CN115422686A - Engine performance improvement method based on accurate local heat insulation of combustion chamber - Google Patents
Engine performance improvement method based on accurate local heat insulation of combustion chamber Download PDFInfo
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- CN115422686A CN115422686A CN202211234398.6A CN202211234398A CN115422686A CN 115422686 A CN115422686 A CN 115422686A CN 202211234398 A CN202211234398 A CN 202211234398A CN 115422686 A CN115422686 A CN 115422686A
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 52
- 238000009413 insulation Methods 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 19
- 230000006872 improvement Effects 0.000 title claims description 4
- 238000004364 calculation method Methods 0.000 claims abstract description 7
- 238000002347 injection Methods 0.000 claims description 8
- 239000007924 injection Substances 0.000 claims description 8
- 238000004088 simulation Methods 0.000 claims description 8
- 239000007921 spray Substances 0.000 claims description 7
- 230000004907 flux Effects 0.000 claims description 6
- 239000000446 fuel Substances 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 235000002020 sage Nutrition 0.000 claims description 3
- 230000004888 barrier function Effects 0.000 claims 1
- 230000006866 deterioration Effects 0.000 abstract description 4
- 238000005728 strengthening Methods 0.000 abstract description 3
- 238000010438 heat treatment Methods 0.000 abstract description 2
- 239000012720 thermal barrier coating Substances 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000017525 heat dissipation Effects 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/17—Mechanical parametric or variational design
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B77/00—Component parts, details or accessories, not otherwise provided for
- F02B77/11—Thermal or acoustic insulation
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- G06F2119/08—Thermal analysis or thermal optimisation
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- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
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Abstract
The method is based on the calculation of heat flow density and fuel-air equivalent ratio of each part of the wall surface of a combustion chamber, partial areas are selected for heat insulation treatment, heat insulation is not carried out on places with less heat flow distribution, intake air heating is relieved, meanwhile, the problem of near-wall combustion after high strengthening of a diesel engine can be effectively relieved, combustion is more sufficient, and in addition, the deterioration of charging efficiency is relieved, so that the performance of the engine is comprehensively improved.
Description
Technical Field
The invention relates to the technical field of engines, in particular to a method for improving engine performance through local heat insulation of a combustion chamber.
Background
In order to reduce heat dissipation loss and improve the thermal efficiency of the engine, combustion chamber insulation technology is widely used. The heat insulation technology is adopted to improve the heat efficiency of the engine, and simultaneously, the charging efficiency is inevitably worsened, because the temperature of the inner wall surface of the cylinder is too high due to the heat insulation technology, so that the fresh charging is heated in the air intake stroke, the density of the fresh air is reduced, and the air intake quality is reduced.
In order to solve this problem, many studies have adopted a form of partial insulation, that is, an insulation treatment is performed on a partial region of the combustion chamber, which helps to alleviate deterioration of the charging efficiency. However, when the heat insulation area is selected, only the macro area is selected, for example, only the piston is subjected to heat insulation treatment, or only a certain characteristic part of the piston is subjected to heat insulation treatment, and the heat insulation area is not selected in a refined manner, so that some irrelevant areas are also subjected to heat insulation treatment, and the improvement of the thermal efficiency is not beneficial basically, but the deterioration of the inflation efficiency is aggravated.
On the other hand, the increasing of the strengthening degree of the diesel engine, the fuel injection pressure and the fuel injection quantity are greatly increased, which inevitably results in the increase of the fuel wall attachment quantity, and the oil film formed by the spray hitting the wall leads to poor oil-gas mixing, incomplete combustion and high emissions of unburned hydrocarbon, carbon monoxide and the like due to the low evaporation rate, especially in the cold start stage of the engine.
Researches find that the surface temperature of the wall surface of the heat-insulating combustion chamber is increased by coating a thermal barrier coating on the surface layer of the metal wall surface, which is beneficial to strengthening the wall-attached combustion and relieving a series of problems caused by slow evaporation rate of a wall-attached oil film and low temperature of the wall surface. However, the current research does not consider the effect on coanda combustion on the selection of the insulation zone when using partial insulation techniques.
Disclosure of Invention
The disclosure provides a universal partial heat insulation method, which comprehensively considers the comprehensive influence of a heat insulation area on heat efficiency, inflation efficiency and coanda combustion and provides theoretical support for selection of the heat insulation area of an engine combustion chamber.
The engine performance improving method based on accurate local heat insulation of the combustion chamber comprises the following steps:
step 1, establishing a three-dimensional simulation model of a fuel engine;
step 2, calculating the heat flux density q of each wall surface of the combustion chamber in the working cycle process of the engine by using the three-dimensional simulation model established in the step 1, and simultaneously calculating the equivalence ratio distribution phi of the mixed gas in the combustion chamber at the moment of oil injection ending;
step 3, converting the heat flow density values of all the walls of the combustion chamber, which are obtained by calculation in the step 2, into circulating average heat flow density values respectively:
q i the heat flow density value at each moment in the step 2 is n, and the number of times of outputting the heat flow density result of one engine cycle is n;
step 4, normalizing the circulating average heat flow density value of each wall surface of the combustion chamber obtained by calculation in the step 3:
step 5, selecting an area for heat insulation treatment based on the normalized heat flow density value of the wall surface of the combustion chamber;
step 6, selecting a region for heat insulation treatment based on the fuel-air equivalence ratio distribution in the combustion chamber at the oil injection finishing moment calculated in the step 2;
and 7, performing Boolean addition operation on the region selected in the step 5 and the region selected in the step 6, performing Boolean subtraction operation on the operation result and the cylinder side wall surface region below the first ring groove when the piston is positioned at the top dead center, and determining the region finally subjected to heat insulation treatment.
Further, the specific method of step 1 includes:
adopting Converge software to establish a CFD three-dimensional simulation model of the engine, wherein the model comprises a turbulence model, a spray model and a combustion model, the turbulence model adopts an RNGk-epsilon model, the spray crushing model adopts a KH-RT model, and the combustion model adopts an SAGE model;
the boundary conditions in the CFD model are set using a first type of boundary conditions, i.e., the wall temperature of each boundary is set.
Further, in the step 2, the heat flux density q is output every 1 ° CA.
Further, in the step 5, a region with the normalized heat flow density value exceeding 0.5 is selected as a heat insulation treatment region, that is, a thermal barrier coating is coated on the region with the normalized heat flow density value exceeding 0.5 to insulate heat, and the other regions are not subjected to heat insulation treatment.
Further, in the step 6, a region in which the fuel-air equivalence ratio in the vicinity of the combustion chamber near the wall surface exceeds 2 is selected as the heat-insulating treatment region.
Compared with the prior art, this disclosed beneficial effect is: (1) the heat insulation area of the combustion chamber is selected based on heat flow distribution, so that high-efficiency heat insulation can be realized, namely, the wall area of the combustion chamber with high heat flow density is selected for heat insulation, so that heat dissipation is effectively prevented, and the heat efficiency is improved; heat insulation is not carried out on the place with less heat flow distribution, and the intake heating is relieved; (2) the selection of the heat insulation area of the combustion chamber is carried out based on the equivalence ratio distribution, so that the problem of near-wall combustion after the diesel engine is highly strengthened can be effectively relieved, and the combustion is more sufficient; (3) the deterioration of the charging efficiency is relieved and the near-wall combustion is enhanced while the high-efficiency heat insulation is realized.
Drawings
The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular descriptions of exemplary embodiments of the disclosure as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the disclosure.
FIG. 1 shows a flow chart of a method of locally insulating a diesel engine according to the present disclosure.
Detailed Description
Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The present disclosure provides a method of improving engine performance through precise local thermal isolation of the combustion chamber. The specific steps of an exemplary embodiment are shown in fig. 1, and include:
step 1, establishing a three-dimensional simulation model of a certain diesel engine by using engine CFD simulation software.
Preferably, in this embodiment, a converter software is used to establish a CFD simulation model of a certain diesel engine, and the model includes a turbulence model, a spray model, and a combustion model. The turbulence model is an RNGk-epsilon model, a KH-RT model is adopted in the spray crushing model, an SAGE model is adopted in the combustion model, and a Soot and NOx emission model is started. The setting of the boundary conditions in the CFD model adopts the first type of boundary conditions, namely, the wall surface temperature of each boundary is set:
and 2, calculating the heat flux density q of each wall surface of the combustion chamber in the working cycle process of the engine by using the CFD model established in the step 1, and calculating the equivalence ratio distribution phi of the mixed gas in the combustion chamber at the oil injection end moment.
The combustion chamber wall surface in this embodiment includes: piston, cylinder cap, cylinder jacket. Preferably, the heat flux density q is output every 1 ° CA.
Step 3, converting the heat flow density values of all the walls of the combustion chamber, which are obtained by calculation in the step 2, into circulating average heat flow density values respectively:
q i for the heat flow density value at each time in step 2, n is the number of times the heat flow density result of one engine cycle is output, and since it is output every 1 ° CA, n is 720 here.
And 4, normalizing the circulating average heat flow density value calculated in the step 3.
Step 5, selecting an insulation area based on the heat flow density values of all the walls of the normalized combustion chamber: preferably, the area with the normalized heat flow density value exceeding 0.5 is subjected to heat insulation treatment, namely, the area with the heat flow density value exceeding 0.5 is coated with a thermal barrier coating to perform heat insulation, and other areas are not subjected to heat insulation treatment.
And 6, selecting an insulation area based on the fuel-air equivalence ratio distribution in the combustion chamber at the oil injection finishing moment obtained by calculation in the step 2: the area with the fuel-air equivalent ratio exceeding 2 near the wall surface of the combustion chamber is coated with a thermal barrier coating for heat insulation, so that the near-wall combustion is enhanced, and the heat dissipation loss is reduced.
Step 7, considering that the area below the first ring groove can not be coated with the thermal barrier coating when the piston is positioned at the top dead center due to the friction generated by the contact of the side wall surface of the cylinder and the piston ring, the final spraying area of the thermal barrier coating is as follows: and (4) performing Boolean addition operation on the region of which the heat flow density exceeds 0.5 in the step (5) and the region of which the fuel-air equivalent ratio in the vicinity of the wall surface of the combustion chamber exceeds 2 in the step (6), and performing Boolean subtraction operation on the operation result and the region of the wall surface of the cylinder below the first ring groove when the piston is positioned at the top dead center to obtain a final heat insulation treatment region.
The foregoing is illustrative of the present invention and various modifications and changes in form or detail will readily occur to those skilled in the art based upon the teachings herein and the application of the principles and principles disclosed herein, which are to be regarded as illustrative rather than restrictive on the broad principles of the present invention.
Claims (5)
1. An engine performance improvement method based on accurate local thermal insulation of a combustion chamber comprises the following steps:
step 1, establishing a three-dimensional simulation model of a fuel engine;
step 2, calculating the heat flux density q of each wall surface of the combustion chamber in the working cycle process of the engine by using the three-dimensional simulation model established in the step 1, and calculating the equivalence ratio distribution phi of the mixed gas in the combustion chamber at the moment of ending oil injection;
step 3, converting the heat flow density values of the walls of the combustion chamber calculated in the step 2 into circulating average heat flow density values respectively:
q i the heat flow density value at each moment in the step 2 is n, and the number of times of outputting the heat flow density result of one engine cycle is n;
step 4, normalizing the circulating average heat flow density value of each wall surface of the combustion chamber, which is obtained by calculation in the step 3:
step 5, selecting an area for heat insulation treatment based on the normalized heat flow density value of the wall surface of the combustion chamber;
step 6, selecting a region for heat insulation treatment based on the fuel-air equivalence ratio distribution in the combustion chamber at the oil injection finishing moment calculated in the step 2;
and 7, performing Boolean addition on the area selected in the step 5 and the area selected in the step 6, performing Boolean subtraction on the calculation result and the area of the cylinder side wall below the first ring groove when the piston is positioned at the top dead center, and determining the area finally subjected to heat insulation treatment.
2. The method as claimed in claim 1, wherein the specific method of step 1 comprises:
adopting Converge software to establish a CFD three-dimensional simulation model of the engine, wherein the model comprises a turbulence model, a spray model and a combustion model, the turbulence model adopts an RNGk-epsilon model, the spray crushing model adopts a KH-RT model, and the combustion model adopts an SAGE model;
the boundary conditions in the CFD model are set using a first type of boundary conditions, i.e., the wall temperature of each boundary is set.
3. The method of claim 1, wherein in step 2, the heat flux density q is output every 1 ° CA.
4. The method according to any of claims 1 to 3, characterized in that in step 5, the area with the normalized heat flow density value exceeding 0.5 is selected as the heat-shielding treatment area, i.e. the area with the heat flow density value exceeding 0.5 is heat-shielded by coating the heat barrier coating, and the other area is not heat-shielded.
5. The method according to claim 4, wherein in the step 6, a region in which the fuel-air equivalence ratio in the vicinity of the combustion chamber near the wall surface exceeds 2 is selected as the heat-insulating treatment region.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112231903A (en) * | 2020-10-13 | 2021-01-15 | 西北工业大学 | Multi-objective optimization design scheme of circular super-combustion chamber based on genetic algorithm |
| CN113326564A (en) * | 2021-05-25 | 2021-08-31 | 南京航空航天大学 | Method for obtaining transient temperature field of gradient composite heat insulation structure |
| US20220003183A1 (en) * | 2020-07-01 | 2022-01-06 | Mazda Motor Corporation | Method for predicting combustion state of engine |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20220003183A1 (en) * | 2020-07-01 | 2022-01-06 | Mazda Motor Corporation | Method for predicting combustion state of engine |
| CN112231903A (en) * | 2020-10-13 | 2021-01-15 | 西北工业大学 | Multi-objective optimization design scheme of circular super-combustion chamber based on genetic algorithm |
| CN113326564A (en) * | 2021-05-25 | 2021-08-31 | 南京航空航天大学 | Method for obtaining transient temperature field of gradient composite heat insulation structure |
Non-Patent Citations (2)
| Title |
|---|
| AKIO KAWAGUCHI 等: "Thermo-swing insulation to reducce heat loss from the combustion chamber wall of a diesel engine", INSTITUTION OF MECHANICAL ENGINEERS, vol. 20, no. 7 * |
| 山下親典等: "发动机燃烧室隔热技术的发展与展望", 汽车与新动力, no. 2021 * |
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