COMBUSTION ENGINE HEAT REMOVAL AND TEMPERATURE CONTROL
United States Patent 3838668
A casing extends about an internal combustion engine cylinder to define an evaporator region containing a liquid subject to evaporation during engine heat transfer thereto; a heat exchanger structure receives vapor from the evaporator region for condensation and return to the latter; and an expansion chamber offset from the casing is in closed communication with the evaporator region via the heat exchanger structure, the chamber containing a non-condensable gas for the purpose of temperature control.
US Patent References:
/1226180.html
Bouton, Jr. - May 1917 - 1226180
Cooling system for internal-combustion engines
Armstrong - October 1922 - 1432518
Cooling system for internal-combustion engines
Eells - September 1948 - 2449110
Two-stage cooling system for heat machine components
Beurtweret - July 1968 - 3390667
VAPOR AND DROPLET SEPARATOR FOR EBULLIENT-COOLED ENGINES
Parsons - June 1969 - 3448729
/1226180.html
Bouton, Jr. - May 1917 - 1226180
Cooling system for internal-combustion engines
Armstrong - October 1922 - 1432518
Cooling system for internal-combustion engines
Eells - September 1948 - 2449110
Two-stage cooling system for heat machine components
Beurtweret - July 1968 - 3390667
VAPOR AND DROPLET SEPARATOR FOR EBULLIENT-COOLED ENGINES
Parsons - June 1969 - 3448729
Inventors:
Hays, Lance G. (La Crescenta, CA)
Torola Jr., John (Whittier, CA)
Torola Jr., John (Whittier, CA)
Application Number:
05/317947
Publication Date:
10/01/1974
Filing Date:
12/26/1972
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
123/41.260, 418/90, 165/51, 165/104.260
International Classes:
F01P9/02; F02B61/02; F02B75/02; F01P9/00; F02B61/00; F01P9/02
Field of Search:
123/41.2,41.21,41.26 165/105 418/90
US Patent References:
Primary Examiner:
Antonakas, Manuel A.
Assistant Examiner:
O'connor, Daniel J.
Attorney, Agent or Firm:
Haefliger, William W.
Claims:
We claim
1. In combination with an internal combustion engine combustion cylinder wherein heat is developed, the cylinder having a wall and a head,
2. The combination of claim 1 including ducting intercommunicating said chamber, said heat exchanger structure and said casing, and capillary means within said ducting to conduct said return flow.
3. The combination of claim 2 wherein said capillary structure comprises a mesh screen carried by the duct, and located therein.
4. The combination of claim 2 wherein said capillary structure is carried to extend along the duct boundary and from a point above the level of the cylinder to said evaporator region.
5. The combination of claim 8 including metallic mesh carried to extend adjacent the cylinder and proximate the top of the cylinder, within said region.
6. The combination of claim 2 wherein said ducting includes a horizontal section, and a vertical section extending to said expansion chamber and carrying integral cooling fins, the expansion chamber located above the level of all said fins, the volume of the expansion chamber substantially exceeding that of the heat exchanger interior passage means.
7. The combination of claim 1 including a motor vehicle powered by said engine.
8. The combination of claim 1 wherein said casing extends about the cylinder and over the head end thereof, the casing maximum outer diameter being less than 50% greater than the cylinder maximum diameter.
9. The combination of claim 1 wherein the engine is of two-stroke cycle type, the cylinder having a side wall with staggered fuel intake and exhaust ports traversed by the engine piston during engine operation, said casing extending proximate the exhaust port.
10. The combination of claim 1 wherein the engine is of rotary piston type.
1. In combination with an internal combustion engine combustion cylinder wherein heat is developed, the cylinder having a wall and a head,
2. The combination of claim 1 including ducting intercommunicating said chamber, said heat exchanger structure and said casing, and capillary means within said ducting to conduct said return flow.
3. The combination of claim 2 wherein said capillary structure comprises a mesh screen carried by the duct, and located therein.
4. The combination of claim 2 wherein said capillary structure is carried to extend along the duct boundary and from a point above the level of the cylinder to said evaporator region.
5. The combination of claim 8 including metallic mesh carried to extend adjacent the cylinder and proximate the top of the cylinder, within said region.
6. The combination of claim 2 wherein said ducting includes a horizontal section, and a vertical section extending to said expansion chamber and carrying integral cooling fins, the expansion chamber located above the level of all said fins, the volume of the expansion chamber substantially exceeding that of the heat exchanger interior passage means.
7. The combination of claim 1 including a motor vehicle powered by said engine.
8. The combination of claim 1 wherein said casing extends about the cylinder and over the head end thereof, the casing maximum outer diameter being less than 50% greater than the cylinder maximum diameter.
9. The combination of claim 1 wherein the engine is of two-stroke cycle type, the cylinder having a side wall with staggered fuel intake and exhaust ports traversed by the engine piston during engine operation, said casing extending proximate the exhaust port.
10. The combination of claim 1 wherein the engine is of rotary piston type.
Description:
BACKGROUND OF THE INVENTION
This invention relates generally to the cooling of internal combustion engines. More specifically, it concerns the use of both liquid and gas for cooling engines, in a manner to provide a number of advantages.
There is a continual need to improve the cooling efficiency of engines. Objectives in this area include the production of nearly uniform temperatures on all engine surfaces associated with or proximate to the combustion zone; the maintenance of such temperature uniformity despite widely varying ambient conditions and engine power outputs; the provision of a cooling system which operates independently of acceleration or gravity forces if desired in producing uniform temperatures on engine surfaces at different heights or locations; and the provision of a cooling system which is hermetically sealed, simple to construct and maintain, and which has no moving parts. Insofar as we are aware, no prior cooling system meets all of the above objectives, and in the unusually advantageous manner as now afforded by the present invention.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide a highly efficient internal combustion engine cooling system satisfying the above objectives. Basically, the invention is embodied in the combination, with an internal combustion engine combustion cylinder or cylinders, of a casing extending in proximity to the cylinder and defining with the latter an evaporator region adjacent a wall of the casing, the evaporator region containing a liquid subject to evaporation in response to heat transfer via the wall during engine operation; a passageway for vapor transport to a heat exchanger structure and condensate return to the evaporator region; a heat exchange surface wherein the heat of vaporization is rejected to air or another cooling fluid, causing the vapor to condense; and, an expansion chamber offset from the casing and in closed communication with the evaporator region via the heat exchanger structure, the chamber containing a non-condensable gas and normally not receiving vapor. This boiling and condensing action transfers a great deal of heat and establishes a heat balance with the heat input from the engine. The non-condensable gas volume in the expansion chamber expands or contracts as the engine temperature and hence vapor pressure tends to decrease or increase. The change in gas volume changes the amount of the heat exchanger passage available for heat transfer to maintain the engine surface temperature uniformity as referred to above.
Additional objects include the provision for return of the condensate to the heated surface at the engine either by capillary forces or by gravity; the provision of fine mesh screen or other means defining capillary passages carried by the engine cylinder and/or by the referenced passageway to provide capillary structure inducing the return flow of condensate; the adaptation of the invention to the cooling of a motorcycle engine in such manner that the overall size of the engine structure beneath the operator may be substantially reduced; the location of the heat exchanger surface proximate the fuel tank or other portions of the motorcycle structure, in unusually advantageous manner; and the substantial reduction in sizing of the overall engine cylinder structure and associated cooling surfaces.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which:
DRAWING DESCRIPTION
FIG. 1 is a vertical section showing one preferred form of the invention;
FIG. 2 is a perspective showing of a vehicle, as for example a motorcycle, to which the invention is applied;
FIG. 3 is a view like FIG. 2 showing another adaptation to a motorcycle;
FIG. 4 is a view like FIG. 2 showing a modified adaptation to a motorcycle;
FIG. 5 is a graph of wall temperature at different locations, during engine operation, and cooling; and
FIG. 6 is another graph.
DETAILED DESCRIPTION
In FIG. 1, an internal combustion engine 10 includes a metallic cylinder 11 and a piston 16 reciprocable therein, forming a combustion zone 12. A spark plug in the cylinder head 11a is indicated at 13, and suitable connecting rod and crankshaft components at 14 and 15. The cylinder and head may be two or more separate parts. The illustrated engine is of two-stroke cycle design, characterized in that the cylinder has a side wall with staggered ports 16a and 17. The former admits a combustible fuel-air mixture, to the combustion chamber on the piston up-stroke, and port 17 releases exhaust gas to the exterior on the piston down stroke. The transfer ports are not shown.
The usual extensive cooling fins associated with the cylinder are eliminated, and a cooling system in accordance with the invention is provided. As illustrated, a casing or jacket, as for example that shown at 18, extends in proximity to the cylinder and an evaporator region 19 is provided between the casing and cylinder. Most desirably, the casing surrounds the cylinder and extends thereover; for maximum heat transfer to the cylindrical evaporator region 19a formed between the casing side wall 18b and cylinder side wall 11b, and to the upper evaporator region 19b formed between the casing top 18a and cylinder head 11a. Note that the hot exhaust fitting or duct 20 forming port 17 bridges the cylindrical evaporator region. The lowermost extent of the cylindrical evaporator region 19a extending below duct 20 (which may enclose part or all of the crank case for cooling thereof) contains liquid 21 subject to evaporation as a result of heat transfer as described, during operation of the engine.
Further, an expansion chamber is provided at 22 and a heat exchanger at 23a which may be either in relatively remotely spaced relation from the casing or closely coupled to the casing and in closed communication with the evaporator region, as for example via a duct or ducting 23. The expansion chamber contains a non-condensable gas 24 (gas which does not condense over all operating conditions of the engine).
The vapor produced by evaporation in zone 19 flows through passage 23 to the heat exchanger 23a. The heat exchanger may comprise a single tube with fins 26, on the cooling fluid side, or it may consist of many tubes with multiple fins connected to the passage 23, or it may comprise other suitable fluid to fluid heat exchanger geometry. The heat of condensation is removed from the vapor by the cooling fluid (such as circulating air) causing the vapor to condense on the inner walls. The liquid condensate on such walls flows back to the evaporator section 19, under the influence of gravity or capillary forces produced by capillary structure to be described. The fraction of the heat exchanger passage available to heat transfer is determined by the volume of the "uncooled" chamber 22, the initial pressure of the gas filling the system, the volume of the heat exchanger passages 23a and the volume of gas initially in the system. A relationship which gives the approximate cylinder temperature is
T c = T a + Q i /h A 1 (1 + V 2 /V 1 - V g /V 1 )
where,
T c = outside cylinder wall temperature
T a = ambient temperature
Q i = heat input from engine
h = external heat transfer coefficient
A 1 = total heat exchanger heat transfer area
V 1 = volume of heat exchanger passages
V 2 = volume of uncooled chamber 22
V g = volume of non-condensable gas 24
The results of using this equation to calculate the temperature change of a typical motorcycle cylinder is shown in FIG. 6 for V 2 /V 1 = 5. An increase in Q i by a factor of ten results in an increase of cylinder wall temperature of only 8°C at a velocity of 110 km/hr. Also, as can be seen, the temperature is very insensitive to changes in velocity or ambient temperature. The reason is that the V g /V 1 term in the above equation is very nearly equal to the V 2 /V 1 term and it changes with changes in pressure.
Capillary means may, with unusual advantage, be provided within the ducting to conduct and otherwise aid such condensate return flow. One suitable type of capillary structure is fine mesh metallic screen 28 spot welded to the metal surfaces or otherwise self supported. Another consists of screen installed over wires which provide a greater interstitial liquid flow area. Still another consists of small passages in the wall covered with screen. Capillary forces act in aid of gravity in returning condensate to the evaporator region, the condensate flowing close to the walls of the duct so as to be shielded from the drag forces associated with vapor flow in the duct toward chamber 22. Note that the capillary structure may likewise be applied or built in directly to the cylinder and/or head as at 28a to cause liquid flow against gravity from the bottom of the casing 18 to the sides and top of the cylinde and in the case of other engine types to any part of the engine.
In operation, when heat from the engine causes the liquid to reach the saturation temperature corresponding to the ambient pressure (the pressure of the gas initially in the vapor space within casing 18), the liquid vaporizes, removing heat. Further increases in temperature cause the liquid temperature and vapor pressure to increase, compressing the gas and increasing the volume of vapor contacting the cooled surface 23a. The choice of volume of uncooled chamber 22, cooling surface area (fins 26, for example) and liquid inventory 21 determine the temperature of the cylinder and head surfaces, which is thereby controlled to within a very narrow range regardless of changes in heat load, ambient temperature or velocity, as in FIG. 6 (which shows sleeve wall temperature vs. heat rejection rate for varying velocity at 21°C ambient temperature for 250 CC motorcycle.) A typical temperature vs. distance curve appears in FIG. 5, showing substantial uniformity of wall temperature at the cylinder 18 and along duct 23, toward chamber 22.
Referring back to FIG. 1, the broken outline 40 indicates the usual engine fin structure extent, illustrating the dramatic reduction in cylinder and head dimensions achieved by the invention.
FIG. 2 indicates an application of the invention to a multicylinder motorcycle 41, the engine cylinder casing being shown at 18c, and corresponding to casing 18 in FIG. 1, but enclosing three cylinders instead of one. Elimination of engine fins creates vertical space at 42, enabling the fuel tank 43 to have greater depth, increasing fuel capacity and lowering the motorcycle center of gravity. The air heat exchanger structure 26a (corresponding to fins 26 in FIG. 1) is located for example forward of the casing 18c, as is the expansion chamber 22a. FIG. 3 shows another application of the invention to a single cylinder motorcycle 50. The casing 18d surrounding the cylinder and head is connected via duct 23b with heat exchanger structure 22c of which expansion chamber 22b is a part. That structure may be part of the fuel tank structure 53, and at the front thereof, behind the upper extent of front fender 58. Ducting 23b (corresponding to duct 23 in FIG. 1) may be flexible. This location of the heat exchanger structure, behind the upper extent of the front wheel fender 58, ensures isolation from mud and dirt thrown by the front wheel, preventing fouling.
Finally, FIG. 4 shows application of the invention to a rotary piston engine, as for example of Wankel design. A casing 80 extends about a cylinder 81 but is spaced therefrom to form an evaporator region 82 corresponding to region 19 described above. The lowermost extent 82a of that region contains liquid 84 subject to evaporation during engine operation. An expansion chamber, not shown is in communication with the upper extent 82b of the evaporator region as via a duct 83. Capillary structure, as for example mesh, is indicated at 86-88 lining the duct 83 and extending over the walls of the casing and cylinder, as shown. A generally triangular rotor 91 rotates in the cylinder and in relation to a combustible mixture inlet port 89 and an exhaust port 90.
Typical liquids 21 and 84 include water or Dow-Therm A, and typical non-condensable gases as at 24 include air, nitrogen and Argon.
This invention relates generally to the cooling of internal combustion engines. More specifically, it concerns the use of both liquid and gas for cooling engines, in a manner to provide a number of advantages.
There is a continual need to improve the cooling efficiency of engines. Objectives in this area include the production of nearly uniform temperatures on all engine surfaces associated with or proximate to the combustion zone; the maintenance of such temperature uniformity despite widely varying ambient conditions and engine power outputs; the provision of a cooling system which operates independently of acceleration or gravity forces if desired in producing uniform temperatures on engine surfaces at different heights or locations; and the provision of a cooling system which is hermetically sealed, simple to construct and maintain, and which has no moving parts. Insofar as we are aware, no prior cooling system meets all of the above objectives, and in the unusually advantageous manner as now afforded by the present invention.
SUMMARY OF THE INVENTION
It is a major object of the invention to provide a highly efficient internal combustion engine cooling system satisfying the above objectives. Basically, the invention is embodied in the combination, with an internal combustion engine combustion cylinder or cylinders, of a casing extending in proximity to the cylinder and defining with the latter an evaporator region adjacent a wall of the casing, the evaporator region containing a liquid subject to evaporation in response to heat transfer via the wall during engine operation; a passageway for vapor transport to a heat exchanger structure and condensate return to the evaporator region; a heat exchange surface wherein the heat of vaporization is rejected to air or another cooling fluid, causing the vapor to condense; and, an expansion chamber offset from the casing and in closed communication with the evaporator region via the heat exchanger structure, the chamber containing a non-condensable gas and normally not receiving vapor. This boiling and condensing action transfers a great deal of heat and establishes a heat balance with the heat input from the engine. The non-condensable gas volume in the expansion chamber expands or contracts as the engine temperature and hence vapor pressure tends to decrease or increase. The change in gas volume changes the amount of the heat exchanger passage available for heat transfer to maintain the engine surface temperature uniformity as referred to above.
Additional objects include the provision for return of the condensate to the heated surface at the engine either by capillary forces or by gravity; the provision of fine mesh screen or other means defining capillary passages carried by the engine cylinder and/or by the referenced passageway to provide capillary structure inducing the return flow of condensate; the adaptation of the invention to the cooling of a motorcycle engine in such manner that the overall size of the engine structure beneath the operator may be substantially reduced; the location of the heat exchanger surface proximate the fuel tank or other portions of the motorcycle structure, in unusually advantageous manner; and the substantial reduction in sizing of the overall engine cylinder structure and associated cooling surfaces.
These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which:
DRAWING DESCRIPTION
FIG. 1 is a vertical section showing one preferred form of the invention;
FIG. 2 is a perspective showing of a vehicle, as for example a motorcycle, to which the invention is applied;
FIG. 3 is a view like FIG. 2 showing another adaptation to a motorcycle;
FIG. 4 is a view like FIG. 2 showing a modified adaptation to a motorcycle;
FIG. 5 is a graph of wall temperature at different locations, during engine operation, and cooling; and
FIG. 6 is another graph.
DETAILED DESCRIPTION
In FIG. 1, an internal combustion engine 10 includes a metallic cylinder 11 and a piston 16 reciprocable therein, forming a combustion zone 12. A spark plug in the cylinder head 11a is indicated at 13, and suitable connecting rod and crankshaft components at 14 and 15. The cylinder and head may be two or more separate parts. The illustrated engine is of two-stroke cycle design, characterized in that the cylinder has a side wall with staggered ports 16a and 17. The former admits a combustible fuel-air mixture, to the combustion chamber on the piston up-stroke, and port 17 releases exhaust gas to the exterior on the piston down stroke. The transfer ports are not shown.
The usual extensive cooling fins associated with the cylinder are eliminated, and a cooling system in accordance with the invention is provided. As illustrated, a casing or jacket, as for example that shown at 18, extends in proximity to the cylinder and an evaporator region 19 is provided between the casing and cylinder. Most desirably, the casing surrounds the cylinder and extends thereover; for maximum heat transfer to the cylindrical evaporator region 19a formed between the casing side wall 18b and cylinder side wall 11b, and to the upper evaporator region 19b formed between the casing top 18a and cylinder head 11a. Note that the hot exhaust fitting or duct 20 forming port 17 bridges the cylindrical evaporator region. The lowermost extent of the cylindrical evaporator region 19a extending below duct 20 (which may enclose part or all of the crank case for cooling thereof) contains liquid 21 subject to evaporation as a result of heat transfer as described, during operation of the engine.
Further, an expansion chamber is provided at 22 and a heat exchanger at 23a which may be either in relatively remotely spaced relation from the casing or closely coupled to the casing and in closed communication with the evaporator region, as for example via a duct or ducting 23. The expansion chamber contains a non-condensable gas 24 (gas which does not condense over all operating conditions of the engine).
The vapor produced by evaporation in zone 19 flows through passage 23 to the heat exchanger 23a. The heat exchanger may comprise a single tube with fins 26, on the cooling fluid side, or it may consist of many tubes with multiple fins connected to the passage 23, or it may comprise other suitable fluid to fluid heat exchanger geometry. The heat of condensation is removed from the vapor by the cooling fluid (such as circulating air) causing the vapor to condense on the inner walls. The liquid condensate on such walls flows back to the evaporator section 19, under the influence of gravity or capillary forces produced by capillary structure to be described. The fraction of the heat exchanger passage available to heat transfer is determined by the volume of the "uncooled" chamber 22, the initial pressure of the gas filling the system, the volume of the heat exchanger passages 23a and the volume of gas initially in the system. A relationship which gives the approximate cylinder temperature is
T c = T a + Q i /h A 1 (1 + V 2 /V 1 - V g /V 1 )
where,
T c = outside cylinder wall temperature
T a = ambient temperature
Q i = heat input from engine
h = external heat transfer coefficient
A 1 = total heat exchanger heat transfer area
V 1 = volume of heat exchanger passages
V 2 = volume of uncooled chamber 22
V g = volume of non-condensable gas 24
The results of using this equation to calculate the temperature change of a typical motorcycle cylinder is shown in FIG. 6 for V 2 /V 1 = 5. An increase in Q i by a factor of ten results in an increase of cylinder wall temperature of only 8°C at a velocity of 110 km/hr. Also, as can be seen, the temperature is very insensitive to changes in velocity or ambient temperature. The reason is that the V g /V 1 term in the above equation is very nearly equal to the V 2 /V 1 term and it changes with changes in pressure.
Capillary means may, with unusual advantage, be provided within the ducting to conduct and otherwise aid such condensate return flow. One suitable type of capillary structure is fine mesh metallic screen 28 spot welded to the metal surfaces or otherwise self supported. Another consists of screen installed over wires which provide a greater interstitial liquid flow area. Still another consists of small passages in the wall covered with screen. Capillary forces act in aid of gravity in returning condensate to the evaporator region, the condensate flowing close to the walls of the duct so as to be shielded from the drag forces associated with vapor flow in the duct toward chamber 22. Note that the capillary structure may likewise be applied or built in directly to the cylinder and/or head as at 28a to cause liquid flow against gravity from the bottom of the casing 18 to the sides and top of the cylinde and in the case of other engine types to any part of the engine.
In operation, when heat from the engine causes the liquid to reach the saturation temperature corresponding to the ambient pressure (the pressure of the gas initially in the vapor space within casing 18), the liquid vaporizes, removing heat. Further increases in temperature cause the liquid temperature and vapor pressure to increase, compressing the gas and increasing the volume of vapor contacting the cooled surface 23a. The choice of volume of uncooled chamber 22, cooling surface area (fins 26, for example) and liquid inventory 21 determine the temperature of the cylinder and head surfaces, which is thereby controlled to within a very narrow range regardless of changes in heat load, ambient temperature or velocity, as in FIG. 6 (which shows sleeve wall temperature vs. heat rejection rate for varying velocity at 21°C ambient temperature for 250 CC motorcycle.) A typical temperature vs. distance curve appears in FIG. 5, showing substantial uniformity of wall temperature at the cylinder 18 and along duct 23, toward chamber 22.
Referring back to FIG. 1, the broken outline 40 indicates the usual engine fin structure extent, illustrating the dramatic reduction in cylinder and head dimensions achieved by the invention.
FIG. 2 indicates an application of the invention to a multicylinder motorcycle 41, the engine cylinder casing being shown at 18c, and corresponding to casing 18 in FIG. 1, but enclosing three cylinders instead of one. Elimination of engine fins creates vertical space at 42, enabling the fuel tank 43 to have greater depth, increasing fuel capacity and lowering the motorcycle center of gravity. The air heat exchanger structure 26a (corresponding to fins 26 in FIG. 1) is located for example forward of the casing 18c, as is the expansion chamber 22a. FIG. 3 shows another application of the invention to a single cylinder motorcycle 50. The casing 18d surrounding the cylinder and head is connected via duct 23b with heat exchanger structure 22c of which expansion chamber 22b is a part. That structure may be part of the fuel tank structure 53, and at the front thereof, behind the upper extent of front fender 58. Ducting 23b (corresponding to duct 23 in FIG. 1) may be flexible. This location of the heat exchanger structure, behind the upper extent of the front wheel fender 58, ensures isolation from mud and dirt thrown by the front wheel, preventing fouling.
Finally, FIG. 4 shows application of the invention to a rotary piston engine, as for example of Wankel design. A casing 80 extends about a cylinder 81 but is spaced therefrom to form an evaporator region 82 corresponding to region 19 described above. The lowermost extent 82a of that region contains liquid 84 subject to evaporation during engine operation. An expansion chamber, not shown is in communication with the upper extent 82b of the evaporator region as via a duct 83. Capillary structure, as for example mesh, is indicated at 86-88 lining the duct 83 and extending over the walls of the casing and cylinder, as shown. A generally triangular rotor 91 rotates in the cylinder and in relation to a combustible mixture inlet port 89 and an exhaust port 90.
Typical liquids 21 and 84 include water or Dow-Therm A, and typical non-condensable gases as at 24 include air, nitrogen and Argon.