Research Papers: Gas Turbines: Turbomachinery

A Research on Waste-Gated Turbine Performance Under Unsteady Flow Condition

[+] Author and Article Information
Q. Deng

Department of Mechanical Engineering,
Powertrain Vehicle Research Centre,
University of Bath,
Bath BA2 7AY, UK
e-mail: qd226@bath.ac.uk

R. D. Burke

Department of Mechanical Engineering,
Powertrain Vehicle Research Centre,
University of Bath,
Bath BA2 7AY, UK
e-mail: R.D.Burke@bath.ac.uk

Q. Zhang

Department of Mechanical Engineering,
Powertrain Vehicle Research Centre,
University of Bath,
Bath BA2 7AY, UK
e-mail: Q.Zhang@bath.ac.uk

Ludek Pohorelsky

Honeywell Technology Solutions, CZE,
Turanka 100,
Brno 62700, Czech Republic
e-mail: Ludek.Pohorelsky@Honeywell.com

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 21, 2016; final manuscript received October 26, 2016; published online January 24, 2017. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(6), 062603 (Jan 24, 2017) (12 pages) Paper No: GTP-16-1459; doi: 10.1115/1.4035284 History: Received September 21, 2016; Revised October 26, 2016

Turbochargers are key components of engine air-paths that must be carefully considered during the development process. The combination of fluid, mechanical, and thermal phenomenon make the turbocharger a highly dynamic and nonlinear modeling challenge. The aim of this study is to quantify the dynamic response of the turbocharger system across a frequency spectrum from 0.003 Hz to 500 Hz, i.e., for exhaust gas pulsation in steady state, load steps, and cold start drive cycles, to validate the assumption of quasi-steady assumptions for particular modeling problems. A waste-gated turbine was modeled using the dual orifice approach, a lumped capacitance heat transfer model, and novel, physics-based pneumatic actuator mechanism model. Each submodel has been validated individually against the experimental measurements. The turbine inlet pressure and temperature and the waste-gate actuator pressure were perturbed across the full frequency range both individually and simultaneously in separate numerical investigations. The dynamic responses of turbine housing temperature, turbocharger rotor speed, waste-gate opening, mass flow, and gas temperatures/pressures were all investigated. The mass flow parameter exhibits significant dynamic behavior above 100 Hz, illustrating that the quasi-steady assumption is invalid in this frequency range. The waste-gate actuator system showed quasi-steady behavior below 10 Hz, while the mechanical inertia of the turbine attenuated fluctuations in shaft speed for frequencies between 0.1 and 10 Hz. The thermal inertia of the turbocharger housing meant that housing temperature variations were supressed at frequencies above 0.01 Hz. The results have been used to illustrate the importance of model parameters for three transient simulation scenarios (cold start, load step, and pulsating exhaust flow).

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Fig. 1

Schematic overview of turbine model showing flow paths, heat transfer, and waste gate model structure. Perturbed boundary conditions are turbine inlet temperature and pressure (T3, P3) and waste gate actuator vacuum pressure (Pvac).

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Fig. 2

Schematic diagram of volumetric breakdown for dual-orifice turbine model

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Fig. 3

Overview of the heat transfer model: (a) schematic of heat transfer process and (b) diagram of simplified heat transfer lumped model

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Fig. 4

Diagram of waste-gate actuator model (P4 and P5 correspond to the pressures indicated in Fig. 1)

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Fig. 5

Illustration of waste gate effective area calculation

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Fig. 6

Steady-state test data for turbine performance comparing reference manufacturer map (from gas stand tests) and simulated test data using the dual orifice model

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Fig. 7

Dual-orifice model validation comparing dual orifice model with map-based data

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Fig. 8

Schematic of the waste-gate actuator test rig

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Fig. 9

Measured and simulated waste gate actuator displacement (x)

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Fig. 10

Normalized excitation signals for selected frequencies (note log scale on time axis)

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Fig. 11

(a) Inlet parameters, (b) turbine mass flow, (c) turbospeed, and (d) turbine housing temperature for temperature only variation (case 1)

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Fig. 12

(a) Inlet parameters, (b) turbine mass flow, (c) turbospeed, and (d) turbine housing temperature for pressure only variation (case 2)

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Fig. 13

(a) Inlet parameters, (b) waste-gate effective diameter, (c) mass flow through rotor, (d) mass flow through volute, (e) turbospeed, and (f) turbine wall temperature for actuator pressure only variation (case 3)

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Fig. 14

(a) Inlet parameters, (b) turbospeed, and (c) mass flow through rotor for temperature and pressure variations (case 4)

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Fig. 15

(a) Inlet parameters, (b) turbospeed, and (c) mass flow through rotor for all parameters variation (case 5)

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Fig. 16

(a) Mass flow, (b) turbine wall temperature, (i) turbospeed, and (d) waste-gate effective diameter amplitude across the frequency spectrum for all cases




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