某重型柴油机燃烧室形状研究

本文针对某重型柴油机,利用燃烧仿真软件FIRE建立了三维数值模型,根据试验数据完成数值模型标定,在原机传统ω型燃烧室形状基础上,从燃烧理论出发优化设计新的燃烧室型线方案,提出了阶梯式燃烧室方案,并完成试验验证。经试验验证,阶梯式燃烧室与传统ω型燃烧室相比,柴油机外特性油耗比降低,滤纸烟度也有较大改善,与仿真预测结果基本一致。为通过优化燃烧系统达到改善柴油机经济性、动力性及排放指标的研究提供参考。     

直喷式柴油机ω型燃烧室的改进试验研究

通过对三种不同结构燃烧室的试验研究，探讨其对YC4108Q型柴油机性能及排放的影响。结果表明改进ω型燃烧室既满足了动力性和经济性的要求，同时在控制排气烟度和降低排放方面取得了良好的效果。     

柴油机燃烧系统多参数多目标优化研究

针对直喷柴油机燃烧系统多参数间存在的非线性现象,采用响应面法对其进行多参数多目标优化研究。该研究以双ω燃烧室结构、喷油夹角、供油始点、涡流比为因子,以燃烧指示功率、NO比排放和碳烟比排放为评价指标。首先利用正交设计,利用方差和极差分析筛选了燃烧室结构和喷油夹角优化方案;其次对供油始点和涡流比进行了多参数二次响应面全局寻优研究,得到2种满足功率和排放的优化方案并与原机方案进行性能对比分析。结果表明,喷油夹角为130°的1号燃烧室具有较高燃烧指示功率与排放性能。涡流比在1.6附近时燃烧指示功率取得最大值,且小涡流比对NO排放改善显著。     

ω型燃烧室对柴油机燃烧过程影响的数值模拟研究

结合某增压发动机燃烧系统开发,应用FIRE软件对新设计的压缩比为15的3种ω型燃烧室进行了建模和仿真计算。对比分析了15压缩比下,不同燃烧室廓形方案对缸内燃烧过程的影响。结果表明:压缩比和口径比相同的条件下,径深比越小的燃烧室燃烧质量较好;缩口、小径深比的燃烧室具有较合理的涡流分布,较大的挤流强度,有利于混合气的形成,加速了扩散燃烧过程,放热率快而集中。     

测力仪双自由度振动模式的研究

<正> 我院研究了具有普遍性意义的测力仪双自由度振动模式,采用复变函数方法求解了与振动模式对应的微分方程组,给出了频率响应特性ψ(ω)、幅频特性|ψ(ω)|和相频特性φ(ω)     

某型燃机燃烧室的数值模拟

燃料喷嘴双级径向旋流器在燃烧室内形成稳定的回流漩涡结构,有助于燃烧室火焰稳定和提高燃烧效率。文中建立了计算模型,利用CFX软件进行燃烧室的燃烧模拟,研究了燃烧室中流场分布、NO含量分布、温度场分布、燃料分布。模拟计算表明,此燃烧室具有较好的气动特性、稳燃性能与冷却性能,能够在额定工况下长时间稳定工作。     

利勃海尔D92系列柴油机核技术、经济效能的对比分析

辽宁-利勃海尔柴油机有限公司(LLD)和瑞士利勃海尔合资、引进的D92系列柴油机是瑞士利勃海尔工程机械股份公司于九十年代在其D90系列、D91系列柴油机基础上,开发出来的四冲程直喷水冷增压式和水冷直喷增压中冷式柴油发动机.采用更加完善的燃烧系统和供油系统,强化了废气增压系统和废气净化技术,燃烧室为深ω形缩口燃烧室,燃油喷射压力提高到22.1MPa,喷油采用低惯量、小孔径、六孔喷油咀,喷射压力提高到196kPa.     

发动机拉缸的原因及排除

斯太尔WD615系列发动机采用干式气缸套。2mm厚的薄壁气缸套可以轻易地从缸孔中取出或者放入。活塞为铝铸件,顶部有偏置的"ω"形烧燃室及避阀坑,第一道环槽镶有隔热圈,活塞销孔向曲轴旋转的方向偏1mm,顶岸有18道细槽,以防咬伤。裙部涂覆2～3微米厚的石墨层,以改善磨合。由于该机活塞顶部有"ω"型燃烧室,不但要承受机械负荷,而     

基于温度场分析的S195柴油机活塞结构改进

S195柴油机活塞采用分隔式燃烧室,其流动损失大,燃油消耗率高,启动性能差。文章将S195活塞顶部结构改进为浅ω形,并采用有限元软件ANSYS对改进之前与之后的活塞温度场进行分析,分析结果表明,改进后的活塞所承受的热负荷减小可延长活塞使用寿命。     

防爆柴油机活塞的热载荷响应特性研究

为提升矿用防爆柴油机的换热能力,提出水冷代替油冷方案,对燃烧室内活塞的热载荷响应特性进行了研究与分析.基于CFD方法,建立活塞冷却腔内的气液两相流模型,选用SSTk-ω湍流模型,结合VOF模型和Level Set模型得出不同曲轴转角下的液相比例和对流换热系数变化规律,分析了冷却腔结构对传热效果的影响.构建活塞热机耦合模...     

Performance and emission characteristics of a low heat rejection spark ignited engine fuelled with E20

In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (Al₂O₃) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and compared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A maximum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved.

     

普通机床加工发动机缸盖球形燃烧室的工艺试验

发动机缸盖是发动机的关键零部件.发动机缸盖的燃烧室容积,直接影响到发动机的工作性能,所以在发动机缸盖制造过程中,最终必须保证发动机缸盖燃烧室的形状、表面粗糙度、尺寸精度、容积等一系列参数,从而保证发动机总机性能.     

点燃式天然气发动机燃烧室结构优化的仿真与试验研究

利用三维数值仿真的方法,对带有浴盆形燃烧室的天然气发动机缸内流动和燃烧特性进行分析,提出了两种燃烧室结构优化设计方案,试验对比了采用原燃烧室和挤气喷射燃烧室时的发动机性能。结果表明:在不改变压缩比情况下,通过改变活塞头部凸起形状和位置,能够实现浴盆形燃烧室内的挤流与滚流有效耦合;控制点火时刻的火花塞附近气体流速,能提高缸内平均湍动能,加大快速燃烧期内火焰前封面的面积,改善燃烧质量。发动机采用优化的2号挤气喷射燃烧室,能够明显加快发动机燃烧进程,提高发动机的动力性和经济性,发动机功率从75kW提高到78.7kW,最低比气耗降低4.4%,HC和CO排放略有降低。     

A study on the unsteady temperature field of combustion chamber wall in a turbocharged gasoline engine

To design and develop a turbocharged engine, it is necessary that a lot of studies should be done to find the chrracteristics of engine performance and thermal flow. To accomplish this purpose, turbocharger equipped to a naturally aspirated gasoline engine was utilized. A thin-film type temperature probe was made and installed onto the combustion chamber wall to measure unsteady temperature. The unsteady heat flux at combustion chamber wall was evaluated by one dimensional unsteady conduction equation.     

Improving the ecological indices of a hydrogen diesel engine with direct gaseous hydrogen injection

A detailed survey of the operating process and formation of nitrogen oxides in the combustion chamber of a hydrogenous diesel has been carried out in three-dimensional space using a mathematical model verified by experimental data. The specific features of the thermophysical processes in the combustion chamber of the hydrogen diesel engine have been specified, providing the applicable ecological and efficient indices of a stationary hydrogen diesel engine.     

Effect of piston bowl shape on the in-cylinder flow characteristics of IC engines

Numerical simulation of the in-cylinder flow for internal combustion (IC) engine with different bowl shapes has been performed. The LES models are applied to a piston-cylinder assembly with a stationary valve and a harmonically moving piston. Gas motion inside the engine cylinder determines the thermal efficiency of an IC engine, and combustion chamber geometry affects the performance of the IC engine. Comparison of the flow characteristics inside the engine cylinder equipped with different piston geometries shows that the squish flow affects the turbulence generation process near the top dead center during compression stroke. The A-type combustion chamber with reentrant shape is shown to have higher radial velocity and turbulence intensity in the piston bowl compared with other types. Results of these simulations aid in the improved understanding of the effect of intake and compression process of piston geometry on the in-cylinder flow. The detailed flow characteristics inside the in-cylinder for different piston bowl shapes can offer basic guidelines to improve the combustion process.     

Effect of water induction on the performance and exhaust emissions in a diesel engine (II)

This study was to investigate the effects of water induction through the air intake system on the characteristics of combustion and exhaust emissions in an IDI diesel engine. The fuel injection timing was also controlled to investigate a method for the simultaneous reduction of smoke and NOx when water was injected into the combustion chamber. The formation of NOx was significantly suppressed by decreasing the gas peak temperature during the initial combustion process because the water played a role as a heat sink during evaporating in the combustion chamber, while the smoke was slightly increased with increased water amount. Also, NOx emission was significantly decreased with increase in water amount. A simultaneous reduction in smoke and NOx emissions was obtained when water was injected into the combustion chamber by retarding more 2°CA of the fuel injection timing than without water injection.     

A study on the characteristics of combustion variations of compression ignition engine

This paper describes the results of a study of the variation of combustion characteristics in a precombusion chamber type water-cooled diesel engine. Statiscal analysis on cycle-by-cycle variation of combustion characteristics such as rate of pressure rise, heat release rate, and mass burning rate from combustion pressure-crank angle data of one thousand cycles were made under several operating conditions. The influence of engine speed and coolant temperature upon maximum frequency of combustion characteristics are discussed also.     

隔板应用于发动机燃烧室不稳定燃烧抑制中的二维数值计算分析

针对某水下航行器的燃烧室,用有限元的方法对隔板抑制燃烧不稳定性的声学机理进行了初步研究。利用ANSYS软件数值计算了隔板长度变化以及隔板数目变化时,对应的燃烧室声模态,并比较了它们的变化对燃烧室声模态造成的影响。计算表明:隔板抑制燃烧不稳定主要是通过对燃烧室腔体的声学共振频率进行平移,避开了与其相耦合的频率,从而达到抑制燃烧不稳定的目的。同时随着隔板长度的增加,靠近隔板处的声腔部分的切向声模态轴向化会逐步加剧,这样就可以得到更好的抑制作用。     

直喷式柴油机燃烧系统的均匀试验设计研究

在SD195柴油机涡流室改直喷过程中,采用了均匀设计试验法优化柴油机性能,用均匀设计表安排了采用浅W燃烧系统柴油机的燃烧室尺寸、油嘴喷孔直径和油嘴伸出量对性能影响的试验,经回归分析得到了最佳的试验结果。用单因素试验法分析了诸因素对性能的影响规律,发现燃烧室尺寸对性能有重大影响,在考虑交互作用情况下,油嘴孔径、伸出量的参数选择时要综合考虑燃烧室尺寸,试验最终获得良好效果。同时证明了均匀设计法的有效性,表明均匀设计试验法是安排多水平试验的良好方法。