Dynamic temperature control of an endurance test bench

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Lauda has implemented a suite of updates in its Kryoheater Selecta line of temperature control equipment, to provide improved operational efficiency and process safety

In the development of engine components, durability and functionality tests are conducted using different methods of analysis including strength, dynamic and wear tests.

Long-term strength characteristics can be determined by subjecting components to temperature. Figure 1 shows an engine component under analysis inside a temperature chamber. For reasons of confidentiality, only one simplified illustration of the application can be shown.

Figure 1: The test bench with engine components including the newly developed Lauda Kryoheater Selecta KHS 3560W for temperature control (right)

The test objects are attached to a test bench adapter. This corresponds to the geometry and the supply of the components in an internal combustion engine. The components, as in practice, are flooded with a water-glycol mixture.

The test objects must be subjected to specific temperature profiles over time with temperature being closely monitored. Temperature range usually varies between 40-150°C.

Figure 2 shows a temperature profile, often used in the automotive industry. The cycle shown here lasts 400 minutes but, within the scope of the durability tests, usually runs as an infinite loop.

Figure 2: Temperature-time course of the durability test

The load cycles describe the cold start conditions under ‘Siberian conditions’, and reach the operating temperature and finally the cool-down period after the engine is switched off.

These loads are shown in the graph as shallow and steep temperature gradients and areas where the temperature must be kept constant over a longer period of time. To run through this temperature profile precisely and reliably, powerful temperature control devices are required that master these highly dynamic temperature control tasks.

A continuous cycle with the following specifications is required:

– Temperatures from -40-150°C in the medium of water/glycol

– Use of steep temperature gradients (160Kh = ?T/h)

– Limitation of the outlet temperature

– Visualization, archiving in databases, and evaluation reporting

– Flexible connection of the temperature control devices to various test benches

The process thermostats of the Kryoheater Selecta product line are ideally suited to these demanding temperature tasks. To meet the desired specifications, a KHS 3,560W process thermostat with a cooling output of 35kW can be used. This thermostat covers a temperature range from -60-00°C.

Equipped with a powerful magnetic-coupled pump, high flow rates can be achieved at constant pressure. The required pressure is built up quickly and under constant control where the pump output is possible over a preset pressure value.

The pump is infinitely adjustable and ensures optimum heat transfer to the consumer (here approximately 30-liter water/glycolic mixture). The integrated frequency converter allows highly accurate, application-specific speed control (40-100%). Furthermore the magnetic coupling ensures that there is no leakage, even in continuous operation.

A resilient pressure and volume expansion vessel can also be increased with an overlay of nitrogen. This prevents contact of the heat transfer liquids with the ambient air and prevents the entry of moisture. Working with the nitrogen overlay, the temperature ranges of the heat transfer liquids can, on the one hand, be extended because boiling ranges can be lifted. On the other hand, oxidation of the heat transfer liquids by atmospheric oxygen prevents that which prolongs the life of these heat transfer fluids.

Exact temperature control is of particular importance for reproducibility and accuracy of the results. The Kryoheater Selecta systems have an integrated PLC control in an industrial enclosure. The electronic control system automatically runs almost completely on its own without human intervention. Thanks to this high level of automation, endurance tests require minimal effort.

The process thermostats work reliably within an ambient temperature range of 5-40°C – such as during the hot summer months – using cooling water temperatures of up to 30°C.

Its design ensures maximum security with a protection class of IP54, which means it can be used in harsh production environments. Accessibility to all components enables ease of maintenance.

The Kryoheater Selecta thermostats also offer a high level of operating safety. Newly implemented safety measures enable unattended continuous operation. All the relevant operating statuses are constantly monitored and visualized on the touchscreen interface. A large 7in color display provides a clear and comprehensive presentation of all important information in the form of values, graphical representations and remarks.

A touch function further optimizes usability. Multiple user levels can be managed using password protection. While the administrator can configure everyday work in advance, selected employees have restricted access rights and can only retrieve settings. This prevents accidental changes to parameters and incorrect operation. Operation is continuously monitored. Warnings and errors are clearly displayed and the system switches itself off if necessary. In case of errors, these can be traced so a test does not need to be completely restarted. In this event, existing records are used.

The system is equipped with various data communication channels enabling adaptation according to the application requirements. The temperature control system can also be remote-controlled easily via networks or included in control systems.

The Kryoheater Selecta is equipped as standard with a USB port, a LEMO connector for an external temperature sensor, and a freely selectable interface (analog module, RS-232 /-485, Profibus, PROFINET, EtherCAT).

This approach is beneficial for many users because the user interface over a network has the same functionality as operation directly on the device. Remote maintenance via a modem is also possible, which enables quick and safe connection of the process thermostats with the Lauda service analysis and assistance via VPN over LAN or UMTS.

August 30, 2016

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John joined UKi Media & Events in 2012 and has worked across a range of B2B titles within the company's automotive, marine and entertainment divisions. Currently editor of Automotive Testing Technology International, Crash Test Technology International and Electric & Hybrid Marine Technology International, John co-ordinates the day-the-day operations of each magazine, from commissioning and writing to editing and signing-off, as well managing web content. Aside from the magazines, John also serves as co-chairman of the annual Electric & Hybrid Marine Awards and can be found sniffing out stories throughout the halls of several of UKI's industry-leading expo events.

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