摘 要
隨著國內外對環(huán)境保護的要求越來越高，人們對船用柴油機的性能也提出了愈來愈苛刻的要求，既要其輸出功率大、比燃料消耗少，又要符合目前日益嚴格的排放法規(guī)要求。柴油機的缸內燃燒是影響其經濟性、動力性和排放性的主要因素，用實驗方法來研究柴油機的缸內工作過程要求有專門的設備，并且由于實驗條件涉及燃燒，除了個別專門實驗室有條件提供測試外，大多數(shù)測試都是難以進行的，所以存在一定的局限性。因此開展用數(shù)值仿真模擬的方法研究柴油機燃燒的過程成為了當前內燃機界研究的一項的重點。
本文利用KIVA-3V程序，以L21/31船用中速柴油機為研究對象，對其缸內過程進行數(shù)值計算研究。分別用KIVA-3V程序的前處理網(wǎng)格生成器K3PREP與專業(yè)劃分網(wǎng)格軟件ANSYS ICEM-CFD對L21/31型船用中速柴油機建立網(wǎng)格模型，選擇了更為合理的模型，并且通過與原機的實測壓力值和NOx排放值與計算值進行對比，驗證了所建模型的正確性。在此基礎上，改變柴油機的轉速、負荷、噴油提前角和進氣延遲角等工況參數(shù)，研究參數(shù)變化對該柴油機缸內過程、整機性能和有害排放物NOx與CO的生成規(guī)律及空間分布規(guī)律的影響。
針對2011年IMO實施的第二階段的NOx排放限制，以及2016年即將實施的第三階段的NOx排放限制，本文在KIVA-3V程序的燃料庫中添加液態(tài)DME的物性參數(shù)，選用液態(tài)DME燃料替代柴油，分析了DME對L21/31型船用中速機NOx排放的影響；并在此基礎上研究了負荷和噴油提前角對L21/31型船用中速機燃用DME時的NOx的排放的影響規(guī)律，為此機型在2016年以后滿足IMO Tier Ⅲ的NOx排放標準提供了有價值的參考，同時為企業(yè)對該機型的改型設計提供理論依據(jù)。

關鍵詞 KIVA-3V；數(shù)值模擬；船用中速柴油機；燃燒過程；二甲醚(DME)

ABSTRACT
With higher requirements for environment protection at home and abroad, people hope to gain a power plant, which needs less energy but releases less pollution emissions. From this point of view, more and more stringent requirements are put forward to the performance of marine diesel engine, such as the greater output power, less fuel consumption rate, and at the same time, the engine must conform to the present ever more stringent emission regulations. The cylinder combustion affects the economic performance, the dynamic performance and the main factors for emissions of diesel engines. Because the experimental method of studying the diesel engine cylinder work process demands special equipments, and the experimental condition involves burning, apart from special laboratory can provide the test conditions, most experimental methods are hard to conduct. So using experimental method to study the work of the diesel engine in cylinder has some limitations. Therefore launching a numerical simulation method research on the combustion process of diesel engine has been a hot topic in internal combustion engine industry.
L21/31 marine medium-speed diesel is taken as the research object and KIVA-3V program is used to simulate the cylinder combustion progress in it. To generate the diesel’s grid meshes, the K3PREP generator and ANSYS ICEM-CFD software are used respectively. By comparing the measured pressures and NOx emissions with two calculated results, ICEM-CFD model is chosen for the more reasonable model, meanwhile the accuracy of this model has also proved successful. On this basis, the main emphasis is placed on the influence of four factors including speed, load, fuel injection advance angle and inlet delay angle on how these parameters effect on the cylinder process, dynamic performance and spatial distribution of harmful emissions such as NOx and CO of the diesel engine.
Aimed at NOx emissions limits of the second stage which implemented by IMO in 2011, and that of the upcoming third stage in 2016, this paper adds physical parameters of liquid DME to fuel libery of KIVA-3V program. We chose liquid DME as a substitute for diesel fuel, analysed the influence of DME on L21/31 type of marine medium speed machine NOx emissions. On the basis, reducing the load and delaying the fuel injection advance angle to research how these two parameters effect on the NOx emission value with DME fuel. Then we can forecast whether this type of engine can meet the standard of the third stage NOx emissions after 2016, and provide a theoretical basis for enterprise to retrofit the design of the model in this paper.

Key word KIVA-3V, numerical simulation, Marine medium-speed diesel, combustion process, dymethyl ether (DME)

目 錄
摘 要 I
ABSTRACT III
第1章 緒 論 1
1.1 選題的理論意義及實用價值 1
1.2 數(shù)值模擬的國內外研究現(xiàn)狀與發(fā)展趨勢 2
1.2.1 國外技術發(fā)展情況 2
1.2.2 國內技術發(fā)展情況 4
1.3 KIVA程序的研究現(xiàn)狀及發(fā)展趨勢 6
1.4 本文的主要研究工作 8
1.5 本章小結 8
第2章 柴油機燃燒過程的基本理論 9
2.1 主要控制方程 9
2.1.1 組分方程與連續(xù)方程（質量守恒方程） 10
2.1.2 動量守恒方程 10
2.1.3 能量守恒方程 11
2.1.4 理想狀態(tài)方程 12
2.1.5 化學守恒方程 12
2.2 湍流模型 13
2.2.1 標準k-ε雙方程 13
2.2.2 （RNG）k-ε湍流模型 14
2.2.3 亞網(wǎng)格尺度（SGS）模型 14
2.3 液滴噴霧模型 14
2.4 氮氧化物生成模型 16
2.5 邊界條件 17
2.6 本章小結 18
第3章 L21/31船用中速柴油機缸內過程數(shù)值計算 19
3.1 L21/31船用中速柴油機的主要結構參數(shù) 19
3.2 燃燒室網(wǎng)格的生成 20..