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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Study of Temperature Effect on Servovalve-Controlled Fuel Metering Unit

[+] Author and Article Information
Bin Wang

Jiangsu Province Key Laboratory
of Aerospace Power System,
Nanjing University of Aeronautics and Astronautics,
29 Yudao Street,
Nanjing 210016, China
e-mail: binwang@nuaa.edu.cn

Haocen Zhao

Jiangsu Province Key Laboratory
of Aerospace Power System,
Nanjing University of Aeronautics and Astronautics,
29 Yudao Street,
Nanjing 210016, China
e-mail: zhaohaocen@163.com

Ling Yu

Jiangsu Province Key Laboratory
of Aerospace Power System,
Nanjing University of Aeronautics and Astronautics,
29 Yudao Street,
Nanjing 210016, China
e-mail: 15050538150@163.com

Zhifeng Ye

Jiangsu Province Key Laboratory
of Aerospace Power System,
Nanjing University of Aeronautics and Astronautics,
29 Yudao Street,
Nanjing 210016, China
e-mail: yzf@nuaa.edu.cn

1Now his research interests are hydraulic system and auxiliaries in aero-engines.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 17, 2014; final manuscript received October 11, 2014; published online December 9, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(6), 061503 (Jun 01, 2015) (7 pages) Paper No: GTP-14-1404; doi: 10.1115/1.4028810 History: Received July 17, 2014; Revised October 11, 2014; Online December 09, 2014

It is usual that fuel system of an aero-engine operates within a wide range of temperatures. As a result, this can have effect on both the characteristics and precision of fuel metering unit (FMU), even on the performance and safety of the whole engine. This paper provides theoretical analysis of the effect that fluctuation of fuel temperature has on the controllability of FMU and clarifies the drawbacks of the pure mathematical models considering fuel temperature variation for FMU. Taking the electrohydraulic servovalve-controlled FMU as the numerical study, simulation in AMESim is carried out by thermal hydraulic model under the temperatures ranged from −10 to 60 °C to confirm the effectiveness and precision of the model on the basis of steady-state and dynamic characteristics of FMU. Meanwhile, the FMU testing workbench with temperature adjustment device employing the fuel cooler and heater is established to conduct an experiment of the fuel temperature characteristics. Results show that the experiment matches well with the simulation with a relative error no more than 5% and that 0–50 °C fuel temperature variation produces up to 5.2% decrease in fuel rate. In addition, step response increases with the fuel temperature. Fuel temperature has no virtual impact on the steady-state and dynamic characteristics of FMU under the testing condition in this paper, implying that FMU can operate normally in the given temperature range.

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References

Figures

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Fig. 1

Schematic diagram of FMU 1—linear variable differential transformer (LVDT); 2—driving piston; 3—metering valve; 4—CPDV; 5/7—balancing spring; 6—adjusting bolt; 8—COPV; and 9—servo valve

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Fig. 2

Hydraulic model of FMU in AMESim

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Fig. 3

Simulation results of COPV

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Fig. 4

Simulation results of CPDV

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Fig. 5

Flowrate response of metering valve (a) flowrate varying with displacement of valve port, (b) flowrate varying with back pressure, (c) step response of flowrate, and (d) sinusoidal response of flowrate

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Fig. 6

Testing system of FMU

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Fig. 7

Testing facilities (a) metering devices and DSP controller and (b) temperature regulator and fuel tank

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Fig. 8

Comparison of simulation and experiment under normal temperature (a) steady-state characteristic of metered flowrate reacting to valve displacement, (b) dynamic response of metered flowrate reacting to valve displacement, and (c) steady-state pressure and pressure difference at the inlet and outlet of the metering valve reacting to the spool displacement

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Fig. 9

Dynamic response of fuel flowrate varying with step change of metering valve opening under different fuel temperatures

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Fig. 10

Characteristic of flowrate varying with fuel temperatures

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Fig. 11

Simulation curves of flowrate–displacement characteristic (a) steady-state characteristic curve and (b) dynamic characteristic curve

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