Faster Analysis, Quieter Engines 
Achieving noise reductions in modern aero-engines represents a complicated engineering challenge, as these engines consist of multiple subassemblies that are connected to multiple shafts, rotating at different speeds. Most of the air drawn in by the large fan travels down the bypass duct of the engine. A fraction of the air is fed into the core part of the engine, which includes the compressor, combustion and turbine stages, each making a distinct contribution to the engine’s overall noise levels. Another prominent noise source is the engine exhaust jet, which creates noise downstream the engine, due to turbulence when the jet comes into contact with surrounding ambient air.
Testing on scaled components and full engines
Rolls-Royce runs in-depth feasibility assessments using proprietary noise prediction models of engines and engine components. Throughout the development of a new engine, Rolls-Royce engineers extensively use these models to optimize the noise performance of the engine. To gradually reduce the risks through an engine development project, Rolls-Royce executes extensive testing activities and systematically uses the test results to calibrate its prediction models. By performing rig tests on scaled physical engine component models, Rolls-Royce engineers are able to efficiently determine and study the noise contribution of the different engine components. One example is the jet engine exhaust, where dedicated anechoic test facilities are used to validate different shapes of jet nozzles and other components to achieve the optimum design.
To obtain maximum flexibility for its acoustic engine testing activities, Rolls-Royce collects the data at different test sites by means of digital tape recording systems, and brings the tapes to a centralized data analysis facility in Derby, UK. The data analysis configuration at Rolls-Royce consists of a LAN network with five LMS CADA-X TMON seats, extended with LMS Test.Lab Desktop and LMS Tec.Manager, which are currently being integrated. The data analysis process starts when data streamers read the acquired time data from the recorded tapes. Rolls-Royce uses its network of LMS data analysis stations to accurately and efficiently crunch high volumes of data by performing a range of different analyses. Most of these analyses reduce the amounts of data by converting the time data into the frequency domain and applying specific data reduction techniques, making it a lot easier to interpret the data. Another critical factor is the data processing speed, which clearly outperforms the speed of the previously installed system.
An efficient environment for noise engineering
The LMS data analysis systems are a well-maintained standard third-party solution that is easy to integrate into Rolls-Royce development processes. The LMS data analysis solution is able to significantly increase the data analysis speed, through the distribution of the analysis workload over different processing stations. The LMS CADA-X TMON stations also allow Rolls-Royce1 to run analyses fully automatically, or follow any preferred interactive sequence to suit specific analysis needs. In addition, the programmable interface makes it possible to take in data from different acquisition systems, and define customizable data reduction techniques.
