A rotary engine has a substantially trochoidal-shaped housing cavity in which a rotor planetates. A cooling system for the engine directs coolant along a single series path consisting of series connected groups of passages. Coolant enters near the intake port, passes downwardly and axially through the cooler regions of the engine, then passes upwardly and axially through the hotter regions. By first flowing through the coolest regions, coolant pressure is reduced, thus reducing the saturation temperature of the coolant and thereby enhancing the nucleate boiling heat transfer mechanism which predominates in the high heat flux region of the engine during high power level operation

Blum, Edward J.

Gigon, Richard M.

Jones, Charles

NASA Technical Reports Server

United States Patent [19] 
Jones et al. 
[11] Patent Number: 4,531,900 
[45] Date of Patent: Jul. 30, 1985 
[54] ROTARY ENGINE COOLING SYSTEM 
[75] Inventors: Charles Jones, Hillsdale; Richard M. 
Gigon, Oradell; Edward J. Blum, 
Wayne, all of N.J. 
[73] Assignee: John Deere Technologies 
International, Inc., Moline, 111. 
[21] Appl. NO.: 618,099 
[22] Filed: Jun. 7, 1984 
[51] 
[52] 
[58] 
~561 References Cited 
Int. Cl.3 .......................... FOlC 1/22; FOlC 21/06 
U.S. C1. ..................................... 418/61 A; 418/83 
Field of Search ................................ 418/61 A, 83 
U.S. PATENT DOCUMENTS 
3,007,460 11/1961 Bentele et al. ........................ 418/83 
3,261,335 7/1966 Zimmermann ................... 418/61 A 
3,289,647 12/1966 Turner et al. ......................... 418/83 
3,895,889 7/1975 Loyd, Jr. et al. ..................... 418/83 
3,907,468 9/1975 Green et al. .......................... 418/83 
3,295,505 1/1967 Jordan ................................... 418/83 
3,572,984 3/1971 Jones ..................................... 418/83 
FOREIGN PATENT DOCUMENTS 
712523 1/1980 U.S.S.R. ................................ 4181’83 
OTHER PUBLICATIONS 
Norbye, Jan P., The Wankel Engine, 1971, Chapter 6, 
“Housing and Rotor Cooling”. 
Yamamoto, Kenichi, Rotary Engine, 1971, pp. 63-67. 
Primary Examiner-John J. Vrablik 
1571 ABSTRACT 
A rotary engine has a substantially trochoidal-shaped 
housing cavity in which a rotor planetates. A cooling 
system for the engine directs coolant along a single 
series path consisting of series connected groups of 
passages. Coolant enters near the intake port, passes 
downwardly and axially through the cooler regions of 
the engine, then passes upwardly and axially through 
the hotter regions. By first flowing through the coolest 
regions, coolant pressure is reduced, thus reducing the 
saturation temperature of the coolant and thereby en- 
hancing the nucleate boiling heat transfer mechanism 
which predominates in the high heat flux region of the 
engine during high power level operation. 
1 Claim, 9 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=20080005905 2019-08-30T02:59:51+00:00Z
U.S. Patent Jui. 30,1985 Sheet 1 of 6 4,53 1,900 
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FIG. I 
U.S. Patent Jui. 30,1985 Sheet 2 of 6 4,53 1,900 
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U.S. Patent Jui. 30,1985 Sheet 3 of 6 4,53 1,900 
F/G.  3 
U.S. Patent Jui. 30,1985 Sheet 4 of 6 4,53 1,900 
FIG. 
U.S. Patent Jui. 30,1985 Sheet 5 of 6 4,53 1,900 
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FIG. 6 
FIG. 5 
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US. Patent Jui. 30,1985 Sheet 6 of 6 4,53 1,900 
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around the periphery of the trochoidal-shaped cavity. 
Coolant enters in the coolest area of the housing in the 
vicinity of the inlet port. Divider ribs in the end hous- 
ings direct the coolant flow so that it flows in series 
through the cooler engine regions, then through the 
hottest or top-dead-center (TDC) region of the engine. 
The highest flow velocity is maintained in the T D C  
region. By flowing first through the cool regions, the 
coolant pressure drops and lowers the coolant satura- 
This invention relates to a rotary internal combustion lo tion temperature and enhances the nucleate boiling heat 
transfer mechanism which operates in the TDC region 
downstream of the cooler regions. 
BRIEF DESCRIPTION O F  T H E  DRAWINGS 
FIGS. 1 , 2  and 3 are end views of the housing sections 
of a single rotor internal combustion engine having a 
cooling system according to the present invention. 
FIG. 4 is an enlarged sectional view of the topdead- 
center (TDC) portion of the rotor housing taken in the 
FIG. 5 is a sectional along lines 5-5 of FIG. 4. 
FIG. 6 is a sectional view along lines 6-6 of FIG. 4. 
FIGS. 7, 8 and 9 are sectional views along lines 7-7, 
ROTARY ENGINE COOLING SYSTEM 
BACKGROUND O F  T H E  INVENTION 
The invention described herein was made in the per- 
formance of law under NASA Contract NO, NAS 
3-23056 and is subject to the provisions of Section 305 
of the National Aeronautics and Space Act of 1958 (72 
Stat. 435; 42 U.S.C. 2457). 
engine and, in particular, to a cooling system for such an 
engine of the Wankel type. 
In liquid cooling systems for the housing assembly of 
rotary internal combustion engines of the Wankel type, 
such as disclosed in the U S .  Pat. No. 2,988,065 to Wan- l 5  
kel et al., it is common practice to provide cooling flow 
passages in the housing, which passages extend substan- 
tially parallel to the axis of the engine mainshaft. Also 
commonly Provided are header chambers in the horn- 
ing end walk constructed and arranged to provide end- 20 plane of the spark plug and injector bores. 
to-end interconnection of the passages and thereby pro- 
vide flow of coolant through those Passages. These 
conventional cooling systems are exemplified in the 
U.S. Pat. Nos. to  Loyd, Jr. et ai., 3,895,889; Turner et 
al., 3,289,647; Jones, 3,572,984 and Bentele et al., 25 
3,007,460. In these conventional cooling systems, the 
primary heat transfer mechanism is convection. In the The rotary engine housing includes an anti-drive end 
systems of Turner et al., Bent& et al. and Jones, the housing section 14 
through the hotter regions of the housing, then flowing 30 are aligned by dowels (not shown) which extend 
together by tie-bolts (not shown) which extend through regions. In Loyd, Jr. et al., for each rotor, the flow is 
directs coolant from the coolant inlet through the 
cooler portion of the housing. The other flow path 35 sections’ 
directs coolant from the inlet through the hotter portion 
8-8 and 9-9, respectively,  of^^^, 3, 
DETAILED DESCRIPTION 
( A ~ ~ )  housing 12, a trochoid 
flows through a series flow path, first flowing and a drive end (DE) housing section 16. These sections 
through the regions downstream Of the hotter through aligned bores 18, 20 and 22, and are secured 
between two separate paths’ One path aligned openings (not shown) in each of the housing 
In the assembled condition, the housing has a substan- 
of the housing. In both of these types of known systems, 
heat transfer by convection is promoted by having the 
coolant pass through the hotter housing regions without 
tially trochoidal-shaped cavity 24 surrounded by an 
inner wall 25 within which a rotor (not shown) is SUP- 
Ported for planetation on a mainshaft (not shown), the 
having a decreased pressure due to first having passed 40 mainshaft extending through the opening 26 in end wall 
through the cooler engine regions. H ~ ~ ~ ~ ~ ~ ,  in higher sections 16 and 14. The housing section 12 is provided 
output engines, the heat fluxes can be considerably with an exhaust Port 28 and an spark Plug bore 30. The 
beyond the levels that can be adequately cooled by housing 14 has an air intake Port 34. The intake Port 34 
convective cooling. ln such engines, the predominant functions to pass air into the combustion chambers (not 
cooling mechanism changes to one of nucleate boiling 45 shown) which are d&ned by the rotor (not shown) and 
in the high heat flux regions ofthe engine, Accordingly, disposed in the cavity 24. It is within the purview of this 
it would be desirable to provide a cooling system which invention that any suitable means may be employed to 
enhances this nucleate boiling cooling mechanism. provide a combustible mixture in the combustion cham- 
bers. As best seen in FIGS. 1 and 3, the direction of 
SUMMARY OF THE INVENTION 50 coolant flow, indicated by the arrows, is generally op- 
An object of the present invention is to provide a posite to the direction of rotation Of the rotor (not 
cooling system for a high output rotary engine wherein shown) indicated by arrow R. 
the nucleate boiling cooling mechanism is enhanced. These housing sections, in their normal operative 
Another object of the present invention is to provide position, are oriented such that the major axis of the 
such a cooling system in which coolant flow is upwards 55 trochoidal cavity 24 is vertical. Also, the relative posi- 
through the hotter engine portions to provide efficient tions of exhaust port 28, intake port 34 and spark Plug 
removal of bubbles and vapor. bore 30 are such that combustion produces a heat flux 
Another object of the present invention is to provide distribution wherein the area of highest heat flux ex- 
a rotary engine cooling system in which the coolant tends along the side of the housing 10 in which the spark 
inlet and the coolant outlet are located at the top of the 60 plug (not shown) is located. This area between bores 18 
engine and in which coolant flows through the cooler and 20 is known as the top-dead-center (TDC) region. 
engine portions before it flows through the hottest en- This heat flux phenomenon is well known and is further 
gine portions. described in U S .  Pat. No. 3,895,889. 
These and’ other objects are achieved by the present The present cooling system includes a coolant inlet 36 
invention which includes a rotary engine housing con- 65 and a coolant outlet 38 located in the upper part of the 
sisting of a rotor housing section situated between two A D E  housing section 12. The coolant inlet 36 is near 
end housing sections. A plurality of coolant flow pas- the intake port 34. The coolant outlet 38 is adjacent inlet 
sages extend axially through the housing sections 36 and is positioned in the compression region between 
4,531,900 
3 
the intake 34 and the T D C  region of the housing. The 
end portion of A D E  housing section 12 is not shown so 
that webs 40, 42 and 44, which define chambers 46, 48 
and 50 therebetween, can be more clearly seen. DE 
housing section 16 has webs 52 and 54 which define 5 
chambers 56 and 58 therebetween. These chambers are, 
of course, also enclosed by front and rear end portions 
(not shown) of housing sections 14 and 16, the front end 
portion of A D E  section 12 being removed for clarity, 
while the rear end portion of DE section 16 is not visi- 10 
ble. Coolant flows from inlet 36 into chamber 46 and 
then from chamber 46 through the cool portion of the 
housing sections via axially extending passage groups 
60, 62 and 64 in housing sections 12, 14 and 16, respec- 
tively, into chamber 56 of DE housing section 16. The 15 
coolant flows through chamber 56 and then back 
through a hotter portion of the housing 10 via axial 
passage groups 66, 68 and 70 into chamber 48 of A D E  
housing section 12. The coolant flows through chamber 
48 and then through the relativelv hot TDC uortion of 20 
Y 
the housing via axially extending passage groups 72, 74 
and 76 and into chamber 58 of DE housing section 16. 
Finally, the coolant flows through chamber 58 and back 
through the remaining relatively hot portion of the 
housing 10 via axial passage groups 78, 80 and 82, into 
chamber 50 of A D E  housing section 12, and out of 
coolant outlet 38. Thus, these series-connected circum- 
ferentially-spaced of axially extending housing passages 
form a single series flow path with multiple axial flow 
portions. Note that before any coolant can reach the 
hottest T D C  portion of the housing, it must first flow 
through the coolest housing portions via chamber 46, 
passages 60, 62 and 64 and chamber 56. Note also that 
the direction of coolant flow through the cooler hous- 
ing portions is generally downward in chambers 46 and 
58. Finally, note that the direction of coolant flow 
through the hotter housing portions is generally up- 
ward in chambers 48, 50 and 58. This upward flow in 
the hot region facilitates bubble and vapor removal. 
As best seen in FIG. 3, the DE housing 16 includes 
ribs 57 and 59 which project generally towards each 
other in chamber 56, thereby restricting the generally 
downward flow of coolant in chamber 56. This restric- 
tion between ribs 57 and 59 operates to assure that sub- 
stantially equal volumes of coolant flow through the 
axially extending coolant passage groups 60, 62 and 64 
on either side of the restriction between ribs 57 and 59, 
and thus, assures that there will be sufficient coolant 
flow through the housings in the vicinity of exhaust 
port 28. 
Turning to FIGS. 4,5,  and 6, the TDC portion of the 
rotor housing 14 includes a bore 90 for receiving a 
conventional main fuel injector (not shown), the bore 30 
for a conventional spark plug (not shown), and a bore 
94 for receiving a conventional pilot fuel injector (not 
shown). As best seen in FIGS. 5 and 6, between ribs 108 
and 110, there are seven (7) coolant passages 101-107, 
entering the A D E  side 13 of TDC portion and exiting 
on the DE side 15 of the T D C  portion of rotor housing 
14. As best seen in FIGS. 4-6, passages 102 and 103, to 
avoid bores 30 and 94, extend or bend away from inner 
rotor surface 25 as they move into the interior of rotor 
housing 14 where they merge into cavity 112 (FIG. 4). 
From cavity 112, they diverge and split up again into 
separate passages 102 and 103 as they exit from the DE 
15 side of rotor housing 14. 
Also, as best seen in FIGS. 4-6, passage 105 passes 
substantially straight through, but passage 104 bends to 
25 
30 
35 
40 
45 
50 
55 
4 
avoid bore 30 and merges with passage 105 in the inte- 
rior of the TDC portion at 114 (FIG. 5). Passages 104 
and 105 then again split apart as they exit the DE side 15 
of rotor housing 14. Similarly, passages 106 and 107 
enter the A D E  side 13 separately. Then, both passages 
106 and 107 bend to avoid bore 90 and merge together 
at 116 (FIG. 5), in the interior of the T D C  portion of 
rotor housing 14, then again separate as they exit the 
DE side 15 of the rotor housing 14. This group of seven 
passages 101-107 register with corresponding passage 
groups 72 and 76 in the A D E  and DE housings 12 and 
16, respectively. 
It should be noted that the highest heat fluxes are 
generated near the rotor housing 14 in its TDC portion 
near bores 30 and 94. However, it is this region through 
which extend the relatively tortuous passages 102, 103, 
104 and 106, while passages 101,105 and 107 pass nearly 
straight through rotor housing 14 in areas of relatively 
lower heat flux. If not otherwise compensated for, this 
situation could result in lower coolant flow rates just in 
the areas where lower flow rates are not desirable. 
Accordingly, the present cooling system includes re- 
strictions in passages 101, 105 and 107. This feature of 
the present cooling system can best be understood with 
reference to FIGS. 3 and 7-9. 
Turning to FIGS. 3, 7-9, the DE housing 16 has a 
side 17 for sealingly engaging the DE side 15 of rotor 
housing 14. Taking into account FIGS. 3 , 5  and 7, it can 
be seen that passages 101, 105 and 107 register with 
passages 701 and 805 and 907, respectively, in DE hous- 
ing 16. The cross sectional area of passages 701,805 and 
907 is smaller than that of their corresponding passages 
101, 105 and 107. This, in effect, creates restrictions at 
the downstream ends of passages 101, 105 and 107. 
Preferably, the amount of restriction is adjusted so that 
the coolant flow rates are substantially equal in all seven 
TDC region passages 101-107. This same principle 
could also be used to bias the flow to match differences 
in heat flux between passages, if there is any variation 
between passages. A suggested degree of restriction is 
to make the cross-sectional area of each of passages 701, 
805 and 907 be 56% of the cross-sectional area of pas- 
sages 101, 105 and 107, respectively. This assures ade- 
quate coolant flow velocities in the high heat flux re- 
gions of the TDC portion of rotor housing 14. Alterna- 
tively, restrictions could be placed at the upstream side 
of passages 101, 105 and 107, to achieve the same effect. 
This slightly lowers the pressure in the more critical 
rotor housing passages and further enhances nucleate 
boiling. 
For  example, in an engine with a 40 cu. in. rotor and 
with a total coolant flow of 32 gallons per minute, this 
cooling system achieves a maximum coolant tempera- 
ture rise of slightly above 10 degrees. The system also 
produces coolant flow velocities of 5 ft/sec in the area 
of inlet 34, in the compression area between inlet 34 and 
the T D C  portion, and in the region just prior to exhaust 
port 28. The coolant flow velocity is 9 ft/sec in the 
region of initial gas expansion and 10 ft/sec in the T D C  
60 region between bores-18 and 20. At low power levels, 
the cooling mechanism is entirely convective, but at 
high power levels, the cooling mechanism becomes 
dominated by nucleate boiling in the high heat flux 
(TDC) region of the engine housings. 
An important feature of the present invention, once 
nucleate boiling dominates over convective cooling in 
the high heat flux region, is that the critical metal tem- 
peratures in the high heat flux (TDC) region are a func- 
65  
433  1,900 
5 6 
coolant flow velocity. Although the flow velocity does 
not directly influence the cooled metal temperatures 15 
when the heat transfer means is primarily nucleate boil- 
ing, the efficient removal of vapor does help the engine 
to operate well below engine “burn-out’’ temperature. 
While the invention has been described in conjunc- 
tion with a specific size and embodiment, it is to be 20 
understood that many alternatives, modifications, and 
variations will be apparent to those skilled in the art in 
light of the aforegoing description. Accordingly, this 
invention is intended to embrace all such alternatives, 
modifications and variations which fall within the spirit 25 
and scope of the appended claims. 
We claim: 
tion of the heat flux and of the coolant saturation tem- 1. In a rotary combustion engine with a rotor rotat- 
perature. In this region, the metal temperatures can be able within a trochoidal cavity in a housing having an 
reduced by keeping the saturation temperature (essen- intake port region, an exhaust port region, an expansion 
tially the boiling point) of the coolant as low as possible. region, a compression region, a top-dead-center region, 
This is done by keeping the coolant pressure as low as 5 and a liquid cooling circuit formed by series-connected 
possible, The present invention accomplishes this by circumferentially-spaced sets of axially extending hous- 
passing the coolant through the pressure drop of the ing passzges forming a multi-pass series flow path, the 
cool housing portions first, thus reducing pressure of improvement wherein the cooling circuit comprises: 
the coolant and lowering its saturation temperature a coolant inlet for receiving coolant in the vicinity of 
before it reaches the high heat flux TDC region. 
In addition, in the present invention, the bubble and a coolant outlet positioned in the compression region between the inlet and the top-dead-center region; vanor wash direction is in the same direction as the and 
passage means in the housing for directing coolant 
flow axially and generally in a direction opposite to 
the direction of rotor rotation from the coolant 
inlet to the coolant outlet, said passage means hav- 
ing a top-dead-center portion downstream of other 
portions in the intake port, exhaust port and expan- 
sion regions of the housing, coolant flowing in the 
top-dead-center portion having a pressure which is 
reduced by said coolant having first flowed 
through the said other portions, said reduced cool- 
ant pressure lowering a saturation temperature of 
the coolant and enhancing cooling by nucleate 
boiling in the top-dead-center portion. 
lo  the intake port; 
* * * * *  
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35 
40 
45 
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Rotary engine cooling system

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