🔥 Steam-Injected Gas Turbine (STIG / Cheng)

Calculate Steam-Injected Gas Turbine (STIG / Cheng cycle) performance: power boost gain (+40-70%), thermal efficiency, HRSG steam duty, and turbine expansion.

⚡ Fortran 90 Engine Double Precision (IEEE 754) ✓ ISO / ASME Validated

Thermodynamics

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👁️ Views 24

⚡ Solves 18

💾 Downloads 461 📦 Fortran Code 11.4 KB

📅 Released Jun 2026

⏱️ Latency < 1 ms

🔥 Dual-Fluid Gas Turbine & HRSG Steam Injection Manifold

Real-time visual simulation: High-temperature exhaust generating superheated steam injected into combustor for massive power boost

📝 Configuration & Presets

✈️ Aeroderivative LM5000 STIG ⚡ Frame 6B Peaker Boost (+50%) 🔥 Cheng Dual-Fluid Cycle (18% Steam) 🏭 Microturbine Distributed CHP

⚡ Gas Turbine Aerothermodynamics

Pressure Ratio r_p:

Turbine Inlet Temp TIT [°C]:

Ambient Air Temp T_amb [°C]:

Air Mass Flow ṁ_air [kg/s]:

💨 Steam Injection & Heat Recovery (HRSG)

Steam Injection Ratio ṁ_s/ṁ_a [%]: Typical: 5% to 15%

Injected Steam Temp [°C]:

⚙️ Turbomachinery Efficiencies

Compressor Isentropic Eff. η_c:

Turbine Isentropic Eff. η_t:

STIG / Cheng Dual-Fluid Formulation:
• Turbine Expansion: Ẇ_turb = (ṁ_air · c_p,air + ṁ_steam · c_p,steam) · TIT · [1 − (1/r_p)^(γ−1)/γ] · η_t
• Power Boost: ΔP_net / P_simple ≈ +40% to +70%
• Steam specific heat (c_p,steam ≈ 2.15 kJ/kg·K) is ~2× air, multiplying expansion power.
• Drastic reduction in thermal NO_x emissions in combustor.

📊 STIG Performance Results

📊 Output Summary
💾 Fortran Source

STIG Net Electrical Power Output

70.77 MW (vs 44.44 MW simple)

STIG Efficiency: 45.17 % (vs 34.19 %) | Boost: +59.2 %

+26.3 MW Boost

Net Power Boost Gain +59.2 % Without extra compressor power

Injected Steam Flow Rate 17.40 kg/s 12 % of air flow

HRSG Steam Heat Duty 52.20 MW Exhaust waste heat recovery

Turbine Exhaust Gas Temp 593.5 °C Inlet to HRSG boiler

📈 Power Boost Gain (%) vs Steam Injection Ratio ṁs/ṁa (%)

📉 STIG Thermal Efficiency (%) vs Pressure Ratio r_p

=================================================================
 THERMOFLUIDCALC — STEAM-INJECTED GAS TURBINE (STIG / CHENG) REPORT
=================================================================
Case Title                 : Aeroderivative LM5000 High-Efficiency STIG Cogeneration
Gas Turbine Parameters     : Pressure Ratio rp = 25.0, TIT = 1180.0 C, Air Flow = 145.0 kg/s
Steam Injection System     : Injection Ratio = 12.0 % (m_steam = 17.40 kg/s), Steam Temp = 450.0 C
-----------------------------------------------------------------
STIG NET POWER OUTPUT      : 70.773 MW
Simple Cycle Baseline Power: 44.443 MW
POWER BOOST GAIN           : +59.24 % (+26.330 MW)
STIG THERMAL EFFICIENCY    : 45.175 % (vs 34.189 % simple)
HRSG Steam Heat Recovery   : 52.200 MW
Turbine Exhaust Temperature: 593.5 deg C
NOx Reduction Effect       : Substantial flame temperature cooling & steam dilution
=================================================================

📘 Calculation Methodology & STIG Standards

Dual-Fluid Expansion Principle

Injecting superheated steam increases mass flow and specific heat ($c_{p,steam} \approx 2.15\,\text{kJ/kg}\cdot\text{K}$) across turbine expanders without demanding additional compressor parasitic power.

Single-Shaft Simplicity

Achieves combined-cycle-class efficiency ($\eta \approx 45 - 50\%$) without the capital complexity of a separate steam turbine, condenser, cooling tower, and vacuum system.

Key Engineering Assumptions

Superheated steam injected at $P_{inj} > 1.15 P_{comp}$.
Ideal gas mixture thermodynamics for exhaust products + steam.
Applicable to aeroderivative turbines, peaker power stations, and industrial cogeneration.

ThermoFluidCalc Engineering Report