Abstract
A brief survey is given of the scope of the design of displacement pumps and hydromotors which are used in the realisation of hydrostatic power transmissions.
During the recent 25 years the computer is playing a role of ever increasing importance in the design and the development of these hydraulic energy converters.
This role has been started on the testbench for pumps and hydromotors. The data aquisition and data processing by computer has led to a much better guidance of the design process. The testing developed from a simple and sometimes very inaccurate determination of efficiencies, based on sometimes very doubtful definitions, into an accurate tool for the designer, with a quite good resolution for detailed analysis of the losses within the prototype. The introduction of the computer to testing had a very upgrading effect on the quality of the testresults.
The disadvantages were the higher costs of testing equipment, the need for higher qualified operators and the generation of a flux of information, demanding qualified engineers that understand the meaning of this information.
The use of the computer also penetrated into the design of pumps and hydromotors. Not only into the design of details of these energy converters but also into optimising the design. The design of controls for pumps and hydromotors, with variable displacement, also has become ‘computer aided’. In this publication some examples are given of the use of computers to enhance the design of details of hydraulic energy converters.
Also the computer can be applied to ‘integrate’ the different procedures which we usually have to execute during a design process, into one coherent package of software.
The computer can perform the design cycle much faster and much more often than a human designer. Once such a package has been realised, it can be used to produce an optimised design. A hydromotor designed by such an integrated design software package is shown. Here again one can mention disadvantages of the introduction of computers into the design process. The designer should have adequate knowledge of the use of computers, in order to be able to use the sometimes expensive computer hardware as a tool for design. The creation of an integrated software package has a long leadtime. Many times one finds ‘blank spots’ or even ‘blank fields’ in the available knowledge about the object to be designed. Without filling these ‘blanks’ with information, the integration of the design package can not be completed. Sometimes tests have to be run, in order to fill in these blanks with information of acceptable quality.
The advantages of the introduction of computer aided design for pumps and hydromotors have become clearly noticable. The improvement of the quality of design is undeniable. The attention of the designer is focussed on the optimization of the design, both in detail and integrally. His understanding of what is going on inside the pump or hydromotor is improved considerably.
