Transient Modeling of a Supercritical CO 2 Power Cycle in GT-SUITE and Comparison with Test Data. Echogen Power Systems 1

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1 Transient Modeling of a Supercritical CO 2 Power Cycle in GT-SUITE and Comparison with Test Data Dr. Vamshi K. Avadhanula Systems Engineer Dr. Timothy J. Held Chief Technology Officer 1

2 Synopsis for today s discussion 1. : Brief background 2. Supercritical CO 2 cycle 3.Test system configuration 4.Modeled system configuration 5.Component validation 6.Results discussion 7.Summary 2

3 Echogen Background 2007 Echogen founded 2011 Partnership with Dresser-Rand for oil & gas market; development of EPS MW engine begins Akron, OH is the industry leader in development of supercritical CO 2 heat recovery systems. Founded in 2007, EPS has progressed from small multi-kw demonstration units to the recent multi-mw heat recovery package, the EPS Partnership with GE Marine; development of EPS MW engine begins 2014 EPS100 completes factory testing 2016 EPS30 testing commences with high-speed alternator subsystem test 2017 Pursuing commercial pilot sites for all EPS products Plans for the future Introduce additional EPS engine sizes Progress to primary power & combined cycle Industrial and nuclear applications 3

4 The Echogen supercritical CO 2 Cycle CO 2 becomes supercritical above 31 o C, 74 bar, and has properties of both liquid and gas. There is no distinct phase change when moving in/out of supercritical region. 1. Liquid CO 2 pumped to supercritical state 2. CO 2 preheated at recuperator 3. Recovered waste heat added at waste heat exchanger 4. High energy CO 2 expanded at turbine drives generator 5. Expanded CO 2 is pre-cooled at recuperator 6. CO 2 is condensed to a liquid at condenser

5 Test System: 7.3MWe net power sco 2 cycle (EPS100) 5

6 GT-SUITE System Model 6

7 Simulink Control System Model 7

8 Reason for sco 2 Cycle Model in GT-SUITE Determining the control system strategies before installing the system at customer site. Rockwell Automation/Allen Bradley (AB) control system was used in test system Future integration of AB control system with GT-SUITE using Simulink (or) FMI Currently: GT-SUITE for system model with Simulink control integration 8

9 Heat exchanger submodeling Counterflow model based on Plate & Frame heat exchanger template Inlet temperatures, pressures and flows are imposed boundary conditions Heat transferred (hot and cold sides independently) and hot/cold side pressure drops are outputs HTC and dp models include calibration to selected steady-state data points 9

10 Heat exchanger submodeling Recuperator and HRHX outlet temperatures from validation simulation Recuperator and HRHX pressure drops from validation simulation 10

11 Turbomachinery: Turbines and Compressor Models Fortran models were developed and are being used for turbomachinery Turbine maps: Two-dimensional tables for corrected mass flow rate and isentropic efficiency in terms of corrected speed and isentropic enthalpy change. w c = f w (N c, dh sc ) η s = f η (N c, dh sc ) N c = f N (N, γ, Z, T) dh sc = f dh (dh sa, γ, Z, p) w c = f 2 (w, γ, Z, T, p) Compressor maps: Two-dimensional tables, with flow coefficient and inlet fluid temperature as the primary correlating variables. η p = f ηp (Φ, T) Ψ = f Ψ (Φ, T) 11

12 Valves and Control System Model Control valves are simulated as lift valves Submodel simulation is conducted, where the throttle valve position was changed in stepwise manner and the power turbine speed response was noted. Assuming first order linear behavior of the valve, the optimal proportional and integral gains for the control loop were determined. 12

13 Model Boundary Conditions Cold water flowrate (kg/s) Cold water temperature ( o C) PHX CO 2 temperature ( o C) Generator Load (kw) 13

14 Model Control System Boundary Conditions Turbocompressor 29500RPM using PCV2 valve Power turbine speed control from initial spin to synchronous speed (24841RPM) using TCV3 and FCV41 valves System low pressure control using Accumulator and BV39 valve (open/close valve) Turbocompressor bearing drain pressure is controlled using PCV11 valve 14

15 Results: Turbocompressor Speed and Compressor Pressures 15

16 Results: Valve Positions 16

17 Results: Temperatures and Pressure Drops 17

18 Results: HRHX Temperatures and HTR 18

19 Results: Turbomachinery Performance 19

20 Thank you. Summary: sco 2 power cycle was modeled and simulated in GT-SUITE system simulation software. Individual system components were modeled and validated. Transient simulation of full system model was carried out with boundary conditions supplied from test data. Good agreement between transient simulation results and test data was observed. Future Work: Integration of AB control system and GT-SUITE system model Thermal lag behavior of heat exchangers is also been studied. For future work will include system modeling from initial startup to full load operation. For detailed report please refer to: Avadhanula, V.K., and Held, T.J., Transient Modeling of a Supercritical CO 2 Power Cycle and Comparison with Test Data, Proceedings of ASME Turbo Expo 2017, June 26-30, 2017, Charlotte, NC. Paper # GT