It’s been less than a month since the release of the iPhone7. There are a lot of exposure spy photos on the iPhone7, and it’s said that the photos of the iPhone7 production drawings have been made. From the drawing, the design and details of the iPhone7 have been basically confirmed.
The first is from the overall appearance of the given production drawings show, iPhone 7 is the appearance before the exposure. There was not much change in the front, and the overall design of the back cover part of the antenna and the camera was changed. From the description of the details, it is completely the front-end design of the previous generation, but does not describe whether to adopt the touch-type touch-ID design.
It is worth mentioning that the details of this production drawing do not mention the design of the headphone jack. So, before the iPhone 7 cancel headphone jack argument to be further confirmed. But from the previous survey, most of the users are not able to accept the fact canceled 3.5mm headphone jack design, do not know after the iPhone 7 release will not change this situation yet. â–
A reaction turbine is a type of steam turbine that works on the principle that the rotor spins, as the name suggests, from a reaction force rather than an impact or impulse force.
In a reaction turbine there are no nozzles to direct the steam like in the impulse turbine.
Instead, the blades that project radially from the outer edge of the rotor are shaped and mounted so that the shape between the blades, created by the cross-section, create the shape of a nozzle. These blades are mounted on the revolving part of the rotor and are called the moving blades.
The fixed blades, which are the same shape as the moving blades, are mounted to the outer casing where the rotor revolves and are set to guide the steam into the moving blades. Below is a simple diagram of reaction turbine blades:
Reaction Turbine Principle:
In the case of reaction turbine, the moving blades of a turbine are shaped in such a way that the steam expands and drops in pressure as it passes through them. As a result of pressure decrease in the moving blade, a reaction force will be produced. This force will make the blades to rotate.
Reaction Turbine Working:
A reaction turbine has rows of fixed blades alternating with rows of moving blades. The steam expands first in the stationary or fixed blades where it gains some velocity as it drops in pressure. Then enters the moving blades where its direction of flow is changed thus producing an impulse force on the moving blades. In addition, however, the steam upon passing through the moving blades, again expands and further drops in pressure giving a reaction force to the blades.
This sequence is repeated as the steam passes through additional rows of fixed and moving blades.
Note that the steam pressure drops across both the fixed and the moving blades while the absolute velocity rises in the fixed blades and drops in the moving blades.
The distinguishing feature of the reaction turbine is the fact that the pressure does drop across the moving blades. In other words, there is a pressure difference between the inlet to the moving blades and the outlet from the moving blades.
Special Aspects of Reaction Turbines
- There is a difference in pressure across the moving blades. The steam will, therefore, tend to leak around the periphery of the blades instead of passing through them. Hence the blade clearances as to maintain as minimum as possible.
- Also, due to the pressure drop across the moving blades, an unbalanced thrust will be developed upon the rotor and some arrangement must be made to balance this.
Reaction Steam Turbine
Shandong Qingneng Power Co., Ltd. , https://www.steamturbine.be