably aligned by dow-
els (not shown) extending through aligned openings 22 and secured
together into a unitary structure by tie bolts (not shown) which
extend through aligned openings (not shown) in each of the hous-
ing components. In the assembled condition the housing has two
substantially trochoidal shaped cavities 24 within which rotors
(not shown) are supported for planetation on a mainshaft (not
shown), the mainshaft extending through the opening 26 in inter-
mediate wall section 16 and end wall sections 18 and 20. The
housing sections 12 and 14 are each provided with an exhaust port
28 and an ignition means 30, such as a spark plug. The inter-
mediate housing 16 has a fuel and air supply inlet 32 which is
bifurcated and communicates with two intake ports 34 and 36 in
the opposite faces 37 of the intermediate housing. The intake
ports 34 and 36 function to pass fuel and air into the combustion
chambers (not shown) which are defined by the rotors (not shown)
and disposed in cavities 24. Obviously, the invention is not
limited to the intake ports 34 and 36. It is within the purview
of this invention that any suitable means may be employed to
provide a combustible mixture in the combustion chambers.
As best shown in Fig. 2, the engine in its normal op-
erative position is orientated relative to a horizontal plane H,
such that each of the major axes X--X and the minor axes Y--Y
are disposed to extend respectively substantially vertically and
horizontally relative to the plane H. Also, as is shown in Fig.
; 30 2, the relative positions of intake ports 34 and 36, exhaust
1036944
ports 28 and ignition means 30 are such that combustion pro-
duces a heat flux Q/A of varying degree as represented by the
broken line and its distance from outline of housing 10 (the
greater the distance the greater the degree of heat transferred
to the housing) of the engine. As herein described and as
shown in Fig. 2, the area of highest heat flux extends along
one side of the engine housing 10 and substantially parallel to
the major axes X--X of the housing cavities 24. In order to
minimize thermal distortion of housing lO as a result of the
heat flux Q/A, it is necessary to provide a cooling system for
the housing which compensates for this varying degree of heat
flux Q/A and, therefore, in accordance with this invention, hous-
ing 10 is provided with a liquid cooling system as hereinafter
described.
As shown in Fig. l, the cooling system comprises an
inlet port means 38 and an outlet port means 40 in end wall sec
tion 18 and a first coolant passageway means in housing 10 lo-
cated adjacent to the area of hiyhest heat flux to conduct a
liquid coolant from inlet port means 38 to outlet port means 40
through the housing and thereby absorb heat from housing 10. The
cooling system may also include a second coolant passageway means
in the housing lO located adjacent the area of lowest heat flux
and through which a small portion of the liquid coolant flowing
through inlet port 38 is directed to flow through the second
coolant passageway means.
The liquid cooling system, more specifically, provides
for disposing both inlet port means 38 and outlet port means 40
in end wall section 18 of housing 10. The inlet port means 38
is located in the housing at a point below minor axes Y--Y and
adjacent to or in alignment with major axes X--X. The outlet
10369~4
port means 40 is located in the housing at a point above minor
axes Y--Y and adjacent to or in alignment with major axes X--X.
As shown, end wall section 18 is divided by a plurality of webs
42 into an inlet header chamber 44, an intermediate header cham-
ber 46 and an outlet header chamber 48, the inlet port means 38
communicating with inlet chamber 44 to deliver liquid coolant
to the latter. The end wall section 18 is also provided with
passage 50 which communicates with inlet header chamber 44 to
receive liquid coolant from the chamber. This passage 50 con-
stitutes part of the first coolant passageway means and is inregister with a passage 52 of the adjacent housing section 12.
The passages 50 and 52 are in register with passages 54, 56 and
58 in the respective intermediate housing section 16, housing
section 14 and end wall section 20. The passages 50, 52, 54,
56 and 58 coact to provide a first pass of the plurality of
parallel passes or passages of the first coolant passageway
means. The passage 58 communicates with a return bend chamber
or intermediate header chamber 60 formed in end wall 20 by webs
62 and 64 to pass liquid coolant into the header chamber 60.
The end wall section 20 has another passage 66 which communicates
with header chamber 60 to receive liquid coolant for flow back
toward end wall 18. The passage 66 lies in register with pass-
ages 68, 70, 72 and 74 of housing sections 14, 16, 12 and 18,
respectively, which passages constitute a second pass of the
` plurality of parallel passes or passages of the first coolant
passageway means. The passage 74 communicates with intermediate
header chamber 46 to discharge liquid coolant into the latter.
A thlrd pass of the first coolant passageway means consists of
registered passages 76, 78, 80, 82 and 84 in housing sections
30 18, 12, 16, 14 and 20, respectively, which pass communicates with
1036944
intermediate header chamber 46 to receive coolant from the
latter. The passage 84 in end wall section 20 communicates with
a return bend chamber or intermediate header chamber 86 formed
in end wall section 20. This header chamber 86 also communi-
cates with a passage 88 in end wall section 20 to deliver li-
quid coolant to the latter. The passage 88 registers with sim-
ilar registered passages 90, 92, 94 and 96 in the respective
housing sections 14, 16, 12 and 18. These registered passages
88, 90, 92, 94 and 95 constitute a fourth pass of the plurality
of parallel passages of the first coolant passageway means and
function to pass heated liquid coolant into outlet header cham-
ber 48 in end wall section 18, which chamber communicates with
passage 96. From outlet header chamber 48 the heated liquid
coolant passes into outlet port means 40 which may be connected
to a thermostat (not shown), radiator (not shown) and a pump
(not shown) for cooling and recirculation to inlet port means
38. As is clearly evident from the foregoing description, li-
quid coolant is conducted from inlet port means 38 to outlet
port means 40 back and forth between end wall sections 18 and
20 through a plurality of passages which are positioned to re-
ceive liquid coolant at successively higher temperaturesas the
coolant absorbs heat from the housing, thereby utilizing con-
vection to promote the flow of liquid coolant. Thus, the vel-
ocity of flow is at a desired rate to achieve a heat transfer
rate without high quantative flow of liquid coolant and a rela-
tively large pump (not shown), if employed, and the attendant
increase in radiator and thermostat size.
The liquid cooling system may also provide a second
coolant passageway means for flowing liquid coolant in the area
adjacent the portion of the housing where heat flux Q/A is least.
1036944
This low heat flux is generally located in the area of the
fuel and air supply inlet 32 and exhaust ports 28 (see Fig. 2).
Since the heat transfer requirements in the area of least heat
flux is low, only a small quantity of liquid coolant is nec-
essary to achieve the desired heat transfer. Therefore, in
accordance with the present invention, a by~pass port means 98
is provided in web 62 of end wall section 20 to communicate
header chamber 60 with an adjacent header chamber 100 formed in
end wall section 20 between web 62 and a web 102. The by-pass
port means 98 is so sized that of the total flow of liquid cool-
ant entering header chamber 60, only a small amcunt, as for ex-
ample about 10~, is diverted into header chamber 100 through
by-pass port means 98. From header chamber 100 the liquid cool-
ant flows in a single pass to outlet header chamber 48, via
registered passages 104, 106, 108, 110 and 112 in housing sec-
tions 20, 14, 16, 12 and 18, respectively. The liquid coolant
then flows from outlet header chamber 48 together with the li-
quid coolant from the first coolant passageway means via outlet
port means 40. This fluid flow through the second coolant pass-
ageway means may for particular engines effect a transfer ofheat to the housing rather than from the housing in order to
provide a housing having minimal thermal distortion.
It is believed now readily apparent that the present
invention provides an efficient liquid cooling system for a
rotary internal combustion engine in which flow velocity of the
coolant through the engine housing is promoted by convection
since flow thereof from the coolant inlet to the coolant outlet
is in the same direction that temperature of the coolant is in-
creased. It is a system in which the provision of disposing
liquid coolant inlet and outlet ports in the same end wall
. .
_g_
~036944
section, eliminates in a multi-rotor engine, liquid coolant
inlet and outlet manifolds and provldes simplified housing
castings.
--10--
