Category Archive: Subscale Jet Engine Testing

The Testing Capabilities of Subscale Jet Engine Rigs – Part 2

High performance machines, such as jet engine and gas turbine parts, need to endure arduous environments for extended periods of time and perform their functions reliably time after time. The parts designed for combustors and turbine systems are subjected to harsh environments resulting from the combined effects of high temperature, combustion gas products and the CF load for rotating parts.

Of course, performing a full-scale engine test would create the most realistic test conditions, but typically these tests can be time consuming to prepare and expensive to perform. It is also an impossible exercise in early stages when the engine and its hardware are still in design and development.

Engineers and scientists working on the development of new materials, coating systems, sensors and part designs for new engine need test data to evaluate and refine their work. Gas burner or torch testing are much more affordable options, but they often fall short of providing the most realistic test conditions.

Fortunately, there is a solution to address and bridge the information gap that currently exists within testing capabilities. Test Devices Inc. provides subscale jet engine testing services to customers who are looking for a more affordable and practical way to gather relevant test data with a high level of realism for materials, coatings, and sensors for new engines in development. Subscale jet engine tests can be readily used to evaluate several essential qualities, including:

  • Coating characterization, performance, and durability
  • Oxidation and corrosion
  • Creep and fatigue
  • Fuel burn studies
  • Blade high cycle fatigue
  • Volcanic ash and CMAS

In this blog, we will discuss the value of subscale testing in coating studies and oxidation and corrosion testing. For a deeper dive into creep and fatigue testing and blade high cycle fatigue testing, be sure to check out the first part of this blog series, The Testing Capabilities of Subscale Jet Engine Rigs – Part 1.

Engine Testing for Challenging Environments

Jet engines are constantly subjected to harsh environments—usually for extended periods of time. Nevertheless, their components must perform consistently and reliably despite these unfavorable conditions.

The blades, vanes and disks of turbomachines often have intricate geometries to optimize aerothermal efficiency. Because such components are routinely subjected to complex mechanical and thermal loading cycles, they can be particularly sensitive to potential damage. The designs of these parts must account for the combined effects of high CF loads, intense heat, and byproducts of gas combustion.

For example, high pressure turbine blades operate above the melting temperature of their base composition metals. Because they are equipped with a precisely designed film air cooling system and a thermo-barrier coating (TBC), the blades can still withstand the extreme temperatures and perform the necessary function without fail.

TBCs, however, can be compromised by oxidation and corrosion, subsequently undermining the performance of the blades themselves. As a result, durable coatings that protect the overall system from damage are essential to a successful jet engine design.

Subscale jet engine tests can be a useful and affordable platform for studying and understanding coating and material degradation when subjected to corrosion and oxidation elements:

  • Coating damage studies via surrogate engine use a subscale jet engine as a surrogate test vehicle, modified to accommodate necessary instrumentation. The engine’s turbine blades carry the test coating in question while being introduced to corrosive chemicals for damage observation.
  • Coating and air film cooling testing uses the subscale jet engine as a hot gas generator. A plate type test specimen is instrumented with embedded thermocouples (or IR pyrometers) to monitor its operating temperature and then placed in the hot gas stream. Temperature of the exhaust gas and test plate can be controlled independently by an air-cooling system attached to the test plate.
  • Aerothermal studies and exhaust gas stream characterization is another process that uses a subscale jet engine as a hot gas generator. The test can be used to economically study the performance of a vane (or nozzle) design by using scaled prototypes manufactured from 3D printers. The use of a robotic sensor probe accurately captures the flow temperature and pressure at defined coordinates in the hot exhaust gas stream and maps the data in a 3D space to validate a CFD model and update the design.

With subscale jet engine rigs, engineers and designers can test and study the performance of newly designed parts in more realistic test conditions, reducing the risk of “surprises” and contributing to the confidence of a successful launch and the operation of new products.

Small Turbine Rig Testing with Test Devices, Inc.

A small turbine test rig offers a viable alternative to pre-existing test methods, including superior test realism and several other attractive advantages:

  • Affordable: Testing on a small turbine test rig is much less expensive to perform when compared with a full-scale engine test.
  • Efficient: The ability to complete test projects in a few months rather than years
  • Flexible: It is easy to change test parameters, including adding/removing sensors and instrumentations, varying the engine or test hardware configurations.

At TDI, we rely on our extensive experience with subscale jet engine testing to develop dependable test solutions to even the most challenging mechanical needs. To learn more about small rig and subscale jet engine testing with our team, download our eBook, The Importance of Subscale Jet Engine Testing or reach out to request a quote today.

 

Download Our Subscale Jet Engine Testing Guide

Exciting Facility Updates at Test Devices

As the rate of jet engine part production has rapidly increased and our clients continue to forecast further growth, we’ve become a trusted spin testing & spin process provider. To keep up with rising demand and continue to offer the most cutting-edge services available, Test Devices, Inc. has completed multiple facility expansions in recent years.

So, what’s new at Test Devices, and what do our latest expansions mean for our customers?

Facility and Capability Expansion

Our latest expansion incorporates improvements in both the shipping and receiving department and the equipment build area. We’ve also recently acquired a new coordinate measuring machine (CMM)!

  • Spin Rig Assembly AreaShipping and receiving — To re-engineer the flow of parts coming into and out of our building, we relocated the shipping and receiving department to the front of the building to allow for expanded storage and handling areas along with additional cranes. In addition, the new area includes both plenty of space for trucks to back-in and an adjustable loading dock, allowing our forklifts to directly unload trailers. The relocation and improvements make unloading and loading operations significantly more efficient, contributing to reductions in turn-around time of customer parts.
  • New coordinate measuring machine — To support the needs of our growing forging pre-spin business, we remodeled our climate-controlled precision inspection room, expanded the Quality Inspection team, and added a new larger Zeiss CMM machine.
  • Equipment build area — Because of the volume of recent spin rig orders, the equipment build & assembly area was relocated to a new section of the building. This update allows for new capabilities including improved setup and staging of the equipment builds and the ability to build three to four machines simultaneously. The improved build area also features an updated air supply and electrical supply for building and testing advanced machines.

Learn More

With an eye on quality services and constant innovation across everything we do, our Test Devices, Inc. team consistently strives to provide timely and efficient services to better meet our customers’ needs.

An industry-leading provider of spin testing and balancing services, Test Devices is thrilled to announce these new facility updates, which will allow us to better serve our ever-expanding client base.

For more information on these changes, or to discuss how we can help with your specific testing needs, contact the team today. We’re on hand to answer any questions you may have.

The Testing Capabilities of Subscale Jet Engine Rigs – Part 1

A full-scale jet engine test provides both engineers and designers valuable and realistic data for developing and improving the design and the performances of critical rotating parts and the jet engines. However, performing a full-scale engine test is typically is an expensive and technically complicated affair.

Small Jet Engine Testing Rig

Many engineers are still unaware of the various affordable engine test capabilities available through the use of subscale jet engines, such as oxidation/corrosion, creep/fatigue, blade high cycle fatigue (HCF), coating durability, fuel burn study, and volcanic ash/CMAS testing. In this blog, we’ll delve into oxidation & corrosion testing, creep & fatigue testing, and blade HCF testing in particular. For an in-depth look at the value of subscale testing in coating studies and oxidation and corrosion testing, be sure to check out the second part of this blog series, The Testing Capabilities of Subscale Jet Engine Rigs – Part 2.

Oxidation and Corrosion Testing

Oxidation — the reaction of oxygen in the gas stream with the surface coating or base metal of a part —  is the most common form of corrosion in aircraft engines. The result of chemical reactions by various elements of the engine core gas stream, corrosion causes the surface coating or base metal of a part to deteriorate. Corrosion can also be the result of galvanic action between mating parts.

Oxidation and corrosion testing can be done more conveniently in a small scale by using an engine, and there are several ways to perform it. One can design and make a surrogate test turbine disk/bladed disk to fit in a microturbine, place a test specimen (a tile specimen or a test blade) in the exhaust gas stream, or design an extended exhaust section for the off-the-shelf turbine as a test section. Or, within the test section, a test rotor can be spun in the exhaust gas stream (by an independent drive).

Creep and Fatigue Testing

Materials, after being subjected to high temperature over a duration time may “creep”; a type of damage mechanism that results in a permanent deformation and initiation of cracks. Study of thermo-mechanical fatigue (TMF), a damage mechanism that combines the effect of the creep and the fatigue cracking, has been an active field of research amongst the aerospace community for some time. The TMF occurs when thermal and mechanical stress are cyclically applied to a part, resulting in a type of damages that shortens the useful life of the engines and hard to predict.

While there are different types of test systems available to perform creep & TMF tests, many existing test systems, such as multi-axial tensile test rig, share the challenge of designing and manufacturing representative specimen that capture the intricate geometry and the features of complex high-temperature parts, for example, blades.  To further complicate the issue, the surfaces of high-temperature parts are often coated (EBC or TBC). Interaction of the coating system and the base material must be captured to accurately understand the failure mode.

By using appropriately scaled turbine blade/disk specimens and using a subscale engine as a test vehicle, such a test could provide an affordable way to study the complex failure mechanisms in more realistic and economical manner. Also, subscale engine tests can cost-efficiently combine the effect of combustion gas elements (corrosion and oxidation) with earlier mentioned heat and mechanical load effects.

Blade High Cycle Fatigue Testing

A blade failure could severely damage or destroy a jet engine, exposing the aircraft and its passengers to an extremely dangerous and often lethal situation. One of the critical blade failure mechanism is the high cycle fatigue (HCF). The HCF is driven by the cyclic load caused by the interaction between the operational loads on the blades and their dynamic responses. HCF could result in a crack and could cause a blade to fail in a very short duration of time.

Perhaps the most convenient and economical way to conduct a blade HCF test is by using a shaker table. Heating the blade helps to simulate the environment inside of the engine. However, shaker table tests severely limit the realism and it cannot capture the complex dynamics effects, such as the damping and response of CF loaded joints and traveling waves. To combine the effect of CF load to a shaker table test, engineers need to design a “representative” specimen shapes that can be mechanically pulled while retaining a “representative” dynamic response and loading conditions to the feature of interest.

Historically, HCF has been a more prevalent problem for fan and the blades in the cold stages of the turbines (compressor). Driven by the efforts in reducing the component weight and improving the compressor performances, testing of the high-pressure compressor and lower turbine blades in elevated temperature HCF environment has become an interest of study for some engine OEMs. Traditionally, thicker and stubbier high-pressure turbine blades have not been a subject of HCF, however, this may change with the emergence of extremely high-temperature capable materials, such as CMC, that could open the opportunities for designing a thinner, lighter hot section blade technologies that would significantly cut weight and boost performances.

A full-scale engine test would be a more realistic way to study HCF behavior but it would be very expensive. The use of a subscale engine could be a more affordable alternative – especially for a concept validation or R&D works. Subscale engine can be modified by using a purpose designed vanes, bladed rotor assemblies to study the HCF. Compare to the full-scale engine, it would be much easier to install and manage necessary sensors and instrumentation on a subscale engine. Spin testing might be a good option for HCF and blade dynamics testing, but we will leave this topic out for the interest of brevity of this blog.

The Benefits of Small Rig Testing

Subscale jet engine rig testing can be completed in a few months, whereas full-scale testing can take years. In fact, depending on number and complexity of tests required, most subscale testing can be completed in just two weeks. Easy customization provides an added bonus, enabling greater flexibility and quicker adjustments, and data from the tests are easier to compare with the model, allowing for greater insight into the condition of the engine. Also, these tests allow designs to be built from the ground up after engineers have a better understanding of test results — ensuring a top-quality, reliable design.

Learn More

To learn more about the benefits of small rig testing and the various jet engine testing capabilities available, download our free eBook, “The Importance of Subscale Jet Engine Testing.

 

Download Our Subscale Jet Engine Testing Guide

For information on how small-scale tests can help with your specific needs, contact our team of experts today.