Patent Publication Number: US-2003226525-A1

Title: Warren cycle internal combustion engine with heat exchanger

Description:
BACKGROUND  
       [0001] 1. Field of Invention  
       [0002] The present invention relates to a reciprocating, two stroke internal combustion engine with four cylinders and one heat exchanger that transfers the heat from the exhaust to the compressed working fluid. The engine also has a compression ratio different from the expansion ratio to allow complete expansion.  
       [0003] 2. Description of Prior Art  
       [0004] The Warren Cycle Engine is a regenerated engine similar to the Stirling Cycle Engine, which is one of the more efficient of the practical engines, but its compression ratio is the same as its expansion ratio therefore it has a problem with under expansion of the charge. The Warren Cycle Engine solves this problem by making the compression ratio different from the expansion ratio. Complete expansion is achieved by having a cooled volume much smaller than the heated volume. The present invention achieves complete expansion by taking in less air than will fill the volume of cylinder  100 . Positioning movable wall  104  so that the desired amount of air is in cylinder  100  when power piston  106  recovers air inlet port  102  does this. This causes the volume of the cooled air about to be compressed to be smaller than the volume of the expanded air.  
       [0005] Previous engines also had trouble with the sizing of the regenerators. Both the high-pressure fluid and the low-pressure fluid used the same passages. What was the correct size for one was a problem for the other. The present invention uses a heat exchanger where each side can be sized for the fluid moving through it.  
       [0006] Previous engines used one regenerator per cylinder. The present invention uses only one heat exchanger for all four cylinders.  
       SUMMARY  
       [0007] The Warren cycle engine is the mechanization of the Warren Cycle. The Warren Cycle is an engine cycle where compression is adiabatic, heat is added at constant volume, expansion is adiabatic and complete, and the exhaust heat is transferred to the compressed air. The result is a two stroke, internal combustion, reciprocating, heat exchanging engine made up of heat exchanger high-pressure side  10 , heat exchanger low-pressure side  20 , and four similar working cylinders. Each cylinder  100 ,  200 ,  300 ,  400  is closed at one end and contains power pistons  106 ,  206 ,  306 ,  406  that are connected to power output shaft  50 . Movable walls  104 ,  204 ,  304 ,  404  are provided to take in the working fluid and push the exhaust out. As the exhaust moves out of cylinder  100 , its heat is transferred from heat exchanger low-pressure side  20  to heat exchanger high-pressure side  10  and to the compressed fluid of cylinder  300 . During the heating portion of the cycle movable wall  304  pushes the compressed fluid through heat exchanger high-pressure side  10  where the air is preheated. The air then moves back again into cylinder  300  where fuel is added and ignited. Movable wall  104  can move between power piston  106  and the top of cylinder  100 . Up movement wall cam  110 , down movement wall cam  112  and rocker arm  124  are provided to accomplish this movement at the appropriate times during the engine&#39;s operating cycle. Movable wall  104  is positioned so that the desired amount of air is in cylinder  100  at the time air inlet port  102  is recovered. This determines the engines power output and efficiency. In an alternate embodiment of this invention the engine operates with only two cylinders.  
       OBJECTS AND ADVANTAGES  
       [0008] The advantage of the Warren Cycle Internal Combustion Engine With Heat Exchanger is that it operates on the Warren Cycle.  
       [0009] Another advantage of the Warren Cycle Internal Combustion Engine With Heat Exchanger is it can use the exhaust heat of all four cylinders to preheat the compressed fluid using only one heat exchanger.  
       [0010] Another advantage of the Warren Cycle Internal Combustion Engine With Heat Exchanger is that it can be operated so that the charge is fully expanded.  
     
    
    
     DRAWING FIGURES  
     [0011]FIG. 1 shows the engine with the first cylinder, cylinder  100 , at the end of the expansion part of the cycle, and at the start of the inlet and exhaust part of the cycle.  
     [0012]FIG. 2 shows the engine with the first cylinder, cylinder  100 , at the end of the inlet and exhaust part of the cycle, and at the start of the compression part of the cycle.  
     [0013]FIG. 3 shows the engine with the first cylinder, cylinder  100 , at the end of the compression part of the cycle, and at the start of the heating part of the cycle.  
     [0014]FIG. 4 shows the engine with the first cylinder, cylinder  100 , at the end of the heating part of the cycle, and at the start of the expansion part of the cycle.  
     [0015]FIG. 5 shows the first alternate embodiment of the engine with the first cylinder, cylinder  100 , at the end of the expansion part of the cycle, and at the start of the inlet and exhaust part of the cycle.  
     [0016]FIG. 6 shows the first alternate embodiment of the engine with the first cylinder, cylinder  100 , at the end of the inlet and exhaust part of the cycle, and at the start of compression part of the cycle.  
     [0017]FIG. 7 shows the first alternate embodiment of the engine with the first cylinder, cylinder  100 , at the end of the compression part of the cycle, and at the start of the heating part of the cycle.  
     [0018]FIG. 8 shows the first alternate embodiment of the engine with the first cylinder, cylinder  100 , at the end of the heating part of the cycle, and at the start of the expansion part of the cycle.  
                               REFERENCE NUMERALS IN DRAWINGS                                                    heat exchanger high-pressure side   10                   heat exchanger low-pressure side   20       exhaust pipe   30       power output shaft   50       crankcase   60       cylinder   100   200   300   400       air inlet port   102   202   302   402       movable wall   104   204   304   404       power piston   106   206   306   406       connecting rod   108   208   308   408       up movement wall cam   110   210   310   410       down movement wall cam   112   212   312   412       heated air valve   114   214   314   414       low-pressure heat exchanger inlet valve   116   216   316   416       high-pressure heat exchanger inlet valve   118   218   318   418       compression ratio valve   120       320       push rod   122   222   322   422       rocker arm   124   224   324   424       valve cams   126   226   326   426       fuel injector   128   228   328   428       igniter   130   230   330   430                  
 
    
    
     Description  
     FIGS.  1  to  4   
     Preferred Embodiment  
     [0019] This invention is a two stroke, reciprocating, internal combustion engine with four cylinders  100 ,  200 ,  300 ,  400 , exhaust pipe  30 , power output shaft  50 , crankcase  60 , heat exchanger high-pressure side  10 , and heat exchanger low-pressure side  20 . The invention employs a two-stroke cycle divided into four parts. The first part is the intake and the exhaust part, the second is the compression part, the third is the heating part, and the fourth is the expansion part. The intake and exhaust part is from about 85% of the downward travel of power pistons  106 ,  206 ,  306 ,  406  to about 15% of the travel back up (or as measured by power output shaft  50  rotation from about 135° to about (225°). The compression part is from about 15% of the travel back up of power pistons  106 ,  206 ,  306 ,  406  (225°) to about top dead center. The heating part is from about 85% of the travel back up of power pistons  106 ,  206 ,  306 ,  406  (315°) to about 15% of the downward travel of power pistons  106 ,  206 ,  306 ,  406  (45°). The expansion part is from about top dead center to about 85% of the downward travel of power pistons  106 ,  206 ,  306 ,  406  (135°). The heating part of the cycle overlaps both the end of the compression part and the start of the expansion part of the cycle. The compression ratio adjustment is part of the air intake and exhaust part of the cycle. The above positions are all estimates and are given for descriptive purposes only. The actual position a part of the cycle may begin or end at may be different from those set out above.  
     [0020] Cylinders  100 ,  200 ,  300 ,  400  contain movable walls  104 ,  204 ,  304 ,  404 , power pistons  106 ,  206 ,  306 ,  406 , and connecting rods  108 ,  208 ,  308 ,  408 . Connecting rods  108 ,  208 ,  308 ,  408  are connected to power output shaft  50 , which operates valve cams  126 ,  226 ,  326 ,  426 , up movement wall cams  110 ,  210 ,  310 ,  410 , and down movement wall cams  112 ,  212 ,  312 ,  412 . Up movement wall cams  110 ,  210 ,  310 ,  410 , and down movement wall cams  112 ,  212 ,  312 ,  412  move rocker arms  124 ,  224 ,  324 ,  424  which move movable walls  104 ,  204 ,  304 ,  404  respectively.  
     [0021] Heat exchanger high-pressure side  10 , heat exchanger low-pressure side  20 , and power output shaft  50  are attached to cylinders  100 ,  200 ,  300 ,  400 . Also attached to cylinders  100 ,  200 ,  300 ,  400  are air inlet ports  102 ,  202 ,  302 ,  402 , heated air valves  114 ,  214 ,  314 ,  414 , low-pressure heat exchanger inlet valves  116 ,  216 ,  316 ,  416 , and high-pressure heat exchanger inlet valves  118 ,  218 ,  318 ,  418 , respectively. Heated air valves  114 ,  214 ,  314 ,  414  control the air flow out of heat exchanger high-pressure side  10 . Low-pressure heat exchanger inlet valves  116 ,  216 ,  316 ,  416  control the air flow into heat exchanger low-pressure side  20 . High-pressure heat exchanger inlet valves  118 ,  218 ,  318 ,  418  control the air flow into heat exchanger high-pressure side  10 .  
     [0022] Air inlet ports  102 ,  202 ,  302 ,  402  allow air into cylinders  100 ,  200 ,  300 ,  400  respectively. Heat exchanger low-pressure side  20  transfers exhaust heat to the compressed air in heat exchanger high-pressure side  10 . Movable walls  104 ,  204 ,  304 ,  404  take in air and push exhaust out through heat exchanger low-pressure side  20  and exhaust pipe  30  during the intake and exhaust part of the cycle. Movable walls  104 ,  204 ,  304 ,  404  also move air from between power pistons  106 ,  206 ,  306 ,  406  and themselves through heat exchanger high-pressure side  10  and into the top of cylinders  100 ,  200 ,  300 ,  400  during the heating part of the cycle.  
     [0023] Fuel is injected by fuel injectors  128 ,  228 ,  328 ,  428 , and ignited by the hot air or by igniters  130 ,  230 ,  330 ,  430 . Power pistons  106 ,  206 ,  306 ,  406 , along with connecting rods  108 ,  208 ,  308 ,  408  and power output shaft  50  transfer work from the hot expanding air to a power takeoff device not shown. Up movement wall cams  110 ,  210 ,  310 ,  410 , push rods  122 ,  222 ,  322 ,  422 , and rocker arms  124 ,  224 ,  324 ,  424  move movable walls  104 ,  204 ,  304 ,  404  up during the air intake and exhaust part of the cycle. Down movement wall cams  112 ,  212 ,  312 ,  412 , push rods  122 ,  222 ,  322 ,  422 , and rocker arms  124 ,  224 ,  324 ,  424  move movable walls  104 ,  204 ,  304 ,  404  down during the heating and expansion parts of the cycle. Valve cams  126 ,  226 ,  326 ,  426  and springs not shown open and close valves.  
     [0024] Air is expected to be employed as the working fluid in this engine. However, the working fluid could be any mixture of gases, liquids, and solids that can be ignited and burned. After heating the working fluid is referred to as spent working fluid or exhaust. Movable walls  104 ,  204 ,  304 ,  404  are shown being moved by cams, electric or hydraulic actuators (not shown) can also move them.  
     Operation  
     FIGS.  1  to  4   
     Preferred Embodiment  
     [0025] FIGS.  1  to  4  present the sequence of steps or processes occurring in the engine. For cylinder  100 , the air intake and exhaust part of the cycle takes place between FIGS. 1 and 2. The compression part of the cycle takes place between FIGS. 2 and 3. The heating part of the cycle takes place between FIGS. 3 and 4. The expansion part of the cycle takes place between FIGS. 4 and 1.  
     [0026] For cylinder  200 , the air intake and exhaust part of the cycle takes place between FIGS. 4 and 1. The compression part of the cycle takes place between FIGS. 1 and 2. The heating part of the cycle takes place between FIGS. 2 and 3. The expansion part of the cycle takes place between FIGS. 3 and 4.  
     [0027] For cylinder  300 , the air intake and exhaust part of the cycle takes place between FIGS. 3 and 4. The compression part of the cycle takes place between FIGS. 4 and 1. The heating part of the cycle takes place between FIGS. 1 and 2. The expansion part of the cycle takes place between FIGS. 2 and 3.  
     [0028] For cylinder  400 , the air intake and exhaust part of the cycle takes place between FIGS. 2 and 3. The compression part of the cycle takes place between FIGS. 3 and 4. The heating part of the cycle takes place between FIGS. 4 and 1. The expansion part of the cycle takes place between FIGS. 1 and 2 FIG. 1 shows power piston  106  at about 85% of downward travel (135°). Cylinder  100  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  102  is being uncovered, heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is starting open, high-pressure heat exchanger inlet valve  118  is closed, and movable wall  104  is just above power piston  106 .  
     [0029] In cylinder  200  there is a charge of fresh air between movable wall  204  and power piston  206  which is at about 15% of its upward travel (225°). Air inlet port  202  has just been recovered, heated air valve  214  is closed, low-pressure heat exchanger inlet valve  216  is open, high-pressure heat exchanger inlet valve  218  is closed, and movable wall  204  is moving to the top of cylinder  200 .  
     [0030] In cylinder  300 , power piston  306  is at about 85% of its upward travel (315°). Heated air valve  314 , is opening, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is opening, and movable wall  304  is adjacent to the top of cylinder  300 .  
     [0031] In cylinder  400 , power piston  406  is at about 15% of its downward travel (45°). Heated air valve  414 , is closing, low-pressure heat exchanger inlet valve  416  is closed, high-pressure heat exchanger inlet valve  418  is closing, and movable wall  404  is adjacent to the top of power piston  406 .  
     [0032] Between FIG. 1 and FIG. 2, in cylinder  100  air intake and exhaust is taking place. Air inlet port  102  is uncovered, heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is open, high-pressure heat exchanger inlet valve  118  is closed. Movable wall  104  moves up in cylinder  100 . While movable wall  104  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  104  is moving up, it takes in fresh air through air inlet port  102  until the correct amount of air is in cylinder  100 . Power piston  106  continues down to the bottom of cylinder  100  and comes up again to about 15% of upward travel of power piston  106  (225°).  
     [0033] In cylinder  200  compression takes place. Air inlet port  202  is recovered, heated air valve  214 , is closed, movable wall  204  moves adjacent to the top of cylinder  200 , low-pressure heat exchanger inlet valve  216  closes when movable wall  204  reaches the top of cylinder  200 , and high-pressure heat exchanger inlet valve  218  is closed. Power piston  206  continues up in cylinder  200  to about 85% of its upward travel (225°).  
     [0034] In cylinder  300  heating takes place. Heated air valve  314  is open, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is open, and movable wall  304  moves adjacent to the top of power piston  306 . While movable wall  304  is moving down to the top of power piston  306  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  300 . Power piston  306  continues up then down in cylinder  300  until about 15% of its downward travel (45°).  
     [0035] In cylinder  400  expansion takes place. Heated air valve  414  is closed, low-pressure heat exchanger inlet valve  416  is closed, high-pressure heat exchanger inlet valve  418  is closed, and movable wall  404  is adjacent to the top of power piston  406 . Power piston  406  and movable wall  404  move down to about 85% of power piston&#39;s  406  downward travel (135°) as power output takes place.  
     [0036]FIG. 2 shows there is a charge of fresh air in cylinder  100  between movable wall  104  and power piston  106  which is at about 15% of its upward travel (225°). Air inlet port  102  has just been recovered, heated air valve  114 , is closed, low-pressure heat exchanger inlet valve  116  is open, high-pressure heat exchanger inlet valve  118  is closed, and movable wall  104  is moving to the top of cylinder  100 .  
     [0037] In cylinder  200 , power piston  206  is at about 85% of its upward travel (315°). Heated air valve  214  is opening, low-pressure heat exchanger inlet valve  216  is closed, high-pressure heat exchanger inlet valve  218  is opening, and movable wall  204  is adjacent to the top of cylinder  200 .  
     [0038] In cylinder  300 , power piston  306  is at about 15% of its downward travel (45°). Heated air valve  314  is closing, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is closing, and movable wall  304  is adjacent to the top of power piston  306 .  
     [0039] In cylinder  400 , power piston  406  is at about 85% of downward travel (135°). Cylinder  400  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  402  is being uncovered, heated air valve  414 , is closed, low-pressure heat exchanger inlet valve  416  is starting open, high-pressure heat exchanger inlet valve  418  is closed, and movable wall  404  is just above power piston  406 .  
     [0040] Between FIG. 2 and FIG. 3, in cylinder  100  compression takes place. Air inlet port  102  is recovered, heated air valve  114  is closed, movable wall  104  moves adjacent to the top of cylinder  100 , low-pressure heat exchanger inlet valve  116  closes when movable wall  104  reaches the top of cylinder  100 , and high-pressure heat exchanger inlet valve  118  is closed. Power piston  106  continues up in cylinder  100  to about 85% of its upward travel (225°).  
     [0041] In cylinder  200  heating takes place. Heated air valve  214  is open, low-pressure heat exchanger inlet valve  216  is closed, high-pressure heat exchanger inlet valve  218  is open, and movable wall  204  moves adjacent to the top of power piston  206 . While movable wall  204  is moving down to the top of power piston  206  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  200 . Power piston  206  continues up then down in cylinder  200  until about 15% of its downward travel (45°).  
     [0042] In cylinder  300  expansion takes place. Heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is closed, and movable wall  304  is adjacent to the top of power piston  306 . Power piston  306  and movable wall  304  move down to about 85% of power piston&#39;s  306  downward travel (135°) as power output takes place.  
     [0043] In cylinder  400  air intake and exhaust is taking place. Air inlet port  402  is uncovered, heated air valve  414  is closed, low-pressure heat exchanger inlet valve  416  is open, high-pressure heat exchanger inlet valve  418  is closed, and movable wall  404  moves up in cylinder  400 . While movable wall  404  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  404  is moving up, it takes in fresh air through air inlet port  402  until the correct amount of air is in cylinder  400 . Power piston  406  continues down to the bottom of cylinder  400  and comes up again to about 15% of its upward travel (225°).  
     [0044]FIG. 3 shows that in cylinder  100  power piston  106  is at about 85% of its upward travel (315°). Heated air valve  114  is opening, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is opening, and movable wall  104  is adjacent to the top of cylinder  100 .  
     [0045] In cylinder  200 , power piston  206  is at about 15% of its downward travel (45°). Heated air valve  214 , is closing, low-pressure heat exchanger inlet valve  216  is closed, high-pressure heat exchanger inlet valve  218  is closing, and movable wall  204  is adjacent to the top of power piston  206 .  
     [0046] In cylinder  300 , power piston  306  is at about 85% of downward travel (135°). Cylinder  300  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  302  is being uncovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is starting to open, high-pressure heat exchanger inlet valve  318  is closed, and movable wall  304  is just above power piston  306 .  
     [0047] In cylinder  400 , there is a charge of fresh air between movable wall  404  and power piston  406  which is at about 15% of its upward travel (225°). Air inlet port  402  has just been recovered, heated air valve  414  is closed, low-pressure heat exchanger inlet valve  416  is open, high-pressure heat exchanger inlet valve  418  is closed, and movable wall  404  is moving to the top of cylinder  400 .  
     [0048] Between FIG. 3 and FIG. 4, in cylinder  100  heating takes place. Heated air valve  114  is open, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is open, and movable wall  104  moves adjacent to the top of power piston  106 . While movable wall  104  is moving down to the top of power piston  106  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  100  Power piston  106  continues up then down in cylinder  100  until about 15% of its downward travel (45°).  
     [0049] In cylinder  200  expansion takes place. Heated air valve  214  is closed, low-pressure heat exchanger inlet valve  216  is closed, high-pressure heat exchanger inlet valve  218  is closed, and movable wall  204  is adjacent to the top of power piston  206 . Power piston  206  and movable wall  204  move down to about 85% of power piston&#39;s  206  downward travel (135°) as power output takes place.  
     [0050] In cylinder  300  air intake and exhaust is taking place. Air inlet port  302  is uncovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is open, high-pressure heat exchanger inlet valve  318  is closed, and movable wall  304  moves up in cylinder  300 . While movable wall  304  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  304  is moving up, it takes in fresh air through air inlet port  302  until the correct amount of air is in cylinder  300 . Power piston  306  continues down to the bottom of cylinder  300  and comes up again to about 15% of its upward travel (225°).  
     [0051] In cylinder  400  compression takes place. Air inlet port  402  is recovered, heated air valve  414  is closed, movable wall  404  moves adjacent to the top of cylinder  400 , low-pressure heat exchanger inlet valve  416  closes when movable wall  404  reaches the top of cylinder  400 , and high-pressure heat exchanger inlet valve  418  is closed. Power piston  406  continues up in cylinder  400  to about 85% of its upward travel (225°).  
     [0052]FIG. 4 shows that in cylinder  100  power piston  106  is at about 15% of its downward travel (45°). Heated air valve  114  is closing, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is closing, and movable wall  104  is moving to the top of power piston  106 .  
     [0053] In cylinder  200 , power piston  206  is at about 85% of downward travel (135°). Cylinder  200  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  202  is being uncovered, heated air valve  214  is closed, low-pressure heat exchanger inlet valve  216  is starting to open, high-pressure heat exchanger inlet valve  218  is closed, and movable wall  204  is just above power piston  206 .  
     [0054] In cylinder  300 , there is a charge of fresh air between movable wall  304  and power piston  306  which is at about 15% of its upward travel (225°). Air inlet port  302  has just been recovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is open, high-pressure heat exchanger inlet valve  318  is closed, and movable wall  304  is moving to the top of cylinder  300   
     [0055] In cylinder  400 , Heated air valve  414  is opening, low-pressure heat exchanger inlet valve  416  is closed, high-pressure heat exchanger inlet valve  418  is opening, and movable wall  404  is adjacent to the top of cylinder  400 .  
     [0056] Between FIG. 4 and FIG. 1, in cylinder  100  expansion takes place. Heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is closed, and movable wall  104  is adjacent to the top of power piston  106 . Power piston  106  and movable wall  104  move down to about 85% of power piston&#39;s  106  downward travel (135°), as power output takes place.  
     [0057] In cylinder  200  air intake and exhaust is taking place. Air inlet port  202  is uncovered, heated air valve  214  is closed, low-pressure heat exchanger inlet valve  216  is open, high-pressure heat exchanger inlet valve  218  is closed, and movable wall  204  moves up in cylinder  200 . While movable wall  204  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  204  is moving up it takes in fresh air through air inlet port  202  until the correct amount of air is in cylinder  200 . Power piston  206  continues down to the bottom of cylinder  200  and comes up again to about 15% of its upward travel (225°).  
     [0058] In cylinder  300  compression takes place. Air inlet port  302  is recovered, heated air valve  314  is closed, movable wall  304  moves adjacent to the top of cylinder  300 , low-pressure heat exchanger inlet valve  316  closes when movable wall  304  reaches the top of cylinder  300 , and high-pressure heat exchanger inlet valve  318  is closed. Power piston  306  continues up in cylinder  300  to about 85% of its upward travel (225°).  
     [0059] In cylinder  400  heating takes place. Heated air valve  414  is open, low-pressure heat exchanger inlet valve  416  is closed, high-pressure heat exchanger inlet valve  418  is open, and movable wall  404  moves adjacent to the top of power piston  406 . While movable wall  404  is moving down to the top of power piston  406  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  400 . Power piston  406  continues up then down in cylinder  400  until about 15% of its downward travel (45°).  
     Description  
     FIGS.  5  to  8   
     First Alternate Embodiment of the Invention  
     [0060] The first alternate embodiment of the invention is a two stroke, reciprocating, internal combustion engine with two cylinders  100  and  300 , exhaust pipe  30 , power output shaft  50 , crankcase  60 , heat exchanger high-pressure side  10 , and heat exchanger low-pressure side  20 . The invention employs a two-stroke cycle divided into four parts. The first part is the intake and the exhaust part, the second is the compression part, the third is the heating part, and the fourth is the expansion part. The intake and exhaust part is from about 85% of the downward travel of power pistons  106  and  306  to about 15% of the travel back up (or as measured by power output shaft  50  rotation from about 135° to about (225°). The compression part is from about 15% of the travel back up of power pistons  106 , and  306  (225°) to about top dead center. The heating part is from about 85% of the travel back up of power pistons  106  and  306  (315°) to about 15% of the downward travel of power pistons  106  and  306  (45°). The expansion part is from about top dead center to about 85% of the downward travel of power pistons  106  and  306  (135°). The heating part of the cycle overlaps both the end of the compression part and the start of the expansion part of the cycle. The compression ratio adjustment is part of the air compression part of the cycle. The above positions are all estimates and are given for descriptive purposes only. The actual position a part of the cycle may begin or end at may be different from those set out above.  
     [0061] Cylinders  100  and  300  contain movable walls  104  and  304 , power pistons  106  and  306 , and connecting rods  108  and  308 . Connecting rods  108  and  308  are connected to power output shaft  50 , which operates valve cams  126  and  326 , up movement wall cams  110  and  310 , and down movement wall cams  112  and  312 . Up movement wall cams  110  and  310 , and down movement wall cams  112  and  312  move rocker arms  124  and  324  which move movable walls  104  and  304  respectively.  
     [0062] Heat exchanger high-pressure side  10 , heat exchanger low-pressure side  20 , and power output shaft  50  are attached to cylinders  100  and  300 . Also attached to cylinders  100  and  300  are air inlet ports  102  and  302 , heated air valves  114  and  314 , low-pressure heat exchanger inlet valves  116  and  316 , and high-pressure heat exchanger inlet valves  118  and  318 , respectively. Heated air valves  114  and  314  control the airflow out of heat exchanger high-pressure side  10 . Low-pressure heat exchanger inlet valves  116  and  316  control the airflow into heat exchanger low-pressure side  20 . High-pressure heat exchanger inlet valves  118  and  318  control the airflow into heat exchanger high-pressure side  10 . Compression ratio valves  120  and  320  control the compression ratio of the engine. The compression ratio of the engine can be set different from the expansion ratio.  
     [0063] Air inlet ports  102  and  302  allow air into cylinders  100  and  300  respectively. Heat exchanger low-pressure side  20  transfers exhaust heat to the compressed air in heat exchanger high-pressure side  10 . Movable walls  104  and  304  take in air and push exhaust out through heat exchanger low-pressure side  20  and exhaust pipe  30  during the intake and exhaust part of the cycle. Movable walls  104  and  304  also move air from between power pistons  106  and  306  and themselves through heat exchanger high-pressure side  10  into the top of cylinders  100  and  300  during the heating part of the cycle.  
     [0064] Fuel is injected by fuel injectors  128  and  328 , and ignited by the hot air or by igniters  130  and  330 . Power pistons  106  and  306  along with connecting rods  108  and  308  and power output shaft  50  transfer work from the hot expanding air to a power takeoff device not shown. Up movement wall cams  110  and  310 , push rods  122  and  322 , and rocker arms  124  and  324  move movable walls  104  and  304  up during the air intake and exhaust part of the cycle. Down movement wall cams  112  and  312 , push rods  122  and  322 , and rocker arms  124  and  324  move movable walls  104  and  304  down during the heating and expansion parts of the cycle. Valve cams  126  and  326  and springs not shown open and close valves.  
     Operation  
     FIGS.  5  to  8   
     First Alternate Embodiment of the Invention  
     [0065] FIGS.  5  to  8  present the sequence of steps or processes occurring in the engine. For cylinder  100 , the air intake and exhaust part of the cycle takes place between FIGS. 5 and 6. The compression part of the cycle takes place between FIGS. 6 and 7. The heating part of the cycle takes place between FIGS. 7 and 8. The expansion part of the cycle takes place between FIGS. 8 and 5.  
     [0066] For cylinder  300 , the air intake and exhaust part of the cycle takes place between FIGS. 7 and 8. The compression part of the cycle takes place between FIGS. 8 and 5. The heating part of the cycle takes place between FIGS. 5 and 6. The expansion part of the cycle takes place between FIGS. 6 and 7.  
     [0067]FIG. 5 shows power piston  106  at about 85% of downward travel (135°). Cylinder  100  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  102  is being uncovered, heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is starting to open, high-pressure heat exchanger inlet valve  118  is closed, compression ratio valve  120  is closed, and movable wall  104  is just above power piston  106 .  
     [0068] In cylinder  300 , power piston  306  is at about 85% of its upward travel (315°). Heated air valve  314  is opening, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is opening, compression ratio valve  320  is closed, and movable wall  304  is adjacent to the top of cylinder  300 .  
     [0069] Between FIG. 5 and FIG. 6, in cylinder  100  air intake and exhaust is taking place. Air inlet port  102  is uncovered, heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is open, high-pressure heat exchanger inlet valve  118  is closed, compression ratio valve  120  is closed, and movable wall  104  moves up to the top of cylinder  100 . While movable wall  104  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  104  is moving up, it takes in fresh air through air inlet port  102 . Power piston  106  continues down to the bottom of cylinder  100  and comes up again to about 15% of upward travel of power piston  106  (225°).  
     [0070] In cylinder  300  heating takes place. Heated air valve  314  is open, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is open, compression ratio valve  320  is closed, and movable wall  304  moves adjacent to the top of power piston  306 . While movable wall  304  is moving down to the top of power piston  306  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  300 . Power piston  306  continues up then down in cylinder  300  until about 15% of its downward travel (45°).  
     [0071]FIG. 6 shows there is a charge of fresh air in cylinder  100  between movable wall  104  and power piston  106  which is at about 15% of its upward travel (225°). Air inlet port  102  has just been recovered, heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is closing, high-pressure heat exchanger inlet valve  118  is closed, compression ratio valve  120  is opening, and movable wall  104  is at the top of cylinder  100 .  
     [0072] In cylinder  300 , power piston  306  is at about 15% of its downward travel (45°). Heated air valve  314  is closing, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is closing, compression ratio valve  320  is closed, and movable wall  304  is adjacent to the top of power piston  306 .  
     [0073] Between FIG. 6 and FIG. 7, in cylinder  100  compression takes place. Air inlet port  102  is recovered, heated air valve  114  is closed, movable wall  104  is adjacent to the top of cylinder  100 , low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is closed, and compression ratio valve  120  is open. Compression ratio valve  120  closes when the correct amount of air for the desired compression ratio is left in cylinder  100 . Power piston  106  continues up in cylinder  100  to about 85% of its upward travel (225°).  
     [0074] In cylinder  300  expansion takes place. Heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is closed, compression ratio valve  320  is closed, and movable wall  304  is adjacent to the top of power piston  306 . Power piston  306  and movable wall  304  move down to about 85% of power piston&#39;s  306  downward travel (135°) as power output takes place.  
     [0075]FIG. 7 shows that in cylinder  100  power piston  106  is at about 85% of its upward travel (315°). Heated air valve  114  is opening, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is opening, compression ratio valve  120  is closed, and movable wall  104  is adjacent to the top of cylinder  100 .  
     [0076] In cylinder  300 , power piston  306  is at about 85% of downward travel (135°). Cylinder  300  has completed the expansion part of the cycle and is about to start the intake and exhaust part. Air inlet port  302  is being uncovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is starting to open, high-pressure heat exchanger inlet valve  318  is closed, compression ratio valve  320  is closed, and movable wall  304  is just above power piston  306 .  
     [0077] Between FIG. 7 and FIG. 8, in cylinder  100  heating takes place. Heated air valve  114  is open, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is open, compression ratio valve  120  is closed, and movable wall  104  moves adjacent to the top of power piston  106 . While movable wall  104  is moving down to the top of power piston  106  compressed air heats up as it is forced though heat exchanger high-pressure side  10  and is heated further by burning fuel after it reenters cylinder  100 . Power piston  106  continues up then down in cylinder  100  until about 15% of its downward travel (45°).  
     [0078] In cylinder  300  air intake and exhaust is taking place. Air inlet port  302  is uncovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is open, high-pressure heat exchanger inlet valve  318  is closed, compression ratio valve  320  is closed, and movable wall  304  moves up to the top of cylinder  300 . While movable wall  304  is moving up exhaust gases are moving through heat exchanger low-pressure side  20  and cooling while heating up heat exchanger high-pressure side  10  on their way out exhaust pipe  30 . Also while movable wall  304  is moving up, it takes in fresh air through air inlet port  302 . Power piston  306  continues down to the bottom of cylinder  300  and comes up again to about 15% of its upward travel (225°).  
     [0079]FIG. 8 shows that in cylinder  100  power piston  106  is at about 15% of its downward travel (45°). Heated air valve  114  is closing, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is closing, compression ratio valve  120  is closed, and movable wall  104  is moving to the top of power piston  106 .  
     [0080] In cylinder  300 , there is a charge of fresh air between movable wall  304  and power piston  306  which is at about 15% of its upward travel (225°). Air inlet port  302  has just been recovered, heated air valve  314  is closed, low-pressure heat exchanger inlet valve  316  is closing, high-pressure heat exchanger inlet valve  318  is closed, compression ratio valve  320  is opening, and movable wall  304  is at the top of cylinder  300 .  
     [0081] Between FIG. 8 and FIG. 5, in cylinder  100  expansion takes place. Heated air valve  114  is closed, low-pressure heat exchanger inlet valve  116  is closed, high-pressure heat exchanger inlet valve  118  is closed, compression ratio valve  120  is closed, and movable wall  104  is adjacent to the top of power piston  106 . Power piston  106  and movable wall  104  move down to about 85% of power piston&#39;s  106  downward travel (135°), as power output takes place.  
     [0082] In cylinder  300  compression takes place. Air inlet port  302  is recovered, heated air valve  314  is closed, movable wall  104  is adjacent to the top of cylinder  300 , low-pressure heat exchanger inlet valve  316  is closed, high-pressure heat exchanger inlet valve  318  is closed, and compression ratio valve  320  is open. Compression ratio valve  320  closes when the correct amount of air for the desired compression ratio is left in cylinder  300 . Power piston  306  continues up in cylinder  300  to about 85% of its upward travel (225°).  
     CONCLUSION  
     [0083] One advantage of the Warren Cycle Internal Combustion Engine With Heat Exchanger is that it can use the exhaust heat of all four cylinders to preheat the compressed fluid while using only one heat exchanger.  
     [0084] Another advantage of the Warren Cycle Internal Combustion Engine with Heat Exchanger is that it can be operated so that the charge is fully expanded.