This study involved computational modelling and analysis only and did not involve human participants, human-derived materials, animals, or identifiable personal data. Therefore, institutional ethics approval and informed consent were not required. The tools used in this protocol are listed in the Table of Materials.
1. Overall study design
The computational workflow was designed to assess the steady-state performance of a representative recuperated micro gas turbine and to identify favorable operating states under prescribed load conditions. The workflow comprised definition of component, environmental, fuel, and operating-bound inputs; calculation of thermodynamic states and performance indicators for each candidate operating point; physical-feasibility screening; generation of one- and two-dimensional performance maps; load-specific deterministic grid-search evaluation; and sensitivity analysis. Selected operating states were compared with the corresponding baseline conditions, and their responses to variations in ambient temperature and recuperator effectiveness were subsequently evaluated. The overall computational workflow is summarized schematically in Figure 1.

Figure 1: Overall schematic of the numerical performance evaluation and operational optimization workflow for a micro gas turbine system. The workflow proceeds from definition of the micro gas turbine configuration and operating inputs through thermodynamic numerical modelling and parametric performance evaluation to an operational optimization module that evaluates the feasible operating domain. Selected operating points are subsequently compared with baseline performance maps to quantify changes in thermal efficiency, specific fuel consumption, and net power output under the evaluated distributed-generation operating conditions. Please click here to view a larger version of this figure.
The model inputs included ambient temperature, ambient pressure, component efficiencies, fuel lower heating value, recuperator effectiveness, compressor pressure ratio, turbine inlet temperature, and load factor. Admissible ranges and discrete increments were prescribed for compressor pressure ratio, turbine inlet temperature, load factor, ambient temperature, and recuperator effectiveness. These quantities defined the operating domain used for performance mapping, feasibility screening, deterministic grid-search evaluation, and sensitivity analysis.
For each candidate operating point, the compressor outlet temperature and compressor specific work were calculated from the prescribed inlet condition and compressor pressure ratio. The turbine outlet state and turbine specific work were then determined from the prescribed turbine inlet temperature, expansion ratio, and turbine isentropic efficiency. The recuperator outlet temperature was calculated using the prescribed recuperator effectiveness and turbine exhaust temperature, followed by determination of the fuel-to-air ratio from the combustor energy balance. Net specific work, thermal efficiency, net power, and specific fuel consumption were subsequently calculated. Candidate states that violated the prescribed parameter bounds, yielded non-positive net power, produced non-physical temperature relations, or contained undefined numerical outputs were excluded. Physically feasible states were retained for performance-map generation and deterministic grid-search evaluation.
Baseline performance maps were generated by varying individual model inputs to construct one-dimensional response curves and by varying compressor pressure ratio and turbine inlet temperature simultaneously to construct two-dimensional thermal-efficiency and specific-fuel-consumption maps. The evaluated inputs and calculated performance indicators were retained in tabular form for plotting and subsequent comparison. Load-specific deterministic grid searches were performed independently at load factors of 1.00, 0.80, and 0.60 for Cases A, B, and C, respectively. All prescribed compressor-pressure-ratio and turbine-inlet-temperature combinations were evaluated within each load-specific grid. The feasible state with the maximum thermal efficiency was selected for each load case, while specific fuel consumption and net power were retained as associated performance outcomes. Sensitivity analysis was then conducted by repeating the baseline and selected-state calculations at prescribed ambient temperatures and recuperator-effectiveness values.
2. System definition and modelling assumptions
A representative recuperated micro gas turbine configuration was selected for the numerical analysis because recuperated architectures are widely used in small-scale distributed generation and provide a suitable basis for evaluating performance enhancement through operational optimization. The model included the principal cycle components: compressor, combustor, turbine, recuperator, and generator-equivalent output block. The working fluid was treated as an ideal gas mixture, with thermophysical behavior represented using standard gas turbine thermodynamic relations. Pressure losses and component efficiencies were introduced as prescribed input parameters.
The baseline operating domain was defined using ambient temperature, compressor pressure ratio, turbine inlet temperature, recuperator effectiveness, and load fraction as the primary independent variables. The system was assumed to operate at steady state at each simulated condition, and the numerical framework evaluated a sequence of steady operating points across the prescribed parameter space. Transient behavior, fuel-composition variation, and degradation effects were not included.
3. Design-point benchmarking against manufacturer specifications
The model was not validated against independently measured experimental data. Instead, the design-point outputs were benchmarked against published manufacturer specifications for the representative 100 kW recuperated micro gas turbine reported in the AE-T100 data sheet15. The comparison included the available rated operating information, including nominal net power, compressor pressure ratio, turbine inlet temperature, thermal efficiency, specific fuel consumption, and turbine exhaust temperature where reported. The benchmarking was used to assess whether the model reproduced the expected design-point magnitude and thermodynamic behavior of the reference unit. The comparison therefore represents agreement with manufacturer-reported specifications rather than experimental validation.
4. Computational implementation, solver settings, and convergence criteria
The computational workflow was implemented in Python 3.13.0 using NumPy 2.4.0 for numerical-array operations, SciPy 1.16 for scientific numerical routines, and Matplotlib 3.10.5 for post-processing and visualization of the calculated performance data. The implementation comprised six principal stages: input definition and parameter-bound assignment, thermodynamic-state calculation, physical-feasibility screening, parametric performance mapping, load-specific deterministic grid-search evaluation, and sensitivity analysis. Each candidate operating point was defined by ambient temperature, ambient pressure, compressor pressure-ratio operating-state value, turbine inlet temperature, load factor, recuperator effectiveness, component efficiencies, combustion efficiency, fuel lower heating value, and the remaining prescribed model parameters.
The steady-state model was evaluated sequentially for each candidate operating point. Compressor outlet temperature and compressor specific work were determined first. Turbine outlet temperature and turbine specific work were then calculated from the specified turbine inlet temperature, pressure ratio, and turbine isentropic efficiency. The recuperator air-side outlet temperature was subsequently calculated from the prescribed recuperator effectiveness and turbine exhaust temperature. The combustor energy balance was then used to determine the fuel-to-air ratio, followed by calculation of net specific work, net power, thermal efficiency, and specific fuel consumption. Because the prescribed-effectiveness thermodynamic model was evaluated using direct sequential algebraic relations, no iterative nonlinear solver was required and no residual-based convergence tolerance was applicable.
Physical-feasibility screening was applied to each evaluated operating point. Candidate states were excluded when a prescribed operating bound was violated, net power was non-positive, recuperator temperature ordering was non-physical, or calculated values were undefined or non-finite. Input parameters and calculated outputs for retained states were stored in a tabular dataset used for one- and two-dimensional performance mapping and comparison of baseline and selected operating states.
5. Computational workflow and data organization
The numerical implementation used a structured parameter dictionary containing thermodynamic constants, component efficiencies, ambient conditions, fuel properties, recuperator effectiveness, nominal system rating, load factor, and allowable bounds for compressor pressure ratio and turbine inlet temperature. Candidate operating grids were generated from arrays of compressor pressure ratio and turbine inlet temperature. For each prescribed load factor, every pressure-ratio–temperature combination in the discrete search domain was evaluated without adaptive search or early stopping.
For each candidate state, the calculated quantities included compressor outlet temperature and specific work, turbine expansion temperature and specific work, recuperator outlet temperature, fuel-to-air ratio, turbine and compressor mass-flow requirements, net specific work, fuel flow, net power, thermal efficiency, and specific fuel consumption. Each evaluated state was stored as an individual row in a tabular results structure. Stored fields included load factor, compressor pressure ratio, turbine inlet temperature, component outlet temperatures, compressor and turbine specific work, net specific work, air mass flow rate, fuel mass flow rate, net power, thermal efficiency, specific fuel consumption, and feasibility status.
Feasibility screening was applied after calculation of each candidate state. States that violated the prescribed pressure-ratio or turbine-inlet-temperature bounds, yielded non-positive net power, resulted in non-physical temperatures, or violated the recuperator temperature-ordering condition were excluded. The remaining feasible states were retained for performance mapping and load-specific selection. For each load case, the feasible candidate with the maximum thermal efficiency was identified, and the corresponding operating variables and performance indicators were reported.
The primary deterministic grid evaluated compressor pressure ratios from 3.00 to 5.00 in increments of 0.05 and turbine inlet temperatures from 850 to 1000 °C in increments of 5 °C. The resulting grid contained 41 pressure-ratio values and 31 turbine-inlet-temperature values, corresponding to 1,271 candidate states per load case. Three load factors of 1.00, 0.80, and 0.60 were evaluated, yielding 3,813 primary candidate states before feasibility screening. The objective was to maximize thermal efficiency among the retained feasible states. A dictionary-based parameter structure, NumPy arrays for candidate-grid generation and numerical operations, and a tabular results structure were used to retain candidate-state values and feasibility flags.
6. Thermodynamic formulation
The compressor outlet state was established from the specified inlet condition and compressor pressure ratio. The compressor outlet temperature was determined from the isentropic relation corrected by compressor isentropic efficiency according to Equation (1)16:
T2 = T1[1 + ηcπc (γ - 1)/γ - 1]
where (T1) and (T2) are the compressor inlet and outlet temperatures, respectively, (πc) is the compressor pressure ratio, (γ) is the specific heat ratio, and (ηc) is the compressor isentropic efficiency.
The compressor specific work was then calculated from Equation (2):
wc = cp(T2 - T1)
where cp is the specific heat at constant pressure.
The recuperator outlet temperature on the compressed air side was evaluated from the prescribed recuperator effectiveness using Equation (3)17:

where εrec is the recuperator effectiveness, T3 is the preheated air temperature entering the combustor, and T5 is the turbine exhaust temperature entering the recuperator hot side.
The combustor energy balance was used to determine the required fuel input for the target turbine inlet temperature. The fuel-to-air ratio was obtained from Equation (4)18,19,20,21:

where f is the fuel-to-air ratio, T4 is the turbine inlet temperature, ηcomb is the combustion efficiency, and LHV is the lower heating value of the fuel.
The turbine outlet temperature was determined from the turbine expansion relation corrected by turbine isentropic efficiency according to Equation (5)18,19,20,21:

where nt is the turbine isentropic efficiency and πt is the turbine expansion ratio.
The turbine specific work and net cycle specific work were then calculated from Equations (6) and (7)18,19,20,21:


The thermal efficiency was evaluated from Equation (8)14,17:

and the specific fuel consumption was computed from Equation (9)22:

where
is fuel mass flow rate and Pnet is net power output.
The governing thermodynamic relations were evaluated sequentially for each candidate operating point using direct algebraic calculations. Because component efficiencies, recuperator effectiveness, pressure losses, and operating inputs were prescribed, no iterative nonlinear solver or residual-based convergence criterion was required. Numerical validity was assessed through feasibility screening, including checks for finite numerical outputs, positive net power, physically meaningful temperatures and mass-flow rates, and valid recuperator temperature ordering19,20,21,22,23,24.
7. Code implementation
The numerical workflow comprised thermodynamic-state calculation, parametric performance mapping, deterministic grid-search evaluation, feasibility screening, and storage of calculated operating states. Baseline environmental and component inputs were specified before execution, including ambient temperature and pressure, compressor and turbine isentropic efficiencies, combustor efficiency, fuel lower heating value, recuperator effectiveness, compressor pressure ratio, turbine inlet temperature, and load factor.
The compressor relation was evaluated first, followed by the turbine expansion relation, the recuperator relation, the combustor energy balance, and the performance equations. The resulting state variables and performance indicators were retained for every feasible operating point in a tabular output dataset used for performance-map generation and comparison of baseline and selected operating states. Candidate points that violated prescribed bounds, yielded non-positive net power, produced non-physical recuperator temperature ordering, or generated undefined or non-finite numerical outputs were excluded. The retained operating points were subsequently used to generate thermal-efficiency and specific-fuel-consumption maps and to identify high-efficiency feasible states for each load case.
8. Deterministic grid-search optimization
A deterministic exhaustive grid-search screening procedure was used to identify high-efficiency steady-state candidate states within the prescribed thermodynamic feasibility bounds. Independent evaluations were conducted at load factors (LF) of 1.00, 0.80, and 0.60. Compressor pressure-ratio operating state, (πc), and turbine inlet temperature, (T4), were evaluated over the prescribed discrete domain. For the fixed-hardware micro gas turbine, (πc) was treated as a parametric proxy for the operating state rather than as an independently actuated physical control variable. It represented pressure-ratio states associated with coupled changes in shaft rotational speed, mass flow rate, fuel scheduling, and compressor–turbine matching.
For each load case, (πc) was evaluated from 3.00 to 5.00 in increments of 0.05, while (T4) was evaluated from 850 to 1000 °C in increments of 5 °C. The resulting grid contained 41 pressure-ratio values and 31 turbine-inlet-temperature values, corresponding to 1,271 candidate states per load case and 3,813 candidate states across the three reported load cases before feasibility screening. Ambient temperature and recuperator effectiveness were maintained at their reference values during the primary grid-search calculations and were varied separately during sensitivity analysis. Recuperator effectiveness was therefore treated as a prescribed model parameter rather than as a resolved off-design heat-exchanger characteristic or independently adjustable control variable.
At each candidate state, the steady-state model calculated compressor and turbine thermodynamic states, recuperator outlet temperature, fuel-to-air ratio, air and fuel mass-flow rates, net electrical power, thermal efficiency, specific fuel consumption, and turbine exhaust temperature. Candidate states were retained only when the specified parameter bounds were satisfied, net electrical power was positive, calculated outputs were finite, and temperature, mass-flow, and recuperator-ordering conditions remained physically meaningful.
The primary selection criterion was maximum thermal efficiency among the retained feasible candidates:
maxηth(πc, T4)
Specific fuel consumption was retained as an associated performance indicator and was used as the first tie-breaker when candidate states had equal thermal efficiency at the reported numerical precision. If a tie remained, the candidate with the lower turbine inlet temperature was selected. Exhaustive enumeration was performed without stochastic sampling, adaptive refinement, gradient-based optimization, heuristic optimization, initialization dependence, or early stopping. Each load-specific grid search was completed only after all 1,271 discrete candidate states had been evaluated and screened.
The prescribed-effectiveness model was evaluated through direct sequential algebraic calculations and therefore did not require an iterative nonlinear solver or residual-based convergence tolerance. Numerical validity was assessed through the prescribed feasibility-screening criteria. The selected candidate states represent model-based steady-state screening results within the prescribed assumptions and do not constitute experimentally validated or directly deployable operational-control setpoints.
Grid-resolution verification was performed to assess the adequacy of the primary discretization. A refined local grid centered on each selected primary-grid state used increments of 0.01 in (πc) and 1 °C in (T4), within ±0.10 in (πc) and ±10 °C in (T4). The maximum thermal efficiency obtained from the refined grid differed from the corresponding primary-grid result by no more than 0.05 percentage points. The selected (πc) and (T4) values remained within 0.03 and 2 °C, respectively, of the corresponding primary-grid values. This verification assessed the adequacy of the primary grid for identifying the local maximum-efficiency region within the prescribed discrete screening domain and did not establish a continuous-space global optimum.
9. Data processing and performance mapping
The calculated results were post-processed to generate operating maps and response surfaces describing the influence of the prescribed operating variables on micro gas turbine performance. Thermal efficiency, net power output, and specific fuel consumption were evaluated as functions of turbine inlet temperature, compressor pressure ratio, and load factor. The selected high-efficiency candidate states were superimposed on the baseline performance maps to indicate their locations within the modeled performance region25. Contour plots and heat maps were generated for thermal efficiency and specific fuel consumption, while line plots were used to compare baseline and selected trajectories as functions of load and power26.
The calculated outputs were examined for internal consistency by assessing the expected increase in compressor work with pressure ratio, the dependence of recuperated-cycle efficiency on turbine exhaust temperature, and the sensitivity of part-load performance to the prescribed operating parameters. Where available, calculated trends were also qualitatively cross-checked against published performance data and modeling studies to assess consistency with prior work.