Abstract:
This is the mechanization of an external combustion hot air engine cycle known as the “Warren Cycle”. The “Warren Cycle” has four parts. They are: 1. cooled compression; 2. stored heat released from a regenerator and heat added to the working fluid at constant volume; 3. heated expansion; and 4. heat stored in a regenerator and heat removed from the working fluid at constant volume. The resulting engine is a thermally regenerated, reciprocating, two stroke external combustion engine that stores the spent heat in regenerator  10  and returns it to the engine cycle to do work. Each unit of the engine has cylinder  12  that is closed at one end by cylinder head  4  and contains working fluid, regenerator  10 , heater  14 , cooler  24 , and power piston  18  that is connected to power output shaft  22 . Cooler  24  is moved through the working fluid as it is being compressed, cooling the working fluid. Regenerator  10  and heater  14  are moved through the working fluid, heating the working fluid, while its volume is kept constant. Heater  14  is moved through the working fluid while it is expanding, heating the working fluid. Regenerator  10  and cooler  24  are moved through the working fluid, cooling the working fluid, while the volume of the working fluid is kept constant.

Description:
BACKGROUND 
     1. Field of Invention 
     The present invention relates to mechanization of the “Warren Cycle”. The “Warren Cycle” is: cooled compression, stored heat released from a regenerator and heat added to the working fluid at constant volume, heated expansion, and heat stored in a regenerator and heat removed from the working fluid at constant volume. The resulting engine is a thermally regenerated, reciprocating, two stroke external combustion engine that stores the spent heat and returns it to the engine cycle to do work. 
     2. Description of Prior Art 
     Thermal regeneration is the capturing of waste heat from a thermodynamic cycle, and the utilization of that energy within the cycle or engine to improve the cycle or engine&#39;s performance. This is commonly done with many heat engines including Stirling engines, gas turbines, and Rankine cycle devices. In the Stirling cycle engine, the fluid is moved about in the engine by a displacer piston or a regenerator acting as a displacer piston. In a gas turbine the exhaust heat coming out of the exhaust is transferred to the fluid leaving the compressor and going into the combustor. This way it is not necessary to add as much heat (fuel) in the combustor to raise the fluid temperature to the desired turbine inlet temperature. This means that the same work is accomplished but less fuel is used. 
     The approach taken by most inventors who attempted to incorporate regeneration into reciprocating external combustion engines was to try to improve existing cycles. In the gas turbine and Brayton cycles, heat is added at constant pressure. This results in a pressure difference across the regenerator that must be sealed. The gas turbines use high speed rotating devices that are costly. The piston type Braton engines need valves in the high temperature working fluid paths. The Stirling cycle engines use a displacer piston or a regenerator that acts as a displacer piston. They also have difficulty getting the heat from the heater into the working fluid and from the working fluid into the cooler. They also have problems timing the heating and cooling with the position of the power piston. 
     The Warren cycle engine is a piston engine. It has no high speed rotating parts. Heat is added at constant volume. There is a slight pressure difference across the regenerator that requires minimum sealing. The Warren cycle engine has no displacer piston, and the regenerator does not act like a displacer piston. In addition, the engine moves the fluid to be heated through the regenerator, heater, or cooler each time the fluid is to be heated or cooled. The Warren cycle engine has perfect timing between the power piston position and when heat is added or removed. Other differences exist between the engines and the regenerated engine disclosed herein. All of these are discussed in greater detail in the section entitled “Detailed Description of the Invention”. 
     SUMMARY 
     This invention is a two stroke, regenerated, external combustion, reciprocating engine made up of a number of similar working units. Each working unit is comprised of a cylinder that is closed at one end by a cylinder head and contains a heater, cooler, regenerator, and a power piston that is connected to a power output means. The regenerator, heater, and cooler can move between the power piston and the cylinder head, and means are provided to accomplish this movement at the appropriate times during the engine&#39;s operating cycle. The regenerator is an alternating flow heat exchanger. The movement of the regenerator, heater, and cooler is such that the cooling stroke (the regenerator is heating) begins when the power piston is at about 85% of the way from the cylinder head, and ends when the power piston is about 15% of the way towards the cylinder head. (This is cooling at constant volume). The compressed fluid heating stroke (the regenerator is giving up heat) begins at about 85% of the power piston&#39;s stroke towards the cylinder head, and ends at about 15% of downward travel of the power piston&#39;s expansion stroke. (This is heating at constant volume). Means are provided for the introduction of heat into the working fluid during the heating and expansion cycles. Means are provided for the removal of heat from the working fluid during the cooling and compression cycles. 
     Objects and Advantages 
     Several objects and advantages of the Warren cycle engine are: 
     (a) The engine compresses the fluid in the same cylinder that the engine expands the fluid in. 
     (b) The engine cools the fluid during compression. 
     (c) The engine saves the heat from the spent fluid and releases the heat to the compressed fluid. 
     (d) The engine has no valves. 
     (e) The engine has no displacer piston 
     (f) The heater supply and exit pipes can be sized so that there is no compression during the heating cycle. 
     (g) The engine can be operated so that the charge is almost fully expanded. 
    
    
     DRAWING FIGURES 
     FIGS. 1-4 are schematic illustrations of the preferred embodiment of a “Warren Cycle Engine”. 
     FIG. 1 shows the engine at the start of the cooling cycle. 
     FIG. 2 shows the engine at the start of the compression cycle 
     FIG. 3 shows the engine at the start of the heating cycle. 
     FIG. 4 shows the engine at the start of the expansion part of the cycle. 
     FIGS. 5-8 are schematic illustrations of the first alternate embodiment of a “Warren Cycle Engine”. 
     FIG. 5 shows the first alternate embodiment of a “Warren Cycle Engine” at the start of the cooling cycle. 
     FIG. 6 shows the first alternate embodiment of a “Warren Cycle Engine” at the start of the compression cycle 
     FIG. 7 shows the first alternate embodiment of a “Warren Cycle Engine” at the start of the heating cycle. 
     FIG. 8 shows the first alternate embodiment of a “Warren Cycle Engine” at the start of the expansion part of the cycle. 
    
    
     REFERENCE NUMERALS IN DRAWINGS 
       4  cylinder head 
       7  shaft 
       10  regenerator 
       12  cylinder 
       14  heater 
       16  heat source 
       18  power piston 
       20  connecting rod 
       22  power output shaft 
       24  cooler 
       25  regenerator actuator 
       26  heater actuator 
       27  cooler actuator 
       28  heater fluid supply pipe 
       30  heater fluid exit pipe 
       32  cooler fluid supply pipe 
       34  cooler fluid exit pipe 
       36  cold source 
     DESCRIPTION 
     FIGS.  1  to  4 —Preferred Embodiment 
     This invention is a two stroke regenerative, reciprocating, external combustion engine employing a regenerator  10 , heater  14 , and cooler  24 . The preferred embodiment of this invention employs two strokes divided into four cycles. The first cycle is the cooling cycle. The second is the compression cycle. The third is the heating cycle. And the fourth is the expansion cycle. The cooling cycle is from about 85% of the downward travel of power piston  18  to about 15% of the travel back up. The compression cycle is from about 15% of the travel back up of power piston  18  to about 85% of the upward travel of power piston  18 . The heating cycle is from about 85% of the upward travel of power piston  18  to about 15% of the downward travel of power piston  18 . The expansion cycle is from about top dead center to about 85% of the downward travel of power piston  18 . The above positions are all estimates and are given for descriptive purposes only. The actual position, at which a part of the cycle may begin or end, may be different from those set out above. (Heater fluid supply and exit pipes can be sized such that no mechanical compression takes place during regenerative heating). The heating and expansion cycles can overlap. 
     The cooling cycle begins with regenerator  10 , and cooler  24  adjacent to cylinder head  4  and ends with regenerator  10 , heater  14 , and cooler  24  adjacent to power piston  18 . During the cooling cycle, regenerator  10 , and cooler  24  move down (towards power piston  18 ) forcing the hot fluid through regenerator  10 , and regenerator  10  absorbs heat from the fluid (cooling the fluid). 
     The compression cycle starts with regenerator  10 , heater  14 , and cooler  24  close to and moving up with power piston  18  and ends with regenerator  10 , and heater  14  moving away from power piston  18 , and cooler  24  adjacent to cylinder head  4 . 
     The heating cycle starts with regenerator  10  and heater  14  moving away from power piston  18 , and ends with regenerator  10 , heater  14 , and cooler  24  adjacent to cylinder head  4 . During the heating cycle regenerator  10  and heater  14  are moved up through the fluid trapped between power piston  18  and cylinder head  4  and transfer heat to this fluid (heating the fluid). Air is the fluid that is expected to be employed in this invention. However, any gas, liquid or mixture of gas and liquid could be used. 
     FIGS. 1-8 Illustrate schematically an external combustion engine suitable for practice of this invention. Only one set of components for such an engine is illustrated; however, what is illustrated will function as a complete engine if it has an inertial load. It will be understood that this is merely representative of one set of components. A plurality of such structures joined together would make up a larger engine. Other portions of the engine are conventional. Thus, the bearings, seals, etc. of the engine are not specifically illustrated. The power output shaft is but one means of power output. The power pistons of two cylinders placed end to end could have a linear electrical generator between them, and the engine operated as a free piston engine. 
     Cylinder  12  is closed at one end by cylinder head  4 . Cylinder  12  further contains power piston  18 , which is connected to power output shaft  22  by a connecting rod  20  (for converting the linear motion of the piston to the rotating motion of the shaft). The expanding gases exert a force on power piston  18 , (a cylindrical piston that can move up and down in cylinder  12 ). That force, exerted on power piston  18  moving it down, is transmitted via connecting rod  20  and power output shaft  22  to a load (not shown). Heater fluid supply pipe  28  transfers hot fluid to heater  14  from heat source  16 , and heater fluid exit pipe  30  transfers spent fluid from heater  14  back to heat source  16 . Cooler fluid supply pipe  32  transfers cold fluid to cooler  24  from cold source  36 , and cooler fluid exit pipe  34  transfers spent fluid from cooler  24  back to cold source  36 . Heater actuator  26  moves heater  14 , and cooler actuator  27  moves cooler  24 . Heater fluid supply pipe  28 , heater fluid exit pipe  30 , cooler fluid supply pipe  32  and cooler fluid exit pipe  34  have sections that slide by one another like sections of a small telescope. Flexible pipes could be used instead of the telescoping sections. 
     There are many ways, such as cams and springs, to move regenerator  10 , heater  14 , and cooler  24 , but for ease of explanation, actuators  26 , and  27  will move regenerator  10 , heater  14 , and cooler  24 . 
     Regenerator  10 , heater  14 , and cooler  24  move back and forth (down and up) between cylinder head  4  and power piston  18  parallel to the axis of the cylinder. When heater  14  is moving down it allows fluid to move from the space below heater  14 , and above power piston  18  through heater  14  into the space between heater  14  and regenerator  10 . When regenerator  10  and cooler  24  are moving down they allow fluid to move from the space below regenerator  10 , and above heater  14  through regenerator  10  and cooler  24  into the space between cooler  24  and cylinder head  4 . When cooler  24  moves up it allows fluid to move from the space between cooler  24  and cylinder head  4  through cooler  24  into the space below cooler  24  and above regenerator  10 . When regenerator  10 , and heater  14  move up they allow fluid to move from the space between cooler  24  and regenerator  10  through regenerator  10  and heater  14  into the space below heater  14 , and above power piston  18 . Regenerator  10  is made from a permeable material such that when regenerator  10  moves down and the fluid flows through it, the material absorbs heat from the fluid. When regenerator  10  moves up, the permeable material gives up heat to the compressed fluid. 
     The means to move regenerator  10 , heater  14 , and cooler  24  are actuators  26 , and  27 . Other means can be used to move regenerator  10 , heater  14 , and cooler  24 , such as a push rod, and a rocker arm (not shown). These other means can be applied from above or below power piston  18 . The means can be hydraulic, pneumatic, electrical, mechanical, or any combination of them that will move regenerator  10 , heater  14 , and cooler  24  as required. 
     FIGS. 1 to  4 —Operation of Preferred Embodiment 
     The engine operates as follows: 
     Heater fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16  during the heating cycle and the expansion cycle. Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36  during the cooling cycle and the compression cycle. 
     Before FIG. 1 (Between FIG.  4  and FIG. 1) 
     The expanding fluid acting on power piston  18  moves power piston  18  down to about 85% of it&#39;s downward travel and delivers power output. 
     Heating fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16 . 
     After power piston  18  has moved about a third of it&#39;s way down, cooler  24  moves down, and catches up with power piston  18  at about 85% of power piston  18 &#39;s downward travel. 
     In FIG. 1 
     Power piston  18  is at about 85% of it&#39;s downward travel. 
     Regenerator  10 , and cooler  24  start to move down. 
     Between FIG.  1  and FIG. 2 
     Regenerator  10 , and cooler  24  continue to move down. 
     Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36 . 
     The working fluid going through regenerator  10  heats up regenerator  10 ; and regenerator  10 , and cooler  24  cool the working fluid. 
     Power piston  18  starts back up. 
     In FIG. 2 
     Power piston  18 , heater  14 , regenerator  10 , and cooler  24  are close to one another. 
     Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36 . 
     Between FIG.  2  and FIG. 3 
     Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36 . 
     Cooler  24  moves up to cylinder head  4 , and cools the working fluid that passes through it. 
     Power piston  18 , regenerator  10  and heater  14  move up together to about 85% of power piston&#39;s  18  upward travel. 
     Power piston  18  moving upwards compresses the working fluid in cylinder  12 . 
     In FIG. 3 
     Heater fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16 . 
     Power piston  18 , regenerator  10 , and heater  14 , are at about 85% of the upward travel of power piston  18 . 
     Cooler  24  is next to cylinder head  4 . 
     Between FIG.  3  and FIG. 4 
     Heater fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16 . 
     Regenerator  10  and heater  14  move away from power piston  18  and up against cooler  24 . 
     As regenerator  10  and heater  14  move up toward cooler  24 , the compressed working fluid moves through heater  14  and regenerator  10  and cools regenerator  10 ; and heater  14  and regenerator  10  heat up the working fluid. 
     In FIG. 4 
     Heater fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16 . 
     Cooler  24 , regenerator  10 , and heater  14  are up against cylinder head  4 . 
     Hot expanding fluid is pushing power piston  18  down. 
     The cycle repeats. 
     Important Features 
     The volume of the working fluid between regenerator  10  and cooler  24  can be adjusted by sizing heater fluid supply pipe  28  and heater fluid exit pipe  30  so that when regenerator  10  and heater  14  move away from power piston  18  no mechanical compression takes place even though power piston  18  continues to move up before it starts to move down. That is no mechanical compression takes place while regenerator  10  and heater  14  are heating the compressed working fluid. 
     The engine can be operated at minimum cycle pressures greater than atmospheric. 
     DESCRIPTION 
     FIGS.  4  to  8 —First Alternate Embodiment 
     This invention is a two stroke regenerative, reciprocating, external combustion engine employing a regenerator  10 , heater  14 , and cooler  24 . The first alternate embodiment of this invention employs two strokes divided into four cycles. The first cycle is the cooling cycle. The second is the compression cycle. The third is the heating cycle. And the fourth is the expansion cycle. The cooling cycle is from about 85% of the downward travel of power piston  18  to about 15% of the travel back up. The compression cycle is from about 15% of the travel back up of power piston  18  to about 85% of the upward travel of power piston  18 . The heating cycle is from about 85% of the upward travel of power piston  18  to about 15% of the downward travel of power piston  18 . The expansion cycle is from about top dead center to about 85% of the downward travel of power piston  18 . The above positions are all estimates and are given for descriptive purposes only. The actual position, at which a part of the cycle may begin or end, may be different from those set out above. (Shaft  7 , heater fluid supply pipe  28 , and heater fluid exit pipe  30  can be sized such that no mechanical compression takes place during regenerative heating). The heating and expansion cycles can overlap. 
     The cooling cycle begins with regenerator  10 , heater  14 , and cooler  24  adjacent to cylinder head  4  and ends with regenerator  10 , heater  14 , and cooler  24  adjacent to power piston  18 . During the cooling cycle, regenerator  10 , heater  14 , and cooler  24  move down (towards power piston  18 ) forcing the hot working fluid through regenerator  10 , and regenerator  10  absorbs heat from the working fluid (cooling the working fluid). 
     The compression cycle starts with regenerator  10 , heater  14 , and cooler  24  close to and moving up with power piston  18  and ends with regenerator  10 , heater  14 , and cooler  24  moving away from power piston  18 . 
     The heating cycle starts with regenerator  10 , heater  14 , and cooler  24  moving away from power piston  18  and ends with regenerator  10 , heater  14 , and cooler  24  adjacent to cylinder head  4 . During the heating cycle regenerator  10 , heater  14 , and cooler  24  are moved up through the working fluid trapped between power piston  18  and cylinder head  4  and transfer heat to this working fluid (heating the working fluid). The fluids that are expected to be employed in this invention is air. However, these fluids could be gas, liquids, or mixture of gases and liquids. 
     Cylinder  12  is closed at one end by cylinder head  4 . Cylinder  12  further contains power piston  18 , which is connected to power output shaft  22  by a connecting rod  20  (for converting the linear motion of the piston to the rotating motion of the shaft). The expanding gases exert a force on power piston  18 , (a cylindrical piston that can move up and down in cylinder  12 ). That force, exerted on power piston  18  moving it down, is transmitted via connecting rod  20  and power output shaft  22  to a load (not shown). Cylindrically shaped regenerator  10 , heater  14 , and cooler  24  is moved by shaft  7 . Heater fluid supply pipe  28  transfers hot fluid to heater  14  from heat source  16 , and heater fluid exit pipe  30  transfers spent fluid from heater  14  back to heat source  16 . Cooler fluid supply pipe  32  transfers cold fluid to cooler  24  from cold source  36 , and cooler fluid exit pipe  34  transfers spent fluid from cooler  24  back to cold source  36 . Regenerator actuator  25  through shaft  7  moves regenerator  10 , heater  14 , and cooler  24 . Heater fluid supply pipe  28 , heater fluid exit pipe  30 , cooler fluid supply pipe  32  and cooler fluid exit pipe  34  have sections that slide by one another like sections of a small telescope. 
     Regenerator actuator  25  moves shaft  7  with regenerator  10 , heater  14 , and cooler  24  attached to it between the power piston and cylinder head  4 . Regenerator actuator  25 , for ease of explanation, is a spring. 
     Regenerator actuator  25 , power piston  18 , and pressure forces on shaft  7  cause regenerator  10 , heater  14 , and cooler  24  to move back and forth (down and up) between cylinder head  4  and power piston  18  parallel to the axis of the cylinder. When regenerator  10 , heater  14 , and cooler  24  move up they allow working fluid to move from the space between cooler  24  and cylinder head  4  through cooler  24 , heater  14 , and regenerator  10  into the space below heater  14 , and above power piston  18 . When regenerator  10 , heater  14 , and cooler  24  are moving down they allow working fluid to move from the space below heater  14 , and above power piston  18  through heater  14 , regenerator  10 , and cooler  24  into the space between cooler  24  and cylinder head  4 . Regenerator  10  is made from a permeable material such that when regenerator  10  moves down and the working fluid flows through it, the material absorbs heat from the working fluid. When regenerator  10  moves up, the permeable material gives up heat to the compressed working fluid. 
     The means to move regenerator  10 , heater  14 , and cooler  24  is regenerator actuator  25 , a spring, Other means can be used to move shaft  7 , such as a push rod, and a rocker arm (not shown). These other means can be applied from above or below power piston  18 . The means can be hydraulic, pneumatic, electrical, mechanical or any combination of them that will move the shaft  7  as required. 
     FIGS. 5 to  8 —Operation of the First Alternate Embodiment 
     The engine operates as follows: 
     Working fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16  during the heating cycle. Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36  during the cooling cycle. 
     Before FIG. 5 (Between FIG.  8  and FIG. 5) 
     Power piston  18  is moving down as a result of pressure created by the working fluid expanding. 
     In FIG. 5 
     At about 85% of downward travel of power piston  18  pressure in cylinder  12  decreases to a point that the spring forces of regenerator actuator  25  exceed the pressure forces against the bottom of shaft  7 , and regenerator actuator  25  urges shaft  7 , regenerator  10 , heater  14 , and cooler  24  down. 
     Cooler fluid starts to come from cold source  36 , go to cooler  24 , and return cold source  36 . 
     Between FIG.  5  and FIG. 6 
     Cooler fluid comes from cold source  36 , goes to cooler  24 , and returns to cold source  36   
     Regenerator  10 , heater  14 , and cooler  24  move down. 
     The working fluid going through regenerator  10  heats up regenerator  10  and cools down the working fluid. 
     The working fluid going through cooler  24  is cooled by cooler  24 . 
     Power piston  18  starts back up. 
     In FIG. 6 
     Power piston  18  and heater  14  come together. 
     Between FIG.  6  and FIG. 7 
     Power piston  18  moves regenerator  10 , heater  14 , and cooler  24  up together. 
     Power piston  18  moving upwards compresses the working fluid and regenerator actuator  25 . 
     In FIG. 7 
     Power piston  18  and regenerator  10 , heater  14 , and cooler  24  are at about 85% of the upward travel of power piston  18 . 
     Heater fluid starts to come from heat source  16 , go to heater  14 , and return heat source  16 . 
     Between FIG.  7  and FIG. 8 
     Heater fluid comes from heat source  16 , goes to heater  14 , and returns to heat source  16 . 
     Compressed working fluid pressure acting on shaft  7  forces regenerator  10 , heater  14 , and cooler  24  away from power piston  18  and up against cylinder head  4 . 
     As regenerator  10 , heater  14 , and cooler  24  move up toward cylinder head  4 , the compressed working fluid moves through heater  14  and regenerator  10  and heats up. 
     In FIG. 8 
     Regenerator  10 , heater  14 , and cooler  24  are up against cylinder head  4 . 
     Power piston  18  is moving down. 
     The cycle repeats. 
     Important Features 
     The volume of the working fluid between cooler  24  and cylinder head  4  can be adjusted by sizing shaft  7 , heater fluid supply pipe  28 , and heater fluid exit pipe  30  so that when cooler  24 , regenerator  10 , and heater  14  move away from power piston  18  no mechanical compression takes place even though power piston  18  continues to move up before it starts to move down. That is no mechanical compression takes place while regenerator  10  and heater  14  are heating the compressed working fluid. 
     The engine can be operated at minimum cycle pressures greater than atmospheric. 
     Conclusion 
     Accordingly, the reader will see that Warren Cycle Engine meets the following objects and advantages: 
     (a) The engine compresses the working fluid in cylinder  12 , and the engine expands the working fluid in cylinder  12 . 
     (b) Regenerator  10  saves the heat from the spent working fluid and releases the heat to the compressed working fluid. 
     (c) The engine has no valves. 
     (d) The engine has no displacer piston. 
     (e) The engine will operate so that the charge is almost fully expanded. 
     Although the description above contains much specificity, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. 
     Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.