Corrosion-resistant methanol engine wet cylinder sleeve

Abstract

The invention provides a corrosion-resistant methanol engine wet cylinder sleeve, and belongs to the technical field of internal combustion engines. The methanol engine wet cylinder sleeve is composed of a stainless steel 2507 matrix, and the stainless steel 2507 matrix comprises the following chemical components in percentage by weight: less than or equal to 0.03% of C; chromium (Cr): 24.0%-26.0%; 3%-5% of Mo (molybdenum); 6.0%-8.0% of nickel (Ni); copper Cu: less than or equal to 0.5%; mn: less than or equal to 1.2%; si: less than or equal to 0.8%; less than or equal to 0.035% of phosphorus P; 0.24% to 0.32% of nitrogen N; and the balance of Fe and inevitable impurities. And a lift reticulate pattern structure is honed on the inner surface. The corrosion problem of the methanol engine cylinder sleeve can be effectively solved; the honing surface of 15-30 degrees is arranged on the inner side of the cylinder sleeve to process reticulate patterns, necessary lubricating oil can be stored, and therefore abrasion reduction in the piston operation process is achieved; the cooling area base body is thinned, the annular heat dissipation ribs are additionally arranged on the base body, the heat exchange effect is enhanced, and heat balance of engine cooling is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of internal combustion engines, and relates to a corrosion-resistant wet cylinder liner for a methanol engine, in particular to a wet cylinder liner suitable for a methanol fuel engine. Specifically, the present application provides a cylinder liner which is specially structured by using a special stainless steel material, can effectively resist corrosion and wear of methanol fuel and its combustion products, and effectively coordinate heat balance. BACKGROUND

[0002] Methanol, as a clean and renewable alternative fuel, is increasingly widely used in engines. However, methanol and its combustion products (such as formic acid, formaldehyde) have strong chemical corrosiveness and dilution effect on lubricating oil, which brings severe challenges to traditional engine components. The cylinder liner, as a core friction pair component, has a particularly harsh working environment.

[0003] The traditional cast iron cylinder liner exposed in the methanol engine has more serious corrosion problems than in the gasoline engine: the by-products such as methanol and formic acid produced by methanol combustion can cause serious acid corrosion of cast iron, destroy the smoothness of the cylinder wall surface, and aggravate wear. Although stainless steel is corrosion-resistant, its direct application in the cylinder liner of a methanol engine still has problems of wear resistance and heat balance. Considering that the heat conduction ability (thermal conductivity is about 10-30 W / (m·K)) of stainless steel is lower than that (thermal conductivity is about 52-60 W / (m·K)) of cast iron, the best balance between corrosion resistance, thermal conductivity and mechanical strength needs to be achieved as a cylinder liner for a methanol engine.

[0004] Therefore, developing a cylinder liner specially used for a methanol engine, which can simultaneously solve corrosion and wear, has become a key to promoting the commercial application of methanol fuel technology. SUMMARY

[0005] In view of the characteristics of methanol fuel, the present application provides a stainless steel wet cylinder liner for a methanol engine. The cylinder liner has excellent methanol corrosion resistance, excellent wear resistance and necessary heat conduction strength, and completely solves the problems of poor adaptability and short service life of traditional cylinder liners in methanol engines.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The application discloses a corrosion-resistant wet cylinder liner of a methanol engine, which is composed of a stainless steel 2507 base body, and the chemical composition of the stainless steel 2507 base body comprises the following components in percentage by weight: carbon (C): 0.03% or less; chromium (Cr): 24.0%-26.0%; molybdenum (Mo): 3%-5%; nickel (Ni): 6.0%-8.0%; copper (Cu): 0.5% or less; manganese (Mn): 1.2% or less; silicon (Si): 0.8% or less; phosphorus (P): 0.035% or less; nitrogen (N): 0.24%-0.32%; and the rest is iron (Fe) and inevitable impurities. After solid solution treatment, a balanced dual-phase structure (gamma and delta are about 50% respectively) is obtained, and harmful phases are dissolved, so that the material has the best toughness and corrosion resistance.

[0008] Further, the inner surface of the stainless steel wet cylinder liner with the 2507 base body is honed with a 15-30° honing pattern, and the honing pattern is within the range of piston stroke and has Ra≤0.63 μm, the honing pattern is helpful to form a lubricating oil storage groove and realize wear reduction.

[0009] Further, considering the low thermal conductivity of the 2507, the wall thickness of the cooling area of the cylinder liner is reduced, and the annular heat dissipation ribs are increased, the heat dissipation ribs are helpful to improve heat exchange and reduce the problem of uneven heat dissipation caused by the low thermal conductivity of the material.

[0010] The application has the following beneficial effects:

[0011] (1) The application is based on the excellent corrosion resistance of the 2507 in methanol and combustion by-products, and the 2507 is used in the methanol engine to be a corrosion-resistant cylinder liner on the basis of the test of the corrosion resistance, so that the corrosion problem of the cylinder liner of the methanol engine can be effectively solved.

[0012] (2) According to the working principle of the engine, the honing surface processing pattern of 15-30 degrees is arranged on the inner side of the cylinder liner, necessary lubricating oil can be stored, and wear reduction in the piston operation process can be realized.

[0013] (3) According to the low thermal conductivity of the 2507 duplex stainless steel, the base body of the cooling area is thinned in the design, and the annular heat dissipation ribs are increased on the base body, so that the heat exchange effect is enhanced, and the thermal balance of the engine cooling is ensured. DETAILED DESCRIPTION

[0014] Figure 1 The application discloses a corrosion-resistant wet cylinder liner of a methanol engine, which is composed of a stainless steel 2507 base body, and the chemical composition of the stainless steel 2507 base body comprises the following components in percentage by weight: carbon (C): 0.03% or less; chromium (Cr): 24.0%-26.0%; molybdenum (Mo): 3%-5%; nickel (Ni): 6.0%-8.0%; copper (Cu): 0.5% or less; manganese (Mn): 1.2% or less; silicon (Si): 0.8% or less; phosphorus (P): 0.035% or less; nitrogen (N): 0.24%-0.32%; and the rest is iron (Fe) and inevitable impurities. After solid solution treatment, a balanced dual-phase structure (gamma and delta are about 50% respectively) is obtained, and harmful phases are dissolved, so that the material has the best toughness and corrosion resistance.

[0015] Figure 2 The application discloses a corrosion-resistant wet cylinder liner of a methanol engine, which is composed of a stainless steel 2507 base body, and the chemical composition of the stainless steel 2507 base body comprises the following components in percentage by weight: carbon (C): 0.03% or less; chromium (Cr): 24.0%-26.0%; molybdenum (Mo): 3%-5%; nickel (Ni): 6.0%-8.0%; copper (Cu): 0.5% or less; manganese (Mn): 1.2% or less; silicon (Si): 0.8% or less; phosphorus (P): 0.035% or less; nitrogen (N): 0.24%-0.32%; and the rest is iron (Fe) and inevitable impurities. After solid solution treatment, a balanced dual-phase structure (gamma and delta are about 50% respectively) is obtained, and harmful phases are dissolved, so that the material has the best toughness and corrosion resistance.

[0016] Figure 3 This is a comparison of the corrosion morphology of the cylinder liner substrate of the present invention and the traditional cast iron cylinder liner in pure methanol.

[0017] Figure 4 This is a comparison of the corrosion morphology of the cylinder liner substrate of the present invention and the traditional cast iron cylinder liner in formaldehyde.

[0018] Figure 5 A comparison of the corrosion morphology of the cylinder liner substrate of this invention and that of a traditional cast iron cylinder liner in formic acid.

[0019] In the diagram: 1. Cylinder liner; 2. Cylinder block; 3. Cooling water chamber; 4. Sealing ring; 5. Sealing ring; 6. Cylinder liner inner wall; 7. Cooling fins. Detailed Implementation

[0020] The present invention will be further described below with reference to specific implementation examples.

[0021] To illustrate the corrosion resistance of the stainless steel cylinder liner described in this invention in methanol and its combustion products, the following corrosion comparison test was conducted.

[0022] 1) Test sample:

[0023] Experimental group: Stainless steel cylinder liner material prepared according to the embodiments of the present invention. Specifically, carbon (C): ≤0.03%; chromium (Cr): 24.0%~26.0%; molybdenum (Mo): 3%~5%; nickel (Ni): 6.0%~8.0%; copper (Cu): ≤0.5%; manganese (Mn): ≤1.2%; silicon (Si): ≤0.8%; phosphorus (P): ≤0.035%; nitrogen (N): 0.24%~0.32%; the remainder is iron (Fe) and unavoidable impurities. Then, a solution treatment was performed to obtain a uniform duplex structure.

[0024] Control group: Currently, the mainstream high-performance cast iron cylinder liner material used in methanol engines is mainly alloy cast iron. Specifically, its main components are: carbon (C): 3.1-3.4%; chromium (Cr): 0.1%~0.3%; copper (Cu): 0.4-0.6%; manganese (Mn): 0.6-0.9%; silicon (Si): 1.9-2.3%; tin (Sn): 0.06-0.09%; phosphorus (P): ≤0.15%; sulfur (S): ≤0.12%, with the remainder being iron (Fe) and unavoidable impurities.

[0025] 2) Test method:

[0026] Immersion corrosion test was conducted. Two groups of cylinder liner material samples were immersed in methanol (AR), methanol containing 1.5% formaldehyde, and methanol containing 0.02% formic acid solutions (simulating methanol combustion products), respectively.

[0027] The samples were suspended in the test solution without contacting the container walls, and the experimental setup used a temperature-controlled water bath maintained at 30°C. Each group contained three parallel samples. The soaking solution was changed every 5 days during the soaking process. After 30 days of soaking, the samples underwent post-testing treatment: (1) gentle removal of surface deposits using a nylon brush, (2) ethanol rinsing and drying, and (3) final mass measurement for corrosion rate calculation. The corrosion rate was determined by the following mass loss equation:

[0028] (1)

[0029] Where Rcor is the corrosion weight loss rate (mm / a, 1a = 8760h); 'b' is the conversion factor (value 8760); 'M' is the weight of the metal before the test (g); 'M1' is the weight of the metal after the test (g); 'A' is the total surface area of ​​the metal (mm²). 2 ); 't' represents the test time (h); ρ represents the density of the metal (g / mm³). 3 ).

[0030] The weight loss of the samples before and after the experiment was measured, and the corrosion rate was calculated. The corrosion rates are shown in Table 1.

[0031] The corrosion morphology was observed using scanning electron microscopy. The corrosion morphology results are shown in the appendix. Figure 3 , 4, 5

[0032] 3) Test results:

[0033]

[0034] Comparison of corrosion rates in Table 1 and Figures 3-5 The corrosion morphology shows that the 2507 selected in this patent has significantly improved corrosion resistance in methanol, formaldehyde, and formic acid environments.

[0035] Implementation of structural features:

[0036] The cylinder liner of this invention, designed with 2507 stainless steel, has good corrosion resistance. To ensure wear resistance and thermal balance during use, the design needs to incorporate the following... Figure 1 Installation and design shown:

[0037] like Figure 1 As shown, the inner wall 6 of the cylinder liner needs to be designed as follows: Figure 1 The textured structure shown ensures wear resistance.

[0038] like Figure 1As shown, cylinder liner 1 is installed on the mating surface of the cylinder block, thereby achieving the positioning and installation of cylinder liner 1. The lower end of cylinder liner 1 is sealed to cylinder block 2 by a first sealing ring 4 and a second sealing ring 5. A cooling water chamber 3 is formed between cylinder liner 1 and cylinder block 2. Under the action of the engine water pump, the fluid in the cooling water chamber 3 will quickly pass over the heat dissipation fins 7. At the same time, the reduction in the size of the cooling water jacket base of cylinder liner 1 also effectively reduces thermal resistance and enhances heat exchange.

[0039] Taking a 110-cylinder engine as an example: the thickness of conventional cast iron cylinder liners is typically 8-10 mm, and the tensile strength of cast iron (250-400 MPa) is only half that of 2507 material (tensile strength 800 MPa). Based on the higher tensile strength of 2507 material, the cylinder liner thickness can be reduced in the design, and a heat dissipation annular fin with a thickness equivalent to the 2507 base material can be designed at position 3 of the cooling water chamber. If the fin width is the same as the width of the unfinished area, the heat dissipation area can be increased by approximately 30%; furthermore, the fluid velocity between the fin gaps will increase, thereby increasing the convective heat transfer coefficient of the fluid and effectively compensating for the poor heat dissipation of stainless steel.

[0040] To ensure heat dissipation balance, the height and density of the heat dissipation fins 7 can be adjusted to achieve thermal stability during engine operation.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A corrosion-resistant wet cylinder liner for a methanol engine, characterized in that, The methanol engine wet cylinder liner is made of stainless steel 2507 matrix. The chemical composition of the stainless steel 2507 matrix, by weight percentage, includes: carbon C: ≤0.03%; chromium Cr: 24.0% ~ 26.0%; molybdenum Mo: 3% ~ 5%; nickel Ni: 6.0% ~ 8.0%; copper Cu: ≤ 0.5%; manganese Mn: ≤ 1.2%; silicon Si: ≤ 0.8%; phosphorus P: ≤ 0.035%; nitrogen N: 0.24% ~ 0.32%; the remainder is iron Fe and unavoidable impurities.

2. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 1, characterized in that, The inner surface of the wet cylinder liner of the methanol engine is machined with a textured structure.

3. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 2, characterized in that, A 15-30 degree honing surface texture is applied to the inner surface of the wet cylinder liner of a methanol engine.

4. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 1, characterized in that, The inner surface of the wet cylinder liner of the methanol engine has a thickness Ra≤0.63μm within the piston stroke range.

5. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 1, characterized in that, The cooling area of ​​the wet cylinder liner of the methanol engine is enhanced with annular fins for heat dissipation.

6. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 1, characterized in that, The stainless steel 2507 matrix, after solution treatment, can obtain a balanced duplex structure.

7. The corrosion-resistant wet cylinder liner for a methanol engine according to claim 1, characterized in that, The methanol engine wet cylinder liner is installed on the cylinder block mating surface to achieve cylinder liner positioning and installation; wherein, the lower end of the methanol engine wet cylinder liner is sealed to the cylinder block by a sealing ring, forming a cooling water chamber between the cylinder block and the cylinder block. Under the action of the engine water pump, the fluid in the cooling water chamber sweeps over the annular ribs to enhance heat exchange.

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