Field of the Invention The present invention is directed to energy reco¬ very fluid motors and, more particularly, to a fluid motor wherein the high pressure driving liquid changes phase throughout a power stroke, which is after a charging stroke and before exhausting from the motor.

Background of the Invention Various fluid circuits, especially refrigeration and/or heating systems, include segments where a higher pressure liquid is throttled through a valve to a lower pressure reservoir. In an absorption refrigeration system, for example, a higher pressure liquid passes through a control valve to a lower pressure evaporator. The evaporator absorbs heat from the environment thereby refrigerating the environment as desired. As the liquid is throttled through the valve, it at least partially changes phase. There is a loss not only of flow energy due to the pressure decrease through the valve, but also a loss of energy to the liquid when it changes phase from a liquid to a gas. The present invention is directed to convert some of the otherwise lost energy to mechanical energy.

Summarv of the Invention The present invention is directed to a motor for powering a use device wherein the motor uses pressurized, saturated liquid fluid from a source as input and exhausts the fluid when expended to a drain. The motor includes a casing having a charging chamber and an exhaust chamber with mechanism for reciprocating to simultaneously increase the size of one of the charging and exhaust chambers while decreasing the size of the other. The motor further includes a mechanism for moving the reciprocating mechanism through a charging/exhaust stroke and a power stroke, the moving mecha-

nis has a first mechanism for selectively placing the source and the charging chamber in fluid communication with one another to move the reciprocating mechanism through the charging/exhaust stroke and placing the exhaust chamber in fluid communication with the drain, the moving mechanism also has second mechanism for selectively placing the charging and exhaust chambers in fluid communication with one another to form a single motor chamber and allow the saturated liquid to at least partially expand and change phase forcing the reciprocating mechanism to move through the power stroke. In addition, the motor includes a mechanism for controlling the first and second selectively placing mechanisms and a mecha¬ nism for transferring to a use device energy from the moving reciprocating mechanism. In another embodiment, the first and second selec¬ tively placing mechanisms include a valve having first and second positions which accomplish the intended functions.

In still a further embodiment, the energy trans¬ ferring mechanism to a use device includes a second casing and a second piston connected by a main shaft to the first piston. This embodiment has further advantage in that equal power strokes are obtained during each half cycle. Therefore, energy is continuously converted and is provided to the use device in a relatively constant fashion. The present motor receives- pressurized, saturated or near saturated liquid through the valve to fill the charging chamber and hydraulically move the piston in a charging stroke while at the same time expelling spent liquid, now a liquid/vapor mixture in an exhaust stroke. When the charging/exhaust stroke is completed, the valve is shifted so that both the charging and exhaust chambers are placed in fluid communication with one another to form a

single motor chamber. The saturated .or near saturated liquid expands and at least partially changes phase. Due to the different face areas on opposite sides of the piston, the expanding vapor/liquid forces the piston in a power stroke, and, with mechanism such as a shaft attached to the piston, energy is supplied to the use devicei The next charging/exhaust stroke drives the spent liquid and vapor mixture from the motor. In this way, in a system wherein fluid pressure is otherwise decreased, generally through a valve, the present motor advantageously recovers energy and converts it to useful work.

Although the invention has been thusly summarized, preferred and other embodiments and the advantages of the invention are further described and explained and may be better understood by reference to the following drawings and the detailed descriptive matter thereafter.

Brief Description of the Drawings FIGURE 1 is a schematic of a fluid system incor- porating a mixed-phase motor in accordance with the present invention;

FIGURES 2A and 2B illustrate charging/exhaust stroke and power stroke configurations of a single chamber motor in accordance with the present invention, respectively; FIGURES 3A and 3B illustrate a motor similar to

FIGURES 2A and 2B with a force mechanism for insuring piston movement during the charging/exhaust stroke;

FIGURES 4A and 4B illustrate both half cycle con¬ figurations of a dual chamber motor in accordance with the present invention;

FIGURE 5 illustrates a typical temperature versus entropy phase diagram;

FIGURΞ 6 illustrates a typical pressure versus enthalpy phase diagram; and

FIGURE 7 illustrates a typical pressure versus spe¬ cific volume phase diagram. Detailed Description of the Preferred and Other Embodiments Referring now to the drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIGURES 1 and 2, a motor in its simplest form of a type in accordance with the present invention is designated generally by the numeral 10 and shown incorporated in a single working fluid system generally designat.ed by the numeral 12. It is understood that the single working fluid system is exemplary and that the present invention is also applicable to use in other systems, particularly single effect and double effect absorption refrigeration systems.

System 12 shows a compressor 14 in fluid com- munication via line 16 with a condensor 18. Condensor 18 is in fluid communication via line 20 with mixed-phase motor 10. The broken line 22 illustrates that motor 10 at least par¬ tially drives compressor 14. In system 12, it is understood that additional motive power is needed as well to drive the compressor 14, as further indicated by auxiliary motor 13 and broken line 15- _ Fluid from motor 10 exhausts through line 24 to evaporator 26 and then again feeds compressor 14 via line 28. It is noted that an auxiliary motor may not be needed in some fluid systems in which a mixed-phase motor may be used, for example, an absorption refrigeration system.

System 12 yields heat to the environment at conden¬ sor 18 and provides a liquid saturated or close to saturation as its output. The liquid is at a high pressure as a result

of the work accomplished by compressor 14. A mixed-phase motor 10 reduces the pressure while at the same time reco¬ vering energy which is used to partially drive compressor 14. The fluid exhausted by motor 10 is partially a liquid and partially a vapor. Evaporator 26 absorbs heat and provides a vapor as an output. Thus, as a part of system 12, -mixed- phase motor 10 of the present invention receives a high pressure, .saturated liquid and converts energy therein to exhaust a lower pressure fluid in partially liquid and vaporous states.

As shown in FIGURES 2A and 2B, motor 10 includes a casing 30 which forms a main chamber 32. In FIGURE 2A, a piston 34 divides main chamber 32 into a charging chamber 36 and an exhaust chamber 38. It is understood that piston 34 i _s representataive of reciprocating mechanisms and that other such mechanisms, such as a diaphragm, are equivalent. It is noted that the charging/exhaust stroke of motor 10 occurs while piston 34 is moving to increase the size or volume of charging chamber 36. The power stroke occurs while piston 34 is moving in a direction opposite to the direction of the charging/exhaust stroke. A shaft 40 is connected to piston 34 and extends through charging chamber 36 and a wall 42 of casing 30. It is understood that shaft 40 is attached to appropriate mechanism for mechanicall driving a use device (not shown). . It is further- understood that seals and other such mechanisms are used on piston 34 and shaft 40 as known to those skilled in the art. Main chamber 32 is pre¬ ferably cylindrical with a diameter d _] _. Piston 34 with appropriate seals has a similar diameter. Shaft 40 has a diameter d2«

Motor 10 also includes a four-way, two position valve 44. In the charging/exhaust stroke configuration shown

— a¬

in FIGURE 2A, valve 44 is in a first position wherein the charging chamber 36 is in fluid communication via line 46, valve 44, and line 48 with a source of pressurized, saturated or near saturated liquid. The hydraulic flow of the liquid is often sufficient to move piston 34 in the charging/exhaust stroke. Exhaust chamber 38 is in fluid communication via line 50, valve 44, and line 52 with a drain port 54- Spent mixture is exhausted through drain port 54 from exhaust chamber 38. It is understood that drain port 54 may actually be a part of valve 44. It is also understood that line 48 and drain port 54 may connect with additional fluid circuitry of a typical type as shown in FIGURE 1. In the power stroke configuration as shown in FIGURE 2B, valve 44 is in a second position wherein charging chamber 36 and exhaust chamber 38 are in fluid communication with one another via lines 50 and 46 through valve 44. Thus connected, the charging chamber and exhaust chamber form one motor chamber 39.

As soon as motor chamber 39 is formed, the liquid in what was charging chamber 36 expands into what was exhaust chamber 38 and partially vaporizes. The pressure of the liquid/vapor mixture forming on the non-shaft side of motor chamber 39 is equal to the pressure on the shaft side, but it acts against the entire face of piston 34 in opposition to the liquid pressure on the shaft side of the piston having a face area minus the shaft area. Because the area on the non-shaft side is so much greater than on the shaft side, the force exerted by the liquid/vapor mixture is overpowering compared to the force exerted by the liquid on the shaft side. Hence, piston 34 is moved by the liquid/vapor mixture through the power stroke.

Valve 44 and piston 34 cooperate closely with one

another so that the ends of the strokes cause valve switching, and when valve 44 switches, piston 34 changes direction. As shown in FIGURE 2A, a limit switch 60 senses piston 34 at the end of the charging/exhaust stroke and communicates electri- cally via line 62 with the solenoid 64 of valve 44 which causes valve 44 to switch. Switch 60 and solenoid 64 are in electrical communication with an electrical source via lines 66 and 68.

Likewise, a limit switch 70 senses piston 34 at the end of the power stroke. Switch 70 is in electrical com¬ munication with solenoid 72 of valve 44 via line 74. Switch 70 and solenoid 72 are in electrical communication with a source via lines 76 and 78.

It is understood that limit switches 60 and 70 can take a variety of forms. They may sense, for example, motion based on mechanical, electrical, magnetic, hydraulic or other physical principles. In like fashion, they may communicate with valve 44 via a signal that is mechanical, electrical, magnetic, hydraulic or a signal of some other physical type. The important consideration is that the end motion of piston 34 must be sensed in both directions and that a signal is sent to control valve 44.

In the embodiment of FIGURES 2A and 2B, it is assumed according to description hereinafter that the geometry of the motor 10 and the state of the working fluid are such that the fluid will drive piston 34 on the charging/exhaust stroke, albeit at a lessor energy level than on the power stroke. In the alternate embodiment of FIGURES 3A and 3B, wherein throughout the remainder of the specifica¬ tion identical or corresponding parts of another embodiment are designated by the same numeral as the first embodi¬ ment, only with a higher number of prime markings, a posi-

tive force is provided for the charging/exhaust stroke. Except then for structure relating to the provision of the positive return force, motor 10' is otherwise the same as motor 10. In this regard casing 30' includes a guide wall 80 for a guide member 82. Guide member 82 is attached to the end of shaft 40 opposite piston 34'. A spring 84 provides appropriate return force. Spring 84 functions in tension between wall 42' and guide member 82. Since guide member 82 is physically connected with piston 34', limit switch 70' can sense the travel of guide member 82 rather than the travel of piston 34' and still provide the appropriate switching control for valve 44". A shaft 86 is attached to guide member 82 and provides a mechanism for energy transfer to a use device. Although shaft 86 is shown connected to piston 34' through shaft 40' and guide member 82, it is understood that shaft 86 could as well be connected to the side of piston 34' opposite shaft 40' and extend through the wall of casing 30* to connect with a use device.

The preferred embodiment, motor 10'', is shown in FIGURES 4A and 4B. Motor 10'' is dual cylinder and provides energy conversion during each half cycle. In this regard, whereas motor 10 requires a particular geometry and working fluid condition to insure the charging/exhaust stroke and whereas motor 10' requires spring 84 to insure the charging/exhaust stroke, motor 10* ' has a shaft 110 con- • necting pistons 98 and 100 so that when one piston is being driven, the other piston is returning.

Motor 10'' includes first and second casings 88 and 90 with typically a common wall 92 separating first and second main chambers 94 and 96, respectively. First and second pistons 98 and 100 divide first and second main cham¬ bers 94 and 96 into first and second charging chambers 102

and 104 and first and second exhausting chambers 106 and 108, respectively. A main shaft 110 has opposite ends which attach to first and second pistons 98 and 100. Main shaft 110 extends through common wall 92 of first and second casings 88 and 90. A drive shaft 112 attaches to piston 98 and extends through a wall 114 of first casing 88. Wall 114 is generally opposite from common wall 92. It is understood that drive shaft 112 could as well be attached to piston 100 instead of piston 98 thereby extending in the opposite direc- tion as shown. Although not necessary, it is preferable that a dummy shaft 116 be attached to the opposite piston as shaft 112 is attached, in this case to piston 100. Dummy shaft 116 has a diameter U _Q the same as drive shaft-112 and thus, at equivalent locations of the pistons, dummy shaft 116 and drive shaft 112 reduce the volume of the respective chambers equally. Dummy shaft 116 can either extend through wall 118 opposite common wall 92 or telescope into piston 100 and main shaft 110. Since at least some of the working liquid changes phase to a vapor, the presence of dummy shaft 116, although important as indicated, is not necessary. If dummy shaft 116 were not present, the gaseous component of the working fluid would pressurize or depressurize somewhat more or less depending on the situation than would be the case for complete symmmetry. It is also understood that the various shafts and pistons include appropriate sealing mechanisms of a type known to those skilled in the art. It is further understood that although shaft 110 is shown as a linear ele¬ ment, that an equivalent structure need not be linear. Similarly, the cylindrical configuration of the pistons, shafts and chambers could as well take some other form.

Motor 10'' includes a six-way, two position valve 120. Valve 120 has a first position, as shown in FIGURE 4A,

placing charging chamber 102 in fluid communication with a source of pressurized saturated liquid via line 122 through valve 120 and line 124 and placing exhaust chamber 106 in fluid communication with a drain line 126 through valve 120 via line 128. At the same time, what was charging chamber 104 and exhaust chamber 108 (see FIGURE 4B) are placed in fluid communication with one another through valve 120 via lines 130 and 132 to form motor chamber 107. As shown in FXGURΞ 4B, each half of motor 10'' exchanges configurations with the other during the other half cycle of operation. That is, charging chamber 104 is placed in fluid com¬ munication with the source of pressurized saturated liquid via line 130, valve 120 and line 124. Exhaust chamber 108 is placed in fluid communication with drain line 126 through line 132 and valve 120. And, what was charging chamber 102 and exhaust chamber 106 are placed in fluid communication with one another through valve 120 via lines 122 and 128 to form motor chamber 109.

Just as with embodiment motor 10 shown in FIGURES 2A and 2B, motor 10'' includes limit switches 60'' and 70'' in electrical communication via lines 62'' and 74'' with solenoids 64'' and 72'', respectively. The switches and solenoids are also wired to a source in a similar fashion via lines 66'* and 68' ' for the one set and lines 76'' and 78'* for the other. Limit switch 60'' senses the end of the charging stroke of piston 98, which is also the end of the power stroke of piston 100, while limit switch 70*' senses the end of the charging stroke of piston 100, which is the end of the power stroke of piston 98. In this regard, it is noted that it is preferable for the pistons of each of the various embodiments to travel to very near the end walls of the various chambers thereby substantially emptying a par-

ticular chamber during a particular stroke.

System Operation A.motor, or heat engine, withdraws energy from a high temperature source, does work, and rejects the remainder of the energy to a low temperature sink. A heat pump opera¬ tes in reverse. It extracts energy from a low temperature source, adds work, and rejects the work energy plus low tem¬ perature energy to a high temperature sink. The amount of work available or required in either case is limited by the first and second laws of thermodynamics.

A mixed-phase motor in accordance with the present invention extracts flow work and expansion energy from a high pressure, high temperature saturated or slightly subcooled liquid. Pressure and temperature are reduced, and the extracted energy is returned as linear shaft work. As indi¬ cated hereinbefore, a mixed-phase motor as a result can be substituted for a fluid control valve so as to return as shaft work some of the energy otherwise lost through the valve. Shaft work can be linked to any of several useful devices, such as a piston pump, a compressor, etc.

The term "high" is understood to be relative to a related lower pressure or temperature. A "saturated" liquid will begin to form vapor if any additional heat is added at a constant pressure. A "subcooled" liquid will take some quan- tity of heat, rising in temperature before beginning to form vapor, at which point the liquid becomes saturated and then begins to form vapor.

A mixed-phase motor and a typical system in which it can advantageously function, as shown in FIGURE 1, is better understood with reference to typical thermodynamic phase diagrams as shown in FIGURES 5-7. FIGURE 5 shows a graph of temperature versus entropy. Entropy is a measure of

the orderliness of a substance. FIGURE 6 shows a graph of pressure versus enthalpy. Enthalpy is a measure of the energy of a substance contained in both its pressure and tem¬ perature. Entropy and enthalpy typically have meaning when 5 they are used to compare two states. Typically, the final enthalpy of a substance is subtracted from its initial enthalpy to give a measure of whether heat or work have been added or subtracted. Likewise, the initial and final entro¬ pies of a substance may be compared as a measure of how 0 effectively the potential to do work has been employed.

An ideal valve is a constant enthalpy, or isenthalpic, device. The enthalpy of a substance on the high pressure side of the valve is the same as the enthalpy of the substance on the low pressure side in the case of an ideal 5 valve. An ideal motor is a constant entropy, or isentropic device. A motor which expands a substance isentropically while extracting work (as in the case of a piston enlarging a chamber conveying force to a crank) is extracting the most amount of work theoretically available in that substance. An -0 ideal mixed-phase motor (if that were possible), would extract work isentropically where there likely once was an isenthalpic valve-

FIGURE 5 shows the thermodynamic cycle for a refri¬ gerant with respect to the system of FIGURE 1. FIGURE 5 is -5 shown in terms of temperature (T) ^' versus entropy (S). Points 1 through 5V in FIGURE 1 correspond to the T-S states of points 1-5V in FIGURE 5. At point 1, T and S are high. The vapor is somewhat "superheated", meaning that heat removal lowers the temperature of the vapor slightly before it begins 0 to condense and form liquid. Point 2 represents where the vapor begins to condense. Condensation at constant pressure is an isothermal process which is represented by the straight

horizontal line between points 2 and 3. Fully condensed refrigerant then passes through mixed-phase motor 10. If an ideal valve were used in the system instead of mixed-phase motor 10, the state of the refrigerant after passing through such valve would be 4h. Point 4s shows the state of the refrigerant after passing through a perfect mixed-phase motor. Complete evaporation with an evaporator leads to point 5V. Assuming a single working fluid, like water, the vapor is then compressed back to point 1 from point 5v. Many thermodynanic charts of property X versus pro¬ perty Y have a characteristic dome. FIGURES 5-7 show such a dome. The state of a substance can be conclusively deter¬ mined by considering a horizontal line which starts at the left vertical margin of one of the charts, passes through the dome, and continues toward the right out of the dome. States along the line to the left of the dome are subcooled liquid. The point where the line contacts the left side of the dome is the point where vapor is just about to form. As the line proceeds through the dome, more and more vapor is generated until the right side of the dome is reached. At that point, all the substance is vapor. From that point to the right, the substance is all superheated vapor.

If a dome is drawn correctly, the mass percentage of vapor and liquid for the mixture represented by points within the dome can be calculated. Looking at FIGURE 5, for example, point 5L is all liquid at temperature T^ and entropy S5L* Point 5V is all vapor. Point 4g represents a vapor/liquid mixture wherein after passing through a mixed phase motor, the quality, X, of the mixture can be expressed _a s a mass percentage of vapor in the vapor/liquid mixture by the following relationship: ^s 4s - S _5L

X = ^s 5v ~ S _5L

On reviewing this relationship, it is apparent from FIGURE 5 that that an isentropic expansion through a valve leading to point 4ft would yield more vapor than is the case for fluid expansion through a mixed-phase motor. Intuitively, it is reasonable to expect that energy wasted producing vapor on passing through a valve is harnessed by a mixed-phase motor as useful work.

It is understood, of course, that real world con¬ ditions result in inefficiencies. Even the best designed mixed-phase motor will increase the entropy of the refri¬ gerant. Consequently, point 4 _a ^{is fche} actual entropy of the fluid which leaves a mixed-phase motor.

Isothermal processes can use the formula Q = T x d(S). That is, the quantity of heat transferred is equal to the temperature of the process times the entropy change. In the evaporator, the entropy change is the difference between a mixture in one of states 4 and state 5V, where all the fluid has been vaporized. Area C then is equal to T(S5v-S ₄ ^) for an isentropic valve. Area C represents "no cost" energy transferred into the system of FIGURE 1 from the environment. Area B represents the additional energy which would be trans¬ ferred into the system due to the use of a mixed-phase motor. In other words, a mixed-phase motor extracts work, resulting in a downstream mixture that has more liquid and- less vapor. _ It is the liquid which is vaporized by the evaporator.

Therefore, more heat is drawn by the evaporator of the refri¬ geration system in order to evaporate the additional liquid. That amount of additional heat energy is equal to area B (in an ideal device). The amount of work available to the mixed-phase motor may be determined from FIGURE 6, a pressure versus enthalpy diagram. Expansion of refrigerant through an isentropic valve results in state ^. In realty, the

enthalpy will decrease slightly as it passes through the valve, resulting in state 4ft _a . State 4 _S is the enthalpy state at pressure P _L for refrigerant passing through an isentropic mixed-phase motor. State 4 _sa is for a less than ideal mixed-phase motor.

The theoretic maximum amount of work a mixed phase motor can produce per pound of refrigerant passing through is equal to the difference between the enthalpy at state 3 and at state 4 _S . The power produced is the enthalpy difference times the mass flow rate. For a real device, available power is as follows:

Power = ( 4h - h _4sa ) x M Knowing the available energy, it is then possible to deter¬ mine whether the mixed-phase motor can produce sufficient power for the particular application or whether it needs to be assisted by an additional standard motor.

A pressure versus specific volume chart is shown in FIGURE 7. By knowing the specific volume of refrigerant at states 3 and 4, an appropriate design for a mixed-phase motor can be determined. In this regard, the temperature, and therefore the pressure of refrigerant condensing or eva¬ porating between points 2 and 3 and between points 4. and 5 is set by the temperature of the appropriate heat sink or heat source. The range of temperatures expected during a fluid cycle is ordinarily known to a designer. When a design tem¬ perature is selected, the specific volume for the vapor/liquid mixture exhausting from the mixed-phase motor" becomes fixed at point V4s. The temperature and pressure of the fluid exiting the condensor fixes the specific volume of fluid entering the mixed phase motor at point V3.

In the most general case, the necessary dimensions for a mixed-phase motor are shown in FIGURE 4B. Since motor

10'* is a reciprocating device, it must have symmetry. That is, for the two sides to operate with 180 degree phase shift, they must be dimensionally identical. Since work is drawn off through a shaft and since that shaft occupies volume associated with motion chamber 106, a "dummy shaft" 116 of identical diameter is provided for motion chamber 108. As indicated hereinbefore, the dummy shaft may extend out of the device, as shown, where it might be attached to another use device, or it may extend into the device in a telescoping fashion (not shown). In any case, due to symmetry, dτ_ equals d ₄ and d equals d3- Shafts 112 and 116 have diameters of dg. By considering the volume of the refrigerant solution at the end of each stroke, the following relationship is develo¬ ped:

2 _

<*1 *2 ^'

dχ ² - d ₀ ² ^4s

Where V3 is a specific volume of liquid entering the mixed- phase motor and V42 is a specific volume of liquid/vapor mix¬ ture exiting the mixed-phase motor, and the diameters are as defined with respect to FIGURE 4B considering the symmetries indicated hereinbefore. In addition, it is noted that the relationship is also appropriate for motors 10 and 10' where do is zero.

With respect to motors 10 and 10' , it is necessary to determine whether an additional force such as spring 84 is necessary to accomplish the charging/exhaust stroke. Forces on each side of piston 34 or 34' are compared and when the following relationship is true, no spring is required:

With respect to all of the embodiments, it is noted that the length of piston stroke is a matter of engineering design and can be selected as desired. It is also noted that many liquid solutions may be used as working fluids.

With respect to the particular operation of motor 10, assuming the pressure ratio and diameter ratio of the chamber size to the shaft size satisfies the relationship discussed hereinbefore, piston 34 will travel through a charging/exhaust stroke when valve 44 is in its first posi¬ tion. When valve 44 is in its first position, pressurized liquid flows to charging chamber 36 and hydraulically forces piston 34 in a charging stroke thereby exhausting liquid and vapor from exhaust chamber 38 to drain port 54. Piston 34 travels until it is sensed by switch 60. At that point, solenoid 64 causes valve 44 to move to its second position. Charging chamber 36 and exhaust chamber 38 are then placed in fluid communication with one another through valve 44 to form motor chamber 39. The saturated liquid expands and forces piston 34 through a power stroke. When piston 34 is sensed by switch 70, solenoid 72 causes valve 44 to move again to its first position to repeat the motor cycle. The recipro- eating motion is transferred as mechanical energy to a use device through shaft 40.

Motor 10' functions similarly except spring 84 pulls in tension against guide 82 during a power stroke so as to insure a return stroke of piston 34' when valve 44' has moved to its second position. Also, it is noted that switch 70' may sense the end of the power stroke by sensing guide 82 instead of piston 34'.

Motor 12'' functions similarly except it has dual elements so that one side or the other of the motor is always in a power stroke. That is, when valve 120 is in a first position, pressurized, saturated liquid flows to charging chamber 102 and moves piston 98 in a charging/exhaust stroke. Liquid and vaporized fluid exhausts from exhaust chamber 106 to a drain line 126. The other side of motor 10' ' has what was charging chamber 104 and exhaust chamber 108 in fluid communication with one another through valve 120 to form motor chamber 107, and piston 100 moves in a power stroke. Thus, since piston 98 is connected with piston 100 by shaft 110, piston 98 is moved in a charging/exhaust stroke as piston 98 moves through its power stroke. When switch 60'' senses piston 98, valve 120 is moved by the action of sole- noid 64' ' to its second position. Pressurized, saturated liquid is now in fluid communication with charging chamber 104 forces piston 100 in a charging/exhaust stroke.. Liquid and vapor fluid mixture is exhausted to drain line 126 through valve 120. What was charging chamber 102 and exhaust chamber 106 are in fluid communication with one another through valve 120 forming a single motor chamber 109. As piston 98 moves through its power stroke, piston 100 is moved through its charging/exhaust stroke. When switch 70' ' senses piston 100 at the end of its power stroke, solenoid 72''.. functions to move valve 120 back to its first position so that the motor continues to cycle. Reciprocating mechanical energy is transferred to a use device with drive shaft 112 which is attached to piston 98. Energy may also be delivered to a use device with dummy shaft 116 attached to piston 100. Usually, however, dummy shaft 116 simply functions to reduce the volume exhaust chamber 108 in a fashion similar to the volume reduction of exhaust chamber 108 as a result of shaft

112.

Thus, the mixed-phase motor of the present inven¬ tion has been described in the form of various embodiments. Furthermore, the function of the motor has been related to the thermodynamics of a typical working fluid. It is understood, however, that the mixed-phase motor is conceptual and that numerous equivalents are possible. Consequently, any changes made from the disclosure as presented, especially in matters of design, shape, size and arrangement of parts to the full extent extended by the general meaning of the terms in which the appended claims are expressed, are within the principle of the invention.