HIGH FIDELITY 3D TURBOFAN ENGINE SIMULATION WITH EMPHASIS ON TURBOMACHINERY-COMBUSTOR COUPLING

Introduction The 3-dimensional flow in the primary flow path of the GE90-94B high bypass ratio turbofan engine has been achieved. The simulation of the compressor components, the cooled high pressure turbine and the low pressure turbine was performed using the APNASA turbomachinery flow code. The combustor flow and chemistry were simulated using the National Combustor Code, NCC. The engine simulation matches the engine thermodynamic cycle for a sea-level takeoff condition. The fan, booster and OGV are corrected to the cycle condition from component simulations, whereas the high pressure compressor and turbines have been simulated at the cycle condition and coupled to the NCC code by passing profiles. Details of this coupling are presented. Significant gains in parallel computing are demonstrated which allow simulations to take place that can impact design. One of the goals of the Numerical Propulsion System Simulation (NPSS) Program at NASA Glenn Research Center has been to demonstrate a high-fidelity 3D Turbofan Engine Simulation. This simulation will support the multi-dimensional, multi-fidelity, multidiscipline concept of the design and analysis of propulsion systems for the future. This paper describes the current status of one major part of that goal: the complete turbofan engine simulation using an advanced 3-D Navier-Stokes turbomachinery solver, APNASA, coupled with the National Combustion Code, NCC. A production engine has been chosen for this demonstration: the GE90 turbofan engine shown in Fig. 1. A sea level, Mach 0.25, takeoff condition has been chosen for the simulation. The main reason is that detailed cooling flows for the turbine are well known at takeoff since this represents the cooled turbine design condition. Since the cooling flow represents a significant amount of the boundary condition information required for the simulation, it was felt this was a good point for the simulation. It also represents a condition where there are the highest temperatures and most stress in the engine, and is therefore a practical point to gain further understanding. _ C A S b A The GE90 development program included component testing of all the turbomachinery as well as the combustor. The full engine simulation effort has taken advantage of this. All the turbomachinery components 38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 7-10 July 2002, Indianapolis, Indiana AIAA 2002-3769 Copyright © 2002 ___________________________________________ * Professor, Senior Member AIAA. † Member AIAA. ‡ Aerospace Engineer, Senior Member AIAA. § Senior Research Scientist, Associate Fellow AIAA. opyright  2002 by Mark G. Turner, Rob Ryder, ndrew Norris, Mark Celestina, Jeff Moder, Nanuey Liu, John Adamczyk and Joe Veres. Published y the American Institute of Aeronautics and stronautics, Inc. with permission. 1 American Institute of Aeronautics and Astronautics by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. The GE90 Turbofan Engine have been analyzed and compared to component test data to validate and calibrate the approach. These efforts have been presented by Turner, Turner et al., and Adamczyk. Also presented by Turner et al. was the coupled high and low pressure turbine run at engine conditions. Temperature profile test data does not exist for the combustor running at takeoff conditions so that validation could not be made. The GE90-94B is a production engine offered on the Boeing 777-200ER as shown in a cutaway schematic in Fig. 1. It is a 94,000 pound thrust version of the GE90 with a bypass ratio of 8.4. The fan is 120 inches in diameter comprising 22 composite wide-chord blades. The fan outlet guide vane (OGV) has several types with different camber to guide the bypass flow around the pylon. Only the nominal type is modeled in the simulation. The efforts presented in this paper have built on the successful component simulations by running or correcting each component to the engine condition. A cycle analysis of the GE90 at the takeoff condition has been run. This cycle point is used to help ground the simulation and to compare with the full 3D simulation. The profiles have been passed from the high pressure compressor (HPC) to the combustor and from the combustor to the high pressure turbine (HPT). The booster, or low pressure compressor, consists of three stages and rotates on a common shaft with the fan and low pressure turbine (LPT). The three stages comprise 7 blade rows. A fan frame strut separates the booster from the high pressure compressor (HPC). The 10 stage HPC has a 23-to-1 pressure ratio and has been redesigned using three-dimensional aerodynamic (3-D Aero) technology. The original GE90 HPC was a scale of the HPC developed for the NASA/GE Energy Efficient Engine (E) program. The HPC is on a common shaft with the high pressure turbine (HPT). The full engine simulation project has produced improved component simulations in computer run times that are now short enough to impact design. The coupled high and low pressure turbine presented in Turner et al. was the first dual spool turbine simulation published. As engines are pushed to higher pressure ratios with reduced part counts, component coupling is becoming even more important. The work presented in this paper demonstrates the coupling of the high fidelity turbomachinery and combustor simulations. The combustor is a dual dome annular design for reduced NOX emission levels and reduced unburned hydrocarbon, carbon monoxide and smoke levels. There are 30 pairs of fuel nozzles around the annulus. The HPT has two stages comprising 4 blade rows. There is a turbine mid frame strut separating the HPT and LPT. It diffuses the flow through a high angle outer diameter casing to a high diameter for an improved efficiency LPT. The LPT has 6 stages comprising 12 blade rows. A turbine rear frame strut follows this. One other important aspect of this effort is to reduce the wall clock time to obtain a simulation by exploiting parallel processing as much as possible. Reduced solution times are necessary to efficiently explore the physics of a problem, to validate a code, and most importantly, to impact design. The simulation consists of 49 blade rows of turbomachinery and a 24-degree sector of the combustor. The 49 blade rows include the fan, bypass splitter, nominal OGV (the pylon and different OGV types are not modeled), the 3 stage booster (7 blade rows), the fan frame strut, the 10 stage HPC (21 blade rows), the 2 stage HPT (4 blade rows), the turbine midframe strut, the 6 stage LPT (12 blade rows), and the turbine rear frame strut. Although there are 30 pairs of fuel nozzles, actual periodicity of the geometry requires the modeling of 2 pairs of fuel nozzles, or a 24-degree sector. Unique cooling arrangements make one pair of fuel nozzles a-periodic. The approach used is presented in the next section of this paper that describes the GE90 engine, the turbomachinery solver, the combustor solver and the coupling strategy. The results section then briefly discusses the simulations and the coupling of the combustor with the turbine in further detail. The solution timings of the parallel solvers are discussed next. At the end of the paper is a discussion on the major conclusions and future work.