甄嬛甘露寺Gasoline Fuel Injector Spray Measurement and Characterization
汽油燃油喷油器喷雾测量与特性
3. BASIC SPRAY CHARACTERISTICS AND DEFINITIONS
基本的喷雾特性与定义
3.1 Introduction to Gasoline Fuel Spray
汽油燃油喷雾的介绍
The primary function of the gasoline fuel injector is to accurately meter the required amount of fuel. Another key function, however, is to atomize the injected liquid fuel. The transformation of the liquid stream into a myriad of small gasoline drops dramatically increas the surface area of the injected fuel, thus enhancing the rate of vaporization. The transient event that simultaneously meters and atomizes the liquid gasoline may be considered as concurrent spray formation and penetration process that occur on the orde
r of milliconds. The resultant atomization is a positive factor in the port fuel injection application, but is an even more critical factor for gasoline-direct injection, due to the fact that for G-DI, the available time interval between the end of injection and ignition is very brief. The mean diameter of a reprentative sample of the delivered gasoline drops is a statistical metric that is a key measure of goodness of the spray delivered by a
酒煮鸡蛋particular injector. As the mean diameter becomes smaller, the surface-to-volume ratio of the injected gasoline increas, and the vaporization rate increas substantially.
汽油燃油喷油器的一个基本功能是精确计量需要的燃油量。另一个关键的功能是将液态燃油喷射成雾状。液流变成大量的小的汽油颗粒大大地增加了喷射燃油的表面积，加快燃油汽化速度。液态汽油的计量和雾化两个同步瞬态事件可以看作以毫秒级时间发生的喷雾生成和渗透过程。由于在GDI喷射结束和点火之间的有效时间间隔非常短，由此产生的燃油雾化是进气道燃油喷射应用的一个重要因素，更是汽油直接喷射应用的一个决定性因素。输送的汽油油滴典型样本的平均直径是一个统计指标，是特定喷油器输送的喷雾效果好坏的关键测量指标。如果平均直径变小，喷射的汽油的面容比就增大，汽化速率就大幅提高。
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There are many spray classifications in the field of gasoline injection, but the initial, primary classification is historically bad upon the application. The two major gasoline applications are port fuel injection (PFI) and gasoline, direct, incylinder injection (G-DI). This is illustrated in Figure 1. In general, the PFI injector application utilizes relatively low fuel pressures of less than 0.5 MPa, and achieves a mean drop diameter in the range from 50 to 200 microns in the delivered spray, depending upon the design. SAE J1832 refers to injectors with fuel pressure below 1000 kPa as low-pressure gasoline injectors. The G-DI injector, however, is required to deliver a mean drop diameter of less than 30 microns in order to sustain combustion; therefore, extensive measures such as a high fuel pressure (5.0 to 20.0 MPa) or the introduction of compresd air are generally required.
在汽油喷射领域有多种喷雾分类，但是最初的基本分类是以往基于应用的分类方法。两个主要的汽油应用是进气道燃油喷射（PFI）和汽油缸内直接喷射（GDI）。如图1所示。一般来说，PFI喷油器应用使用相对较低的燃油压力，低于0.5MPa，在生成的喷雾中形成的平均油滴直径范围是50微米到200微米之间，与具体设计有关。SAE J1832中将低于1000
KPa燃油压力喷油器称为低压汽油喷油器。然而，GDI直接喷射喷油器要求生成的喷雾平均油滴直径小于30微米才能维持燃烧，因此，需要更广泛的测量，如高燃油压力（5.0到20.0MPa）或者引入压缩空气。南京狮子桥美食街
FIGURE 1 - MAJOR CLASSIFICATION OF SPRAYS FROM AUTOMOTIVE FUEL INJECTORS
Typical geometric configurations for both a PFI application and a G-DI application are illustrated in Figure 2. On the right in this illustration, α depicts the injector mounting angle relative to the engine fire deck, and β depicts the spray angle of the spray plume. In the port injector classification illustrated on the left panel in Figure 2, the fuel injector is positioned to introduce the fuel spray into the intake port upstream of the intake valve or valves. This may be anywhere within a significant range of distances from the injector tip to the rear face of the intake valve. This distance is commonly referred to as the “targeting distance”, and is a key parameter in the overall design of the combustion system. The PFI injector is most commonly mounted in the intake manifold runner, which yields targeting distances of 65 to 120 mm. Some special applications such as supercharging may have the injector mounted in the cylinder head portion of the intake runner, with associated shorter targeting distances of 40 to 65 mm. This option, and the G-DI in-cylinder mounting, generally yield elevated injector operating temperatures. The ti
ming of the port fuel injection event in the vast majority of applications occurs while the intake valve is clod, and with no mean airflow in the port. This results from the obrved fact that engine-out UBHC (unburned hydrocarbon) emissions are significantly elevated if injection into the port occurs during the period when the intake valve is open. The fuel spray from the PFI injector normally requires from 4 to 9 milliconds to traver the targeting distance and to impact the rear face of the intake valve. This rear face is the most common “target” for the fuel spray axis, which is again due to the obrved fact that the engine combustion and emission characteristics are both degraded as greater amounts of the fuel spray mass are allowed to contact the port wall.
PFI和GDI应用的典型几何结构如图2所示。在右图中表示喷油器相对发动机点火平面的安装角度，表示喷雾的喷雾角。在图2左边所示进气道喷油器类型中，燃油喷油器是在将燃油喷雾引入到进气阀的进气口上游的位置。它的位置可以是在喷油器顶端到进气阀背面距离范围内的任何地方。这个距离通常称为“目标距离”，而且是整个燃烧系统设计中的一个关键参数。PFI喷油器通常安装在进气歧管，目标距离是65到120mm。一些象增压压力一样特殊的应用可能要求喷油器安装在进气歧管的缸盖部分，另外有40到65mm的较短的目标距离。一般这种选择和GDI缸内安装将具有提高喷油器工作温度的作用。在大多数实际应用中，进气道燃油喷射事件发生在进气门关闭时刻，而且在气道里没有有效的空气流。实际观察的结果是，如果在进气门打开期间在气道内进行喷射，发动机的未燃烧碳氢排放会严重增加。通常要求PFI喷油器的燃油喷雾在4到9毫秒通过目标距离，与进气门背面发生碰撞。这个气门的背面就是通常燃油喷雾轴线上的“目标”，同样实际观察表明当更多燃油喷雾的燃油量与进气道壁面接触时，发动机的燃烧和排放特性都将下降。
FIGURE 2 - SCHEMATIC REPRESENTATIONS OF THE PORT FUEL INJECTION
AND GASOLINE-DIRECT INJECTION CLASSIFICATIONS
The G-DI injector, in contrast, introduces the fuel spray directly into the engine cylinder. This is depicted schematically in the right panel of Figure 2. As a direct conquence of the very limited time available for penetration, evaporation and mixing, the spray must, out of necessity, be significantly more brief and of a finer atomization level than that from a PFI injector. The G-DI injector may be open less than 2 milliconds at light load operat
半导体制冷ing conditions, and will normally exhibit a mean drop size that is an order of magnitude smaller than that of a PFI spray. The time scale of the spray event is quite different for the two main application classifications, with nearly all of the event time markers such as injector opening, spray formation, pul duration, penetration, vaporization and injector closing being two to four times faster for direct injection. This is, of cour, forced by the stringent timing requirements for achieving stable combustion when injecting directly into the combustion chamber. As is the ca for the mounting of PFI injectors, a number of options exist for G-DI injectors. Depending upon the type of intended combustion system, the spray may be intentionally directed at the piston crown, at a special bowl in the piston crown or against or with the in-cylinder air motion.
关于读书的议论文相反，GDI的喷油器直接将燃油喷雾引入到发动机的汽缸。如图2右图所示。出于必要性，一个对渗透、蒸发和混合有效的非常有限时间，喷雾必须更短（简单），而且要比PFI喷油器有更好的雾化水平。在小负荷工作条件下，GDI喷油器的打开时间可能小于2毫秒，而且通常体现出油滴的平均尺寸要比PFI喷雾小一个数量级。从这两种主要的应用类型来看，喷雾事件的时间范围非常不同，对于直接喷射几乎所有事件的时间标注，如喷油器打开、喷
太原迎泽公园
雾生成、脉冲持续时间、渗透、蒸发和喷油器关闭等，都要快2到4倍。当然，这是直接喷射到燃烧室时实现稳定燃烧对时间有严格要求的原因。象PFI喷油器的安装情况一样，GDI喷油器的安装也有许多的选择。根据燃烧系统的类型，喷雾可能故意直接喷射到活塞顶部、活塞顶部专门的凹坑、或者与缸内空气运动方向一致或者相反。
For the transient process of spray formation, penetration and dissipation, there are a number of key spray features that may be readily identified. The features are illustrated and identified in Figure 3. Although the spray features are illustrated schematically for a G-DI injector spray, nearly all tho shown except for the toroidal vortex also exist in the port injection spray. Thus, each classification may have an early sac spray and a later main spray, and may have one or more after-injections.
