Gas turbines engine designers are leaning towards aircraft engine architectures due to their footprint, weight, and performance advantages. Such engines need some modifications to both the combustion system, to comply with emission limits, and turbine rotational speed. Aero derivative engines maintain the same legacy aircraft engine architecture, and replace the fan and booster with higher speed compressor booster driven by a single stage intermediate turbine. A multistage free power turbine (FPT) sits on a separate shaft to drive compressors for Liquefied Natural Gas (LNG) applications or generators. The intermediate power turbine (IPT) design is important for the engine performance as it drives the booster compressor and sets the inlet boundary conditions to the downstream power turbine. This paper describes the experience of Baker Hughes, a GE company (BHGE) in the design of the intermediate turbine that sits in between a GE legacy aircraft engine core exhaust and the downstream power turbine. This paper focuses on the flow path of the TCF/intermediate turbine and the associated design, as well as on the 3D steady and unsteady CFD assisted design of the IPT stage to control secondary flows in presence of through flow curvature induced by the upstream TCF.
Gas turbines engine designers are leaning toward aircraft engine architectures due to their footprint, weight, and performance advantages. Such engines need some modifications to both the combustion system, to comply with emission limits, and turbine rotational speed. Aeroderivative engines maintain the same legacy aircraft engine architecture and replace the fan and booster with a higher speed compressor booster driven by a single-stage intermediate turbine. A multistage free power turbine (FPT) sits on a separate shaft to drive compressors for liquefied natural gas (LNG) applications or generators. The intermediate-power turbine (IPT) design is important for the engine performance as it drives the booster compressor and sets the inlet boundary conditions to the downstream power turbine. This paper describes the experience of Baker Hughes, a GE company (BHGE) in the design of the intermediate turbine that sits in between a GE legacy aircraft engine core exhaust and the downstream power turbine. This paper focuses on the flow path of the turbine center frame (TCF)/intermediate turbine and the associated design, as well as on the 3D steady and unsteady computational fluid dynamics (CFD)-assisted design of the IPT stage to control secondary flows in presence of through flow curvature induced by the upstream TCF.
This paper describes a coupled experimental and CFD campaign conducted on a 1.5 intermediate turbine stage in the full range of operating conditions, from start-up to design point under variable expansion ratio and physical speed. The test maintains engine similitude conditions and allows direct comparison with CFD data to assess the predictions accuracy. The choice of variables to describe the speedlines is also addressed by using both measured and predicted data. A discussion on velocity ratio versus corrected speed illustrates the advantages of the former parameter the adoption of which produces constant shape curves in a very wide range of operating conditions. The comparison between measurements and predictions suggests that CFD, in conjunction with performance correlations, is a viable tool to predict speedlines in a fairly wide range of conditions, provided that geometrical and operational details are carefully matched.
The life of valves is extremely important for the availability of hypercompressors in LDPE plants. Different factors such as high gas temperatures, early wear, the presence of polymers or loud noise, can give an indication of poor valve performance that could shorten their life. 3D computational fluid dynamics (CFD) has been extensively used to obtain an accurate evaluation of pressure losses, drag forces and flow coefficients at various operating conditions. CFD dimensionless flow field coefficients have been fed into 1D valve dynamics model simulations, resulting in a more accurate calculation, able to better predict the poppet position during valve opening and closing. The poppet motion can be correlated to critical performance factors and can be used to estimate valve life. Experimental validation will allow a fine tuning of this modified model for valve performance prediction, which can be used to design optimized valve geometries with improved reliability.
Valves are extremely important for the availability of hypercompressors in LDPE plants. A methodology for the life assessment of these valves was developed based on numerical calculations and experimental results. A test rig was used to measure the behavior of different poppet valves in terms of differential pressure and valve lift as a function of the process flow. Water is used as the working fluid instead of ethylene, since the flow is almost incompressible. The Measured data were reduced to non-dimensional flow and drag coefficients as a non-linear function of the poppet position. The valve characteristics and real gas data were used in a one-dimensional dynamic simulator to evaluate the poppet position during a single crank cycle together with pressure losses. The calculated dynamic behavior of the poppet was correlated to the failure modes experienced in the field. A dynamic finite element analysis was used to calculate the mechanical stresses on both the poppet and valve body from impact velocities. The stresses from each impact (both during the opening and closing phases) and the axial poppet displacement were accounted for to estimate the total cumulative damage and assess the life of each valve design.
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