该论文已在芬兰赫尔辛基举行的第28届CIMAC大会上发表。论文的版权归CIMAC所有。Caterpillar develops medium speed Dual fuel engines for marine applications in the power range from 2.400 to 15.440 kW. Due to new emission legislation like IMO3 in MARPOL Annex VI, customers are looking for alternative solutions for propulsion and power generation, which are able to operate like the well- known Diesel engines. The M46DF and M34DF Caterpillar Dual Fuel engines – also offered under the MaK trademark – are able to burn Natural gas ( LNG) and liquid fuels like Diesel, HFO or Crude oil. IMO3 emission limits are fulfilled with in gas operation and for liquid fuels an exhaust gas aftertreatment solution (SCR) is offered. Transient response is a key requirement for a lot of marine applications and these are not only emergency gensets with three step block loading. Supply vessels operate in a majority of time on low stand by power and require fast ramp up to high level of thrust. Even with Diesel engines this demands additional features like air injection into the charge air manifold. Gas engines are known to be slow in load response. This is mainly caused by air fuel ratio control depending on turbocharger inertia. Gas ignition is limited by upper and lower air fuel ratio limit, which leads to reduced rates in fuel ramp up. A faster speed governor would overfuel the combustion chamber. A Diesel engine would react with black smoke, but a gas engine would break down due to a mixture which is too rich. The M46DF and M34DF engines are equipped with a superior engine control. All controls are handled in a MIMOcontrol architecture. One speed governor controls three fuel systems (main Diesel fuel, ignition Diesel fuel and Gas admission). Due to this concept the load acceptance of Dual Fuel is on a level, which may be called “It runs like a Diesel”. This paper describes the engine concept and will show engine test results. A second aspect is the low load operation in Gas mode. Without additional technologies common gas engines run with a very lean mixture and emit increased amount of hydrocarbons. New technologies have been developed to allow unlimited engine operation with gas combustion. This paper describes the engine concept and will show engine test results of an IMO3- Dual Fuel engine optimized for marine applications with class leading load acceptance and low load operation.

该论文已在芬兰赫尔辛基举行的第28届CIMAC大会上发表。论文的版权归CIMAC所有。Demand of dual fuel of liquid and gas is increased in a business of the standby gas turbine generator set. In this paper, technology in Niigata Power Systems regarding to dual fueled gas turbine system will be introduced. Following two main features will be described. The first one is the general description of the gas turbine package. The package mainly includes in a generator, a reduction gear, gas turbines and dual fuel supply units. The gas turbine components are also introduced. Especially, the configurations of the dual fuel injector and the combustor are focused. The combustor is single can type having simple configurations. The liquid fuel injector has both of a pressure atomizer for the pilot and an air blast atomizer for the main fuel injection. The gas injector with several spokes is inserted from over the liquid injector and the spokes are settled in just upstream of the swirler of the air blast atomizer. So, the flow pattern is not influenced by the fuel change. As the second one, engine operating results are shown. The exhaust gas emissions are compared with liquid and gas fuel. Emissions of carbon dioxide, nitrogen oxide and smoke are decreased by gas fuel use. Smoke emission is decreased 80 % from liquid to gas. Fuel control logics and trend data are focused in when fuel changes between liquid and gas. The fuel changes within extremely short time for overshooting recovery and with low fluctuations of engine speed are realized by fully electronic fuel control. It can choose both types of the fuels for engine start up. The trend data show that it can be quickly started up within 40 seconds in case of both fuels of liquid and gas. Here, purge clank time isn’t included in case of gas fuel choice. Finally, load dumping while fuel switching is discussed. Full load dumping during fuel changing is realized with low fluctuations of engine speed. And the overshooting recovery is very short time.

该论文已在芬兰赫尔辛基举行的第28届CIMAC大会上发表。论文的版权归CIMAC所有。Yanmar has developed two types of marine gas engines which converted from proven marine diesel engine. These are a pure gas engines and dual fuel engines. A pure gas engine was developed as an auxiliary power supply, or the propulsion power of electric propulsion ship. The environmental impact material exhausted from this engine is few and thermal efficiency is high. A dual fuel engine was developed as the direct drive main propulsion engine. The feature of this engine is a high-power density and a high acceleration performance. A further reduction of nitrogen oxidation (NOx), sulfur oxidation (SOx) and particulate matter (PM) from an exhaust gas is international key policy problem from the viewpoints of the environmental protection. Green house gas including carbon dioxide emission control is also great problem from the view point of the global warming mitigation. The emission regulation of nitrogen oxides and sulfur oxides has been introduced to marine environment by IMO/MARPOL international convention for the marine environment in 2005, and, in addition, it is strengthened with the tier 2 restriction (2011) and the tier 3 restriction (2016) afterwards. Carbon content ratio in natural gas is less than that in other fossil fuels, and it contains sulfur not at all or little. That is why the natural gas can greatly reduce not only NOx, SOx, and PM but also the amounts of the CO2 exhaust. Therefore, installing natural gas engine in the ship would be effective to reduce environmental impact material from the ship. The air and fuel are mixed before the mixture is inhaled into, which is ignited in the gas engine. Because a homogeneous air-fuel mixture can control the highest combustion temperature by the density of the air-fuel mixture, the generation of the nitrogen oxide can be controlled. When the gas engine changes the output, a short time lag is necessary for the making changing of the air-fuel mixture. In the worst case, the engine runs into the knocking or missfire because the density of the air-fuel mixture significantly changes during this term. As for above marine gas engine mentioned before, the development technology of mixture concentration control during the load changing has been installed In this paper, we describe the mixture concentration control technology, and test results done by the new gas engines.

该论文已在芬兰赫尔辛基举行的第28届CIMAC大会上发表。论文的版权归CIMAC所有。Off-Highway applications such as locomotives, mining trucks, inland waterway carriers, ferries or tug-boats are operated several thousand hours each year and require robust and cost efficient internal combustion engines. Today most of these applications are powered by diesel engines. But tightened emission regulations and limited oil reserves lead to more complex engines and higher costs. This leads to the question: are compressed (CNG) or liquefied (LNG) natural gas an alternative to diesel fuel? Looking at availability, infrastructure, costs and engine-out-emissions good arguments can be found to switch from Diesel to Gas in the future. The motivation is clear but the hurdles are high: availability of gas equipment (fuelling equipment, storage-tanks, engines), operational experience with gas (fuelling, servicing) or clear regulations. Within this paper we will provide a first more deep insight into the development of a 2 MW gas engine based on Series 4000 Diesel and Gas. It will be explained why this product is a promising concept for marine applications in particular. Design details like gas supply and injection System will be presented. Safety issues will be discussed and how these are designed on the engine. Results from the test bench will demonstrate the diesel-like performance while lowering the emissions. Finally there are a lot of challanges beside the engine which are ship design and gas fuelling. Having solved this, gas engines will have a great future in the market.

通过一台改装的6 缸增压直喷式柴油机，调整喷油正时实现燃烧相位的调节，在不同燃烧相位下开展了宽馏程燃油低温燃烧和排放特性的试验．结果表明：随初馏点的降低，燃料中汽油轻质馏分增加，燃料十六烷值降低，滞燃期延长，预混合气量增加，NOx 和碳烟排放均得到有效改善，但初馏点过低会导致HC 和CO 排放增加．随CA 50 的延后，碳烟和HC 排放增加，CO 和NOx排放降低．燃烧相位和宽馏程燃油特性相结合，可以在保证指示热效率的前提下，实现柴油机燃烧和排放的优化，达到同时降低NOx和碳烟排放的目的．

通过一台共轨柴油机，基于正庚烷/甲苯/正己烯混合物简化动力学机理耦合三维CFD 数值模型，模拟不同进气组分(O2、H2 和CO2)耦合喷油时刻对发动机工作过程的影响机理．研究表明：不同进气组分下，随喷油时刻提前，缸内活性自由基(OH、O)质量分数及其分布区域增大，NO 生成量增多．但随喷油时刻过度提前，燃烧始点反而推迟，燃烧放热速率、缸内燃烧压力与温度峰值降低，NO 也相应减少；相比其他进气组分，进气掺O2时缸内O自由基质量分数增大，碳烟(Soot)降低且喷油时刻对其影响较小；进气掺H2 时，缸内燃烧压力和温度峰值最高，OH 自由基质量分数及分布区域最大，Soot 随喷油定时提前大幅降低；进气掺CO2 时，缸内燃烧压力与温度峰值最低，OH 和O活性自由基最少，当喷油时刻提前超过24° CA BTDC时，燃油逐渐喷射到压缩余隙容积形成局部过浓区，C2H2和多环芳香烃芘(A4)生成量增多，Soot排放随喷油定时进一步提前明显升高．

利用详细化学动力学在绝热均质定容条件下对正丁醇燃烧过程进行了数值模拟，并通过非平衡态热力学熵平衡方程计算了燃烧过程的㶲损失．结果表明： 㶲损失率曲线主要有两个峰值，第1 个峰值由正丁醇转变为小分子燃料的反应(阶段1)和H2O2 loop 及支撑反应(阶段2)构成；第2 个峰值由CO、H 氧化为最终产物反应(阶段3)构成．提高燃烧初始温度或当量比，反应温度上升，阶段1 中高温反应路径取代低温反应路径，使㶲损失降低，阶段2 和阶段3 中主要反应㶲损失持续时间缩短，使㶲损失降低；然而燃烧温度过高致使离解反应发生，导致不完全燃烧．增加燃烧初始压力或降低氧体积分数都可抑制离解反应，减少不完全燃烧．若使用进气加热、增压、稀燃、提高压缩比和废气再循环等发动机技术，可改变燃烧初始条件，使㶲总损失从30.7% 减少至18.7% ．

对带有叶片前缘混合掠的跨音速离心压气机流场进行了数值模拟研究．结果表明：叶片前缘混合前掠能够有效提高压气机流通能力，拓展失速裕度，推迟压气机失稳，使压气机工作裕度得到明显提升，而叶片前缘混合后掠则减少失速裕度，使压气机工作裕度下降，易发生失稳；叶片前缘混合前掠可以有效减弱叶轮通道内部激波强度，而前缘混合后掠会使通道内激波强度增强，造成一定的激波损失；虽然二者均可以改善通道下游分流叶片两侧低能流团的分布情况，但叶片前缘混合前掠改善作用更好；叶片前缘混合掠对压气机内部二次流的影响主要集中在叶片前缘附近，对叶轮出口附近二次流影响不大．通过对不同前缘混合掠结果对比分析，叶片前缘混合前掠在提高压气机流通能力、工作裕度以及改善内部气流流动情况具有明显的优势．

气门间隙异常是柴油机常见机械故障之一，对其进行准确的诊断对提高柴油机的使用寿命具有积极的作用．针对柴油机气门间隙异常的问题，在某直列6 缸柴油机上模拟了不同气门故障，提出了基于双谱估计、图像处理以及分形理论相结合的故障诊断方法．该方法首先利用双谱估计对非线性、非高斯信号的敏感性质，分析了不同故障状态下振动信号中非高斯成分及二次相位耦合特性，然后通过图像处理技术将双谱图表示为以像素位置及对应颜色强度构成的三维空间曲面，最后利用分形理论提取该曲面的分形盒维数作为故障特征．结果表明：不同状态下柴油机振动信号的双谱及其图像分形维数明显可分，正常状态下的双谱峰值分布最为复杂、分形维数最大，故障状态下的分形维数分别处在不同的范围．因此，以振动信号的分形维数作为特征值可实现柴油机气门故障诊断．

利用高速摄像的方法，在狭缝间距为2 mm 的圆盘状微型定容燃烧装置中考察了常温常压、当量比φ为1.0～1.6 静止丙烷/空气预混气中心点火后向外传播的火焰传播特性．结果表明：微型定容燃烧腔内形成的火焰面有光滑、褶皱和断裂3 种形态；光滑火焰面的火焰传播速度低于常规尺度下的火焰传播速度；火焰传播速度随着当量比的增加先增大后减小；在点火能量影响范围外，火焰传播速度随半径增大而减小；随当量比的增加火焰锋面容易出现褶皱和断裂现象．