TECHNICAL FIELD

[0001] This invention relates to rotary vane engine generators that convert heat energy to electrical energy.

[0004] There have been numerous attempts to build rotary vane engine, and there exist a large number of patents of various designs, however, to this day, not one of the many proposed constructions has been successful in practical testing.

[0005] In a rotary vane engine, to realize the internal combustion cycles it is necessary to ensure coordinated rotation of the shafts. The main cause of failure in all known variants of rotary vane engine construction is that they employ mechanical linkages to coordinate shaft rotation; none of them are sufficiently reliable and capable of long-term operation. Components in these mechanical linkages experience alternating shock loadings, which quickly lead to their destruction.

[0006] An example of a known rotary vane engine invention is patent RU2237817, which proposes attaching reversible electrical machines (REMs) onto the shafts of the engine, but, to keep the trailing vane from rotating backwards, proposes a mechanical linkage (a locking device or ratchet) which makes the device practically unusable due to unavoidable quick wear and tear of this mechanical part. Other designs, for example WO 2008/081212 A1, also propose to install REMs onto shafts, and also propose mechanical stopper devices to ensure motion of the rotor in one direction only.

 TECHNICAL PROBLEM

[0007] The technical task is to find a simple, and reliable method of coordinating the rotation of the shafts of a rotary vane engine, without employing mechanical linkages to affect the rotation of the shafts.

 SOLUTION TO PROBLEM

[0008] In the disclosed method and device, coordinated rotation of shafts of a rotary vane engine is achieved through the application of accelerating, and decelerating torques applied to the shafts from either one or two REMs; no mechanical linkages are used to affect the nature of rotation of the shafts. A commutator controls the current supplied to the REM(s). The commutator is in turn controlled by a computing device, which receives shaft position information from sensors.

 BRIEF DESCRIPTION OF DRAWINGS

 [0010] FIG. 1 depicts an embodiment of the device with one reversible electrical machine (REM) attached to one of the shafts.

                                                                                     1 - position sensor
                                                                                     2 - flywheel
  3 - shaft 1
  4 - cylindrical casing
  5 - oin (opening for the intake of gases)
  6 - ignition device, which can either be
      a spark plug or an injector
  7 - one of vanes attached to shaft 1
  8 - one of vanes attached to shaft 2
  9 - shaft 2
 10 - REM
 11 - position sensor





 [0011] FIG. 2 depicts an embodiment of the device with two reversible electrical machines attached to each shaft.
                                                                                           1 - position sensor
                                                                                           2 - REM
    3 - shaft 1
    4 - cylindrical casing
    5 - oin (opening for the intake of gases)
    6 - ignition device, which can either be
         a spark plug or an injection
    7 - one of vanes attached to shaft 1
    8 - one of vanes attached to shaft 2
    9 - shaft 2
   10 - REM
   11 - position sensor








 [0012] FIG. 3 is a diagram of the simplest version of the main unit of a rotary vane engine containing four identical vanes, two vanes to each shaft.

     θ  -   angular size of a vane
     d  -   width of a vane
     R1 - radius of shafts
     R2 - radius of vanes.
     Vanes attached to shaft 1 are marked by a single black dot,
     vanes attached to shaft 2 are marked by two black dots




[0013] FIG. 4 depicts positions of the vanes at the beginning of the first stroke

     oex, oin - openings for the exhaust and intake
     ig - ignition device
     c1, c2, c3, c4 - chambers between vanes
     k0 - origin of coordinates
     k1, k2 - coordinates of shaft 1 and shaft 2
     bs - bisector of the angle between the shafts
     φ1, φ2 - angular sizes of chambers c1 and c2



[0014] FIG. 5 depicts an intermediate position of the vanes between the beginning and end of the first stroke

     in chamber c1 the power stroke is carried out
     in chamber c2 the compression stroke is carried out
     in chamber c3 the intake stroke is carried out
     in chamber c4 the exhaust stroke is carried out






[0015] FIG. 6 depicts a position of the vanes at the end of the first stroke, which is also the beginning of the second stroke












 [0016] FIG. 7 depicts an intermediate position of the vanes between the beginning and end of the second stroke.
     in chamber c2 the power stroke is carried out
     in chamber c3 the compression stroke is carried out
     in chamber c4 the intake stroke is carried out
     in chamber c1 the exhaust stroke is carried out






[0017] FIG. 8 depicts positions of the vanes at the end of the second stroke.










[0018] FIG. 9 plots the speed of the bisector (dashed line) and the angle between the shafts (continuous line) versus time, of an embodiment with one REM.












[0019] FIG. 10 plots the speed of shaft 1 relative to the bisector (continuous line) and speed of shaft 2 relative to the bisector (dashed line) versus time of an embodiment with one REM












[0020] FIG. 11 plots the speed of the bisector (dashed line), and the angle between the shafts (continuous line) versus time of an embodiment with two REMs












[0021] FIG. 12 plots the speed of shaft 1 relative to the bisector (continuous line) and speed of shaft 2 relative to the bisector (dashed line) versus time of an embodiment with two REMs.













DESCRIPTION OF EMBODIMENTS

[0022] General forms of a rotary vane engine with one and two reversible electrical machines are depicted in FIG. 1 and FIG. 2, wherein two vanes are attached to the first and second shaft of the engine in such a way so that vanes of shaft 1 alternate with vanes of shaft 2. As the angle between the shafts changes, the volume of the chambers between the vanes also changes. FIG. 1 depicts a rotary vane engine with a REM 10 attached to shaft 2, and a flywheel 2 attached to shaft 1. FIG. 2 depicts a rotary vane engine with two REMs, 2 and 10 attached to shaft 1 and shaft 2 respectively.

[0023] In both FIG. 1 and FIG. 2, vanes are enclosed within a cylindrical casing 4, which has an opening for the intake of gases 5 and a second opening (not shown) for the exhaust of gases on the other side of the casing. On the side of the cylindrical casing 4 there is a device for ignition 6 which can either be a spark plug or an injection nozzle that sprays fuel into the hot air which is at a sufficiently high temperature for ignition to occur. Position sensors 1 and 11 are fixed to the shafts 1 and 2 respectively and are used to inform the computing device of the positions of the shafts. The electronic commutator controls electrical currents in REM 10 FIG. 1, and REM 2 and REM 10 in FIG. 2. The computing device controls the electronic commutator. The stators of REM 10 in FIG. 1 and REMs 2 and 10 in FIG. 2 and the cylindrical casing 4 are fixed to a common stationary base (not shown). The energy storage serves as a buffer for temporary storage of electrical energy for powering the REM(s), and for offering continuous energy flow to the electrical load. The electrical load is consumer of all energy produced by the REM(s) during their continuous, uniform operation.

[0024] FIG. 3 depicts an example embodiment of the main unit of the simplest version of a rotary vane engine containing four identical vanes, with pairs of vanes attached to each shaft. θ is angular size of a vane, d is the width of a vane, R1 is the radius of shafts, and R2 is the radius of vanes.

[0025] FIG. 4, FIG. 5, FIG. 6, FIG. 7 and FIG. 8 depict five consecutive positions of the vanes over two strokes. We use these figures to briefly summarize the coordinated rotation of vanes to execute the  strokes of the internal combustion cycle. The vanes create between them chambers of variable volume: c1, c2, c3, and c4. The origin of the coordinate of the shafts is the horizontal ray directed to the right, labeled k0 in figures 4 to 8. The coordinate of shaft 1, k1, is measured as the angle between the surface of the vane attached to shaft 1 which bounds chamber c1 and ray k0. Similarly, the coordinate of shaft 2, k2, is measured as the angle between the surface of the vane attached to shaft 2 which bounds chamber c1 and ray k0.

[0026] In FIG. 4 the angle between k1 (starting coordinate of shaft 1) and k0 is considered positive, as the direction from k0 to k1 is anti-clockwise, whereas the angle between k0 and k2 (starting coordinate of shaft 2) is negative. This coordinate choice for shafts is convenient because the difference in coordinates of the two shafts (k1 – k2) gives the angular size of the chamber c1. The bisector bs of the angle between the two shafts is a ray starting from the center of rotation marked by a circle on its end. The coordinate of the bisector is the arithmetic mean of the coordinates of the two shafts (k1 + k2)/2. The ignition device ig has a constant coordinate k0. Intake and exhaust openings are labeled as oin and oex respectively.

[0027] During the first stroke, from the instant of ignition of the fuel mixture in chamber c1, this chamber increases its volume as it performs the power stroke. Chamber c2 contracts compressing the fuel mixture as it performs the compression stroke. In chamber c3 the intake stroke is carried out, and in chamber c4 the exhaust stroke is carried out. In short, during the first stroke, chamber c1 is the power chamber, c2 is the compression chamber, c3 is the intake chamber, and c4 is the exhaust chamber. During this stroke, shaft 1 is leading, and shaft 2 is trailing.

[0028] Passing through an intermediate position shown in FIG. 5, at the end of the first stroke the vanes come to a position shown in FIG. 6. In this position chamber c1 has expanded to the angle φ2, shaft 1 has turned through an angle θ + φ2, shaft 2 has turned through an angle θ + φ1, and the bisector bs of the angle between the shafts has rotated through 90°.

[0029] A fresh portion of fuel mixture is now compressed in chamber c2, ignition of this fuel mixture begins the second stroke. During the second stroke chamber c2 is where the power stroke is carried out; chamber c3 is where the compression stroke is carried out; chamber c4 is where the intake stroke is carried out; and chamber c1 is where the exhaust stroke is carried out.

[0030] Similarly to the first stroke, during the second stroke the vanes pass through an intermediate position shown in FIG. 7, with their final position at the end of the second stroke shown in FIG. 8. FIG. 8 depicts that the exhaust stroke has ended in chamber c1, and in chambers c2, c3 and c4 the power, compression, and intake strokes have come to completion. During the second stroke, shaft 1 rotated through an angle θ + φ1, shaft 2 rotated through an angle θ + φ2, the angular width of chamber c1 becomes equal to φ1, and the bisector bs of the angle between the shafts has rotated through another 90°. During this stroke, shaft 1 is trailing, and shaft 2 is leading. As the positions of the vanes shown in FIG. 8 are equivalent to the positions of the vanes shown in FIG. 4, the time taken to perform these two strokes is considered the period of operation of the device.

[0031] In order for the above-described changes in the angles of the chambers, as well as the position of the chambers relative to the cylindrical casing to occur, rotation of the shafts should be coordinated. Below we present considerations underlying the disclosed method to achieve the required coordination using REM(s), in the simplest case, when the moments of inertia of the shafts are equal.

[0032] Let the pressures of gases in chambers c1, c2, c3 and c4 be equal to p1, p2, p3 and p4 respectively. Then, the torques acting on shaft 1 τ1 and shaft 2 τ2 due to these pressures are equal to:
τ1=(p1-p2+p3-p4)SL
τ2=(-p1+p2-p3+p4)SL
or,
τ2 = -τ1            (1)
where the surface area of a vane S=d(R2-R1), and lever arm L=(R1+R2)/2, see FIG. 3.

[0033] From the above equation, we see that the torques applied by the gases to shaft 1 and shaft 2 are always equal in magnitude and opposite in direction. This means that if the gases induce acceleration in one shaft, the same acceleration, but in the opposite direction is induced in the other shaft. Consequently, the bisector of the angle between the shafts cannot obtain acceleration due to pressure applied by gases onto the vanes; the motion of the bisector is not dependent on interacting forces between the shafts. Only external torques (in our case torques applied by the REM(s)) whose algebraic sum is not equal to zero can cause the bisector of the angle between the shafts to accelerate.

[0034] Let us assume that in the position shown in FIG. 4 the initial speed of both shafts is equal to zero, the speed of the bisector ωb is also equal to zero, ignition of the compressed fuel mixture occurs in chamber c1, and external torques are applied to the shafts by the REMs. Shaft 2 experiences an external torque τ0 (in the anti-clockwise direction) from its REM, and shaft 1 experiences an external torque -τ0 (in the clockwise direction) from its REM. Assume also, that in the remaining three chambers the pressures of gases are atmospheric.

[0035] From this unstable state the system will begin non-harmonic periodic oscillation. Much like a spring pendulum, the system will be in the process of transferring internal energy of the gases to kinetic energy of the shafts, and back again. The period of this oscillation of the shafts depends on initial pressures of the gases, elastic properties of the gases, moments of inertia of the shafts, and magnitudes of the externally applied torques. During these oscillations, the coordinate of the bisector will experience zero acceleration.

[0036] If, at the starting moment the angular speed of bisector ωb is not equal to zero, then the shafts will execute the same oscillations but relative to a rotating bisector. The rotating motion of the shafts will be the sum of two independent motions: oscillation of the shafts relative to the bisector, and uniform rotation of the bisector. If the initial speed of the bisector ω0 is such that it rotates 90° in the time it takes for the chamber c1 to expand its angle from φ1 to φ2, then the shafts will move from the positions shown in FIG. 4, to the positions shown in FIG. 6, which corresponds to the end of the first stroke. At the end of this first stroke, chamber c1 is replaced by chamber c2, which contains a newly compressed fuel mixture, and the system is ready to execute another stroke.

[0037] The vanes, with elastic gases between them form an oscillatory system. This property is exploited in the disclosed method and devices, utilizing the REM(s) to influence the period and amplitude of these oscillations, as well as the angle of rotation of the bisector during each stroke.

[0038] During continuous, uniform operation of the rotary vane engine, the processes occurring during each period should repeat themselves, and the speeds of the shafts at the end of each period should be equal to the speeds of the shafts at the start of each period. If during a period the gases produced a given quantity of work by transferring energy to the shafts, then during this same period, an equivalent quantity of work should be done by the shafts against external torques applied by the REM(s). This means, that during a period, the sum of work done by the gases and work done by external torques is equal to zero, only then will the shafts neither loose nor gain kinetic energy, i.e. not increase or decrease their speed. The bisector of the angle between the shafts should rotate through 90° with every stroke, and the angle between the shafts during a stroke should either increase from φ1 to φ2, or decrease from φ2 to φ1.

[0039] In the following examples we will show how these conditions are met for a rotary vane engine with one REM, and with a REM on each shaft. In these examples, the following assumptions are made:
- thermal and friction losses are negligible,
- compression and expansion processes of the gases are polytropic,
- work expended to intake and expel gases is negligible,
- torques exerted by REMs on the shafts during each stroke are constant.

[0040] In FIG. 3 numerical values are equal to:
- radius of shafts, R1 = 41.5 mm,
- radius of vanes, R2 = 124.6 mm,
- width of vanes, d = 83.1 mm,
- angular size of vanes, θ = 40°,
- sum of angular sizes of adjacent chambers, ssa = π − 2θ = 100°,
- moment of inertia of shaft 1 and shaft 2, J1=J2 = 0.215 kg⋅m2.

[0041] Below are the thermodynamic parameters used in our calculations:
- compression ratio, CR = 9,
- sum of volumes of adjacent chambers, Va= 1 L,
- polytropic compression index, nc = 1.3,
- polytropic expansion index, ne = 1.3,
- temperature increase at ignition of stoichiometric mixture: ΔT = 2000 K,
- initial temperature of compression: T2 = 300 K,
- initial pressure of compression: P2 = 100 kPa.

[0042] Using the above values, we calculate:
- angular size of compression chamber after compression, φ1 = 10°,
- angular size of compression chamber before compression, φ2 = 90°,
- volume of gas at start of compression, V2 = 0.9 L,
- volume of gas at end of compression, V1 = 0.1 L,
- work expended in compression of the fuel mixture, from a pressure P2 and volume V2 to a volume V1 is:

- at the end of this compression, pressure of the fuel mixture will increase to:

- and temperature will increase to:

- upon ignition of the compressed fuel mixture, the temperature inside the chamber will increase to:


- and pressure inside the compression chamber will increase to:

- work done by the gas during expansion from a pressure PF and volume V1, to a volume V2 is:
 
- total work done during the compression-expansion process is:

EXAMPLE 1

[0043] Example 1 describes the continuous, uniform operation of a rotary vane engine generator with one REM on one shaft, see FIG. 1. The mode of the REM is switched between motor and generator by the commutator. The REM attached to shaft 2 when operating as a motor increases the speed of rotation of shaft 2 consuming electrical energy, and decreases the speed of rotation of shaft 2 when operating as a generator.

[0044] As indicated earlier [0038], during a period of operation the energy of the shafts should not change, which is observed when the sum of work done by gases and externally applied torques during a period is equal to zero. During the first stroke the REM applies an accelerating torque τ0 to shaft 2, which adds energy to the shafts, performing work equal to τ0(θ + φ1). During the second stroke the REM applies a decelerating torque -τ0, which performs work equal to -τ0 (θ + φ2) . The total work of these external moments during two strokes (period) is equal to:

The work of the gases during these two strokes is 2WT. To satisfy the necessary condition that the sum of work done by gases and externally applied torques during a period is equal to zero, we write:

from which we calculate the value of τ0:

[0045] Provided that an external torque τ0 is applied to shaft 2, and assuming that the initial speeds of the shafts and the bisector are equal to zero, we utilize the method of iteration to determine the time it takes for the ignited mixture to expand from volume V1 to V2, that is, the duration of a stroke tS. We find tS equal to 21.53 ms. The angle β of rotation of the bisector is found by:

Using these values, we calculate the initial speed of the bisector ω0 at which the angle of rotation of the bisector will be 90° during a stroke:

[0046] These calculations provide us with a description of the continuous, uniform operation of the rotary vane engine generator with one REM on shaft 2. Using the same iterative method we calculate the motion of the shafts with τ0 applied, and having an initial speed ω0. FIG. 9 plots the speed of the bisector ωb (dashed line), and the angle between the shafts α12 (continuous line) as a function of time over four strokes. FIG. 10 plots the speed of shaft 1 relative to the bisector ω1b (continuous line) and speed of shaft 2 relative to the bisector ω2b (dashed line) as a function of time over four strokes. Table 1 lists values of the quantities in FIG.s 9 and 10 during four strokes divided into twenty equal time intervals. From table 1 we see that when the coordinate of the bisector takes on the values of 90°, 180°, 270° and 360°, the angle between the shafts α12 becomes equal to 90°, 10°, 90° and 10° respectively, which confirms the correct mutual rotation of the shafts, and their correct rotation relative to the static cylindrical casing.

TABLE 1

[0047] In summary, the parameters of this embodiment of rotary vane engine generator with one REM are:
- Power delivered to load: 45 kW (61 HP) at 697 RPM,
- Engine displacement: 3.2 L,
- Power of reversible electrical machine: 101 kW. 

EXAMPLE 2

[0048] Example 2: describes the continuous, uniform operation of a rotary vane engine generator with one REM on shaft 1, and one REM on shaft 2, FIG. 2. The mode of both REMs is switched between motor and generator by the commutator. When an REM is operating as a motor it causes an increase in speed of rotation of the attached shaft consuming electrical energy, and when operating as a generator decreasing the speed of rotation of the shaft to which it is attached.

[0049] The numerical values provided for the dimensions of the main unit of a rotary vane engine generator are the same for this example, as are the thermodynamic characteristics.

[0050] During the first stroke REM 10 (FIG. 2) applies an accelerating moment τ0 to shaft 2 (trailing shaft) which performs work equal to τ0(θ + φ1), whereas, shaft 1 (leading shaft) experiences a decelerating moment -τ0 from REM 2 (FIG. 2), which performs work equal to -τ0(θ + φ2). During the second stroke, REM 10 applies a decelerating moment -τ0 to shaft 2 (now the leading shaft) which performs work equal to -τ0(θ + φ2) and shaft 1 (now the trailing shaft) experiences an accelerating moment τ0 from REM 2, which performs work equal to τ0(θ + φ1). The work done by both REMs during the first stroke is equal to:

The work done by both REMs during the second stroke is the same:

The work of gases during a period is 2WT. Writing the condition for the sum of works of gases and external forces acting on the shafts to be equal to zero:

we calculate the value of τ0:

[0051] Provided that an external torque τ0 is applied to shaft 2, an external torque -τ0 is applied to shaft 1, and assuming that the initial speeds of the shafts are equal to zero, we utilize the method of iteration to calculate the time it takes for the ignited mixture to expand from V1 to V2, that is, the duration of a stroke tS. We find tS equal to 21.53 ms. The angle of rotation of the bisector during the stroke is equal to zero, as the sum of external moments from both REMs at every point in time is equal to zero. The initial speed of the bisector for the continuous, uniform operation of the rotary vane engine generator with two REMs, where the bisector rotates through 90° during a stroke is:

 [0052] These calculations provide us with a description of the continuous, uniform operation of our disclosed rotary vane engine generator with two REMs. Using the same iterative method we calculate the motion of the shafts with external torques applied to both shafts, and having an initial speed ω0. FIG. 11 plots the speed of the bisector ωb (dashed line), and the angle between the shafts α12 (continuous line) as a function of time for four strokes. FIG. 12 plots the speed of shaft 1 relative to the bisector ω1b (continuous line) and speed of shaft 2 relative to the bisector ω2b (dashed line) as a function of time for four strokes. Table 2 lists values of the quantities in FIGs. 11 and 12 during four strokes divided into twenty equal time intervals. From table 2 we see that when the coordinate of the bisector takes on values of 90°, 180°, 270° and 360°, the angle between the shafts α12 becomes equal to 90°, 10°, 90° and 10° respectively, which confirms the correct mutual rotation of the shafts, and their correct rotation relative to the static cylindrical casing.

TABLE 2

[0053] In summary, the parameters of this embodiment of the rotary vane engine generator with two REMs are:
- Power delivered to load: 45 kW (61 HP) at 697 RPM,
- Engine displacement: 3.2 L,
- Power of reversible electrical machine: 51 kW. 

[0054] In both embodiments of the rotary vane engine generator with either one or two REM(s) the necessary coordination of the shafts is achieved with the REM(s) applying external torques. The function of the REM(s) is reduced to periodic removal of the energy generated by the gases, and it appears to be sufficient to reach necessary coordination of the shafts. In both examples, position sensors were not used, and no mention of the control of the angles or speeds of the shafts by a computing device is made.

[0055] In any practical realization of the disclosed methods and devices, feedback and control of the REM(s) is of course a practical necessity as deviations from continuous, uniform operation are inevitable. In practice, monitoring the position of both shafts is necessary by sensors that will inform the computing device of any deviations from the expected operating state. A control system will act to compensate these deviations by applying necessary corrections to the torques of REM(s).