JP2006037075A - Fuel oil composition for premixed compression self-ignition engine - Google Patents

Abstract

To provide a fuel oil composition for a premixed compression self-ignition engine capable of reducing PM, THC, etc. contained in exhaust gas of the premixed compression self-ignition engine.
SOLUTION: It contains 2% by volume or more of an oxygen-containing compound having an intramolecular oxygen ratio of 60% by mass or less and a boiling point of 50 ° C. or more, and has a predetermined distillation property, and has a density, total aromatic content, and two or more rings. A fuel oil composition for a premixed compression self-ignition engine in which the content of the group, the content of sulfur, and the content of nitrogen are in a specific range.
[Selection figure] None

Description

  The present invention relates to a fuel oil composition for a premixed compression self-ignition engine.

  In a diesel engine, the piston in the compression process rises to highly compress the air in the combustion chamber to raise the temperature, and when the temperature reaches the critical temperature of light oil or higher, the fuel is sprayed and self-ignited combustion is taken. ing. For this reason, diesel engines have good combustion efficiency, are mounted on automobiles, ships, construction machines, generators, etc., and are widely used in society. However, exhaust gases from diesel engines are rich in environmental pollutants such as nitrogen oxides (NOx), particulate matter (Particulate Matter: PM), and total hydrocarbons (Total Hydro Carbon: THC).

Therefore, various measures have been taken for the purpose of reducing environmental pollutants, such as improvement of the engine body, oxidation catalyst and DPF (Diesel Particulate Filter). As one of them, a premixed compression self-ignition combustion system has been proposed (for example, Non-Patent Document 1 and Patent Document 1).

  A premixed compression self-ignition engine that uses this method is that most of the fuel is injected into the cylinder from the beginning of the intake stroke to the end of the compression stroke, and the injected fuel is vaporized and mixed in the compression stroke. It is an engine that ignites and burns by spontaneous ignition at the end of the stroke. In a premixed compression self-ignition engine, the combustion temperature does not become high because the fuel and air are burned in a uniformly and leanly mixed state. Therefore, generation of NOx and PM can be significantly suppressed. The premixed compression self-ignition engine is highly efficient because it has a high combustion speed and is close to the ideal cycle and can be operated at a high compression ratio. It is close to a spark ignition engine (gasoline engine) in that a premixed gas is used as fuel, and close to a compression ignition engine (diesel engine) in that combustion is started by spontaneous ignition. Therefore, it can be said that it is a new combustion engine located between the two.

  So far, various studies have been conducted for the purpose of obtaining fuel oil suitable for premixed compression self-ignition combustion. For example, an example using a plurality of fuel oils having different cetane numbers (for example, Patent Document 2) and an example using a volatile fuel with improved ignitability have been proposed (for example, Patent Document 3).

Automotive Engineering Society Academic Lecture Preprint 981 (1998) 49-52 JP-A-9-158810 JP 2001-355471 A JP 2004-91657 A

  However, the fuel oil described in Patent Document 2 is not clear about the specific effective oil type, and if a plurality of different fuel oils are required, the filling and supply of the fuel oil becomes complicated, and Since the structure of the engine is complicated, it is economically inconvenient. Further, the fuel oil described in Patent Document 3 has a very high volatility and is close to so-called gasoline, and has a problem that fuel consumption is not good.

  In view of such circumstances, an object of the present invention is to provide a fuel oil composition for a premixed compression self-ignition engine that can reduce PM and THC contained in exhaust gas from the engine.

  In order to solve the above problems, a fuel oil composition for a premixed compression self-ignition engine according to the present invention contains 2% by volume or more of an oxygen-containing compound having an intramolecular oxygen ratio of 60% by mass or less and a boiling point of 50 ° C. or more. It is characterized by including.

  According to the fuel oil composition for a premixed compression self-ignition engine of the present invention, the fuel oil composition contains 2% by volume or more of a predetermined oxygen-containing compound. It has moderate premixing and self-ignitability, and is easy to burn completely, reducing environmental pollutants such as PM and THC (total hydrocarbons) in the exhaust gas.

  The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an oxygen content of 1% by mass or more. When the oxygen content in the fuel oil composition is 1% by mass or more, combustion in the engine becomes more efficient, and generation of PM and THC in the exhaust gas can be effectively reduced.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention preferably has the following (1) and (2) formulas and has the following (3) to (7).

(3) Density: 0.801 g / cm ³ or more (4) Total aromatic content: 5 vol% or more (5) Bicyclic or higher aromatic content: 5 vol% or less (6) Sulfur content: 10 mass ppm or less ( 7) Nitrogen content: 10 mass ppm or less

  According to the premixed compression self-ignition engine fuel oil composition of the present invention, in addition to containing the oxygen-containing compound, the fuel oil composition has the distillation properties represented by the formulas (1) and (2), Since it has the characteristics shown in (3) to (7), it has suitable volatility and ignitability, and enables more efficient combustion of the fuel oil composition in the engine. Therefore, environmental pollutants such as PM and THC (total hydrocarbons) can be reduced.

  In the premixed compression self-ignition engine fuel oil composition of the present invention, the residual carbon content of 10% residual oil is preferably 0.1% by mass or less. When the residual carbon content of 10% residual oil is 0.1% by mass or less, the fuel injection pump constituting the engine can be maintained for a long time in a high-performance state.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
In the present invention, the premixed compression self-ignition engine is a type of engine that is also called an HCCI engine (Homogeneous Charge Compression Ignition Engine). A premixed compression self-ignition engine injects fuel into the engine compartment at the beginning of the intake stroke, vaporizes and mixes the injected fuel in the compression stroke, and ignites and burns by spontaneous ignition at the end of the compression stroke. In the engine compartment, the combustion temperature does not become high because the fuel and air are burned in a uniformly and leanly mixed state. Therefore, compared with the conventional diesel engine, generation | occurrence | production of NOx and PM can be suppressed. Moreover, since it can be operated at a high compression ratio, it is highly efficient. It is close to a spark ignition engine (gasoline engine) in that a premixed gas is used as fuel, and close to a compression ignition engine (diesel engine) in that combustion is started by spontaneous ignition. The fuel oil composition of the present invention can also be applied to a premixed compression self-ignition engine and a hybrid engine using a spark ignition gasoline engine, an electric motor, or the like.

  The premixed compression self-ignition engine fuel oil composition of the present invention is characterized in that it contains 2% by volume or more of an oxygen-containing compound having an intramolecular oxygen ratio of 60% by mass or less and a boiling point of 50 ° C. or more.

  The intramolecular oxygen ratio of the oxygen-containing compound contained in the fuel oil composition needs to be 60% by mass or less. When the intramolecular oxygen ratio exceeds 60% by mass, the amount of NOx produced increases when the fuel oil composition burns in the engine. The intramolecular oxygen ratio of the oxygen-containing compound is preferably 50% by mass or less, and more preferably 30% by mass or less.

  The boiling point of the oxygen-containing compound needs to be 50 ° C. or higher. If the boiling point of the oxygen-containing compound is less than 50 ° C., the premixed gas formation is adversely affected. The oxygen-containing compound preferably has a boiling point of 70 ° C. or higher.

  The oxygen-containing compound needs to be contained in an amount of 2% by volume or more in the premixed compression self-ignition engine fuel oil composition. If the content of the oxygen-containing compound in the fuel oil composition is less than 2% by volume, the effect of reducing PM and THC in the exhaust gas may not be sufficiently exhibited. When the content of the oxygen-containing compound in the fuel oil composition is 2% by volume or more, not only the effect of reducing PM and THC but also the fuel efficiency is improved. The content of the oxygen-containing compound is preferably 20% by volume or more, more preferably 50% by volume or more, and still more preferably 70% by volume or more with respect to the fuel oil composition.

  Here, the oxygen-containing compound used in the present invention is, for example, methyl tertiary butyl ether (MTBE), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (ETBE), tertiary amyl ethyl ether (TAEE), Ethers such as diisopropyl ether (DIPE) and diethylene glycol dimethyl ether (DGM), esters such as methyl caprolate and methyl decanoate, carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC), or methanol, Alcohols such as ethanol, isopropyl alcohol, isobutyl alcohol, tertiary butyl alcohol (TBA), pentyl alcohol, hexyl alcohol, 2-ethyl-1-hexanol Le acids, refers to oxygen-containing compounds such as fatty acid methyl esters. These can be used alone or in combination.

  As described above, the premixed compression self-ignition engine fuel oil composition of the present invention only needs to contain 2% by volume or more of a predetermined oxygenated compound, and therefore consists of 100% oxygenated compound. There may be.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention contains 2% by volume or more of a specific oxygen-containing compound. PM and THC can be effectively reduced, and fuel efficiency is excellent.

  The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an oxygen content of 1% by mass or more. When the oxygen content is 1% by mass or more, the fuel oil composition is easily combusted in the engine, and the production of PM and THC can be effectively reduced. The oxygen content in the fuel oil composition is more preferably 5% by mass or more, and further preferably 10% by mass or more. Here, the oxygen content can be measured in accordance with, for example, JIS K 2536-6 “Petroleum product-component test method Part 6: Determination of oxygen content and oxygen compound by oxygen detection type gas chromatograph”. .

  The premixed compression self-ignition engine fuel oil composition of the present invention preferably has the distillation properties of the following formulas (1) and (2) and includes the following (3) to (7).

  These represent distillation properties, and from the viewpoint of reducing THC (total hydrocarbons) in the exhaust gas, the value of the formula (1) is preferably 2000 ° C. or less. More preferably, it is 1900 degrees C or less, More preferably, it is 1800 degrees C or less.

Among these distillation temperatures, T ₉₀ is particularly important in terms of the influence on the combustibility of the fuel oil composition. T ₉₀ is preferably 400 ° C. or lower. When T ₉₀ exceeds 400 ° C., there is a possibility that PM and soot in the exhaust gas increases. Considering the effect of reducing PM and soot in the exhaust gas, T ₉₀ is more preferably 270 to 360 ° C., and further preferably 270 to 350 ° C.

Further, ΔE _{270 represented} by the formula (2) is preferably 20% by volume or more from the viewpoint of reducing THC (total hydrocarbons) in the exhaust gas. More preferably, it is 40 volume% or more. Note that T _50, T ₇₀ , T ₉₀ in equation (1) and ΔE ₂₇₀ in equation (2) are, for example, J
It can be measured according to IS K 2254 "Petroleum products-Distillation test method".

(3) Density:
The fuel oil composition for a premixed compression self-ignition engine of the present invention preferably has a density of 0.801 g / cm ³ or more from the viewpoint of improving fuel efficiency. More preferably, it is 0.820 g / cm < ³ > or more, More preferably, it is 0.830 g / cm < ³ > or more. This density is, for example, JIS
K 2249 “Crude oil and petroleum products—density test method and density / mass / capacity conversion table” can be measured.

(4) Total aromatic content:
The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a total aromatic content of 5% by volume or more. When the total aromatic content is 5% by volume or more, the premixed gas can be sufficiently formed by controlling the ignitability in the engine. The total aromatic content is more preferably 10% by volume or more, and further preferably 15% by volume or more.
The total aromatic content can be measured, for example, in accordance with JIS K 2536 “Petroleum product-component test method”.

(5) Aromatic content of 2 or more rings:
The fuel oil composition for a premixed compression self-ignition engine of the present invention preferably has an aromatic content of 2 or more rings of 5% by volume or less as its composition. When the aromatic content of two or more rings is 5% by volume or less, PM in the exhaust gas can be more effectively reduced. More preferably, it is 3 volume% or less. The aromatic content of two or more rings can be measured, for example, in accordance with JIS K 2536 “Petroleum products-component test method”.

(6) Sulfur content:
The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a sulfur content of 10 mass ppm or less. If the sulfur content exceeds 10 mass ppm, the sulfate content in the PM contained in the exhaust gas may increase. Sulfate is present in PM in a state containing sulfate and about 1.3 times as much bound water, but the amount depends on the sulfur content in the fuel oil composition. The sulfur content is more preferably 5 ppm by mass or less. The sulfur content can be measured, for example, according to JIS K2541 “Crude oil and petroleum products—Sulfur content test method”.

(7) Nitrogen content:
The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a nitrogen content of 10 mass ppm or less. If the nitrogen content exceeds 10 mass ppm, so-called fuel NOx may increase. Fuel NOx is NOx derived from the fuel oil composition. The nitrogen content is more preferably 5 ppm by mass or less. The nitrogen content can be measured, for example, according to JIS K 2609 “Crude oil and petroleum products—nitrogen content test method”.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention uses the above-described oxygen-containing compound or a base material containing these oxygen-containing compounds and the following light oil base material, and the distillation properties and density described above. It can prepare by mix | blending suitably so that conditions, such as, may be satisfy | filled. Examples of such light oil base materials include straight-run gas oil obtained by atmospheric distillation of crude oil, vacuum gas oil obtained by vacuum distillation of straight-run heavy oil and residual oil obtained by atmospheric distillation, and hydrogenation of vacuum gas oil. Hydrocracked diesel oil obtained by refining, hydrodesulfurized diesel oil obtained by hydrodesulfurizing straight run diesel oil, dewaxed desulfurized diesel oil obtained by further dewaxing hydrodesulfurized diesel oil, reduced pressure diesel oil and desulfurized diesel oil by catalytic cracking The cracked gas oil obtained by hydrocracking the straight-run kerosene obtained by hydrocracking the straight-run kerosene obtained by hydrocracking the crude oil obtained by catalytic distillation And cracked kerosene obtained by synthesis, synthetic oil obtained by polymerization of olefin, and the like.

  In the fuel oil composition of the present invention, various additives can be appropriately blended as necessary within a range that does not impair the object and effect of the present invention. Examples of the lubricity improver include carboxylic acid type, ester type, and alcohol type. Examples of the cetane number improver include a nitrate ester type and an organic peroxide type. Examples of engine detergents include imide compounds, alkenyl succinic acid derivatives, succinic acid esters, and copolymer polymers. Examples of the fluidity improver include ethylene-vinyl acetate copolymer and alkenyl succinic acid amide. Examples of the antioxidant include a phenol type and an amine type. One or more of these may be added to the fuel oil composition of the present invention. Further, the addition amount of these additives may be appropriately selected as necessary, but usually, the total amount of the additives is preferably 0.5% by mass or less with respect to the fuel oil composition. Among these additives, the oxygen-containing compounds include those that act as oxygen-containing compounds in the present invention.

  According to the premixed compression self-ignition engine fuel oil composition of the present invention, in addition to containing the oxygen-containing compound described above, the fuel oil composition has the distillation properties represented by the formulas (1) and (2), and , Density, total aromatic content, aromatic content of 2 or more rings, sulfur content, nitrogen content, satisfying the above conditions, it becomes possible to efficiently burn in the engine, PM in the exhaust gas, There is an effect that sulfate and THC can be reduced. The action mechanism is estimated as follows.

  Since the premixed compression self-ignition engine fuel oil composition of the present invention has a distillation property, total aromatic content, and aromatic content of two or more rings within a predetermined range, the ignition timing is neither too early nor too late, It has moderate self-ignitability. In other words, the ignition timing of the fuel oil composition injected from the engine nozzle is automatically controlled near the top dead center. Therefore, the thermal efficiency is inevitably high.

  In addition, since the ignition timing is not too early, the mixing time of the fuel oil composition and air is sufficient, and the concentration distribution in the engine of the fuel oil composition becomes uniform. Furthermore, it is considered that the combustion itself approaches the complete combustion due to the presence of the oxygen-containing compound, and as a result, good premixed compression self-ignition combustion is achieved, and the generation of PM and THC can be suppressed. Moreover, since the sulfur content in a fuel oil composition is below a predetermined amount, the sulfate in PM can also be reduced.

  The fuel oil composition of the present invention is effective when used in a premixed compression self-ignition engine having a multistage injection mechanism. There are various forms of an engine having a multi-stage injection mechanism. For example, an engine equipped with a pilot injection mechanism is more effective. Here, the pilot injection means that a small amount of fuel is injected before the main injection in the compression process.

  It is also effective to use the fuel oil composition of the present invention in a common rail injection system. Here, the common rail injection system is a system that can control necessary injection pressure, injection amount, and the like at necessary timing by electronic control.

  In the premixed compression self-ignition engine fuel oil composition of the present invention, the residual carbon content of 10% residual oil is preferably 0.1% by mass or less. The residual carbon content of 10% residual oil is the residual carbon content of the fuel oil composition that has been adjusted to a 10% distillate residual oil. When this value exceeds 0.1% by mass, carbon is likely to be generated in the combustion chamber, and the possibility of causing a decrease in performance of the fuel injection pump increases. The residual carbon content of 10% residual oil can be measured in accordance with, for example, JIS K 2270 “Crude oil and petroleum products—residual carbon content test method”.

  The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an abrasion mark of 500 μm or less in a HFRR (High Frequency Reciprocating Rig) test. The wear mark of the HFRR test is a measure of the lubricity of the fuel oil composition, and if this value exceeds 500 μm, there is a high possibility that the performance of the fuel injection pump will deteriorate. Preferably it is 460 micrometers or less, More preferably, it is 420 micrometers or less. The wear scar in the HFRR test can be measured in accordance with, for example, the Petroleum Institute Standard JPI-5S-50-98 “Light Oil-Lubricating Oil Test Method”.

  The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an induction period (IP) of 960 minutes or longer. I. P. Is a measure of the oxidation resistance stability of the fuel oil composition. When this value is less than 960 minutes, the fuel oil composition is oxidized and deteriorated to produce a gum component, which tends to deteriorate the performance of the fuel injection pump. . Preferably it is 1440 minutes or more. The induction period (IP) of the composition can be measured according to, for example, JIS K 2287 “Gasoline-Oxidation Stability Test Method—Induction Period Method”.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not restrict | limited at all to description content, such as these Examples.

[Examples 1 and 2 and Comparative Example 1]
Table 1 shows the properties of the fuel oil composition of the present invention and the comparative fuel oil composition. Moreover, the preparation method of the fuel oil composition in each Example is as follows.
Example 1: Using the fuel oil composition of Comparative Example 1 as a base substrate, an oxygen-containing compound (DMC: dimethyl carbonate) was prepared to be 10% by mass.
DMC has an oxygen content of 53.3% by mass and a boiling point of 90.9 ° C.
Example 2 Using the fuel oil composition of Comparative Example 1 as a base substrate, an oxygen-containing compound (DGM: diethylene glycol dimethyl ether) was prepared to be 40% by mass.
The oxygen content of DGM is 35.8% by mass and the boiling point is 163 ° C.

(Properties of fuel oil composition)

(Method for measuring properties of fuel oil composition)
(1) Oxygen content Measured in accordance with JIS K 2536-6 “Petroleum products—component test method Part 6: Determination of oxygen content and oxygen compound by oxygen detection type gas chromatograph”.
(2) Distillation property Measured according to JIS K 2254 "Petroleum products-Distillation test method".
(3) Density The density was measured according to JIS K 2249 “Crude oil and petroleum products—Density test method”.
(4) Total aromatic content Measured according to JIS K 2536 “Petroleum products—component test method”.
(5) Aromatic content of two or more rings Same as above (6) Sulfur content Measured according to JIS K 2541 “Crude oil and petroleum products—Sulfur content test method”.
(7) Nitrogen content Measured according to JIS K 2609 “Crude oil and petroleum products—Test method for nitrogen content”.
(8) Residual carbon content of 10% residual oil Measured according to JIS K 2270 “Crude oil and petroleum products—residual carbon content test method”.

[Test Example 1]
Using the premixed compression self-ignition engine having the specifications shown below, the fuel oil compositions of Examples 1 and 2 and Comparative Example 1 obtained as described above were operated under the following operating conditions. The NOx concentration at the engine outlet, the amount of PM generated, the amount of SOF in PM, the amount of sulfate in PM, and the amount of THC (total hydrocarbons) were measured and compared and evaluated.

(Engine specifications)
Cylinder diameter x piston process: 105mm x 115mm
Stroke volume: 1000cm ³
Valve mechanism: 2 intake valves, 2 exhaust valves Combustion chamber: Flat dish compression ratio: 18.0
Fuel injection pressure: 40 MPa

(Engine operating conditions)
Fuel injection timing: 40 deg before top dead center
Engine speed: 2000rpm
Engine load: 50%
EGR: 20%

(Exhaust gas test method)
(1) NOx (nitrogen oxide)
Extract a part of the exhaust gas from the gas sample outlet installed in the exhaust pipe of the engine,
Measurement was performed using an automobile exhaust gas analyzer (MEXA-9100DGR: manufactured by Horiba, Ltd.).

(2) PM (particulate matter)
Part of the exhaust gas was introduced into the micro tunnel (manufactured by Horiba, Ltd.) from the gas sample outlet installed in the exhaust pipe of the engine, diluted, sampled with a collection filter, and then weighed ( New car screening standards collection: Kobunsha, 438 pages). In addition, PM collection was carried out for 30 minutes with engine conditions being steady.

(3) SOF (solvent soluble matter in PM)
The filter that collected PM was subjected to Soxhlet extraction (dichloromethane solvent), and the weight reduced by extraction was defined as the amount of SOF.

(4) Sulfate (sulfur oxide in PM)
The PM remaining on the filter after SOF extraction was measured by ion chromatography using the sample.

(5) THC (total hydrocarbons)
A part of the exhaust gas was extracted from a gas sample outlet installed in the exhaust pipe of the engine and measured using a smoke meter (MEXA-130S: manufactured by Horiba, Ltd.).

(Result)

  As can be seen from the results shown in Table 2, the premixed compression self-ignition engine fuel oil composition of the present invention obtained in Examples 1 and 2 has an oxygen content as compared with the fuel oil composition of Comparative Example 1. Although NO is high, NOx in the exhaust gas does not increase so much, and THC, PM, and SOF in PM are remarkably reduced.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention can reduce THC and PM contained in exhaust gas when used in a premixed compression self-ignition engine.

Claims (4)

  A fuel oil composition for a premixed compression self-ignition engine, comprising 2% by volume or more of an oxygen-containing compound having an intramolecular oxygen ratio of 60% by mass or less and a boiling point of 50 ° C. or more. In the fuel oil composition for premixed compression self-ignition engines according to claim 1,
A fuel oil composition for a premixed compression self-ignition engine characterized by having an oxygen content of 1% by mass or more. In the fuel oil composition for premixed compression self-ignition engines according to claim 1 or 2,
A fuel oil composition for a premixed compression self-ignition engine having the distillation properties represented by the following formulas (1) and (2) and comprising the following (3) to (7).

(3) Density: 0.801 g / cm ³ or more (4) Total aromatic content: 5 vol% or more (5) Bicyclic or higher aromatic content: 5 vol% or less (6) Sulfur content: 10 mass ppm or less ( 7) Nitrogen content: 10 mass ppm or less The premixed compression self-ignition engine fuel oil composition according to claim 3,
A fuel oil composition for a premixed compression self-ignition engine, wherein the residual carbon content of 10% residual oil is 0.1% by mass or less.