Towards virtual testing of compression systems in gas turbine engines

Current trends in the computational fluid dynamics (CFD) analysis of gas turbine engines are in the direction of the so called "virtual testing". Although this term is used nowadays loosely in the context of this application, the ultimate objective of virtual tests is to replace partly or fully rig and engine tests during the design and certification of engines. In the past few decades, significant developments have been achieved in the discretisation methods and the associated CFD algorithms. Combined with the rapid developments in hardware in both speed and memory which are becoming increasingly available at affordable prices, the simulation of full engine or rig tests are increasingly becoming a reality. This paper describes a method by which virtual tests can be conducted on a low pressure compression system of a gas turbine engine using smart boundary conditions and allowing the sweep along a speed characteristic or sweep along a working line during the mapping of the compressor characteristic in a similar fashion to a typical rig test. The low pressure compression system is equipped with a variable downstream nozzle and the rotational speed is allowed to vary during the computations. The simulations are validated using NASA rotor 67 experimental data where good agreement was obtained