共查询到18条相似文献,搜索用时 234 毫秒
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通过建立喷射系统CFD三维仿真模型,研究了柴油机SCR系统在空气辅助雾化条件下尿素喷射的喷雾速度流场、雾化粒径、喷雾形态和贯穿距等变化规律,并通过试验对模型进行了验证;根据喷射模型对SCR系统的喷孔直径等结构参数进行了优化设计,通过发动机ESC,ETC试验对还原剂雾化性能进行试验验证。试验结果表明:采用改进后的柴油机空气辅助喷射还原剂供给系统后,柴油机NOx排放和NH3泄漏等指标均满足国Ⅴ阶段排放法规要求,验证了所采用的喷雾特性仿真优化设计方法有效可行。 相似文献
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利用高速摄影技术,对空气辅助和无空气辅助两种典型的柴油机氮氧化物(NOx)选择催化还原(SCR)尿素喷射系统,在常温常压下的尿素喷雾特性和在定容燃烧弹内对空气辅助喷射系统在不同温度下的尿素喷雾特性进行了可视化试验研究.结果表明,随着尿素溶液喷射速率的提高,空气辅助喷射系统的喷雾贯穿距增大,喷雾锥角变小,且随着环境温度的上升贯穿距明显减小,发生碰壁现象的可能性减小;而无空气辅助喷射系统的喷雾形态则基本不受喷射速率的影响.应用粒子动态分析仪(PDA)对两种喷射系统的喷雾粒径分布进行的测试结果表明,空气辅助喷射系统的喷雾液滴粒径明显小于无空气辅助喷射系统,因而具有良好的喷雾特性. 相似文献
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准确模拟喷雾是提高缸内模拟准确性的关键,为了使模拟喷雾与试验喷雾更加一致,需要根据试验喷雾贯穿距及粒径对模拟喷雾进行标定。使用AVL FIRE软件建立定容弹及喷雾数值模型,对处于不同喷射工况(喷射压力、环境压力、油温)下的喷雾进行数值模拟,根据试验喷雾的贯穿距及喷嘴下方30 mm平面处SMD对模拟喷雾进行标定,并对不同喷射工况的标定参数选择进行探讨。结果表明:为了同时满足贯穿距和粒径的标定要求,需要根据工况参数对标定参数进行调整;对于本研究中的GDI喷油器,喷射压力10 MPa时使用KH-RT模型的模拟结果与试验值匹配较好,5 MPa时使用Huh-Gosman模型匹配更好;在喷射压力、环境压力和环境温度相同的条件下,高油温和低油温工况可以用同一套参数满足标定要求。 相似文献
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供油系统电磁延迟和液力延迟导致实际喷射脉宽与控制信号脉宽之间存在差异.利用由喷雾图像获取的喷雾脉宽作为实际喷射脉宽,对喷雾脉宽与控制信号脉宽之间对应关系进行研究.研究结果表明:单次喷射喷雾脉宽大于控制信号脉宽,且脉宽差量随着喷射压力增大而缩小,与背景气体密度基本无关;多次喷射喷雾脉宽大于控制信号脉宽,且脉宽差随着喷射压力增大而缩小;两次喷射喷雾间隔小于控制信号喷射间隔,且喷射间隔差在不同压力、预喷油量、控制信号间隔下保持不变;燃油融合现象发生的实际临界喷射间隔时间小于由喷油规律所获取的临界喷射间隔时间.本研究提出了利用喷雾对供油系统喷射脉宽进行研究的新思路,并为多次喷射控制策略的优化提供指导. 相似文献
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喷嘴孔数及其布置对汽油直喷喷嘴闪沸喷雾-环境气体相互作用影响的研究 总被引:1,自引:0,他引:1
为了区分火花塞点火式缸内直喷(SIDI)发动机喷雾和环境气体两相流场,将优化后的高速双色PIV(Particle Image Velocimetry)技术应用于多孔直喷喷油器的喷雾和环境气体速度的测试.此双色PIV系统由一个特殊的示踪和滤波系统组成,可同时对燃油喷雾及其环境气体的速度场进行测量.本研究采用该双色PIV方法研究不同环境压力和燃油温度的条件下,喷嘴孔数及其布置情况对燃油喷雾和环境气体的相互作用的影响.在此研究中,对3个汽油直喷喷嘴做了详细的研究,包括1个6孔喷嘴,1个3孔喷嘴及1个2孔喷嘴.研究结果表明,随着燃油温度的提高或者环境气体压力的降低,喷雾雾化增强,燃油颗粒粒径减小,导致喷雾油束变宽,喷雾与环境气体接触面积变大,喷雾和环境气体的两相流场的作用变强.不同孔数和布置的喷油器在冷态及闪沸条件下油束间干扰作用的强度不同,导致喷雾传递给环境气体的动能不同.较强的油束间的干扰作用加强了燃油喷雾与环境气体之间的动量交换过程,进而增强了环境气体的动能. 相似文献
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H. S. Kook 《International Journal of Automotive Technology》2008,9(4):493-500
Flows over cavity openings are known to be highly structured and periodic due to the strong sound pressures emitted by the
cavities. This article is concerned with the measurement of flow fields over the sunroof opening of an SUV. Since the PIV
system used in the present work is not capable of taking phase-locked velocity fields during the measurement stage, phase-marked
PIV measurements are performed and the phase-locked velocity fields are retrieved during a post-processing stage. The new
PIV measurement method is shown to yield fairly accurate results with a proper choice of a phase-bandwidth. By using the phase-marked
PIV measurement method, the evolution of large-scale structures in shear flow over the sunroof opening as phase changes is
revealed. The detached shear layer is shown to fluctuate and then form a discrete large vortex convecting and impinging on
the rear roof edge of the SUV. The average convection velocity of the vortex is calculated to be 0.45 of the nominal free
stream flow velocity. Flow fields are compared for four different cases of deflector protrusion and a case without a deflector.
Installation of a deflector can significantly change the flow field. For a deflector that reduces the buffeting noise by more
than 10 dB, it is shown that turbulent fluctuations are initiated by the deflector but do not grow in amplitude as they convect
downstream. As the deflector protrusion is increased, the amount of flow under the deflector increases in general. The flow
exiting from the channel formed by the deflector and an A-frame is shown to increase the thickness of the shear layer near
the leading edge of the sunroof opening. 相似文献
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Air flow inside an automotive HVAC module was visualized using a high-resolution PIV technique with varying temperature control
modes. The PIV (particle image velocimetry) system used for the experiment consisted of a 2-head Nd:YAG laser (125 mJ), a
high-resolution CCD camera (2 K × 2 K), optics and a synchronizer. A real automotive HVAC module was used as a test model,
and some of its casing parts were replaced with transparent windows to capture the flow images of the laser-light-sheet illumination.
In addition, instant velocity fields were measured for three different temperature control modes by adjusting the temperature
baffle. Characteristics of the air flow inside the automotive HVAC were then evaluated based on the time-averaged PIV data.
Results from the experiment showed that flow for the warm mode loses more momentum due to its complicated flow path. Thus,
the present PIV data can be used to validate numerical prediction and to improve the performance of HVAC modules. 相似文献
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《JSAE Review》1999,20(3):407-411
Ignition and combustion characteristics of a two-stage injection diesel spray were experimentally investigated. A constant volume combustion chamber was filled with air which was controlled at 3.0 MPa and 743–923 K. In order to measure the ignition delay and the ignition position, a high speed video system was used. A 306 nm interference filter and an image intensifier system were attached to the camera for detecting the OH radical emission. The results show that the ignition delay of a two-stage injection spray becomes shorter compared with that of a single injection spray. The ignition positions of two-stage injection spray are observed nearer to the nozzle than that of single injection spray. Also, the temperature limit of complete combustion on a two-stage injection spray becomes lower than that of a single injection spray. 相似文献
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M. Xu Y. C. Sun Y. Cui K. Y. Deng L. Shi 《International Journal of Automotive Technology》2016,17(1):109-118
In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions. 相似文献
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In the following paper, a numerical study of the atomization, vaporization and wall impingement processes of hollow-cone fuel
spray from high-pressure swirl injectors under various ambient temperature conditions was carried out. Also, the availability
of applied models and the effect of ambient temperature on spray characteristics is discussed. The Linearized Instability
Sheet Atomization (LISA) model combined with the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model, the improved
Abramzon model and the Gosman model are used to calculate the atomization, vaporization and wall impingement processes of
hollow-cone fuel spray, respectively. Spray models are implemented with the modified KIVA code. The calculation results of
the spray characteristics under two ambient temperatures, including spray tip penetration, spray structure and radial distance
after spray-wall impingement are compared to the experimental results obtained by the Laser Induced Exciplex Fluorescence
(LIEF) technique. The droplet size distribution, ambient gas velocity field, vapor phase distribution and fuel film mass generated
by spray-wall impingement, measurements which are generally difficult to obtain by experimental methods, are also calculated
and discussed. Quantitative discussions on the effect of the ambient temperature on the spray development process are conducted.
It is shown that the applied models are applicable even in the high ambient temperature condition. 相似文献