The laboratory is part of the practical education on machines and engines.The students of the 8. semsester carry out measurements to determine power output (duty) respectivly power consumption, efficency, characteristic coefficients and lims. Furthermore the experimental set-up is used to clarify theoretical topics of the lectures , such as cavitation, opertational behaviour, speed and throtting control of compressorsand pumps.
Topics internal theses (handling within the laboratory) concerning primarily the renewing of the existing equipment and construction of new test and measurements techniques.
Topics external theses (handling within the company) will be selected in agreement with the industrial partners. In this case the equipment of the laboratory can be used if necessary.
With the available equipment experimental and theoretical RDT-studies can be carried out. The experimental set-up enables investigations on model-hydroturbins, centrifugal pumps, fans and flow guided components, such as perforated plates and others. Three dimensional flow fields can be analysed by means of the CFD-Software ANSYS-cfx and ANSYS-ICEM (Computational Fluid Dynamics).
Test Stand Concept:
The test stand can be operated in both open and closed loop configurations. The test stand is configured for a given test operation by opening or closing the appropriate shut-off gate valves (Fig. 1). The key test stand components include the circulating pump (P1) and the “under water” pressure vessel. With the help of these items, the inlet and outlet pressure of the component investigated can be varied.
Modes of Operation (open and closed loop):
In the open-loop mode of operation, the circulating pump pumps water out of the open reservoir to feed the components to be tested. After flowing through the turbine, the water flows through the tailwater tank and an open channel, such as that of the reservoir. Since the outlet flow into an open channel depends on the local conditions, the pressure in the tailwater (turbine outlet) is set and cannot be varied. It is advantageous that the stability of the selected operating point can be guaranteed with higher certainty. This method of operation is suitable for testing turbines and hydraulic components such as pumps and valves when no variation of the backpressure is necessary and the outlet pressure of the object constant values of the order of atmospheric pressure.
For tests of turbines or hydraulic components where various backpressures are desired measurements are carried out in closed loop mode using the tailwater tank. The tailwater tank in this mode of operation has no connection to the open channel, so that the pressure in the tailwater tank can be set according to the requirements. The circulating pump pumps the water directly out of the tailwater tank and through a pressurized pipe to the unit under test, from which it flows into the tailwater tank again.
For testing centrifugal pumps, the test stand is usually operated closed loop. Compared to turbine operation, the flow is in the opposite direction during pump tests so that the tailwater tank is upstream of the pump to be tested. Thus, the pump inlet pressure can be varied using the tailwater tank. The centrifugal pump under test pumps water out of the tailwater tank and through a pipe, in which a throttling valve is installed, which returns to the tailwater tank. The circulating pump can also be included in the loop if needed.
Observation of Cavitation:
Plexiglas inserts, in the pump inlet and turbine outlet, are included for optical studies of cavitation effects, which can be observed from the formation of the vapor bubbles, through their transport, to their collapse. A stroboscope is utilized whose flash frequency is locked to that of the fundamental rotor frequency and whose relative phase angle can be adjusted. This enables photographs of the quasi-stationary flow fields at defined points in time to be taken, i.e. at definite relative positions of the rotor blades to the trigger. Additionally, it is possible to observe the flow configuration in the rotor through creation of a slow motion effect.
Test Stand Component Specifications
Test Stand Specifications:
- flow rate bup to 0,3m³/s (bis 1080m³/h)
- pump head ca. 15 mWS
- turbine head ca. 10 mWS
- circulating pump drive power 55 kW
- tailwater tank max. pressure (pmin to pmax)abs.: 0,15 bis 3,5 bar
- Circulating Pump Specifications: rated flow rate up to 0,3 m³/s (1080 m³/h)
- rated head 15 mWS
- maximum head 25 mWS
- NPSH 5,4 m
- drive motor ratings 55 kW, 960 min-¹
- Tailwater Tank Specifications: rated pressure -0,85 to +2,5 bar
- diameter 1,2 m
- volume 3,5 m³
- rated diameter 300 mm
- rated pressure 6,0 bar
- Throttle Valve Specifications:
- maximum differential pressure 5,0 bar
- Kaplan model turbine specifications: generator ratings 22 kW, 3000 min-¹
- maximum RPM 2000 min-¹
- reference diameter (D) 0,15 m
- flow area high-pressure side (A1) 0,05309 m²
- flow area low-pressure side (A2) 0,08663 m²
- Francis-Pump-turbine specifications:
- Drive Motor Ratings (pump operation) 45 kW, 1500 min-¹
- rated RPM 1500 min-¹
- maximum RPM 3000 min-¹
- reference diameter (D) 0,1792 m
- diameter high pressure side (d1) 0,250 m
- flow area high pressure side (A1) 0,01779 m²
- flow area low pressure side (A1) 0,05711 m²
Test and Measurement Methods
The experiments are run from a central control platform. The parameter of the various measurement points are set with the help of servomotors. This include the regulating gate valve of the plant for throtting control and the guide vane position, the pressure within the tailwater tank as well as the head of the head of the circulating pump. The variation of speed takes place in the turbine operation mode by changing the load of the generator and in the pump operation mode with help of a frequency converter.
There are different loading mechanism installed. The Kaplan-turbine is loaded by a generator with load resistances. The generator of the Francis-turbine is via an automatic synchronizing device connected with the public electric network to feed power. The measurement techniques, evaluation and display of the results are controlled by Pc.
Test Stand History
The fan test chamber was built in cooperation with a mid-sized company (Schmidt-Seeger AG, Beilngries). A large number of students were involved as part of their Diplom/FH (equivalent to Bachelor) theses. Initially the main concerns were developing concepts and considerations about the layout of the test chamber. Then the concerns were working out the detailed design and construction of the test chamber. In the third phase the emphasis was on installing the instrumentation and programming the computer for automated data acquisition and test data evaluation.
Detailed descriptions of the fan project can be found in Spectrum magazine, published by the Regensburg University of Applied Sciences (issues 1/95 and 1/97).
The test chamber is used for measurement of the performance curves of fans. Additionally, pressure drop measurements on flow components can be carried out. All test chamber components are so dimensioned that, in addition to teaching use, tests for industry can also be performed. With this in mind, the test chamber was designed to be as flexible as possible, so that different types of fans with various diameters and connection sizes can be installed and tested.
As part of the fan project, the perfomance curves of a new series of fan models developed by Schmidt-Seeger AG, Beilngries, were determined. After the end of this project, the test chamber was also used for determining the pressure losses of filters.
Test Chamber Concept
The test chamber concept is based on DIN 24163. It includes three parts and is most appropriate for fans that will be selected on the basis of catalog data, which was determined without knowledge of the installation details for the various applications. The design of the Test Chamber fulfills the basic requirements of DIN and ISO.
Instrumentation and Computer Interfacing
The acquisition and evaluation of the measurement data as well as graphing of the characteristic curves is computer controlled using DIA/DAGO software (GfS Aachen), with help of self-developed algorithims (see following diagram).
Features of the Test Stand Components
The following configuration drawing gives an overview of the most important parts of the test stand.
The following machinery test stands belong to the laboratory:
- Hydraulic Turbomachinery
- Testchamber for fans
The machinery test stands are mainly used for education to show the construction of turbomachinary, test methods and measurement techniques.
The Hydraulic Machinery Laboratory is located on the ground floor of the Mechanical Engineering Laboratory Building and extends over two floors. It has 250 m² of floor space. An additional 45 m² are available on a gallery. In addition to water, electric power, and internet, the laboratory has several lab tables with connections for compressed air and electric power (220 und 380 Volt). Currently two machinery test stands have been set up which will be described below.
Hydraulic Machinery Laboratory (View from the Gallery)
Layout of the Test Stand
Range of Application:
The Test Stand for Hydraulic Turbomachinery can be used for carrying out tests on scale models of centrifugal pumps and water turbines. Currently a Francis turbine pump and a doubly adjustable Kaplan turbine are installed. Tests on flow components, such as pressure drop measurements, are possible if suitable modifications are made. All test stand components are so dimensioned that it can be used for applied research and development and industrial contracts in addition to teaching.
Test Stand for Hydraulic Machines