Final Report Summary - BESTT (Development, Construction and Integration of Bench Systems for Ground Thermal Tests)
Executive Summary:
The general objective of this part of the Eco-Design ITD was to make a significant step towards the concept of the all-electric vehicle system aircraft. Thus the feasibility of such an aircraft has to be investigated through the study of innovative energy management architectures while reducing ground and flight tests with innovative concepts and technologies.
To develop, validate and finally demonstrate these energy management architectures a ground thermal test bench was installed based on the use of aircraft representative fuselages including various typical areas to cover the problems encountered for the thermal modelling. To achieve this the ground thermal test bench was planned to consist of three fuselage mock-ups containing equipment, representing the thermal dissipation of the aircraft systems, and an ancillary thermal bench element with modular measurement and calibration capability.
As the required boundary conditions of the bench equipment are very extreme concerning temperatures, humidification and pressure, the work within BESTT was allocated within seven work packages which lifted the current know-how and demands for technological solutions step-by-step to a new innovative level. The consortium, consisting of three experienced companies covered the capabilities of developing and implementing a complex test bench by their experience in the field of manufacturing and standardisation (TEMES), modelling and engineering of complex plants (Modelon) and development and implementation of complex test benches (Streit).
With this consortium three strong expert companies worked together on the development of a step-change test environment for future technologies especially the more-electric aircraft. The consortium was managed by STREIT, which is an experienced engineering and plant constructing company that already participated successfully in two FP projects.
Project Context and Objectives:
The work within BESTT was allocated within seven work packages which lifted the current know-how and demands for technological solutions step-by-step to a new innovative level. The consortium, consisting of three experienced companies covers the capabilities of developing and implementing a complex test bench by their experience in the field of manufacturing and standardisation (TEMES), modelling and engineering of complex plants (Modelon) and development and implementation of complex test benches (Streit).
Within the first work package “Development and Design” all important parameters for the detailed design, the construction and the integration of the test equipment were gathered and evaluated. Based on these results, the development of possible solutions has been executed. The development process was created by this interdisciplinary expert consortium in an innovative iterative way which means, that short development cycles have gone through the evaluation of an industrial manufacturer, a specialist company for test bench construction and a modelling experts company that was the mathematic backbone on the way to the best solutions. With the models incorporated in the modelica air-conditioning-library a broad range of possible solutions for the air- conditioning unit was assessed in order to identify the most promising ones. The library incorporates models of gascooler, heat exchangers, compressors, valves, receivers, etc. and provides the thermodynamic state of most of the fluids commonly used in air conditioning units. Modelons results from these simulations together with the field expertise of TEMES and Streit enabled the consortium to do quick review cycles and to have the possibility of short time reactions to different developments and technological findings.
Based on the results of the first work package a detailed planning process was executed in WP2 “Design”. In this process the components of the test environment have been calculated and selected. Iterative self-control mechanisms by modelling and engineering approach ensured best solutions and prevented errors and insufficient number of competitive suppliers. Specification sheets were prepared as a basis for the scope of work and for the tender documents to be handed out to possible suppliers of materials, components and subcontracted parts. Tenders were evaluated and suppliers for material, components and subcontracts were selected. Due to expected long delivery times for special components, in this early stage the first orders of time-critical components got triggered early in the project.
As the required boundary conditions of the bench equipment are very extreme concerning temperatures, humidification and pressure, certain parts of the equipment had to be subcontracted to the special requirements in WP3 “Construction”. The suppliers ́ construction processes of different components like e.g. the special refrigeration system, the special ventilation system or the special air condition for fuselage parts and the Aircraft Calorimeter (ACC) was strictly monitored and quality controlled by the partners. Each partner assumed responsibility for his special application fields or carried out the construction works in his scope himself.
After the construction of the different custom parts in WP3, the integration of these components into the test facility has been carried out. Therefore the parts will were delivered to the test facility, integrated into the test environment with its pressurized steel chamber and the technical area. All the components then were connected to the different supply lines like electrical power, waste heat system, fresh water system, etc. For the operational control of the test bench, a comprehensive and safe control system based on the internationally standardized software Siemens DESIGO and its control modules has been implemented and programmed.
To guarantee the operational functionality of the test bench, extensive operational testings were carried out in collaboration with the EDS WP4 member, to meet theri requirements regarding the future bench test scenarios in WP5 “Operational testing”. It was guaranteed, that the quality of the whole test bench met the defined requirements of WP1 and WP2.
BESTT clearly addresses all topics addressed in the call. The project will enhance the possibilities for European manufacturers and suppliers to develop, test and validate new concepts and equipment located in the aircraft environment. This can be equipment for both existing and future aircraft. Besides, the procedures and installations proposed can be transferred to other high- technology areas, such as the rail sector or power plants.
Project Results:
Streit:
Development, Design, Construction and Integration of:
• 2 mock-up fuselage parts (carbon fibre and aluminium) with simulated hot and cold air layer around to simulate high altitude and hot on ground situations
• development of a heat exchange plate system (HEP) to enable air and radiation layers around the fuselage parts
• development of the ATU principle, an air treatment principle to enable short reaction times of air conditioning systems for simulation environments
• construction and integration of a gas tight vacuum resistant lead through construction for high and low temperature ventilation applications
• development, design and construction of the ACC Aircraft Calorimeter, a low pressure chamber with 50 cbm volume to simulate flight conditions at altitudes up to equivalent of 2 mbar absolute pressure, simultaneously conditioning the inside from -60°C to +120°C
Mock-up:
For the T12 fuselage part, a cocoon construction was designed to bear the load of the fuselage and to enable a defined air layer around the fuselage. Additional requirements from the measurement and test side desired a removable metal cladding around the fuselage due to the accessibility of numerous flow and temperature sensors that will be installed
The cocoon was transported onto the lower installation platform and was measured to determine the position of later bearing construction points.
Included was the design of the cocoon air supply system that consists of a piping system with integrated low temperature cooling heat exchanger and a bypass-system with optional heating capabilities to set the environmental boundary conditions of the fuselage. For this a complex air distribution system for the fuselage was designed. From the original design, a simple radial flow around the fuselage, significant changes were elaborated. The air distribution around the fuselage was completely changed, the inlet and outlet situation was CFD calculated and based on these calculations, complex welding constructions were be made to meet the stated requirements of the test bench.
For the environmental boundary condition simulation, a defined air layer has to be blown around the fuselage. Coming from the original idea with radial airflow, the change requests lead to a design with a longitudinal airflow, an inlet manifold at the back, an outlet funnel construction on the front an a changing air gap rate along the fuselage.
A special fan of stainless steel had to be designed and constructed to stand the -65°C possible temperature and to be able to overcome the expected pressure drop at 10.500 cbm/h
HEP:
During the design phase, the idea of a special heat exchanger with heat convection and heat conduction ratios was developed by Streit. The system was named HEP (Heat exchange plates) concept.
Extruded aluminium profiles were installed in a Tichelmann system for the best possible heat distribution along the completed heat exchanger.
A small first prototype was followed by a realistic prototype for first tests and measurements of the possible performance data. Due to the low delta T that is available by the current CCU solution, the concept was changed to a pure air system with defined air gaps around the fuselage. Therefore the T12 Cocoon recirculation system will be used for the surface cooling of the T23 mock-up.
The prototype work including the complete development of the system was carried out by Streit. We provided also the necessary cooling/ heating machine so that IIBP could build up their measurement equipment and do the performance measurements.
ATU:
A major requirements difference to all common air conditioning units is the very low air volume of the fuselage parts and the connecting pipes and air treatment components. At the same time, the loads are high regarding thermal loads, humidity of the air and the control of the volumetric air flow.
Standard air conditioning units are working in a sequential way as they do have relatively small changes of their loads and are usually running with smaller deviations of the desired values.
A standard air conditioning has not been considered a promising solution.
As the standard air conditioning solution could not fulfil the requirements of the air treatment for the T12 fuselage, an innovative air treatment unit was designed.
The innovative approach of the designed air treatment unit is to reduce and even blind out the thermal inertia of the components on the system and to raise the reaction times of the unit by connecting the single components in a parallel way and to keep them permanently in a “stand-by” state. The objective was to use standard components from the air conditioning industry, modify them of necessary and interconnect them to a compact unit.
From the management station, the desired set-points for the air conditions are entered. The central control system then will control the different components of the ATU to achieve these desired values.
When the system is started, the “stand-by” mode will be activated, that means that:
- the ATU central cooling unit is in operation and cooling the buffer to its setpoint
- the electric heating circuit is working on the set internal constant temperature
- the adsorption dryer is in operation and the precooler is supplying the dryer with cold air
- the air cooler is in operation and being supplied with cold glycol from the central cooling unit for the ATUs
After all components have reached their operational state, it will be possible to start the main system for the fuselage supply, that means, that the supply fan will ramp-up and the flap valves will start to control the desired volume flows.
Lead through:
A gas tight lead through for the ACC was constructed. It allows low pressure and low temperature operation of the ACC with the electrical motor beeing outside the ACC in normal conditions. This enables the ACC to operate from -60°C to +120 °C at nearly 0 bar absolute pressure and 10.500 cbm/ h recirc air.
ACC:
For the ACC the construction of a 1-zone model was decided. It was preferred because of the more flexible interior space, better thermal manageability and the possibility to test bigger specimen.
The vessel geometry was selected by the technical advantages of a cylindrical system, especially when considering the planned low pressure operations.
Therefore a cylindrical steel vessel was designed with the following properties:
length: 6500mm
diameter: 3200mm
insulation thickness: 150mm
weight 16 tons
For the thermal insulation of the ACC, a material had to be found, that is resistant to the low temperatures as well as to the high temperatures.
Another very critical influence is coming from the vacuum operation conditions, especially from the rapid decompression scenarios.
A PIR material was selected, based on Polyurethane materials, that can be shape by milling and CNC cutting into the shape of the round vessel. Conglutination with special 2K- material.
For the coating of the abrasive PIR material, a Polyuera material was chosen, that can be spray applied to the surface of the PIR material. When finaling testing the Polyurea material under hot conditions and following rapid evacuation in our small vacuum chamber, the Polyuera material separated from the PIR material.
A new solution had to be worked out.
Due to the low thermal mass and the near term availability of the material, an aluminium coating for the complete inner space of the ACC was selected and applied to the PIR material. Linear expansions due to the big temperature differences had to be considered and were constructively considered by using a special plastic material under each bolt as a slide bearing.
For the desired low temperatures and the planned thermal shock conditions an air cooler was designed and constructed for the use with thermal oil provided by the CCU.
The boundary conditions were 30kW @-65°C oil temperature and 10000 cbm/h of circulated air.
Due to the mass of 700 kg, a steel support was constructed to bear the load of the cooler and distribute it along the grating subconstruction.
Temes:
Temes main responsibility within the BESTT consortium was the development an construction or the Central Cooling Unit (CCU), the R245FA Cooling unit for the heater supply, the High Current Power Supply and related printed circuit boards. Furthermore Temes was responsible to design the ACC components: High current / High Energy Density Heating Elements along with a new connector system.
CCU:
The CCU = Central Cooling Unit comprises two cooling units (CU), working in parallel. Each cooling unit is equipped with
− four cooling machine modules
− one cooling oil storage vessel, filled with 1.700 l oil. The vessel is fed by the four cooling machine modules. Purpose of the oil: Providing high peak cooling capacity when changing the chamber temperature status from hot to cold.
A further vessel is used as expansion tank.
Each cooling machine module KMM507 provides a refrigerating capacity of 5 kW at -65 °C. As refrigerant R507 is used allowing this low temperature.
Four modules KMM507 are mounted on a common frame and working in parallel, providing max. refrigerating capacity of 20 kW at -65 °C. The modules cool the cooling oil which is stored in the cooling oil pressure vessel. This arrangement forms the cooling unit (CU).
Two cooling units CU form the central cooling unit (CCU). The CCU provides max. refrigerating capacity of 40 kW at -65 °C. For safety reasons (environmental pollution) the CCU is located within a safety pan. The pan is dimensioned for the complete amount of cooling oil.
The cooling oil vessel has a capacity of appr. 1.700 l. The cooling oil works as cold storage.
The expansion vessel compensates works as compensation volume which is required due to the different volumes of the cooling oil, depending on its temperature.
In compliance to the ongoing change management needs through the integration phase until April 2014, because not all connecting systems (e.g. ACC designs and T23 compartment) could be finalized and accepted with the FHG IBP and the BESTT consortium in a short time range (until April 2014), Temes had to change in different steps the scheduling, workload and work flow for the CCU system as well as the documentation (see picture below, as one point in the change management, e.g. CDR documentation).
The Central Cooling Unit (CCU) was successfully integrated in the FHG Test field and completely checked by 2 different external test authorities:
- TÜV Nord Essen checked all electrical realization works and the electrical definition files and drawings
- TÜV Süd “safety department” Munich defines in a HAZOP-Meeting and Report to all safety issues
- TÜV Süd “department for cooling system and conformity” Munich checked all realization works and safety reports in a step-by-step-reporting including the reporting to the results through the HAZOP- Meeting.
The Central Cooling Unit was successfully integrated in the FHG IBP area and there Benches and completely accepted from the German Test Authorities as well by step-by-step reportings.
The CCU uses Therminol D12 a cold storage medium. Appr. 4.600 l cooling oil are used.
The Central Cooling Unit uses R507 as refrigerant.
This refrigerant is suitable for temperatures down to -75 °C.
ACC heater:
The ACC heater is used to rapidly heat up the air in the ACC test chamber. A voltage converter provides up to 120 kW electrical power for the heater. The power electronics components of the voltage converter are mounted on water cooled heat sinks. The cooling water absorbs the waste heat dissipated by the power electronics.
The 2.5-m3 storage tank works as a heat buffer.
To cool the water in the storage tank a 25-kW cooling unit (refrigerant: R245fa) is provided.
The R245fa unit transfers the heat to the test facility's recooling circuit, dissipating the heat to the environmental air using a cooling tower.
The R245fa cooling unit including the tank was delivered to the FHG IBP and is ready for integration to the FHG IBP environment since Sept. 2013, but is isn’t foreseen to integrate this in this program yet, because of the budget needs at BESTT-program.
R245fa unit:
This cooling unit is used to cool the water of the 2.500-l storage tank. The water absorbs the heat dissipated by the heat sinks of the high current power supply for the ACC heater.
The future advantages of the R245fa cooling units for cooling properties e.g. FUEL CELL systems including high power electronics for aeronautics and special application we shown within this project.
Power supply:
The heater supply rack is capable to supply 2.700 A max. at 50 V max.
The step down chopper is located in the heater supply rack.
Four double IGBT modules V1 to V4 are working in interleaved mode to switch the input voltage to the output. Only the upper IGBT's are switched when working for the heating.
Each part current is measured by its own current sensor (B1 to B4). Additionally, the total current is measured by sensor B5.
The new developed and realized high current power supply was tested and fully operable and fulfilled all defined specification points.
Advantages: 180 to 200kWs energy storage versus 50 to 70 kWs state of the art
The 5 heating units are ready for integration.
Connector system:
One of the biggest problems in state-of-the-art-power electronic system is the connection between power electronic modules and the environment or the connection between systems.
So, a unique connector system was designed and developed to uphold the parameters for aeronautic equipment and power electronic modules according to the electrical net specifications as well as the mechanical and environmental specifications.
Advantages/target:
1. weight reducing up to 50-60% vs. state of the art, readiness and operability for aeronautic applications
2. High-current contacts
3. IP69
4. High-temperature operability vs. high current and/or high voltage possibilities
5. Loss reducing contacts vs. readiness for aeronautic applications
These finalized designs for the connectors were build as first Prototypes. These Prototypes were fulfilling all electric specification points, but not all Environmental and Weight Needs.
So in the construction phase these points were defined and prototyped in a hybrid manufacturing process with milling and injection molding machines for the first Prototypes.
Through the construction phase of the new designed connectors a lot of problems occur through structure complexity in the connectors and their state-of-the-art-production of connectors.
Modelon:
Use cases for the BESTT project
For each use-case different simulation models with varying and appropriate degrees of detail are required. In order to prepare these models the relevant use-cases have been identified with the different project partners.
For the design phase the following use-cases have been ascertained to be the most relevant.
• Verifying calculation for the plant dimensioning (ATU)
• Virtual comissioning (ATU)
• Control parameter optimization (ATU)
• Verifying calculation for the plant dimensioning (CCU)
• Evaluation of conditioning duration for test procedures (CCU)
• Development of control strategies for air handling (CCU)
Models
Overview
All of the models being developed by Modelon during the project were packaged in a new library for the simulation of cooling systems, the so called “BESTT-Library”. The models were developed using Dymola 2014 with Modelica 3.2. Also required are the commercial libraries AirConditioningLibrary 1.8.4 ModelonLibrary 1.8 and ThermoFluidPro 1.8.4 library.
The various subsystems have been designed to be very modular in order to easily pick and mix the components to ideally suit all manner of problems, thereby reducing the overall complexity and improving simulation performance.
Air treatment unit model
The air treatment units (ATU) are used to condition the mass flow, temperature and humidity of the inlet air of the fuselage mockups. Due to the innovative parallel setup of the components and short air paths the design of the control is quite demanding. The ATU model covers all air ducts, the heater, the cooler, the dryer, the fan and all necessary valves, sensors and control units. It can be used stand alone or in combination with other models like the CCU model.
As far as possible the ATU-model uses standard components from the AirConditioningLibrary, but for several components the development of specific submodels was necessary. Amongst others these mainly include the heater, cooler and air dehydrator with their respective controls and test benches. A notable numerical and simulation challenge was the development of an interface in order to manipulate the humidity rating of air.
Central cooling unit model
The central cooling unit CCU is used to provide cooling oil at temperatures down to -66°C for the thermal test bench. The cool oil is stored in two insulated tanks with several outlets to the thermal test bench. For the cooling down of the oil four parallel single cooling units are combined for each tank as can be seen in the model in figure 2.
The modelling is done as far as possible by using standard components from the Modelon library with appropriate parameters. For performance reasons the cooling units were implemented following a map based approach with maps created by the Bitzer software 6.3.
Flight test facility model
Models for the fuselage mockups at a high level of details were already available but could not be used for performance reasons. For the usage in combination with the CCU and the ATU model simple, fast and generic fuselage mockup models were developed and parameterized.
Simulation study: influence of the isolation thickness
All of the above-mentioned use cases can be evaluated with the current modelling state. In this paper a typical examples for the usage of the Bestt-Library is presented.
In this simulation experiment the CCU is running at full load and the cooling units cool down the oil in the tank. After one hour a heat load is applied to the test facility connected to the tank. The red curve shows the temperature in the tank with the assumption of ideal insulated components (tank, pipes). In further experiments the thickness of the insulation material of the pipes connecting tanks and cooling machines is varied. The curves show the influence of the thickness of the isolation material (green: 1cm, blue: 1.5cm pink: 2cm) on the tank temperature.
Potential Impact:
ATU: The ATU principle will enable high accuracy environmental simulation systems to deliver better results in transient system simulations. It will help to reduce simulation times and reduce inflight tests due to realisitic scenarios on ground.
Other industries will also profit from this very accurate air conditioning systems, especially laboratories and test environments.
ACC: The ACC is a test bench to simultaneously test high altitude and extreme temperature situations for large systems. By this, inflight tests can be reduced and development times can be shortened.
Central Cooling Unit at -65°C:
In future test bench areas, in compliance with new aeronautic standards, it will be necessary to cool down environments and test configurations below – 55°C, so there is a very high interest from test facilities for new cooling systems, which are able to convert very low temperatures with compressor- based machine systems, like the CCU.
R245fa cooling unit:
The future advantages of the R245fa cooling units for cooling properties e.g. FUEL CELL systems including high power electronics for aeronautics and special application we shown within this project.
High current high power system as heating system:
The future advantages of the high current power systems are very sufficient for heating applications in future test bench areas as well as converter systems in FUEL CELL programs for aeronautics and special application we shown within this project.
New connector units for high power systems:
First prototypes very build, but for the ACC integration these connectors are not feasible.
It is necessary in a further development program to invest in high-grade flexible tools to produce connector sets, which are convenient and next to a series connector sets in a state-of-the-art- production line, without any special tooling or separate hybrid production process.
Modelling:
With the developed models, design cycles of environmental simulation systems can be shortened. Especially for the ATU systems, the models can be used to predict the right control strategies.
Within plant engineering system simulation can be used as a powerful tool for dimensioning of plants, the development of control strategies and the testing of control algorithms. Comprehensive commercial simulation tools and model libraries are available on the market. Unfortunately these tools are comparatively expensive in purchase and require specific numerical know-how. That is one reason why system simulation isn’t widely adopted especially in smaller organisations. During the project a workflow for the compilation of licence-free models and the stand-alone execution of this models was developed. The solution is based on the open FMI-standard for the exchange of simulation models.
This workflow makes it possible to outsource the development and validation of simulation models to specialised organizations with the appropriate tools and resources. A technical expert of the plant design company using a case-specific user interface then performs the actual simulation study. This way especially small companies can avoid to hold available costly and highly specific resources but use the advantages of system simulation
The project will enhance the possibilities for European manufacturers and suppliers to develop, test and validate new concepts and equipment located in the aircraft environment. This can be equipment for both existing and future aircraft. Besides, the procedures and installations proposed can be transferred to other high-technology areas, such as the rail sector or power plants.
When aiming at all-electric aircraft architectures thermal issues will become critical inside the pressured fuselage and thus will be a main differentiator in aviation industry. Means to handle and test these critical energy fluxes correctly will therefore contribute to strengthen the competitiveness of the European aviation industry and its suppliers.
Thus BESTT improves not only the product range and applicability of the participating manufacturers but even the reputation of the partners as partners for the aviation industry.
Generally RTD activities are considered by the partners as the basis of sustainable growth in the highly innovative aviation sector, especially for those partners that have their core business in research and innovation development.
BESTT brings together manufacturers and suppliers of aircraft equipment as well as experts in simulation, testing and test bench installation. The consortium elaborated a synergistic way forward to develop new technologies for ground thermal tests as well as their simulation environment. Experimental testing validated both the technology itself as well as the simulation environment falling back on the data gained through the operational testing. Thus the industry can fall back onto a very solid basis for their further development of BESTT technologies for aircraft application. To meet the end-users requirements the close cooperation with the EDS WP4 members delivered the needed input to achieve this impact.This project provided knowledge, operational recommendations, prepared validated technological concepts for implementation of future aircraft testing guidelines, recommendations and European pre-standards, and design guidance for manufacturers, all leading to more competitive aircraft. Public demand for safer and more comfortable aircraft cabins will be met, which would otherwise be heightened by the continued growth in demand for air travel. Through BESTT, European manufacturers will be in a position to anticipate regulations and technical improvements and thereby offer more competitive aircraft in the future, to the benefit of consumers and manufacturers alike.
List of Websites:
www.bestt.eu
Alexander Streit – Coordinator
Streit-TGA GmbH & Co. KG
Bergfeldstraße 1
83607 Holzkirchen
Germany
as@streit-tga.de
Tel. +49 8024 470 274-0
Fax.+49 8024 470 274-9
www.streit-tga.com
Emmeram Klotz
Modelon GmbH München
Agnes Pockels-Bogen 1
80992 München
Germany
emmeram.klotz@modelon.com
Telefon +49 89 416142040
www.modelon.com
Maik Hohmann
Division Manager
Temes Engineering GmbH
Birkerfeld 53
83627 Warngau
Germany
maik.hohmann@temesonline.de
Tel.: +49 (0)8024 473 88 16
Fax: +49 (0)8024 473 88 26
The general objective of this part of the Eco-Design ITD was to make a significant step towards the concept of the all-electric vehicle system aircraft. Thus the feasibility of such an aircraft has to be investigated through the study of innovative energy management architectures while reducing ground and flight tests with innovative concepts and technologies.
To develop, validate and finally demonstrate these energy management architectures a ground thermal test bench was installed based on the use of aircraft representative fuselages including various typical areas to cover the problems encountered for the thermal modelling. To achieve this the ground thermal test bench was planned to consist of three fuselage mock-ups containing equipment, representing the thermal dissipation of the aircraft systems, and an ancillary thermal bench element with modular measurement and calibration capability.
As the required boundary conditions of the bench equipment are very extreme concerning temperatures, humidification and pressure, the work within BESTT was allocated within seven work packages which lifted the current know-how and demands for technological solutions step-by-step to a new innovative level. The consortium, consisting of three experienced companies covered the capabilities of developing and implementing a complex test bench by their experience in the field of manufacturing and standardisation (TEMES), modelling and engineering of complex plants (Modelon) and development and implementation of complex test benches (Streit).
With this consortium three strong expert companies worked together on the development of a step-change test environment for future technologies especially the more-electric aircraft. The consortium was managed by STREIT, which is an experienced engineering and plant constructing company that already participated successfully in two FP projects.
Project Context and Objectives:
The work within BESTT was allocated within seven work packages which lifted the current know-how and demands for technological solutions step-by-step to a new innovative level. The consortium, consisting of three experienced companies covers the capabilities of developing and implementing a complex test bench by their experience in the field of manufacturing and standardisation (TEMES), modelling and engineering of complex plants (Modelon) and development and implementation of complex test benches (Streit).
Within the first work package “Development and Design” all important parameters for the detailed design, the construction and the integration of the test equipment were gathered and evaluated. Based on these results, the development of possible solutions has been executed. The development process was created by this interdisciplinary expert consortium in an innovative iterative way which means, that short development cycles have gone through the evaluation of an industrial manufacturer, a specialist company for test bench construction and a modelling experts company that was the mathematic backbone on the way to the best solutions. With the models incorporated in the modelica air-conditioning-library a broad range of possible solutions for the air- conditioning unit was assessed in order to identify the most promising ones. The library incorporates models of gascooler, heat exchangers, compressors, valves, receivers, etc. and provides the thermodynamic state of most of the fluids commonly used in air conditioning units. Modelons results from these simulations together with the field expertise of TEMES and Streit enabled the consortium to do quick review cycles and to have the possibility of short time reactions to different developments and technological findings.
Based on the results of the first work package a detailed planning process was executed in WP2 “Design”. In this process the components of the test environment have been calculated and selected. Iterative self-control mechanisms by modelling and engineering approach ensured best solutions and prevented errors and insufficient number of competitive suppliers. Specification sheets were prepared as a basis for the scope of work and for the tender documents to be handed out to possible suppliers of materials, components and subcontracted parts. Tenders were evaluated and suppliers for material, components and subcontracts were selected. Due to expected long delivery times for special components, in this early stage the first orders of time-critical components got triggered early in the project.
As the required boundary conditions of the bench equipment are very extreme concerning temperatures, humidification and pressure, certain parts of the equipment had to be subcontracted to the special requirements in WP3 “Construction”. The suppliers ́ construction processes of different components like e.g. the special refrigeration system, the special ventilation system or the special air condition for fuselage parts and the Aircraft Calorimeter (ACC) was strictly monitored and quality controlled by the partners. Each partner assumed responsibility for his special application fields or carried out the construction works in his scope himself.
After the construction of the different custom parts in WP3, the integration of these components into the test facility has been carried out. Therefore the parts will were delivered to the test facility, integrated into the test environment with its pressurized steel chamber and the technical area. All the components then were connected to the different supply lines like electrical power, waste heat system, fresh water system, etc. For the operational control of the test bench, a comprehensive and safe control system based on the internationally standardized software Siemens DESIGO and its control modules has been implemented and programmed.
To guarantee the operational functionality of the test bench, extensive operational testings were carried out in collaboration with the EDS WP4 member, to meet theri requirements regarding the future bench test scenarios in WP5 “Operational testing”. It was guaranteed, that the quality of the whole test bench met the defined requirements of WP1 and WP2.
BESTT clearly addresses all topics addressed in the call. The project will enhance the possibilities for European manufacturers and suppliers to develop, test and validate new concepts and equipment located in the aircraft environment. This can be equipment for both existing and future aircraft. Besides, the procedures and installations proposed can be transferred to other high- technology areas, such as the rail sector or power plants.
Project Results:
Streit:
Development, Design, Construction and Integration of:
• 2 mock-up fuselage parts (carbon fibre and aluminium) with simulated hot and cold air layer around to simulate high altitude and hot on ground situations
• development of a heat exchange plate system (HEP) to enable air and radiation layers around the fuselage parts
• development of the ATU principle, an air treatment principle to enable short reaction times of air conditioning systems for simulation environments
• construction and integration of a gas tight vacuum resistant lead through construction for high and low temperature ventilation applications
• development, design and construction of the ACC Aircraft Calorimeter, a low pressure chamber with 50 cbm volume to simulate flight conditions at altitudes up to equivalent of 2 mbar absolute pressure, simultaneously conditioning the inside from -60°C to +120°C
Mock-up:
For the T12 fuselage part, a cocoon construction was designed to bear the load of the fuselage and to enable a defined air layer around the fuselage. Additional requirements from the measurement and test side desired a removable metal cladding around the fuselage due to the accessibility of numerous flow and temperature sensors that will be installed
The cocoon was transported onto the lower installation platform and was measured to determine the position of later bearing construction points.
Included was the design of the cocoon air supply system that consists of a piping system with integrated low temperature cooling heat exchanger and a bypass-system with optional heating capabilities to set the environmental boundary conditions of the fuselage. For this a complex air distribution system for the fuselage was designed. From the original design, a simple radial flow around the fuselage, significant changes were elaborated. The air distribution around the fuselage was completely changed, the inlet and outlet situation was CFD calculated and based on these calculations, complex welding constructions were be made to meet the stated requirements of the test bench.
For the environmental boundary condition simulation, a defined air layer has to be blown around the fuselage. Coming from the original idea with radial airflow, the change requests lead to a design with a longitudinal airflow, an inlet manifold at the back, an outlet funnel construction on the front an a changing air gap rate along the fuselage.
A special fan of stainless steel had to be designed and constructed to stand the -65°C possible temperature and to be able to overcome the expected pressure drop at 10.500 cbm/h
HEP:
During the design phase, the idea of a special heat exchanger with heat convection and heat conduction ratios was developed by Streit. The system was named HEP (Heat exchange plates) concept.
Extruded aluminium profiles were installed in a Tichelmann system for the best possible heat distribution along the completed heat exchanger.
A small first prototype was followed by a realistic prototype for first tests and measurements of the possible performance data. Due to the low delta T that is available by the current CCU solution, the concept was changed to a pure air system with defined air gaps around the fuselage. Therefore the T12 Cocoon recirculation system will be used for the surface cooling of the T23 mock-up.
The prototype work including the complete development of the system was carried out by Streit. We provided also the necessary cooling/ heating machine so that IIBP could build up their measurement equipment and do the performance measurements.
ATU:
A major requirements difference to all common air conditioning units is the very low air volume of the fuselage parts and the connecting pipes and air treatment components. At the same time, the loads are high regarding thermal loads, humidity of the air and the control of the volumetric air flow.
Standard air conditioning units are working in a sequential way as they do have relatively small changes of their loads and are usually running with smaller deviations of the desired values.
A standard air conditioning has not been considered a promising solution.
As the standard air conditioning solution could not fulfil the requirements of the air treatment for the T12 fuselage, an innovative air treatment unit was designed.
The innovative approach of the designed air treatment unit is to reduce and even blind out the thermal inertia of the components on the system and to raise the reaction times of the unit by connecting the single components in a parallel way and to keep them permanently in a “stand-by” state. The objective was to use standard components from the air conditioning industry, modify them of necessary and interconnect them to a compact unit.
From the management station, the desired set-points for the air conditions are entered. The central control system then will control the different components of the ATU to achieve these desired values.
When the system is started, the “stand-by” mode will be activated, that means that:
- the ATU central cooling unit is in operation and cooling the buffer to its setpoint
- the electric heating circuit is working on the set internal constant temperature
- the adsorption dryer is in operation and the precooler is supplying the dryer with cold air
- the air cooler is in operation and being supplied with cold glycol from the central cooling unit for the ATUs
After all components have reached their operational state, it will be possible to start the main system for the fuselage supply, that means, that the supply fan will ramp-up and the flap valves will start to control the desired volume flows.
Lead through:
A gas tight lead through for the ACC was constructed. It allows low pressure and low temperature operation of the ACC with the electrical motor beeing outside the ACC in normal conditions. This enables the ACC to operate from -60°C to +120 °C at nearly 0 bar absolute pressure and 10.500 cbm/ h recirc air.
ACC:
For the ACC the construction of a 1-zone model was decided. It was preferred because of the more flexible interior space, better thermal manageability and the possibility to test bigger specimen.
The vessel geometry was selected by the technical advantages of a cylindrical system, especially when considering the planned low pressure operations.
Therefore a cylindrical steel vessel was designed with the following properties:
length: 6500mm
diameter: 3200mm
insulation thickness: 150mm
weight 16 tons
For the thermal insulation of the ACC, a material had to be found, that is resistant to the low temperatures as well as to the high temperatures.
Another very critical influence is coming from the vacuum operation conditions, especially from the rapid decompression scenarios.
A PIR material was selected, based on Polyurethane materials, that can be shape by milling and CNC cutting into the shape of the round vessel. Conglutination with special 2K- material.
For the coating of the abrasive PIR material, a Polyuera material was chosen, that can be spray applied to the surface of the PIR material. When finaling testing the Polyurea material under hot conditions and following rapid evacuation in our small vacuum chamber, the Polyuera material separated from the PIR material.
A new solution had to be worked out.
Due to the low thermal mass and the near term availability of the material, an aluminium coating for the complete inner space of the ACC was selected and applied to the PIR material. Linear expansions due to the big temperature differences had to be considered and were constructively considered by using a special plastic material under each bolt as a slide bearing.
For the desired low temperatures and the planned thermal shock conditions an air cooler was designed and constructed for the use with thermal oil provided by the CCU.
The boundary conditions were 30kW @-65°C oil temperature and 10000 cbm/h of circulated air.
Due to the mass of 700 kg, a steel support was constructed to bear the load of the cooler and distribute it along the grating subconstruction.
Temes:
Temes main responsibility within the BESTT consortium was the development an construction or the Central Cooling Unit (CCU), the R245FA Cooling unit for the heater supply, the High Current Power Supply and related printed circuit boards. Furthermore Temes was responsible to design the ACC components: High current / High Energy Density Heating Elements along with a new connector system.
CCU:
The CCU = Central Cooling Unit comprises two cooling units (CU), working in parallel. Each cooling unit is equipped with
− four cooling machine modules
− one cooling oil storage vessel, filled with 1.700 l oil. The vessel is fed by the four cooling machine modules. Purpose of the oil: Providing high peak cooling capacity when changing the chamber temperature status from hot to cold.
A further vessel is used as expansion tank.
Each cooling machine module KMM507 provides a refrigerating capacity of 5 kW at -65 °C. As refrigerant R507 is used allowing this low temperature.
Four modules KMM507 are mounted on a common frame and working in parallel, providing max. refrigerating capacity of 20 kW at -65 °C. The modules cool the cooling oil which is stored in the cooling oil pressure vessel. This arrangement forms the cooling unit (CU).
Two cooling units CU form the central cooling unit (CCU). The CCU provides max. refrigerating capacity of 40 kW at -65 °C. For safety reasons (environmental pollution) the CCU is located within a safety pan. The pan is dimensioned for the complete amount of cooling oil.
The cooling oil vessel has a capacity of appr. 1.700 l. The cooling oil works as cold storage.
The expansion vessel compensates works as compensation volume which is required due to the different volumes of the cooling oil, depending on its temperature.
In compliance to the ongoing change management needs through the integration phase until April 2014, because not all connecting systems (e.g. ACC designs and T23 compartment) could be finalized and accepted with the FHG IBP and the BESTT consortium in a short time range (until April 2014), Temes had to change in different steps the scheduling, workload and work flow for the CCU system as well as the documentation (see picture below, as one point in the change management, e.g. CDR documentation).
The Central Cooling Unit (CCU) was successfully integrated in the FHG Test field and completely checked by 2 different external test authorities:
- TÜV Nord Essen checked all electrical realization works and the electrical definition files and drawings
- TÜV Süd “safety department” Munich defines in a HAZOP-Meeting and Report to all safety issues
- TÜV Süd “department for cooling system and conformity” Munich checked all realization works and safety reports in a step-by-step-reporting including the reporting to the results through the HAZOP- Meeting.
The Central Cooling Unit was successfully integrated in the FHG IBP area and there Benches and completely accepted from the German Test Authorities as well by step-by-step reportings.
The CCU uses Therminol D12 a cold storage medium. Appr. 4.600 l cooling oil are used.
The Central Cooling Unit uses R507 as refrigerant.
This refrigerant is suitable for temperatures down to -75 °C.
ACC heater:
The ACC heater is used to rapidly heat up the air in the ACC test chamber. A voltage converter provides up to 120 kW electrical power for the heater. The power electronics components of the voltage converter are mounted on water cooled heat sinks. The cooling water absorbs the waste heat dissipated by the power electronics.
The 2.5-m3 storage tank works as a heat buffer.
To cool the water in the storage tank a 25-kW cooling unit (refrigerant: R245fa) is provided.
The R245fa unit transfers the heat to the test facility's recooling circuit, dissipating the heat to the environmental air using a cooling tower.
The R245fa cooling unit including the tank was delivered to the FHG IBP and is ready for integration to the FHG IBP environment since Sept. 2013, but is isn’t foreseen to integrate this in this program yet, because of the budget needs at BESTT-program.
R245fa unit:
This cooling unit is used to cool the water of the 2.500-l storage tank. The water absorbs the heat dissipated by the heat sinks of the high current power supply for the ACC heater.
The future advantages of the R245fa cooling units for cooling properties e.g. FUEL CELL systems including high power electronics for aeronautics and special application we shown within this project.
Power supply:
The heater supply rack is capable to supply 2.700 A max. at 50 V max.
The step down chopper is located in the heater supply rack.
Four double IGBT modules V1 to V4 are working in interleaved mode to switch the input voltage to the output. Only the upper IGBT's are switched when working for the heating.
Each part current is measured by its own current sensor (B1 to B4). Additionally, the total current is measured by sensor B5.
The new developed and realized high current power supply was tested and fully operable and fulfilled all defined specification points.
Advantages: 180 to 200kWs energy storage versus 50 to 70 kWs state of the art
The 5 heating units are ready for integration.
Connector system:
One of the biggest problems in state-of-the-art-power electronic system is the connection between power electronic modules and the environment or the connection between systems.
So, a unique connector system was designed and developed to uphold the parameters for aeronautic equipment and power electronic modules according to the electrical net specifications as well as the mechanical and environmental specifications.
Advantages/target:
1. weight reducing up to 50-60% vs. state of the art, readiness and operability for aeronautic applications
2. High-current contacts
3. IP69
4. High-temperature operability vs. high current and/or high voltage possibilities
5. Loss reducing contacts vs. readiness for aeronautic applications
These finalized designs for the connectors were build as first Prototypes. These Prototypes were fulfilling all electric specification points, but not all Environmental and Weight Needs.
So in the construction phase these points were defined and prototyped in a hybrid manufacturing process with milling and injection molding machines for the first Prototypes.
Through the construction phase of the new designed connectors a lot of problems occur through structure complexity in the connectors and their state-of-the-art-production of connectors.
Modelon:
Use cases for the BESTT project
For each use-case different simulation models with varying and appropriate degrees of detail are required. In order to prepare these models the relevant use-cases have been identified with the different project partners.
For the design phase the following use-cases have been ascertained to be the most relevant.
• Verifying calculation for the plant dimensioning (ATU)
• Virtual comissioning (ATU)
• Control parameter optimization (ATU)
• Verifying calculation for the plant dimensioning (CCU)
• Evaluation of conditioning duration for test procedures (CCU)
• Development of control strategies for air handling (CCU)
Models
Overview
All of the models being developed by Modelon during the project were packaged in a new library for the simulation of cooling systems, the so called “BESTT-Library”. The models were developed using Dymola 2014 with Modelica 3.2. Also required are the commercial libraries AirConditioningLibrary 1.8.4 ModelonLibrary 1.8 and ThermoFluidPro 1.8.4 library.
The various subsystems have been designed to be very modular in order to easily pick and mix the components to ideally suit all manner of problems, thereby reducing the overall complexity and improving simulation performance.
Air treatment unit model
The air treatment units (ATU) are used to condition the mass flow, temperature and humidity of the inlet air of the fuselage mockups. Due to the innovative parallel setup of the components and short air paths the design of the control is quite demanding. The ATU model covers all air ducts, the heater, the cooler, the dryer, the fan and all necessary valves, sensors and control units. It can be used stand alone or in combination with other models like the CCU model.
As far as possible the ATU-model uses standard components from the AirConditioningLibrary, but for several components the development of specific submodels was necessary. Amongst others these mainly include the heater, cooler and air dehydrator with their respective controls and test benches. A notable numerical and simulation challenge was the development of an interface in order to manipulate the humidity rating of air.
Central cooling unit model
The central cooling unit CCU is used to provide cooling oil at temperatures down to -66°C for the thermal test bench. The cool oil is stored in two insulated tanks with several outlets to the thermal test bench. For the cooling down of the oil four parallel single cooling units are combined for each tank as can be seen in the model in figure 2.
The modelling is done as far as possible by using standard components from the Modelon library with appropriate parameters. For performance reasons the cooling units were implemented following a map based approach with maps created by the Bitzer software 6.3.
Flight test facility model
Models for the fuselage mockups at a high level of details were already available but could not be used for performance reasons. For the usage in combination with the CCU and the ATU model simple, fast and generic fuselage mockup models were developed and parameterized.
Simulation study: influence of the isolation thickness
All of the above-mentioned use cases can be evaluated with the current modelling state. In this paper a typical examples for the usage of the Bestt-Library is presented.
In this simulation experiment the CCU is running at full load and the cooling units cool down the oil in the tank. After one hour a heat load is applied to the test facility connected to the tank. The red curve shows the temperature in the tank with the assumption of ideal insulated components (tank, pipes). In further experiments the thickness of the insulation material of the pipes connecting tanks and cooling machines is varied. The curves show the influence of the thickness of the isolation material (green: 1cm, blue: 1.5cm pink: 2cm) on the tank temperature.
Potential Impact:
ATU: The ATU principle will enable high accuracy environmental simulation systems to deliver better results in transient system simulations. It will help to reduce simulation times and reduce inflight tests due to realisitic scenarios on ground.
Other industries will also profit from this very accurate air conditioning systems, especially laboratories and test environments.
ACC: The ACC is a test bench to simultaneously test high altitude and extreme temperature situations for large systems. By this, inflight tests can be reduced and development times can be shortened.
Central Cooling Unit at -65°C:
In future test bench areas, in compliance with new aeronautic standards, it will be necessary to cool down environments and test configurations below – 55°C, so there is a very high interest from test facilities for new cooling systems, which are able to convert very low temperatures with compressor- based machine systems, like the CCU.
R245fa cooling unit:
The future advantages of the R245fa cooling units for cooling properties e.g. FUEL CELL systems including high power electronics for aeronautics and special application we shown within this project.
High current high power system as heating system:
The future advantages of the high current power systems are very sufficient for heating applications in future test bench areas as well as converter systems in FUEL CELL programs for aeronautics and special application we shown within this project.
New connector units for high power systems:
First prototypes very build, but for the ACC integration these connectors are not feasible.
It is necessary in a further development program to invest in high-grade flexible tools to produce connector sets, which are convenient and next to a series connector sets in a state-of-the-art- production line, without any special tooling or separate hybrid production process.
Modelling:
With the developed models, design cycles of environmental simulation systems can be shortened. Especially for the ATU systems, the models can be used to predict the right control strategies.
Within plant engineering system simulation can be used as a powerful tool for dimensioning of plants, the development of control strategies and the testing of control algorithms. Comprehensive commercial simulation tools and model libraries are available on the market. Unfortunately these tools are comparatively expensive in purchase and require specific numerical know-how. That is one reason why system simulation isn’t widely adopted especially in smaller organisations. During the project a workflow for the compilation of licence-free models and the stand-alone execution of this models was developed. The solution is based on the open FMI-standard for the exchange of simulation models.
This workflow makes it possible to outsource the development and validation of simulation models to specialised organizations with the appropriate tools and resources. A technical expert of the plant design company using a case-specific user interface then performs the actual simulation study. This way especially small companies can avoid to hold available costly and highly specific resources but use the advantages of system simulation
The project will enhance the possibilities for European manufacturers and suppliers to develop, test and validate new concepts and equipment located in the aircraft environment. This can be equipment for both existing and future aircraft. Besides, the procedures and installations proposed can be transferred to other high-technology areas, such as the rail sector or power plants.
When aiming at all-electric aircraft architectures thermal issues will become critical inside the pressured fuselage and thus will be a main differentiator in aviation industry. Means to handle and test these critical energy fluxes correctly will therefore contribute to strengthen the competitiveness of the European aviation industry and its suppliers.
Thus BESTT improves not only the product range and applicability of the participating manufacturers but even the reputation of the partners as partners for the aviation industry.
Generally RTD activities are considered by the partners as the basis of sustainable growth in the highly innovative aviation sector, especially for those partners that have their core business in research and innovation development.
BESTT brings together manufacturers and suppliers of aircraft equipment as well as experts in simulation, testing and test bench installation. The consortium elaborated a synergistic way forward to develop new technologies for ground thermal tests as well as their simulation environment. Experimental testing validated both the technology itself as well as the simulation environment falling back on the data gained through the operational testing. Thus the industry can fall back onto a very solid basis for their further development of BESTT technologies for aircraft application. To meet the end-users requirements the close cooperation with the EDS WP4 members delivered the needed input to achieve this impact.This project provided knowledge, operational recommendations, prepared validated technological concepts for implementation of future aircraft testing guidelines, recommendations and European pre-standards, and design guidance for manufacturers, all leading to more competitive aircraft. Public demand for safer and more comfortable aircraft cabins will be met, which would otherwise be heightened by the continued growth in demand for air travel. Through BESTT, European manufacturers will be in a position to anticipate regulations and technical improvements and thereby offer more competitive aircraft in the future, to the benefit of consumers and manufacturers alike.
List of Websites:
www.bestt.eu
Alexander Streit – Coordinator
Streit-TGA GmbH & Co. KG
Bergfeldstraße 1
83607 Holzkirchen
Germany
as@streit-tga.de
Tel. +49 8024 470 274-0
Fax.+49 8024 470 274-9
www.streit-tga.com
Emmeram Klotz
Modelon GmbH München
Agnes Pockels-Bogen 1
80992 München
Germany
emmeram.klotz@modelon.com
Telefon +49 89 416142040
www.modelon.com
Maik Hohmann
Division Manager
Temes Engineering GmbH
Birkerfeld 53
83627 Warngau
Germany
maik.hohmann@temesonline.de
Tel.: +49 (0)8024 473 88 16
Fax: +49 (0)8024 473 88 26
