Video Transcript
Introduction to Gas Turbines
Roberto Tabet:
Hello everyone, and thank you for attending this webinar on advanced gas turbine test benches.
A gas turbine is a continuous-combustion engine mainly used in applications such as high-capacity UAVs, aircraft, and stationary power generation.
It consists of four main components.
The first is the compressor, highlighted in blue, which draws air from the atmosphere and compresses it through multiple stages before delivering it to the combustion chamber.
Next is the combustion chamber, where combustion occurs and thermal energy is added to the system. Typically, liquid fuel, such as atomized kerosene at high pressure, is mixed with compressed air to provide the energy input.
The combustion chamber operates continuously. Once the flame is ignited by a spark plug, combustion is maintained until the engine is shut down.
Finally, we have the turbine, highlighted in red, where energy is extracted from the exhaust gases to drive the compressor. This area experiences the most extreme conditions in the engine. The turbine blades must withstand very high temperatures, pressures, and rotational speeds.
Types of Gas Turbine Engines
There are four main types of gas turbine engines.
The first is the turbojet, used primarily for sonic and supersonic flight applications. We will not focus on turbojets in this webinar, as they are mainly used for very high-speed applications.
The other three configurations are shown on this slide.
The first is the turbofan, commonly used for long-range flight due to its high efficiency at high speeds and excellent thrust-to-size ratio.
Next is the turboprop, where a gas turbine drives a propeller that generates thrust. This configuration is mainly used for medium-sized aircraft and offers excellent efficiency, low operating costs, and reduced fuel consumption at medium speeds.
The final configuration is the turboshaft, which is mainly used in helicopters and vertical take-off and landing UAVs. Here, the focus is on delivering shaft power to drive the rotor system while maintaining a compact design and low vibration levels.
Market Growth
Let's briefly look at market growth and the motivation behind developments in this field.
Significant growth is expected in the gas turbine market, particularly for microturbines below one megawatt. This market segment is projected to roughly double over the next decade, driven largely by UAV applications.
Heavy-lift UAVs are expected to be a major growth driver, particularly in regional logistics, cargo transport of up to 500 kilograms, and long-haul autonomous operations such as cargo helicopters.
When examining propulsion technologies, turbojet and turbofan microturbines are expected to grow moderately. However, the strongest growth is anticipated in turboshaft, turboprop, and hybrid turbine-electric systems over the coming decade.
Overview of a Gas Turbine Test Cell
Here we see an example of a gas turbine test cell, including photographs from an ongoing project involving a turboshaft engine.
The installation includes a hydraulic dynamometer as the load unit, an exhaust system, intake conditioning systems, ventilation equipment, and a control room.
One of the most interesting aspects of this project is that it was delivered as a containerized solution. It can be installed outdoors without requiring a dedicated building.
Although the example shown features a complete turboshaft engine, it is not the only application we support.
We can also test turboprops, which focus on shaft power. Turbofans, on the other hand, focus primarily on thrust generation. Therefore, complete turbofan testing requires different setups. However, individual turbofan or turbojet components such as compressors, combustion chambers, and turbines can be tested separately before the complete engine is assembled.
This helps engineers better understand component behavior early in the development process.
Testing can be performed under two main conditions:
- Ground testing at ambient pressure, temperature, and humidity.
- Simulated flight testing using altitude simulation systems.
Using our altitude simulation technology, we can reproduce flight conditions by controlling pressure, temperature, and humidity and simulating altitudes of 7,000, 8,000, or even 9,000 meters.
These tests can focus on performance boundaries, endurance testing, combustion chamber relight testing after shutdown, compressor power consumption, alternative fuel operation, and emissions evaluation.
While emissions legislation for these applications is currently limited, we expect regulatory requirements to increase in the future.
Survey Results
At this point, Roberto discussed the live audience survey.
The results showed that the majority of participants were interested in microturbine applications below one megawatt, which aligned closely with market growth projections.
A second survey focused on testing priorities. Most participants indicated an interest in full-performance testing of complete engines, with additional interest in idle-performance testing and in-flight relight testing.
Load Units and Dynamometers
One of the key components of a gas turbine test stand is the load unit.
We need a system capable of absorbing power generated by the engine and, in some situations, motoring the engine as well.
Several options are available:
AC Dynamometers
These systems provide:
- High torque and speed capability
- Low inertia
- Dynamic testing capability
- Motoring and loading functions
- High measurement accuracy
HORIBA offers several AC dynamometer variants, including:
- High-speed series
- Low-inertia series
- High-torque series
- Heavy-duty series
Each is optimized for specific applications ranging from electric vehicles and race cars to heavy-duty diesel engines.
Hydraulic Dynamometers
Hydraulic dynamometers are widely used for steady-state testing.
They provide:
- Extremely high torque capacity
- Broad power ranges
- Robust operation
They are ideal for durability testing, acceptance testing, and engine performance mapping.
Tandem Dynamometers
The tandem solution combines an AC dynamometer with a hydraulic dynamometer.
This offers:
- High steady-state power capability
- Dynamic testing functions
- Motoring capability
- Reduced facility power demand
The tandem setup supports engines from approximately 300 kW up to more than 12 MW.
E-Motor Dynamometers
E-motor dynamometers operate on a similar principle to AC dynamometers but are optimized for much higher rotational speeds.
These systems support applications such as:
- Electric vehicles
- Racing applications
- Construction equipment
- Marine systems
- Aircraft
- UAVs
Gearboxes can also be incorporated when speed requirements exceed direct dynamometer capabilities.
Fuel Supply Systems
To operate an engine, fuel must be supplied accurately.
HORIBA offers:
FQ Liquid Fuel Systems
These systems support:
- Diesel
- Gasoline
- Kerosene
- SAF
- Biodiesel
Capabilities include:
- Flow rates up to 1,000 L/h
- Fuel temperatures up to 80°C
- Stationary and transient testing
HyFQ Gas Fuel Systems
Designed primarily for hydrogen applications, these systems can also be adapted for gaseous fuels such as:
The system consists of:
- A main control unit
- A DUT unit installed close to the test specimen
This arrangement maximizes pressure and temperature control accuracy.
Hydrogen Safety
Hydrogen applications require special safety precautions because gas leaks cannot be visually detected.
HORIBA recommends:
- Continuous hydrogen concentration monitoring
- Proper test cell ventilation
- Local extraction systems above potential leak locations
- Automatic shutdown procedures
Hydrogen sensors are installed around critical areas such as fuel supply units and the test specimen.
If unsafe concentrations are detected, safety systems automatically isolate the fuel source, shut down the installation, and evacuate accumulated gas.
Altitude Simulation (MEDAS)
The MEDAS altitude simulation system allows reproduction of flight conditions inside a test cell.
Capabilities include:
- Altitudes up to 9,000 meters
- Temperature control from -35°C to +50°C
- Humidity control
- Airflow rates up to 5,200 kg/h per unit
Multiple MEDAS systems can be connected in parallel to support higher airflow demands.
Flight scenarios including ascent, descent, airport conditions, seasonal variations, and cloud passage can all be simulated.
Automation and Integration
To coordinate all test stand components, HORIBA uses the STARS automation platform.
Key benefits include:
- Integration of HORIBA and third-party equipment
- Centralized data management
- Unified reporting
- Scalable architecture
- Industry-standard communication interfaces
The platform supports protocols such as:
- EtherCAT
- CAN
- LAN
- ASAM-compatible systems
Security functions can also be customized according to project requirements.
Project Examples
Roberto concluded by presenting two examples.
Helicopter Turbine Test Bench
This project focused on performance testing of a helicopter turboshaft engine.
Features included:
- Tandem dynamometer solution
- 2.4 MW power capability
- 27,500 rpm speed capacity
Helicopter Autorotation Test Bench
This project focused on analyzing helicopter rotor autorotation behavior during emergency conditions.
Features included:
- Gearbox system
- 26,000 rpm operating speed
- Two 1.5 MW outputs
- Simultaneous testing of two specimens
Closing Remarks
In summary, I'd like you to take away three key messages from today's webinar:
- HORIBA provides flexible and highly customizable test solutions.
- We have extensive global experience delivering gas turbine test facilities.
- Our worldwide service and support network helps customers achieve their testing objectives efficiently and reliably.
Thank you very much for your attention.
Q&A Session
"What safety measures are implemented in the test cell for hydrogen testing, and how does the system react when hydrogen concentration reaches an ATEX threshold?"
As mentioned during the presentation, it is crucial to ensure that hydrogen concentrations never reach explosive or otherwise dangerous levels.
Making an entire test cell ATEX-certified is generally not practical because of the associated costs and complexity. Instead, we focus on preventing explosive atmospheres from forming in the first place.
This is achieved through two key measures:
- Proper ventilation throughout the test cell to prevent the accumulation of hydrogen.
- Continuous monitoring using hydrogen sensors strategically placed around the installation to detect any leaks.
If a dangerous concentration is detected, our standard safety threshold is set at 50% of the Lower Explosion Limit (LEL). For hydrogen, this corresponds to approximately 2% concentration.
Once that threshold is reached, all non-ATEX-certified equipment is automatically shut down and powered off to eliminate any potential ignition sources.
At the same time, the ventilation systems in the test cell and the extraction units associated with systems such as MEDAS are activated to remove accumulated hydrogen safely.
These ventilation and extraction systems themselves must be ATEX-compliant to ensure safe operation under emergency conditions.
"Has HORIBA assisted customers with combustion chamber testing for jet engines, and if so, could you provide some insight into the sampling probe used?"
If by "sampling probe" you are referring to emissions measurement, then yes, we do have experience testing combustion chambers for jet engines.
These tests can be carried out using either the engine's own compressor or an external compressor to provide the required boost pressure. We also control the back pressure to maintain the desired combustion chamber conditions and supply the fuel necessary to analyze combustion behavior and flame characteristics.
Regarding emissions measurements specifically, this is currently an area of ongoing development.
Our present approach focuses on sampling in the exhaust stream rather than directly within the combustion chamber itself.
The objective is to perform measurements without dilution. However, because exhaust temperatures can be extremely high, especially in jet-engine applications, this presents significant engineering challenges.
The technology is still under development and is not yet commercially available, but it is an area we are actively working on.
Thank you again for joining us today. Have a great day, and we look forward to seeing you again at a future webinar.
