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How to make a Stirling engine at home? Which Stirling Engine Has the Best Design for Maximum Efficiency Making Your Own Stirling Engine

It replaced other types of power plants, however, work aimed at abandoning the use of these units suggests an imminent change in leading positions.

Since the beginning of technological progress, when the use of engines that burn fuel inside was just beginning, their superiority was not obvious. Steam machine, as a competitor, contains a lot of advantages: along with traction parameters, it is silent, omnivorous, easy to control and configure. But lightness, reliability and efficiency allowed the internal combustion engine to take over the steam.

Today, issues of ecology, economy and safety are at the forefront. This forces engineers to throw their forces on serial units operating on renewable fuel sources. In the year 16 of the nineteenth century, Robert Stirling registered an engine powered by external heat sources. Engineers believe that this unit is able to change the modern leader. The Stirling engine combines efficiency, reliability, runs quietly, on any fuel, this makes the product a player in the automotive market.

Robert Stirling (1790-1878):

Stirling engine history

Initially, the installation was developed with the aim of replacing the steam-powered machine. Boilers of steam mechanisms exploded when the pressure exceeded the permissible norms. From this point of view, Stirling is much safer, functioning using a temperature difference.

The principle of operation of the Stirling engine is to alternately supply or remove heat from the substance on which work is performed. The substance itself is enclosed in a closed volume. The role of the working substance is performed by gases or liquids. There are substances that perform the role of two components, the gas is transformed into a liquid and vice versa. The liquid-piston Stirling engine has: small dimensions, powerful, generates high pressure.

The decrease and increase in the volume of gas during cooling or heating, respectively, is confirmed by the law of thermodynamics, according to which all components: the degree of heating, the amount of space occupied by the substance, the force acting per unit area, are related and described by the formula:

P*V=n*R*T

  • P is the force of the gas in the engine per unit area;
  • V is the quantitative value occupied by gas in the engine space;
  • n is the molar amount of gas in the engine;
  • R is the gas constant;
  • T is the degree of gas heating in the engine K,

Stirling engine model:


Due to the unpretentiousness of the installations, the engines are divided into: solid fuel, liquid fuel, solar energy, chemical reaction and other types of heating.

Cycle

The Stirling external combustion engine uses a set of phenomena of the same name. The effect of the ongoing action in the mechanism is high. Thanks to this, it is possible to design an engine with good characteristics within normal dimensions.

It should be taken into account that the design of the mechanism provides for a heater, a refrigerator and a regenerator, a device for removing heat from the substance and returning heat at the right time.

Ideal Stirling cycle, (diagram "temperature-volume"):

Ideal circular phenomena:

  • 1-2 Change in the linear dimensions of a substance with a constant temperature;
  • 2-3 Removal of heat from the substance to the heat exchanger, the space occupied by the substance is constant;
  • 3-4 Forced reduction of the space occupied by the substance, the temperature is constant, heat is removed to the cooler;
  • 4-1 Forced increase in the temperature of the substance, the occupied space is constant, the heat is supplied from the heat exchanger.

The ideal Stirling cycle, (pressure-volume diagram):

From the calculation (mol) of a substance:

Heat input:

Heat received by the cooler:

The heat exchanger receives heat (process 2-3), the heat exchanger gives off heat (process 4-1):

R – Universal gas constant;

CV - the ability of an ideal gas to retain heat with a constant amount of space occupied.

Due to the use of a regenerator, part of the heat remains, as the energy of the mechanism, which does not change during the passing circular phenomena. The refrigerator receives less heat, so the heat exchanger saves the heat of the heater. This increases the efficiency of the installation.

Efficiency of circular phenomenon:

ɳ =

It is noteworthy that without a heat exchanger, the set of Stirling processes is feasible, but its efficiency will be much lower. Running the set of processes backwards leads to a description of the cooling mechanism. In this case, the presence of a regenerator is a mandatory condition, since when passing (3-2) it is impossible to heat the substance from the cooler, the temperature of which is much lower. It is also impossible to give heat to the heater (1-4), the temperature of which is higher.

The principle of the engine

In order to understand how the Stirling engine works, let's look at the device and the frequency of the phenomena of the unit. The mechanism converts the heat received from the heater located outside the product into a force on the body. The whole process occurs due to the temperature difference, in the working substance, which is in a closed circuit.


The principle of operation of the mechanism is based on expansion due to heat. Immediately prior to expansion, the substance in the closed circuit heats up. Accordingly, before being compressed, the substance is cooled. The cylinder itself (1) is wrapped in a water jacket (3), heat is supplied to the bottom. The piston that does the work (4) is placed in a sleeve and sealed with rings. Between the piston and the bottom there is a displacement mechanism (2), which has significant gaps and moves freely. The substance in a closed circuit moves through the volume of the chamber due to the displacer. The movement of matter is limited to two directions: the bottom of the piston, the bottom of the cylinder. The movement of the displacer is provided by a rod (5) which passes through the piston and is operated by an eccentric 90° late compared to the piston drive.

  • Position "A":

The piston is located in the lowest position, the substance is cooled by the walls.

  • Position "B":

The displacer occupies the upper position, moving, passes the substance through the end slots to the bottom, and cools itself. The piston is stationary.

  • Position "C":

The substance receives heat, under the action of heat it increases in volume and raises the expander with the piston up. Work is done, after which the displacer sinks to the bottom, pushing out the substance and cooling.

  • Position "D":

The piston goes down, compresses the cooled substance, useful work. The flywheel serves as an energy accumulator in the design.

The considered model is without a regenerator, so the efficiency of the mechanism is not high. The heat of the substance after work is removed into the coolant using the walls. The temperature does not have time to decrease by the required amount, so the cooling time is extended, the motor speed is low.

Types of engines

Structurally, there are several options using the Stirling principle, the main types are:


The design uses two different pistons placed in different contours. The first circuit is used for heating, the second circuit is used for cooling. Accordingly, each piston has its own regenerator (hot and cold). The device has a good power to volume ratio. The disadvantage is that the temperature of the hot regenerator creates design difficulties.

  • Engine "β - Stirling":


The design uses one closed loop, with different temperatures at the ends (cold, hot). A piston with a displacer is located in the cavity. The displacer divides the space into cold and hot zones. The exchange of cold and heat occurs by pumping a substance through a heat exchanger. Structurally, the heat exchanger is made in two versions: external, combined with a displacer.

  • Engine "γ - Stirling":


The piston mechanism provides for the use of two closed circuits: cold and with a displacer. Power is taken off a cold piston. The displacer piston is hot on one side and cold on the other. The heat exchanger is located both inside and outside the structure.

Some power plants are not similar to the main types of engines:

  • Rotary Stirling engine.


Structurally, the invention with two rotors on the shaft. The part performs rotational movements in a closed space cylindrical shape. A synergistic approach to the implementation of the cycle has been laid. The body contains radial slots. Blades with a certain profile are inserted into the recesses. The plates are put on the rotor and can move along the axis when the mechanism rotates. All the details create changing volumes with phenomena taking place in them. The volumes of the various rotors are connected by channels. Channel arrangements are offset by 90° to each other. The shift of the rotors relative to each other is 180°.

  • Thermoacoustic Stirling engine.


The engine uses acoustic resonance to carry out processes. The principle is based on the movement of matter between a hot and a cold cavity. The circuit reduces the number of moving parts, the difficulty in removing the received power and maintaining resonance. The design refers to the free-piston type of motor.

DIY Stirling engine

Today, quite often in the online store you can find souvenirs made in the form of the engine in question. Structurally and technologically, the mechanisms are quite simple; if desired, the Stirling engine is easy to construct with your own hands from improvised means. On the Internet you can find a large number of materials: videos, drawings, calculations and other information on this topic.

Low temperature Stirling engine:


  • Consider the simplest version of the wave engine, which requires tin, soft polyurethane foam, disk, bolts and paper clips. All these materials are easy to find at home, it remains to perform the following steps:
  • Take soft polyurethane foam, cut a circle two millimeters smaller than the inner diameter of the can. The height of the foam is two millimeters more than half the height of the can. Foam rubber plays the role of a displacer in the engine;
  • Take the lid of the jar, make a hole in the middle, two millimeters in diameter. Solder a hollow rod to the hole, which will act as a guide for the engine connecting rod;
  • Take a circle cut out of foam, insert a screw into the middle of the circle and lock it on both sides. Solder a pre-straightened paperclip to the washer;
  • Drill a hole two centimeters from the center, three millimeters in diameter, thread the displacer through the central hole of the lid, solder the lid to the jar;
  • Make a small cylinder out of tin, one and a half centimeters in diameter, solder it to the lid of the can in such a way that the side hole of the lid is clearly centered inside the engine cylinder;
  • Make an engine crankshaft out of a paper clip. The calculation is carried out in such a way that the spacing of the knees is 90 °;
  • Make a stand for the crankshaft of the engine. From a plastic film, make an elastic membrane, put the film on the cylinder, push it through, fix it;


  • Make an engine connecting rod yourself, bend one end of the straightened product in the shape of a circle, insert the other end into a piece of eraser. The length is adjusted in such a way that at the lowest point of the shaft the membrane is retracted, at the extreme upper point, the membrane is maximally extended. Adjust the other connecting rod in the same way;
  • Glue the engine connecting rod with a rubber tip to the membrane. Mount the connecting rod without a rubber tip on the displacer;
  • Put a flywheel from the disk on the crank mechanism of the engine. Attach legs to the jar so as not to hold the product in your hands. The height of the legs allows you to place a candle under the jar.

After we managed to make a Stirling engine at home, the engine is started. To do this, a lighted candle is placed under the jar, and after the jar has warmed up, they give impetus to the flywheel.


The considered installation option can be quickly assembled at home, as a visual aid. If you set a goal and desire to make the Stirling engine as close as possible to factory counterparts, in free access There are drawings of all the details. Stepping through each node will allow you to create a working layout that is no worse than commercial versions.

Advantages

The Stirling engine has the following advantages:

  • A temperature difference is necessary for the operation of the engine, which fuel causes heating is not important;
  • There is no need to use attachments and auxiliary equipment, the engine design is simple and reliable;
  • The resource of the engine, due to the design features, is 100,000 hours of operation;
  • The operation of the engine does not create extraneous noise, since there is no detonation;
  • The process of engine operation is not accompanied by the emission of waste substances;
  • Engine operation is accompanied by minimal vibration;
  • Processes in the plant cylinders are environmentally friendly. Using the right heat source keeps the engine clean.

disadvantages

The disadvantages of the Stirling engine include:

  • It is difficult to establish mass production, since the engine design requires the use of a large number materials;
  • High weight and large dimensions of the engine, since a large radiator must be used for efficient cooling;
  • To increase efficiency, the engine is boosted using complex substances (hydrogen, helium) as a working fluid, which makes the operation of the unit dangerous;
  • The high temperature resistance of steel alloys and their thermal conductivity complicate the engine manufacturing process. Significant heat losses in the heat exchanger reduce the efficiency of the unit, and the use of specific materials makes the manufacture of the engine expensive;
  • To adjust and switch the engine from mode to mode, special control devices must be used.

Usage

The Stirling engine has found its niche and is actively used where dimensions and omnivorousness are an important criterion:

  • Stirling engine-generator.

A mechanism for converting heat into electrical energy. Often there are products used as portable tourist generators, installations for the use of solar energy.

  • The engine is like a pump (electric).

The engine is used for installation in a circuit heating systems saving on electrical energy.

  • The engine is like a pump (heater).

In countries with a warm climate, the engine is used as a space heater.

Stirling engine on a submarine:


  • The engine is like a pump (cooler).

Almost all refrigerators in their design use heat pumps By installing a Stirling engine, resources are saved.

  • The engine is like a pump that creates ultra-low heat levels.

The device is used as a refrigerator. To do this, the process is started in the opposite direction. The units liquefy gas, cool measuring elements in precise mechanisms.

  • Underwater engine.

The submarines of Sweden and Japan work thanks to the engine.

Stirling engine as a solar installation:


  • The engine is like a battery of energy.

Fuel in such units, salt melts, the engine is used as an energy source. In terms of energy reserves, the motor is ahead of chemical elements.

  • solar engine.

Convert the sun's energy into electricity. The substance in this case is hydrogen or helium. The engine is placed in the focus of the maximum concentration of the energy of the sun, created using a parabolic antenna.

A Stirling engine is a kind of engine that starts to run on thermal energy. In this case, the source of energy is completely unimportant. The main thing is to make a difference temperature regime, in this case, such an engine will work. Now we will analyze how you can create a model of such a low-temperature engine from a can of Coca-Cola.

Materials and fixtures

Now we will analyze what we need to take to create an engine at home. What we need to take for stirling:

  • Balloon.
  • Three cans of cola.
  • Special terminals, five pieces (for 5A).
  • Nipples for fixing bicycle spokes (two things).
  • Cotton wool.
  • A piece of steel wire thirty cm long and 1 mm in cross section.
  • A piece of large steel or copper wire with a diameter of 1.6 to 2 mm.
  • Wooden pin with a diameter of twenty mm (length one cm).
  • Bottle cap (plastic).
  • Wiring (thirty cm).
  • Special glue.
  • Vulcanized rubber (about 2 centimeters).
  • Fishing line (length thirty cm).
  • Several weights for balancing (for example, nickel).
  • CDs (three pieces).
  • Special buttons.
  • A tin can for creating a firebox.
  • Heat resistant silicone and tin can for making water cooling.

Description of the creation process

Stage 1. Jars preparation.

First you should take 2 cans and cut them off upper part. If the tops are cut off with scissors, the resulting notches will have to be ground off with a file.

Stage 2. Making the diaphragm.

As a diaphragm, you can take balloon, which should be reinforced with vulcanized rubber. The ball must be cut and pulled onto a jar. Then glue a piece of special rubber on the central part of the diaphragm. After the glue has hardened, in the center of the diaphragm we will punch a hole for installing the wire. The easiest way to do this is with a special button that can be left in the hole until assembly.

Stage 3. Cutting and creating holes in the lid.

Two holes of two mm must be made in the walls of the cover, they are necessary to install the pivot axis of the levers. Another hole must be made in the bottom of the lid, a wire will go through it, which will be connected to the displacer.

On the last step cover must be cut off. This is done so that the displacer wire does not catch on the edges of the cover. For such work, you can take household scissors.

Stage 4. Drilling.

In the jar, you need to drill two holes for the bearings. In our case, this was done with a 3.5 mm drill.

Stage 5. Making a viewing window.

A special window must be cut out in the engine housing. Now it will be possible to observe how all the nodes of the device work.

Stage 6. Terminal modification.

It is necessary to take the terminals and remove the plastic insulation from them. Then we take a drill, and make through holes on the edges of the terminals. In total, three terminals need to be drilled. Leave two terminals undrilled.

Stage 7. Creating leverage.

As a material for the manufacture of levers, copper wire is taken, the diameter of which is only 1.88 mm. How exactly to bend the knitting needles, it is worth looking on the Internet. You can take steel wire, just with copper wire, it is more convenient to work.

Stage 8. Manufacturing of bearings.

To make the bearings, you will need two bicycle nipples. The hole diameter needs to be checked. The author drilled them through with a 2 mm drill.

Stage 9. Installation of levers and bearings.

Levers can be placed directly through the viewing window. One end of the wire should be long, the flywheel will lie on it. Bearings should sit firmly in the right places. If there is a backlash, they can be glued.

Stage 10. Making the displacer.

The displacer is made of steel wool for polishing. For the manufacture of the displacer, a steel wire is taken, a hook is created on it, and then a certain amount of cotton wool is wound around the wire. The displacer must be the same size so that it moves smoothly in the bank. The entire height of the displacer should not exceed five centimeters.

At the end on one side of the cotton it is necessary to make a spiral of wire so that it does not come out of the wool, and on the second side we make a loop from the wire. Then we will tie a fishing line to this loop, which will subsequently be attracted through the central part of the diaphragm. Vulcanized rubber should be in the middle of the container.

Step 11. Making the pressure tank

It is necessary to cut the bottom of the jar in a certain way so that about 2.5 cm remains from its base. The displacer together with the diaphragm must be moved to the tank. After that, this whole mechanism is transferred to the end of the can. The diaphragm needs to be tightened a little. so that it does not sag.

Then you need to take the terminal that was not drilled, and pass the fishing line through it. The knot must be glued so that it does not move. The wire must be lubricated with high quality oil and at the same time make sure that the displacer can easily stretch the line behind it.

Stage 12. Making push rods.

These special links connect the diaphragm and levers. This is made from a piece of copper wire fifteen cm long.

Stage 13. Creating and installing a flywheel

For the manufacture of the flywheel, we take three old CDs. Take a wooden rod as the center. After installing the flywheel, bend the crankshaft rod, so the flywheel will no longer subside.

At the last stage, the entire mechanism is assembled completely.

The last step, creating a firebox

So we have reached the last step in the creation of the engine.


A Stirling engine is an engine that can run on thermal energy. In this case, the source of heat is absolutely not important. The main thing is that there is a temperature difference, in which case this engine will work. The author figured out how to make a model of such an engine from a can of Coca-Cola.


Materials and tools
- one balloon;
- 3 cans of cola;
- electrical terminals, five pieces (for 5A);
- nipples for attaching bicycle spokes (2 pieces);
- metal wool;
- a piece of steel wire 30 cm long and 1 mm in cross section;
- a piece of thick wire made of steel or copper with a diameter of 1.6 to 2 mm;
- a pin made of wood with a diameter of 20 mm (length 1 cm);
- bottle cap (plastic);
- electrical wiring (30 cm);
- Super glue;
- vulcanized rubber (about 2 square centimeters);
- fishing line (length about 30 cm);
- a pair of weights for balancing (for example, nickel);
- CDs (3 pieces);
- pushpins;
- another tin can for making a firebox;
- heat-resistant silicone and a tin can to create water cooling.


Step one. Jars preparation
First of all, you need to take two jars and cut off their tops. If the tops are cut with scissors, the resulting notches will need to be ground off with a file.
Next, you need to cut the bottom of the jar. This can be done with a knife.







Step two. Creating an Aperture
As a diaphragm, the author used a balloon, which was reinforced with vulcanized rubber. The ball must be cut and pulled over the jar, as indicated in the picture. Then a piece of vulcanized rubber is glued to the center of the diaphragm. After the glue hardens, a hole is punched in the center of the diaphragm for installing the wire. The easiest way to do this is with a pushpin, which can be left in the hole until assembly.






Step three. Cutting and creating holes in the lid
In the walls of the cover, you need to drill two holes of 2 mm each, they are needed to install the pivot axis of the levers. Another hole must be drilled in the bottom of the lid, a wire will pass through it, which will be connected to the displacer.

At the final stage, the cover must be cut as shown in the picture. This is done so that the displacer wire does not cling to the edges of the cover. For such work, utility scissors are suitable.




Step four. Drilling
In the jar, you need to drill two holes for the bearings. In this case, this was done with a 3.5 mm drill.


Step five. Creating a viewing window
A viewing window must be cut into the engine housing. Now it will be possible to observe how all the nodes of the device function.


Step six. Terminal modification
You need to take the terminals and remove the plastic insulation from them. Then a drill is taken, and through holes are made at the edges of the terminals. In total, you need to drill 3 terminals, while two should remain undrilled.


Step seven. Creating leverage
As a material for creating levers, copper wire is used, the diameter of which is 1.88 mm. How exactly to bend the knitting needles is shown in the pictures. You can also use steel wire, it's just more pleasant to work with copper wire.





Step eight. Creation of bearings
To make bearings, you will need two bicycle nipples. The hole diameter needs to be checked. The author drilled them through with a 2 mm drill.


Step nine. Installation of levers and bearings
The levers can be installed directly through the viewing window. One end of the wire should be long, it will have a flywheel. The bearings must be firmly in place. If there is a backlash, they can be glued.


Step ten. Creating a Displacer
The displacer is made of steel wool for polishing. To create a displacer, a steel wire is taken, a hook is made on it, and then the required amount of cotton wool is wound around the wire. The displacer must be large enough to move freely in the can. The total height of the displacer should not exceed 5 cm.

As a result, on one side of the cotton wool, it is necessary to form a spiral of wire so that it does not come out of the cotton wool, and on the other side a loop is made of the wire. Next, a fishing line is tied to this loop, which is subsequently pulled through the center of the diaphragm. The vulcanized rubber should be in the middle of the container.








Step 11 Create a Pressure Tank
It is necessary to cut the bottom of the jar so that about 2.5 cm remains from its base. The displacer together with the diaphragm must be placed in the tank. After that, this whole mechanism is installed at the end of the can. The diaphragm needs to be tightened a little so that it does not sag.




Then you need to take the terminal that was not drilled and stretch the fishing line through it. The knot must be glued so that it does not move. The wire must be well lubricated with oil and at the same time make sure that the displacer easily pulls the line along.
Step 12 Create Push Rods
Push rods connect the diaphragm and levers. This is done with a piece of copper wire 15 cm long.

In which the working fluid (gaseous or liquid) moves in a closed volume, in fact it is a kind of external combustion engine. This mechanism is based on the principle of periodic heating and cooling of the working fluid. Extraction of energy occurs from the emerging volume of the working fluid. The Stirling engine works not only from the energy of burning fuel, but also from almost any source. This mechanism was patented by the Scot Robert Stirling in 1816.

The described mechanism, despite the low efficiency, has a number of advantages, first of all, it is simplicity and unpretentiousness. Thanks to this, many amateur designers are trying to assemble a Stirling engine with their own hands. Some succeed, and some don't.

In this article we will consider Stirling with our own hands from improvised materials. We will need the following blanks and tools: a tin can (you can use it from under sprats), sheet metal, paper clips, foam rubber, elastic, a bag, wire cutters, pliers, scissors, a soldering iron,

Now let's start assembling. Here detailed instructions to how to make a Stirling engine with your own hands. First you need to wash the jar, clean the edges with sandpaper. We cut out a circle from sheet metal so that it lies on the inner edges of the can. We determine the center (for this we use a caliper or ruler), make a hole with scissors. Next, we take a copper wire and a paper clip, straighten the paper clip, make a ring at the end. We wind a wire on a paper clip - four tight turns. Next, soldering the resulting spiral a small amount solder. Then it is necessary to carefully solder the spiral to the hole in the cover so that the stem is perpendicular to the cover. The paperclip should move freely.

After that, it is necessary to make a communicating hole in the lid. We make a displacer from foam rubber. Its diameter should be slightly smaller than the diameter of the can, but there should not be a large gap. The height of the displacer is a little more than half of the can. We cut a hole in the center of the foam rubber for the sleeve, the latter can be made of rubber or cork. We insert the rod into the resulting sleeve and glue everything. The displacer must be placed parallel to the cover, this is an important condition. Next, it remains to close the jar and solder the edges. The seam must be sealed. Now we proceed to the manufacture of the working cylinder. To do this, cut out a strip 60 mm long and 25 mm wide from tin, bend the edge by 2 mm with pliers. We form a sleeve, after that we solder the edge, then it is necessary to solder the sleeve to the cover (above the hole).

Now you can start making the membrane. To do this, cut off a piece of film from the package, push it a little with your finger inside, press the edges with an elastic band. Next, you need to check the correctness of the assembly. We heat the bottom of the can on fire, pull the stem. As a result, the membrane should bend outward, and if the rod is released, the displacer should lower under its own weight, respectively, the membrane returns to its place. In the event that the displacer is made incorrectly or the soldering of the can is not tight, the rod will not return to its place. After that, we make the crankshaft and racks (the spacing of the cranks should be 90 degrees). The height of the cranks should be 7 mm and the displacers 5 mm. The length of the connecting rods is determined by the position of the crankshaft. The end of the crank is inserted into the cork. So we looked at how to assemble a Stirling engine with our own hands.

Such a mechanism will work from an ordinary candle. If you attach magnets to the flywheel and take the coil of an aquarium compressor, then such a device can replace a simple electric motor. With your own hands, as you can see, making such a device is not at all difficult. There would be a desire.

Modern automotive industry has reached a level of development in which, without fundamental scientific research it is almost impossible to achieve dramatic improvements in the design of traditional internal combustion engines. This situation forces designers to pay attention to alternative power plant designs. Some engineering centers have focused on creating and adapting hybrid and electric models for serial production, while other automakers are investing in the development of engines powered by renewable sources (for example, biodiesel with rapeseed oil). There are other projects of power units, which in the future may become the new standard propulsion for Vehicle.

Among the possible sources of mechanical energy for cars of the future is the external combustion engine, which was invented in the middle of the 19th century by the Scot Robert Stirling as a thermal expansion machine.

Scheme of work

Stirling engine converts thermal energy, supplied from the outside, into useful mechanical work at the expense changes in the temperature of the working fluid(gas or liquid) circulating in a closed volume.

In general, the scheme of operation of the device is as follows: in the lower part of the engine, the working substance (for example, air) heats up and, increasing in volume, pushes the piston up. Hot air penetrates to the top of the motor, where it is cooled by a radiator. The pressure of the working fluid is reduced, the piston is lowered for the next cycle. In this case, the system is sealed and the working substance is not consumed, but only moves inside the cylinder.

There are several design options for power units using the Stirling principle.

Stirling modification "Alpha"

The engine consists of two separate power pistons (hot and cold), each of which is located in its own cylinder. Heat is supplied to the cylinder with the hot piston, and the cold cylinder is located in the cooling heat exchanger.

Stirling modification "Beta"

The cylinder containing the piston is heated on one side and cooled on the opposite end. A power piston and a displacer move in the cylinder, designed to change the volume of the working gas. The return movement of the cooled working substance into the hot cavity of the engine is performed by the regenerator.

Stirling modification "Gamma"

The design consists of two cylinders. The first is completely cold, in which the power piston moves, and the second, hot on one side and cold on the other, serves to move the displacer. The regenerator for circulating cold gas can be common to both cylinders or be included in the design of the displacer.

Advantages of the Stirling engine

Like most external combustion engines, Stirling is inherent multi-fuel: the engine runs on a temperature difference, regardless of the reasons that caused it.

Interesting fact! Once, an installation was demonstrated that operated on twenty fuel options. Without stopping the engine, gasoline, diesel fuel, methane, crude oil and vegetable oil- the power unit continued to work steadily.

The engine has simplicity of design and does not require additional systems and attachments(timing, starter, gearbox).

Features of the device guarantee a long service life: more than one hundred thousand hours of continuous operation.

The Stirling engine is silent, since detonation does not occur in the cylinders and there is no need to remove exhaust gases. Modification "Beta", equipped with a rhombic crank mechanism, is a perfectly balanced system that does not have vibrations during operation.

There are no processes in the engine cylinders that can have negative impact on the environment. By choosing a suitable heat source (e.g. solar power), Stirling can be absolutely environmentally friendly power unit.

Disadvantages of the Stirling design

With all set positive properties immediate mass use of Stirling engines is impossible for the following reasons:

The main problem lies in the material consumption of the structure. Cooling of the working fluid requires the presence of large volume radiators, which significantly increases the size and metal consumption of the installation.

The current technological level will allow the Stirling engine to compare in performance with modern gasoline engines only through the use of complex types of working fluid (helium or hydrogen) under pressure of more than one hundred atmospheres. This fact raises serious questions both in the field of materials science and user safety.

An important operational problem is related to the issues of thermal conductivity and temperature resistance of metals. Heat is supplied to the working volume through heat exchangers, which leads to inevitable losses. In addition, the heat exchanger must be made of heat-resistant metals resistant to high pressure. Suitable materials very expensive and difficult to process.

The principles of changing the Stirling engine modes are also fundamentally different from traditional ones, which requires the development of special control devices. So, to change the power, it is necessary to change the pressure in the cylinders, the phase angle between the displacer and the power piston, or to affect the capacity of the cavity with the working fluid.

One way to control the shaft speed on a Stirling engine model can be seen in the following video:

Efficiency

In theoretical calculations, the efficiency of the Stirling engine depends on the temperature difference of the working fluid and can reach 70% or more in accordance with the Carnot cycle.

However, the first samples realized in metal had an extremely low efficiency for the following reasons:

  • inefficient coolant (working fluid) options, limiting maximum temperature heating;
  • energy losses due to friction of parts and thermal conductivity of the engine housing;
  • lack of structural materials resistant to high pressure.

Engineering solutions have constantly improved the design of the power unit. So, in the second half of the 20th century, a four-cylinder automobile Stirling engine with a rhombic drive showed an efficiency equal to 35% in tests on a water coolant with a temperature of 55 ° C. Careful study of the design, the use of new materials and fine-tuning of the working units ensured the efficiency of the experimental samples at 39%.

Note! Modern gasoline engines of similar power have an efficiency of 28-30%, and turbocharged diesel engines in the range of 32-35%.

Modern examples of the Stirling engine, such as the one built by the American company Mechanical Technology Inc, show efficiency up to 43.5%. And with the development of the production of heat-resistant ceramics and similar innovative materials, it will be possible to significantly increase the temperature of the working environment and achieve an efficiency of 60%.

Examples of successful implementation of automotive Stirlings

Despite all the difficulties, there are many workable models of the Stirling engine applicable to the automotive industry.

Interest in Stirling, suitable for installation in a car, appeared in the 50s of the XX century. Work in this direction was carried out by such concerns as Ford Motor Company, Volkswagen Group and others.

UNITED STIRLING (Sweden) developed Stirling, which made maximum use of serial components and assemblies produced by automakers (crankshaft, connecting rods). The resulting four-cylinder V-engine had a specific gravity of 2.4 kg / kW, which is comparable to the characteristics of a compact diesel engine. This unit was successfully tested as a power plant for a seven-ton cargo van.

One of the successful examples is the four-cylinder Stirling engine of the Dutch production model "Philips 4-125DA", intended for installation on a car. The motor had a working power of 173 liters. with. in dimensions similar to the classic gasoline unit.

General Motors engineers achieved significant results by building an eight-cylinder (4 working and 4 compression cylinders) V-shaped Stirling engine with a standard crank mechanism in the 70s.

Similar power plant in 1972 equipped with a limited series of Ford Torino cars, whose fuel consumption has decreased by 25% compared to the classic gasoline V-shaped eight.

Currently, more than fifty foreign companies are working to improve the design of the Stirling engine in order to adapt it to mass production for the needs of the automotive industry. And if it is possible to eliminate the shortcomings of this type of engine, while maintaining its advantages, then it is Stirling, and not turbines and electric motors, that will replace gasoline internal combustion engines.