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THE FLYWHEEL ASSISTED ROTARY PULSE JET ENGINE

The Concept

n                  A new type of engine that can be used as a power plant for clean, efficient and ecologically aware transport and also for convenient, cost-effective, and dependable home power generation.

Importance of Conservation and the environment.

n      Today global warming and the environment are a major topic in the media.

n      Conservation of fuel, water and the environment is no longer a matter of individual choice but of collective necessity.

n      We at Green Initiative are concerned with the conservation of fuel.

How can we conserve fuel ?

n      Do we conserve fuel by switching off our engines at traffic lights ?

n      Unfortunately no, it is not so simple!

n      What we need are cars that give a minimum mileage of 150 Kms. a litre, and that is what Green Initiative is trying to do.

n      The same engine can be used to generate captive electrical power for households.

Inefficiency of the IC Piston Engine

§    The IC piston engine is one of the few really energy inefficient machines still in daily use by most of mankind.

§    A brief look at any other technology shows that rapid improvements have been made.

§    For instance the publishing industry, media and communications have all made quantum leaps in terms of efficiency. Yet car engines have remained unchanged since 1860 when Nicholaus Otto invented the first IC piston engine.

What is the reason for this inefficiency ?

n      The IC piston engine has certain inherent and fatal flaws.

n      These flaws are related to the fact that the IC piston engine is a reciprocating engine requiring linear to rotary conversion.

n      Further the mechanical linkages that are used in this linear to rotary conversion do not deliver force at the correct angle or length for maximum mechanical advantage. 

A New Engine Design is Needed !

n      We at Green Initiative have designed a completely new type of engine.

n      In this engine there are no cylinders, no pistons, no connecting rods, no cam shafts, no push rods and no crankshaft.

n      Practically the only thing that remains in common with the IC Piston Engine is the combustion Chamber and the idea of using fuel and compressed air.

n      Fuel used is CNG, LPG or petrol.

        The Rotary Pulse Jet Engine

Working of the Rotary Pulse Jet Engine.

n      As can be seen the Rotary Pulse Jet Engine has no cylinders , pistons, connecting rods or crankshaft.

n      It consists of a rotor with two opposed combustion chambers equipped with an inlet valve an outlet valve and an ignition device. The rotor is attached to a main shaft.

n      Compressed air and fuel  is introduced into the combustion chambers via a rotary union attached to the main shaft.

  A Picture of a  Rotary Union.


  A Rotary Union as used in Industry

As can be seen in the picture, the rotary union isolates inputs and outputs from the rotating movement of the cylinder.

  Rotary Union

Today Rotary Unions are available that can handle pressures of 15000 psi and rotational speeds of 10000 rpm. These are parameters far in excess of those needed by the Rotary Pulse Jet Engine.

Fuel Supply

n      The purpose of the Rotary Union is to isolate the supply of fuel and compressed air from the rotary movement of the main shaft.

n      Compressed air is stored externally in a pre-filled tank that is replenished as required from a small compressor attached to the main shaft.

n      Fuel is mixed into the stream of compressed air in a stoichiometrically correct ratio by a computerized device

Compression

The compressed air in the external tank yields a compression ratio of anything from 8 : 1 to 10 : 1 in the combustion chamber as preferences might dictate. For instance air compressed to 125 psi or 8.8 Kg/cm2. will yield a compression ratio of  8 : 1 when it enters the combustion chamber while air compressed to 150 psi or 10.5 Kg/cm2 will yield a compression ratio of 10 : 1 approx. in the combustion chamber.

Introduction of compressed fuel/air into the Combustion Chamber

n      The compressed air/fuel mixture is introduced into the combustion chambers through channels in the main shaft and then through similar shafts set into the rotor.

n      Once the compressed fuel/air mixture has been introduced into the combustion chamber the intake valve is closed and the combustion chamber is completely sealed.

Ignition

n      The compressed fuel/air mixture in the sealed combustion chamber is ignited causing the pressure to rise to 500 psi  (35 Kg/cm2)  and the temperature to rise to about 20000 C.

n      The outlet valve to a venturi is now opened and the hot gases of combustion are allowed to escape at velocity causing the rotor to turn in the opposite direction.

n      Fuel used can be CNG, LPG or petrol.

Advantages of the Rotary Pulse Jet Engine

n      A look at a picture of the Rotary Pulse Jet Engine makes it apparent that:

n      The lever arm through which force is exerted is about 18” ( 50 cms) long giving maximum mechanical advantage.  (i.e., technically if a force of 28 Lbsf (13Kgf )) is exerted on the lever arm it would result in a torque of 42 Lbs ft  ( 75 Nm) being generated at the main shaft.

n       Force is exerted at right angles and not through a continuously changing angle.

n      The Rotary Pulse Jet Engine is a pure rotary Engine.

n      The fact that the Rotary Pulse Jet Engine exerts force through a long lever arm at right angles and does this in a pure rotary output, gives it a tremendous mechanical advantage over the IC piston engine design.

n      The engine is superbly balanced. Force is exerted through a force Couple; both combustion chambers firing simultaneously and exerting   force on the lever arm, at right angles and in the same direction.Hence balance is achieved.

The importance of levers and the angle at which force is applied

§      It was Archimedes of ‘Eureka’ fame who once boasted : “Give me a lever that is long enough and I will move the world. “

§      There is a reason behind this boast. Take a lever that is 1 ft. long attached at one end to an axle, and exert a force at the other end at an angle of 900 of 1 lb and you will generate a torque of 1 ft lb.

§      Increase the length of the lever to 2 ft and the same 1lb force exerted on its end at right angles will result in a torque of 2 ft lbs being generated at the axle.

§      Increase the length of the lever to 10 ft and the same 1 lb force exerted on the end of the lever at right angles will result in a torque of 10 ft lbs being generated and so on.

§      A lever acts like a force multiplier OR vice-versa.

§      This is common sense as anyone who has used a spanner is aware.

§      However in the IC piston engine the length of the lever (the crank throw) used for linear to rotary conversion is very small, half the length of the stroke, if this were not the case the connecting rod would hit on the skirts of the cylinder as it moves up and down the cylinder, further the angle of attack of the connecting rod is constantly changing, which is another huge mechanical disadvantage.

 

Comparison of the IC Piston Engine and the Rotary Pulse Jet Engine

n      The Rotary Pulse Jet Engine needs only 20Kgf (44lbsf) to generate a torque of 100Nm, an IC piston engine needs more than 1650 Kgf on the piston head to generate the same amount of torque. In other words the RPJ needs to exert just 1/80th. of the force that an IC piston engine exerts to get the same result. 

n      Here is an example for an IC piston engine  that has a bore of 7.6cms and stroke of  7.6cms

Area of Piston head =  3.92   x  3.14 = 47.75 cm 2

      Pressure in Combustion chamber after ignition = 35 Kg/cm2

Therefore total force acting on piston head  =  35 x 47.75 = 1671.5 Kgf.

Length of lever in IC piston engine (crank throw) = 0.039m . Torque delivered = 0.039 x 1671.5 = 65Kgm Torque.

However, in order to gain maximum mechanical  advantage, force has   

to be delivered at 900 . In an IC  Piston engine the connecting rod    

delivers force at a continuously changing angle, not at 900 . Further as    

the  piston moves down the cylinder pressure drops, and  the  exhaust   

valve opens at 150 before BDC. All these factors contribute to a

reduction constant of 0.173. So final torque delivered = 0.173 x 65 =

11.2 Kgm of torque or 110 Nm. The manufacturers figure for

     maximum torque for this engine is  110Nm. At 4000 rpm.

{Converting these figures to pounds we have:

bore and stroke = 3” x 3” (i.e., 7.6cm x  7.6cm)

Pressure in combustion chamber after ignition = 500 psi (i.e., 35Kg/cm2.)

Area of piston head = 1.52  x 3.14 x 500 = 7.065sq ins.

Total pressure on piston head = 7.065 x 500 = 3532.5 lbsf

Torque generated =  length of lever (i.e., half of stroke) x force exerted = 0.125ft x 3532.5 = 441.6 ft lbs torque. Multiplied by inefficiency constant of 0.173 final torque = 76.4 ft lbs approx = 110 Nm approx. }

By Contrast the amount of force needed by the Rotary Pulse Jet Engine to generate a torque of 100 Nm is simply, the desired torque divided by the length of the lever arm. If the length of lever arm is 0.5m and the needed torque is 10Kgm (100Nm) then 10/0.5 = 20 Kgf.

It is significant that in an IC piston Engine the extremely short length  of the lever arm (crank throw) used for linear to rotary conversion and  the angle of attack of the connecting rod with the crankshaft result in an initial force of  1671 Kgf generating a  torque of just 11.2 Kgm. (110 Nm).

The above formula can be applied to any IC piston engine  to get a rough

idea of  the torque that it generates.

N.B. If the crank throw (lever arm) on the IC piston engine had been 1 ft. and the force  had been exerted at right angles then the torque generated from an exerted force of 3532 lbs on the piston head, would be closer to 3000  ft lbs than to 76 ft lbs.  It is something to think about.

   Torque And Power

§      In the automobile engineering world, there is some doubt as to the significance of torque. Torque is the motivating force in any engine i.e., it is the force available to rotate the main shaft.  In fact torque is a function of power and vice versa.  Power generated by a car engine  can be calculated from the following equation:

§      Power in kilowatts = Torque (Nm)  x   2 Pi   x  RPM  / 60000                         

§      OR

§      Horse Power  =        Torque (ft lbs,) x  2 Pi  x  RPM/ 33000

§      How the torque generated is used, depends upon the gearing and transmission. This can be designed to pull a heavy load slowly or to pull a lighter load at speed.

  The Rotary Pulse Jet Engine is a Reaction Engine!

 

 

 

 

 

 

 

 

 

 

 

 

n      The Rotary Pulse Jet is a reaction engine, it works on the principle of Newton’s Third Law: “For every action there is an equal and opposite reaction.”

n      The question on everyone’s mind is : “Will this system work ? Will it provide as much power as an IC piston engine ?”

n      The answer is that the engine will work because the subject has been extensively researched for over 60 years although no-one has previously thought of utilizing this principle in a car engine

  Equivalence

n      The principle on which the RPJ works is based on the recoilless gun and the Bazooka or LAW ( Light anti tank weapon) both of which were invented in the U.S.A more than sixty years ago and are still in service all over the world today.

  The Recoilless gun and the LAW.

n      With the introduction of tanks into warfare there arose the need for effective artillery that could be carried by one or two men.

n      The presence of recoil in conventional artillery pieces meant that the field guns had to be one or two tons in weight and were not easily transported.

n      It was discovered that recoil could be cancelled if an amount of ballast equal to the weight of the shell was ejected from the rear of the gun.

Newton’s Third Law.

n      This method of canceling recoil was in keeping with Newton’s Third Law.

n      By an extension of this Law it was found that recoil could also be cancelled if the gases of combustion in the gun were ejected at high velocity through the rear of the gun.

n      This is in keeping with the Conservation of momentum, i.e., the momentum of the mass x velocity of the shell was equal to the mass x velocity of the escaping gases.


Diagram of the working of a Recoilless Gun

Performance of the recoilless gun

The M18, 57mm. recoilless rifle  pictured here in action,

had a length of just 1.21m. weighed 20 Kg and fired a 2.4 Kg shell a distance of  3,913m or approx. 4 Kms.  The Bazooka had a much more limited range about 2000m. because the rocket had to fully fire within the confines of the short 1m length firing tube, if this was not the case the back blast could severely injury the soldier firing the weapon

The Bazooka

In a natural extension of this idea the propellant, instead of being put into the breech of the gun, was loaded inside the shell itself.

                                                                                                                                                                                                                                                             

Difference between the Rotary Pulse Jet Engine and the recoilless gun

 

 

n      The main difference between the Rotary Pulse Jet Engine and the recoilless gun or Bazooka, is that in the Rotary Pulse Jet Engine, combustion of the fuel (propellant) takes place in a fully sealed combustion chamber. This allows for a build up of pressure for a few milliseconds BEFORE the valve to the venturi is opened.

  n      In both the Bazooka and the recoilless gun combustion takes place with a venturi  that is left open to the outside, meaning that pressure is not allowed to build up.  This was necessary for obvious reasons.

  Principle of working of the Rotary Pulse Jet Engine  

§     The RPJ works on the same principle as the Bazooka or LAW (Light anti tank weapon), although using liquid fuel instead of solid propellant.

§     In order to gain the same muzzle velocity as a conventional cannon these recoilless guns had to use three times the amount of  propellant used in conventional cannon. This means that the combustion chambers in the  RPJ will have to use three times the fuel of a normal IC piston engine. (At this point this is speculation until tests are carried out. )

Excess power

n      Because of the mechanical advantages that it enjoys, the RPJ can theoretically generate about 100 times the power of an IC piston engine.

n      The question is what do we do with this tremendous amount of power?

n      Do we use it to go faster?

n      The answer is no, the tremendous power generated by the RPJ is stored in a flywheel and then bled out as required !

The gyro bus

n      The flywheel is an ideal short term energy storage device; below 20 minutes.

n      This fact was utilised in the construction of a gyro bus by Oerlikon Ltd., This was a bus that was powered solely by a flywheel! It was in service for more than 8 years at three locations around the globe including Switzerland, Belgium and the Belgian Congo.


                                                                                                                                            The gyrobus had a huge 1m diameter 1 ton flywheel that spun at a rate of 3000 rpm. This gave the flywheel a kinetic energy of 6 million joules, this kinetic energy was gradually bled off by electric motors powering the bus. The bus normally did a stretch of 6km at 60 km/hr in between charges. The gyrobus weighed 11,000 Kg fully loaded and had a huge cross section as regards wind resistance.

How much power did the Gyro Bus use

A simple calculation shows that the Gyro Bus used about 18 Kw (24 hp) of energy per sec., given the huge weight and cross section of the Gyro Bus this is an impressive performance and might be due to the fact that the Gyro Bus was run on electric motors that are more efficient than the IC piston engine, a family saloon using the same system should use a fraction of that energy.

Store the extra power generated by the Rotary Pulse Jet Engine in a flywheel!

n      The idea is to store the massive power generated by the RPJ engine in a flywheel!  Flywheels are already being used in Formula 1 races for short time bursts of power through regenerative braking!

n      By using a flywheel for energy storage a Rotary Pulse Jet Engine can run for just 10 seconds or less to power up the flywheel to 6 Mega Joules, and the next 12-15 minutes or so  power for the car will come from the flywheel.

n      This is how it is possible to dream of mileage of 150Km/litre and more !  The Rotary Pulse Jet Engine will run for only 10 seconds for every 12 minutes (720 secs.) or 15 minutes (900 secs.) or so.

How much power does it take to power up a flywheel ?

§    The answer is simple, power IN equals power OUT.

§    So if we need to store 6 Mega Joules in a flywheel in 10 secs. Then the Rotary Pulse Jet Engine has to yield a power equivalent to 6 Mega Joules in 10 secs !

§    Can it do this ? The answer (hopefully) is with ease !

§    As explained earlier in this presentation, the Rotary Pulse Jet Engine will need a force of 400 Kgf resulting in a torque of 200Kgm (2000Nm) when running at 3000 rpm  to impart a kinetic energy of 6 Mega Joules to a flywheel in 10 secs, this amount of force is just 1/5th of the force that an IC piston engine uses to generate a torque of  just 10Kgm (100Nm), The calculation for  the power developed by the Rotary Pulse Jet Engine and the time needed to power up a fly wheel to a K.E of  6 Mega Joules is given below:

§    Power in KW =  2000 x 6.28 x 3000/60000 = 628 Kw or 628,000 W.

§    Time needed to impart K.E of 6 Mega Joules to flywheel

      = 6000,000/628,000 = 9.5secs.

How long would it take for an IC piston Engine to furnish a flywheel with 6 MJ K.E and how much fuel would it use ?

Taking the example of the 7.6 cm. square IC piston engine described earlier and assuming it is running at 3000 rpm. Power yield would be 31.4 Kw/sec (42hp) and the time it would take to impart an energy of  6 MJ to a flywheel would be 6000000/31400 =  191 sec or 3.18 minutes, fuel used during this time would be  458.4 cc . For this reason it is more practical to connect the engine directly to a generator than to store the energy in a fly-wheel.

Flywheel Energy and the Grid

§    Flywheels are increasingly being used in grid applications but are restricted to smoothing out transient fluctuations in the power supply. This is because in general, power stations generate power in terms of Mega Watts. 5 MW, 10 MW, 100 MW etc., if you have a flywheel with a 20 MJ capacity it will be able to supply power for 4 secs. 2 secs. and 0.2 secs respectively in each of the above cases. A 10 MJ Flywheel could be used to store power from a 2KW windmill for 1.2 Hrs. but if the wait to deliver this power to the grid exceeds 3 hrs. windage losses could be as high as 60% so in either case, it is not really worth it.

§    However in  households where power usage is restricted to  10 KWh  to 15 KWh, a day, and where usage is almost immediate, flywheel energy storage can play a useful role as has been demonstrated by the example of the Gyro Bus,  PROVIDED that a suitable power source is available for bringing the flywheel up to the desired Kinetic energy.   The Rotary Pulse Jet Engine might very well supply this role.

Qualities needed in a power source for flywheels

§      The qualities needed in a suitable power source for practical use of a

     flywheel as an energy storage source are:

§      The fly wheel should be brought up to its K.E in a matter of  seconds,

      this means  that the motive power has to be very powerful and should                      

      have the capability of  starting and stopping fast.

§      The Engine should have a pure rotary output.

§      The engine should be almost  maintenance free so that it can run for

      long periods of time.

§      The Rotary Pulse Jet Engine, if it works as predicted, will  fulfill all of

     these  criteria.

Home Power Generation

n      The scenario for home power generation is even brighter. (Kindly excuse the pun!)

n      An average urban household in India uses about 10 Power Units a day. This works out to about 36, 000 KW. Or  36,000,000 W.

n      Suppose that a Rotary Pulse Jet engine can bring a single or multiple flywheels up to  a Kinetic energy of  12 MJ in 20 seconds. Then theoretically the  RPJ would have to use just three 20 second bursts  to power the house for the whole day. In other words the Rotary Pulse Jet Engine would have to run for just one minute to supply enough power to the house for twenty-four hours. In practice, energy use in a normal household is unevenly distributed over time. So that out of the total 10 Kwh used in 24 hrs. 5Kwh might be used in just  2- 3 hours in the morning, 3 Kwh might be used during 3 hours in the evening  and the remaining 2 Kwh of power use might be distributed over the rest of the day.  In practical terms a flywheel will lose about 15% of its energy to windage losses for every hour, although work is being done to improve these figures.

n      A RPJ engine and flywheel at a fixed location would have greater power generating capability than one on a moving platform such as a car, theoretically it should  be possible to set up a flywheel with a K.E of 12 Mega Joules.  This is because limitations such as precession forces and size will not apply for a flywheel in a fixed location.

n      A 12 Mega Joule flywheel has an energy equivalent to 3.3 Kwh, so in theory a flywheel would have to be charged just twice, (or the RPJ engine will have to run for 2 bursts of 20 seconds each  (40 seconds total)) to take the peak load of 5KWh in the morning and fire for just two or three times after that for the rest of the day. A total of 1 litre of petrol (CNG, LPG) a day.

How much fuel does a Rotary Pulse Jet Engine Consume.

A 3in bore  x  3in stroke IC piston engine, running on a stoichiometrically correct ratio uses about 0.024 c.c of fuel per power stroke. The RPJ engine needs 3 times this amount of fuel or 0.072 cc per combustion event. Since there are two power strokes per rotation of the main shaft and since 2 combustion chambers fire simultaneously, there are a total of 4 combustion chambers firing per rotation of the main shaft, so the RPJ engine uses 4 x 0.072 cc fuel or  0.288 cc of fuel per rotation of the crank shaft. If the optimum rpm for the RPJ engine is 3000 rpm, this equals 50 rps.  So in one second the RPJ engine will use 14.4 cc of fuel and in 10 seconds it will use 144 cc of fuel. These figures can be improved using new lean burn technology and improved sparking devices.

The future of home power Generation

In the future most homes will be off the Grid, each home will generate its own power and switch on and off its power supply as and when it is needed. It will not be necessary for most  households to connect to the grid which is hugely expensive because it has to run 24 hours a day, instead individual households will each have their own power supply, that they  generate themselves.   Power (fuel) bills and power consumption will be totally in the hands of the consumer. However, the Grid will continue to be used by power intensive industries, and to light cities and towns although individual houses in those towns and cities would supply their own power.  Households might in the future create time slots for specific power usage, to ensure optimum use of their home power generation capability. With improvements to the fuel consumed by the Rotary Pulse Jet engine/flywheel combination and software to track power consumption, this may prove to be  cost effective in the near future.

Practical Considerations

n      Today it might sound like madness to suggest that a machine, any machine, could put out enough power in a few minutes to power a home for twenty-four hours.

n      BUT think about it, if even just twenty years ago, one walked into a printers establishment and requested that a 1000 page, 1,000,000 word book be printed and collated in the space of 20 minutes, they would have asked you to buy a magic wand!

n      Yet today this is a task that any high speed printer is capable of.

n      Or think about lasers, if twenty years ago you said you wanted a laser that would have a beam, that could reach twenty six kilometers, fit into your pocket and was powered by tiny 1.5 V button batteries, people would have laughed their heads off. Today, these type of lasers can be bought in any store as key chains.

n      This is the attitude we should keep in mind when thinking about transport and power generation in the future.

Part II : First steps

§    Obviously the idea of the RPJ is good! It is based on sound reasoning. How do we go about implementing it? The answer is that we build a combustion chamber and measure the amount of thrust that it generates. Accurate measurements of the thrust generated by the combustion chambers at various pressures  will give an idea of the performance of the actual engine.

What will it cost to build and test a combustion chamber ?

§    The total amount of money needed to build and test a combustion chamber for the  Rotary Pulse Jet Engine will be  below Rs. 10 lakhs. This amount includes the purchase of ballistic pendulums, electronic accelerometers, pressure sensors,  computerized soft-ware  and the manufacture of  the combustion chamber itself, together with  differently shaped De Laval (CND Convergent Divergent Nozzles) etc., in order to determine the best configuration. Once the theory is validated building a prototype should pose no problems.

Hazards during testing of the Combustion Chamber

n      The advantage of this scheme is that it involves no hazards and no risks, at this stage the thrust generated by the combustion chamber can be simulated using plain compressed air.

n      Tests can be conducted right up to 35Kg/cm2  (500 psi) and more without  any risk.

n      Any materials engineer will tell you that without the complications of heat being present, a pressure of 35Kg/cm2  (500 psi) can easily be contained.

Conclusion

n      The idea of a new type of power plant for cars and a new approach to home power generation and use is long overdue. The Rotary Pulse Jet Engine, is one possible  solution, at least until an even better solution is found. The design of the Rotary Pulse Jet Engine is based on the performance of the recoilless gun and so, is in a sense, validated. The idea of the Rotary Pulse Jet Engine is one that deserves to be followed up.

n      There will always be armchair pedants and pessimists who are content to sit back and spout reasons why something cannot be done.

n      Fortunately there are also people who are open to new ideas and are willing to see if they will work. We need people of the second sort, if we are to break out of the current impasse viz-a-viz man, the environment and the global energy crisis.

End of Presentation