KRATZER AUTOMATION AG: Variable Venturi VTflX - current developments

The VTflX is a high-precision measuring device for measuring the compressor intake air-flow of the turbocharger on hot gas test benches. KRATZER AUTOMATION has now revised and improved the component and opened it for further applications, for example on fuel cell test benches.

Variable Venturi VTflX - for flow measurement of compressor intake air

The measuring device is based on a Venturi geometry with adjustable active cross-section and is a joint development of KRATZER AUTOMATION AG and sa-charging solutions. To better meet the requirements of the everyday test bench operations, we made use of the advantages of the differential pressure-based measuring systems such as orifice plates, nozzles, and Venturis and at the same time significantly increase the measuring range by means of variability.

Robustness, reproducibility and error propagation on the turbocharger test bench with VTflX

On turbocharger test benches for passenger car, light, and heavy-duty applications, the robust measurement of compressor mass flows is a crucial element for determining the turbine efficiency using the turbocharger main equation. The required robustness is as positively influenced by the use of the variable Venturi VTflX as the reproducibility and error propagation in the overall system.

VTflX versus classic orifice plate

The measuring system we developed is  equal in robustness, accuracy, and repeatability than standard flow orifices, and additionally achieves a significantly higher turndown ratio of up to 1:50. This measurement range covers the requirements of radial compressors during turbocharger mapping very well. Internal comparisons with thermal or ultrasonic-based measurement systems show that our VTflX measurement device has clear advantages in terms of dynamic, raw signal stability, and accuracy.

Higher availability - lower calibration costs

The improved long-term stability compared to other volume flow measurement systems enables increased test bench availability in daily operation, while at the same time reducing maintenance and calibration costs. Using the variable Venturi VTflX, the calibration needs are limited to the pressure and temperature probes and can be carried out on-site. Thus, the measurement device does not need to be returned to the manufacturer for calibration tasks.

Open to the future - VTflX provides potential beyond hot gas test benches

In the first step, the focus of design and functional implementation was on the application of turbocharger test benches and there especially on the compressor intake side. However, we clearly see the potential for applications beyond hot gas test benches. There are advantages for all testing tasks and implementation where high demands on accuracy and repeatability occur. For example, this applies to component test benches (fuel cells, flow benches for cylinder heads, etc.) and additionally as a reference for engine air intake charge determination models.

Test it - with our demo device

The first series is already in daily use and some of the devices have now completed operating times of more than 3000 hours without significant wear or loss of accuracy. All systems in use have been calibrated at the Swiss Federal Institute of Metrology (METAS).
We have one of the devices ready for you as a demo device. We would be pleased to make this VTflX available to you for a test run.


Please get in contact with us.