JP2014098351A - Supercharging internal combustion engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve supercharging effect performed by a gas fuel during driving and achieve higher effect than conventional systems in a supercharging internal combustion engine system including a turbocharger which operates supercharging operation by exhaust energy.SOLUTION: A supercharging internal combustion engine system (10) of the invention includes: an internal combustion engine (11); a turbocharger (14); and a gaseous fuel injection valve (168). The gaseous fuel injection valve is provided at intake passages (121, 122) so as to jet a gas fuel toward a compressor wheel (142) of the turbocharger.

Description

  The present invention relates to a supercharged internal combustion engine system including a turbocharger that performs a supercharging operation with exhaust energy.

  In recent years, gaseous fuel such as compressed natural gas (Compressed Natural Gas: hereinafter abbreviated as “CNG”) has attracted attention as a fuel for internal combustion engines from the viewpoint of reducing harmful components in exhaust gas. Various types of systems that can use gaseous fuel have been proposed in the past (see, for example, JP-A-2006-329165).

JP 2006-329165 A

  By the way, compared with liquid fuels, such as gasoline, in gaseous fuels, such as CNG, combustion temperature is low and, therefore, exhaust energy also becomes low. Therefore, in the conventional system of this type, the supercharging effect was low during operation with gaseous fuel. The present invention has been made in view of such problems.

  The supercharged internal combustion engine system of the present invention includes an internal combustion engine and a turbocharger. The internal combustion engine has a cylinder inside. The internal combustion engine is connected to an intake passage through which intake air introduced into the cylinder flows and an exhaust passage through which exhaust discharged from the cylinder flows. The turbocharger includes a turbine wheel and a compressor wheel. The turbine wheel is provided in the exhaust passage so as to be rotationally driven by the energy of exhaust gas flowing through the exhaust passage. The compressor wheel is coupled to the turbine wheel so as to be rotationally driven as the turbine wheel rotates. Further, the compressor wheel is provided in the intake passage so as to pressurize the intake air by being driven to rotate as the turbine wheel rotates.

  A feature of the present invention resides in that the supercharged internal combustion engine system includes a gaseous fuel injection valve provided in the intake passage so as to inject gaseous fuel toward the compressor wheel. Specifically, the gaseous fuel injection valve is provided so that the jet of the injected gaseous fuel collides with the compressor wheel. In this specification, gaseous fuel refers to fuel in a gaseous state at normal temperature and pressure (CNG, liquefied natural gas, liquefied petroleum gas, hydrogen, etc.). On the other hand, fuel in a liquid state at normal temperature and pressure is called liquid fuel (gasoline, light oil, dimethyl ether, alcohol, etc.).

  In the supercharged internal combustion engine system of the present invention having such a configuration, the gaseous fuel is injected toward the compressor wheel. Thereby, the gaseous fuel is supplied to the intake air, and at the same time, the rotation of the compressor wheel is assisted. Therefore, according to the present invention, the supercharging effect during operation with the gaseous fuel can be improved better than before.

1 is a schematic configuration diagram of a supercharged internal combustion engine system according to an embodiment of the present invention. The enlarged view of the compressor wheel vicinity in FIG. The graph for description about the distance of the compressor wheel and gaseous fuel injection valve which were shown by FIG. The figure which shows the modification of a structure of the compressor wheel vicinity shown by FIG. The schematic block diagram which shows the modification of the supercharged internal combustion engine system shown by FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In addition, since a modification will prevent understanding of description of one consistent embodiment, if it is inserted during the description of the said embodiment, it is described collectively at the end.

<Apparatus Configuration of Embodiment>
Referring to FIG. 1, a supercharged internal combustion engine system 10 according to this embodiment includes an internal combustion engine 11, an intake system 12, an exhaust system 13, a turbocharger 14, a liquid fuel injection valve 15, and a gaseous fuel supply unit. 16. In the present embodiment, the supercharged internal combustion engine system 10 is configured to be able to use gasoline as liquid fuel and CNG as gaseous fuel. That is, the supercharged internal combustion engine system 10 of this embodiment is constructed as a so-called “bi-fuel” engine system.

  A cylinder 112 is provided inside an engine block 111 that constitutes a main body portion of the internal combustion engine 11. A piston 113 is accommodated in the cylinder 112 so as to be capable of reciprocating along the central axis of the cylinder 112 (that is, in the vertical direction in FIG. 1). A water jacket 114 that is a passage of cooling water is formed inside the engine block 111 and around the cylinder 112.

  An intake port 115 and an exhaust port 116 are formed in the engine block 111. An intake system 12 is connected to the intake port 115. An exhaust system 13 is connected to the exhaust port 116. Further, the engine block 111 is provided with an intake valve 117 for opening and closing the intake port 115 and an exhaust valve 118 for opening and closing the exhaust port 116.

  Hereinafter, the configuration of the intake system 12 will be described. The intake pipe 121 is connected to the internal combustion engine 11 via the intake manifold 122 so as to supply intake air to the cylinder 112 via the intake port 115. That is, the intake pipe 121 and the intake manifold 122 constitute the “intake passage” of the present invention through which the intake air introduced into the cylinder 112 flows. A throttle valve 123 for adjusting the amount of intake air introduced into the cylinder 112 is mounted at a position downstream of the intake pipe 121 in the intake air flow direction. An intercooler 124 for cooling the intake air supercharged by the turbocharger 14 is mounted at a position in the intake pipe 121 between the turbocharger 14 and the throttle valve 123. A liquid fuel injection valve 15 is mounted on the intake manifold 122. The liquid fuel injection valve 15 is provided so as to inject liquid fuel toward the intake port 115 when the fuel injection port at the tip thereof is exposed in the intake manifold 122.

  Hereinafter, the configuration of the exhaust system 13 will be described. The upstream end of the exhaust pipe 131 in the exhaust flow direction is connected to the exhaust port 116 via the exhaust manifold 132. In other words, the exhaust pipe 131 and the exhaust manifold 132 constitute the “exhaust passage” of the present invention through which the exhaust discharged from the cylinder 112 flows.

  Hereinafter, the configuration of the turbocharger 14 will be described. The turbocharger 14 is configured to pressurize the intake air flowing through the intake pipe 121 by the energy of the exhaust flowing through the exhaust pipe 131. Specifically, the turbocharger 14 includes a turbine wheel 141 and a compressor wheel 142. The turbine wheel 141 is provided on the exhaust pipe 131 side so as to be rotationally driven by the energy of the exhaust gas flowing through the exhaust pipe 131. The compressor wheel 142 is coupled to the turbine wheel 141 via the coupling shaft 143 so as to be rotationally driven as the turbine wheel 141 rotates. In addition, the compressor wheel 142 is provided on the intake pipe 121 side so as to pressurize the intake air by being driven to rotate as the turbine wheel 141 rotates.

  Hereinafter, the configuration of the gaseous fuel supply unit 16 will be described. In the gaseous fuel tank 161, CNG as gaseous fuel is stored in a compressed state (for example, about 20 MPa). A first opening / closing valve 163 is attached to a connection portion between the gaseous fuel tank 161 and the first gaseous fuel pipe 162. The end of the first gas fuel pipe 162 on the downstream side in the flow direction of the gaseous fuel is connected to the regulator 164. A second opening / closing valve 165 is attached to a connection portion between the first gaseous fuel pipe 162 and the regulator 164. The regulator 164 depressurizes the high-pressure gaseous fuel supplied from the gaseous fuel tank 161 to a predetermined pressure (for example, 0.4 MPa) and supplies it to the second gaseous fuel pipe 166. The first on-off valve 163 and the second on-off valve 165 are provided so that the supply state of the gaseous fuel from the gaseous fuel tank 161 to the regulator 164 can be adjusted.

  An end of the second gaseous fuel pipe 166 on the upstream side in the flow direction of the gaseous fuel is connected to the regulator 164. A gas fuel heating unit 167 is provided in the second gas fuel pipe 166. The gaseous fuel heating unit 167 is configured to heat the gaseous fuel supplied from the regulator 164 toward the gaseous fuel injection valve 168 with waste heat generated by the operation of the internal combustion engine 11. Specifically, the gaseous fuel heating unit 167 is provided in the cooling water flow path connected to the water jacket 114 or the exhaust system 13 such as the exhaust pipe 131 so as to exchange heat between the gaseous fuel and the cooling water or the exhaust. It is installed.

  The gaseous fuel injection valve 168 injects the gaseous fuel toward the compressor wheel 142, so that the rotation of the compressor wheel 142 is assisted by the energy of the injected gaseous fuel jet. It is mounted upstream of the compressor wheel 142 in the direction. That is, the gaseous fuel injection valve 168 is provided so as to collide with the compressor wheel 142 while the jet of the injected gaseous fuel has a sufficient penetration force.

  Specifically, referring to FIG. 2, the gaseous fuel injection valve 168 is provided so as to inject gaseous fuel along the flow of intake air flowing toward the compressor wheel 142 (see the white arrow in the figure). (The state of the jet of injected gaseous fuel is indicated by a black arrow). Further, the gas fuel injection valve 168 has a shortest distance D in the direction (refer to the alternate long and short dash line in the figure) between the tip portion 168a that injects the gas fuel in the gas fuel injection valve 168 and the compressor wheel 142. , 50 mm or less.

<Description of operation>
Hereinafter, the operation of the supercharged internal combustion engine system 10 according to the present embodiment having the above-described configuration will be described together with the functions and effects with reference to the drawings as appropriate.

  In the supercharged internal combustion engine system 10 of the present embodiment, the fuel supply mode for the cylinder 112 is selected from among a liquid fuel supply mode for supplying liquid fuel and a gas fuel supply mode for supplying gaseous fuel, depending on the operating state. Is selected (determined) from and is switched between the two depending on the situation.

  Here, in the gaseous fuel supply mode, the exhaust energy is lower than in the liquid fuel supply mode. For this reason, when the turbocharger 14 is driven only by the exhaust energy, the supercharging pressure does not sufficiently increase in the gaseous fuel supply mode, and the supercharging effect (output improvement effect by supercharging) is sufficiently obtained. Concern is raised.

  In this regard, in the configuration of the present embodiment, the gaseous fuel injection valve 168 injects the gaseous fuel toward the compressor wheel 142, so that the rotation of the compressor wheel 142 is assisted by the energy of the injected gaseous fuel jet. . Thereby, the supercharging effect can be obtained satisfactorily even in the gaseous fuel supply mode. The present inventor found that the charging efficiency is higher according to the configuration of the present embodiment than when the gaseous fuel injection valve 168 is attached to the intake pipe 121 downstream of the turbocharger 14 in the intake air flow direction. It has been confirmed by experiments that the effect of improving the shaft torque by 5% at the same time is improved by 5% at the maximum.

  By the way, examples of supercharging assistance by air injection (see Japanese Utility Model Laid-Open No. 61-186742 and Japanese Patent Application Laid-Open No. 2008-286093) are conventionally known. However, in this conventional example, a predetermined time is required to accumulate a predetermined amount of assisting air in the pressure accumulator. For this reason, in such a conventional example, a shortage occurs in the amount of air for assisting in the pressure accumulator, so that supercharging assistance cannot be performed at a necessary time and a supercharging effect may not be obtained. There was a problem. On the other hand, in the configuration of the present embodiment, gaseous fuel that is used for the operation of the internal combustion engine 11 (combustion stroke in the cylinder 112) and stored in a large amount in the gaseous fuel tank 161 is used. Thus, supercharging assistance is performed. Therefore, according to the present embodiment, supercharging assistance can be performed satisfactorily at a necessary time. That is, supercharging assistance can be performed with a good response.

  In the present embodiment, the gaseous fuel jet injected by the gaseous fuel injection valve 168 collides with the compressor wheel 142 while having sufficient penetrating force (energy). Specifically, in the present embodiment, as shown in FIG. 2, gaseous fuel is injected along the flow of intake air that flows toward the compressor wheel 142. Further, the shortest distance D in the direction in which the gaseous fuel is injected between the tip 168a of the gaseous fuel injection valve 168 and the compressor wheel 142 is set to 50 mm or less. Therefore, the rotation assist of the compressor wheel 142 by the energy of the jet flow of the injected gaseous fuel is performed extremely well.

  FIG. 3 shows the effective penetration distance (the position at which the penetration force of the gaseous fuel jet starts to attenuate and the injection when the fuel pressure (pressure of the gaseous fuel supplied to the gaseous fuel injection valve 168) is changed under certain conditions. It is a graph which shows the change of the distance between holes. The experiment for obtaining the graph shown in FIG. 3 was carried out as follows: a commercially available gaseous fuel injector and city gas 13A as the gaseous fuel were used at normal temperature. In a pressurized air atmosphere (28 ° C., 0.1 MPa, average flow velocity 6.8 m / s), gas injection is performed so that the direction of the gas jet makes an angle of 45 degrees with respect to the direction of the air flow (flux). went. The distance between the position where the flow velocity of the injected gas jet was 90% of the value immediately after the nozzle hole and the nozzle hole was determined as the effective penetration distance. The plots indicated by diamonds in the figure are experimental points.

  As shown in FIG. 3, when the fuel pressure is assumed to be a certain value, the shortest distance D in FIG. 2 is less than or equal to a predetermined value determined by the fuel pressure (a value corresponding to a point on the solid line graph in the figure). If so, the jet of gaseous fuel can collide with the compressor wheel 142 before the penetration force is greatly attenuated by the influence of the flow of the intake air. In this regard, in the configuration of the present embodiment, since the regulator 164 is provided, it is possible to control the fuel pressure to be constant in this way. Here, if the graph of fuel pressure vs. effective penetration distance is extrapolated to the position of fuel pressure 0 based on the experimental results, the value of effective penetration distance at fuel pressure 0 is approximately 50 mm. This tendency is the same even if the experimental conditions are changed. Therefore, by setting the shortest distance D in FIG. 2 to 50 mm or less, even if the fuel pressure fluctuates within a range where the operation in the gaseous fuel supply mode is possible, the gaseous fuel having sufficient penetration force for supercharging assistance. Can be made to collide with the compressor wheel 142.

  Further, in the present embodiment, the gaseous fuel supplied toward the gaseous fuel injection valve 168 is heated by effectively using the waste heat generated by the operation of the internal combustion engine 11 in the gaseous fuel heating unit 167. Thereby, the jet velocity of the gaseous fuel injected toward the compressor wheel 142 is improved satisfactorily, and the supercharging assist effect is further improved.

<Modification>
Hereinafter, some typical modifications will be exemplified. In the following description of the modified examples, the same reference numerals as those in the above embodiment can be used for portions having the same configurations and functions as those described in the above embodiment. And about description of this part, the description in the above-mentioned embodiment shall be used suitably in the range which is not technically consistent. Needless to say, the modifications are not limited to those listed below. In addition, a part of the above-described embodiment and all or a part of the plurality of modified examples can be combined appropriately as long as they are technically consistent.

  The liquid fuel injection valve 15 may not be provided. That is, the application target of the present invention is not limited to a so-called “bi-fuel” engine system. Further, the gaseous fuel injection valve 168 may be provided on the downstream side of the turbocharger 14 in the intake air flow direction.

  As described above, even when the shortest distance D is 50 mm or more, a good supercharging assist effect can be obtained by increasing the fuel pressure according to the extension of the shortest distance D. Accordingly, the shortest distance D may be equal to or less than a predetermined value (see FIG. 3) determined by the fuel pressure.

  The number of gaseous fuel injection valves 168 for supercharging assistance may be one as shown in FIGS. 1 and 2, or may be plural as shown in FIG. As shown in FIG. 4, by providing a plurality of gaseous fuel injection valves 168, the supercharging assist effect is further improved, and more precise air-fuel ratio control in the gaseous fuel supply mode becomes possible. .

  The object of application when the present invention is a so-called “bi-fuel” engine system is not limited to a so-called “port injection” gasoline engine as shown in FIG. That is, for example, as shown in FIG. 5, the present invention can be satisfactorily applied to an internal combustion engine 11 (including a diesel engine) that can directly inject liquid fuel into the cylinder 112.

  DESCRIPTION OF SYMBOLS 10 ... Supercharged internal combustion engine system, 11 ... Internal combustion engine, 14 ... Turbocharger, 141 ... Turbine wheel, 142 ... Compressor wheel.

Claims (5)

An intake passage (121, 122) having a cylinder (112) inside and through which intake air introduced into the cylinder flows and an exhaust passage (131, 132) through which exhaust exhausted from the cylinder flows. An internal combustion engine (11) connected;
A turbine wheel (141) provided in the exhaust passage so as to be rotationally driven by the energy of the exhaust gas flowing through the exhaust passage, and connected to the turbine wheel so as to be rotationally driven as the turbine wheel rotates. A turbocharger (14) comprising a compressor wheel (142) provided in the intake passage so as to pressurize the intake air by being driven and rotated.
A gaseous fuel injection valve (168) provided in the intake passage so as to inject gaseous fuel toward the compressor wheel;
A supercharged internal combustion engine system (10) comprising: The supercharged internal combustion engine system according to claim 1,
The liquid fuel injection valve (15) further provided to supply the liquid fuel into the cylinder by injecting the liquid fuel in the intake passage or the internal combustion engine. A supercharged internal combustion engine system. The supercharged internal combustion engine system according to claim 1 or 2,
The supercharged internal combustion engine system, wherein the gaseous fuel injection valve is provided so as to inject the gaseous fuel along a flow of intake air flowing toward the compressor wheel. The supercharged internal combustion engine system according to any one of claims 1 to 3,
The gaseous fuel injection valve is arranged so that a shortest distance in a direction in which the gaseous fuel is injected between the tip (168a) for injecting the gaseous fuel in the gaseous fuel injection valve and the compressor wheel is 50 mm or less. A supercharged internal combustion engine system, characterized in that it is provided. The supercharged internal combustion engine system according to any one of claims 1 to 4,
The gas fuel heating part (167) provided so that the gaseous fuel before being injected by the gaseous fuel injection valve may be heated by the heat generated by the operation of the internal combustion engine is further provided. Supercharged internal combustion engine system.

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