变工况条件对船用二冲程低速柴油机扫气过程的影响

在船用二冲程低速柴油机中,扫气过程的优劣直接关系到发动机的各项特性,在前期研究中主要以扫气口结构为主要研究方向,但发动机循环是一个瞬变的动态过程,因此需要针对扫气过程的不同阶段及不同环境因素开展性能分析,以便在扫气全过程内改善扫气性能.本研究基于扫气流动试验台,通过三维激光粒子测速系统,对不同工况条件下的稳态扫气过程进...     

OP2S柴油机气口参数的多目标优化研究

通过建立GT-Power仿真模型,分析了不同进、排气口高度及宽度对对置活塞二冲程(OP2S)柴油机动力性和换气性能的影响规律。采用多目标优化方法,在不同转速下优化了OP2S柴油机的平均指示压力、扫气效率和捕获率,并综合评价了OP2S柴油机的动力性和换气性能。研究表明,最优进、排气口高度随着转速的增加而增大,并且与固定气口高度相比,采用可变气口高度可使平均指示压力明显提高,说明在OP2S柴油机中采用可变气口高度技术实现可变配气相位对性能的提高具有重要意义。     

利用可变气门相位提高车用发动机性能的研究

应用WAVE整机性能分析软件研究了某汽油机的可变气门相位对发动机性能的影响,提出了优化的进、排气相位.在此基础上,进行了不同进、排气相位策略对发动机动力性、经济性和排放影响的试验研究.研究着重分析在外特性及2 000 r/min负荷特性下采用可变气门相位技术对发动机性能的影响.研究结果表明,采用可变气门相位技术,不但提高了低速扭矩和最大功率,还改善了低速、部分负荷时的燃油经济性.     

二冲程船用柴油机稳态扫气流动特性

设计了一台船用柴油机稳态扫气光学试验装置,用以研究低速二冲程船用柴油机的扫气过程.利用立体粒子图像测速技术对不同参数下的缸内扫气流场进行了研究.结果表明:随着扫气口径向切角的增大,平均涡心位置与气缸轴线的偏离增大,涡流强度有所增强,气流的轴向速度呈现先增大后减小的趋势;随着扫气口开度的减小,涡心附近的轴向速度先有所增大,当扫气口开度降低到25%时,轴向速度大幅度减小,并出现回流现象.为通过流场评估扫气性能,提出了"扫气非均匀性系数".试验发现在扫气口径向切角为15°及20°时扫气性能较好,此外,扫气口开度对扫气性能的影响仅体现在扫气口开度较小时,此时在扫气口附近的轴向速度均匀性差,影响扫气性能.     

二冲程汽油机气体流动及扫气品质的数值计算

利用非稳定流动的理论,建立了曲轴箱边界、气口边界等模型,建成了适用于曲轴箱扫气式二冲程汽油机性能预测和进、排气系统分析的模型,并针对ＡＸ１００型摩托车二冲程汽油机进行了计算和分析。由于该有较好地分析二冲程发动机进排气系统中的压力波动,并考虑了扫气口回流中新鲜充量和复合扫气模型,计算得到的二冲程发动机的扫气品质与试验数据比较是吻合的。通过研究加深了对二冲程汽油机进、排气系统流动规律及其对发对机性能     

基于VGT控制参数的柴油机低速变海拔热平衡试验

进行二级可调增压柴油机热平衡性能研究,有助于解决高海拔发动机开锅问题,提高热效率。利用自主设计的柴油机高海拔热平衡试验系统,进行不同模拟海拔(0、3 500、5 500 m)基于可变截面涡轮增压器(VGT)控制参数的二级可调增压柴油机低速全负荷热平衡试验,全面分析了变海拔条件下VGT控制参数对整机低速热平衡性能影响的机理与规律,优化标定了不同海拔下柴油机低速最佳VGT叶片开度。结果表明:随VGT叶片开度增大,发动机低速工况下热负荷升高,表现形式为涡前排温升高、缸内最高燃烧温度上升,但缸内最大燃烧压力呈下降趋势,0 m、VGT开度小于50%时,缸内最高燃烧压力大于17 MPa,在0、3 500、5 500 m海拔,VGT开度分别大于70%、50%、30%时,缸内最高燃烧温度超过2 200.0℃。随VGT叶片开度增大,柴油机有效功率、排气带走热量及其占比升高,冷却液带走热量、余项损失及其占比呈下降趋势,5 500 m海拔下,VGT叶片开度每增大10%,柴油机热效率降低3.1%。综合考虑VGT控制参数对缸内最高燃烧温度、缸内最大燃烧压力及热效率的影响,0、3 500、5 500 m柴油机低速工况最佳VGT叶片开度应分别为50%、20%、20%。     

船用低速柴油机扫气口结构对涡流比影响数值模拟与试验研究

船用二冲程柴油机扫气过程中的缸内流场直接影响着燃油的雾化情况,进而也对燃烧过程与排放水平有所影响,涡流比是评价缸内流场湍流强度的一项重要指标。本文首先用数值模拟的方法对某型二冲程船用柴油机进行建模,计算得到不同扫气口结构下的扫气过程的涡流比数据。随后,参考相关测试方法,结合相似准则,设计并进行了扫气口稳流试验。试验结果表明,试验能有效评估不同结构扫气口产生缸内流场涡流的能力,且试验结果与数值模拟结果在趋势上符合程度较好。     

对置活塞二冲程柴油机扫气系统优化方法研究

分析了对置二冲程柴油机扫气系统参数对发动机工作过程特征参数的影响规律,分别提出了以扫气效率为优化目标和以平均指示压力(IMEP)为优化目标的优化函数。结合正交优化方法,优化计算并对比分析不同优化函数的优缺点。研究结果表明:IMEP可有效地兼顾扫气系统参数对扫气效率与发动机指示热效率的影响,更适合作为对置二冲程柴油机扫气系统优化目标。优化结果显示:扫气口宽度比为0.85,排气口宽度比为0.6,扫气口高度为22mm,排气口高度为29mm,扫气口倾角为10°时发动机IMEP达到最优值。     

基于排气VVT的直喷汽油发动机性能试验研究

在一台自然吸气直喷汽油发动机上进行运行工况内的进、排气可变气门正时(VVT)相位扫点试验,根据不同排气VVT相位下的发动机动力性和燃油经济性,结合进气流量、最高燃烧温度、指示热效率和泵气损失等因素,分析了发动机性能变化的原因。研究结果表明,外特性工况排气VVT推迟15°曲轴转角时,进气量增加,动力性提高;继续推迟排气VVT相位,泵气损失增加,动力性降低。在转速低于2 400r/min的中、高负荷区域,开启排气VVT使得指示热效率增大,泵气损失减少,发动机油耗降低;在排气VVT相位大于-15°曲轴转角、转速高于2 800r/min的中、高负荷区域,发动机经济性变差。     

发动机换气系统三维瞬态数值模拟应用研究

通过对 K10 0二冲程汽油机倒拖工况下扫排气道 -缸内系统流场的三维瞬态数值模拟 ,发现整个扫气阶段的缸内流场是由三维回流组成的。主扫气口径向平面的切向倾斜角偏小 ,径向汇聚角偏大 ,产生了明显的短路损失 ,并在缸盖顶局部产生了反向流动形成的“死角”。为此 ,调整了主扫气口的扫气角 ,其它参数均不改变。计算结果表明 :缸内分层扫气十分清晰 ,短路损失及死角明显减少 ,反向流动被消除。但缸内回流 -环涡的流动结构基本不变     

JK80VNT增压器的开发研究

可变喷嘴涡轮调节技术是改善增压柴油机低速性能、降低柴油机排放的有效措施。本文对JK80VNT增压器进行了设计计算，将所设计的转叶式可变喷嘴涡轮增压器进行了涡轮性能试验，试验结果表明它能够有效地调节涡轮特性。并进行了可变喷嘴涡轮增压器与CA6106柴油机的匹配试验，将其结果与带放气阀增压器的试验结果进行了比较，结果表明CA6106柴油机高速油耗和整个外特性烟度都得到明显的改善。     

VVT和TCI技术提高发动机热效率的研究

本文针对一款汽油发动机,通过试验的方法,分别对VVT(可变气门正时)和TCI(涡轮增压中冷)技术提高其热效率进行了对比分析。试验结果表明,VVT和TCI都可以有效的提高发动机热效率,但在不同的运行工况下,其效果不同。同时,本文研究了VVT联合TCI技术提高汽油机热效率的效果及其影响因素。对于涡轮增压发动机在部分负荷下燃油耗率较高,通过一维模拟计算,分析了发动机使用涡轮增压后,热效率降低的影响因素,初步提出改善涡轮增压发动机部分负荷下热效率的思路。     

二冲程汽油机扫气过程多维数值模拟及扫气系统优化设计

本文采用多维数值模拟方法对二冲程发动机的扫气过程进行优化。对原型机(小型HS-510航空发动机)的扫气过程数值模拟发现：在缸内存在环流和涡流。环流在贴近气缸附近较强，可以将废气排出气缸；而在气缸中部较弱，难以将废气彻底排出。涡流的存在则降低了发动机的扫气效率。原型机的扫气过程同理想的扫气过程相比有相当大的差距。在原型机扫气过程数值模拟的基础上，改进扫气系统设计，将扫气口由原来的两个增加到五个。对改型机数值模拟发现缸内没有形成涡流。计算和试验结果表明发动机的扫气效率得到了提高，且发动机的功率提高11％。     

Development of a hybrid pneumatic-power vehicle

Many complex technologies have been developed and applied to improve the energy efficiency and exhaust emission of an engine under different driving conditions. The overall thermal efficiency of an internal-combustion engine, however, can be maintained at only about 20–30%, with aggravated problems in the design and development, such as overall difficulty, excessive time consumption or excessively high cost. For electric cars, there is still no major technological breakthrough for the rapid recharging of a large capacity battery and detection of remaining power in it. Although all currently available hybrid-power engines are able to lower the amount of exhaust emissions and the fuel consumption of the engine, they are still unable to achieve a stable and optimal running condition immediately after ignition; hence the engine's thermal-efficiency remains low. To solve the aforementioned problems, an innovative concept – a hybrid pneumatic power-system (HPPS), which stores “flow work” instead of storing electrochemical energy of the battery – is introduced. This innovative power system not only ensures that the internal-combustion ensures optimally but also recycles the exhaust flow to propel the vehicle. The optimization of the internal-combustion and recycling of the exhaust energy can increase the vehicle's efficiency from an original 15% to 33%, an overall increase of 18%.     

ABB增压系统应对未来发展措施

介绍了ABB公司针对大功率发动机的发展需求,不断发展其增压器技术的情况,具体体现在以下几方面:在单级高压比A100-L系列增压器基础上,进一步扩大容积流量以满足更大功率的覆盖范围;用于低速机的新一代A200-L系列增压器,通过高压比调节方式可替代可变几何涡轮优化部分负荷;ABB两级增压系统的配置及两级增压系统在柴油机和气体机应用的典型案例;分析了两级增压系统潜能,两级增压系统结合可变气门正时技术,可显著降低NOx排放和燃油效率,提高发动机瞬态特性。     

Reduction of emissions in a biodiesel‐fueled compression ignition engine using exhaust gas recirculation and selective catalytic reduction techniques

This paper analyzes the emissions of a single‐cylinder diesel engine fueled with biodiesel, using selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) techniques. The aim of this paper is to compare both EGR and SCR techniques, which were studied under different brake powers. Grape seed biodiesel was used as a test fuel. Experiments were performed by both techniques at different loads and rates to find out the performance change in the engine and the change in the emission rates using both the techniques. Then the observations from both the techniques were compared, concluding that both the techniques show a sufficient reduction in NOx. Using the abovementioned techniques, a reduction in hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO₂), nitrogen oxides (NOx), and smoke was observed. The EGR technique is more suitable for low‐load engine vehicles, as it affects the efficiency of the engine with an increase in the fuel consumption, whereas the SCR technique is suitable for high‐load engines, which do not affect the efficiency of the engine with a decrease in the fuel consumption.     

基于Simulink在不同排气背压下VGT增压系统控制策略

为了改善柴油机在高背压环境条件下进排气流速降低、涡前排温、缸内最高燃烧压力和油耗升高等问题,采用Simulink软件,基于柴油机数学模型建立某型号柴油机零维仿真模型和可变截面涡轮(variable geometry turbine,VGT)增压系统仿真模型,并根据试验结果对模型进行校核.利用所建立的仿真模型模拟在不同排...     

在汽油机上实施HCCI的技术策略

均质混合气压燃(HCCI)燃烧方式，是一种克服常规柴油机和汽油机缺点、集常规汽油机和柴油机优点于一体的新概念燃烧。本文分析了汽油机实施HCCI的可行性，介绍了HCCI发动机实用化所面临的问题，提出了双工作模式的折衷方案：在中低负荷工况实施HCCI，而在大负荷工况和冷起动工况恢复常规发动机工作方式。推荐可变压缩比(VCR)方案、可变废气再循环率(EGR)方案、可变排气门关闭时刻方案，以及废气再循环滚流分层充气方案等。为尽快在汽油机上实施HCCI燃烧方式指出了技术方向。     

Effect of Exhaust Gas Recirculation (EGR) on performance,emissions, deposits and durability of a constant speed compression ignition engine

To meet stringent vehicular exhaust emission norms worldwide, several exhaust pre-treatment and post-treatment techniques have been employed in modern engines. Exhaust Gas Recirculation (EGR) is a pre-treatment technique, which is being used widely to reduce and control the oxides of nitrogen (NO_x) emission from diesel engines. EGR controls the NO_x because it lowers oxygen concentration and flame temperature of the working fluid in the combustion chamber. However, the use of EGR leads to a trade-off in terms of soot emissions. Higher soot generated by EGR leads to long-term usage problems inside the engines such as higher carbon deposits, lubricating oil degradation and enhanced engine wear. Present experimental study has been carried out to investigate the effect of EGR on soot deposits, and wear of vital engine parts, especially piston rings, apart from performance and emissions in a two cylinder, air cooled, constant speed direct injection diesel engine, which is typically used in agricultural farm machinery and decentralized captive power generation. Such engines are normally not operated with EGR. The experiments were carried out to experimentally evaluate the performance and emissions for different EGR rates of the engine. Emissions of hydrocarbons (HC), NO_x, carbon monoxide (CO), exhaust gas temperature, and smoke opacity of the exhaust gas etc. were measured. Performance parameters such as thermal efficiency, brake specific fuel consumption (BSFC) were calculated. Reduction in NO_x and exhaust gas temperature were observed but emissions of particulate matter (PM), HC, and CO were found to have increased with usage of EGR. The engine was operated for 96 h in normal running conditions and the deposits on vital engine parts were assessed. The engine was again operated for 96 h with EGR and similar observations were recorded. Higher carbon deposits were observed on the engine parts operating with EGR. Higher wear of piston rings was also observed for engine operated with EGR.     

汽油机燃用汽油/二甲氧基甲烷混合燃料的性能与排放研究

在丰田8A型汽油机上开展了汽油／二甲氧基甲烷（DMM）含氧混合燃料的性能与排放特性研究,得到了不同节气门开度、转速和负荷下的发动机性能和排放参数,为在汽油机上使用含氧燃料提供了试验依据。研究结果表明：在相同平均有效压力下混合燃料的燃油消耗率有所增加,但折算成当量汽油的燃油消耗率下降,热效率提高。CO和HC排放随混舍燃料中含氧量的增加而降低,但NOx排放变化不大。