RU2167316C2 - Multifuel internal combustion engine and method of its operation - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: proposed method of operation includes air intake into cylinder, compression of air with partial bypass into swirl chamber, injection of fuel in process of compression into connecting channel with transfer of part of fuel into swirl chamber and formation of fuel-air mixture in swirl chamber, ignition of fuel-air mixture by glow plug, ejection of burning gases from swirl chamber into main space of combustion chamber, expansion of combustion products and discharge of exhaust gases. Fuel is injected into widened space of connecting channel towards flowing air. Swirl chamber has heating insert and glow plug. Connecting channel, nozzle and swirl chamber are arranged at angle to piston which is provided with wedge combustion chamber with turbolator. EFFECT: reduced consumption of fuel and toxicity of exhaust gases. 3 cl, 2 dwg

Description

 The invention relates to mechanical engineering, i.e. to the class of multi-fuel internal combustion engines (ICE) of a two-chamber design with an electric spark method of ignition of a pre-chamber charge.

 The present invention can be implemented both in the internal combustion engine of a tractor type, and in large dimensions, for example, diesel, marine in stationary and transport performance, as well as in piston aviation.

 Widely known methods of mixing, based on the use of energy flow during compression-mixing and expansion-combustion.

 The closest technical solution is the invention SU 1810593 A1, 04/23/1993, F 02 B 19/10. The essence of which: fuel is injected into the broadening cavity of the connecting channel, moreover, the finely dispersed part of the fuel jet is transferred to the pre-chamber by the bypassed air, and the coarse part of the jet is deposited on the walls of the broadening cavity in the form of a film that is evaporated by burning gases ejected from the pre-chamber.

 The disadvantage of the prototype is that it does not provide efficient operation at various speed modes with equally high rates in terms of efficiency, power and environmental performance.

 This is due to the fact that there is no stability of ignition in the pre-chamber due to different conditions of atomization of the fuel, depending on the speed of the engine.

Spraying fuel at a specific set value of the injection pressure of the nozzle is regulated by the dynamics of fuel supply, i.e. the law of supply or the cam profile of the high-pressure fuel pump, so the amount of fuel injected by the nozzle during the initial fuel supply period of 10 - 12 ^o p.p. remains constant regardless of the speed of the engine. Due to the prevailing influence of the pneumatic component in the process of fuel atomization, it should be noted that when the engine speed is changed from 800 to 2000 min ^-1 , the mixture will flow from the main volume to the additional one from 98 to 247 m / s, which is comparable with the injection pressure 8 to 45 MN and will cause a sharp increase in fineness of spray.

 It should also be noted that the walls of the broadening cavity (heated engine) have approximately the same temperature as the charge, therefore, when the front of the fuel plume reaches the wall, the entire unevaporated part of the fuel actually settles and heats up on it. When fuel settles on the wall, a thin film is formed, which quickly warms up from the metal wall, since the heat transfer coefficient from metal to the fuel film is very large and many times exceeds the heat transfer coefficient from air to fuel droplets, the heating and evaporation of which takes no more than 10 cal . Therefore, the time of heating and evaporation of fuel on the wall can almost be neglected; this time is immeasurably less than the movement of the torch toward the wall and does not exceed 0.1 ms.

 These factors question the possibility of the existence of a fuel film in the conditions of the connecting channel for a long time and shed light on the causes of unstable ignition of the fuel in the prechamber.

 Differences in fineness of atomization and the lack of organized movement of the air-fuel mixture in the prechamber lead to the appearance of local centers of re-enrichment due to the uncertain trajectory of the droplets of fuel (regardless of their dispersion), including near the spark plug electrodes.

 A flat nozzle does not provide all-mode maintenance of the dynamics of heat generation within specified limits, i.e. increasing the pressure of the combustion products in the prechamber and its flow part is a passive element that performs its function only in certain modes, from the point of view of increasing the pressure of the combustion products in the prechamber, which leads to inefficiency of the displacer.

 The objective of the invention is to increase fuel efficiency and reduce exhaust emissions.

 The solution to this problem lies in the fact that fuel is injected into the expanded cavity of the connecting channel towards the bypassed air in order to obtain uniform dispersion during combustion during the backflow of hot gases from the vortex chamber, the expanded cavity acts as a thermoenergy battery, reducing heat losses and increasing the flame velocity in the local plot of fuel intake of the final part of the injection, which favorably affects the maintenance of the dynamics of the combustion process.

 In FIG. 1 shows the proposed internal combustion engine (ICE), a cross section; in FIG. 2 is a view of a combustion chamber (in a piston) with a turbulator, and also a projection of an additional chamber nozzle onto the piston plane.

 The engine includes a cylinder 1, a piston 2 with rings, and also the main cavity of the combustion chamber 3 with turbulator 4 located therein, a cylinder head 5 with an additional vortex chamber 6 located in it, which communicates with the main cavity of the combustion chamber in the piston by means of a number of structural elements connecting channel. The composite connecting channel includes those placed on a common longitudinal axis, i.e. coaxially sequentially, three sections of the channel of different cross sections, i.e. two smaller 7 and 8, the first is paired with the output nozzle 9, made in the form of a Laval nozzle, the latter is adjacent to the vortex chamber. Between these sections is a section of a larger cross section 10. The atomizer 11 of the nozzle 12 is perpendicular to the section of a larger cross section.

 In the vortex chamber 6, an electric spark plug 13, a glow plug 14, and the lower and opposite part of the vortex chamber are equipped with a heat-insulating (insulating) insert 15. An inlet 16 and an outlet valve are installed in the cylinder head.

 The engine operates as follows.

 When the piston 2 moves from the top dead center (TDC) to the bottom dead center (BDC) at the intake stroke, the engine cylinder through the open intake valve 16 receives fresh charge (atmospheric air) due to the resulting vacuum, filling the over-piston space, as well as the main chamber cavity combustion 3. The end of the intake stroke is regulated, as usual, by the filling phase. At the end of this phase, the intake valve 16 closes. With further movement of the piston 2 from BDC to TDC and closed valves in cylinder 1, the compression stroke begins. In the main cavity of the combustion chamber 3, displacement vortex formation occurs, as shown in FIG. 1. At the same time, sequentially through a composite connecting channel, including the nozzle channel 9, channels of a smaller cross section of 7.8 and greater than 10, under the influence of an interchamber pressure drop, part of the cylinder charge flows from the main 3 into the vortex chamber of the main cavity of the combustion chamber.

 Near TDC, i.e., in the fuel supply phase, by means of a high-pressure fuel pump (high-pressure pump) (not shown) through the nozzle 12 and atomizer 11, fuel is injected into the section of the connecting channel 10 of a larger section, towards the flowing air charge.

 In the process of fuel supply, the cyclic dose of fuel is divided in accordance with the presence of an air charge in the cavities of the combustion chamber at the time of supply of the spark discharge, taking into account the continuing fuel supply during the ignition delay period.

This separation is due to the fact that the dynamics of fuel supply is regulated by the law of supply, the cam profile of the high-pressure fuel pump, which is required to ensure the first 15 ^o of cranked (p.c.v.) fuel supply, the composition of the mixture in the vortex chamber within the flammability range α = 0, 5 - 2.5.

 After the start of fuel supply, all atomized fuel enters the vortex chamber 6 through a channel 8 located tangentially, creates a rotational movement of the charge in the chamber, which has a beneficial effect on the mixture formation of fuel vapor with air. During a vortex, the temperature drops significantly less due to the additional intake of air, which explains the more complete evaporation.

 The presence of the insulating insert 15 and the glow plug 14 stimulates an improvement in evaporation and a reduction in the ignition delay period.

After 5 - 10 ^o p.c. fuel supply when the composition of the mixture in the vortex chamber 6 is reached α = 1.5 - 2.0, depending on the speed mode of the internal combustion engine, high voltage voltage is applied to the electrodes of the spark plug 13. After which, pre-flame reactions develop in it.

Due to a higher temperature in the vortex chamber by 150 - 250 ^o C, the presence of an organized vortex movement, a heat insulating insert and a glow plug, the ignition delay is significantly reduced with respect to single-chamber modifications of the ignition delay and amounts to 1 - 3 ^o for diesel fuel, for A-76 gasoline 3 - 5 ^o .

 During the ignition delay period, the composition of the vortex chamber charge is somewhat enriched to α = 0.8 - 1.2 and the phase of visible combustion begins, accompanied by a sharp increase in pressure in the vortex chamber 6 and the beginning of the backflow of flame gases into the main cavity 3 of the combustion chamber.

 The backflow of the flame of the flame gas collides in section 10 with the fuel of the ongoing fuel supply process. The large cross-sectional diameter 10 has a beneficial effect on accelerated evaporation, the occurrence of pre-flame reactions and the ignition of this fuel through a local decrease in heat loss to the walls and an increase in flame speed [1], further stimulating turbulent combustion of the final part of the injection.

 All-regime regulation of the increase in pressure of the combustion products, i.e. maintaining the dynamics of heat generation within specified limits, by creating certain pressure ratios at the outlet of the vortex chamber, which vary in proportion to the engine load and provide constant, predetermined conditions for the development of the combustion process in the combustion chamber, and also use a concomitant increase in the rate of expiration of the combustion products to improve mixture formation in main volume. This is due to the fact that the flame gases, as well as the unburned part of the fuel in the vaporized and finely dispersed state, enter the main combustion chamber 3 through the Laval nozzle 9 connected to it.

 The burnout of the charge of the vortex chamber with acceleration of the backflow, and therefore turbulization in the main cavity of the combustion chamber 3, provides, along with the intensive flow of mixture-forming processes, also quick burnout of the charge in this cavity near the TDC on the expansion stroke with a corresponding improvement in the working cycle efficiency indicators.

 After the combustion and expansion process is completed, the exhaust valve opens and the cylinder of the engine 1 is cleaned when the piston moves from BDC to TDC from exhaust gases. The work cycle ends and is periodically repeated.

To ensure the efficiency of the engine on various fuels, speed and load conditions, taking into account other structural and operational factors using appropriate structural elements and automatic machines, the lead angle of the beginning of the fuel supply varies in the range of 24 - 18 ^o p.p. inside. Within this interval, the angle changes ignition timing.

To ensure the most efficient processes of mixture formation and combustion, smokeless work on the entire range of engine operating modes and all types of liquid fuels (gasoline, kerosene, diesel fuel, gas condensate, etc.), the relative volume of the vortex chamber a = V _k / V _s is selected within a = 0.3-0.6, preferably spherical in shape.

 The calculation of the geometric parameters of the Laval nozzle is based on the calculation of the expansion and expiration of combustion products in the nozzle [2].

To determine the rate of discharge of combustion products from the vortex chamber, it is necessary to know the temperature T _a , pressure P _a and their composition in the outlet section of the nozzle. These parameters can be determined by thermal calculation of the engine.

The nozzle exit area is determined
F _a = V _a / ω _a , (1)
where V _a is the actual specific volume of combustion products in the outlet section of the nozzle at a gas constant R _a of combustion products and the actual temperature T _a , as well as the calculated compression pressure P _a at the outlet of the nozzle;
ω _a - the rate of flow of combustion products from the nozzle.

The area of the smallest section of the nozzle
F _cr = V _k / ω _cr , (2)
where V _k is the specific volume of the combustion products at T _{to the} temperature at the outlet of the vortex chamber, P _k is the pressure in the vortex chamber in front of the nozzle and R _k is the gas constant of the combustion products in the smallest section of the nozzle;
ω _cr - the rate of flow of combustion products in the smallest section of the nozzle.

A factor affecting the area of the connecting channel F _to , sections 7.8, is the relative area
f _k = F _k / F _cr (3)
The determination of the relative area is determined by a number of reasons:
1. The possibility of using the flow energy in the compression-combustion process to give the nozzle only dosing functions;
2. An economically optimal mode of consumption of combustion products and at the same time maintaining the dynamism of the combustion process;
3. Least throttling;
4. Limited structural dimensions.

It should be noted that the use of cameras with f _k <2 in the experiments did not give positive results, stable operation was observed only at idle and partial loads. In chambers with f _k = 1, the effect of flame suppression was generally observed.

According to the calculations for the UD-15 engine, converted to a multi-fuel version and based on the choice of the optimal flow rate and criteria for combining the area of the connecting channel and the smallest nozzle cross-section, we have the following values: connecting channel area F _k = 100 mm ² , the smallest nozzle cross-sectional area F _cr = 11.6 mm ² , the area of the output section of the nozzle F _a = 30 mm ² .

Given the generally accepted view that the diameter of the connecting channel is directly dependent on the volume of the additional chamber, within the studied values of the ratios of volumes and diameters of the connecting channel, we find the optimal ratios for F _to from the studied range V _to / F _to = 8.5 -17 ,5; V _k / F _k = 10 and for F _cr from the studied range of V _k / F _k = 40 - 20; V _to / F _cr = 25.

In practice, a smaller section of the connecting channels 7; 8 with a diameter of 8 -12 mm is selected from the condition of ensuring the optimal flow rate during compression-mixture formation for a nominal speed mode of 2000 min ^-1 .

 Their lengths are determined by the traditional l / d ratio, for section 7 l / d = 1 - 3, for section 8 l / d = 0.5 - 2.

 The diameter D of section 10 of larger diameter is selected in the range D = d (1.1 - 1.4), length D (1 - 1.5).

 In connection with the transience of the combustion process and the slowness of the homogenization process on a diffusion basis, the constructive variant of homogenization (uniform distribution of fuel in the air charge) is based on the principle of organized vortex formation with mutual coordination of the shapes and sizes of the nozzle channel with the corresponding structural elements of the turbulator 4 of Fig. 2.

With this in mind, the axis of symmetry of the connecting channel relative to the plane of the piston is located at an angle of 25 ^o with possible variations of 20 - 40 ^o . The main cavity of the combustion chamber in the wedge-shaped piston is bounded from the side opposite the nozzle by a large turbulator 4 of FIG. 2 specified forms.

Due to the absence of valves in the main plane of the combustion chamber, the turbulator can be made to protrude beyond the central axis of symmetry of the piston, as well as use smoother mates with the surface of the piston. It is important that the front of the combustion chamber adjacent to the nozzle is a surface having an inclination angle equal to the angle of the nozzle solution, a line of its extension until it intersects with the axis of symmetry of the piston, with smooth coupling, as in FIG. 1. The angle of the nozzle in the vertical plane is selected 5 ^o from the axis of symmetry. In this case, the angle of inclination of the plane of the front of the combustion chamber is 30 ^o .

The angle of the cone of the combustion chamber in the horizontal plane of the piston of figure 2 is selected in the range of 50 - 70 ^o , in this case 60 ^o .

The nozzle exit hole is made in the form of an ellipse with a larger (horizontal) axis (2 - 4) d _cr , smaller (vertical) (1 - 2) d _cr , the nozzle length is selected 10 - 30 mm.

 Such a device of the structural elements of the combustion chamber provides not only a high level of charge homogenization in its main cavity 3, but also a more complete burning of this charge both with respect to analogues and the prototype.

With the correct choice of the above defining characteristics of the structural elements of the engine, smokeless engine operation is ensured when the injector spring is tightened P _f = 0.1 - 0.5 MN. In this case, it is recommended to use single-hole or open nozzles with an opening directed towards the flowing mixture at the compression stroke.

 With such a low level of fuel supply pressure, the high-pressure pump and nozzles operate in a very light mode, and this guarantees a sharp increase in the motor resource of the fuel supply equipment. However, in this constructive version, optimal modeling of the supply law (cam profile of the injection pump) is required, which is feasible on the basis of calculating the dynamics of changes in the composition of the mixture in the vortex chamber.

где a - объем вихрекамеры;
В - коэффициент дросселирования наименьшего сечения соединительного канала;
f(б) - функция поворота коленчатого вала.α = G _in / 15G _t , (4)
where G _in is defined as

where a is the volume of the vortex chamber;
In - throttling coefficient of the smallest section of the connecting channel;
f (b) is the crankshaft rotation function.

 The use of a 50-100 W glow plug [3] located on the symmetry axis of the connecting channel, as well as a heat insulating insert together with an electric spark plug using a compression ratio of 12-14 creates an equivalent effect of increasing the polytropic compression ratio, which reduces the effect of octane and cetane the number of fuels used, as well as the composition of the mixture on the ignition process.

 Due to the prevailing influence of the pneumatic component during the atomization of the fuel, a higher level of dispersion and homogenization in the cavities of the combustion chamber is achieved in relation to traditional mixing schemes. Both of these mixture-forming factors stimulate a sharp reduction in emissions of toxic components of CO and CH with the exhaust gases of the engine.

The shift in the combustion of the bulk of the charge of the main cavity 3 to its final phases, combined with the short duration of the high-temperature effect, respectively provide a reduction in the emission of the most toxic component N _ox with the exhaust gases of the engine.

 Due to the high efficiency of the preparatory processes in the vortex chamber-composite compound channel, which provides gasification of the fuel charge before entering the main cavity of the combustion chamber 3 in combination with a highly controlled turbulent homogenization process, an approximation of the charge composition in the main cavities of the combustion chamber close to α ≈ 0.95, completely eliminating smoky exhaust, which stimulates, together with an increase in the frequency of rotation of the internal combustion engine, the liter level ty.

 The intensive course of evaporation and ignition processes, the elimination of the effect of fuel accumulation in the main cavity of the combustion chamber 3 during the ignition delay period increases the measure of controllability of the heat release process and the pressure increase ΔP / Δγ by the fuel supply law, regulated by the injection pump cam profile, on all types of liquid fuel, which also stimulates increase engine life.

 A weak dependence on the temperature regime of the charge during compression and the initial stages of fuel ignition, combined with a high controllability of the combustion process, providing soft detonation-free operation of the engine, makes it possible to burn all types of liquid fuels with the most efficient thermodynamic compression ratios ε = 12 - 14.

Literature
1. Sviridov Yu. B. Mixture formation and combustion in diesel engines. - L .: Engineering, 1972, p. 126, 151, 164 - 168, 180 - 185, 209 - 218.

 2. Kulagin I.I. Theory of liquid jet engines. - The Ministry of Defense of the USSR, 1972. - 518 p.

 3. Vohmin D. M. The use of a glow plug in a multi-fuel engine // Tyumen, Tsogu // Proceedings of the conference "Operation of technological transport and special equipment in the sectors of the fuel and energy complex", 1997.

Claims (2)

 1. The method of operation of a multi-fuel internal combustion engine by introducing air into the cylinder, compressing the air in the cylinder with transferring part of it to the vortex chamber, injecting fuel during compression into the connecting channel with transferring part of it by the bypassed air into the vortex chamber and forming the last air-fuel mixture, igniting the mixture in the vortex chamber from the spark plug, the discharge of burning gases from the vortex chamber with the transfer of the rest of the fuel to the main cavity of the combustion chamber, combustion of fuel, expansion of the combustion products and exhaust gas discharge, characterized in that the fuel is injected into the expanded cavity of the connecting channel towards the flowing air in order to obtain uniform dispersion, in the process of combustion during the backflow of burning gases from the vortex chamber, the expanded cavity acts as a thermal energy accumulator, reducing heat loss and increasing the speed of the flame.  2. An internal combustion engine comprising at least one cylinder with a piston placed therein with a combustion chamber in it, a cylinder head, a vortex chamber having a spark plug placed in the head and communicated with the main cavity of the combustion chamber using a connecting channel made of coaxial successively interconnected sections of a smaller section adjacent to the vortex chamber and the outlet nozzle, as well as a section of a larger section between them, as well as an expanding nozzle adjacent to the main cavity of the chamber with Gorania, and a fuel nozzle with a spray located in the connecting channel, characterized in that the vortex chamber has an insulating insert and a glow plug, the connecting channel, nozzle and vortex chamber are located at an angle to the piston, in which there is a wedge-shaped combustion chamber with a turbulator, and expanding the nozzle is made in the form of a Laval nozzle.

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