电喷发动机燃源性沉积物与汽油清净剂的研究

电喷发动机早期故障主要因汽油沉积物引起.本文综合前人研究成果指出,我国汽车燃用以催化裂化为主的重整调合汽油,其电喷发动机早期严重沉积物故障主要发生在喷油器和进气阀处,在汽油中添加清净剂是控制和清除此类沉积物最有效方法.但若清净剂使用不当,将引发严重的燃烧室积碳.本文提出了应根据燃油成分正确使用汽油清净剂.     

热分解率(TGA)评定汽油清净剂控制发动机沉积物的理论和实践

阐述了依据清净剂及其加剂汽油的热稳定性预测其控制发动机沉积物的可行性.用热分解率( TGA)从购自汽车售后市场8款清净剂中挑选2款特定热稳定性的清净剂,分别按规定浓度添加在2台试验车的汽油中进行1000 km道路试验.结果表明,这2款清净剂控制CCD、IVD及PFID的实际效能与其由TGA热稳定性预测的清净效能完全吻合...     

燃烧室沉积物对火花点火发动机碳氢排放的影响

为了弄清燃烧室沉积物对发动机排气碳氢的影响，使用一台实验用单缸火花点火发动机来形成燃烧室沉积物。在燃烧室沉积物存在的条件下，开展了不同工况下碳氢排放的实验研究，分析了燃烧室沉积物对发动机动力性和燃油经济性的影响。实验结果表明：当发动机运行一段时间后，其燃烧室表面沉积物将达到一稳定平衡厚度，此时排气碳氢浓度随转速的升高、冷却水温的增加以及点火推迟而降低。在本实验各类工况下，沉积物的存在将使发动机排气碳氢浓度增加２０％～３０％。同时沉积物的存在将使发动机的功率和燃油经济性有所提高（功率增加１．１％～１．６％，燃油经济性提高２．７％～３．０％），此现象被认为主要是因沉积物的隔热作用，而不是压缩比的增加所致。     

燃油添加剂在汽车内燃机排气净化中的应用研究

在汽油中添加清净剂可以防止汽油机燃料系统及进气系统沉积物的形成 ,减少排放污染 ,降低燃油消耗。在柴油中添加消烟助燃剂能有效减少柴油机碳烟等污染物的生成。本文综述了清净剂和消烟助燃剂的应用研究发展过程 ,分析了其效果和作用机理 ,提出了清净剂和消烟助燃剂的研究重点和发展方向。     

PFI发动机进气门沉积物形成机理分析

综述了电啧汽油发动机进气门沉积物对发动机性能的影响，分析了影响沉积物形成的主要因素。结果表明，在影响进气门沉积物的形成的各因素中，进气门表面温度是最重要的外因，汽油及其添加剂和机油组成和物理化学性质的作用也至关重要，同时它们也是沉积物成分的来源。除此之外，发动机参数与运行工况对进气门沉积物的生成也有不同程度的影响。     

火花点火发动机燃烧室沉积物未燃碳氢排放的理论与实验研究

本从实验和理论两个方面来系统地研究火花点火式发动机燃烧室沉积物处未燃碳氢排放浓度随冷却水温，发动机转速，节气门开度和点火提前角等运转参数的变化规律，对发动机缸内沉积物未燃碳氢的生成过程和缸内，排气系统中未燃碳氢的氧化过程进行了模拟，对缸内沉积物未燃碳氢生成过程进行了详细的研究，找出了影响燃烧室沉积物处未燃碳室氢生成量的关键因素。此外还分析了燃烧室中沉积对发动机性能的影响。     

点燃式发动机燃烧室沉积物的研究综述

本文系统综述了点燃式发动机燃烧室表面沉积物的形成机理、组成以及沉积物对燃料等烷值的要求，沉积物对燃油经济性和未燃碳氢排放的影响，指出了燃烧室表面沉积物对发动机性能的有利于与不利方面。     

点燃式发动机燃烧室沉积物的研究综述

本文系统综述了点燃式发动机燃烧室表面沉积物的形成机理、组成以及沉积物对燃料辛烷值的要求，沉积物对燃油经济性和未燃碳氨排放的影响，指出了燃烧室表面沉积物对发动机性能的有利与不利方面。     

点火式发动机中沉积物的形成及其影响

发动机燃烧室沉积物的形成及排气系统的积碳堵塞,造成发动机的不正常工作。本文着重探讨燃烧室中沉积物的形成机理、影响因素及其对发动机性能和排放的影响     

点火式发动机中沉积物的形成及其影响

发动机燃烧室沉积物的形成及排气系统的积碳堵塞,造成发动机的不正常工作。本文着重探讨燃烧室中沉积物的形成机理、影响因素及其对发动机性能和排放的影响。     

直喷汽油机气门积碳的成因与对策研究

针对在用汽油直喷发动机出现的气门积碳现象,对比缸内直喷汽油机与进气道喷射汽油机气门积碳组分与成因的差异,分析了缸内直喷汽油机进气门积碳的主要形成机理、影响因素和生成途径,其中气门表面温度、机油的物理和化学性能起了关键作用。在上述分析基础上,探讨了在发动机设计与应用层面减少进气门积碳的措施。     

混合器对国六柴油机选择性催化还原系统尿素结晶的影响

针对国六柴油机选择性催化还原(selective catalytic reduction,SCR)后处理系统尿素结晶问题,设计了两种不同的混合器结构。利用计算流体动力学(computational fluid dynamics,CFD)技术对两种混合器方案的尿素碰壁位置、尿素轨迹、气流速度、流速均匀性、NH_3均匀性、压力损失等进行了仿真分析和对比,最后通过发动机台架试验验证两种方案的排放性能和结晶性能。CFD分析及试验结果表明:方案二的气流速度、流速均匀性和NH_3均匀性都优于方案一,而方案一的压力损失小于方案二;方案一台架试验的结晶质量为608g,不满足主机厂要求,方案二台架试验的结晶质量为6g,满足主机厂要求。CFD分析和试验结果趋势一致,表明CFD分析是合理有效的。     

开阀喷射模式对进气道喷射式汽油机性能的影响

采用台架试验和数值计算的方法研究了开阀喷射模式对发动机性能的影响规律。研究结果表明:在20%节气门开度下,较早的喷油时刻与较晚的喷油时刻相比,功率升高了0.2kW,HC排放降低了30×10~(-6);当节气门开度达到100%时,由于进气气流和机体温度的影响使得喷油时刻对动力性和排放性能的影响可以忽略;处于20%节气门开度时未挥发燃油最大比例大约占总喷油量的50%,而在100%节气门开度下未挥发燃油仅占15%左右,可见燃油未完全挥发是造成开阀喷射模式时发动机性能下降的主要原因,提高开阀喷射模式下发动机燃油挥发性能是提升发动机性能的主要途径。     

Thermal analysis of cylinder head carbon deposits from single cylinder diesel engine fueled by palm oil–diesel fuel emulsions

This paper aims to evaluate the cylinder head carbon deposit from diesel engine fuelled by four samples of diesel fuel emulsions containing 0%; 5%; 10% and 15% vol. water and 20% Palm Oil Methyl Ester (POME) were subjected to thermogravimetric analysis (TGA/DSC) in air medium. The deposit build up processes were performed on a single-cylinder direct-injection diesel engine for period of 25 h for each set of test fuel under constant speed 2500 rpm. The TGA system was used and then correlated with elemental analysis as well as infrared spectra for microscopic observations. It has been found that, as the water increases in fuel, less aromatic and less reactive of deposits would be formed. Therefore, such method of analyses can be used as an indicator to verify the stability of carbon deposit inside the combustion chamber that could substantiate the applicability of a particular fuel to be accepted.     

A review on deposit formation in the injector of diesel engines running on biodiesel

For the short-term use of diesel engines, biodiesel can provide a comparable engine performance to that of using fossil diesel fuel. However, some arising problems including the reduction of the engine performance, the increase in lacquer deposits, and excessive carbon blacks in the combustion chamber and in the injectors resulting in an increase in the emissions and the damage to the engine have been indicated. Deposits formed inside or outside the injector may have an adverse influence on the engine performance and the fuel injection system. In this study, a review of the formed deposits in the injector of diesel engines fueled with biodiesel was conducted. The physicochemical mechanism of the deposit formation in the injector including injector nozzles, injector holes, and injector tips was mentioned. Moreover, the test-cycles for determining the deposit formation level in the injector were also introduced. Especially, the effects of the key factors such as biodiesel components, temperature, and injector configurations on the formation level of deposits were reviewed, and the utilization of the cativation mechanism in the controlling strategy of the deposits was presented. Besides, the impacts of deposits in the injector on the spray characteristics, combustion, and diesel engine operation process were also referred.     

中速柴油机燃用重质燃料油的试验及数值模拟研究

以某型号大功率中速柴油机为研究对象,以燃烧性能试验和数值模拟方法研究了重质燃料油在该机上的燃烧性能、动力性能和燃油经济性。研究表明:与燃用轻柴油相比,在燃用重质燃料油时,柴油机保持了原有的动力性能;燃油消耗率有所上升,但考虑重质燃料油的低成本因素,其经济性有较大程度改善。为了进一步改善燃油经济性并保证燃用重质燃料油时柴油机的可靠性,对喷油嘴等燃油系统关键部件进行改进设计是必要的。     

某型重油柴油发电机组相关问题的分析及改进

介绍了某型重油柴油发电机组在试验和使用过程中发现的功率开不足、缸内积碳及冒黑烟问题的分析及改进方案。改进后,该型柴油机功率开不足、烟度及燃烧效果得到了较好的改善,达到了预期的效果。     

Deposit formation characteristics of gasoline spray in a stagnation-point flame

Combustion chamber deposit has adverse effects on the performance and operation of various combustion devices, such as boilers, furnaces and engines. To study deposits by actually running combustion device for a long time to gather the deposit is very time and money consuming. In this investigation, we developed a deposit-forming technique by using a spray burner with water-cooled stagnation plate. The deposit could form on the stagnation plate readily and thus enabled us to investigate the formation of deposit under different operating conditions. We focused on the effect of the cooling water temperature and F/A ratio on the formation of deposit. In this paper, the temperature profile of the stagnation flow was measured for different F/A ratios to provide basic understanding of the thermal characteristics of two-phase flow burners. Then, the weight, formation area and H/C ratio of deposits were analyzed. It was found that the growth of deposit was faster for a lower cooling water temperature, i.e. lower surface temperature. The weight of deposit basically increased with time. H/C ratio showed a tendency to decline with the increase of F/A ratio. We also performed deposit formation tests on a CFR engine with 4 different fuel compositions. There was a qualitative correlation on weight of deposit between stagnation plate and CFR engine test. This study presents a simple experimental modeling on deposit formation. However, there are still some parameters relative to real engine conditions, such as pressure, turbulence to be considered in near future.     

液压自由活塞柴油机喷油特性研究

针对液压自由活塞柴油机的特点提出了共轨液压式柴油喷油系统,即利用液压自由活塞柴油机的高压油路替代供油系统的高压油泵。通过对共轨液压式喷油系统的原理分析,利用活塞式供油规律测试仪对其喷油规律展开离线研究,研究了不同驱动压力、不同喷射频率条件下的循环喷油量、喷油延迟时间的变化规律。为进一步研究发动机实际运行过程中气门控制油路等对喷油过程产生的影响,在线对循环喷油量进行了测量。结果表明:由于喷油器驱动油路和气门驱动油路连接在一起,气门驱动供油造成了喷油器驱动油路的压力波动,从而使得循环喷油量变动范围变大(-6.9%9.5%),最终影响发动机稳定运行。对发动机气门及喷油驱动油路改进后进行连续运行试验,试验研究结果表明:循环喷油量的波动及实际喷油位置的变化都会影响液压自由活塞发动机连续稳定运行,要实现液压自由活塞发动机连续可靠稳定运行,必须减小循环喷油量波动和喷油延迟时间。     

Fuel injector deposits in direct-injection spark-ignition engines

Controlling fuel injector deposits is recognized as a challenge for advanced direct-injection spark-ignition (DISI) engines. This paper gives a comprehensive overview of the research on formation, measurement, effect, and mitigation of injector deposits in DISI engines. Methodologies for the injector deposit studies include visual and compositional analysis. It is shown that injector deposits will reduce injector fuel flow rates, and lead to changes in spray characteristics. Consequently, spray angle and envelope are likely to be affected, and spray penetration distance as well as droplet diameter can be increased. Injector deposits are revealed to be primarily fuel-derived and created by two distinct free radical pathways, i.e., low temperature auto-oxidation and high temperature pyrolysis. Fuel compositions (olefins, aromatics, and sulphur), as well as T90 parameter, are significant factors in injector deposit formation. The worst consequences of injector fouling are pre-ignition, and engine misfiring and malfunction. Emissions, especially particulates, dramatically increase as the fuel injector becomes fouled. It appears that fuel detergent is the most effective method in controlling injector deposit formation if its chemistry and dosage rate are optimized. Outward opening piezo-driven injector configuration with a good surface finish, a sharp nozzle inlet, and a counter bore design, is useful in preventing injector deposit formation. Reducing injector nozzle temperature by methods such as designing special injector cooling passages, and improving engine design are also proven to be helpful in reducing injector fouling. Anti-deposit coatings only delay the onset of injector deposit formation.