Turbine Nozzle & Bucket Manufacturing

What Are Turbine Buckets? 

Turbine buckets are an important part of gas turbine stage design. Each stage unit contains a nozzle with a wheel and accompanying bucket. Further turbine sections include the turbine rotor, turbine shell, nozzle, shroud, exhaust diffuser, spacers, and exhaust frame. 

A turbine bucket consists of a leading edge, trailing edge, root portion, and tip portion. Turbine buckets also include cooling holes for cooling liquid running through the bucket. First stage buckets are the first surface that the gases from the first nozzle encounter. Given this, they require high heat resistance to function at standard operating temperatures without failure. 

As the air passes through the first stage bucket, it flows through cooling holes and exits out of the recessed bucket tips. Cooling holes spaced evenly around the turbine bucket's interior allow air through the plenum and function to cool the airfoil without requiring compressor air. 

Due to the pressure drop between each stage of a gas turbine, progressive turbine buckets need to be larger than the previous. The second stage buckets do not require shank cooling, so they use cooling holes to reduce airfoil temperature without losing energy during the cycle. Enclosing the third stage bucket is a turbine shroud that connects to each bucket to dampen vibrations from rotor motion. 

Each bucket connects to its turbine wheel with a set of tang dovetails that fit into cutouts placed around the wheel rim. The dovetails then connect to bucket vanes that line the top and bottom of the turbine rotor. The lengthened design of the wheel attachment and spacers ensure that the dovetails do not overheat. 

Turbine Nozzle and Vane Design

Each turbine section contains a stationary nozzle that directs the compressed combustion gas into the buckets. The force of the gas stream emitted from the nozzles pushes against the turbine buckets and turbine blades, causing the entire rotor to spin. This setup creates high pressure and heat flow. That's why each gas turbine has seals on the interior to prevent thermodynamic leakage. Turbine nozzles or vanes are an essential part of a gas turbine and must be capable of withstanding thermal stresses and intense pressure from heated gas.

Like buckets, there are three stages of nozzles. The first stage nozzle directly receives gas from the main combustion system through transition pieces. These transition pieces minimize compressor leakage and attach to a retaining ring, which also works to seal the gap between turbine vane and the outer shell. The nozzle support ring supports the first stage vane via bolts that anchor it to the outer casing. 

By design, each stage vane reuses combustion gases from the previous stage. To that end, the second stage nozzle redirects pressure against the second stage turbine bucket. Likewise, the third stage nozzle receives gas exiting the second stage turbine bucket and directs it to the third stage turbine bucket. The tiered stage design of the modern gas turbine ensures maximum efficiency and minimal heat loss from each part during the process. 

High-Performance Turbine Components

Much of the current research on turbine performance involves analysis into modification techniques to increase temperature resistance. Vanes, turbine blades, turbine buckets, and each wheel and turbine rotor component need to withstand extreme sheer force and centrifugal force, along with heat.

Materials capable of higher temperatures reduce the need for cooling holes, so there is less heat flow and less energy lost during the gas transfer process. Thanks to these advancements, modern blade and turbine buckets often have a 30-year operational life. 

Alloy Creep

One common deficiency in modern airfoil blades is alloy creep. Vanes in the center wheel rotate with great force. This centrifugal force can cause plastic deformation in blades and buckets over time, resulting in the need for replacement. Turbine buckets under creep stretch out of alignment, upsetting the integrity of the seal in the gas turbine unit. The result is lower turbine efficiency. 

New forms of casting turbine alloys, such as single crystal casting and directionally solidified casting, aim to solve these issues in material degradation. These procedures alter the molecular structure of alloy to create a directional axis along the turbine blade. This type of modification improves the form of the turbine blade and improves the integrity of the turbine section. 

Fatigue and Corrosion of Turbine Blades and Buckets

Turbine blades and turbine buckets are also susceptible to material fatigue. Buckets, blades, and nozzles encounter high temperatures and extreme force from gas. Improved air cooling implemented in advanced gas turbine design can increase operational life by reducing the overall strain on materials. Incorporating more heat-resistant materials can reduce the thermal load borne by each part of the turbine. 

Corrosion from the environment is also a pressing concern for modern turbine design. Oxidation of alloys in the path of gases can degrade turbine blades, vanes, and buckets, compromising their structural integrity. Most turbine blade and turbine bucket corrosion solutions involve chemically resistant coatings, modification, and super-alloys that require less cooling than regular alloys. 

At Hi-Tek Manufacturing, we specialize in high-performance land and aviation turbine nozzle and turbine bucket manufacturing. Our high-tech facility features a 138,000square foot manufacturing space dedicated to the precision engineering of components. Every piece we make passes through several phases of quality assurance to guarantee a high-caliber product. 

Modern-designed gas turbine blades and turbine buckets need to be capable of operation under extreme industrial stresses. We use state-of-the-art CAD/CAM systems to design our turbine nozzles, turbine blades, turbine buckets, and rotor systems. Our expert team of engineers has extensive experience in machine tooling and achieves a standard of precision and excellence unmatched in the industry. 

We produce Stage 1, 2, 3, and 4 turbine blades from machining and processing to finishing and sales. Turbine buckets and turbine blades are an area of particular interest for our team, but we also make a wide range of other technical gas turbine components. We strive to outmatch our competition with superior craftsmanship. 

What are the Benefits of Using Nickel-Based Alloys for Aerospace Applications?

Creep Resistance

Using nickel superalloys for aerospace and aviation applications provides advantages you won’t get with other alloy metals. Nickel combined with certain metals can create a high-temperature alloy with numerous beneficial properties, like resisting creep and other extreme conditions while offering reliable performance.

Creep is the tendency for individual components within larger systems to move and change position under the wear-and-tear from daily use and constant high pressures. Nickel alloys have extraordinary creep resistance and can also withstand extreme conditions or temperatures.

High Strength and Corrosion Resistance

Nickel alloys also have naturally high strength, which means they can withstand very intense pressure and situations due to the high oxidation resistance and corrosion resistance they possess. This high resistance makes virtually every nickel alloy well-suited for high-pressure operations where strength and durability are of the utmost importance.

Nickel Alloys Are an Integral Part of Aerospace Industries and Applications

It's plain to see how important a nickel-based, high-temperature alloy can be for applications in the aviation, aerospace, and military industries. The beneficial properties of alloys also make them perfectly suited for creating air, land, and marine-based engine parts, gas turbines, and other applications.

At Hi-Tek Manufacturing, we know the importance of using nickel alloys for aerospace applications. Our fully-equipped, state-of-the-art machine shop produces precision CNC-machined components and assemblies for aviation, marine, and land-based applications. We also manufacture engine parts, gas turbines, and a high amount of nickel aerospace alloys. We handle every project with our 40+ years of skill and expertise to produce flawless components that can withstand the high stressors of the aerospace industry. Contact us for a quote today.

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