Internal combustion engine block having a cylinder liner shunt flow cooling system and method of cooling same

An internal combustion engine block having a circumferential channel formed between the cylinder block and a cylinder liner, surrounding and adjacent to the high temperature combustion chamber region of the engine, to which coolant flow is diverted from the main coolant stream to uniformly and effectively cool this critical area of the liner. The high velocity flow of the main coolant stream, as it passes the end of the cylinder liner adjacent the combustion chamber, provides a reduced pressure head at the port interconnecting the outlet end of the circumferential channel with the main coolant stream. Channel entrance holes, located upstream at relatively stagnant regions in the main coolant flow, are at a higher pressure head than the channel exit port, thus inducing flow through the channel at a high velocity flow.

TECHNICAL FIELD 
This invention relates to internal combustion engines and particularly to 
fuel injected diesel cycle engines, and specifically to the construction 
of the cylinder block and cylinder liner to accommodate cooling of the 
liner. 
BACKGROUND OF THE INVENTION 
It is conventional practice to provide the cylinder block of an internal 
combustion engine with numerous cast in place interconnected coolant 
passages within the area of the cylinder bore. This allows maintaining the 
engine block temperature at a predetermined acceptably low range, thereby 
precluding excessive heat distortion of the piston cylinder, and related 
undesirable interference between the piston assembly and the piston 
cylinder. 
In a conventional diesel engine having replaceable cylinder liners of the 
flange type, coolant is not in contact with the immediate top portion of 
the liner, but rather is restricted to contact below the support flange in 
the cylinder block. This support flange is normally, of necessity, of 
substantial thickness. Thus, the most highly heated portion of the 
cylinder liner, namely the area adjacent the combustion chamber, is not 
directly cooled. 
Furthermore, uniform cooling all around the liner is difficult to achieve 
near the top of the liner because location of coolant transfer holes to 
the cylinder head is restricted by other overriding design considerations. 
The number of transfer holes is usually limited, and in many engine 
designs the transfer holes are not uniformly spaced. 
All of the foregoing has been conventional practice in internal combustion 
engines, and particularly with diesel cycle engines, for many, many years. 
However, in recent years there has been a great demand for increasing the 
horsepower output of the engine package and concurrently there exists 
redesign demands to improve emissions by lowering hydrocarbon content. 
Both of these demands result in hotter running engines, which in turn 
creates greater demands on the cooling system. The most critical area of 
the cylinder liner is the top piston ring reversal point, which is the top 
dead center position of the piston, a point at which the piston is at a 
dead stop or zero velocity. In commercial diesel engine operations, it is 
believed that this temperature at the piston reversal point must be 
maintained so as not to exceed 400.degree. F. (200.degree. C.). In meeting 
the demands for more power and fewer hydrocarbon emissions, the fuel 
injection pressure has been increased on the order of 40% (20,000 psi to 
about 28,000 psi) and the engine timing has been retarded. Collectively, 
these operating parameters make it difficult to maintain an acceptable 
piston cylinder liner temperature at the top piston ring reversal point 
with the conventional cooling technique described above. 
SUMMARY OF THE INVENTION 
The present invention overcomes these shortcomings by providing a 
continuous channel all around the liner and located near the top of the 
liner. Between 5 to 10% of the total engine coolant fluid flow can be 
directed through these channels, without the use of special coolant supply 
lines or long internal coolant supply passages. This diverted flow 
provides a uniform high velocity stream, all around and high up on the 
liner, to effectively cool the area of the cylinder liner adjacent to the 
upper piston ring travel, thus tending to better preserve the critical 
lubricating oil film on the liner inside surface. The resulting uniform 
cooling also minimizes the liner bore distortion, leading to longer 
service life. Further, the present invention requires but minor 
modification to incorporate into existing engine designs. 
The present invention includes a circumferential channel formed between the 
cylinder block and cylinder liner, surrounding and adjacent to the high 
temperature combustion chamber region of an internal combustion engine, to 
which coolant flow is diverted from the main coolant stream to uniformly 
and effectively cool this critical area of the liner. Coolant flow through 
the channel is induced by the well known Bernoulli relationship between 
fluid velocity and pressure. The high velocity flow of the main coolant 
stream, through the passages that join the cylinder block with the 
cylinder head, provides a reduced pressure head at intersecting channel 
exit holes. Channel entrance holes, located upstream at relatively 
stagnant regions in the main coolant flow, are at a higher pressure head 
than the channel exit holes, thus inducing flow through the channel. 
These and other objects of the present invention are readily apparent from 
the following detailed description of the best mode for carrying out the 
invention when taken in connection with the accompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Pursuant to one embodiment of the present invention as show in FIGS. 1-3, a 
cylinder block, generally designated 10 includes a plurality of 
successively aligned cylinder bores 12. Each cylinder bore is constructed 
similarly and is adapted to receive a cylindrical cylinder liner 14. 
Cylinder bore 12 includes a main inner radial wall 16 of one diameter and 
an upper wall 18 of greater diameter so as to form a stop shoulder 20 at 
the juncture thereof. 
Cylinder liner 14 includes a radial inner wall surface 22 of uniform 
diameter within which is received a reciprocating piston, having the usual 
piston rings, etc., as shown generally in U.S. Pat. No. 3,865,087, 
assigned to the same assignee as the present invention, the description of 
which is incorporated herein by reference. 
The cylinder liner 14 further includes a radial flange 24 at its extreme 
one end which projects radially outwardly from the remainder of an upper 
engaging portion 26 of lesser diameter than the radial flange so as to 
form a stop shoulder 28. The entirety of the upper engaging portion 26 of 
the cylinder liner is dimensioned so as to be in interference fit to close 
fit engagement (i.e. 0.0005 to 0.0015 inch clearance) with the cylinder 
block, with the cylinder liner being secured in place by the cylinder head 
and head bolt clamp load in conventional manner. 
About the cylinder liner 12, and within the adjacent walls of the cylinder 
block, there is provided a main coolant chamber 30 surrounding the greater 
portion of the cylinder liner. A coolant fluid is adapted to be circulated 
within the main coolant chamber from an inlet port (not shown) and thence 
through one or more outlet ports 32. 
The general outline or boundaries of the main coolant chamber 30 are shown 
in phantom line in FIG. 1 as surrounding the cylinder bore, and include a 
pair or diametrically opposed outlet ports 32. 
Thus far, the above description is of a conventionally designed internal 
combustion engine as shown in the above-referenced U.S. Pat. No. 
3,865,087. 
As further shown in FIGS. 1-3, and in accordance with the present 
invention, a secondary cooling chamber is provided about the uppermost 
region of the cylinder liner within the axial length of the upper engaging 
portion 26. The secondary cooling chamber is provided specifically as a 
circumferentially extending channel 34 machined or otherwise constructed 
within the radially outer wall of the upper engaging portion 26 of the 
cylinder liner and having an axial extent or length beginning at the stop 
shoulder 28 and extending approximately half-way across the upper engaging 
portion 26. 
The secondary cooling chamber includes a pair of fluid coolant passages in 
the form of inlet ports 36 diametrically opposed from one another and each 
communicating with the main coolant chamber 30 
by means of a scalloped recess constructed within the radial inner wall of 
the cylinder block. Each scalloped recess extends in axial length from a 
point opening to the main coolant chamber 30 to a point just within the 
axial extent or length of the channel 34, as seen clearly in FIG. 2, and 
each is disposed approximately 90.degree. from the outlet ports 32. 
The secondary cooling chamber also includes a plurality of outlet ports 38. 
The outlet ports 38 are radial passages located at and communicating with 
a respective one of the outlet ports 32 of the main cooling chamber. The 
diameter of the radially directed passage or secondary cooling chamber 
outlet port 38 is sized relative to that of the main coolant chamber 
outlet port 32 such that it is in effect a venturi. 
While not shown, it is to be appreciated that the top piston ring of the 
piston assembly is adapted to be adjacent the secondary cooling chamber 
when the piston assembly is at its point of zero velocity, i.e., the top 
piston ring reversal point. 
In terms of specific design for an internal cylinder bore diameter of 149.0 
mm, the important relative fluid coolant flow parameters are as follows: 
______________________________________ 
Circumferential channel 34: 
axial length 12.0 mm 
depth 1.0 mm 
Scalloped recess (inlet port 36): 
radial length (depth) 2.0 mm 
cutter diameter for 3.00 inches 
machining scallop 
arc degrees circumscribed 
20.degree. 
on cylinder bore 
chord length on cylinder 
25.9 mm 
bore 
Main cooling chamber outlet port 32: 
diameter 15 mm 
Secondary cooling chamber outlet 
port/venturi/radial passage 38: 
diameter 6 mm 
pressure drop across 0.41 psi 
venturi/output port 38 
coolant flow diverted 7.5% 
through secondary 
cooling chamber 
______________________________________ 
Generally, the above-mentioned specific parameters are selected based upon 
maintaining the flow area equal through the ports 36, 38 (i.e. total inlet 
port flow area and total outlet port flow area) and channel 34. Thus in 
the embodiment of FIGS. 1-3, the flow area through each inlet port 36 and 
outlet port 38 is twice that of the channel 34. 
In operation, as coolant fluid is circulated though the main coolant 
chamber 30, it will exit the main coolant chamber outlet ports 32 at a 
relatively high fluid velocity. For example, within the main coolant 
chamber the fluid velocity, because of its volume relative to the outlet 
ports 32, would be perhaps less than one foot per second. However, at each 
outlet port 32 the fluid velocity may be in the order of seven to eight 
feet per second and would be known as an area of high fluid velocity. But 
for the existence of the secondary cooling chamber, the flow of coolant 
through the main coolant chamber would not be uniform about the entire 
circumference of the cylinder liner. Rather, at various points about the 
circumference, and in particular with respect to the embodiment shown in 
FIGS. 1-3 wherein there is provided two diametrically opposed outlet ports 
32, a region or zone of coolant flow stagnation would form at a point 
approximately 90.degree., or half-way between, each of the outlet ports. 
This would create a hot spot with a potential for undesirable distortion, 
possible loss of lubricating oil film, leading to premature wear and 
blow-by. 
Pursuant to the present invention, coolant fluid from the main coolant 
chamber is caused to be drawn through each secondary cooling chamber inlet 
port 36 as provided by the scalloped recess and thence to be split in 
equal flow paths to each of the respective outlet ports 38, thence through 
the venturi, i.e. the radial passage forming the outlet port 38, and out 
the main cooling chamber outlet ports 32. By reason of the Bernoulli 
relationship between the fluid velocity and pressure, the high velocity 
flow of the main coolant stream through each outlet port 32 provides a 
reduced pressure head at the intersection with the venturi or radial 
passage 38. Thus the coolant within the secondary cooling chamber or 
channel 34 will be at a substantially higher pressure head than that which 
exists within the radial passages 38, thereby inducing flow at a 
relatively high flow rate through the channel 34. In practice, it has been 
found that the fluid velocity through the secondary channel 34 will be, in 
the example given above, at about three, and perhaps as much as six feet 
per second. This, therefore, provides a very efficient means for removing 
a significant portion of the thermal energy per unit area of the cylinder 
liner at the uppermost region of the cylinder liner adjacent the 
combustion chamber. 
As an alternative to the scalloped recess forming inlet port 36 being 
constructed within the inner radial wall of the cylinder bore, the 
cylinder liner may be constructed with a flat chordal area 36 as shown in 
FIG. 3c of the same dimension (i.e. same axial length and circumferential 
or chord length) and within the same relative location of the 
above-described recess. The effect is the same, namely providing a channel 
communicating the coolant flow from the main coolant chamber 30 with that 
of the secondary cooling chamber channel 34. 
In FIG. 4, there is shown an alterative embodiment of the present 
invention, particularly applicable for re-manufactured cylinder blocks, 
whereby the cylinder bore includes a repair bushing 50 press fit within 
the cylinder block 10 and including the same stop shoulder 20 for 
receiving the cylinder liner. Likewise, the repair bushing and cylinder 
liner include a pair of radial passages extending therethrough to provide 
outlet ports 38 and thereby establishing coolant fluid flow between the 
secondary cooling chamber and the main outlet ports 32. Also as seen in 
FIG. 4, the radial extending passage of outlet port 38 is easily machined 
within the cylinder block by drilling in from the boss 52 and thereafter 
plugging the boss with a suitable machining plug 54. 
The foregoing description is of a preferred embodiment of the present 
invention and is not to be read as limiting the invention. The scope of 
the invention should be construed by reference to the following claims.