Simple Cycle Gas Turbine Engine Research Articles

Maximum-efficiency architectures for steady-flow combustion engines, I: Attractor trajectory optimization approach

In this paper, we present a new systematic optimization approach to identify maximum-efficiency architectures for steady-flow combustion engines. Engine architectures are modeled as trajectories in the thermodynamic state space, and the optimal engine architecture is deduced by minimization of total irreversibility over all permissible trajectories that satisfy device constraints. In the past, both parametric and functional minimizations of engine irreversibility have been studied extensively. Our approach combines the functional optimization aspect (i.e., optimization of the process sequence or engine cycle) and the parametric optimization aspect (i.e., optimization of process lengths or parameters in the engine cycle) to identify the maximum-efficiency architecture permitted by physics. The concept central to this approach is that of chemical-equilibrium attractor states in the thermodynamic state space. It enables semi-analytical optimization for reactive engines with no need to model the detailed combustion dynamics. In this study we present the motivation and theoretical details of this method. In Part II of this study, this approach is applied to optimize the class of simple-cycle gas turbine engines. It is shown that even with modest device technology (e.g., turbine inlet temperature of 1650 K), maximum efficiency above 50% can be achieved in simple-cycle engines.

Maximum-efficiency architectures for steady-flow combustion engines, II: Work-regenerative gas turbine engines

In this paper we identify the maximum-efficiency architecture allowed by physics for simple-cycle gas turbine engines. This is achieved by functional minimization of total irreversibility using the attractor trajectory optimization approach developed in the first part of this study. It is shown that maximization of efficiency requires the combustion process to be performed in a part-adiabatic and part-isothermal manner. The optimal split of fuel to be burned between the adiabatic and isothermal segments is determined to be a function of turbomachinery irreversibilities and the turbine-blade temperature limit. The resulting optimal architecture has higher efficiency than both the traditional Brayton cycle (that employs only adiabatic combustion) and a fully-reheat cycle (that employs only isothermal combustion).

Analysis of a small steam injected gas turbine system with heat recovery

This paper describes a methodology and results for the analysis of a small steam injected gas turbine cogeneration system. A performance analysis program for the gas turbine engine is utilized with modifications required for the model of steam injection and the heat recovery steam generator (HRSG). The object of simulation is a simple cycle gas turbine engine under development which adopts a centrifugal compressor. The analysis is based on the off-design operation of the gas turbine and the compressor performance map is utilized. Analyses are carried out with the injection ratio as the main parameter. The effect of steam injection on the power and efficiency of gas turbine and cogeneration capacity is investigated. Also presented is the variation in the main operating parameters inside the HRSG. Remarkable reduction in NOx generation by steam injection is confirmed. In addition, it is observed that for the 100% power operation the temperature of the cooled first nozzle blade decreases by 100.deg. C at full steam injection, which seems to have a favorable effect on the engine life time.

Design and Test of a Small, High Pressure Ratio Radial Turbine

This paper describes the aerodynamic design and rig test of a radial inflow turbine having a rotor tip diameter of 4.58 inches. The single-stage turbine was designed for use in the Sundstrand Power Systems (SPS) T-100 Multipurpose Small Power Unit (MPSPU). The T-100 is a small, single-shaft, simple-cycle gas turbine engine intended for airborne, vehicular, and ground-based auxiliary power application. Nominal power output of the engine is 50 hp, with growth capability to 100 hp with minimal modification. Aggressive specific fuel consumption goals for the engine led to a demanding turbine efficiency target of 87 percent total to static, referred to exhaust diffuser exit, at an expansion ratio of 5.7:1 and a flow rate of 0.73 lb/s. Details of the design approach are given, together with test results from the turbodrive rig. The results include overall stage mapping and rotor exit surveys.

Performance of simple cycle gas turbine engines in two modes of operation

The gas turbine engine is finding progressively more acceptance in different applications with different operation and performance requirements. In this work, a model free power gas turbine engine, driving an electric dynamometer, is run in two modes, namely, a single and two-shaft operation using LPG as fuel. Experimental readings under controlled operating conditions and relevant calibration curves were used to calculate performance, including net power output, specific fuel consumption and engine thermal efficiency. Results show that operating a two-shaft engine in the single-shaft mode would boost the part load power tremendously. However, the torque characteristic of the two-shaft mode at part load is superior.

Optimal State-Space Control of a Gas Turbine Engine

An analog fuel control for a gas turbine engine was compared with several state-space derived fuel controls. A single-spool, simple cycle gas turbine engine was modeled using ACSL (high level simulation language based on FORTRAN). The model included an analog fuel control representative of existing commercial fuel controls. The ACSL model was stripped of nonessential states to produce an eight-state linear state-space model of the engine. The A, B, and C matrices, derived from rated operating conditions, were used to obtain feedback control gains by the following methods: (1) state feedback; (2) LQR theory; (3) Bellman method; and (4) polygonal search. An off-load transient followed by an on-load transient was run for each of these fuel controls. The transient curves obtained were used to compare the state-space fuel controls with the analog fuel control. The state-space fuel controls did better than the analog control.