设为首页收藏本站

科技网

[技术] 模型蒸汽轮机制作(转)

[复制链接]
发表于 2018-4-25 12:38:52 | 显示全部楼层 |阅读模式
模型汽轮机的笔记。 警告:小心使用蒸汽,特别是蒸汽涡轮发动机。 发动机操作的能量易产生蒸汽爆炸,轴承故障和其他危险!模型蒸汽涡轮机的制造非常简单,这里把模型蒸汽轮机制作分享给大家。
蒸汽轮机参考材料
第一台现代汽轮机是由英国人查尔斯A.帕森斯于1884年发明的:
帕森第一台涡轮机...

模型蒸汽轮机制作

模型蒸汽轮机制作


两种蒸汽轮机。 大多数型号将是“冲动式”涡轮机......

模型蒸汽轮机制作

模型蒸汽轮机制作



 楼主| 发表于 2018-4-25 12:39:44 | 显示全部楼层
Most models will be of the impulse variety due to the difficulties of producing the complex curves for a reaction turbine. Most commercial turbines are reaction. With an impulse turbine, steam velocity is everything, but there are tradeoffs. An air powered engine will generate the most velocity with a converging nozzle such as is described on the three rotor turbine below. However, steam is heated and can expand. In that case, providing more volume just before injection to the rotor blades converts as much heat as possible to velocity. So, a diverging nozzle (such as the "trumpet" nozzle on de Laval's turbine below) works better there.
Another issue is operating efficiency versus RPM. One of Parson's essential insights was to use successive stages that each expanded the steam a bit more to extract maximum energy from the steam expansion as well as designing a turbine that could run at a little slower rpm's than his predecessor's turbine Dr de Laval:

模型蒸汽轮机制作

模型蒸汽轮机制作

The de Laval turbine used trumpet shaped nozzles to extract most of the expansion energy from the steam, but it ran at velocities that were too high for the materials of the time except in very small applications. Might make for an interesting model though!
In fact, it is the use of multiple stages and more gradual steam expansion among the stages that leads to the greater efficiency at slower speeds of Parson's design. The different diameters at each stage are what allow for expansion on this 70,000 HP steam turbine rotor:

模型蒸汽轮机制作

模型蒸汽轮机制作

Increasing rotor diameters allow for steam expansion...
 楼主| 发表于 2018-4-25 12:40:08 | 显示全部楼层
Here is a rotor from Parson's first turbine:

模型蒸汽轮机制作

模型蒸汽轮机制作


模型蒸汽轮机制作

模型蒸汽轮机制作


模型蒸汽轮机制作

模型蒸汽轮机制作

 楼主| 发表于 2018-4-25 12:40:40 | 显示全部楼层
Straight bladed rotor must have been difficult to construct without CNC!
The blades were made of drawn brass. Each blade was fitted into a groove with a wedge, called a "distance" piece in the drawing. Here is some more on the labyrinth passages that connect each stage:

模型蒸汽轮机制作

模型蒸汽轮机制作


Guide blades redirect the steam direction for the next stage...
In modern times I'm sure the shape of the blades is carefully predicated on aerodynamics similar to those used to design airplane wings, but in Parson's time, no such understanding was available. His shapes were trial and error combined with intuition. Nevertheless, they were not bereft of sophisticated knowledge in other ways. For example, they determined that the optimal velocity of the blade was 1/2 to 3/4 of the velocity of the steam, hence the very high operating speeds of these turbines. Parson's first model ran at 18,000 rpm.

模型蒸汽轮机制作

模型蒸汽轮机制作

Isn't this a lovely curvaceous Parsons' turbine?
The model steam turbines I've seen are not Parson's turbines, they are impulse turbines, and hence the wind up to ridiculously high velocities. Enough to blow the bearings, so be careful! It would be fascinating to see a model Parsons, but the issue would be in the much increased complexity of many rotors for gradual expansion as well as complex shapes to machine on the rotor and stator blades. Certainly not impossible, as we see model gas turbines, just not easy.
 楼主| 发表于 2018-4-25 12:41:15 | 显示全部楼层
Bogstandard's Single Rotor Impulse Steam Turbine
Bogstandard is (was, he may have left the forum) one of the real geniuses on the HMEM board. I learned a lot of things from him and always admired the fine craftsmanship of his model engines.
Here are photos from the first thread, a single rotor turbine that's really cool.

模型蒸汽轮机制作

模型蒸汽轮机制作


模型蒸汽轮机制作

模型蒸汽轮机制作

Raw materials, and machining the "buckets" on the rotor...

模型蒸汽轮机制作

模型蒸汽轮机制作

 楼主| 发表于 2018-4-25 12:45:43 | 显示全部楼层

模型蒸汽轮机制作

模型蒸汽轮机制作


Parts. Note the steam ports on the housing. The first version had perspex on both sides...

模型蒸汽轮机制作

模型蒸汽轮机制作

I like the final version better. The back side is perspex. There is a little Swiss motor set up as a generator, and as the rpm increases, you see the LEDs light up one by one. The model is beautiful, and shows Bogstandard's trademark "bling" touches to make it more decorative.
This one was made "on spec" for a model boater. Ultimately they concluded that the space available on the boat and the power characteristics made it impractical. These turbines don't make much power until they get over 10K rpm, and the more rpm you give them, the more prone to runaway they are. A 15 or 20:1 gear reduction would be needed as well as some form of speed governor to prevent the turbine from blowing up its bearings. Here is what it looks like when a model turbine blows:

模型蒸汽轮机制作

模型蒸汽轮机制作

Note the shredded housing as the rotor blew. Excercise care running these little engines to avoid exceeding their limits!
 楼主| 发表于 2018-4-25 12:46:32 | 显示全部楼层
Getting back to the three rotor, here are some photos (many more on this one!):

模型蒸汽轮机制作

模型蒸汽轮机制作

Sketch. Note how the leftmost rotor is a reversing rotor, so the "buckets" go the other way?

模型蒸汽轮机制作

模型蒸汽轮机制作


模型蒸汽轮机制作

模型蒸汽轮机制作

 楼主| 发表于 2018-4-25 12:54:01 | 显示全部楼层
Turning the basic shape in phosphor bronze

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

Rotor stack is drilled to lighten it...

模型蒸汽轮机制作

模型蒸汽轮机制作

 楼主| 发表于 2018-4-25 12:54:24 | 显示全部楼层

模型蒸汽轮机制作

模型蒸汽轮机制作


Areas in green on the shaft are knurled to hold the shaft and rotor together...

模型蒸汽轮机制作

模型蒸汽轮机制作


模型蒸汽轮机制作

模型蒸汽轮机制作


 楼主| 发表于 2018-4-25 12:54:50 | 显示全部楼层
With the shaft press fitted, skim cuts are taken to ensure balance relative to the shaft...

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

Now the buckets are being cut. It comes out looking quite exotic and beautiful, no?

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

模型蒸汽轮机制作

您需要登录后才可以回帖 登录 | 注册

本版积分规则

辽公网安备 21100402204006号|科技网 ( 辽ICP备07501385号-1   

GMT+8, 2019-11-20 13:23

Powered by tech-domain X3.4 Licensed

© 2001-2017 Comsenz Inc.

快速回复 返回顶部 返回列表