Surge Margin Research Articles

Surge Margin Optimization of Centrifugal Compressors Using a New Objective Function Based on Local Flow Parameters

Currently, 3D-CFD design optimization of centrifugal compressors in terms of the surge margin is one major unresolved issue. On that account, this paper introduces a new kind of objective function. The objective function is based on local flow parameters present at the design point of the centrifugal compressor. A centrifugal compressor with a vaned diffuser is considered to demonstrate the performance of this approach. By means of a variation of the beta angle distribution of the impeller and diffuser blade, 73 design variations are generated, and several local flow parameters are evaluated. Finally, the most promising flow parameter is transferred into an objective function, and an optimization is carried out. It is shown that the new approach delivers similar results as a comparable optimization with a classic objective function using two operating points for surge margin estimation, but with less computational effort since no second operating point near the surge needs to be considered.

Investigation of variable orifice plate design for centrifugal compressor low-end performance improvement

In the present paper, a compressor with variable inlet configuration upstream of the compressor wheel was investigated to improve the compressor low-end performance. As a concept study, the variable inlet configuration was assumed to be a variable orifice plate which can reduce the compressor inlet flow area when it is activated. The compressor performance with and without the initial orifice plate was assessed quantitatively using both numerical and experimental methods. The results indicated that the initial orifice plate design can improve the compressor efficiency at low speed and flow rate condition. Different orifice plate designs with different setting angles to the compressor inlet main flow direction and different radial heights were also numerically studied. It was found that: (1) changing the orifice plate setting angle from 90° for the initial design to 67° can improve compressor efficiency about 0.56% at low flow rate condition; (2) increasing the orifice plate radial height from 16% of the compressor inlet radius for the initial design to 27% can improve the compressor efficiency by 1.78% at near surge condition and extend surge margin by 9%. The results indicated that the radial height has larger effects on compressor performance than the setting angle at near surge flow rate. While increasing the orifice plate height variation can further improve compressor low-end efficiency and surge margin, there is an increased complexity of the actuation and control system.

Off-design performance improvement of twin-shaft gas turbine by variable geometry turbine and compressor besides fuel control

A novel procedure for finding the optimum values of design parameters of industrial twin-shaft gas turbines at various ambient temperatures is presented here. This paper focuses on being off design due to various ambient temperatures. The gas turbine modeling is performed by applying compressor and turbine characteristic maps and using thermodynamic matching method. The gas turbine power output is selected as an objective function in optimization procedure with genetic algorithm. Design parameters are compressor inlet guide vane angle, turbine exit temperature, and power turbine inlet nozzle guide vane angle. The novel constrains in optimization are compressor surge margin and turbine blade life cycle. A trained neural network is used for life cycle estimation of high pressure (gas generator) turbine blades. Results for optimum values for nozzle guide vane/inlet guide vane (23°/27°–27°/6°) in ambient temperature range of 25–45 ℃ provided higher net power output (3–4.3%) and more secured compressor surge margin in comparison with that for gas turbines control by turbine exit temperature. Gas turbines thermal efficiency also increased from 0.09 to 0.34% (while the gas generator turbine first rotor blade creep life cycle was kept almost constant about 40,000 h). Meanwhile, the averaged values for turbine exit temperature/turbine inlet temperature changed from 831.2/1475 to 823/1471°K, respectively, which shows about 1% decrease in turbine exit temperature and 0.3% decrease in turbine inlet temperature.

Investigation of the Combined Effect of Variable Inlet Guide Vane Drift, Fouling, and Inlet Air Cooling on Gas Turbine Performance

Variable geometry gas turbines are susceptible to various malfunctions and performance deterioration phenomena, such as variable inlet guide vane (VIGV) drift, compressor fouling, and high inlet air temperatures. The present study investigates the combined effect of these performance deterioration phenomena on the health and overall performance of a three-shaft gas turbine engine (GE LM1600). For this purpose, a steady-state simulation model of the turbine was developed using a commercial software named GasTurb 12. In addition, the effect of an inlet air cooling (IAC) technique on the gas turbine performance was examined. The design point results were validated using literature results and data from the manufacturer’s catalog. The gas turbine exhibited significant deterioration in power output and thermal efficiency by 21.09% and 7.92%, respectively, due to the augmented high inlet air temperature and fouling. However, the integration of the inlet air cooling technique helped in improving the power output, thermal efficiency, and surge margin by 29.67%, 7.38%, 32.84%, respectively. Additionally, the specific fuel consumption (SFC) was reduced by 6.88%. The VIGV down-drift schedule has also resulted in improved power output, thermal efficiency, and the surge margin by 14.53%, 5.55%, and 32.08%, respectively, while the SFC decreased by 5.23%. The current model can assist in troubleshooting the root cause of performance degradation and surging in an engine faced with VIGV drift and fouling simultaneously. Moreover, the combined study also indicated the optimum schedule during VIGV drift and fouling for performance improvement via the IAC technique.

Design of a Centrifugal Compressor with Low Solidity Vaned Diffuser (LSVD) for Large-Scale Compressed Air Energy Storage (CAES)

Compressed Air Energy Storage (CAES) has tremendous promotional value in the intermittent renewable energy supply systems. CAES has special requirements for compressor (e.g. heavy load, high pressure ratio, wide range). With advantages of higher efficiency and wider operation range, IGC (Integrally Geared Compressors) is selected to fulfill the special requirements of the large-scale CAES. To get a better aerodynamic performance, in this paper, based on the analysis of internal flow of centrifugal compressor, a multi-objective one-dimensional optimization design program was put forward combined with modified Two-Zone model and a low solidity vaned diffuser (LSVD) design method. Then, a centrifugal compressor aerodynamic component optimization design system was established with the three-dimensional blade optimization design method based on neural network and genetic optimization algorithm. Then a validation was done by redesigning the Krain-Impeller to get better performance. Finally, the aerodynamic design of the first stage of IGC was completed. The CFD calculation results indicated that the total-to-total pressure ratio of the first stage was 2.51 and the polytropic efficiency was 91.0% at the design point. What’s more, an operation margin and surge margin of the compressor was about 26.5% and 16.4% respectively.

Dynamic simulation of a solar-hybrid microturbine system with experimental validation of main parts

A micro gas turbine (MGT) is a potential option for distributed energy systems driven by fuel and solar energy. The dynamic characteristics of a solar-hybrid microturbine system are essential to its control development and performance assessment. In this paper, a dynamic model is proposed, including an MGT (T100), a tubular air receiver and a sensible thermal energy storage system, which are experimentally validated well. Based on the developed model, the dynamic responses of a solar-hybrid microturbine system in stand-alone mode are studied considering load and Direct Normal Irradiance (DNI) changes. Results show that the fuel consumption is greatly reduced by integrating solar energy, which comes at the cost of system instability; if the investigated system experiences a significant load decrease, heliostats must be oriented away from the air receiver to ensure a stable operation, whereas the load must be increased incrementally to avoid a compressor surge in the case of a significant load increase. Compared to load change, DNI change will cause smaller overshoots of the MGT’s rotational speed and surge margin. The system is simulated with measured DNI and shows that the thermal energy storage can reduce the fluctuation of combustor inlet temperature from 130.8 °C to 12.8 °C.

Performance analysis and optimized control strategy for a three-shaft, recuperated gas turbine with power turbine variable area nozzle

Performance analysis and optimization for a three-shaft, recuperated gas turbine with power turbine variable area nozzle (VAN) is conducted in this paper. A modified recuperator simulation model is obtained from recuperator experiment. A gas turbine performance simulation program is established. The influence of power turbine shaft speed on engine performance is studied and optimized control of power turbine shaft speed is proposed. Comparative performance analysis proves VAN angle control improves engine performance, but leads to less compressor surge margin and increased risk of over temperature. The optimized control of VAN angle under different safety operation temperature limits and ambient temperature is investigated. Power turbine shaft speed barely influences the optimized control of VAN angle, but temperature limits and ambient temperature greatly do. By decoupling power turbine shaft speed and VAN angle, an optimized control strategy for power turbine shaft speed and VAN angle is proposed, which brings 6.37%, 15.88%, 47.80% increases in output power, and 10.84%, 25.59%, 64.97% increase in thermal efficiency when relative high-pressure shaft speed is 0.95, 0.90 and 0.85, respectively. Maximum thermal efficiency could be achieved at part-load conditions rather than design-point if temperature limit is relaxed.

ОПРЕДЕЛЕНИЕ ДРОССЕЛЬНОЙ ХАРАКТЕРИСТИКИ ТУРБОВАЛЬНОГО ГТД НА ОСНОВЕ МЕТОДА МАТЕМАТИЧЕСКОГО МОДЕЛИРОВАНИЯ С ИСПОЛЬЗОВАНИЕМ ОДНО- И ДВУМЕРНЫХ ПОДХОДОВ К РАСЧЕТУ ПАРАМЕТРОВ КОМПРЕССОРА

The results of mathematical modeling processes in the turboshaft gas turbine engine (GTE) are presented. The using calculation method based on a high-level GTE mathematical model, which is founded on a multi-stage axial compressor blade-to-blade description. The model was developed at the Aviation Theory Chair of National Aerospace University “KhAI”. The model is based on a multistage axial compressor thermodynamic parameters calculations using a 1D and 2D approaches to analyzing of the flow. The model named above allows one to take into account air intakes from of the compressor blade gaps, as well as adjusting the angles of installation of the rotary stator vanes depending on the rotational speed. The GTE model has a modular structure. To determine the compressor parameters the modules for 1D or 2D flow calculation can be connected. As the initial data, besides the data traditionally specified in the 1st level GTE models it is necessary to set the geometrical parameters of the compressor flow path and blades on the medium radius (for the 2nd level GTE model) or along with the blade height (for the 3rd level). Both calculating compressor parameters methods are verified and have a fairly wide experience of practical use. The article presents the results of calculating the maps of the GTE multi-stage compressor using one- and two-dimensional approaches. Comparison of the compressor performances achieved by using of these two methods among themselves and with the experimental data has shown their good agreement. The approach used to simulate the flow in compressors makes it possible to estimate, by calculation, the surge margin, to consider the incidence angles and other flow parameters in the blade gaps in a wide range of GTE operation modes. Such results, as well as a comparison with experimental data, are presented in the article. The article also demonstrates the results of applying the described above model to the gas turbine engine performances calculation. The engine has the 12-stage axial compressor with the stator blades position of the first stages regulation. The calculated line of joint operation modes of the gas generator units, the dependence of the power and specific fuel consumption on the rotational speed. Presented are the processes in GTE on stationary modes analyzing results given in the article showed the used model advantage, reliability and expediency of its practical application.

Off-design performance analysis of hybridised aircraft gas turbine

ABSTRACTAn advanced geared turbofan with year 2035 technology level assumptions was established and used for the hybridisation study in this paper. By boosting the low-speed shaft of the turbofan with electrical power through the accessory gearbox, a parallel hybrid concept was set up. Focusing on the off-design performance of the hybridised gas turbine, electrical power input to the shaft, defined as positive hybridisation in this context, generally moves the compressor operation towards surge. On the other hand, the negative hybridisation, which is to reverse the power flow direction can improve the part-load operations of the turbofan and minimise the use of compressor handling bleeds. For the pre-defined mission given in the paper, negative hybridisation of descent, approach and landing, and taxi operations with 580 kW, 240 kW and 650 kW, respectively was found sufficient to keep a minimum compressor surge margin requirement without handling bleed.Looking at the hybridisation of key operating points, boosting the cruise operation of the baseline geared turbofan is, however, detrimental to the engine efficiency as it is pushing the cruise operation further away from the energy optimal design point. Without major modifications to the engine design, the benefit of the hybridisation appears primarily at the thermomechanical design point, the hot-day take-off. With the constraint of the turbine blade metal temperature in mind, a 500kW positive hybridisation at hot-day take-off gave cruise specific fuel consumption (SFC) reduction up to 0.5%, mainly because of reduced cooling flow requirement. Through the introduction of typical electrical power system performance characteristics and engine performance exchange rates, a first principles assessment is illustrated. By applying the strategies discussed in the paper, a 3% reduction in block fuel burn can be expected, if a higher power density electrical power system can be achieved.

Characterization of the Performance of a Turbocharger Centrifugal Compressor by Component Loss Contributions

The performance of an automotive turbocharger centrifugal compressor has been studied by developing a comprehensive one-dimensional (1D) code as verified through experimental results and a three-dimensional (3D) model. For 1D analysis, the fluid stream in compressor is modeled using governing gas dynamics equations and the loss mechanisms have been investigated and added to the numerical model. The objective is to develop and offer a 1D model, which considers all loss mechanisms, slip, blockage and also predicts the surge margin and choke conditions. The model captures all features from inlet duct through to volute discharge. Performance characteristics are obtained using preliminary geometry and the blade characteristics. A 3D numerical model was also created and a viscous solver used for investigating the compressor characteristics. The numerical model results show good agreement with experimental data through compressor pressure ratio and efficiency. The effect of the main compressor dimensions on compressor performance has been investigated for wide operating range and the portions of each loss mechanism in the impeller. Higher pressure ratio is achievable by increasing impeller blade height at outlet, impeller blade angle on inlet, diffuser outlet diameter and by decreasing impeller shroud diameter at inlet and blade angle at outlet. These changes may cause unfavorable consequences such as a lower surge margin or shorter operating range, which should be compromised with favorable changes. At lower rotational speeds, impeller skin friction mainly impacts the performance and at higher rotational speeds, impeller diffusion, blade loading and recirculation losses are more important. The results allow the share of each loss mechanism to be quantified for different mass flow rates and rotational speed, shedding new light on which losses are most important for which conditions. For a turbocharger, which must operate over a wide range of conditions, these results bring new insight to engineers seeking to optimize the compressor design as part of an internal combustion engine system.

Effect of fuel composition of LNG on the performances and operating characteristics of a gas turbine cycle

The effect of natural gas compositions on the thermodynamic performance characteristics of the single-shaft gas turbine cycle is analyzed in this study. The fuel characteristics are signified by H/C ratio and heating value, then the system are analyzed, and the full off-design analysis is performed by using TIT, TET, and power control. As the heating value of natural gas decreases, power output increases due to the increased mass flow passing through the turbine for all control methods. Additionally, regardless of the control method, the compressor surge margin is reduced and the turbine blade temperature is raised, making the gas turbine operation extremely vulnerable. Most parameters are sensitively affected by the HC ratio of fuel with TIT control. When the power control is used, gas turbine efficiency is reduced due to the increased operation of the compressor. The results are expressed by polynomial equations relative to each design value. In terms of the performance curves of the gas turbine cycle, the trends of most parameters accord with high H/C ratio and low heating value.

Turbofan Engine Performance Deterioration Due To Fan Erosion

In this paper, the performance deterioration for the fan due to geometry changes by erosion is investigated and discussed. Furthermore, the fan life time is predicted. The fan in concern is installed in General Electric CF6-50 high bypass turbofan engine. It is large in diameter and has highly twisted blades. Moreover, the overall engine performance degradation due to fan performance deterioration is predicted. The studied aircraft mission lasts on the average for 3.5 hours. 7.5% of the mission time is near the ground and the remaining 92.5% is for the cruising condition. The life time of the fan is divided into 2000 cycles intervals. After each interval the fan geometry is updated and the flow field is solved to predict the fan performance. The fan performance is predicted after 2000, 4000, 6000, and 8000 cycles. Finally the fan performance characteristics are used to determine the performance deterioration in the CF6 turbofan engine. It is found that, fan erosion causes a remarkable degradation on both the fan and the engine performances. After 8000 operating cycles it was found that, the surge margin is reduced from 10.5% and 9.77% to 2.5% and 1.5% at cruise and takeoff, respectively. Furthermore, there is a decrease of 2.35% and 3.55% in the fan pressure ratio and fan efficiency for both cruise and takeoff, respectively. The fan life time based on the blend limits provided by the engine manufacturer is found to be after nearly 5000 operating cycles.

Predicting the performance of a micro gas turbine under solar-hybrid operation

There are currently no commercial solar-hybrid gas turbine systems readily available off-the-shelf. Several operation and control challenges still exist, and significant development effort is still required to provide technically proven units. To address this gap, this study modeled the performance of a solar-hybrid micro gas turbine (MGT) system, considering both steady-state and transient operation. Based on the component matching, the equilibrium running point shifted on the compressor characteristic, to counter the additional system pressure losses, and ensure a useful work output, albeit with a reduced surge margin. Solar-hybrid operation was only possible for solar share of at least 20%, while the work output and cycle thermal efficiency drop below standard operation levels beyond certain solar share. In contrast to standard operation, a higher nominal work output of 20 kW, at a lower SFC of 0.0004 kg/kWh and a higher cycle thermal efficiency of 8% was predicted, the latter potentially increasing to 20% with recuperation. Solar-hybrid equilibrium running could eliminate the risk of running into compressor surge. The findings from this study should guide operation and control strategies for the proposed, and future solar-hybrid MGT systems, which should in turn contribute to their development and commercialization.

On the Effect of Engine Pulsations on the Performance of a Turbocharger Centrifugal Compressor

In an internal combustion engine, the centrifugal compressor is placed upstream of the inlet manifold and therefore, it is exposed an unsteady flow regime caused by the inlet valves of the cylinder arrangement. This valve motion sets a pulsating state at the compressor exit, having greater influence when the operation is near the surge margin of the compressor. This paper presents the experimental results of the evaluation of the surge dynamics on a compressor with induced downstream pulsating flow. Different pulsation levels are achieved by the variation of three different parameters on the induced pulse: pulse frequency, amplitude, and system storage volume (plenum). Each pulse parameter was evaluated independently in order to assess its effect on the compressor stability limit. The main effect on the surge margin of the compressor was found to be due to the presence of a storage volume in the system for all cases (steady/pulsating condition) and at all frequencies. It was found that the magnitude of the pulse frequency determines the hysteresis behavior of the system that leads to a phase difference between the convected terms and the acoustic dominated terms, and therefore this affects the onset of flow instability, surge, in the compression system under study.

Acoustic and pressure characteristics of a ported shroud turbocompressor operating at near surge conditions

The operation of compressor at lower mass flow rates is limited by surge which is marked by large fluctuations in operational variables and accompanied by significant increase in noise. Ported shroud casing treatment is a widely used method to control the flow near unstable conditions in order to obtain a stable operation and enhance deep surge margin. The research on the acoustic effects of the ported shroud design is limited. Therefore, this paper numerically characterises the acoustic features of a turbocharger compressor with ported shroud design operating at marginal or soft surge conditions and investigates the correlation between acoustic characteristics and the spatial flow structures. The acoustic and the flow field features are analysed using spectral signatures obtained from an experimentally validated numerical model using both performance and acoustic measurements. Propagation of the frequency content through the ducts has been estimated with the aid of the beamforming and method of characteristics to enhance the content coming from the compressor. Expected acoustic phenomena such as rotating order tones and blade passing peaks are correctly identified in the modelled spectrum with the limitation to capture the specific broadband features. Hence, the numerical model can be used to further the research encompassing the impact these flow enhancement solutions have on the noise emission of the turbocharger. Inspection of the flow field shows radially exiting fluid at the ported shroud slot leading to the formation of the high-speed jets exiting the ported shroud cavity. Circumferential propagation of the stall cells is also identified in the impeller. Further inspection of the pressure field through modal decomposition implies the localisation of the energetic noise sources in the impeller downstream components. The influence of the ported shroud cavity on the acoustic characteristic of the compressor is not significant and is limited to the propagation of the tonal noise in the direction of impeller upstream.

Test Rig for Emulation of Turbocharged SOFC Plants

This work is devoted to an emulator test rig designed for experimental analysis on SOFC-based plants pressurised by a turbocharger. The utilization of a turbocharger for SOFC pressurization aims to reduce the machine costs, due to the large mass production of this component. This emulator rig is an essential plant to perform tests on the component integration, dynamic operations, control system development and prevention of risky operative conditions (e.g. surge). These are essential issues to be solved before developing expensive complete prototypes and the related commercialization. This experimental plant is based on a pressure vessel for emulating the thermal (combustor and inert ceramic material) and fluid dynamic (the volume) responses. The vessel pressurisation is obtained with a turbocharger, where the exhaust flow operating in the turbine powers the compressor. The plant is also equipped with a recuperator and with different valves for control and flexibility reasons (bleed, compressor/turbine bypass, and recuperator bypass). Preliminary experimental results are included in this work focusing attention on the turbocharger choice and on the component constraints. In details, these are the necessary experiments for choosing the suitable machine for the rig (with a good surge margin for this component coupling).

Dynamic Effect of Cold-Air Bypass Valve for Compressor Surge Recovery and Prevention in Fuel Cell Gas Turbine Hybrid Systems

A large volume between compressor and turbine is present in fuel cell gas turbine hybrid systems. The substantially larger compressor plenum volume modifies the dynamic behaviour of these systems, increasing the risk of compressor surge during transients and subsequent destruction of both turbomachinery and fuel cell components. Diverting part of the compressor inlet flow directly to the turbine inlet through a cold-air bypass valve, bypassing the fuel cell stack, has been proven to be an effective method to increase the surge margin during normal operation and also to recover the machine from fully developed surge. This study investigates the dynamic effect of different cold-air bypass valve opening/closing procedures, especially steps and ramps changing the valve fractional opening. This analysis was carried out with reference to the Hybrid Performance (Hyper) facility: a hybrid system emulated using hardware and a cyber-physical fuel cell system at the National Energy Technology Laboratory (NETL), U.S. Department of Energy (DOE). Simulations performed on a Matlab®-Simulink® dynamic model of the system based on Greitzer’s theory showed a different behaviour varying the valve fractional opening with steps or ramps. Many experimental tests were performed on the Hyper facility to confirm the trends obtained from the simulations results. From the outcomes of this study, it has been possible to determine how to maximize the surge recovery effect of the cold-air bypass valve opening and to minimize surge related risks during the valve closure.

The impact of heat exchanger degradation on the performance of a humid air turbine system for power generation

This paper aims to analyse the impact of air-water heat exchanger’s degradation on the performance of a reheated humid air turbine system for power generation applications. A number of thermal models to simulate the performance of the various sub-systems was put together and validated against experimental data. The performance degradation of the heat exchangers is characterised by means of a degradation coefficient, which is used to drive the cycle into off-design and part-load conditions when degradation is accounted for. Three heat exchanger design scenarioswere investigated, namely a low, a medium and a high effectiveness in order for the impact of the degradation penalties on cycle thermal efficiency to be determined. The performance deterioration of the heat exchangers is also analysed from an exergetic point of view in order to identify the key sources that penalise the thermal efficiency of the humid air turbine system. The degradation analysis shows that typical levels of intercooler deterioration cause notable penalties in the cycle performance, reducing its thermal efficiency and power output by 1.8 percentage points and 28% respectively compared to the un-degraded operation. The exergy analysis showed that the deterioration of the intercooler also penalises the efficiency of the low pressure compressor and reheater, which contribute to the performance penalty of the cycle too. It is also found that the degradation of the intercooler can also lead to operability penalties at the low pressure compressor by reducing its surge margin. The effects of the deterioration of the aftercooler and economiser were found to only have a weak effect on the system’s performance. The outcome of the work constitutes a step forward in understanding of the performance behaviour of an advanced cycle when heat exchanger degradation is present.

Acoustic characteristics of a ported shroud turbocompressor operating at design conditions

In this article, the acoustic characterisation of a turbocharger compressor with ported shroud design is carried out through the numerical simulation of the system operating under design conditions of maximum isentropic efficiency. While ported shroud compressors have been proposed as a way to control the flow near unstable conditions in order to obtain a more stable operation and enhance deep surge margin, it is often assumed that the behaviour under stable design conditions is characterised by a smooth, non-detached flow that matches an equivalent standard compressor. Furthermore, research is scarce regarding the acoustic effects of the ported shroud addition, especially under the design conditions. To analyse the flow field evolution and its relation with the noise generation, spectral signatures using statistical and scale-resolving turbulence modelling methods are obtained after successfully validating the performance and acoustic predictions of the numerical model with experimental measurements. Propagation of the frequency content through the ducts has been estimated with the aid of pressure decomposition methods to enhance the content coming from the compressor. Expected acoustic phenomena such as ‘buzz-saw’ tones, blade passing peaks and broadband noise are correctly identified in the modelled spectrum. Analysis of the flow behaviour in the ported shroud shows rotating structures through the slot that may impact the acoustic and vibration response. Further inspection of the pressure field through modal decomposition confirms the influence of the ported shroud cavity in noise generation and propagation, especially at lower frequencies, suggesting that further research should be carried out on the impact these flow enhancement solutions have on the noise emission of the turbocharger.

Performance prediction methodology and analysis of a variable pitch fan turbofan engine

The objective of this paper is development and application of a methodology for preliminary analysis of variable pitch fan (VPF), both as a separate component and as a module integrated into a short-medium range geared turbofan engine developed within European FP7 project ENOVAL. For this purpose, a high bypass ratio two spool geared turbofan engine model was constructed in software PROOSIS. A VPF performance modeling methodology was then developed using 3D steady RANS CFD produced fan maps as baseline; the CFD maps characterized five discrete fan pitch angle settings. In order to represent those maps in PROOSIS and add the pitch angle as a degree of freedom, they were transformed into the Map Fitting Tool (MFT) reference frame. Once the complete VPF turbofan model was in place, engine mission optimization experiments were carried out. The resulting performance is characterized by a good capability to control the fan surge margin, without degrading the engine fuel consumption. This paper represents a new contribution on the topic firstly by coupling a 0D engine performance code with a 3D RANS calculation, and then by introducing the concept of MFT maps with an additional degree of freedom as the interface between the two.