摘 要
冷卻水的流動(dòng)與傳熱直接影響到柴油機(jī)的冷卻效率、高溫零件的熱負(fù)荷、整機(jī)的熱量分配和能量利用。雖然從能量觀點(diǎn)來(lái)看，柴油機(jī)的冷卻是一種能量損失，但只有使柴油機(jī)受熱零部件得到適度的冷卻，使其溫度維持在允許的范圍內(nèi)，才能保證其有效而可靠的工作。所以，對(duì)柴油機(jī)缸套冷卻性能的研究對(duì)改善柴油機(jī)冷卻效率和提高氣缸缸套可靠性有重要的意義。
在柴油機(jī)冷卻問(wèn)題的各種研究方法中，計(jì)算流體力學(xué)已經(jīng)成為一個(gè)重要的手段。在冷卻系統(tǒng)數(shù)值模擬過(guò)程中，由于傳熱邊界條件難以確定，多數(shù)研究者僅僅考慮了冷卻水的流動(dòng)問(wèn)題，在計(jì)算傳熱問(wèn)題時(shí)，將冷卻液的流動(dòng)作為人為的邊界條件進(jìn)行處理。本文采用流固耦合的方法，建立冷卻水腔與缸套之間三維耦合的模型，將冷卻水流場(chǎng)與缸套溫度場(chǎng)進(jìn)行整體耦合，從而避免了對(duì)冷卻水側(cè)施加固定壁溫及冷卻液流動(dòng)的邊界條件。利用FLUENT軟件自帶的UDF功能對(duì)燃?xì)鈧?cè)換熱系數(shù)及溫度進(jìn)行編程，從而實(shí)現(xiàn)了對(duì)燃?xì)鈧?cè)施加第三類邊界條件，通過(guò)固體與流體之間的耦合，可以使施加的邊界條件更為準(zhǔn)確。
用耦合的方法計(jì)算分析了某船用柴油機(jī)內(nèi)冷卻水的流動(dòng)、溫度分布、壓力分布以及缸套溫度場(chǎng)的分布情況，并將計(jì)算結(jié)果與傳統(tǒng)的固定邊界條件結(jié)果進(jìn)行對(duì)比分析。分析結(jié)果表明，通過(guò)流場(chǎng)與溫度場(chǎng)的耦合計(jì)算，能夠得到更加準(zhǔn)確的冷卻水流動(dòng)情況、壓力分布以及冷卻水出口溫度，同時(shí)還能得出缸套溫度場(chǎng)的分布情況，說(shuō)明固體與流動(dòng)之間耦合的數(shù)值模擬能夠更客觀的反映柴油機(jī)冷卻系統(tǒng)的流動(dòng)與傳熱問(wèn)題，并且能為冷卻系統(tǒng)的優(yōu)化設(shè)計(jì)提供重要的參考依據(jù)。

關(guān)鍵詞 柴油機(jī)；冷卻系統(tǒng)；流動(dòng)與傳熱；數(shù)值模擬；耦合計(jì)算

Abstract
The flow and heat transfer of cooling water has directly effect on the cooling efficiency of diesel engine, the heat load of high temperature parts and the heat distribution and energy use of whole diesel engine. Although, at the view of energy, the engine cooling is an energy loss process, it is the necessary process during the work of diesel engine. Because it is necessary to keep the temperature of the high temperature parts within the permissible range, in order to ensure the effective and reliable work of the diesel engine. Generally speaking, the research on cooling performance of diesel engine cylinder has great significance on improving the diesel engine’s cooling efficiency and the reliability of cylinder liner.
The computational fluid dynamics is one of the most important research methods in the research on diesel engine cooling problems. During the numerical simulation process of cooling system, because of the boundary conditions of heat transfer is difficult to determine, most researchers only considered the problem of cooling water flow. In addition, when calculated the heat transfer, they treated the coolant flow as artificial boundary condition. In this paper, the fluid-structure coupling method was used; the three-dimensional coupling model of cooling water chamber and cylinder was established. In the model, the cooling water flow field and cylinder temperature field was coupled, in which way the set of fixed wall temperature and coolant flow boundary condition were avoided. Using the UDF module of FLUENT to program the transfer coefficient and temperature at the gas side, and then the third type boundary condition exerted on the gas side was realized. It made the exertion of the boundary conditions more accurate, by coupling between fluids and solid.
The coupling method was used to analyze the cooling water flow field, temperature distribution, pressure distribution and the cylinder liner temperature distribution, and compare the calculation results and the traditional fixed boundary condition calculation results. The more accurate flow condition of cooling water, pressure distribution, the cooling water temperature at outlet, and the cylinder liner temperature distribution were obtained, through calculating of flow field and temperature field. The calculation results show that the coupling numerical simulation method could describe the flow and heat transfer problem of diesel engine more objectively. And the calculation results could provide important reference for the optimized design of cooling system.
Keywords Cooling system; Flow and transfer; Numerical simulation; Coupling calculation

目 錄
摘 要 I
Abstract III
第1章 緒 論 1
1.1 課題來(lái)源及研究意義 1
1.2 柴油機(jī)熱負(fù)荷研究現(xiàn)狀 1
1.2.1 實(shí)驗(yàn)測(cè)量 1
1.2.2 數(shù)值仿真計(jì)算 2
1.2.2.1缸套傳熱微分方程及邊界條件計(jì)算發(fā)展現(xiàn)狀 2
1.2.2.2數(shù)值計(jì)算方法發(fā)展現(xiàn)狀 4
1.3 有限體積法在發(fā)動(dòng)機(jī)設(shè)計(jì)中的應(yīng)用 6
1.4 有限體積法在發(fā)動(dòng)機(jī)設(shè)計(jì)中的缺陷 6
1.5本研究的主要內(nèi)容及意義 7
第2章 流固耦合 9
2.1 流固耦合理論 9
2.2 用戶自定義函數(shù)(UDF) 10
2.3本章小結(jié) 11
第3章 數(shù)值模擬計(jì)算模型及邊界條件 12
3.1 柴油機(jī)參數(shù)介紹 13
3.2 冷卻水流動(dòng)控制方程及其求解條件 13
3.2.1 冷卻水流動(dòng)控制方程 13
3.2.2 湍流模型 14
3.2.3 流動(dòng)邊界條件 15
3.3 導(dǎo)熱微分方程及其求解條件 16
3.3.1 導(dǎo)熱微分方程 16
3.3.2 方程的求解條件 18
3.3.3 傳熱邊界條件 18
3.4 缸套溫度場(chǎng)計(jì)算 19
3.4.1 缸套溫度場(chǎng)計(jì)算的換熱微分方程 19
3.4.2 燃?xì)鈧?cè)邊界條件及UDF的應(yīng)用 19
3.4.3 缸套與機(jī)體和缸蓋接觸面之間的換熱系數(shù) 24
3.4.4 缸套外側(cè)冷卻水換熱系數(shù)的分布 24
3.5 本章小結(jié) 25
第4章 模擬計(jì)算與分..