JP2005343919A - Fuel oil composition for premixed compressed self-ignition type engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel oil composition for premixed compressed self-ignition type engine capable of reducing NOx, PM, etc., contained in a discharge gas and improving fuel cost. <P>SOLUTION: The fuel oil composition for premixed compressed self-ignition type engine has distillation properties represented by formula (1): T<SB>50</SB>+ T<SB>70</SB>×2 + T<SB>90</SB>×3×≤2,200°C (wherein T<SB>50</SB>is 50 vol% distillation temperature; T<SB>70</SB>is 70 vol% distillation temperature; T<SB>90</SB>is 90 vol% distillation temperature) and formula (2): ΔE<SB>270</SB>≥10 vol% (wherein ΔE<SB>270</SB>is distillation amount obtained when heated to 270°C) and cetane number, density, whole aromatic content, sulfur content and nitrogen content are each within a specific range. Reduction of NOx, etc., in the discharge gas can efficiently be carried out and improvement of fuel cost can be performed by using fuel oil composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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.

In addition, exhaust gas from diesel engines contains many environmental pollutants such as nitrogen oxides (NO _X ), particulate matter (Particulate Matter: PM), and unburned hydrocarbons (Thermal Hydro Carbon: THC). For this reason, various measures have been taken with the aim of reducing environmental pollutants, such as improvement of the engine body, oxidation catalyst, particulate matter collection device (Diesel Particulate Filter: DPF), and the like. 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 using this method is a method in which fuel is injected into the cylinder from the beginning of the intake stroke to the middle of the compression stroke, and the injected fuel is vaporized and mixed in the compression stroke. The engine is ignited and burned by spontaneous ignition at the end. Therefore, the premixed compression self-ignition engine has a feature that the combustion temperature does not become high because the fuel and air are burned in a state where the fuel and air are mixed evenly and leanly. Therefore, generation of NO _X and PM occurs. Can be greatly 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. This engine 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.

  On the other hand, in recent years, various studies have been conducted for the purpose of obtaining a fuel oil suitable for premixed compression self-ignition combustion. For example, examples using a plurality of fuel oils having different cetane numbers (for example, patents) Document 2), an example using a volatile fuel with improved ignitability has been proposed (for example, Patent Document 3).

Japan Society for Automotive Engineers Academic Lecture Preprints 981 (1998), pp. 49-52 JP-A-9-158810 JP 2001-355471 A JP 2004-91657 A

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

  In consideration of such circumstances, the present invention provides a fuel oil composition for a premixed compression self-ignition engine that is excellent in fuel efficiency while reducing NOx and PM contained in exhaust gas from the engine. For the purpose.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention has distillation properties represented by the following formulas (1) and (2), and comprises the following (3) to (7): It is characterized by.

(3) Cetane index: 60 or less (4) Density: 0.801 g / cm ³ or more (5) Total aromatic content: 15 vol% or more (6) Sulfur content: 10000 mass ppm or less (7) Nitrogen content Content: 500 mass ppm or less

According to the premixed compression self-ignition engine fuel oil composition of the present invention, it has the distillation properties represented by the formulas (1) and (2), and is also characterized by the following (3) to (7) Therefore, it has moderate volatility and ignitability, enables efficient combustion of the fuel oil composition in the engine, and can reduce environmental pollutants such as NO _x , PM, and THC (unburned hydrocarbon). . Moreover, since the density is high, the fuel oil composition is excellent in fuel efficiency.

The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a trace impurity content of 50 mg / L or less.
According to the present invention, since the content of trace impurities in the composition is in a specific range, the state of the fuel injection pump constituting the engine can be kept good.
Here, examples of the trace impurities expected to be mixed in the fuel oil composition include, for example, so-called dry sludge.

The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a wear scar of 500 μm or less in an HFRR (High Frequency Reciprocating Rig) test.
If the HFRR of the fuel oil composition is 500 μm or less as in the present invention, the fuel injection pump constituting the engine can be maintained for a long time in a high performance state.

The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an induction period (IP) of 960 minutes or longer.
As in the present invention, when the induction period (IP), which is a measure indicating the oxidation resistance stability of the fuel oil composition, is 960 minutes or more, the oxidation resistance stability of the fuel oil composition becomes good. The fuel injection pump 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.
The premixed compression self-ignition engine to which the fuel oil composition for the premixed compression self-ignition engine of the present invention is applied is a type of engine called a so-called HCCI engine (Homogeneous Charge Compression Ignition Engine). is there. Such 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. Therefore, in the engine chamber, fuel and air are burned in a uniformly and leanly mixed state, and the combustion temperature is not high.

  Since the premixed compression self-ignition engine does not have a high combustion temperature in this way, generation of NOx and PM can be suppressed as compared with a conventional diesel engine. In addition, it is highly efficient because it 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.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention is not limited to such a premixed compression self-ignition engine, but also a hybrid engine using a spark ignition gasoline engine or an electric motor together. Can also be applied.

  Here, the fuel oil composition for a premixed compression self-ignition engine of the present invention has properties represented by the following formulas (1) and (2).

  Among the distillation properties of the formulas (1) and (2), when the value represented by the formula (1) exceeds 2200 ° C., THC (unburned hydrocarbon) in the exhaust gas increases, which is not preferable. The distillation property represented by the formula (1) is 2020 ° C. or lower, more preferably 1900 ° C. or lower.

Among these distillation temperatures, T ₉₀ is particularly important, and T ₉₀ is preferably 400 ° C. or lower. When T ₉₀ exceeds 400 ° C., PM and soot in the exhaust gas in some cases increased. Considering the fuel efficiency improvement effect on the engine and the effect of reducing PM and soot in the exhaust gas, T ₉₀ is particularly preferably 270 to 360 ° C.

Further, if ΔE ₂₇₀ represented by the formula (2) is less than 10% by volume, THC in the exhaust gas may increase, which is not preferable. ΔE ₂₇₀ is preferably 20% by volume or more.
_{Incidentally, T 50, T 70, T} 90 in the formula (1) Delta] E ₂₇₀ and in the formula (2), may, for example, JIS K2254 - can be measured according to "Petroleum products distillation test method".

(3) Cetane index:
The premixed compression self-ignition engine fuel oil composition of the present invention has a cetane index of 60 or less. When cetane index of a fuel oil composition exceeds 60, it will adversely affect the premixed gas formed, NO _X emissions increases. The cetane index in the fuel oil composition is preferably 50 or less.
The cetane index of the composition can be measured in accordance with, for example, JIS K2280 “Testing method for octane number and cetane number”.

(4) Density:
The fuel oil composition for a premixed compression self-ignition engine of the present invention has a density of 0.801 g / cm ³ or more from the viewpoint of improving fuel efficiency. If the density of the composition is less than 0.801 g / cm ³ , the fuel efficiency will deteriorate. The density of the composition is preferably 0.820 g / cm ³ or more, and more preferably 0.850 g / cm ³ or more.
The density of the composition can be measured in accordance with, for example, JIS K2249 “Crude oil and petroleum products—density test method and density / mass / volume conversion table”.

(5) Total aromatic content:
The premixed compression self-ignition engine fuel oil composition of the present invention has a total aromatic content of 15% by volume or more. If the total aromatic content is less than 15% by volume, the cetane index described above is lowered, which adversely affects the formation of the premixed gas. The total aromatic content of the composition is preferably 30% by volume or more, particularly preferably 50% by volume or more.
The total aromatic content in the composition can be measured, for example, according to JIS K2536 “Petroleum product-component test method”.

(6) Sulfur content:
The premixed compression self-ignition engine fuel oil composition of the present invention has a sulfur content of 10,000 mass ppm or less. If the sulfur content in the composition exceeds 10,000 ppm by mass, the sulfate content in the PM contained in the exhaust gas increases. Here, such 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 content of sulfur in the composition is preferably 5000 ppm by mass or less.
In addition, the sulfur content in a composition can be measured based on JISK2541 "Crude oil and petroleum products-sulfur content test method", for example.

(7) Nitrogen content:
The premixed compression self-ignition engine fuel oil composition of the present invention has a nitrogen content of 500 mass ppm or less. The nitrogen content in the composition is more than 500 mass ppm, so Hyueru NO _X is increase. Here is that of NOx from fuel oil composition as Hyueru NO _X, and thus this is NO _X increases contained in the exhaust gas by increasing. The nitrogen content in the composition is preferably 200 mass ppm or less, particularly preferably 100 mass ppm or less.
The nitrogen content in the composition can be measured by a conventionally known chemiluminescence method.

  The fuel oil composition for a premixed compression self-ignition engine of the present invention comprises a known light oil base material, a distillation property represented by the above formula (1) or formula (2), and (3) to (7). It can be prepared by blending appropriately using any means so as to have characteristics.

  Here, as usable light oil base materials, for example, straight-run gas oil obtained by atmospheric distillation of crude oil, vacuum gas oil obtained by vacuum distillation of straight-run heavy oil or residual oil obtained by atmospheric distillation, vacuum gas oil Hydrorefined diesel oil obtained by hydrorefining, hydrodesulfurized diesel oil obtained by hydrodesulfurizing straight-run diesel oil under severe conditions, dewaxed desulfurized diesel oil obtained by dewaxing hydrodesulfurized diesel oil, reduced pressure Catalytic cracked light oil obtained by catalytic cracking of light oil or desulfurized heavy oil, straight-run kerosene obtained by atmospheric distillation of crude oil, hydrogenated kerosene obtained by hydrorefining straight-run kerosene, obtained by atmospheric distillation of crude oil Cracked kerosene obtained by cracking the gas oil fraction obtained, synthetic oil obtained by polymerization of olefins, etc., may be used alone, or these may be used in combination of two or more be able to

In the premixed compression self-ignition engine fuel oil composition of the present invention, various additives can be appropriately blended as necessary within a range that does not hinder the object and effect of the present invention. Examples of such additives include lubricity improvers such as carboxylic acids, esters, and alcohols, cetane index improvers such as nitrate esters and organic peroxides, imide compounds, and alkenyl succinates. Examples include detergents such as acid derivatives, succinic acid esters and copolymer polymers, fluidity improvers such as ethylene-vinyl acetate copolymers and alkenyl succinic acid amides, and antioxidants such as phenols and amines. . Moreover, these additives can be added individually by 1 type or in combination of 2 or more types.
The additive amount of these additives may be appropriately selected as necessary in consideration of the type of the light oil base material, etc., but the fuel oil composition of the present invention is usually used as the total amount of additives. It is preferable to set it as 0.5 mass% or less with respect to the whole.

The fuel oil composition for a premixed compression self-ignition engine of the present invention obtained in this way has the distillation properties represented by the above formulas (1) and (2), and (3) to (7). by providing the characteristic enables efficient combustion in the premixed compression ignition in the engine, NO X in the exhaust _gas, PM, not only can reduce the sulfate and THC in PM, the effect that is excellent in fuel efficiency Can be suitably achieved.

Here, the action mechanism of the present invention having the effects described above is estimated as follows.
That is, the premixed compression self-ignition engine fuel oil composition of the present invention has a distillation property, a cetane index, and a total aromatic content within a predetermined range, so that the ignition timing is neither too early nor too late. Has self-ignitability. Therefore, since the ignition timing of the fuel oil composition injected from the engine nozzle is automatically controlled near the top dead center, the heat efficiency is inevitably increased.

In addition, since the ignition timing is not too early in this way, the mixing time of the fuel oil composition and air is sufficient, and the distribution of the fuel oil composition in the engine becomes uniform, resulting in good premixing. It is considered that compression self-ignition combustion can be achieved and generation of NO _x , PM and THC can be suppressed. Moreover, the sulfur content of the fuel oil composition, since the nitrogen content is not more than the predetermined amount, and sulfate in PM, can be reduced _(NO X due to the _fuel) called Hyueru NO X. Moreover, since the density is sufficiently high, the fuel consumption is also excellent.

  The fuel oil composition for a premixed compression self-ignition engine 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. The pilot injection is a mechanism that injects a small amount of fuel before the main injection in the compression process.

The premixed compression self-ignition engine fuel oil composition of the present invention is also effective when used in a so-called common rail injection system. 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. There is a high degree of freedom with respect to the injection control such as pilot injection, by combining these, it is possible to more effectively reduce NO _X in the exhaust gas.

The premixed compression self-ignition engine fuel oil composition of the present invention preferably has a trace impurity content of 50 mg / L or less. When the content of trace impurities (for example, so-called dry sludge) in the composition exceeds 50 mg / L, unnecessary substances accumulate in the combustion chamber, and the possibility of causing a decrease in performance of the fuel injection pump increases.
In addition, what is necessary is just to measure the trace impurities in a composition based on JISK2276 "Petroleum product-aviation fuel oil test method", for example.

The premixed compression self-ignition engine fuel oil composition of the present invention preferably has an HFRR (a wear scar in the HFRR test) of 500 μm or less. Here, the wear scar by the HFRR test is a measure of the lubricity of the fuel oil composition, and if this value exceeds 500 μm, the performance of the fuel injection pump may be degraded. The HFRR of the composition is preferably 460 μm or less, particularly preferably 420 μm or less.
In addition, the abrasion scar of the HFRR test of a composition can be measured based on, for example, 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. Here, this I.D. P. Is a measure of the oxidation resistance stability of the fuel oil composition, and if this value is less than 960 minutes, the fuel oil composition is oxidized and deteriorated, and a gum is generated. There is a case. The induction period (IP) of the composition is preferably 1440 minutes or longer.
The induction period (IP) of the composition can be determined according to, for example, JIS K2287 “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 to 3 and Comparative Examples 1 and 2]
The fuel oil composition for the premixed compression self-ignition engine of Examples 1 to 3 of the present invention of Examples 1 to 3 and a comparison for comparison are prepared by combining light oil base materials so as to have the distillation properties shown in Table 1. The fuel oil compositions of Examples 1 and 2 were prepared.
The properties of the fuel oil composition in Table 1 were measured as follows.

(Properties of fuel oil composition)

(Method for measuring properties of fuel oil composition)
Distillation property: Measured according to JIS K2254 "Petroleum products-Distillation test method".
Cetane index: Measured according to JIS K2280 “Testing method for octane number and cetane number”.
Density: Measured according to JIS K2249 “Crude oil and petroleum products—Density test method”.
Aromatic content: Measured in accordance with JIS K2536 “Petroleum products-component test method”.
Sulfur content: Conforms to JIS K2541 "Crude oil and petroleum products-Sulfur content test method"
Measured.
Nitrogen content: Measured by chemiluminescence method.
Trace impurities: In accordance with JIS K 2276 “Petroleum products – Test method for aviation fuel oil”
It was measured.
HFRR: Petroleum Society Standard JPI-5S-50-98 "Diesel Oil-Lubricity Test Method"
Measured in conformity.
Induction period (IP): Measured according to JIS K2287 “Gasoline-Oxidation stability test method—Induction period method”.

[Test Example 1]
Using the premixed compression self-ignition engine having the specifications shown below, the fuel oil compositions for the premixed compression self-ignition engine of Examples 1 to 3 and Comparative Examples 1 and 2 obtained as described above were used. When the engine is operated under the following operating conditions, the NO _X 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 (unburned hydrocarbon) are as follows: Measured, compared and evaluated using the exhaust gas test method. The results are shown in Table 2. In addition, the operating state of the engine during the test was also 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 ( (Refer to page 438 of New Automobile Examination Standards Collection (issued by Kobunsha)).
In addition, PM collection was performed by implementing operation for 30 minutes in the state which made the engine conditions steady.

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

(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 (unburned hydrocarbon)
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 of Table 2, the fuel oil compositions for premixed compression self-ignition engines of the present invention obtained in Examples 1 to 3 are good for the evaluation items (1) to (5). Results
It was confirmed that NO _x , PM, SOF, sulfate and THC in the exhaust gas of the premixed compression self-ignition engine can be efficiently reduced.

The fuel oil composition for a premixed compression self-ignition engine of the present invention can reduce NOx, PM, etc. contained in exhaust gas when used in a premixed compression self-ignition engine, and can improve fuel efficiency. Can be improved.

Claims (4)

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) Cetane index: 60 or less (4) Density: 0.801 g / cm ³ or more (5) Total aromatic content: 15 vol% or more (6) Sulfur content: 10000 mass ppm or less (7) Nitrogen content Content: 500 mass ppm or less 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, wherein the content of trace impurities is 50 mg / L or less. 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, characterized in that a wear scar in an HFRR (High Frequency Reciprocating Rig) test is 500 μm or less. In the fuel oil composition for a premixed compression self-ignition engine according to any one of claims 1 to 3,
A fuel oil composition for premixed compression self-ignition engines, characterized in that the induction period is 960 minutes or longer.