The Forgotten Engine

By

Robert Orsello

Foreword

The following is a concept for a more efficient engine. In essence it is a modern variation of a very old engine concept invented by John Ericsson and patented in 1833.

Premise

The principle of a heat engine is to add heat and extract shaft work.

Every engine has a maximum temperature and pressure at which it can operate called the ceiling temperature and pressure respectively. (Think Melting point and bursting point)

Conventional heat engines such as Otto and Diesel operate on a four phase process which completes a repeatable cycle.

In this process, a unit volume of air is compressed, heat is added to create energy content, the heated unit of compressed air is expanded and made to do shaft work, then the mostly expanded air is exhausted.

Drawbacks of a conventional Heat Engine

About ¼ of fuel is consumed on compression

Ceiling Temperature limits compression ratio

There is incomplete expansion on power-stroke

There is no Recycling of heat

Galt Cycle™

In an effort to develop a more efficient heat engine, A new thermodynamic process is proposed which is intended to eliminate the efficiency drawbacks of a conventional engine. This process does not run in steady state. It requires a charge time and has a fixed operating time.

The four phases to the Galt Cycle are:

Disassociated Isothermal Compression

Isobaric Heat Addition

Isothermal Working Expansion

Isobaric Regenerative Cooling

Disassociated Isothermal Compression

In this application, compression is completed separate to and in advance of engine operation, stored in an onboard container for use during operation and used in metered packets.

This compression is completed with an Isothermal process, which yields a very high compression ratio while keeping the temperature of the compressed air at room temperature. In this case, compression ratio is only limited by the Ceiling Pressure of the engine design.

It is common knowledge that when a gas is compressed, it heats up. In fact a Diesel Engine operates on this fact. Yet the interesting aspects to compression without heating are that a much higher compression ratio can be attained and a lower initial temperature is established.

Compression is good. The more compression achieved the better. Higher compression increases the power density of an engine and its overall efficiency. The compression in a conventional engine is limited because the air heats up when it is compressed. Too much compression can produce extreme temperatures that exceed the engine’s Ceiling Temperature.

Likewise, the lower the initial starting temperature and the greater the heat input, the more efficient the engine. The principle of a heat engine is to add heat and get work out. The more heat added, while remaining at or below the Ceiling Temperature, the better.

The immediate advantages of Disassociated Compression are that energy used to complete the compression process is not derived from auto fuel, nor does it rob ¼ of the engine power. Very high compression ratio can be used to increase engine power and overall efficiency. A Low inlet temperature allows for greater heat addition during combustion, yielding an increased efficiency.

Isobaric Heat Addition

During engine operation a packet of air is extracted from the Charge Canister at ambient temperature and maximum ceiling pressure in a metered volume. At this point, maximum heat is input until the temperature of the packet is elevated to the engine’s thermal limit or Ceiling Temperature.

Since the packet was at the maximum pressure of the engine prior to heat addition, heating is done with an isobaric process, which means, the pressure remains constant during heating. Under these conditions, the volume of the packet expands proportionately to the increase in temperature, which is also a proportional increase in its potential energy or ability to do work.

Isothermal Working Expansion

The Working Expansion process is one which extracts work from the heated, pressurized packet, by allowing it to expand and do work. Imagine the heated packet contained behind a piston, ready to do work by pushing the piston to the right as it expands. While the packet expands its pressure drops. The packet will continue to push and expand, until its pressure is equal to the ambient pressure outside of the piston.

Once again, it is common knowledge that an expanding gas cools down. This is called Isentropic Expansion and is the process used in conventional heat engines. If our packet of air begins working expansion at the ceiling temperature and pressure of the engine, it will complete the working expansion at a much lower temperature, and a pressure near ambient. Ironically, as it is expanding, it is cooling, which is causing it to contract. The contraction from cooling during the expansion is counter productive and reduces the engine fuel efficiency.

An expanding gas is a sponge ready to absorb heat. If heat is added during expansion and the temperature is maintained, then the expansion process is called Isothermal. In the method presented here, heat is added to the packet of air while it is expanding, to counteract the cooling phenomenon. This not only gives a second opportunity for heat addition, but is the largest direct contributor of added heat toward work out.

Isobaric Regenerative Cooling

Because the Working Expansion phase is Isothermal, the exhausted air at completion will be at the maximum ceiling temperature of the engine. With this high temperature exhaust is the opportunity for heat reclamation, or regeneration.

For this method, there are two instances where this exhaust heat can be reapplied. If we go back to our original packet, prior to Isobaric Heat Addition, we have a specific amount of air which is at Ambient (outside) temperature, waiting to be heated to the Ceiling Temperature. At this same moment, exists the same amount of air, which was just exhausted from the previous cycle, and is already at the Ceiling Temperature.

If you allow these two amounts, one cold and one hot, to heat share, then the simple and direct result is that the temperature of the exhaust and the packet will equalize in the middle. This is called regenerative preheating, and essentially half of the excess heat energy in the exhaust is pushed back into the system, greatly increasing the fuel efficiency, since this is heat that was not supplied by fuel.

It is important to note that the process of regeneration does not work well in a conventional heat engine because the compression phase heats the air to a point that it does not accept much heat energy from the exhaust, and the short duration of time between compression and combustion, gives the compressed air little time to absorb heat.

As mentioned, there are two instances where the exhaust heat can be reclaimed. At this point, half of the heat has been reclaimed and the new exhaust temperature is (Tc+Ta)/2, or half way between the Ceiling Temperature and Ambient.

Remember that the Charge Source is a canister filled with compressed air, which is initially at Ambient Temperature before the engine process begins. As packets of air are removed from the canister to sequence through the three phases of our operational engine, the canister pressure drops and its contents begin to cool. Everyone has seen frost form on a propane tank that has been used for an extended period of time. This is the same Isentropic cooling phenomenon that was counteracted during working expansion. If no heat were added to the canister, its temperature would quickly drop below ambient and continue down below zero degrees.

To keep the canister temperature from dropping down below ambient, the remaining exhaust heat is applied to the canister.

For maximum efficiency gain, heat can be added to the canister, not only to counteract the Isentropic cooling effect, but to gradually increase the canister temperature above Ambient with Isometric heating (constant volume).

With each packet of air that is extracted, pressure in the canister drops slightly. By heating the air in the canister, the pressure can be held to the ceiling pressure. For maximum efficiency, this compensation heating should be used to maintain the ceiling pressure, up to the point that the canister reaches its ceiling temperature.

Engine Operation

Operation of this engine begins with a fully charged canister, which delivers a packet of air at the ceiling pressure. The packet is preheated with regenerative exhaust heat, and finished with passive heating to achieve Ceiling Temperature prior to the Working Expansion. Fuel is then added to the packet and the packet fuel mixture is burned during the Working Expansion, to add the necessary heat for Isothermal Expansion. The exhaust is then cycled back to the system for the two phase regenerative heating of subsequent packets and the charge canister.

While the engine is used and the canister begins to discharge, heat is added to the canister not only to counteract the natural cooling effect, but to raise its temperature so as to maintain Ceiling Pressure.

At some point, as packets are removed, the pressure in the canister will steadily drop. As the pressure drops, the packet size delivered to the engine for heat addition and working expansion must increase. In this way, more constant power output can be observed at the shaft and the efficiency can be maintained.

The engine will operate in this fashion until the charge in the canister is exhausted.

The overall concept of this engine is to achieve and maintain an operational core temperature which is at the mechanical thermal limit of the engine. The amount of fuel combusted in the engine is metered to maintain the core temperature. The engine itself is insulated to keep the heat within, thereby reducing the amount of fuel required to offset the passive radiant heat loss. In this design, the only heat which should leave the system is contained in the final exhaust product.

With the method presented here, a modified version of the dynamic Ericsson Cycle of: Isothermal Compression, Isobaric Heating, Isothermal Working Expansion and Isobaric Regenerative Cooling, can be attained for a period of time determined by:

1.) The volume and initial pressure of the charge canister.

2.) The Ceiling Temperature of the engine.

3.) The work output required.

In a basic example, a 10 cubic foot container with a ceiling pressure of 5000 psi and a Ceiling Temperature of 2000 Degrees F could deliver about 90 hp hrs, means that it could deliver 90 hours of 1 hp, 15 minutes of 360 hp, or any combination therein.

A typical vehicle traveling at highway speed might use ~15 hp. In this case, the vehicle could travel for 6 hours and reach over 300 miles on one full charge.

Overall Efficiency Improvement

It is not the intent of this paper to derive and explain the theoretical efficiencies which are indicative of the Galt Cycle, however a sister paper is available to do just that. One can also conduct research on the Ericsson Cycle for further investigation. The efficiency is a factor of the Ceiling Pressure and Temperature used.

In the parameters of operation for an engine, as used in the example from above, the theoretical Overall Efficiency is in excess of 60%. Friction and imperfect cycle operation would obviously reduce the actual efficiency. Calculations predict an engine efficiency that exceeds 40%. Conventional engines operate between 25% and 30% efficiency.

A side note to this efficiency is that it represents the overall efficiency, which includes the work necessary to create the pre-charged canister. Overall efficiency should not be confused with fuel efficiency.

For this engine, the run time, fuel efficiency is strictly the work out / fuel consumed.

The theoretical fuel efficiency for this engine is over 80%, with an expected actual fuel efficiency of ~58%. This is a significant increase to the fuel efficiency of a conventional engine at 25% to 30%, as stated earlier.

Reduced weight and footprint without sacrificed power

The very exciting aspect of this engine design is that large power and torque can be delivered from the charge canister if necessary. A vehicle powered with this engine would not suffer from poor acceleration, yet it would still deliver excellent fuel economy. No starter would be required and when the vehicle is not moving, the engine would not be running.

In comparison, a conventional Hybrid engine uses an electric motor, batteries, internal combustion engine, starter cooling system and fuel tank. This could be replaced with a single engine, charge canister and reduced fuel tank for a significant space and weight reduction.

Improved Fuel Efficiency

The fuel which is carried onboard is used solely to create power to the wheels. Unlike a conventional heat engine where ~1/4 of the fuel consumed is to execute the compression stroke. Clearly energy still has to be used to pre-compress the charge canister, but this is not accomplished during operation with onboard fuel.

Off-Peak Electricity for Compression is less expensive

The compression phase requires the same amount of work whether it is conducted real time, using the onboard fuel and engine power, or in advance, using Off-Peak grid electricity with an efficient electric compressor. The Off-Peak advantage here is cost.

As comparison:

1.) A conventional engine burning one gallon of gas can produce about 11.6 kwh of energy.

2.) An electric motor uses about 12 kwh to produce 11.6kwh of energy.

One Gallon of Gas = 12Kwh of Off-Peak Electricity

$3.50 $1.08

The benefit of using Off-Peak electricity to execute compression is 1/3 the fuel cost with less resultant pollution.

Calc:

[ Gas weighs about 6 lbs. and contains about 22,000 btu/lb of potential heat energy. With a conventional heat engine operating at 30% efficiency, one gallon of gas can deliver 6*22000*.3 = 39600 btu work output = 11.6 kwh.

An electric motor, using grid electricity operates at 97% efficiency and would use 12 kwh to accomplish the same task.

]

Applications

Rechargeable Vehicle Engine

The merits of using the Galt Cycle as an automobile engine have been shown. Further gains of the system could employ back compression for braking, which would also add heat to the system and push charge back into the canister.

Onboard compressed air is inherently much safer than a comparable hydrogen tank. If a tank of compressed air ruptures, air discharges out of the puncture or fracture and the tank gets very cold, it does not explode.

Solar Power Generation

The Galt Cycle is readily adaptable for Solar Power Generation, in that the sun only shines a fraction of the day.

During the night, Off Peak grid electricity could be used to build a pre-charge. In the day, the engine would run, to not only return the energy stored from the night before, but efficiently convert the solar heat from a concentrator or flat plate collector into Peak electricity by means of a generator.

In one application, the charge storage container could be flat, thin and black; accepting the solar heat directly like a flat plate collector, to offset the Isentropic Cooling effect as packets were removed and converted to work out.

Collector Panel Area would be highly minimized because of the high efficiency of the daytime conversion.

Personnel Power and Cooling

An awake active male produces about 50 watts / hour of heat. This heat is used to maintain body temperature. The body also has mechanisms to shed excess heat by vessel constriction and perspiration. If an active human body is restricted from the dissipation of excess body heat with the uniform on a fireman, as an example, then overheating can occur.

A vest could be designed which used the body heat of an active human to employ the Galt Cycle for personnel cooling and power generation. If the subject wore a specially designed vest to access core body heat in the chest, back and neck, excess heat could be absorbed into the charge canister, while driving a small engine to produce electric power for hand held or field carried electronics.

If the goal were to dissipate 40 watts / hour, and the efficiency of a small Galt based Engine was 50%, then 20 watts / hour of electricity could be produce and 40 watts / hour of cooling would take place.

For perspective, 20 watts / hour would run a small laptop. To deliver 20 watts of electricity and 40 watts of cooling for 10 hours, the engine would need to produce a total of 200 watts, which extrapolates to a charge canister volume of: .15 cubic feet and weigh 3.8 lbs at full charge of 5000 psi.