Ceramic Flat Slide Valve

  Concept of a Flat Spool Valve

Flat slide valves have the potential to reduce leakage and increase service life compared to conventional valves used in industry. A demonstrator was built and tested to prove the functionality of a flat slide valve. For this purpose, the pressure compensation was first tested with a main stage made of steel. Afterwards the metallic main stage was removed and replaced by ceramic main stages made of Al2O3 and Si3N4. After testing the pressure compensation, the occurring leakage and the necessary adjustment forces for different degrees of compensation were determined. 

 
Benefit Procedure
Innovative valve concept Definition of the operating conditions and preparation of a requirement profile
Reduction of leakage Design of the hydraulic stage
Reduction of control edge wear Development and optimization of pressure compensation
Increase service life & efficiency Construction and testing of the flat slide valve

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Advantages of the Ceramic Flat Spool Valve

Rounding at the Control Edge (left) and Leakage Between Spool Valve and Housing (right) Rounding at the Control Edge (left) and Leakage Between Spool Valve and Housing (right)

There are two disadvantages when using piston spool valves, which are primarily used in hydraulics for resistance control.

Between the slide and the housing there is a leakage in piston slide valves due to the gap caused by the principle, as can be seen in the figure on the right. This leakage leads to a reduction in efficiency. The concept of the flat spool valve can significantly reduce the gap height and the resulting leakage. In doing so, a gap formation between the control plates and the gate is counteracted by applying a compensating force.

  Flat spool valve concept with pressure compensation Copyright: ifas Flat spool valve concept with pressure compensation

Due to the design of the flat slide valve it is possible to manufacture the control plates and slide valve plates from a ceramic material. Thereby design and material harmonise. The geometries are simple enough to be implemented from ceramic semi-finished products at low cost and with sufficient accuracy. Due to the high plane-parallelism and the achievable surface qualities, small gap dimensions can be achieved.

In piston valves, the slides are usually made of a metallic material. As shown on the left in the illustration, this results in abrasive wear at the control edges. This has a negative influence on the control behaviour of the valves and leads to a limitation of the service life. Due to the fact that the hydraulic stage of the flat gate valve will be made of a ceramic material, which has a much higher hardness and resistance against abrasive wear compared to metals, an increase in service life can be achieved.

 

Cooperation Project

Project Procedure in Cooperation with the IWM of RWTH Aachen University Project Procedure in Cooperation with the IWM of RWTH Aachen University

The project is being carried out with experts in the field of materials technology, the Institute for Material Applications in Mechanical Engineering (IWM) at RWTH Aachen University.

As shown in the figure, the IWM is concerned with the determination of suitable ceramics through material investigations. At ifas, a prototype of the flat slide valve, in which the hydraulic stage (control plates & slide plate) will initially be made of steel, is being constructed. The demonstrator will be used to validate and optimise the previously developed pressure compensation. The knowledge gained from the development and testing of the first prototype will be used together with the findings of the material investigation carried out by the IWM to construct a prototype in which the hydraulic stage will consist of ceramic components. These prototypes will be used to prove the functionality of the ceramic flat slide valve.

 

Development of Pressure Compensation

Implemented Calculation of the Forces for Geometry Optimization Implemented Calculation of the Forces for Geometry Optimization

When designing the pressure compensation, there are two opposing design criteria. On the one hand, the force applied to the control plates must be large enough to counteract an increase in the gap between the control plates and the valve plate. On the other hand a too high compensation force causes high frictional forces, which must be overcome by an actuator. Therefore, one focus of the research project is the design of the pressure compensation.

For this purpose, a calculation program was developed in Matlab, which calculates the forces acting on the slider and thus enables rapid geometry optimisation.

 

Design of the Hydraulic Stage

Design of the Hydraulic Stage using CFD Simulations Copyright: ifas Design of the Hydraulic Stage using CFD Simulations

The hydraulic stage was designed with the help of test bench trials with a 2-2-way valve, which was developed in a preliminary study at ifas. With the help of the results from the test bench trials, the flow channel geometry was predicted and subsequently optimised by CFD simulations.

A flow rate of 30 l/min with complete valve spool deflection and a pressure difference of 10 bar is planned.

 
 

Testing of the demonstrator

Volume flow characteristics of the flat slide valve Copyright: ifas Volume flow characteristics of the flat slide valve

The volume flow characteristics measured during the testing of the flat slide valve show a good agreement with the simulations carried out. In addition, an almost linear behaviour between slide valve deflection and resulting volume flow could be realised. The measurements, like the simulations, were carried out with a mineral oil of type HLP 46 at 40°C and a constant pressure difference of 10 bar per control edge.

 

Acknowledgement

The IGF project 19576 N / 1 and 19576 N / 2 of the Forschungsvereinigung Forschungskuratorium Maschinenbau e.V. - FKM, Lyoner Straße 18, 60528 Frankfurt am Main was funded via the AiF as part of the programme to promote joint industrial research and development (IGF) by the Federal Ministry of Economics and Energy on the basis of a resolution of the German Bundestag.

  Copyright: AIF
 
 

Publications

Aengenheister, Stefan; Liu, Chao, Broeckmann, Christoph; Schmitz, Katharina: “ Functional proof of a flat slide valve as a 4/3-way proportional valve“, 2020, 12th International Fluid Power Conference, IFK 2020
Aengenheister, Stefan; Liu, Chao; Figge, Felix; Broeckmann, Christoph; Schmitz, Katharina: „A 4/3-Way Flat Slide Valve with a Metallic Main Stage“, 2020, ASME/BATH 2020 Symposium on Fluid Power and Motion Control
Aengenheister, Stefan; Liu, Chao, Broeckmann, Christoph, Schmitz Katharina: “ A Ceramic Flat Slide Valve for Hydraulic Applications“, 2019, ASME/BATH 2019 Symposium on Fluid Power and Motion Control
Liu, Chao; Aengenheister, Stefan; Herzog, Simone; Deng, Yuanbin; Kaletsch, Anke; Bezold, Alexander; Schmitz, Katharina; Broeckmann, Christoph: „ Tribological Qualification and Prediction of Fracture Probability of High-Performance Ceramics for Application in Flat Sliding Valves“, 2019, Ceramic Application, Band 7, Baden-Baden