SCHOELL CYCLE REGENERATIVE ENGINE IN THE AUTOMOBILE.
By James D. Crank1 1-16-12-f PREFACE. Over the last 250 years, steam engines ushered in the American Industrial Revolution, powered
our factories, drove the locomotives that fueled our Western Expansion and powered ships that navigated America’s rivers and coastlines well into the 20th Century. Steam built this country and today, steam remains the driving force behind over 60% of our nation’s electricity production – natural gas, coal and nuclear power plants run on massive Rankine cycle steam turbines, as do our nuclear submarines and ships for the U. S. Navy.
Recent and dramatic advances in steam engine technology utilizing new materials, unique designs and creative processes such as extensive heat regeneration and water lubrication have made these engines smaller, lighter, more powerful and more efficient than ever before. Today, steam engines again have the potential to power cars, trucks, busses, trains and other forms of modern transportation in ways that are simpler, cleaner, quieter and less reliant on fossil fuels than current practical alternatives. The problem has never been the Rankine cycle itself; but the application of it via the hardware to produce efficient power.
The reader must understand the very basic fundamental difference between the internal combustion (IC) engines and the external combustion (EC) steam engine. In the IC engine power is produced by combustion of the fuel inside each cylinder and it is a cyclic event with varying pressures and temperatures throughout the pistons power stroke. In the Rankine cycle steam engine, the power is produced in the steam generator by burning the fuel at a constant rate and constant temperature with low air pressure and a long term residence time for the fuel particle. Harmful pollution is under complete control and is not present in a correctly designed burner without ANY pollution control hardware at all, a most unique feature only found in the Rankine cycle steam engine and the Stirling cycle hot air engine.
Being external combustion, these two engines are able to burn any fuel that can be supplied to the burner.
The engine, or more accurately described as the expander, is not the actual power source that is elsewhere in the steam generator. Also, the actual power level the steam engine will produce is determined in part by this available steam pressure and temperature. The expander is factually only the converter for transforming heat energy seen as hot steam pressure from the steam generator into shaft power.
Identical to the way the battery electric car also stores its power as chemical energy in the battery with the electric motor acting as a converter to change this chemical-electrical energy to shaft power.
This also is also the reason why the Rankin cycle steam engine produces such large starting torque. The EC engines averaged cylinder pressure (Brake Mean Effective Pressure) is controlled by the initial steam pressure and the amount entering the cylinder on each power stroke and not by the changing conditions inside the cylinder which only last for milliseconds as in the IC engine, the explosion of the fuel-air mixture, but on a controlled longer term basis which the steam engine employs. These are two very different operating conditions and are described in detail further in this paper.
It is also important for the inquiring engineer to understand that while IC engine design is a very well established science, efficient Rankine cycle engine design has now entered a totally different phase.
Early work on vehicle steam engine systems since the turn of the 20th Century ranged from 15% to perhaps 23% net cycle efficiency. In the world today that is just not sufficient to encourage a return look at the cycle for vehicle propulsion, it has to be a lot better, it has to be competitive to existing IC engines. This, as will be examined in this paper, is what prompted the Cyclone engine development, combined with a global warming situation and a need to drastically reduce foreign oil consumption for transportation purposes. The cycle itself does offer more than sufficient gains to encourage a very serious re-examination and a return. This is what the Cyclone Rankine cycle engine has now made attractive and definitely possible. The return application of this cycle cannot be neglected any longer.
This paper is written to explore and discuss the possibilities of applying the modern Rankine cycle steam engine to the automobile, interstate truck and other vehicles. With the design and material improvements available today, the Rankine cycle engine cannot continue to be ignored as a mobile power source. One such engine developed by Cyclone Power Technologies2, the Schoell cycle engine, of all the steam systems proposed, offers the most advanced form and presents the most competitive net cycle efficiency to any IC engine and could be the closest to production. It is not a wishful proposal; Cyclone’s Schoell cycle engine is a working reality with important funded contracts in house and continuing development and dynamometer testing refining the design.
Finally, this author would like to thank certain individuals who have helped make not only this paper, but also more importantly modern steam a reality. Harry Schoell, the consummate inventor and namesake for the Schoell cycle engine, is someone I’ve known and watched with interest for a number of years and who initiated the writing of this paper.
Mr. Schoell may have just brought more to the practical development of modern steam technology than anyone in the past three-quarter century. One approach that was studiously avoided and which has doomed so many wishing to improve the Rankine cycle steam engine, was the vaporous imagined theoretical approaches that many past academics and corporate managements have used and totally failed to achieve, just because of a total lack of any real experience and even real knowledge about these engines. Mr. Schoell took the firm position that the work was based on practical hands on experience and assembled a Board of Advisors that had the knowledge to assist in this direction needed for success.
He took a very important approach today when deciding to work with the Rankine cycle steam engine, with the guiding direction of reducing global warming and economically operating on U. S. produced carbon neutral fuel. There is continuing debate whether global warming is a natural long period event or is being accelerated by mankind. What the eventual truth will be is not being debated in this paper, only to state that it does seem to be accelerating and what we can do to slow down this condition is worthy of being done on a worldwide basis. The use of fuels other than petroleum is also not debated, we are consuming this natural resource at a great rate and substitution is also worthy of being implemented.
One paramount consideration was that the potential inherent in the Rankine cycle engine has never been fully optimized nearly as much as it must be to become a competitive power source today for the automobile and truck. Mr. Schoell identified each of the previous features and operating parameters that apply to this power source and also what was not optimum and where research and improvement was demanded to bring the engine into the 21st century. He then proceeded to fund and implement those improvements with seriously advanced design, working experimental hardware and a firm commitment to succeed. He formed the company Cyclone Power Technologies, Inc. to enact this work.
Harry Schoell is not alone in this quest for improving the Rankine cycle steam engine a few others also share this goal. Experienced steam car engineers who also know as fact that the steam engine has enormous potential providing it is developed along these improved lines. His team of technical advisors includes some of the most proven, respected and knowledgeable people in the field, including Robert Edwards, a former fellow engineer from Lockheed-Martin, and George Nutz, whose work with steam cycles over the last 50 years is unrivaled in the field. George did much of his early work on steam at the MIT Instrumentation Laboratory, part of the Department of Aeronautics and Astronautics, and represented MIT-IL at the Department of Transportation Clean Air / External Combustion hearings in the late 1960s. In the spirit of full disclosure, this author also serves as an enthusiastic technical advisor for Cyclone’s Schoell cycle engine. One must also thank the people that have fought to keep steam automobiles in the public eye such as Tom Kimmel, the President of the Steam Automobile Club of America, Jay Leno whose collection of antique steamers this author knows very well and the hundreds of steam enthusiasts worldwide who study, build, drive and collect these fascinating vehicles.
THE APPLICATION OF THE RANKINE CYCLE TO AUTOMOBILES. The steam powered automobile has existed since the very genesis of that form of transportation. At the turn of the 20th Century, steam was the desired power source. It was understood, used and accepted worldwide in all sizes and applications including the steam engines that powered factories, ships, cars and locomotives. If you wanted a high power output, then steam was the only possible choice. By then, electricity was becoming a serious contender; but not yet up the power levels demanded by industry.
On the contrary, the internal combustion engine (IC) was a cantankerous and unreliable power source until the various automobile manufacturers took the technology under intense development and one by one eliminated the problem areas such as the hand crank starter, carburetion with all of the sophistication of chicken watering troughs, lubrication by dip hope and pray, primitive ignition and low engine efficiency and poor reliability. The IC engine soon became the accepted prime mover for vehicles and the steamer was relegated to the background, except for a few companies and enthusiasts who refused to bow to this way of thinking and to abandon the features that only steam offered.
Why was this? An often repeated statement was that a driving goal was to get reliable power from this one lump of iron and not the collection of components all strung together with yards of plumbing. Then having to wait until the boiler got up steam was another, crank the engine to life and away you go was a serious inducement.
Today that dream of a good and modern steam car is still alive and active in the hands of many enthusiasts worldwide. It is an achievable goal that refuses to go away, nor should it.
The steam powered automobile as it exists now has not benefited to any major degree from engineering improvements, technological advances, or the application of many of the new materials available since World War II, not really in all respects. Most of the recent modern steam projects have only employed Band-Aids and some detail advances in specific areas to what is still basically a 19th Century technology. A few proposed steam systems that this author has witnessed being promoted, border on the technically absurd. The numbers of seriously wrong concepts that are floating around are simply astounding to witness. Quite frankly, these legacy steam power systems, utilizing antiquated technology and materials, will not begin to provide the pollution control, fuel efficiency, simplicity, reliability, power density and compactness required to ensure commercial success today. They are best left as most interesting hobby subjects to be enjoyed for what they represent. A brisk run in a fine restored vintage Stanley or White steamer or a serene cruise in a 19th Century steam launch are most certainly very enjoyable. Events to be remembered and savored for a long time.
What was necessary was a total objective review in all areas of Rankine cycle engineering – a clean sheet of paper with detailed concentration on advancing the work in specific problem areas.
In the opinion of this author, Cyclone Power Technologies has done this to a greater extent than any other developer known or reviewed and the developments introduced in the early prototypes of Cyclone’s Schoell cycle engine are showing a dramatic improvement over Rankine cycle engines of the past.
THE RIGHT QUESTIONS AND REALISTIC ANSWERS. Questions that we should be asking with respect to automotive power sources are which ones are really practical, reliable, cost effective, and acceptable to the car-buying motorist, what will he willingly spend his money on? Which ones truly address the greatest environmental problems of our time, and allow our nation to wean itself off the use of traditional fossil fuels that increasingly come from volatile, if not actively hostile, areas of the world? Once identified, it is up to the manufacturers to provide them.
With respect to the advancement of vehicle technologies, the prime goal of the responsible scientific community, in the opinion of this author, is to reduce as much as possible the CO2 level produced by the automobile and to reduce the consumption of imported petroleum. This means in part making carbon-neutral fuels and burning less of it – especially homegrown bio fuels which are commercially, financially and morally attractive. Basing one’s fuel supply future on unstable and often unfriendly nations is an increasingly risky business. Our scientific community must also be charged with seeing that the total energy consumed by any new fuel system being promoted for large scale production is as low as is practical. The reduction of this speed of climate change increase is the primary emphasis for all of this work, along with reducing the use of petroleum fuels for transportation.
From a practical standpoint, we also need to ask whether a new engine format can quickly be put into production even on a limited basis. What tooling costs are involved and what training of the assembly line workers is needed? How would it affect the suppliers? What would it cost to introduce even a limited conversion plan? Could or would they offer a special engined model? Often, the negative mindset of risk-adverse corporate executives, or those who are basing their opinions of such new technologies on old and out-dated concepts, confuses and obscures these practical issues. The solutions seen being offered by Government must be viewed with great suspicion. Political goals, arrogance, confused science and lobbying by special interests has seriously clouded the picture and resulted in some large added costs to the purchase of the modern IC automobile and their repair bills.
Overall, there are primary reasons why this author believes that the modern steam engine is a most satisfactory path to take for our automotive future. It is most obviously not the only one possible, no single engine has that distinction; but the Rankin cycle engine certainly will do the job very well and is a definite possibility for the near term future if given the chance and correctly applied.
Steam engines being external combustion are inherently cleaner and inherently less pollution producing compared to any IC engine. In the proper burner design NOx is not produced.
Steam engines demonstrate true fuel flexibility; they can burn virtually any liquid or gaseous fuel in the cleanest manner possible without any added hardware or control systems.
Steam engines can provide higher fuel efficiency in city and stop-and-go driving conditions.
New designs can provide overall net cycle efficiencies rivaling Diesel engines with relatively unrefined fuels and without additives as compared to any IC engine.
Steam engines match the torque and horsepower requirements of motor vehicles perfectly and exhibit massive starting torque, often eliminating the need for any transmission.
Steam vehicle engines can provide near silent operation.
Compared to the IC engine and automatic transmission package seen today, the Rankin cycle engine can be more economical to produce either in mass or limited production.
As it operates at lower temperatures than the IC engines and does not require high speed to produce the torque and horsepower demanded, the steam engine system enjoys a long service life. Vintage steam cars are known that have not had major engine service for over forty years.
These are all important, science-based reasons why automotive companies are encouraged to revisit Rankine cycle engines as a power source for cleaner, more efficient, more fuel-flexible vehicles, with the power output needed to move the type of cars that the American public actually wants to buy.
POLLUTION CONTROL COMES NATURALLY TO THE RANKINE CYCLE ENGINE. The Rankine cycle engine is an external combustion engine, burning its fuel in a separate outside combustion chamber. By contrast, the internal combustion (IC) engine burns its fuel inside the cylinders. The constantly varying temperatures and pressures in the IC engine greatly influence the actual combustion process and the composition of the exhaust gasses. In the Rankine cycle engine continuous combustion is at a constant low pressure i.e., there are no explosions, no pressure peaks and with a long residence time for the fuel particles to burn completely in a pollution free manner. The actual burners are simplicity personified sheet metal constructions.
When properly designed, the combustion system of the Rankine cycle engine with absolutely no pollution control hardware provides the very best possible pollution elimination over any fuel burning IC engine. This very clean burning condition is accomplished in several ways. The combustion air pressure in the firebox is typically less than one pound per square inch compared to the hundreds of pounds pressure in the IC engine at the point of ignition and the fuel particles have a long residence time in the burner (combustion is a continuous controlled process) insuring complete and clean combustion. There are NO unburned hydrocarbons, NO soot emissions, NO CO traces and when bio fuel oils from plants or algae are used being carbon neutral there is NO excess CO2 production. Furthermore, if the combustion temperature is held down below 2300°F by means of secondary air admission into the firebox, NOx is NOT produced. None of these features harm or reduce the overall net cycle efficiency in any manner.
The natural clean burn of the steam engine is a major cost saving over the gasoline and Diesel IC engine. The need for the computer controlled systems for engine management, valve timing, automatic transmission management, ignition and fuel injection requirements in IC engines and exhaust system air injection, filters and converters all vanish in the steam car. One inspection under the hood of any new IC automobile will amply illustrate just how complex and costly all this pollution control and engine management has driven matters. For the long-term vehicle and truck owner, all this hardware and electronics translates into some eye watering repair bills down the line.
The steam car requires none of this hardware or electronic controls. It could not use them even if it had them.
New Diesel engines while very good with fuel consumption, very durable and providing high torque output, are now requiring involved, expensive and complicated exhaust converter systems to meet constantly evolving EPA pollution standards. These engines require the addition of special fluids and reactors to the exhaust stream to control the NOx, and converters and filters to handle the soot production.3 This addition, coupled with some intrusive mandates from the EPA to insure that this fluid system always operates, have added unnecessary high cost to the new vehicles that offer Diesel alternatives to the standard gasoline engine. Their new common rail fuel injection systems are computer controlled, adding more cost and potential reliability problems that are already being noted. Some data this author obtained about the Cummins engines suggests that new large interstate truck Diesel engines will require such pollution control additions to meet near term government mandates at a cost of up to $25,000 per engine, plus frequent and costly maintenance. This is simply not acceptable to truck owners.4
It is also noted that these government agencies are now actively considering mandating similar requirements for marine Diesels, railroad locomotives, farm, construction and industrial engines and even down to lawnmower sized engines. It appears that any Diesel engine is going to require expensive pollution control systems. As a result, some industrial Diesel engine manufacturers have stopped supplying these engines for truck use, as the cost of efficient NOx and soot pollution control devices for large engines has driven the cost of these beyond what their customers will accept. Caterpillar is one manufacturer who took this path in 2008.
THE TRUE FUEL FLEXIBILITY OF THE RANKINE CYCLE ENGINE. Talk of “flex fuel” IC engines by auto manufacturers and Government politicians is truly a misnomer, in point of fact an outright deception. What these engines offer the motorist is the ability to use certain alcohol blend fuels as a replacement for pure gasoline. Not only is this hardly flexibility, but the use of alcohol in today’s IC engines comes with a whole realm of new issues besides increased fuel consumption and loss of power, including:
The hygroscopic nature of alcohol has proved to accelerate corrosion in older automotive components and to seriously dilute lubricating oil resulting in excessive piston ring and valve guide wear. One reason today why alcohol is transported in tanker trucks and railroad tank cars and not by using existing petroleum pipelines, this tendency to absorb water.
Once a vehicle’s compression ratio is increased to take advantage of alcohols higher octane rating, it cannot again use straight gasoline again or destructive detonation will take place.
The fermentation part of producing alcohol for fuel usage from cellulous material creates substantial CO2, highly limiting the carbon-neutral benefits of burning this bio fuel in a vehicle.
Since formaldehyde is often used to prevent human consumption of ethanol, some very hazardous byproducts of combustion in the IC engine have been noted.
It has often been accurately reported that large scale fuel alcohol production is only commercially feasible providing that large farm corn growing and alcohol fuel production tax offsets and
Government subsidies are in place. This was done by the Bush Administration.
In January 2012, it was announced that Senator Feinstein sponsored and saw passed her bill removing the Government subsidy given to the alcohol producers. The eventual fallout from this has yet to be seen when the increased cost of producing this fuel is passed on to the eventual customer. What was not yet addressed was the mandate implementing the addition of alcohol to gasoline, nor the equally expensive subsidy given to the farmers to grow corn for use in automotive fuels. The Senators office responded by saying that these two costly subsidies are also to be eliminated.
These concerns and others about alcohol usage in passenger vehicles are addressed in additional detail later in this paper. Suffice it to say, however, that what the public has been conditioned to believe is fuel “flexibility” in their cars, is a fuel fallacy, a Government backed fraud. What is most unfortunate is that the general motoring public is totally ignorant about the fuel chemistry of alcohol and how it must be used in an IC engine and unable to see through this politically inspired smoke and mirrors tap dance.
Bio fuel oils from plant sources and algae offer a better fuel selection solution. Many of these fuels can be produced without impacting the food supplies and offer a high BTU value relative to alcohol. (19,500 vs. 8500 BTU/lb) The Diesel engine when burning these bio fuel oils also shows a neutral CO2 emission condition and retains the high net efficiency. However, as the Diesel cycle depends on a high compression ratio for the ignition phase and a resulting high combustion temperature, the NOx generation is a very serious matter. NOx is inherent with any Diesel cycle engine and unavoidable. Soot can be and is being controlled, although in old engines it may become a serious problem to keep using them.
These bio fuel oils when used in Diesel engines must be highly refined to eliminate any water or glycerin or serious and costly engine damage will be seen. The Rankine cycle engine does not have this requirement, only that any dirt be filtered out to prevent the burner nozzles from clogging up.
Diesel engines cannot use alcohol fuel and the spark ignited IC engine cannot use these bio fuel oils. This is hardly “flexible” from most educated people’s viewpoint. What is desired is a practical engine than can cleanly use any liquid fuel or varying mix of fuels without any compromise or adjustment. The selections available for this task however just got very small, microscopic in fact. Only the Rankine cycle steam engine and the Stirling cycle engine alone demonstrate this attribute.5
The Rankine cycle engine demonstrates true fuel flexibility than no gas or Diesel IC engine can attempt to match. Cyclone’s Schoell cycle engine can use any liquid fuel or gaseous fuel that can be supplied to the fuel pump. The company has tested: alcohol, acetone, gasoline, Diesel oil, heating oil, kerosene, vegetable oils, used waste motor oil, even reclaimed oil from the recent Gulf oil spill disaster, propane, natural gas and other fuels in its engines with no special added on control systems or modifications to the burner fuel delivery system or to the combustion chamber. This is simplicity personified when compared to any vehicle IC engine today. A major cost savings potential.
THE MODERN STEAM ENGINE CAN PROVIDE EQUAL FUEL ECONOMY TO IC ENGINES. In addition to the wide fuel capability, one feature of the Rankine cycle engine regarding fuel consumption must be considered. When the steamer is used in city driving, residual heat does the main job of maintaining the steam conditions for a modest period of time. When just puttering along, the burner is off most of the time only coming on for brief periods to maintain steam pressure and temperature.
In city traffic the Rankine cycle engine will enjoy better fuel mileage than when on the highway where the burner is on primarily all the time. With city driving the IC engine must consume fuel to keep running continuously so as to remain in operation. At these slow speeds the IC engine is showing its worst efficiency. Only at their full design power output do they exhibit high cycle efficiency.6
The Rankine cycle engine does have one efficiency hurdle and one operational hurdle that cannot be avoided. The first is the unavoidable thermodynamic loss from the heat required to vaporize water. This means adding 947 BTU/lb just to effect the phase change from liquid to gas, then rejecting that heat to the atmosphere in the condenser where the exhaust steam is changed back again into water. This process does not itself produce power and therefore is a total loss. For the competent engineer, this means that considerable attention must be paid to minimizing any other heat, fluid flow or friction losses in the system, and also utilizing the most efficient expander possible. Various regenerative heat exchangers plus the use of the best insulation against heat losses are of critical importance to such a system. As will be discussed subsequently, Cyclone’s Schoell cycle has accomplished this better than any known automotive steam engine in the past.
This loss occasioned the flurry of trying to find some alternate working fluid that would be satisfactory as a substitute for water. Except for the toluene used in many solar power plants, particularly in Israel by Dr. Tabor, use in a vehicle power plant came to a halt when it was discovered that these fluids disintegrated with high temperature (650°F+) and some produced some really hazardous byproducts. The other problem was their low specific heats compared to water, which meant a much larger pumping loss.
The second unavoidable problem is that water freezes at +32°F and that you cannot alter. This means that when designing the engine, the water inside the various components must be able to be drained into one common sump or tank. Then a small electric heater can prevent freezing, identical to the block heaters used in IC cars and trucks today. This however, is of little help when the vehicle is stopped on the road and electricity is not at hand. Using the battery will only get one a discharged battery in the morning when it comes time to start the vehicle up from cold.
One humorous quip by the famous Ettore Bugatti comes to mind at this point, when replying to an angry customer complaining how hard his new Bugatti was to start when it was cold: “Well, if you can afford a Bugatti, then you can afford a heated garage.” So much for him!!
The natural condition of turning off fuel combustion when in stop-and-go traffic means that with a steam engine system, the vehicle’s essential powered auxiliaries -- the power steering pump, the power brake vacuum pump, and the air conditioning compressor, must be kept running. When the steam car is stopped, so is the main engine. Thus, so would be the vital auxiliary systems too if they are driven off the vehicle engine. Some other solution has to be found. A situation that has vexed steam car developers since the beginning of the breed, particularly with rapid response “flash” steam generators.
Normally they are run off the main IC engine even when at idle. The steam generators water feed pump, electric generator and the condenser fan and vacuum pump can be intermittent, depending on what steam generator design is used. Having a reserve water capacity is a desirable feature now. The burner air blower and fuel pump must be independent and these are powered by an electric motor using the battery.
The auxiliaries and their drives must be as efficient as possible. All this means some very serious engineering expertise and experience is demanded when designing this entire auxiliary system.
It is also a necessity to provide the vehicle with really powerful disc brakes, as the steam engine does not provide engine braking like the usual IC engine does as it also has a transmission to assist where the usual EC engine does not have that in the drive line. Putting the main steam engine in reverse has been done and sometimes the result is broken engine parts scattered all over the street. Not advisable at all.
A practical solution with steam is using a separate steam driven auxiliary unit for these purposes, which has a great deal of precedent and practicality. The past history of steam cars has well illustrated the fact that some separate engine best drove the ancillary loads, although their steam consumption is a concern although manageable. 10% has often been quoted, although the convenience may override this extra steam demand and slight added fuel consumption. Recuperating the heat from this auxiliary unit exhaust steam is also a necessity for good efficiency. This decision requires most serious thought now, as the type and operating characteristics of the steam generator have a big influence on how the auxiliaries are powered. Serious battery demand and failure is well known in previous steam cars.
Packaging all the auxiliary loads into one steam driven unit with an electric motor assist at times is one solution that is well known. This entire subject is one very complicated problem and requires a competent and thorough energy balance determination and some very hard decisions before the selection is made.
STEAM ENGINES EXACTLY MATCH THE TORQUE REQUIREMENTS OF THE AUTOMOBILE. The modern IC engines are not self-starting from rest. They require some outside power source to put them into operation, previously the “Armstrong Starter” (aka the hand crank) or since 1912 the electric starter. Both also demand that when the vehicle is stopped or waiting in traffic some means of disconnecting the engine from the load is needed. Either a manual clutch or the torque converter that is found in the automatic transmission is the common means of accomplishing this today.
The torque and horsepower output of both IC engines are at minimum when only idling, so a multi-speed transmission is also mandatory. This is provided now in almost every vehicle by a costly computer controlled six, seven or now eight speed automatic transmission of considerable complexity.
Reversing the steam car is accomplished by changing the valve timing 180° and this means that no special reverse gearing is needed as the engine reverses itself. These features provide a major cost saving over any IC engine for vehicle use, as well as resulting in lighter and much less complicated drive train systems, which reduces the fuel consumption and maintenance costs.
In vivid and dramatic contrast to the IC engine, the steam engine produces maximum starting torque when the high-pressure steam is first admitted to the engine.7 Thus the torque is highest when first starting out and it often is a surprisingly massive amount, providing rather startling acceleration. Even with the vintage steam cars of yesterday this torque can and did amount to over 2,000 lb/ft. As expected, Cyclone’s Schoell cycle engines are also displaying this extremely high starting torque. Its 100hp “Mark V” model (currently undergoing dynamometer testing) boasts over 860 ft/lbs of torque and the larger 330hp “Mark VI” model (currently in the advanced design stage) is calculated to generate over 2600 ft/lbs of torque. The electric vehicle motor also exhibits high starting torque; but unlike the Rankine cycle engine, is not able to maintain such output due to heat buildup along with rapidly exhausting the battery.
The result of this high starting torque is that in most steamers no transmission is required, although a two-speed transmission with a neutral position has been shown to be beneficial. As with the old White steamers two speed rear axle, you didn’t have to use it to get going, but under some difficult situations like deep sand or mud or a very steep hill, it proved to be one of their best ideas. Today it is most useful in congested city driving and particularly if hills are also encountered, as in San Francisco.
It also eliminates a very serious problem with steam cars using forced circulation monotube steam generators with minimum water capacity, the popularly termed “flash boiler”. When negotiating such dense traffic conditions and add in perhaps a hill, starting the car consumes a lot of steam and thus water. As the engine is going very slowly, so are the water pumps when they are driven off the main engine. The result is quite often a dry and overheated steam generator and angry motorists that you have just blocked as the temperature control has shut off the fire you now have no steam pressure either. You cannot start a steam car by pushing it. The fad of using many very small diameter tubes in parallel in the steam generator greatly magnifies this defect in design philosophy. Such is most definitely not recommended.
Thus, a separately driven auxiliary system and a two-speed transmission with a neutral position in the modern steam car is a serious consideration. Pull off the road put it in neutral and build up the water supply again. Or better yet, design the system so this cannot happen in the first place. One solution that the White used was oversized water pumps, accepting the added power loss to drive them.
Or use a steam generator with a usable reserve of water, yet not actually a storage type of boiler, the Lamont. This design exhibits fast steaming identical to the monotube, drastically simplified control system demands, complete safety and a good reduction in the heating surface necessary and in the bulk and weight of the steam generator for a given output. An optimum design when one considers all aspects.
It is interesting to note that the better steam car builders ultimately went to a separately driven water source for their steam generators. The Series F Dobles, the Scott-Newcomb and the French Serpollet are good examples. The designer does have some choices.
THE ADVANCES OF THE SCHOELL CYCLE ENGINE. With all the benefits that Rankine cycle engines offer for automotive usage, why are they not being employed or even considered today, the obvious question the reader must ask himself. One of the reasons that will be considered further in the next section is the prevailing viewpoint of the automotive industry that the Rankine cycle system is not a proven practical solution in spite of past successes. This faulty and grossly distorted opinion has its roots in the failures of the Government sponsored Clean Air Car program between 1960 and 1985 and possibly with exposure to some antique steam car that was not having a very good day, coupled with a decided lack of expertise and any experience with these systems.
Steam car engineering is not for the faint of heart as it is a most seriously complex subject and demands a high level of expertise in many areas of thermodynamics, metallurgy and power engineering.
In the firm opinion of this author since he was deeply involved, the Clean Air Car episode tainted the steam engine for the automotive industry to such an extent that they refuse to consider it seriously today as a potential candidate. One cannot really blame them for this attitude, as only one successful and usable steam car ever emerged during that period and that one was a private construction for General Motors by the Besler Developments Corporation. Not that it was a shining example of advanced Rankine cycle engineering, it certainly was not; but used primarily old Doble technology, yet it worked and worked very well within it’s limitations and that was all that was asked from the car. That one was actually and faultlessly driven from Emeryville to Los Angeles and back twice, something that not one other car constructed during this episode could manage or even attempted. They were transported to various displays on flat bed trucks or trailers.
As one very senior Detroit executive told this author at a dinner some years ago: “We all watched the program with great care and interest, but with that total failure, as far as we are concerned the steam car does not exist.” Industry insiders also bring up the poor fuel mileage and unreliability of the vintage steam cars, which in truth were not all that bad when compared to the gas engined vehicles of those days and the relative costs and plentitude of kerosene (used in steamers) vs. gasoline sort of balanced things out. The White steamer was well regarded for its dogged reliability and dependability in those days.
There is a very persistent yet unproven view that has existed for many years that the General Motors Corporation deliberately, energetically and completely sabotaged this Clean Air Car program in collaboration with senior management of the EPA and DOE in Washington. One supportable suggestion was that G.M. corporate management was concerned that their vast and vested interests and funding of IC engine development and production would be in serious danger should the Rankine cycle engine be adopted en mass and even worse, possibly mandated by Government. What has also been exposed is that behind this stand on new steam engine development, was the firm management view that it was a fuel wasteful, unreliable and unsatisfactory power source for the automobile and their position was that it never could be usable. Completely ignoring the good success some steamers had in the early days of the automobile. This was totally a deliberate falsehood based on total ignorance of improved systems and an unwillingness to even learn or investigate and primarily for protecting existing corporate investment in their gasoline engines and ancillary industries.
It should be said in all honesty that in that period and for many reasons, the Rankine cycle power source was not really commercially competitive with any IC engine with the one exception that it could burn its fuel in a clean manner, the prime goal of that program. That was not in dispute, everything else was.
While clean burning of the fuel was accomplished with this program, another Government demand was added later that put the final nail in the steam car coffin, the efficient use of fuel. The trigger was that “oil crisis” of about 1972 or so and phony or not, it caused a great uproar and a generally new way to look at the automobile. The steam car systems of that era burned twice as much fuel as their IC competition, even though they could burn a cheaper fuel than gasoline. When fuel economy entered the picture the steam car idea died, no one needed to attack it any further. From any commercial aspect, the steam car was indeed a dead issue.
It may be said that the underlying reason why steam is so thoroughly rejected by the auto industry now is that basically in our modern world they do not know anything about it. Certainly management, engineering staff and the Board members know what a steam engine is, restored locomotives, toy engines and restored vintage steam automobiles at the many public concours and tours demonstrate that a steam engine exists; but it is postulated that in fact none of them really know the subtle and hidden aspects on what does or does not exist in a really efficient and usable steam vehicle power source. With their closed minds and prevailing attitude, it also appears they refuse to learn. Only a potent demonstration car could perhaps alter this thinking.
Today with the Cyclone engines high cycle efficiency, plus the global warming and home produced fuels situation, that picture has indeed changed again and such a vehicle could be produced.
General Motors did commission two steam cars during this period. The SE-101 was their own conversion of a Pontiac and the SE-124, the converted Chevrolet sedan by the Besler Corporation which the author helped build. Corporate engineering insiders did mention that the prime reason for these two cars was so that General Motors could say: “Well, we built two of them, we tried and the results were not good, so we do not support further work on steam cars. It is not usable.” A gross distortion as the Besler conversion did work well within its limits. Both cars still exist although are not running as of this writing.
The author must confess that the hopes and chances of any wholesale conversion of the auto industry to Rankine cycle power is almost guaranteed to fail. The vested interests of Corporate management are directed to company and stockholder profit and such a conversion would cause great concern in the motoring public, not to mention panic in many Board Rooms, as to the success and usability of steam as a prime motive power today. Detroit will not touch steam in any manner. Perhaps a “clean air” tax incentive or buyer cost offset could be of assistance here, identical to the one given the battery electric cars and based on lack of pollution by the vehicle itself. Or possibly just constructing such a car or cars, then having them publically demonstrated and shown that steam is indeed a viable power source today could spark some public interest.
However, what is potentially possible as an introductory automotive market, quite similar to the introduction of battery electric cars in the past five years, would be as a special model like the top end Callaway Corvette or AMG Mercedes-Benz, done by an outside firm. Or, as an optional conversion power source by some specialty firm for those that would want it for the splendid driving pleasures and performance capability steam well demonstrates.
The other quite probable scenario would be for the power system manufacturer (Cyclone) to team with a good specialty sports car kit maker (Factory Five or E.R.A.) and introduce the engine that way with a high priced exclusive high performance GT vehicle.
There exists at the present time a very large, active and wealthy group of automotive collectors and enthusiasts that spend hundreds of thousands (millions often) of dollars for the finest collector and GT cars as the recent (2011) auctions well demonstrate. This niche market would be the customer base for a new limited production GT steam powered car. The market currently populated by the Ferrari, Bugatti Vyron, Lamborghini, McLaren, Aston Martin, Porsche, Jaguar, Mercedes-Benz AMG “Black” models and other similar super expensive limited production cars with breathtaking performance.
One must most definitely not ignore the huge interstate truck market, as their Diesel engines are receiving new negative rulings in Washington. This is also being seriously considered to extend to the railroad motive power sources too. The railroads are still the most efficient and cost effective way to move large amounts of goods long distances in the United States. They are being pressed to clean up their Diesel engines by Government mandate and the nation is not yet crisscrossed with overhead wires for electric locomotives and most likely never will be. The cost and lack of suitable power sources and distribution network for this would be the impediment. In spite of the delusions by some politicians and instant utopia demanding environmentalists.
One may easily envision a 2,000-4,000 hp Cyclone engine-generator power car that can be coupled in multiples behind the locomotive depending on the size of the train required, similar to what is done today with the Diesel power cars only much quieter, with a longer service life between overhauls and at reduced cost. Again, now burning clean bio fuel oils and eliminating the pollution.
This change by Government mandate is also being seriously considered to be expanded to take in city buses and delivery trucks, forklifts, yachts and all other Diesel powered industrial and farm equipment, all of which may be advantageously powered by the Cyclone steam engine.
Modern steam car projects of worth have been few and far between. In 1974, SAAB created a 9-cylinder axial steam engine, a unaflow design with a variable cut-off control in the rotary valve that was geared to run at 3000 rpm at 90 mph. Despite being heralded by the U.S. and considered by SAAB as worth continuing development of this engine, the project was apparently shelved in the early 1980s. In 2005, BMW announced a steam-powered auxiliary drive called the Turbosteam that used waste heat from the exhaust gases and the cooling system from the gasoline engine as its power source. In tests with a 1.8 liter, four-cylinder engine, the Tubosteam reportedly reduced fuel consumption by 15% while generating nearly 14 additional HP. Claims that then were observed with a cautious and very questioning eye. In these early reports, BMW claimed that the system needed more development, and their long-term goal was to have it in volume production within ten years. Finally, in 2008, Honda announced the development of a similar concept Rankine cycle co-generation unit to power a hybrid engine, taking heat from the exhaust to recharge the car’s batteries. Honda reported that low efficiency and high cost of this prototype did not yet warrant placing the system into a production vehicle. Nothing more was heard from either company. The point that was subsequently learned via some intense back door snooping was that neither company knew enough about the advanced Rankine cycle technology nor especially the past history to make a practical go of it. They depended on only the theoretical considerations and not any practical ones. All were infected with the idea that stacking energy conversion systems in series was a good idea.
This author challenges the automotive industry to revisit the Rankine cycle engine as an alternative to IC engines and as a more practical and readily producible alternative to electric-hybrid vehicles. In particular, the Schoell cycle engine may have all the requirements needed to make a steam powered vehicle a success today. The lack of interest by the entrenched auto industry is notable in its total silence so another way must be used to open the door for this power source.
Three such areas of improvement employed by Cyclone to make its Rankine cycle steam engine which they describe as a “heat-regenerative engine” in Cyclone’s patents8 – competitive to the gasoline or Diesel engine for use in automobiles exist, which also addresses the concerns expressed previously by SAAB, BMW and Honda, are:
Major increases in the power density are needed to even consider it. Done.
Vastly improved net cycle efficiency at all speeds and loads is absolutely essential. Done.
Dramatically updated packaging, making the power plant lighter, more compact and less expensive to produce. Done.
Each of these areas is explored in more detail below.
INCREASED POWER DENSITY. Improvements to power density means substantially increasing the push on the piston head during the power stroke, a higher operating pressure, also known as increased brake mean effective pressure (BMEP). With a given bore and stroke this increases the developed horsepower and torque. Otherwise, one needs to increase one or both of them to give a much larger displacement and thus a larger and heavier engine, which is undesirable. Another solution is to drastically increase the speed with which the engine operates, but this is not ideal from a wear, reliability and noise standpoint and with a steam engine, considering the torque and horsepower graphs vs. rpm, totally unnecessary and unwanted for vehicle use.
The steam car enjoys a very unique set of operating features that are most useful in real world conditions.
The historical steam car engines ran between about 200 psi and 1200 psi. To increase the BMEP, Cyclone’s Schoell cycle uses steam pressures up to 3200 psi, termed “super critical.” The use of super critical steam pressure increases the power density of the engine as regards to horsepower per pound and per cubic foot of overall size to the desired level. The desired goal is the highest practical drop in pressure between the inlet valve closing and the exhaust ports venting the exhaust steam, which the Schoell cycle is able to achieve by using these higher operating pressures and very short steam admission timing at the higher speeds thus giving this most desired high expansion ratio.
However, there is a balance here where a modest increase in expander displacement and a somewhat reduced operating pressure and running speed may evolve into a well rounded, reliable and quiet automotive system. The high steam temperature that the Cyclone uses is essential to generating this higher total net cycle system efficiency. The balanced approach is most certainly recommended.
INCREASED NET CYCLE EFFICIENCY. Cycle net efficiency is the measure of how much work an engine can produce from using a given amount of fuel. Improvements to cycle net efficiency in a steam engine can be accomplished by increasing the temperature of the steam entering the engine or expander. The highest practical inlet steam temperature vs. the lowest practical exhaust temperature is the goal. This provides a means of increasing the expansion ratio per stroke of the piston, which is the prime desired criterion. This assumes that piston ring leakage and heat losses are kept to the absolute achievable minimum throughout the entire system.
The old steam car engines were restricted in terms of steam temperature and therefore efficiency, by the need to inject special cylinder oil to lubricate the piston rings and valves. Exceed a temperature of 550ºF to 650ºF and the oil became carbonized and caused high maintenance demands in keeping the steam generator coils clean, the condenser washed out at frequent intervals and draining accumulated oil from the water tank. This abrasive carbon also caused rapid piston ring wear.
With special materials and specific points of lubrication throughout the system, Cyclone’s Schoell cycle engine is able to use its operating fluid, de-ionized water, as the lubricant for the piston rings, crankshaft bearings and other moving components of the engine. Successfully eliminating cylinder oil is the single major advance in the technology. By eliminating motor oils and using water, Cyclone’s Schoell cycle engine is able to use steam temperatures up to 1200-1400°F, the highest possible and usable working temperature today with most modern metals.
The successful elimination of injected oil as a lubricating agent is simply the most dramatic and major improvement in the Rankine cycle vehicle engine seen in the past ninety years. Without this innovation, the Cyclone engine would never have surpassed the efficiency of previous steam car power systems. In all honesty, it must be said that the best steam cars of the past, the White and the Series E and F Dobles, fuel mileage was quite comparable to other vehicles in their respective classes. The Doble against the P-I Rolls-Royce, Duesenberg J, Hispano-Suiza H Series, Cadillac V-16, Packard 12 or Lincoln Model L. The White against others of its same size and weight.
Of course, substantial research and development was needed to accomplish this feat; but early durability demonstrations have proved that the Cyclone team has done it successfully.
The Cyclone team has also employed other features with good effect in raising the cycle net efficiency of the Schoell cycle. Paying close attention to heat losses with improved insulation and heat barriers and using high efficiency heat exchangers in the exhaust side of the engine, combustion chamber exhaust vents and around the cylinder steam exhaust ports to recuperate otherwise wasted heat back into the cycle, has proved to be very beneficial, raising overall system thermal efficiency by as much as 8%.
To date the net reproducible cycle efficiency of the Cyclone engine is above 28%, with 31.5% efficiency achieved on the company’s small two-cylinder engine, and 35% confidently predicted to be achieved on the larger 6 cylinder “Mark V” model in the immediate future on the dynamometer.
There are serious losses when steam engines are greatly reduced in size by heat losses and piston ring and valve leakage and much finer operating clearances are demanded and seldom seen, one can only go so far in reducing the size of the engine itself. The larger the better is the norm. These efficiency figures already make this Cyclone Rankine cycle engine competitive to the vehicle gasoline engine. The best Diesel engines show about 35-38% and that is hard to beat. However, this number is suspect as nothing was reported if the calculations included the automatic transmission losses or not. If an automatic transmission is part of the system, then the Cyclone alternative is an even match to the Diesel today, with continued improvements being seen by the Company as testing progresses and detail changes are incorporated into the designs.
It MUST be understood that both IC engines reach their peak operating net cycle efficiencies at their top designed rpm. At low speeds or part loads the fuel consumption rate is seriously worse.
WEIGHT AND SIZE REDUCTION. The historical version of the automotive steam system has always been a collection of heavy and big components tied together by a maze of plumbing and fittings. The Schoell cycle engine was designed from the start as an integrated one-piece unit of impressive compactness. Every single component that makes up this Rankine cycle engine is packaged into one neat unit, which should easily fit where the present IC engine is located in the vehicle. The only outside connections other than gauges are the fuel line, the cable supplying electric power to the combustion and condenser cooling blowers, plus the forward-reverse lever, the throttle actuator and the output shaft. The moving parts count in Cyclone’s engine is drastically reduced when compared to any known IC engine. Compared to the present automotive IC engine and automatic transmission, the complete Schoell cycle engine is literally simplicity personified as the parts layout at the end of this paper well illustrates.
Cyclone’s 100hp automotive model engine, the Mark V, weighs a mere 350 lbs. dry, and is 28” in diameter and 24” high. These weight and size dimensions include the system’s combustion chamber, water tank, steam generator, expander and condenser, all of which are circular in design to achieve higher heat exchange rates in the smallest possible space. In sum the entire engine.
The use of multi parallel circuits in parts of the steam generator in place of one long single tube allows the Schoell cycle to increase the heat transfer rate by increasing the flow velocity and thus the production of steam per square foot of heating surface per hour. However, the designer must take extreme care with the control system and water feed to each circuit so that tube burnout due to water starvation or surging does not occur in any one coil. Extended surface steam generator tubing with fins would also greatly increase the evaporation rate per square foot of heating surface and per linear foot of the tubing in the steam generator, allowing even greater reduction in size and less weight. Perhaps this is a subject for the ongoing development program of the Cyclone engine.
The control of the steam pressure and steam temperature has been a vexing problem with some earlier steam car systems. Early addition of electric controls to the Doble and other steam cars in the 1920’s only managed to add some unreliability and maintenance issues. The Schoell cycle engine is able to employ simple relay logic controls fed by thermocouples and a pressure switch to control the water feed and burner operation, or the simplest of microprocessor control modules. The cost savings here with this engine are a major improvement over the highly complex integrated computer systems now employed with the IC gasoline engine in vehicles for engine, vehicle dynamics behavior, transmission and fuel injection management.
The noted cost reductions over any hybrid, plug-in-electric or other such pasted on additions to the gasoline engine are also going to be a major savings in the production costs over those vehicles.9