Liquid nitrogen engine and liquid nitrogen injection cycle in a two-stroke engine.

Abstract

Liquid nitrogen engine, part of whose operating energy results from the compression of air drawn from outside the engine. "Figure to be published for the abstract: [Fig. 7]"

Description

Title of the invention: Liquid nitrogen engine and liquid nitrogen injection cycle in a two-stroke engine.

[0001] There are many types of compressed air motors used in industry, or for craft activities. These motors are most often used for mechanical purposes or for the motorization of vehicles. Compressed air motors can also be used for the design of electrical energy storage and restitution systems by proceeding as follows: -The air is compressed to high pressure, typically pressures above 300 bars, using commercially available compressors. -This compressed air is stored in cylinders designed to withstand these high pressures and then, as needed, is injected into the piston chambers of an engine. -The compressed air motor is coupled either to the mechanical transmission components of a vehicle to ensure its mobility, or to an electricity generator, preferably a permanent magnet generator. In the case of coupling to a generator, we thus have a source of current and voltage which can replace battery systems or other means of energy storage such as super-capacitors. The current from this generator can be transformed and then coupled to an electric motor, which will enable an electric vehicle to operate. The operating time of the system depends on the amount of stored compressed air, the air consumption by the engine and, therefore, the type of compressed air engine and the injection cycle of the compressed air into this engine.

[0002] The invention, the subject of this patent, describes an engine operating on liquid nitrogen, and a cycle for injecting liquid nitrogen into an engine, designed according to the known principle of so-called "two-stroke" internal combustion engines or so-called "diesel" engines.

[0003] A "two-stroke" combustion engine [Fig.l] operates according to the stages of the cycles shown in [Fig.2]. • Outside air, which is at atmospheric pressure, is drawn in by the air intake (1.2) • When the piston (3-1) moves upwards in the piston chamber (1-3). Outside air mixed with gasoline is drawn into the crankshaft chamber (3-3) located below the piston. [Fig.2] (b). • A valve (1-2-1) opens and closes in phase with the movement of the engine piston in its chamber. As the piston rises, outside air is sucked in in the lower engine and the valve (1-2-1) is open. • As it descends, the piston compresses the air in the crankshaft chamber. The valve (1-2-1) is closed. • When the air injection window (1-1) is clear, when the piston descends, the air / fuel mixture from the crankshaft chamber is injected into the piston chamber (1-3). A deflector (3-1-1) directs the mixture towards the top of the piston chamber. This mixture expels, via the outlet orifice (1-4), the combustion residues resulting from the explosion of the previous cycle, present in the piston chamber [Fig.2] (a). • When rising, the piston covers the outlet orifice (1-4) and compresses the air / fuel mixture which reaches a high temperature, [Fig.2] (c). • A spark provided by the spark plug (4) causes the mixture to explode, which violently pushes the piston downwards, [Fig.2] (d), and the cycle resumes. Under the effect of compression, if the compression ratio of the mixture in the piston chamber is sufficient, the mixture can be brought to a high temperature, above 600 K, which means that, in diesel engines, the mixture explodes spontaneously. • Compression ratio means the maximum volume of air drawn into the piston chamber divided by the volume of this air compressed by the piston in the high position. • The piston chamber (1-3), and the engine, are made of an alloy, preferably with high heat capacity, high thermal conductivity, such as an aluminum alloy, to cool the piston chamber of the heat engine.

[0004] Our invention will be described more precisely in the remainder of this text using the engine diagram of [Fig.3] and [Fig.4] where two sections of the engine are shown schematically. [Table 1] describes the list of components found in [Fig.1] or [Fig.3] or [Fig.4]. [Tables 1] Engine block (1) Moving parts (3) Crankshaft chamber (3-3) Air injection window in the piston chamber (1-1) Air circulation channel in the lower engine (1-1-D) Outside air intake in the lower engine (1-2) Outside air inlet valve (1-2-1) Piston chamber (1-3) Expansion air outlet (1-4) Spark plug (4) Piston (3-1) Air deflector entering the piston chamber (3-1-1) See [Fig.l] Connecting rod (3-2) Engine shaft (3-4) Balance weight / flywheel (3-5) Seal groove (3-6) which is not shown in the diagrams. Liquid nitrogen injection Liquid nitrogen engine [Fig. 4] Liquid nitrogen injection system (4-1) Electronic control of liquid nitrogen injection (4-1-1) Liquid nitrogen tube (4-1-2) connected to a liquid nitrogen cylinder not shown in the figure.Liquid nitrogen injection nozzle in the piston chamber (4-1-3) Compressed air circulation cavity (5) Compressed air outlet valve and Air outlet valve (5-1) Camshaft and valve activation system (5-2) (valve, rod, spring, cam). Compressed air outlet to the outside (5-3) Piston cavity heating plug. (7) Thermal insulation of the air circulation cavity (6) Liquid nitrogen drop (8) [Fig. 5] and [Fig. 6] Liquid nitrogen vapor (9) [Fig. 5] and [Fig. 6].

[0005] When injecting outside air via channel (1-1-1) into the piston chamber (1-3), the compression of the air by the piston will bring this air to a high pressure and a high temperature. Depending on the air compression ratio, the temperature of the piston chamber, when the piston is in the high position, can exceed 600 degrees Kelvin, and the pressure in the chamber several tens of bars.

[0006] To maintain the piston chamber at a high temperature, and in all cases higher than the freezing temperature of water (273 K / 0°C) which is always contained in traces in liquid nitrogen, and to avoid the piston being blocked by ice: -A coil containing a heat transfer fluid containing a heated liquid can be placed around the piston chamber. -A heating plug (7) can be used, which in any case is necessary to start the liquid nitrogen engine, the cavity of which must be heated to prevent the piston from jamming when starting the engine due to freezing of the air moisture. This plug is powered by a battery, or a generator, not shown in the drawings.

[0007] A high temperature can also be maintained in the piston chamber by circulating high-temperature compressed air in a cavity (5) [Fig.4], surrounding the piston chamber. Which air circulation chamber is thermally insulated (6), to minimize temperature exchanges with the outside of the engine. The principle of such heating is described in patent FR 3115313. The arrows [Fig.4] indicate the direction of circulation of the hot air in the cavity. This air exits through the air outlet (5-3).

[0008] In our invention, [Fig.3], the liquid nitrogen engine comprises at least one liquid nitrogen injection system (4-1), the liquid nitrogen is stored in a liquid nitrogen cylinder, not shown in the figure, which enters through the tube (4-1-2) and is then injected into the piston chamber (1-3) through the injection nozzle (4-1-3). The system is electronically controlled via the component (4-1-1)

[0009] [Fig.5] describes the main stages of operation of the liquid nitrogen engine: a. [Fig.5] (b) When the piston (3-1) rises, there is suction of outside air, which is at atmospheric pressure of 1 bar, via air suction (1-2) and injection into the crankshaft chamber (3-3). b. [Fig.5] (a) When descending, the piston (3-1) compresses the air coming from the outside, and when the air injection window (1-1) is uncovered, the air coming from the outside is injected into the piston chamber (1-3) via the channel (1-1-1) while the vaporized nitrogen from the previous cycle is evacuated via the orifice (1-4). c. [Fig.5] (b) When moving up, the piston (3-1) compresses the air injected into the piston chamber (1-3), at a pressure which can reach several tens of bars depending on the compression ratio, typically greater than 30 bars, and this causes the air in the piston to heat up to a high temperature, typically greater than 600K. d. [Fig.5] (c) When the piston (3-1) reaches its upper position, the dead center At the top, we open the liquid nitrogen injection system which sends one or several drops of liquid nitrogen (8) into the volume heated to high temperature. e. [Fig.5] (d) The nitrogen suddenly vaporizes (9) and exerts a significant pressure P on the piston (3-1). This pressure depends on the quantity of liquid nitrogen injected, and on the temperature of the compressed air. This pressure P is added to the pressure of the air taken from outside and compressed by the piston. f. The cycle then resumes [Fig.5] (a)

[0010] To accelerate the evaporation of the liquid nitrogen drop, the surface of the piston must be rough. A roughness Ra> 1.6 pm is preferred.

[0011] Using the theory of ideal gases, it can be calculated that, when a drop of liquid nitrogen vaporizes at room temperature, T=20°C, and at atmospheric pressure (P=101325Pa or Ibar approximately), the volume V of the gaseous nitrogen obtained is approximately 683 times the volume Vg of the drop of liquid nitrogen. For example, a drop of liquid nitrogen of 1 ml volume will give 683 ml of nitrogen gas at approximately 1 bar pressure. So, considering that nitrogen gas would be an ideal gas, if we inject a 1ml drop into a volume equal to (683ml / 2) = 341.5ml, the pressure of the nitrogen gas will be 2 bars. And therefore, if the volume where the drop of liquid nitrogen is injected is divided by 10, or 6.8 ml, the pressure will be 10 bars. If we apply the ideal gas formula, PV=nRT, and let P be the pressure of the gas, V the volume of the enclosure, n the number of moles of gas, R the ideal gas constant, T the temperature of the compressed air expressed in degrees Kelvin. The pressure of the gaseous nitrogen resulting from the evaporation of the liquid nitrogen in the piston chamber can be considered to be proportional to the temperature T of the compressed air in the piston chamber, when the piston is at top dead center.

[0012] This temperature T in the enclosure depends on the following parameters: The (low) mass of liquid nitrogen injected into the piston chamber, the heat capacity of the liquid nitrogen, The mass of compressed air in the piston chamber, the heat capacity of the compressed air, The latent heat of evaporation of liquid nitrogen. Liquid nitrogen cools the volume as it evaporates. On the nature of the alloys of the piston displacement chamber. The boiling point of nitrogen is approximately 77.4 K / -196°C at atmospheric pressure.

[0013] A calibrated drop of liquid nitrogen can be injected, which will vaporize in the area compressed by the piston, or a nebulization of drops of liquid nitrogen can be injected. The pressure in the piston chamber will be approximately the sum of the pressures partial pressures of the nitrogen that has become gaseous and the partial pressure of the high-temperature compressed air present in the piston chamber. Since high-temperature compressed air is composed of 78% nitrogen, the whole behaves approximately like a single volume of nitrogen.

[0014] The injection of drops of liquid nitrogen can be done at high frequencies, for example equal to 500 Hz. The torque of the engine, the rotation frequency of the engine, will depend mainly on the compression ratio of the engine, the mass of liquid nitrogen injected into the piston chamber and the frequency of injection of the drops of liquid nitrogen.

[0015] The engine speed evolves towards a stationary speed where the temperature of the piston chamber (1-3), resulting from the compression of the outside air, will reach a value which depends on numerous parameters which must be adapted according to the expected performance of the engine: a. The compression ratio in the piston chamber. b. The type of alloy of the piston chamber and cylinder head, the ca lorific and thermal conductivity of these alloys. c. Insulation of the piston chamber.

[0016] However, injecting liquid nitrogen into a volume containing compressed air presents a constraint: we then find ourselves in a situation where it is the compression rate of the air coming from the outside, and compressed by the piston, which defines the minimum pressure which will be exerted on the piston after injection of the liquid nitrogen. Because the pressure of the vaporized nitrogen will be added to the pressure of the compressed air coming from the outside. This therefore does not allow for fine control of the consumption of liquid nitrogen, and for fine modulation of the engine rotation speed by controlling, for example, the frequency of injection of the volume of liquid nitrogen into the piston chamber (1-3). To be able to finely modulate the torque exerted on the piston, it is therefore necessary on the one hand to reduce the pressure in the piston after compression of the air coming from outside and on the other hand to keep the temperature of the piston well above 300K.

[0017] To improve the thermal behavior of the system, and finely control the quantity of liquid nitrogen injected, the engine [Fig.3] can be modified by adding [Fig.4] a. A valve for extracting compressed air (5-1), which had been taken at 1 bar from outside the engine, then compressed by the piston. This valve is controlled by a camshaft system (5-2) which can be usefully replaced by an electromagnetic control system for said valve. b. A piston chamber heating plug (7) connected to a battery.

[0018] A second operating principle of the liquid nitrogen engine is described [Fig.6]. A more detailed section is shown [Fig.7], showing a drop of liquid nitrogen injected into the engine (8) and the nitrogen vapor (9). - [Fig.6] (b) Just before the injection of liquid nitrogen, a valve (5-1), mechanically or electronically controlled, opens and lets out the high-temperature compressed air, then this valve is closed. Compressed, very hot air is injected into the volume (5) surrounding the piston chamber (1-3). The whole is wrapped in a thermal insulator (6), which keeps the piston chamber at a high temperature. - [Fig.6] (c) A drop of liquid nitrogen (8) is then injected into the piston chamber (1-3) which is approximately at atmospheric pressure, while maintaining a high volume temperature. - [Fig.6] (d) The nitrogen vaporizes (9) on contact with the walls of the piston and the piston chamber and suddenly pushes the piston back. - [([Fig.6]] (a) The vaporized and expanded nitrogen is evacuated, and air from outside enters the piston. The cycle begins again. This piston chamber temperature also depends on the compression ratio of the air taken from outside, the amount of liquid nitrogen injected into the piston chamber, as well as the materials used to manufacture the engine.

[0019] However, during engine operation, the temperature surrounding the engine may be particularly low, for example in polar regions. Therefore, to start the engine, or during operation, a temperature above 400K will be maintained using a heating plug (7) commonly used for diesel engines. This plug can be powered using a small part of the electrical energy supplied by the battery or by an alternator coupled to the engine.

Claims

Claims

1. Liquid nitrogen engine, designed according to the operating principle of a two-stroke engine, comprising: an air intake (1.2) through which air enters from the outside which is at atmospheric pressure; a valve (1-2-1) which opens and closes in phase with the movement of the piston of the engine; a channel (1-1-1) and an injection window (1-1) through which the outside air enters the piston movement chamber (1-3); a piston (3-1) which moves in the chamber (1-3); a liquid nitrogen injection system (4-1) which is stored in a liquid nitrogen cylinder, comprising an electronic injection control (4-1-1), a liquid nitrogen tube (4-1-2) connected to a storage cylinder, a liquid nitrogen injection nozzle (4-1-3) in the chamber (1-3) of the piston; an outlet (1-4) through which the mixture of expanded air and gaseous nitrogen is evacuated during the descent of the piston; a piston (3-1) which is coupled to a connecting rod (3-2) and a flywheel (3-5); an engine block (1) and an engine cylinder head (6) made of aluminum alloy or high heat capacity alloy.

2. A liquid nitrogen engine according to claim 1 comprising a cylindrical cavity (5) placed around the piston chamber; a compressed air outlet valve (5-1) which opens in phase with the movement of the piston (3-1) to discharge external air compressed at high pressure and high temperature by the piston (3-1) into the cavity (5); a camshaft (5-2) and associated rods and springs which activate the air outlet valve (5-1); an air outlet (5-3) allowing the high pressure compressed air to be discharged to the outside by the piston (3-1), a thermal insulation (6) being placed around the cavity (5)

3. Liquid nitrogen engine according to claim 2, in which the camshaft (5-2), and the associated rods and springs, can be replaced by an electronic system for activating the air evacuation valve (5-1).

4. Liquid nitrogen engine according to claims 1 and 2, the piston of which has a surface roughness Ra greater than 1.6 pm.

5. Liquid nitrogen engine according to claim 1, comprising a heating plug (7) for the piston displacement chamber, connected to a battery or to an electric generator, making it possible to maintain the piston chamber at a temperature above 300K.

6. A method of operating a liquid nitrogen engine according to claims 1, 3, 4 and 5, comprising the following steps [Fig. 5]: High temperature and high pressure compression by the piston (3-1) of the air sucked from outside, via the air suction (1-2), and which has been injected into the piston chamber (1-3). Then, injection of liquid nitrogen droplets (8) into the piston chamber, when the piston reaches its top dead center, via the injection nozzle (4-1-3) supplied by the pipe (4-1-2), which pipe is connected to a liquid nitrogen cylinder, the injection being electronically controlled by the injection system (4-1). Vaporization of liquid nitrogen upon contact with compressed air at high pressure and high temperature above 400K. Sudden expansion of the air / nitrogen mixture which pushes the piston (3-1), which makes the engine turn. Ejection of the expanded nitrogen / air mixture via outlet (1-4) when it is no longer masked by the piston (3-1). Return to the first step

7. A method of operating a liquid nitrogen engine according to claims 1, 2, 3, 4, and 5, allowing control of the pressure applied to the piston and comprising the following steps [Fig. 6]: -High temperature and high pressure compression by the piston (3-1) of the air sucked from outside, via the air suction (1-2), and which has been injected into the piston chamber (1-3). - Opening of the air outlet (5-1) for the evacuation of high pressure and high temperature compressed air from the piston chamber and ejection of this air into the cylindrical cavity (5), just before the piston reaches its top dead center. -Injection of liquid nitrogen droplets into the piston chamber, which is approximately at atmospheric pressure when the piston reaches its top dead center, via the injection nozzle (4-1-3) fed by the tube (4-1-2), which tube is connected to a liquid nitrogen cylinder, the injection being electronically controlled by the injection system (4-1). -Sudden vaporization of liquid nitrogen on contact with the hot walls of the piston chamber and the surface of the piston. -Sudden release of the nitrogen which pushes the piston (3-1), which makes the engine turn. - Ejection of the expanded nitrogen via outlet (1-4) when it is no longer masked by the piston (3-1). Return to the first step

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