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ENGINE WITH EXTERNAL HEAT SUPPLY

Dmitry Konyukhov

(EN) The invention relates to machine building, in particular to engine building, in particular to engines with external supply of heat. And it is intended for use as a power plant.

The invention can be used in the automotive industry, but also as propulsion devices for sea and river transport. In addition, the motor can be used as a drive for electric generators.

With the modern development of technology, the issue of the need to create power plants in which various sources of thermal energy that do not pollute the environment and have a low level of noise and vibration can be used. Such prospective power plants can include the proposed engine.

A simplified diagram of the engine is shown in Fig. 1. In the engine compression and expansion cycles are carried out in different cylinders, respectively compression 1 and expansion 2. Cylinders 1 and 2 are connected through a compression 3 and an extension 4 of the highway. In the compression line 3 there is a cooler 5 and in the expansion line 4 there is a heater 6. The compression line 3 is connected to the compression cylinder 1 through the exhaust valve 7 and to the expansion cylinder 2 through the inlet valve 8. The expansion line 4 is connected to the expansion cylinder 2 through the outlet Valve 9, and to the compression cylinder 1 through the intake valve 10. The pistons 11 and 12 of the cylinders 1 and 2 are connected to the motor shaft 13 via the motion conversion mechanism 14.

Fig. 1. Diagram of DVPT operation

Structurally, the engine contains four expansion and four compression cylinders. Cylinders are arranged alternately and in parallel, around the axis of the working shaft of the engine. The mechanism for converting the reciprocating motion is made in the form of an oblique washer, as the drive of an axial-piston pump. Fuel combustion occurs in the heat exchange chamber. The supply of heat to the working fluid is carried out through the heat exchange tubes. When the working medium is compressed, heat is removed through the heat exchange tubes and the working medium is cooled in the cooler (radiator). The amount of working fluid (it can be air), enclosed in the working volume of the engine, is constant and unchangeable. The working body is under great pressure, of the order of 40-200 atm.

Appearance of the engine

The engine has approximately the same dimensions and mass as a conventional gasoline engine.

The features of the proposed engine include:

High efficiency. The possibility of obtaining a high efficiency, and therefore of great economic efficiency, is an important feature of the engine. This is due to the full use of the temperature drop and the pressure in the cycle. However, in order to realize these opportunities, it is necessary to overcome significant design and technological difficulties, and difficulties associated with the selection of materials for the manufacture of engine parts.

Different heat sources. External heat input, used in the engine, allows the use of various thermal sources without any significant changes in the engine design. Virtually all fossil fuels from solid to gaseous can be directly used in the engine. For this purpose, the engine is equipped with a combustion chamber with a recuperative heat exchanger to heat the air charge with the heat of the exhaust gases.

In cities with high traffic for use on vehicles, the engine with a thermal battery has great prospects.

The advantage of the engine lies in the fact that it can work not only on a variety of fuels, but it makes it possible to use different types of heat sources. This means that the operation of the engine does not depend on the presence of the atmosphere. It can work equally well in confined space, both on submarines and on satellites.

Impact on the environment (toxicity, noise, vibration). It is obvious that the toxicity of the engine (in the usual sense of this concept) can only be said when using the heat of combustion of the fuel.

Sources for the release of toxic substances are the products of combustion of fuel and its evaporation from the food system. The engine operates in a closed cycle, so its crankcase does not have combustion products, and as a consequence, no toxic substances are released from the crankcase.

Evaporation of fuel into the atmosphere in the engine is much less than that of carburetor internal combustion engines, since the fuel system is closed. Virtually the only source of toxic substances are combustion products that escape into the atmosphere from the combustion chamber.

The main toxic substances contained in the combustion products of this fuel are carbon monoxide CO, unburned hydrocarbons C _x H _y , nitrogen oxides NO _x , aldehydes, soot, sulfur oxides (using sulfur fuels), lead compounds (for leaded gasolines).

We estimate the toxicity of the engine for the release of carbon monoxide, hydrocarbons, nitrogen oxides, and smoke. These allocations are or are subject to legislative restrictions. Toxic products of incomplete combustion (CO and C _x H _y ) are the consequence of a lack of oxygen during combustion (at low total or local air-excess coefficients).

The soot in the exhaust gases appears in those cases when there is a thermal decomposition of hydrocarbon fuel (cracking) at high temperatures and a lack of oxygen. The combustion chambers of the engine are similar to the combustion chambers of gas turbine and steam engines. The combustion process in them is stationary. Under these conditions, it is possible to ensure a sufficiently good quality of the mixture formation. The air entering the combustion chamber is heated in a special heater by the exhaust gases. Obviously, the release of toxic substances with exhaust gases in the engine depends on the air excess ratio during combustion and the air temperature at the inlet to the combustion chamber.

With an increase in the excess air factor, the concentration of CO, C _x H _y and NO _x decreases during combustion. Consideration of the mass of toxic components released when a unit of fuel is burned leads to the same conclusion. It should be noted very low concentrations of CO, C _x H _y . The NO _x concentration decreases with an increase in the air excess ratio due to a more significant effect of temperature decrease compared to the effect of an increase in the amount of free oxygen in the combustion products. Since the efficiency of the engine drops somewhat when the excess air factor is increased, the rational value of the air excess ratio during combustion is approximately 1.5-1.8.

With an increase in the temperature of the air entering the combustion chamber, with a constant excess air coefficient, the content of the products of incomplete combustion (CO and C _x H _y ) decreases, and the NO _x concentration increases. The efficiency of the engine increases with increasing air temperature at the inlet to the combustion chamber. Reducing the concentration of CO and C _x H _{y is} due to improved combustion conditions in hotter air. The increase in the NOx concentration is due to the increase in the maximum combustion temperature with a constant excess air ratio. The air temperature at the entrance to the combustion chamber in the engine reaches 600-800 ° C.

It should be noted that the exhaust gases of the engine are odorless and practically free of soot.

The above materials show that nitrogen oxides exert the greatest influence on the toxicity of engine exhaust gases. Isolation of these can be reduced by exposure to the conditions of combustion of fuel in the chamber (reduction of the maximum temperature and oxygen concentration). To reduce the temperature in the combustion zone, the appropriate combustion chamber parameters are selected or exhaust gas recirculation is used (as in internal combustion engines).

An increase in the number of by-passes of exhaust gases of more than 33% of the amount of incoming fresh air is impractical, since the concentration of CO significantly increases, and the NOx concentration decreases less significantly.

To assess the level of engine toxicity, the table gives specific emissions of toxic substances in this engine, in a diesel engine, a gas turbine and a carburetor engine.

It follows from the table that even without taking special measures, the toxicity of the engine's exhaust gases is much lower than the toxicity of other types of thermal engines.

Low noise and vibration. The main sources of noise in internal combustion engines are the turbocharger, the combustion process, the intake and exhaust processes, the gas distribution mechanism, the crank and connecting mechanisms and auxiliary mechanisms (due to the presence of gaps in the gearing, periodically overlapping gaps in the movable joints, etc.). Generation of noise by auxiliary mechanisms in internal combustion engines and external combustion can be adopted the same, there are no other sources of noise in the engine, therefore the noise level produced by the running engine is much less than that of the internal combustion engine. External combustion in the engine is continuous and does not have an explosive nature, so that during combustion and release, noise is almost not generated.

In addition, the pressure in the cylinders of the engine changes smoothly, almost in a sinusoidal fashion. The noise level of this engine is on average 20-30 dB lower than a diesel of the same power.

Lube oil consumption. In internal combustion engines, the ingress of oil into the cylinder, on the one hand, leads to the burning out of oil, and on the other, to its aging due to contact with hot gases and engine parts.

In the proposed engine, oil can not practically get into the working cavities, and besides, it does not come into contact with either hot gases or heated parts, so there is neither burning nor oiling. As a consequence, the engine does not need to periodically add oil. In principle, the engine can run throughout the entire service life with the oil originally refueled (if it does not change its qualities with the passage of time under the influence of the environment), which is cleared only of abrasive particles. For large and medium-sized engines this is an important economic advantage (the cost of lubricating oil is 10 times higher than the cost of fuel). For low-power engines, this significantly reduces the laboriousness of maintenance.

Oil entering the working cavities of the engine is extremely undesirable and extremely harmful phenomenon, as the properties of the working fluid and, as a consequence, the effective efficiency of the engine change. Therefore, the engine uses non-lubricated piston rings, and the lubricant is required only for lubrication of the drive mechanism and auxiliary units. As piston seals in the engine, continuous rings of fluoroplastic or composite materials based on the latter are used.

Reliable and quick start of the engine at low temperature. The proposed engine, which has a high pressure of the working fluid in the internal cavities and a sufficiently high temperature of the heater tubes, is easily started at any ambient temperature. Its start depends solely on the reliability with which fuel in the combustion chamber can be ignited. The spark plug, which is integrated with the injector into one unit, virtually guarantees engine start-up at any environmental parameters.

Insensitivity to dust in the surrounding area. Since the proposed engine is an external combustion engine, the dust entering the air charge of the combustion chamber from the surrounding space does not enter the cylinders and the crankcase (in the engine, crankcase ventilation is not required). As a result, there is no additional abrasive wear on the moving parts of the drive mechanism in the engine. In addition, because of the low speed of air charge and exhaust gases in the recuperative combustion chamber heat exchanger (air-charge heater) and in its spraying device, the corrosion of these parts is negligible.

Work with short-term overloads. The motor resource of the engines is determined by the rate at which the creep rate reaches the material of the heater parts operating at high temperature. With increasing pressure of the working fluid in the internal cavities of the engine, the creep rate becomes more rapid. Nevertheless, the short-term overloads associated with increasing the pressure of the working fluid in the internal cavities, slightly reduce the longevity of the engine, since the temperature of the heater parts remains unchanged.

In general, any engine can be guaranteed to withstand a short-term 50-80% overload without a noticeable decrease in longevity.

Heat transfer to the cooling medium. Due to the presence in the motor of a closed circulating system of the working fluid, the heat sink is almost completely carried out through the cooler, and the heat sink must occur at the lowest possible temperatures. Therefore, the amount of heat that is diverted to the cooling water in the engine is approximately 2 times greater than in internal combustion engines, with their equal effective efficiency. Consequently, the dimensions of the radiator of the engine cooling system on vehicles are greater than those of internal combustion engines of the same purpose.

In marine engines this feature is not a serious drawback.

MAIN PARAMETERS OF THE ENGINE VOLUME 1500 cm ³

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Author: Dmitry Konyukhov
PS Material is protected

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