KR100853270B1 - Ignition control method of hcci combustion and hcci engine - Google Patents

Abstract

A method of controlling the ignition time of homogeneous charge compression ignition(HCCI) and a HCCI engine are provided to maximize the thermal efficiency and minimize harmful matter in exhaust gas by burning an air-fuel mixture when a piston is located neat the top dead center of a cylinder. A method of controlling the ignition time of HCCI which is ignited after fuel and air are evenly premixed in a cylinder includes the first step of jetting reserve fuel before the top dead center one or more times(S100), and the second step of jetting control fuel before the ignition of the reserve fuel(S200). The first step is performed at the bottom dead center. The second step is performed at 25 to 35 degrees before the phase of a crank shaft reaches the top dead center. A HCCI engine is constructed so that fuel is jetted into a cylinder by an injector to be premixed with air in the cylinder, and thereafter the air-fuel mixture is ignited under constant pressure and temperature. The injector jets the fuel two or more times, jets reserve fuel one or more times before the top dead center, and jets control fuel before the reserve fuel is ignited. The reserve fuel is jetted when the phase of a crank shaft is located at the bottom dead center, and the control fuel is jetted at 25 to 35 degrees before the phase of the crank shaft reaches the top dead center.

Description

Combustion timing control method of premixed compression ignition combustion and premixed compression ignition combustion engine {IGNITION CONTROL METHOD OF HCCI COMBUSTION AND HCCI ENGINE}

1 is a schematic diagram of a premixed compression ignition combustion engine according to one embodiment of the invention,

2 is a flowchart illustrating a method of controlling a combustion time of premixed compression ignition combustion according to an embodiment of the present invention;

3 is a view showing the relationship between the phase of the crankshaft, the cylinder pressure, the heat generation rate in accordance with an embodiment of the present invention,

4 is an enlarged view illustrating a relationship between a phase of a crankshaft, a cylinder pressure, and a heat generation rate according to an embodiment of the present invention;

Figure 5 is a graph measuring the exhaust gas component and the output of the pre-mixed compression ignition combustion controlled combustion time in accordance with an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: drive unit 200: control unit

300: fuel supply unit 400: exhaust gas component measurement unit

500: cooling unit 110: cylinder

120: piston 110a: top dead center

110b: bottom dead center 130: crank

340: Injector 240: Injector driver

The present invention relates to a method for controlling the combustion timing of premixed compression ignition combustion and to a premixed compression ignition combustion engine, and more particularly, to preliminary fuel by latent heat of the control fuel by injecting the control fuel before the start of combustion of the preliminary fuel. The present invention relates to a method for controlling the combustion timing of premixed compression ignition combustion and a premixed compression ignition combustion engine.

Premixed Combustion Combustion Ignition (HCCI) is a combustion method in which the combustion is carried out by uniformly premixing fuel and air inside a cylinder, unlike conventional diesel combustion diffusion combustion. It is a revolutionary combustion technology that can reduce nitrogen oxides (NO _x ) and particulate matter (PM) simultaneously by making it favorable.

In detail, the characteristics of the premixed compression ignition combustion are as follows. First, the premixed compression ignition combustion is basically a compression ignition method. The thermal efficiency of can be obtained. In addition, since combustion is simultaneously performed from multiple ignition sources, compared to spark ignition (SI), there is no flame propagation and the combustion period is very short, thereby reducing the cycle time loss.

Secondly, the premixed compression ignition combustion pursues lean combustion, so that the combustion temperature is low to suppress the generation of nitrogen oxides, and since the combustion is performed in a uniform mixture of fuel and air, it is caused by the lack of oxygen in a local heterogeneous mixer. It can reduce particulate matter. This has the effect of fundamentally solving the harmful components of the exhaust gas in the combustion stage.

Finally, since premixed compression ignition combustion is based on compression ignition, most fuels capable of compression ignition regardless of liquid fuel or gaseous fuel can be used. That is, all kinds of fuels capable of compression ignition such as gasoline, diesel, hydrogen, general gas fuel, and dimethyl ether (DME) can be applied. In addition, there is an advantage that can be applied regardless of the size of the engine from a small two-wheeled motorcycle engine to a large marine engine, power generation engine.

In other words, the premixed compression ignition engine can be seen to combine only the advantages of gasoline engine and diesel engine.

Despite these advantages, premixed compression ignition combustion has not been put to practical use due to problems such as difficulty in ignition timing control and limited operating range. In other words, diesel and gasoline engines can be ignited optimally near the top dead center (TDC) depending on the timing of fuel supply and the ignition timing of the spark plugs. After premixing, it is difficult to control the combustion timing because it is compressed and spontaneously ignited.

Therefore, the commencement of combustion of the mixer is so fast that combustion proceeds during the compression stroke of the piston, which causes mechanical overload in the engine, resulting in low thermal efficiency.

The present invention was devised to solve the above problems, and an object of the present invention is to premix the piston when the piston is located near the top dead center of the cylinder to maximize the thermal efficiency while minimizing the harmful substances in the exhaust gas. The present invention provides a method for controlling the combustion timing of compression ignition combustion and a premixed compression ignition engine.

Combustion timing control method of the pre-mixed compression ignition combustion according to an embodiment of the present invention for achieving the above object is a pre-mixed compression ignition combustion (HCCI: Homogeneous) that is burned after the fuel and air uniformly premixed in the cylinder A method of controlling a combustion timing of a charge compression ignition, comprising: a first step of injecting a reserve fuel at least one time before a top dead center (TDC) and a second step of injecting a control fuel before the start of combustion of the preliminary fuel; It is made, including.

In a preferred embodiment, after the first step, the preliminary fuel is mixed with air in the cylinder and compressed in the cylinder, and after the second step, the temperature inside the cylinder is evaporated. Step 2-1, which is lowered to a predetermined temperature by a latent heat and then rises again, step 2-2 and the mixer in which a mixer in which the preliminary fuel, the cylinder air, and the control fuel are mixed is compressed in the cylinder; Further comprises the second to third steps of initiating combustion at a constant temperature and pressure.

In a preferred embodiment, the second step takes place between 25 degrees and 35 degrees before the top dead center of the crankshaft.

In a preferred embodiment, the first step is at a bottom dead center (BDC).

The premixed compression ignition engine according to an embodiment of the present invention for achieving the above object is an example in which fuel is injected into the cylinder by the injector and premixed with the air in the cylinder, and then compressed and burned at a constant pressure and temperature In a Homogeneous Charge Compression ignition (HCCI) engine, the injector injects the fuel at least two times, injecting at least one preliminary fuel before the top dead center (TDC), and the preliminary Control fuel is injected before the fuel is burned.

In a preferred embodiment, the injector injects the control fuel at a phase of the crankshaft between 25 degrees and 35 degrees before top dead center.

In a preferred embodiment, the injector injects preliminary fuel at the bottom dead center (BDC) of the crankshaft phase.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a schematic diagram showing a premixed compression ignition combustion engine according to one embodiment of the invention.

Referring to FIG. 1, the mixed mixture ignition combustion engine according to an exemplary embodiment of the present invention includes an injector 340 and a cylinder 110.

Premixed compression ignition combustion engine is a fuel 310 is supplied to the inside of the cylinder 110 and uniformly premixed with the air in the cylinder 110 and then spontaneously combusts when the pressure rises to a constant pressure and temperature by the compression stroke of the piston. It is an engine.

In addition, the premixed compression ignition combustion engine according to an embodiment of the present invention comprises a driving unit 100, the control unit 200, the fuel supply unit 300, the cooling unit 500, the injector 340 The fuel supply unit 300 is provided, and the cylinder 110 is provided in the drive unit 100.

The injector 340 injects fuel 310 into the cylinder 110 under the control of the injector driver 240.

In the premixed compression ignition combustion method, a method of injecting fuel 310 into a cylinder 110 is generally performed, wherein the fuel 310 is premixed with air inside the cylinder 110 to form a mixer, and the mixer is a piston ( Compressed by 120) to increase temperature and pressure, and to spontaneous combustion of the mixer at a constant pressure and temperature, premixed according to the timing of injecting fuel 310 into the cylinder 110. Combustion characteristics of compression ignition engines also vary.

In general, the slower the timing of the fuel 310, the slower the progress of combustion, the slower the progress of combustion, the slower the progress of the combustion output (IMEP: INDICATED MEAN EFFECTIVE PRESSURE) has the advantage of rising, but the fuel 310 and the cylinder 110 ) The internal air is premixed, so that the mixed state is not good, so that a large amount of nitrogen oxides are discharged after combustion.

Therefore, the premixed compression ignition combustion engine and the combustion method according to the embodiment of the present invention inject the fuel 310 into the cylinder 110 a plurality of times, and the fuel injected into the plurality of circuits is simultaneously burned. Unlike the method of injecting into the first stage, it was observed that as the fuel injection time is delayed, the combustion start time is not delayed proportionally.

Meanwhile, in one embodiment of the present invention, the fuel 310 is divided into two injections, and the fuel injected first is defined as the control fuel as the fuel injected later as the reserve fuel.

In addition, the preliminary fuel was injected at bottom dead center (BDC: Bottom Dead Center (110b)) and the control fuel was injected at 30 degrees before the top dead center (TDC: Top Dead Center (110a)).

As a result, the start point of the combustion of the whole mixer was slower than when the control fuel was injected at 20 degrees before the top dead center 110a.

A detailed description will be made with reference to FIGS. 3 and 4.

On the other hand, the top dead center (110a) and the bottom dead center (110b) is described as a phase formed by the crank 130 and the axis connecting the crank shaft 131 and the cylinder 110, the top dead center (110a) The bottom dead center 110b is defined as 180 degrees. That is, the crankshaft 131 is zero degrees while the piston 120 reciprocates once in the cylinder 110 to the top dead center 110a-> bottom dead center 110b-> top dead center 110a. > 180 degrees-> 0 degrees will rotate once.

In addition, the injection time of the preliminary fuel and the control fuel may vary according to fuel and cylinder specifications, and it is sufficient that the control fuel is injected before the start of combustion of the preliminary fuel to delay the combustion time of the entire mixer.

The driving unit 100 includes a cylinder 110 in which a mixer is burned, a piston 120 reciprocating between the top dead center 110a and the bottom dead center 110b of the cylinder 110 in the cylinder 110, And a crank shaft 131 connected to the piston 120 and the crank 130 to rotate.

The control unit 200 is a part corresponding to an ECU (Electronic control unit) of Charang, a thermometer measuring unit 210 and a charge amplifier 220 for measuring the temperature and the pressure inside the cylinder, respectively, the thermometer measuring unit 210 and the charge Computer 250 receives the data measured from the amplifier 220 and the injector driver 240 for controlling the fuel injection of the injector 340 in response to the command of the computer 250. In addition, it was provided with an oscilloscope 230 for displaying the pressure and temperature inside the measured cylinder 110.

In addition, the computer 250 receives phase information of the crankshaft 131 from a rotary encoder (not shown) provided in the crankshaft 131 and drives the injector driver 240 based on the phase information. Let's do it.

The fuel supply unit 300 includes a booster device 320 for adjusting the pressure of the fuel 310 and the fuel 310, a common rail 330 for storing the boosted fuel, and the boosted fuel in the cylinder 110. Injector 340 is injected to the inside.

In an embodiment of the present invention, it is assumed that dimethyl ether (DME) is used as the fuel 310, but all kinds of fuels capable of compression ignition such as gasoline, diesel, hydrogen, and general gas fuel may be used. The timing of injection of the reserve fuel and the control fuel may vary.

The cooling unit 500 includes an electric heater 520 for maintaining the temperature of the cooling water and a cooling water circulation pump 510 for circulating the cooling water.

In addition, an exhaust gas component measuring unit 400 is provided for component analysis of the exhaust gas discharged from the cylinder 110, and the exhaust gas component measuring unit 400 measures NO _x for measuring nitrogen oxides in the exhaust gas. An analyzer 420 and an infrared spectrophotometer 410 for measuring carbon monoxide and hydrocarbons.

However, the premixed compression ignition engine according to an embodiment of the present invention is configured to experimentally confirm the start time of combustion by changing the injection timing of the fuel injected from the injector 340, and when applied to the actual premixed compression ignition engine The experimental equipment such as the exhaust gas component measuring unit 400 or the oscilloscope 230 is excluded.

2 is a flowchart illustrating a method of controlling a combustion timing of premixed compression ignition combustion according to an embodiment of the present invention.

Referring to FIG. 2, a method of controlling a combustion time of a premixed compression ignition combustion engine according to an exemplary embodiment of the present invention may include a predetermined amount of the piston 120 when the piston 120 is located at the bottom dead center 110b of the cylinder 110. Spare fuel is injected (S100).

In addition, the preliminary fuel may be injected at least once, and it is sufficient to be injected before the control fuel injection.

In one embodiment of the present invention, the preliminary fuel was injected once at the bottom dead center (110b). However, the number of injections and the injection timing of the preliminary fuel may vary depending on the type of fuel or the specifications of the engine.

Next, the preliminary fuel and the air inside the cylinder 110 are mixed and the temperature is increased while being compressed by the compression stroke of the piston 120 (S120).

Next, a predetermined amount of control fuel is injected before the preliminary fuel reaches a pressure and a temperature at which combustion starts (S200).

In addition, the control fuel is injected once between 25 degrees to 35 degrees before the top dead center (110a), preferably at 30 degrees.

As a result, while the preliminary fuel and the control fuel are mixed, the internal temperature of the cylinder 110 is constantly lowered by the latent heat of evaporation of the control fuel, and then rises again (S210).

 That is, the preliminary fuel is injected at the bottom dead center 110b, which is the starting point of the compression stroke of the piston 120, so that the mixed state of the preliminary fuel and the air in the cylinder 110 is good, while the control fuel is the top dead center. (110a) by spraying at 30 degrees before the start of combustion by the latent heat of evaporation of the control fuel.

A detailed description will be given with reference to FIGS. 3 and 4.

Next, the entire fuel mixture of the preliminary fuel in the cylinder 110 and the mixed fuel is continuously compressed in the cylinder 110 (S220), and combustion is started at a constant temperature and pressure (S230).

As a result, while the emission of harmful gases such as nitrogen oxide, carbon monoxide and hydrocarbons of the cylinder 110 is reduced, there is no problem that the engine output is reduced.

Therefore, efficient premixed compression ignition combustion can be performed.

3 is a view showing the relationship between the phase of the crankshaft, the cylinder pressure, the heat generation rate according to an embodiment of the present invention, Figure 4 is a relationship between the phase, cylinder pressure, heat generation rate of the crankshaft according to an embodiment of the present invention This is an enlarged view.

Referring to the drawings, it can be seen that the dimethyl ether used as the fuel 310 in one embodiment of the present invention is combusted near 20 degrees (e) before the top dead center (110a).

However, the fuel 310 may apply any type of fuel capable of compression ignition such as gasoline, diesel, hydrogen, and general gas fuel, and the timing at which combustion starts may vary according to the type of the fuel 310.

In addition, all the preliminary fuel is injected at a certain time, and the control fuel is injected before the start of the introduction of the preliminary fuel, after the start of combustion, and after the start of combustion, to find out how the control fuel affects the start of combustion of the entire mixer. saw.

In one embodiment of the present invention, the preliminary fuel was injected at the bottom dead center (110b) and the control fuel was injected at 30, 20 and 10 degrees before the top dead center (110a), respectively.

As a result, when the start of combustion of the preliminary fuel is not proportionally proportional to the time of injecting the control fuel and the control fuel is injected at 20 degrees before the top dead center 110a (a) 110a) Combustion was started next in case of spraying at 30 degrees before, and in case of spraying at 10 degrees of top dead center (110a), combustion (c) was started most recently.

That is, the combustion was delayed compared to the case where (b) sprayed at 30 degrees before the top dead center 110a (a) when sprayed at 20 degrees before the top dead center 110a. The reason is that when spraying at 30 degrees before the top dead center (110a), the temperature (d) of the cylinder temporarily decreases and then rises again (d), which is caused by the latent heat of evaporation of the control fuel. This is because the combustion start is delayed.

Therefore, the mixture of the fuel and the air inside the cylinder 110 is better than that of the case where it is injected at 30 degrees before the top dead center 110a (b) when the gas is injected at 20 degrees (a). On the other hand, since the onset of combustion is delayed, the output is improved to allow the combustion closest to the premixed compression ignition combustion.

Figure 5 is a graph measuring the exhaust gas component and the output of the pre-mixed compression ignition combustion controlled combustion time in accordance with an embodiment of the present invention.

Referring to FIG. 5, the preliminary fuel is injected at the bottom dead center 110b to measure the output of the engine and the component of the exhaust gas of the premixed compression ignition combustion in which the combustion timing is controlled according to an embodiment. After spraying at 30 degrees, 20 degrees, 10 degrees, top dead center 110a, and 5 degrees after top dead center 110a before point 110a, the output (IMEP) and the emissions of nitrogen oxides (NO _x ) were compared.

As a result, when the control fuel was injected at 30 degrees before the top dead center (110a), there was little emission of nitrogen oxide than in the other cases, and the output was similar to that injected at 5 degrees after the top dead center (110a) and the top dead center (110a). Was measured. However, it can be seen that when the control fuel is injected at 5 degrees after the top dead center 110a and the top dead center 110a, a large amount of nitrogen oxide is generated even though the engine output increases.

Therefore, when the control fuel is injected at 30 degrees of the top dead center (110a), the emission of nitrogen oxides is reduced while output power does not occur. Therefore, the control is closest to the premixed compression ignition combustion.

In the above, the configuration and operation of the present invention is shown in accordance with the above description and drawings, but this is merely described, for example, and the injection timing of the preliminary fuel and the control fuel may be changed according to the type of fuel and the specifications of the engine. If the preliminary fuel is injected before the start of combustion, it will be apparent to those skilled in the art to belong to the technical spirit and scope of the present invention, and various changes and modifications can be made without departing from the technical spirit and scope of the present invention. Of course.

As described above, according to the present invention, the preliminary fuel and the control fuel are sprayed in two stages, respectively, so that the piston can simultaneously maximize the thermal efficiency by simultaneously burning the entire mixture of the preliminary fuel and the control fuel near the top dead center of the cylinder. It is effective to provide a mixed compression ignition engine and a combustion timing control method.

In addition, there is an effect that can provide a pre-mixed compression ignition engine and combustion timing control method that can reduce the harmful gas contained in the exhaust gas.

Claims (8)

In the combustion timing control method of premixed compression ignition combustion (HCCI) in which fuel and air are uniformly premixed in a cylinder and then combusted, A first step of spraying at least one spare fuel before the top dead center (TDC); And And a second step of injecting control fuel before the start of combustion of the preliminary fuel. The first step is performed at the bottom dead center (BDC) The second step is the combustion timing control method of the premixed compression ignition combustion, characterized in that the crankshaft phase is between 25 degrees to 35 degrees before the top dead center. The method of claim 1, After the first step, the preliminary fuel is mixed with air in the cylinder and is compressed in the cylinder; After the second step, the temperature in the cylinder is lowered to a predetermined temperature for a predetermined time by the latent heat of evaporation of the control fuel, and then the second step of rising again; A second step of mixing the preliminary fuel, the air in the cylinder, and the control fuel with the mixer mixed inside the cylinder; And Combustion timing control method of the premixed compression ignition combustion, characterized in that the mixer comprises a third step to start the combustion. The method of claim 2, In the second to third stages, the mixer starts combustion before the top dead center. delete delete delete delete In a premixed compression ignition (HCCI) engine in which fuel is injected into an cylinder by an injector, premixed with the air in the cylinder, and then compressed and combusted at a constant pressure and temperature, The injector injects the fuel at least two times, at least one injection of the preliminary fuel before the top dead center (TDC), and the injection of control fuel before the preliminary fuel is burned, The preliminary fuel is a premixed compression ignition engine, characterized in that the phase of the crankshaft is injected at the bottom dead center (BDC: Bottom Dead Line), the control fuel is injected between 25 degrees to 35 degrees before the top dead center of the crankshaft. .

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