COZBY ENTERPRISES, INC.

How Does an Advanced Rankine Engine Work?
Step by Step Walk Through
(Reference: Flow Diagram)

1.Liquid water is drawn from the reservoir and pumped into high pressure tubing where the water begins to be heated. The tubing then passes into the furnace area where the water is converted into steam. This section of tubing is referred to as the boiler. The boiler tubing is heated by the furnace producing very high pressure steam in the boiler tubing. The boiler/furnace are sometimes referred to as the steam generator.

2.The steam is then heated to a much higher temperature by the furnace in what is called the superheater tube section.

3.This very high pressure superheated steam is then admitted to the first stage of the engine itself. This first stage is a small high pressure cylinder containing a piston. The steam is admitted by means of an injection valve.

4.The piston in the cylinder is then pushed down by the steam pressure. The piston is connected to the crankshaft by a connecting rod. The crankshaft rotates producing useful work. As the steam produces useful work through the piston motion the steam expands, loses pressure, and cools.

5.The steam is then exhausted from the first cylinder by an exhaust valve and enters tubing called a receiver/reheater where the steam temperature is raised by the furnace heat. The steam is reheated so that it can continue to expand in the next stage and do useful work without condensing.

6.The reheated steam which is at a lower pressure is then admitted to the second stage larger intermediate pressure cylinder via an injection valve. The steam pressure presses on the second stage larger piston to produce further useful work as described in the first stage.

7.The expanded steam is then exhausted from the second stage via an exhaust valve and enters a second receiver/reheater and the steam is again reheated so that it can continue to expand and do useful work without condensing.

8.The second time reheated steam at an even lower pressure is then admitted to the largest low pressure cylinder via an injection valve. The steam presses upon the largest low pressure piston producing more useful work as described above.

9.The very low pressure steam from the low pressure cylinder is exhausted via an exhaust valve into a recuperator where exhaust steam heat from the engine is used to begin to heat the feed water which is in a tube on its way back to the boiler.

10.The steam exhaust from the engine then exits the recuperator and continues to a heat exchanger to be further cooled and condensed back to liquid water. This condensate is returned to the reservoir as liquid water ready to be pumped back into the boiler tubing. This is why the cycle is referred to as closed loop, there is no steam exhausted into the atmosphere, and this is a primary reason that Rankine engines are quieter than internal combustion engines. The heat exchanger that condenses the exhaust steam into liquid water is called a condenser and is similar in size, appearance, and function to present automobile radiators. A vacuum pump is employed to keep the recuperator, condenser, and reservoir pressure below atmospheric pressure, or vacuum.

Such a system is much more efficient than a gasoline engine besides being cleaner , fuel diverse, and powerful.

Summary
The water/steam is kept in a closed loop. The high pressure steam does useful work by moving the pistons in the engine. The steam heat and pressure are converted to useful work and low pressure steam is exhausted from the engine. The exhaust steam is condensed back to liquid water to be reused in the continuing cycle.

Note:
Some important aspects of advanced Rankine engine efficiency are that the engine is kept hot through multiple working stages, the exhaust temperature is low, and the fuel is completely combusted with few nitrogen oxides produced. By contrast: Much internal combustion engine inefficiency (especially gasoline engines) is caused by wasting much heat through cooling of the engine, by high temperature exhaust heat from a very limited simple single working stage, incomplete combustion of the fuel, and restrictions because of nitrogen oxides. Gasoline engines waste about 80% of their fuel. There is no such thing as an efficient internal combustion gasoline engine.! (Regardless of what General Motors or the Department of Energy say to the contrary.)

General Design Parameters and Criteria
(How to design and build advanced Rankine cycle engines)

The above page gives a comparison of Rankine cycle to the common refrigerator. Fred Burnell suggested that I expand into some of the fundamental principles of design for the advanced Rankine cycle steam engine. It is not within the scope of this website to go into all the design details or the many various component arrangements that are anticipated. The cylinder/ piston/ crankshaft/crank case portion can vary from three cylinders to forty cylinders depending upon need and application. The arrangement can vary from radial (three to nine cylinders), I-V (three cylinder; a good automobile design), I- opposed (three cylinder), I-doubleV (five cylinder), I-doubleV-opposed or I-triple V (seven cylinder; a good design for a four stage heavy truck application), I-triple V-opposed (nine cylinder), Full-Opposed as described in our patent (ten cylinder), single or double banked (up to twenty), double ended, and double ended double banked (up to forty; for large ships and power generation up to about 100 megawatt size.). The choices are many just for how to arrange cylinder/piston/crankshaft/crank case components. Steam lends itself to great variety. There are at least three different means to control engine speed and protect from over speed conditions which may be used singly or in combination. There are two means that may be employed to vary valve motion which can be applied singly or in combination. An engine may be designed for one direction of rotation or it may be designed to reverse rotation. An engine may be designed with engine braking capability or not. An engine may be designed for extremely high torque and overload capacity as for heavy truck applications. An advanced Rankine system can be designed to use any liquid fuel, any gaseous fuel, or solid fuels; or in combinations. The system can use air or water for the cooling medium for steam engine exhaust condensing. The system can use a pressure fired boiler. Feed water heating by bleeding may be employed in two or three stages. The list goes on, the point being that design details and specifications are major areas unto themselves.

BUT : there are certain definitive parameters and criteria that must be satisfied for a proper advanced Rankine cycle steam engine to operate optimally. Not adhering to these principles was the cause of the of the prototype engines of the 1960's and 70's achieving poor efficiency and performance. General Motors designed Rankine engines were some of the very worst.

1. There are two basic engine types that will be employed. The first type of engine is a three stage engine; The second type of engine is a four stage engine. The three stage engine has a high pressure first stage piston/cylinder, an intermediate pressure second stage piston/cylinder, and a low pressure third stage piston/cylinder. The three stage engine uses high pressure, high temperature steam in the first stage and a receiver/reheater between the first and second stage, and a receiver/reheater between the second and third stage. The second type of engine is a four stage engine. It is constructed similar to the three stage engine except that the four stage engine can use higher pressure steam and realize a greater ratio of expansion. The four stage engine has an additional expansion stage, an additional reheat, and an additional feed water heater. The four stage is more efficient and potentially more powerful, but it is generally bigger, heavier, and more expensive. The three stage system is expected to be employed in automotive type applications, while the four stage would be used in heavy long haul tractor trucks or railroad locomotive type applications. For high power out put the three stage engine can be designed to be made to convert to a high ratio compound engine during operation with a push of a button or by pressing the accelerator peddle. This action greatly increases the power out put of the second and third stages of the engine by greatly increasing the pressure on the pistons of these two later stages. The four stage type engine can be converted to a high ratio, high out put engine by similar means as need arises. For most power requirements, the engine out put can be adjusted adequately by varying the high pressure injection valve timing. The longer the high pressure injection valve is held open the more steam is admitted, and the greater the power out put.

2. The engines must be designed for the highest practical steam pressure and temperature. The highest practical pressure for the three stage is in the range of 3,500 pounds per square inch. The highest practical initial temperature to about 1,250 F with a second reheat temperature to about 1,400 F. The highest practical steam pressure for the four stage engine will probably be in the 6,500 pounds per square inch range at 1,200 F and the third reheat temperature to about 1,500 F.

3. For these high pressures and temperatures the engine must employ high ratios of expansion, but the ratios must be such that the exhaust steam from each stage is still above the saturation point, i.e. the exhaust must be in the superheat range. (This aspect is for lubrication needs as well as thermodynamic considerations.)

4. The engines must be designed for very low exhaust pressures when operating at their usual power levels. This is the reason that high ratios of expansion are employed and the engine exhausts into a vacuum. High ratios of expansion call for high temperature steam in order to maintain dry vapor. Heat recuperation from the engine exhaust steam is employed for feed water heating as well as for fuel and combustion air pre-heating.

5. The United States Energy Research and Development Administration found that water was a better working fluid than other fluids. They found that piston expanders (engines) were superior to turbine expanders. They found that multi-stage reheat engines were superior to simple single stage engines. They found that counter flow piston engines were superior to uni-flow engines. These criteria must be incorporated into any properly designed Rankine engine.

6. Means must be employed to minimize heat loss to the piston/cylinder/head components. The cylinders must be kept as hot as good lubrication will allow without heat loss to the atmosphere. There are three or four means that can be employed for heat retention and heating.

7. The crank case, crankshaft, along with the portion of the piston/cylinder section facing the crankshaft must be sealed and kept at as low a pressure as possible, i.e. under vacuum. This aspect is for both mechanical and thermal considerations.

8. Oil and steam must be kept separated. Oil must not be injected into the steam. Wet saturated steam must not be allowed to wash lubricating oil. The piston rings are lubricated in the manner usual to four cycle gasoline engines. Water injection is used in the valve stem gland seal sections for gas tight sealing and lubrication, as well as for the valve face/cylinder head interfaces. The lubricating oil in the section that is interior to the crank case is separate from the lubricating oil that is external to the crank case. The pistons/cylinders, connecting rods, and crank shaft bearings oiling will be similar to that common to internal combustion engine design.

9. Valve clearance must be kept to a minimum. All valve clearance is an absolute loss and is most harmful in the first and second stages where steam pressure and density are the greatest. Valves must be designed to keep valve clearance to as close to zero as possible. Valve clearance is the dead space between the valve face and the piston face when the piston is at top dead center.

10. For best results the engine will incorporate a flywheel. The valves must be designed so that they open for injection steam only after the piston has passed top dead center at start-up and slow speed operation, but the valves must begin to open before top dead center at higher rotative speeds.

11. Valve motion is the primary key to proper advanced Rankine engine operation. First stage steam injection duration must be variable from 0 to about 120 or from top dead center of the piston to about 3/4 of the stroke in order to vary the engine power. Means are employed to hold the first stage valve in closed position for engine off to save energy even while the boiler is up to operating pressure. By manipulating valve motion an engine brake mode may be employed. By manipulating valve motion the engine may be run in reverse. By manipulating valve motion, engine over speed protection is automatically activated. Correctly designing and implementing the valving is critical.

12. The vacuum pump is designed to operate off of a bleed from the exhaust (before reheat) of the second stage cylinder on the three stage engines and off of the third stage cylinder of the four stage engines. In similar fashion a compressor pump can be made to operate off of a bleed from the first or second stage depending upon the compressed air pressure desired. The compressor can supply compressed air for air brakes, other air powered equipment, and for flushing the boiler.

13. In passenger cars the defrost and interior passenger space is heated by furnace exhaust, boiler steam, or engine exhaust steam, or a combination of two or three methods. This is to make defrosting and heating very economical and quick from start-up. Start-up of the furnace is immediate and drive away can be realized in a matter of seconds.

14. Electronic sensors, instrumentation, and controls in conjunction with computer programing and micro-processors are employed to keep the air/fuel ratios optimum and the steam conditions optimum to give the highest steam generator efficiencies and to keep the engine operating at its optimum capacity and efficiency.

15. Materials used will be similar to those in internal combustion engine design. These include such materials as cast iron, copper, steel, stainless steel, spring steel, bronze and such. For some applications aluminum alloys and titanium alloys may be employed. Ceramics and some exotic coatings may prove useful.

16. The steam generator, engine, and water reservoir should be encased in insulated steel for safety, protection of the components from atmospheric conditions, and to keep the water from freezing by heating the enclosed compartment. (Draining can also be used in conjunction for freeze protection.)

17. An electric starter motor may be employed to initiate rotation. A reversible motor will be used for reversible engines. Manual means of initiating rotation may also be used.

18. Various switches with solenoid controlled mechanisms are employed to function in such areas as: engine off mode, vacuum pump operation, cabin heat/defrost, feed water pump function, steam line shut-off, over load operation, compressor operation, and such. Many of these functions may be manual as well. Some of these functions are selective while some of the functions are automatic or controlled by sensors and programs.

There are other details, but the above 18 areas address most of the design parameters and criteria.

A small automotive system will be a simple three stage, three cylinder engine with a small steam generator with reheating and a condensing system. The engine cylinder arrangement will follow the I-V design. The piston sizes will run in the range of: First stage, under one inch diameter; Second stage, around two inch diameter; Third stage, about six inch diameter. The stroke to be in the range of three to four inches and the speed from around 3,000 r.p.m. to 4,000 r.p.m. The crank throws will be at 120. The valve operating mechanisms will be attached to the front end of the crank case/crank shaft and the flywheel to the back end of the crank shaft.

As simple and straightforward as the above descriptions are, most of the critical aspects of design were unknown or ignored by the developers of the Rankine engines for automobiles in the 1960's and 70's. This was especially true of General Motors Corporation. However, the basic and fundamental principles laid out above have been published and taught in the respected engineering manuals and handbooks for nearly a century. Steam conditions to 5,000 pounds per square inch pressure and 1,250 F are demonstrated in practice, and steam generators to 1,500 F have been built and demonstrated.

An advanced Rankine cycle steam engine can be clean, efficient, fuel diverse, and powerful. Development and production of advanced Rankine engines is one of the worlds great needs.

Alternate Advanced Rankine Engine Valve Motion Designs11.13.10

The valve cams/cam shaft may also be located at the side of the engine block and driven by gear, chain, cogged belt, etc. off of the crank shaft/drive shaft. Push rods, rocker arms, and valve stems would work in the usual manner. Or, the cam shaft(s) can be mounted to the side of the cylinder or cylinder head with the cam lobes in direct contact with the valve stem ends. The cam shaft(s) could be belt driven, etc.

This arrangement can make the engine over all length more compact and the cylinders can be arranged in-line, I-V, or simple V configuration.

Also, a combination may be used: the high pressure valve cams, etc. can be located as an extension of the end of the crank shaft/drive shaft with the later stages operated from the side of the block or be mounted on the cylinder or heads. Or, the high-pressure cylinder can have its cam shaft located on one side of the engine and the other stages cam shaft(s) located on the opposite side of the engine.

Valve advance and engine reverse modes would work in the same manner as previously shown, i.e. by centrifugal bell-crank for advance and cam shaft shifting for reverse, etc.

This is to show that there are various ways to configure not only the cylinders and crank shaft, but also the valve mechanisms and valve motions as desired and chosen.

A three cylinder/three stage, in-line engine with belt driven cam shafts might be a very good choice for automotive applications.
John A. Cozby

Three Important Formulas

Reference: Marks Standard Handbook for Mechanical Engineers, Eighth Edition, 1978

Valve and Port Sizes Flow area of valves and cross section of ports are usually determined by port area = AS/C in², where A is net piston area, in², S is mean piston speed, ft/min, and C is a constant, ft/min. Values of C are approximately 9,000 to 15,000 ft/min for inlet and 6,000 to 7,000 ft/min for outlet. Small valves and ports represent lost work.

Reference: Marks Mechanical Engineers Handbook, Fourth Edition, 1941, page 325

Isentropic Expansion of Superheated Steam

The isentropic expansion of superheated steam is fairly represented by

pvⁿ = const, with n = 1.315.

The volume at the end of expansion is V₂ = V₁(p₁/p₂)^1/n

Reference: RYERSON, Joseph T. Ryerson & Son, Inc., Steel, Special Metals, Spokane, Washington, Edition 121, pages 135 and 138

Bursting Pressures, Steel Fluid Line Tubing

Per Barlows Formula Burst P = 2ST D

S = Allowable Fibre Stress, T = Wall Thickness, D = O.D.

S is the tensile strength in PSI. One must consult RYERSON STEEL & ALUMINUM DATA BOOK for specifications, properties, etc.

(On Sealing High Pressure Steam)

To Jukka 4.4.12 Rev. 7.5.12

Your reply to my statement: For the small high pressure piston, more positive sealing means other than piston rings is probably a better approach. Your comment was: I dont know any other method. Perhaps the-gapless-ring.

Your quandary is understandable, you are not alone. Therefore, this topic needs some discussion because it is at the crux of a serious problem related to high pressure steam engine design and development.

The problem and the more recent history:
The problem is that the higher the steam pressure and the smaller the piston the more difficult it is to secure a tight leak proof seal for the high pressure cylinder using piston rings. The result is blow-by and loss of steam, pressure, and heat from the high pressure cylinder. The use of piston rings has proven to be an inadequate sealing means. Losses in the range of 10% have been shown. Such losses are clearly unacceptable. This was a problem for Saab as shown in their S.A.E. (Society of Automotive Engineers) paper. Saab employed SEVEN piston rings. This problem was also confirmed by both Tom Kimmel and Ken Helmick of the Steam Automobile Club of America (SACA). They both relate that high pressure steam loss in small automotive size engines has been an obstacle to development for innovators here in the United States as well. This has led some to the opinion that high pressure steam cannot be adequately contained in a small cylinder. This conundrum appears to be the Achilles heel for small efficient high pressure automotive engines.

Some solutions to the problem:
First we will look at the piston ring problem.
Piston rings may be capable of sealing the high pressure cylinder if the rings are properly and adequately lubricated. The method most often used to lubricate piston rings in steam engines is by injecting oil into the steam. This is bad for two reasons; one, the rings and cylinder wall are not adequately lubricated, and two, the steam is contaminated with oil. Improperly (under) lubricated rings and cylinder will not seal against high pressure steam. Oiling of the rings is not only to reduce friction and wear, but also for sealing and cooling. Prof. Dr.-Ing. h.c. J. Stumpf in his book, The Una-Flow Steam Engine, 1922 refers to and describes a method of oiling rings by pumping oil between the rings. Such a procedure can also be applied to piston rings by channeling oil from the connecting rod/crankshaft journals, through the connecting rod to the wrist pin, and from the wrist pin to an opening in the space between rings. There is a small return opening which drains the oil back to the crankcase. This provides for a sufficient and continuos flow of fresh cool oil to adequately coat the rings and cylinder wall without injecting oil into the steam. The motor oil should be of a fairly high viscosity. The oil is cooled before being pumped into the crankshaft. This method of oiling rings can be applied to any of the stages of the engine, that is: the high pressure stage, the intermediate stage, and the low pressure stage.

Second we will look at complete sealing without rings:
Since complete sealing with piston rings of high pressure steam in small cylinders is problematic, there is another method that completely eliminates leakage of steam. Prof. Dr. J. Stumpf discusses this approach in his aforementioned work, and it is more completely covered in Marks Mechanical Engineers Handbook, 1941. Marks has four sections that deal with high pressure sealing. Quoting form Marks, pages 1051 and 1052 on PACKINGS By F. C. Thorn: Sliding contact packings include all packings that operate against moving surfaces. . . . The only sure way to eliminate leakage is to inject into the packing another liquid at higher pressure, permitting it to leak both ways from the point of admission. This is the basis for the use of the water seal and for the force-feed lubricating of metal packing sets when operating against steam or gases. . . . rod or plunger packing . . . They are used for steam under the most severe conditions of temperature and pressure . . . Where it is desired to effect complete sealing it is common practice to inject water or other fluid into the packing by way of the H-shaped lantern ring shown in Fig. 27. (The descriptions are accompanied by drawings referred to as Fig.s) It is clear that these means of effecting complete sealing are not new, they are not original, nor are they unique to me, but they do work and they do answer the need. However, these means are not and have not been applied in the design or construction of modern automotive type steam engines to my knowledge, but they need explanation and application; i.e., they need to be specified and used. They can also be applied to the second stage as well, if necessary. The purpose is to prevent steam or water from leaking from the system or from being contaminated.

The following describes how these above quoted means are applied to high pressure automotive type steam engines:
As an example we will take an engine with a 0.750 inch diameter bore for the high pressure cylinder. [A 0.750 inch high pressure cylinder is adequate for a rather large and powerful automotive type steam engine operating on high pressure steam and with high ratios of expansion.] The high pressure piston is a polished rod that is ground and lapped to a close sliding fit in the cylinder. (This small diameter piston is steepled to a cross-head.) The lower end of the high pressure cylinder is bored to create a stuffing box. The cylinder end of the stuffing box contains several carbon ribbon packings. The central portion of the stuffing box contains the H-shaped lantern ring and an inlet line and an outlet line creating a water seal gland for high pressure water. The crankcase end of the stuffing box contains several carbon ribbon packings and the tightening ring. (Carbon packings have very low coefficients of friction and do not seize, while the sealing water is both lubricative and cooling.) The boiler feed water line is connected to the inlet side of the water seal gland supplying high pressure water to the gland seal/packing and effecting complete sealing. The boiler feed water exits the gland seal by the outlet line continuing its path to the boiler. The very small amount of water that leaks into the cylinder side from the stuffing box will flash to steam and become part of the working fluid for the following stages. The very small amount of water that leaks into the crankcase side of the stuffing box is collected and drained back to the feed water reservoir. There is no loss of steam, that is, no blow-by of steam nor is there any loss of water. (It should be noted that the valve stems are sealed in a similar fashion.)

Another means of sealing is the same as that described above, except that oil is used as the sealing fluid. Small amounts of oil are continually being injected into the gland seal under high pressure. The oil then returns to the crankcase by an exit oil line that has a high pressure relief valve that is set to a pressure that is slightly higher than the steam pressure so that steam cannot leak into the gland seal. The high viscosity of the oil greatly reduces leakage through the packings and is a better lubricant. By whichever means is employed, positive sealing can be obtained providing for long duration of operation between feedwater servicing

Reheaters

Following are some general guidelines for reheater design. These can be altered or changed according to need and experience. The volume of the reheater is suggested to be about 20 times greater than the volume of the previous cylinder. The cross sectional area of the reheater tubing should be close to the same area as the exhaust port to which it is connected. These general guidelines are meant as a starting point.

These items are given in addition. The reheat tubing may be better if finned. It may also be better if the tubing is blackened or copper plated. The tubing may work best if slightly flattened and twisted. Heat transfer needs may indicate double lines of smaller diameter rather than a single reheat tube. Secondary or auxiliary burners may be needed for adequate heating under some operating conditions. These are areas of significant potential for future investigation and development. That which is most practical for a given application should be chosen, recognizing that there are many trade-offs in design selection.

SLIDE VALVES (Cozby type) John A. Cozby Aug. 27, 2012

     There are several aspects to the type slide valves designed for advanced Rankine cycle engines.  Advanced Rankine engines are counter flow, re-heat engines.  Valves are located in the heads at the top of the cylinder, with the exception that the third stage exhaust valve is inside the cylinder.  The valves are operated by cams.  Valve design and function are of paramount importance.  (The following aspects apply in a three stage engine.) 

  1.  Designed to eliminate valve clearance for the first and second stages, which is most important, and to minimize valve clearance for the third stage.  The first and second stage valves are one-piece and control both injection and exhaust functions from a single set of cams on each stage.  The third stage valves have separate injection and exhaust valves with separate sets of cams.  The third stage valves are grid type. 

  2.  Valve stems are balanced, going completely through the heads.  The third stage exhaust valve stem extends through the top of the cylinder.  One end of the valve stem is spring loaded, the other end is moved by the cams. 

  3.  Valve stems are sealed with packings with a high pressure liquid water gland seal between packings. 

  4.  The valve stem gland-seal water is fed to the space between the valve face and the valve seat forcing the two surfaces apart.  This action serves five purposes:
          1.  Lubricating
          2.  Cooling
          3.  Lifting (balancing)
          4.  Sealing
          5.  Permitting seal water flow-through 

  5.  A small amount of water is injected per revolution.  (This water flashes to steam resulting in a semi-hot head engine effect.)

  6.  The injection is timed to occur just at the time the valve begins to move. 

  7.  Little valve motion is required. 

  8.  The valve is motionless (dwells) for a large portion of each cycle. 

  9.  Little force is required to move valves. 

  10.  Infinitely variable cut-off from about 10% to 80% first stage is probably best. 

  11.  The valves can lift off of their seats to allow any liquid or over-pressure steam to be expelled from the cylinder preventing damage to the engine.  This is particularly important at start-up.  

Definition

Best Rankine engine / ˈraɳ - kən/  1:a highly efficient advanced steam engine system.  2: The best Rankine engine system is a closed loop or closed circuit arrangement; that is, a closed path followed by a fluid in a mechanical system.  The fluid is water/steam.  Water is pumped from a holding tank (hot well) through a recuperator and regenerative feedwater heaters into an economizer and from thence into the boiler.  The system incorporates a furnace which heats a monotube boiler, super heater, and multiple receiver/reheaters.  The boiler changes the water to steam.  The system uses steam at a high initial pressure and high super heat.  The fluid (steam) expands through a three stage (triple) or a four stage (quadruple) expansion counter flow  engine with reheating between stages.  The steam expands greatly (has a high expansion ratio).  As the steam expands it moves pistons which turn a crankshaft to produce rotative power for useful work.  As the steam expands the pressure decreases.  The steam is kept dry (super heated) until it is exhausted from the engine.  The steam is exhausted at low pressure and flows through a recuperator which heats feedwater on its way to the economizer.  A centrifugal exhauster may be employed.  The exhaust steam is then condensed back to liquid water in the condenser. [Steam collapses as it condenses, maintaining vacuum.]  The condensate (water) then returns to the hot well.  A vacuum is maintained in the recuperator, condenser and hot well and also in the engine crankcase.  There is a regenerative feedwater heater bleed at the upper end of each receiver/reheater (before reheating begins).  Air and fuel preheat is provided.  In vehicle applications the best Rankine engine employs a flywheel, clutch, and transmission (or the equivalent).  Best efficiency is gotten with early steam cut-off in the first stage, and running at relatively high speed.  Engine speed and power is by cut-off to the first stage.  Valve timing is by cams and automatically advances at higher r.p.m.  For vehicles, neutral, brake, and reverse modes are provided.  For high torque requirements an interceptor valve (to change the engine temporarily to a compound) is provided.  Steam generation and steam properties are automatically controlled. 

Best Rankine engine is easy to understand and production is by standard present technology.  America needs the best Rankine engine.  An engine that does not measure up to the above criteria is not a best Rankine engine.  Deficient designs and mistakes of the past should not be repeated.  There are many steam engines that “work”, but are not the best. 

John A. Cozby
Nov. 28, 2012
cozincmtusa.com 

SIXTEEN  POINT CHECK LIST

Basic Elements of a High Efficiency Closed Loop Steam Engine System

1.     High pressure steam (3,000 psi and above range)

2.     High temperature steam (1,200˚ F range)

3.     Multiple stages (3 or 4)

4.     High temperature steam reheats (1,200˚ F range, 2 or 3 reheats)

5.     Truly high expansion ratios (similar to power plants’)

6.     Vacuum exhaust (1 to 2 psia range, similar to power plants’)

7.     Minimum valve clearance

8.     Adequate lubrication

9.     Tight sealing

10.    Regenerative, recuperative, economizing feedwater heating

11.    Crankcase vacuum

12.    Oil cooling (keep oil in the 100˚ to 150˚ F range)

13.    High efficiency furnace, monotube boiler and reheaters (over 90%)

14.    High efficiency condenser

15.    Exhaust expeller

16.    Air and fuel recuperative pre-heating

Getting it right is not difficult, but necessary if good economy is desired.

Design and Function of Valves for High Pressure Multi-stage Steam Engines
John A. Cozby           December 11, 2012

Valving is probably the most important, most difficult, and most complex part of a steam engine if the valving is to accomplish all of the various needs of and demands on the engine.  Engine rotation (forward or reverse) can be initiated by starter motor.  Self starting is a moot issue.

I.  Type of Valves (descriptive, different for each stage)
 1.  Modified Sliding (½ “D” type, a single valve per cylinder)   
  1.1 First stage (high pressure), and second stage (Intermediate pressure)
  1.2 Intake
  1.3 Exhaust
  1.4 Single acting
  1.5 Across cylinder head       
  1.6 Balanced valves
  1.7 Positive seal
  1.8 Balanced valve stems
  1.9 Valve stem positive liquid gland seals (steam tight)
  1.10 Injection straight into cylinder (valve out of steam flow, no ports/passages)
  1.11 Injection and exhaust are on opposite sides and sized appropriately
 2.  Sliding plate grid type (two valves per cylinder, providing large area)                  

  2.1 Third stage (low pressure)
  2.2 Intake and exhaust are separate plates on opposite sides properly sized
  2.3 Non interference
  2.4 Single acting
  2.5 Across cylinder head
  2.6 Balanced valves
  2.7 Positive seal
  2.8 Balanced valve stems
  2.9 Valve stem positive liquid gland seals (steam tight)
  2.10 Injection straight into cylinder (virtually no ports or steam passages)

II.  Sealing (positive sealing for sliding valves; steam tight – Dr. Stumpf)
 1.  Fine finish ground then lapped together at temperature valve will operate (Dr. Stumpf)
 2.  Cool liquid water injected between the two surfaces (Dr. Stumpf)
  2.1 Small amount injected per revolution
  2.2 Forms liquid steam tight seal between mating surfaces (Dr. Stumpf)
  2.3 Lubricates mating surfaces (Dr. Stumpf)
  2.4 Cools mating surfaces (Dr. Stumpf)
  2.5 Balances valve (lifts valve, balances pressures)(Dr. Stumpf)
  2.6 Creates semi-hothead effect

III.  Cut-off
 1.  First stage, variable from about 10% to 90% of power, or down, stroke
 2.  First stage opening varies with cut-off (wider for later)
 2.  Second and third stage set at 1/8th of power stroke

IV.  Exhaust
 1.  First stage, begins about 1/3 of return, or up, stroke and continues until close to TDC
 2.  Second stage, begins about 1/3 of return stroke and continues until close to TDC
 3.  Third stage, begins at BDC and continues to almost TDC

V.  Valve motion
 1.  By cam (although eccentric can be employed) Dr. Stumpf and Abner Doble used cams
 2.  First stage cams are separate from second and third stage cams
 3.  Lap and lead provided (for positive sealing)
 4.  Advance / retard
  4.1 Injection valves open after TDC at low rpm
  4.2 Injection valves open before TDC at high rpm
 5.  Valve motion is small or short stroke (compared to much past practice)
 6.  Valves dwell at various positions (i.e. valves are not in constant motion)
 7.  Return is by valve spring (valve adjustment is through the valve stem ends)
 8.  Positions
  8.1  Forward
  8.2  Neutral
   8.21 First stage injection valve does not open
   8.22 First stage exhaust operates normally
   8.23 Second and third stage valves operate normally
   8.24 Receivers and cylinders empty
  8.3  Brake
   8.31 Brake is employed after neutral
   8.32 First stage injection valve opens at BDC
   8.33 First stage injection valve closes at TDC
   8.34 First stage does not exhaust 
   8.35 Second and third stage valves operate normally, but have no steam
  8.4  Reverse
   8.41 Reverse can be employed after brake
   8.42 No valve advance, valves only open after TDC (slow speed)

VI.  Valve clearance
 1.  First and second stage, no clearance (piston face “kisses” valve face)
 2.  Third stage, very small clearance

VII.  Valves can float (a few thousandths of an inch)
 1.  Prevents any over compression
 2.  Prevents water lock-up

VIII.  Interceptor valve (changes engine temporarily to a compound)(Abner Doble’s term)
 1.  A separate valve in the steam lines
 2.  Activated by a solenoid
 3.  Opens boiler to first receiver; exhausts first stage to second receiver
Use of cams makes the various functions possible and gives good overall control.  Speed is governed by centrifugal force moving cams to neutral and/or by electronic sensor and solenoid valve that stops steam flow to engine.

Sealing and Lubrication in High Pressure Multi-stage Steam Engines
John A. Cozby        December 13, 2012

I.  Steam engines should be and can be steam tight (they should be well sealed)
II.  Steam engines should be well lubricated
     1.  Lubricant should be cool
     2.  Lubricant should not leak
III.  Sealing and lubrication are interconnected
IV.  Lubrication requires two separate systems
     1.  A pressurized system which supplies oil to the areas under vacuum
          1.1 The vacuum system utilizes an oil cooler
     2.  A pressurized system which supplies oil to areas operating at atmospheric pressure such as            the auxiliaries, cams, and such
V.  Crankcase lubrication (under vacuum)
     1.  Main bearings
     2.  Connecting rod bearings
     3.  Wrist pins
     4.  Cylinder and rings (oil forced between rings, Dr. Stumpf)[no oil to first stage]
VI.  Third stage, low pressure, cylinder and ring lubrication details1
     1.  Steam temperatures in cylinder (using 4 inch stroke in this example)
            1.1 1,200˚ F steam enters top of cylinder for ½" of stroke
            1.2 temperature drops to 440˚ F by end of stroke
            1.3 temperature continues to drop as steam expands and exhausts for full return stroke
            1.4 temperature below 400˚ F
            1.5 cycle repeats
            1.6 1,200˚ F for only about 6% of each cycle (1,200˚ F injection steam does not mean a                        1,200˚ F cylinder or 1,200˚ F oil)
  1.7 no oil is injected into the steam (steam and oil are kept separate)
     2.  Oil temperature is about 100˚ F
            2.1 Aluminum oil pan with cooling fins
            2.2 Oil passes through an oil cooler
            2.3 A fresh cool film of oil is applied to cylinder and rings twice per revolution
                   2.31 the cool oil forms a thermal barrier (Dr. Stumpf)
                   2.32 the oil lubricates the cylinder and rings
                   2.33 the oil cools the cylinder and rings
                   2.34 the oil forms a gas tight seal between cylinder wall and rings
                   2.35 the oil film protects the cylinder and rings
                   2.36 these temperature parameters are essentially constant for all engine loads
                   2.37 the oil film is not affected by the dry (superheated) steam (does not “wash” off)
                   2.38 the cylinder temperatures remain fairly constant and equal top to bottom
VII.  Second stage, intermediate pressure, cylinder and ring lubrication details1
     1.  Second stage lubrication is very similar to the third stage
     2.  The second stage average temperature will run about 70˚ to 100˚ warmer than the third                   stage because of the higher exhaust pressure but well within the limits of present oils
     3.  If necessary, the second stage can be sealed in the same way the first stage is sealed

VIII.  The first stage, high pressure, is treated entirely differently
     1.  1,200˚ F steam can be admitted for 90% of stroke, oil cannot be used
     2.  the piston is small (typically about 3/4 inch diameter)
     3.  the piston is a smooth shaft with close sliding fit in the cylinder (no rings)
     4.  a double stuffing box with a liquid gland seal between seals the cylinder and piston
     5.  Cool feedwater at boiler pressure effects steam tight sealing
         5.1 the water seals
         5.2 the water cools
         5.3 the water lubricates (Dr. Stumpf, Harry Schoell, Marks’)
         5.4 the first stage is steepled with cross head 
IX.  Sealing the valves and valve stems
     1.  The paper “Design and Function of Valves for High Pressure Multi-stage Steam Engines”,              written myself, covers this matter in detail and the reader is referred thereto.
         
     It is seen that sealing and lubricating a high pressure, high temperature multi-stage, reheat steam engine is not difficult, but it is critical to proper operation.              

1 The second and third stage pistons are single acting trunk pistons similar to present automotive pistons with connecting rods.

From: The White Steamer by A. T. Edmonson, Chicago, Ill. 1910; pages 13, 14

     “Lubrication . . . enumerated in the order of their importance:
 1st. The cylinders.  Applied energy is obtained from a steam engine by means of the steam pushing a piston up and down in a closed cylinder.  This piston must fit close enough to be steam tight and at the same time be free to move up and down.  From this fact it can readily be seen that the power and economy of the engine depends upon a steam tight joint between the moving piston and the cylinder walls.  Proper cylinder lubrication helps preserve this steam tight fit and helps to prevent leakage past the piston by forming a film on the cylinder surface. . . .
  On the scale of importance, the second place for lubrication is given to the engine crank case.” 

The White Steamers injected oil into steam at 735 degrees F.

Doble injected one drop of oil into 765˚ F steam for four cylinders once for every 50 revolutions.
Besler, successor to Doble, used 800˚ F and 825˚ F steam in their engines.
SES, ERDA Contract E(11-1)-2701, used 900˚ F to 1,100˚ F steam in a uniflow engine. 

Dr. Stumpf, Besler, I. C. Engine, Prof. Faires

     Confirmations from Dr. Stumpf;
1.  Valves — cam operated automotive
2.  Valves — slide, force fluid between surfaces, grind/polish at operating temperature.
      (Fluid lifts - balances, seals, cools, lubricates valve surfaces)
3.  Ring \ cylinder lubrication — force oil between rings (very good for counter flow, single acting, trunk piston, ringed, steam engine cylinder such as Cozby Ip and Lp cylinders)
4.  Stem and rod sealing — high pressure liquid gland seals (fluid lubricates, seals, cools)

     Besler Piston Valve
From Fig. 4 and Fig. 6; 1/4 scale
2 inch diameter; 7.25 inches long; 2.5 inch stroke
(Besler has run their engines as high as 3000 rpm)
[stem not balanced, no liquid gland seal, single port, large valve clearance]
{about twice as large with about twice the stroke of the Ip Cozby valve}

     Internal Combustion Gasoline Automobile Engine Lubrication and Sealing
Counter flow
Single acting
Trunk piston
Rings

Cylinder temperature fairly constant — cylinder remains cylindrical
Close tolerances
Large quantity of oil
Oil is cool (even cooled)
[The oil lubricates, cools, seals, forms a thermal barrier, protects]

Seals high temperature and high pressure gas
Runs a long time

We should buy a clue!

        Prof. Virgil Faires, Texas A & M (SACA Bulletin, Jan -Feb, 2013)
“If the steam is superheated sufficiently, the walls will remain dry; and even though the temperature range is increased, there will result a net saving . . . because the rate of heat transfer between superheated steam and dry walls is less . . .”
If the cylinder walls are not dry it is useless to try to lubricate and seal the cylinder with oil.  The oil forms a thermal barrier as well (Dr. Stumpf).