Open Cycle Gas Turbine Power Research Articles

Power and efficiency optimizations for an open cycle two-shaft gas turbine power plant

In finite-time thermodynamic analyses for various gas turbine cycles, there are two common models: one is closed-cycle model with thermal conductance optimization of heat exchangers, and another is open-cycle model with optimization of pressure drop (PD) distributions. Both of optimization also with searching optimal compressor pressure ratio (PR). This paper focuses on an open-cycle model. A two-shaft open-cycle gas turbine power plant (OCGTPP) is modeled in this paper. Expressions of power output (PP) and thermal conversion efficiency (TCE) are deduced, and these performances are optimized by varying the relative PD and compressor PR. The results show that there exist the optimal values (0.32 and 14.0) of PD and PR which lead to double maximum dimensionless PP (1.75). There also exists an optimal value (0.38) of area allocation ratio which leads to maximum TCE (0.37). Moreover, the performances of three types of gas turbine cycles, such as one-shaft and two-shaft ones, are compared. When the relative pressure drop at the compressor inlet is small, the TCE of third cycle is the biggest one; when this pressure drop is large, the PP of second cycle is the biggest one. The results herein can be applied to guide the preliminary designs of OCGTPPs.

Lab-scale research on acoustically transparent stacks for hot exhaust jets in cooler cross-flow

From the exhaust stack of open cycle gas turbine power stations, the sound radiated is strongly refracted in the near-field by the thermal and velocity gradients of the jet. Research undertaken by the authors has identified that the presence of a cooler cross-flow leads to a bent-over plume downwind of the exhaust stack and a significant increase in sound in the far field by up to 10dB downwind when compared to spherical spreading. This paper is the first in a series that explores a unique “acoustically transparent silencer,” which prevents this by separating the sound from the flow. The concept of the approach is demonstrated in this paper, with aero-acoustic simulations conducted on a supercomputer and small-scale experiments in a wind tunnel. The numerical simulations have predicted the effects of using an acoustically transparent exhaust stack to reduce the refraction of sound in the near field, which reduced the lobes in the acoustic directivity downstream of the exhaust by up to 4.5 dB. This was further supported by experimental results in a wind tunnel with a reduction of up to 4 dB. These results were used to assist in the second iteration of designs for the Refrastack in a subsequent paper.

When less is more: Reducing environmental noise from open cycle gas turbines with acoustically transparent stacks

Sound radiation from large open cycle gas turbine power stations is strongly refracted by high temperature and velocity gradients in the near field of the exhaust stack outlet. Recent research by the authors has shown that in the presence of a cross-flow, the exhaust plume bends downwind and in doing so leads to significant increases in far-field sound pressure levels of up to 10dB compared to levels predicted from spherical spreading. This paper is the second in a series that explores a unique “acoustically transparent silencer,” which limits sound refraction consequently reducing downwind SPLs by separating the sound from the bulk exhaust flow. The efficacy of the approach is demonstrated two ways; initial characterization studies conducted in the reverberation chambers at the newly renovated Acoustic and Vibration Laboratory, University of Adelaide, and subsequent trials undertaken on a laboratory scale of 250 kW gas turbine in the field. Numerous designs are explored to quantify the effective insertion loss, where it will be shown as the transmission loss of the stack walls is reduced, the effective insertion loss increases, thus demonstrating that less is more. Reductions in ground-plane SPLs of up to 10 dB are achieved with less material and weight compared to traditional hard-walled stacks.

Thermodynamic Analysis and Improvement Potential of Helium Closed Cycle Gas Turbine Power Plant at Four Loads

This paper presents thermodynamic and improvement potential analyses of a helium closed-cycle gas turbine power plant (Oberhausen II) and dominant plant components at four loads. DESIGN LOAD represents optimal operating conditions that cannot be obtained in exploitation but can be used as a guideline for further improvements. In real plant exploitation, the highest plant efficiency is obtained at NOMINAL LOAD (31.27%). Considering all observed components, the regenerator (helium-helium heat exchanger) is the most sensitive to the ambient temperature change. An exact comparison shows that the efficiency decrease of an open-cycle gas turbine power plant during load decrease is approximately two and a half or more times higher in comparison to a closed-cycle gas turbine power plant. Plant improvement potential related to all turbomachines leads to the conclusion that further improvement of the most efficient turbomachine (High Pressure Turbine—HPT) will increase whole plant efficiency more than improvement of any other turbomachine. An increase in the HPT isentropic efficiency of 1% will result in an average increase in whole plant efficiency of more than 0.35% at all loads during plant exploitation. In the final part of this research, it is investigated whether the additional heater involvement in the plant operation results in a satisfactory increase in power plant efficiency. It is concluded that in real exploitation conditions (by assuming a reasonable helium pressure drop of 5% in the additional heater), an additional heating process cannot be an improvement possibility for the Oberhausen II power plant.

Sound propagation through elevated, heated jets in cooler cross-flow: An experimental study.

Sound propagation through hot exhaust plumes with cooler cross-winds is present in many real world systems. One particular example is the sound propagation from exhaust stacks attached to open cycle gas turbine power stations. The research presented in this paper investigates the sound propagation from a reduced-scale exhaust stack, with a cross-flow from experiments conducted in a wind tunnel. Experimental measurements of the flow and temperature fields provide insight into the complex sound radiation characteristics. Results from the acoustic measurements show the change in the sound directivity arising from the inclusion of the hot exhaust plume, leading to non-axisymmetric sound directivity and a concentration of sound downwind of the exhaust stack outlet. In certain cross-flow conditions, the hot exhaust plume can increase the sound observed downwind by up to 11 dB when compared to the scenario of sound propagation from an exhaust stack in the absence of a heated jet or cross-flow. This paper describes the acoustic directivity at various radial distances from the exhaust stack, acoustic frequencies, jet temperatures, and cross-flow free-stream velocity. The results from this paper emphasise the importance of taking into consideration the hot exhaust plume with cooler cross-flow when estimating sound levels downwind of the stack.

Performance improvement of biomass-fueled closed cycle gas turbine via compressor inlet cooling using absorption refrigeration; thermoeconomic analysis and multi-objective optimization

Compressor inlet air cooling is a practical and applied methodology to enhance the conventional open cycle gas turbine power plants. This methodology in this paper, is proposed to be applied on an innovative biomass-fueled Closed Cycle Gas Turbine (CCGT), in which the exhaust gas waste heat is utilized to run an ammonia-water absorption refrigeration cycle for compressor inlet cooling. Thermoeconomic analysis is presented to investigate the two systems (with and without inlet cooling) and multi-objective optimization is conducted to compare their performances at optimal operating conditions. Levelized Cost of Electricity (LCOE) and exergy efficiency are selected as the two rational objectives. The results indicated that, for all the practical range of operating conditions, compressor inlet cooling significantly improves the system performance in terms of both thermodynamics and economics, despite the additional costs imposed on the overall system by adding the absorption refrigeration cycle. It is found that, under the optimal operating conditions, incorporation of compressor inlet cooling results in an improvement of net power and exergy efficiency by 30.1%, meanwhile the LCOE would be reduced by 22.5% when inlet cooling is employed.

Optimization of an Open Cycle Gas Turbine Power Plant Using Exergoeconomics

Optimization of an Open Cycle Gas Turbine Power Plant Using Exergoeconomics

ANALYSIS OF THERMAL EFFICIENCY OF OPEN CYCLE GAS TURBINE POWER PLANT AT PUTRAJAYA (MALAYSIA)

The purpose of this paper is to study the performance of an existing open cycle gas turbine power plant at Putrajaya power station. At compressor inlet temperature of 298.90K, thermal efficiency of 31 % was observed for the existing or current cycle whiles the modified configuration yielded thermal efficiency of 45 %, this result in 14 % increase in thermal efficiency. At pressure ratio of 3.67, thermal efficiency of about 31.06% and 44% was recorded for the current cycle and regenerative cycle respectively. The efficiency of both cycles increase considerably with increase in pressure ratio, but at pressure ratio of about 7, only a small increase in efficiency for both cycles was observed. The optimum value of the efficiencies for both cycles that correspond to pressure ratio of 7 is 43.06 and 56% for the current cycle and the regenerative cycle respectively.

Thermodynamic Evaluation of a 42MW Gas Turbine Power Plant

Energy and exergy analyses were carried out on an active 42MW open cycle gas turbine power plant. Data from the power plant record book were employed in the investigation. The First and Second Laws of Thermodynamics were applied to each component of the gas power plant at ambient air temperature range of 21 - 330C. Results obtained from the analyses show that the energy and exergy efficiencies decrease with increase in ambient air temperature entering the compressor. It was also shown that 66.98% of fuel input and 54.53% of chemical exergy are both lost to the environment as heat from the combustion chamber in the energy and exergy analysis respectively. The energy analysis quantified the efficiency of the plant arising from energy losses , while exergy analysis revealed the magnitude of losses in various components of the plant. Therefore a complete thermodynamic evaluation of gas turbine power plants requires the use of both analytical methods.

Thermo-environmental analysis of an open cycle gas turbine power plant with regression modeling and optimization

In this paper, a gas turbine cycle is modeled to investigate the effects of important operating parameters like compressor inlet temperature (CIT), turbine inlet temperature (TIT) and pressure ratio (PR) on the overall cycle performance and CO2 emissions. Such effects are also investigated on the exergy destruction and exergy efficiency of the cycle components. Furthermore, multiple polynomial regression models are developed to correlate the response variables (performance characteristics) and predictor variables (operating parameters). The operating parameters are then optimized. According to the results, operating parameters have a significant effect on the cycle performance and CO2 emissions. The largest exergy destruction is found in the combustion chamber with lowest exergy efficiency. The regression models have appeared to be a good estimator of the response variables. The optimal operating parameters for maximum performance have been determined as 288 K for CIT, 1600 K for TIT and 23.2 for PR.

Understanding and improving energy conversion systems with the aid of exergy-based methods

Exergy–based methods are powerful tools for developing, evaluating and improving an energy conversion system. Conventional exergy–based analyses have limitations, which are significantly reduced by the so–called advanced analyses. The latter evaluate: (a) the interactions among components of the overall system, and (b) the real potential for improving a system component. The main objective of advanced exergy–based analyses is to provide additional information that is useful improving the design and operation of energy conversion systems. This paper deals with integrated conventional and advanced exergetic, exergoeconomic and exergoenvironmental analyses. The advantages of these analyses are demonstrated using an academic example, an open–cycle gas turbine power system.

Performance optimization for an open-cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling. Part 2: Power and efficiency optimization

The power and efficiency of the open cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling with pressure drop irreversibilities are optimized based on the model established using finite time thermodynamics in Part 1 of this article by adjusting the mass flowrate (or the distribution of pressure losses along the flow path). It is shown that there are optimal air mass flowrates (or the distribution of pressure losses along the flow path) that maximize the net power output, and the maximum has additional maximum with respect to the compressor overall pressure ratio. When optimization is performed with the constraints of the fixed fuel flow and the plant size, the net power output and the thermal conversion efficiency of the cycle can be maximized again by properly allocating the fixed flow area among the compressor inlet and the power turbine outlet. The numerical examples show the effects of design parameters on the power output and heat conversion efficiency. The net power output and the thermal conversion efficiency are improved by using the refrigeration cycle for compressor air inlet cooling.

Performance optimization for an open-cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling. Part 1: Thermodynamic modelling

A thermodynamic model of an open cycle gas turbine power plant with a refrigeration cycle for compressor inlet air cooling with pressure drop irreversibilities is established using finite-time thermodynamics in Part 1 of this article. The flow processes of the working fluid with the pressure drops of the working fluid and the size constraints of the real power plant are modelled. There are 12 flow resistances encountered by the working fluid stream for the cycle model. Three of these, the friction through the blades, vanes of the compressor, and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in the flow cross-section at the mixing chamber inlet and outlet, the compressor inlet and outlet, the combustion chamber inlet and outlet, the heat exchanger inlet and outlet, and the turbine inlet and outlet. These resistances associated with the flow through various cross-sectional areas are derived as functions of the mixing chamber inlet relative pressure drop, and they control the air flowrate and the net power output. The analytical formulae about the power output, efficiency, and other coefficients are derived with the 12 pressure drop losses. The numerical examples show that the dimensionless power output reaches its maximum at the optimal value and that the dimensionless power output and the thermal efficiency reach their maximum values at the optimal values of the compressor fore-stages pressure ratio of the inverse Brayton cycle.

Closure to “Discussion of ‘Some Effects of Pressure Loss on the Open-Cycle Gas-Turbine Power Plant’” (1948, Trans. ASME, 70, pp. 139–141)

Closure to “Discussion of ‘Some Effects of Pressure Loss on the Open-Cycle Gas-Turbine Power Plant’” (1948, Trans. ASME, 70, pp. 139–141)

Closure to “Discussions of ‘Some Effects of Pressure Loss on the Open-Cycle Gas-Turbine Power Plant’” (1947, Trans. ASME, 69, pp. 908–910)

Closure to “Discussions of ‘Some Effects of Pressure Loss on the Open-Cycle Gas-Turbine Power Plant’” (1947, Trans. ASME, 69, pp. 908–910)

Some Effects of Pressure Loss on the Open-Cycle Gas-Turbine Power Plant

Abstract The open-cycle gas turbine has been analyzed in many recent publications, of which some of the more important are listed in the Bibliography (3-7). Most of these analyses, while they utilize probable values of turbine and compressor efficiencies, omit the effects of the pressure drops which occur in the actual components. In the actual gas-turbine plant, the pressure loss which occurs between the compressor and the turbine can seriously affect the performance of the cycle. This pressure loss will be particularly important when bituminous coal is used as the fuel, because of the necessity of interposing ash-removal equipment between the combustor and the turbine. The present study was undertaken in order to determine how much pressure loss can be tolerated in the ash eliminator, and how seriously the cycle efficiency would be affected by the presence of such equipment. The mathematical method outlined in the paper was chosen because a general solution was desired which would be applicable to higher values of turbine temperatures and regenerator effectiveness, when such values can be attained. The results are presented both in tabular form and in a series of graphs. A sample calculation performed with the Keenan and Kaye air tables (1) showed very close agreement with the results obtained by using the equation derived in the paper.