Design Validation of High Speed Ratio Epicyclic Gear Technology in Compression Systems

Abstract

Lecture 5: Epicyclic gear technology is a key factor to support thcompression growth strategy in electrified applications, due to the ever increasing transmission ratio required to meet the high compressor speeds. The paper collects the experience of the authors in developing a unique product through its conceptual design, as well as its mechanical and rotordynamic assessment, up to its complete validation with a full speed full load test in a complete unit arrangement. The main target of high pressure ratio compressors is to fulfil the required compression service with one casing less than traditional technology. The new compressor technology results in machines which run much higher in speed. To achieve a compressor ratio of ~30 in a single casing, the rotational speed is increase by roughly 40% respect to a traditional compression train, and therefore it becomes the most critical parameter. The specific requirements of higher speeds at high powers dictate the need for the very high speed ratio gearing, which was critical to the success of the new compressor technology. The power transmission was jointly developed by the gear and compressor manufacturers. The methods used to evaluate the gearbox configuration options are detailed in this paper, along with the gearbox specific technology design challenges faced. A detailed overview of the selected epicyclic transmission technology is provided and how the use of the fundamental configuration was able to provide advantages over more traditional arrangements when combined with some application specific design features. Specific address will be provided to the tooth design principles applied, bearing technology and rotordynamic modelling and performance. The paper will close with details of transmission performance testing from the gearbox manufactures test bed to the full load string test in a complete compressor unit arrangement, at different operating conditions.