RU2451802C1 - Optimising combustion product expansion in piston engine cylinder with working medium feed from free-piston gas generator with external combustion chamber - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: method is intended for free-piston gas generator with external combustion chamber, piston expansion machine with intake and discharge valves with electropneumatic drive and control system and consists in optimising combustion product in cylinder by intake valve control system. For this, control system tracks position of piston in expansion machine cylinder to open intake valve at the beginning of working stroke with piston at BDC. With piston changing into TDC, control system closes intake valve.

EFFECT: higher efficiency of expansion.

1 dwg

Description

FIELD OF TECHNOLOGY

The invention relates to power engineering.

BACKGROUND

The closest analogues of the claimed invention are patents RU 2324060 C1 “Free-piston gas generator of a ram engine with two compressor drive pistons” and RU 2324830 C1 “Free-piston gas generator of a ram engine with one piston of compressor drive”.

The principle of operation of both gas generators is largely similar. Therefore, it is enough to consider the principle of operation of one of them, namely the “Free-piston gas generator of a ramjet engine with two compressor drive pistons”.

When starting the gas generator with an external combustion chamber (hereinafter referred to as the gas generator), fuel is supplied to the combustion chamber 1 (see the figure) by the nozzle 2 and ignited by the spark plug 3. Combustion products through the gas distribution valve (hereinafter referred to as patent valve RU No. 2349765 C1, “ The pneumatic valve actuator of a single-stroke free-piston engine with an external combustion chamber ") 4 enters the left cavity of the compressor drive piston 5, as a result of which the piston 5 and the piston of the compressor 7 connected to it by the piston rod 6 move (according to the figure) from left to right. Since the area of the left (in the figure) surface of the piston 5 is larger than the area of its opposite surface by the cross-sectional area of the rod 6, the air pressure in the cavity to the right of the piston 5 (compressor cavity) is greater than the pressure of the combustion products to the left of the piston 5. Therefore, the air from the right piston cavity 5 (compressor cavity, the valve 8 is closed) through the valve 9 enters the combustion chamber 1, thereby providing air to the fuel combustion process. At the same time, when the piston 7 moves, air (from the following combustion products) from its right cavity through the valve 10 (valve 11 is closed) is released into the atmosphere, and through the open valve 12, air from the atmosphere is sucked into the left piston cavity 7. When the pistons reach 5 and 7 of the rightmost position, the control system (not shown in the figure) translates valves 4 and 10 into opposite positions. Now, the combustion products from the combustion chamber enter the right cavity of the piston 7, and the pistons 5 and 7 move from right to left. Air from the left cavity of the piston 7 opens the valve 11 and enters the combustion chamber 1. The valve 9 closes and air from the atmosphere through the opened valve 8 is sucked into the right cavity of the piston 5. As soon as the pressure of the combustion products in the combustion chamber reaches the operating value, the shutter 13 and combustion products enter the expansion machine.

From the description of the principle of operation of the gas generator, it is seen that the combustion products from the combustion chamber enter its cylinders throughout the movement of the pistons from one extreme point to another, while the temperature and pressure of the combustion products entering the cylinders practically does not differ from their pressure in the combustion chamber. The main expansion of the combustion products occurs in the exhaust valve when they are released in the period from opening to closing the exhaust valves 4 or 10. However, their energy does not do any useful work. For efficient energy conversion of expanding combustion products, it is necessary to organize their expansion directly in the cylinder of the expansion machine of the gas generator - application No. 2011919000 "Optimization of the expansion process of the combustion products of a free-piston gas generator with an external combustion chamber", arrival date 05/11/2010, incoming No. 026958. By analogy with the internal combustion engine, the cylinder of the gas generator can be divided into two volumes. The first, smaller, corresponds to the combustion chamber of the internal combustion engine - a virtual combustion chamber. Depending on the direction of movement of the piston group, it is alternately located with one or the other cylinder head. The remaining volume of the cylinder, in fact, as in the internal combustion engine, is the virtual working volume. At the beginning of the working cycle, when the piston group is at the starting extreme point of movement (for example, in the figure, to the left), the control system opens the intake valve 4 and the combustion products from the combustion chamber enter the virtual combustion chamber of the cylinder, the temperature and pressure of which are almost equal to those in the combustion chamber 1. The pistons begin to move from left to right and, when they pass the virtual combustion chamber, the control system closes the intake valve 4, stopping the access of combustion products to the cylinder. From this moment, the actual process of expansion of combustion products begins. The timing of the opening and closing of the gas control valve — the duration of the inlet of the combustion products into the cylinder — the control system determines, taking into account the temperature and pressure of the combustion products, in such a way as to ensure maximum efficiency of the process of their expansion in the virtual working volume of the cylinder. Thus, the working cycle from a thermodynamic point of view is similar to that in a diesel engine. The difference is that the stroke length of the piston group in the cylinder does not depend on the design of the crank mechanism, which is simply not in the power module, and is determined by the control system based on the requirement to ensure optimal expansion of the combustion products and noiselessness in accordance with the physicochemical characteristics of the used currently fuel.

SUMMARY OF THE INVENTION

The purpose of the invention is to optimize the expansion of combustion products in the cylinders of an engine expansion machine with cylindrical or rotary pistons, converting the exothermic energy of motor fuel into mechanical energy of rotation of the power take-off shaft. The optimization of the expansion of combustion products in the cylinder is carried out by a control system using an inlet valve with an electropneumatic actuator; patent RU No. 2349765 C1, “Pneumatic valve actuator of a single-stroke free-piston engine with an external combustion chamber,” has already been mentioned. The control system monitors the position of the piston in the cylinder of the expansion machine and, when the piston is at the initial extreme point of movement, opens the inlet valve during a working stroke. After the piston has passed part of the total piston path in the cylinder, the control system closes the inlet valve at the moment providing an efficient process of expansion of the combustion products with the further movement of the piston to the extreme point of movement. Thus, the process of expansion of combustion products is similar to that in a diesel engine.

SUMMARY OF THE INVENTION

A method for optimizing the expansion of combustion products in a cylinder of a piston engine powered by a free piston gas generator with an external combustion chamber, including a free piston gas generator with an external combustion chamber, a piston expansion machine with inlet and outlet valves with an electropneumatic actuator and a control system, characterized in that the optimization the expansion of the combustion products in the cylinder is carried out by the intake valve control system, for which the control system monitors It sets the position of the piston in the cylinder of the expansion machine and, when the piston is at the initial extreme point of movement during the working stroke, opens the inlet valve and, after the piston passes part of the common piston path, closes the inlet valve when the piston moves further to the extreme point of movement.

INDUSTRIAL APPLICATION

The implementation of a method for optimizing the expansion of combustion products of a free-piston gas generator with an external combustion chamber does not require the development of any new technologies and is capable of any engine-building production.

GRAPHIC MATERIAL

Figure. Schematic diagram of a free-piston gas generator with an external combustion chamber.

1 - combustion chamber, 2 - nozzle, 3 - spark plug, 4, 10 - gas distribution valves, 5, 7 - pistons, 6 - stem, 8, 9, 11, 12 - check valves, 13 - damper.

Claims (1)

A method for optimizing the expansion of combustion products in a cylinder of a piston engine powered by a free piston gas generator with an external combustion chamber, including a free piston gas generator with an external combustion chamber, a piston expansion machine with inlet and outlet valves with an electropneumatic actuator and a control system, characterized in that the optimization the expansion of combustion products in the cylinder is carried out by the intake valve control system, for which the control system It lives the position of the piston in the cylinder of the expansion machine and, when the piston is at the initial extreme point of movement, opens the inlet valve during a working stroke, and after the piston passes part of the common piston path, closes the inlet valve when the piston moves further to the extreme point of movement.

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