A method for improving diesel engine combustion efficiency by alleviating local oxygen deficiency through chemical chaining

Abstract

The present invention discloses a method for improving the combustion efficiency of a diesel engine by alleviating local hypoxia by using a chemical chain. The method loads an oxygen carrier coating onto the inner wall of a diesel engine cylinder, uses CeO2 / Fe2O3 as an oxygen carrier, and fully oxidizes the small molecule fuel pyrolysis products near the cylinder wall into CO2 and H2O during the fuel spray pyrolysis stage. The reduced oxygen carrier will be reoxidized into Fe2O3 during the next intake stroke, thereby realizing the recycling of the oxygen carrier. In the temperature window of the normal operation of the diesel engine, the oxygen carrier of the present invention can convert the small molecule fuel pyrolysis products that would otherwise generate unburned hydrocarbons, PAHs, soot and other pollutants under local high temperature and hypoxia conditions into pollution-free CO2 and H2O and additional heat output. Moreover, since the oxygen carrier exists in the form of a coating on the inner wall surface of the cylinder, no additional emission pollution will be generated, thereby profoundly improving energy efficiency, reducing pollutant emissions, and being green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to a method for improving the combustion efficiency of a diesel engine by utilizing a chemical chain to alleviate local hypoxia, and belongs to the technical field of improving the combustion efficiency of a diesel engine. Background Art

[0002] Due to the characteristics of diffusion combustion in diesel engines, there will be local high-temperature, oxygen-deficient areas near the inner wall of the cylinder. The fuel enters the cylinder in the form of an oil beam and is atomized. After a brief thermal decomposition, it begins to burn. Under local oxygen-deficient conditions, pollutants such as hydrocarbons, PAHs, and carbon soot are generated, reducing combustion efficiency and causing environmental pollution. To alleviate the reduction in combustion efficiency caused by this local incomplete combustion, the main measures currently taken are to optimize the injection strategy and improve the nozzle and piston structure design. These measures focus on improving the combustion conditions in the diesel engine from the perspective of structure and fuel entry method, making combustion more complete. In addition, the use of fuel additives can also inhibit the generation of pollutants, such as barium dinonylnaphthalenesulfonate and ferrocene. However, the metal elements contained in the main active ingredients of fuel additives can also produce additional pollutants in the exhaust gas.

[0003] The primary current measure to address pollutants produced by incomplete combustion is to install devices such as diesel particulate filters and three-way catalytic converters along the exhaust path to capture or degrade pollutants. These after-treatment devices can significantly reduce diesel engine pollutant emissions. However, most exhaust treatment devices combine capture and catalytic regeneration. Over time, due to factors such as thermal shock, vibration, and particulate clogging, their effectiveness gradually decreases. They also generate additional backpressure, increasing the work done during the exhaust stroke and thus affecting the overall efficiency of the diesel engine.

[0004] The use of coatings on cylinder inner walls to reduce pollutant generation has also received some attention. Existing research focuses on the catalytic effects of common catalysts such as metals and perovskites, often using precious metals as active sites to accelerate combustion and reduce ignition temperatures. However, this has not substantially improved the localized high-temperature hypoxia caused by the uneven distribution of oxygen atoms and hydroxyl groups near the combustion chamber sidewalls, and has also led to negative effects such as catalytic quenching. The actual effect is not significant and has not been applied in production. However, the use of oxygen carrier coatings to alleviate localized hypoxia from the perspective of chemical chaining and oxygen carriers has not received much attention. Summary of the Invention

[0005] The present invention aims to provide a method for improving diesel engine combustion efficiency by alleviating localized oxygen deficiency through chemical chaining, thereby improving diesel engine combustion efficiency and reducing pollutant emissions. This method utilizes CeO2 / Fe2O3 as oxygen carriers and chemical chaining to promote more complete combustion of fuel pyrolysis products.

[0006] The technical solutions for achieving the purpose of the present invention are as follows:

[0007] The method for improving the combustion efficiency of a diesel engine by alleviating local oxygen deficiency through chemical chaining comprises the following steps:

[0008] A CeO2 / Fe2O3 iron-based oxygen carrier is applied as a coating to the ceramic insulation layer on the inner wall of the cylinder. After fuel is sprayed into the cylinder and atomized and pyrolyzed, the Fe2O3 provides oxygen atoms to alleviate the localized oxygen shortage near the combustion chamber sidewalls, creating a high-temperature, oxygen-deficient area caused by uneven distribution of oxygen atoms and hydroxyl groups. Pyrolysis products, including PAHs, hydrocarbons, and soot precursors, are fully oxidized by the Fe2O3 to CO2 and H2O, while the Fe2O3 is reduced to Fe3O4. During the next intake stroke, fresh air enters the cylinder, oxidizing the Fe3O4 with the incoming air, thus enabling the recycling of the iron-based oxygen carrier.

[0009] In the present invention, the iron-based oxygen carrier is covered on the surface of the ceramic heat insulation layer in the form of a coating, and the coating position is on the side wall of the combustion chamber.

[0010] In the present invention, the iron-based oxygen carrier is coated on the surface of the ceramic heat insulation layer by flame spraying.

[0011] In the present invention, the CeO2 / Fe2O3 iron-based oxygen carrier is prepared by conventional methods in the field, and can be specifically prepared by the following steps: Ce(NO3)3·6H2O and Fe(NO3)3·9H2O are mixed according to a doping ratio and dissolved in deionized water, heated and stirred at 70°C until the mixture is uniform, allowed to stand and age at room temperature, dried, heated to 900°C and calcined at a constant temperature, and finally crushed to obtain the CeO2 / Fe2O3 iron-based oxygen carrier.

[0012] Preferably, the doping amount of CeO2 in the CeO2 / Fe2O3 iron-based oxygen carrier is 10% to 20%.

[0013] Preferably, during the preparation of the CeO2 / Fe2O3 iron-based oxygen carrier, the standing time at room temperature is 12 hours, the drying temperature is 110°C, the drying time is 12 hours, the calcination heating rate is 10°C / min, and the calcination time is 6 hours.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) In the present invention, the oxygen carrier coating provides oxygen atoms to promote more complete combustion of the fuel pyrolysis products, and the reduced oxygen carrier will also be oxidized in the next intake stroke to supplement oxygen atoms. The oxygen carrier in the present invention covers the insulating ceramic surface of the combustion chamber side wall. When it works, the soot precursors, PAHs and other substances in the nearby area are still in the primary stage, with high reactivity and easy reaction with the oxygen carrier, and alleviates the generation and further accumulation of pollutants in the subsequent soot growth process, thereby improving combustion efficiency and reducing the generation of pollutants;

[0016] (2) After the combustion efficiency is improved by the method of the present invention, the products are CO2 and H2O, which do not generate additional pollutants and can be discharged directly. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of a method for improving diesel engine combustion efficiency by utilizing chemical chaining to alleviate local oxygen deficiency, including an oxygen carrier coating (1), a ceramic heat-insulating layer (2), a cylinder base material (3), unburned fuel pyrolysis products generated under local high temperature and oxygen deficiency (4), and products CO2 and H2O (5). DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the embodiments and accompanying drawings.

[0019] like Figure 1 As shown, the present invention utilizes chemical chaining to alleviate local hypoxia and improve the combustion efficiency of diesel engines. It mainly utilizes CeO2 / Fe2O3 as an oxygen carrier, and the oxygen carrier is loaded on the surface of the ceramic heat insulation layer (2) in the form of a coating. The fuel pyrolysis products (4) that cannot be oxidized in time due to local high temperature hypoxia near the wall are fully oxidized by Fe2O3 into CO2 and H2O (5), and Fe2O3 is reduced to Fe3O4. After entering the next intake stroke, fresh air enters the cylinder, and Fe3O4 is oxidized by the incoming air to regenerate Fe2O3, thereby realizing the recycling of the iron-based oxygen carrier.

[0020] The CeO2 / Fe2O3 iron-based oxygen carrier used in the following examples was prepared by the following steps:

[0021] (1) Weigh Fe(NO3)3·9H2O crystals and Ce(NO3)3·6H2O crystals according to the doping ratio and dissolve them in deionized water;

[0022] (2) The mixed solution was heated to 70°C and stirred continuously with an electric stirrer, and ammonia water was added dropwise until the pH value of the mixed solution reached 10, and the solution was allowed to settle;

[0023] (3) The precipitate was separated by filtration and washed with deionized water. The solid was dried in a drying oven at 110°C for 12 h. The dried solid was then heated at 900°C at a rate of 10°C / min and calcined at this temperature for 6 h.

[0024] (4) The calcined block oxygen carrier is crushed by a crusher to obtain CeO2 / Fe2O3 iron-based oxygen carrier, wherein the doping amount of CeO2 is 10%-20%.

[0025] Example 1

[0026] In a fixed-bed reactor, a simulated gas (low-concentration ethylene in nitrogen) was heated to 1000°C to simulate the unburned fuel pyrolysis atmosphere produced by the fuel in the high-temperature, oxygen-deficient area near the combustion chamber sidewall. Alumina thermal insulation ceramics coated with an iron-based oxygen carrier were placed inside the fixed bed to simulate the combustion chamber sidewall after loading the iron-based oxygen carrier. At 1000°C, the pyrolysis gas was fully oxidized by Fe2O3 to CO2 and H2O. The simulated gas was stopped and air was introduced, causing the Fe3O4 to be oxidized by the air and regenerated into Fe2O3, achieving the recycling of the iron-based oxygen carrier. The yield of ethylene to carbon dioxide reached over 92%, and remained above 90% after 20 cycles. At the same time, a ceramic plate without the iron-based oxygen carrier coating was set as a control group. It can be observed that the control ceramic plate has a large amount of carbon deposits, while the ceramic plate loaded with the iron-based oxygen carrier has less carbon deposits on its surface.

Claims

1. A method for improving diesel engine combustion efficiency by alleviating local hypoxia using a chemical chain, characterized in that: The following steps are involved: The CeO2 / Fe2O3 iron-based oxygen carrier is loaded onto the surface of the ceramic insulation layer on the inner wall of the cylinder in the form of a coating. After the fuel is sprayed into the cylinder for atomization and pyrolysis, the unburned fuel pyrolysis products near the wall are fully oxidized by Fe2O3 into CO2 and H2O, and Fe2O3 is reduced to Fe3O4. After entering the next intake stroke, fresh air enters the cylinder and Fe3O4 is oxidized by the incoming air, realizing the recycling of the iron-based oxygen carrier.

2. The method according to claim 1, characterized in that The CeO2 / Fe2O3 iron-based oxygen carrier is covered on the surface of the ceramic insulation layer of the combustion chamber side wall in the form of a coating, and the effective ingredients act in the form of an oxygen carrier.

3. The method according to claim 1, characterized in that The CeO2 / Fe2O3 iron-based oxygen carrier is coated on the surface of the ceramic heat insulation layer by flame spraying.

4. The method according to claim 1, wherein The CeO2 / Fe2O3 iron-based oxygen carrier is prepared by the following steps: Ce(NO3)3·6H2O and Fe(NO3)3·9H2O are mixed according to a doping ratio, dissolved in deionized water, heated at 70°C and stirred until the mixture is uniformly mixed, allowed to stand at room temperature for aging, dried, heated to 900°C and calcined at a constant temperature, and finally crushed to obtain the CeO2 / Fe2O3 iron-based oxygen carrier.

5. The method according to claim 4, characterized in that In the CeO2 / Fe2O3 iron-based oxygen carrier, the doping amount of CeO2 is 10% to 20%.

6. The method according to claim 4, characterized in that The standing time at room temperature is 12 hours, the drying temperature is 110°C, the drying time is 12 hours, the calcination heating rate is 10°C / min, and the calcination time is 6 hours.

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