U.S. patent number 3,765,479 [Application Number 05/110,727] was granted by the patent office on 1973-10-16 for liquid cooled engine.
Invention is credited to Robert F. Fish.
United States Patent |
3,765,479 |
Fish |
October 16, 1973 |
LIQUID COOLED ENGINE
Abstract
A novel engine cooling system which incorporates a special heat
exchanger. The heat exchanger replaces the conventional exhaust
inlet or inlet manifold of an internal combustion engine. The heat
exchanger includes an exhaust conduit having an inlet portion, an
intermediate portion and an outlet portion. Encompassing walls
define two separate flowpaths for coolant such that the coolant is
in thermal communication with the exhaust conduit. A first one of
these passages extends only over the inlet portion of the exhaust
conduit; the other of the coolant passageways extends over the
intermediate and outlet portions of the conduit although it can,
and, in the embodiment shown, does extend over the inlet portion as
well. The heat exchanger is connected to receive exhaust gases from
the engine. Its coolant passageways are connected in a circuit
which includes an inlet by which make-up water is introduced into a
pump which forces fluid through the first passageway of the heat
exchanger into the cooling passages of the engine from whence it is
circulated back to the inlet side of the pump when the coolant has
a temperature below a selected value. When the coolant temperature
rises above that value, it is permitted to flow past a thermostatic
valve to the second coolant passageway of the heat exchanger, after
which it is exhausted to the exhaust gas stream. The heat exchanger
is oriented so that one portion of the second coolant passageway is
disposed above other portions and the conduit is arranged so that
flow is confined at one point along the length of the exhaust
conduit to flow in the region of that uppermost point whereby the
second fluid passageway is maintained substantially full of coolant
from that point upstream.
Inventors: |
Fish; Robert F. (Costa Mesa,
CA) |
Family
ID: |
22334593 |
Appl.
No.: |
05/110,727 |
Filed: |
January 28, 1971 |
Current U.S.
Class: |
165/51; 165/103;
60/310 |
Current CPC
Class: |
F01N
3/04 (20130101); F28D 7/106 (20130101); Y02T
10/12 (20130101); Y02T 10/20 (20130101) |
Current International
Class: |
F28D
7/10 (20060101); F01N 3/04 (20060101); F28f
027/02 () |
Field of
Search: |
;165/50,51,103,35,39,40 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sukalo; Charles
Claims
I claim:
1. For use in cooling an engine which has an exhaust gas exit port
and has an inlet opening and an outlet opening for receiving and
discharging fluid, respectively:
a heat exchanger comprising an exhaust conduit formed by an
encompassing wall and defining an inlet portion for receiving
exhaust gas from the engine exit port, an intermediate portion, and
an outlet end portion for discharging exhaust gas that has
traversed said intermediate portion after entering at the inlet
portion;
a jacket comprising said encompassing wall and an overlying outer
wall, said jacket being formed to define two passageways capable of
conducting liquid coolant, one of said passageways extending over
the inlet portion of said exhaust conduit, the other one of said
passageways extending over the intermediate portion of said exhaust
conduit; and
means interconnecting said heat exchanger and said engine such that
exhaust gas is permitted to flow to said exhaust conduit, coolant
is permitted to flow from said one passageway to said engine inlet,
and fluid from said engine outlet is permitted to flow to said
other one of said passageways.
2. The invention defined in claim 1 in which said other one of said
passageways is formed with an outlet opening which opens at the
interior of said exhaust conduit.
3. The invention defined in claim 2 in which said jacket further
comprises means for insuring that said other one of said
passageways is substantially completely filled with coolant along
an initial portion of its length before fluid can be discharged
from said outlet opening.
4. The invention defined in claim 1 in which said jacket comprises
means for insuring that said other one of said passageways is
substantially completely filled with coolant along an upstream
portion of its length, said means comprising mounting means for
mounting said conduit with one portion of said other one of said
passageways uppermost and of dam means in the form of a dam
interconnecting said inner and outer walls except in the region of
said one portion of said other of said passageways for confining
flow to that one portion.
5. In combination:
an elongate exhaust conduit comprising an inlet section, an
intermediate section and an outlet section, said conduit being
formed with openings in its inlet section by which exhaust gases
may be admitted thereto so that they will traverse the conduit from
its inlet section through its intermediate section to be expelled
at said outlet section;
means comprising a first enclosing wall overlying portions of said
exhaust conduit at its inlet section and defining a first
passageway for coolant having inlet and outlet openings;
means comprising a second enclosing wall overlying portions of said
conduit at its intermediate section and at its outlet section and
defining inlet and outlet openings; and
means for orienting said conduit and enclosing walls such that one
portion of the flowpath formed by said conduit and said second
enclosing wall is uppermost in the vicinity of the juncture of said
intermediate section and said outlet section of said conduit and
for confining flow of fluid along said second passageway to flow
substantially at said uppermost region.
6. The invention defined in claim 5 together with an engine
comprising a plurality of spaced exhaust gas outlet ports, an inlet
opening for coolant, an outlet opening for coolant, and internal
passageways interconnecting said inlet and said outlet;
means interconnecting the outlet ports of the engine with the
openings in the inlet section of said exhaust conduit;
means for connecting said first passageway and the passageways
through said engine and said second passageway in series, in that
order, comprising a first conduit extending from said first
passageway defined by said first overlying wall to the inlet of
said engine, and comprising a second interconnecting conduit
extending from the outlet of said engine to said second passageway
defined by said second overlying wall.
7. The invention defined in claim 6 together with means for forcing
a flow of coolant into said first passageway and for permitting
flow of coolant from said passageways of the engine to said second
passageway when said coolant has a temperature exceeding a selected
value.
8. The invention defined in claim 7 in which said first passageway
is confined to the inlet area of said exhaust conduit and in which
said second passageway extends throughout the length of said
exhaust conduit.
9. The invention defined in claim 6 in which said conduit comprises
a horizontal section and an inverted U-shaped section, said first
enclosing wall overlying the horizontal section and said second
enclosing wall overlying the inverted U-shaped section.
10. The invention defined in claim 9 in which said U-shaped section
comprises a double-walled jacket and said means for confining the
flow to said one portion of said second passageway comprises a dam
disposed between the walls of the conduit and the second overlying
wall except at an upper region of said U-shaped section.
11. The invention defined in claim 9 which further comprises an
inlet conduit for make-up water connected to the inlet side of said
pump, means interconnecting the passageways of the engine with the
inlet side of said pump, said means for permitting flow of coolant
from the engine passageways to said second conduit comprising a
thermostatic valve.
Description
This invention relates to improvements in liquid cooled engines and
it relates particularly to an improved engine for marine
application.
One of the objects of the invention is to provide an improved
liquid cooling system for engines which combines the engine and its
coolant passageways with conduits, pumps, valves and a heat
exchange structure arranged for preheating liquid coolant before
introduction into the engine passages and for cooling the conduit
by which exhaust gases are lead from the engine. Provision of that
novel structure, and provision of the novel cooling system made
possible by its combination with an engine, are both objects of the
invention.
It will be apparent that the invention is not limited to use in
connection with inboard marine engines. However, the invention is
especially well-adapted for that application. Accordingly, it is
one of the objects to provide an improved cooling system circuit
and structure for that application. In certain classes of boats, it
is advantageous to mount the propulsion engine back adjacent to the
transom for direct connection to a steerable propeller drive and
propeller. Locating the engine in that fashion introduces a number
of problems. Special design is ordinarily required to ensure that
the engine structure imposes no serious limitation on the steering
system. In addition, space limitations ordinarily require that the
engine enclosure be as small as possible and that boat occupants be
seated and that gear be placed immediately adjacent to the engine.
That spatial limitation gives rise to the requirement that engine
heat be minimized by use of an effective and efficient cooling
arrangement. The exhaust gases, in the case of most engines, are
exhausted from a series of space ports. Consequently, the manifold
in which they are collected for explusion outside the boat extends
substantially over the whole length of the engine and is exposed at
the interior of the engine. In the case of V-8 engines two such
manifolds are employed. One of the objects of the invention is to
make it more feasible to employ an engine of conventional design
which requires large, exposed exhaust gas collection manifolds. A
related object is to provide an engine and engine cooling system
for limiting the maximum engine temperature and for greatly
reducing exhaust conduit temperature.
These and other objects and advantages of the invention are
realized by the combination with an engine of the kind that has
exhaust ports and internal passageways for fluid coolant of a heat
exchanger means comprising an exhaust gas conduit formed by an
inner wall and extending from the region of the engine exhaust
ports to an intermediate gas flow conducting portion and then to an
outlet section for discharging that exhaust gas and, which further
comprises a jacket formed by said inner wall and an overlying outer
wall, the outer wall being arranged to define two separate
passageways capable of conducting fluid coolant. One of the
passageways extends over that portion of the exhaust conduit at
which exhaust gas is received. The other passageway extends over
the intermediate and outlet sections of the exhaust conduit. The
exhaust conduit and jacket combination is arranged so that the
coolant passageways adjacent the intermediate section of the
exhaust conduit must remain full of coolant regardless of boat
motion.
In the drawings:
FIG. 1 is a pictorial view of a marine engine which is fitted with
the cooling circuit of the invention including the novel heat
exchanger structure that it provides;
FIG. 2 is a diagram of the cooling system circuit employed in the
engine of FIG. 1;
FIG. 3 is a pictorial view of the novel heat exchanger employed in
the invention;
FIG. 4 is a cross-sectional view taken on line 4--4 of FIG. 3;
FIG. 5 is a cross-sectional view taken on line 5--5 of FIG. 3;
FIG. 6 is a cross-sectional view taken on the vertical,
longitudinal midplane of the U-shaped portion of the heat exchanger
of FIG. 3, except that portions have been cut away to expose the
nature of the double walled construction; and
FIG. 7 is a cross-sectional view taken on line 7--7 of FIG. 6.
The engine selected for illustration in FIG. 1 is an internal
combustion unit which uses gasoline as fuel and is generally of the
same type and style as the engines used in passenger automobiles.
The engine is generally designated 10. Its block 12 is provided
with internal passageways by which a coolant may flow. A pulley 14
at the lower, forward end of the engine is driven by the engine's
crankshaft. A belt 16 transmits power from that pulley to a cam
driven pump 18 by which coolant is pumped through the system. The
numeral 20 designates an air filter; the element 22 is the oil
pan.
Thus far described the unit does not differ materially from an
ordinary automobile engine. The exhaust manifolds do differ,
however. They are heat exchangers. In this case it has been assumed
that the engine is of the V--8 variety with four exhaust ports at
the right and four at the left. The right exhaust manifold - heat
exchanger structure is designated by the numeral 24 and the left
one is designated 26. In this embodiment the exhaust gas is
expelled from the heat exchanger through a flexible conduit 28
through an opening in the boat's transom.
The boat's transom was omitted from FIG. 1 so that the propeller 30
and the propeller drive housing 32 would be visible. A part 34 of
the transmission's system is mounted forward to the transom and the
remainder is mounted behind it. Thus, the transom is placed just
rearward of the U-shaped portions 36 and 38 of the two heat
exchangers.
The boat may be steered by pivoting the propeller drive housing 32
about a pivot axis rearward of the transom. The force by which it
is made to pivot is applied to a tiller arm 40 which is arranged to
extend through or over the transom. Steering cables 42 extend in
opposite directions from a connection to the end of the tiller bar
40 through the spaces defined by the U-shaped rear sections 36 and
38 of the two heat exchangers. Guides for those cables are attached
to the housing within those spaces. This arrangement is
particularly advantageous. The U-shape of the heat exchanger
structure is doubly functional in that it ensures a generally
uniform high degree of exhaust gas cooling, as well as providing
protection for, and against, the tiller bar while providing a high
order of stability for the steering cable system in the region of
tiller bar movement.
The heat exchangers both include a passageway or conduit for
exhaust gases and two liquid coolant passageways. The inner exhaust
conduit is jacketed to form a double walled arrangement. Exhaust
gases flow in the conduit defined by the inner wall and the cooling
liquid flows in the space between the double walls. That space is
divided by blocking walls into two flowpaths. The exhaust conduit
is connected to the exhaust ports of the engine by laterally and
downwardly extending connecting conduits that are not visible in
FIG. 1. They can be seen in FIG. 3 and one of them is shown in
cross-section in FIG. 5. The exhaust conduit extends over the
length of the engine and through the U-shaped section of the heat
exchanger housing to an exit point at its junction with the
flexible conduit 28. One of the liquid passageways, in this
embodiment, extends only part way over the length of the exhaust
conduit. It extends over that part, called the inlet region, where
the exhaust gases are collected. Flow lines connected to the
exchanger structure at both ends of that passage are connected at
thier opposite ends to fittings at the forward end of the engine
block. The two conduits associated with heat exchanger 26 are
identified in FIG. 1 by the reference numerals 44 and 46. Another
conduit 48 interconnects the inner passages of the engine block
with the other liquid flow passage in exchanger 26. That passageway
has an outlet near the outlet of the exchanger at the point of its
connection with flexible conduit 28.
The interconnection of the engine pump, control valve, and the
several conduits with the passageways of the manifold structure is
illustrated in FIG. 2. In that figure, the engine block and its
cooling passages are illustrated by a block 50. The engine block is
provided with four exhaust gas outlet ports on each side. For
identification, one of those outlet ports has been designated 52 in
FIG. 2. The lateral, connecting conduit 54 leads from that exhaust
port opening to a port 56 which opens to the interior of the heat
exchange structure 24. The preferred arrangement is illustrated in
detail in FIG. 5.
Pump 18 of FIG. 2 is the same one designated 18 in FIG. 1. The
exhaust gases are collected in the exhaust conduit which is formed
by an inner wall generally designated 58 in FIG. 2. Those gases
pass through the conduit moving rearwardly through the U-shaped
section 36 of the structure and then emerge at the junction with
the flexible conduit 60. The latter is like the flexible conduit 28
with the exception that it is connected to the other of the two
heat exchangers.
The exhaust conduit portion of the exchanger is conveniently
considered to comprise three portions. The first is called an inlet
portion and is that portion of the conduit in which the exhaust
gases are collected. In general, that part extends from the forward
end of the exhaust conduit to a point just downstream of the
rearmost of the exhaust inlet openings. The numeral 62 in the case
of U-shaped member 38, and the numeral 64 in the case of U-shaped
member 36, identify a dam in one of the two liquid flow
passageways. The portion of the exhaust conduit which lies upstream
from the vicinity of that dam, and downstream from the inlet
portion is called the intermediate portion. That portion of the
exhaust conduit which lies downstream from the vicinity of the dam
is called the exhaust or outlet portion.
The liquid passageways are formed by the double walls of the
exchanger structure. In the case of manifold 24 the inner walls are
generally designated 58. Together with a portion of the outer wall
that is identified by the reference numeral 66, the inner wall 58
defines a passageway in which cooling liquid is preheated. This
passageway, numbered 68, is called the "preheating passageway."
Another portion 70 of the outer wall cooperates with wall 58 to
define a second passageway for liquid coolant which is called the
"exhaust conduit cooling passageway" or cooling passageway 72. In
this embodiment the preheating passageway extends approximately the
length of the inlet portion of the exhaust conduit. The cooling
passageway extends over the intermediate portion of the exhaust
conduit and over at least part of the exhaust portion of that
conduit. It may, and in this embodiment it does, extend over the
inlet portion of the exhaust conduit as well. In the intermediate
portion of the exhaust conduit, the cooling passageway 72 extends
substantially entirely around the exhaust conduit and the
passageway has been extended in the diagram to the inner region of
the U-shaped section 76 to illustrate that this is so.
The arrangement of the other exhaust manifold structure 26 is
similar. For identification, walls that define the exhaust conduit
are generally designated 74. The wall that cooperates with that
inner conduit to form the exhaust conduit cooling passage 76 is
designated 78. The wall that cooperates with inner wall 74 to form
the precooling passageway 80 is designated by reference numeral 82.
The inlet to that passage is designated 83 and the outlet is
numbered 84. The inlet 85 of the exhaust conduit cooling passageway
is at the forward end of the structure and the outlet 86 is at the
rearward end adjacent the connection with the flexible conduit 28.
In the lower part of FIG. 2 the precooling passageway has an inlet
86 and an outlet 87. The exhaust conduit cooling passageway has an
inlet 88 and an outlet 89. The engine block cooling passage system
includes inlets 91 and 92. It includes a recirculation outlet 90, a
primary outlet 94 and a safety bypass passageway 95. That outlet
bypasses the thermostatic valve 96. That valve is connected in
series between outlets 94 and the inlets 85 and 88 of the two
exhaust conduit passageways. Valve 96 and inlet 85 are
interconnected by the conduit 48 which was visible in FIG. 1. The
valve 96 and inlet 88 are connected by a conduit 98. Outlet 84 and
engine block unit 92 are interconnected by the conduit 46. On the
other side of the engine, engine block inlet 91 and precooling
passage outlet 87 are interconnected by a conduit 100. The outlet
side of pump 18 is connected to precooling passageway 80 by the
conduit 44 and is connected to the inlet opening 86 of the other
precooling passageway by a conduit 102. Cooling water, either sea
water or fresh water, enters the system at an inlet 104 and is
conducted by a passageway 106 to the inlet side of pump 108. The
recirculation outlet is connected by a conduit 108 back to the
inlet side of the pump.
Make-up water enters in at inlet 104 and proceeds by conduit 106 to
the inlet side of pump 18 where it is forced through conduits 44
and 102 to enter into the precooling passageways 80 and 68. The
water flows through those passageways and emerges at outlets 84 and
87. It then proceeds by conduits 46 and 100 to engine block inlets
92 and 91, respectively. Until that cooling water has reached a
temperature sufficiently high to open the thermostatic valve 96, it
exits the engine at outlet 90 and travels by conduit 108 to the
junction with conduit 106. Thereafter, it again flows to the inlet
section of pump 18 to be recirculated through the preheating
passageways 80 and 68. When this circulating water has reached a
temperature sufficiently high to open the thermostatic valve 96,
then the water is free to flow from the engine to conduits 48 and
98 to inlets 85 and 88 of the two exhaust conduit cooling
passageways 76 and 72. Those passageways must become entirely
filled with water downstream of their respective dams 62 and 64,
before any of the water they contain can be expelled to that
portion of the passageway that surrounds the outlet section of the
exhaust conduit. This result is achieved by providing the heat
exchange structure with a downstream section that is placed
generally above and higher than any other section of the exhaust
system. That section could be U-shaped, V-shaped, or otherwise
shaped to accomplish that result. In the preferred embodiment, the
U-shape is employed because it provides a number of advantages. It
removes the cooling function to the very rear of the boat, or at
least to the rear of the engine; it provides a very effective and
efficient means for protecting the tiller linkage and for guiding
the steering cables; and it has certain manufacturing
advantages.
The cooling circuit arrangement offers a number of advantages. It
is desirable to have the heat rise in the engine block occur as
uniformly as possible following engine start-up. The invention
helps to achieve that result by precirculating the water contained
in the engine block past the hottest portion, the inlet portion, of
the exhaust conduit. In the preferred form, that passageway is
limited substantially to the inlet portion of the exhaust conduit
as illustrated in FIG. 2. It will be shown subsequently, in
examination of FIG. 5, that the preheating passageway encompasses a
larger portion of the inlet portion of the exhaust conduit than
does the cooling passageway. The result is rapid preheating of the
cooling water. During initial operation that feature helps raise
engine block temperature uniformly and rapidly. Subsequently, it
minimizes extreme thermal differences by preventing direct
introduction into the heated block of very much colder sea water. A
further advantage is that the coolant that flows through the
preheated passageway derives its heat from the hottest part of the
exhaust conduit so that excessive heat rise is avoided.
In most small boat designs, the engine occupies a premium space.
The engines themselves are available in compact form. However, the
space that must be devoted to the engine is function not only of
engine size but is also a function of engine temperature. If the
temperature can be minimized, the size of the engine compartment 0r
enclosure can be reduced. In large measure, the size of that
compartment is determined by maximum engine temperature rather than
by average temperature. Accordingly, it is desirable to provide an
engine cooling system which minimizes peak temperature as well as
average temperature. Efficiency demands that the cooling system
contribute to engine warm-up. Within the engine itself, these
antithetical requirements are dealt with by the thermostatic valve.
In this case, it is desired not only to control block temperature
but also to control exhaust conduit temperature. Here, too, the
requirements are different during the start-up and the run
condition. In this case, the invention solves the problem by the
special arrangement of its exhaust manifold and heat exchange
structure and by the combination with that structure of the
thermostatic valve and the flow circuit arrangement. During the
start-up period, the short but large area preheating passageway
provides the heat input necessary to ensure the requisite degree of
block temperature uniformity. The preheating passageway is assisted
in its function by the thermostatic valve which ensures
recirculation of the coolant with minimum introduction of cold
water. After the engine is heated, the coolant is expelled from the
system and new coolant is introduced. That new coolant has a much
lower temperature and serves to carry away large quantities of heat
from the hottest, inlet section of the exhaust conduit. The cooling
passage of the exchanger is supplied with coolant only after the
engine is heated. It completely surrounds the intermediate portion
of the exhaust conduit to ensure that a maximum volume of water is
exposed, through a maximum heat exchange surface, to the heat of
the exhaust gases. The cooling passage is extended forwardly
adjacent the inlet portion of the exhaust passage to the extent
that the surface area of the exhaust conduit does not need to be
encompassed by the preheating conduit. In this embodiment,
approximately one-fourth of the conduit wall in the inlet portion
forms a part of the cooling passageway while three-fourths of that
wall forms a part of the preheating passageway. The heat exchange
structure is oriented so that dams 62 and 64 are at an uppermost
point thereby to ensure that the passageway is completely filled
with coolant upstream from that point. Below the dam, the coolant
is finally expelled into the stream of exhaust gases, cooling those
gases sufficiently so that flexible conduit of conventional
material can withstand their temperatures.
A preferred heat exchange structure is shown in FIGS. 3 through 7.
The whole structure 24 is shown in FIG. 3. It comprises a straight
section 110, having an end closure 112 at its forward end, and the
U-shaped section 36 at its rearmost end. The three sections are
cast separately and are bolted together. Bolts 114 connect the
forward closure to the straight section 112 and the bolts 116
connect the U-shaped section to the straight section. There are
four inlet conduits that afford communication for exhaust gases
from the exit ports of the engine to the inlet section of the
exhaust conduit. The conduit 54 is the one that was identified in
connection with the description of FIG. 2 and is the one shown in
cross-section in FIG. 5. The exit opening for the exhaust conduit
is designated 118 and it is on this element that the flexible
conduit 60 is fitted. The flexible conduit has been omitted from
the figure so that the outlet opening 86 of the coolant passage is
made visible. The threaded boss 120, which can be seen on the upper
inner surface of the U-shaped section 36, accommodates a fitting
through which the steering cable is run. Just below that, the
numeral 122 identifies a drain port for the cooling passageway. At
the front closure 112, elbow 124 is connected to the inlet opening
85 and forms part of conduit 48. Just below, the nipple 126 forms
part of the coolant passage outlet opening 84.
In this embodiment, the cooling passage extends over the length of
the straight section 112 and it continues into the lower forward
portion of the U-shaped section 36. Except in the region of the
four passageways by which exhaust gases are admitted into the
exchanger, the preheating passageway extends between the double
walls of the structure at its sides and at its bottom. Thus, in
FIG. 5 the exhaust conduit is defined by the inner walls 58. The
cooling passageway is defined by the lower one and the side ones of
those inner walls and by the outer walls 66 at the sides and the
bottom of the structure. The coolant passage is the upper one in
FIG. 5 and is defined by the upper wall 58 at its inside and the
wall 70 at its outside. The passageway is necked down at 130
because the outer wall is indented to accommodate the bolts
114.
That the two passageways are separated is illustrated by the
cross-sectional, pictorial view of end member 112 in FIG. 4. The
slot 132 communicates only with the upper coolant passage of the
straight section 110 and with the elbow 124. On the other hand,
nipple 126 communicates with the bottom and the side openings that
comprise the precooling passageways 68.
The rearmost region of the precooling passage is shown at the lower
left in FIG. 6. The cross-sectional view in that figure is taken on
the vertical, longitudinal midplane of the U-shaped section 36. The
far wall of this structure is double; part of it has been broken
away to make it clear that the upper section of wall 58 extends
throughout the length of the precooling passageway with respect to
the coolant passageway even though the exhaust conduit turns
upwardly and continues through portion 58a of that wall. The inner
wall has been broken away above the webb 58a to show that from that
point on downstream all of the space between the inner and outer
walls is part of the cooling passageway. A dam is formed
transversely across that flow passage on the plane 7--7 of FIG. 6.
The dam is formed by a webb that interconnects the inner and outer
walls except at the upper portion of the space between them. The
edge of the dam visible in FIG. 6 is designated 140. FIG. 7 is a
cross-sectional view taken on line 7--7 which illustrates this
construction. Below the dam the cooling passageway encompasses the
exhaust conduit over most of its area so that additional cooling is
accomplished.
The extent to which that passage is filled with water, and
therefore the extent to which cooling is accomplished in that
portion, depends upon the size of opening 86 and the rate at which
18 forces coolant to flow. The pump 18 is driven at a speed that
varies with engine speed. In a marine engine, engine load is rather
directly related to engine speed and heating is rather directly
related to engine load. As a consequence, if the outlet opening 86
is not unduly large, the amount of water in the final section of
the cooling passage will vary with load and the quantity of heat
that must be removed from the exhaust gases.
Advantageously, the dam is located at the highest point in the
coolant flowpath so that the flowpath must be completely filled
upstream from that point. Removal of the dam from that high point
does not destroy the value of the invention although efficiency
would be lowered somewhat. The dam may have any convenient form.
Thus, it could comprise any kind of structural division of the
coolant passageway into upstream and downstream sections
interconnected at an elevated point.
Although I have shown and described certain specific embodiments of
my invention, I am fully aware that many modifications thereof are
possible. My invention, therefore, is not to be restricted except
insofar as is necessitated by the prior art.
* * * * *