This study synthesizes prior research on performance enhancement of single-spool gas turbine systems

efficiency gains, environmental performance, and operational constraints. Despite extensive studies, a critical

gap remains in defining optimal injection parameters under varying operating conditions. This work therefore

proposes a simulation-based framework for optimizing water injection in a 135 MW single-spool gas turbine,

targeting improved thermal efficiency, reduced emissions, and enhanced overall performance.

Key words: Gas turbine; Single spool; Combustion chamber; Direct water injection, etc

The growing escalation of energy needs has forced numerous scientists and researchers to conduct extensive

research in the energy and power production especially in the inventions and optimization of the gas turbines.

Their studies yielded exception al results that form the basis of strength behind the energy industry. This

chapter will explain the works of renowned scholars and technical professionals who have been involved in

Indonesia, to establish the underlying causes of the reduction in power production and the growth of fuel

consumption. They perform necessary checks of the control systems in the plant to measure their operation

and do parametric analysis of the working data to determine the thermodynamic performance of the gas

turbine. It was found that the efficiency of the plants had reduced because compressor blades were clogged

and that other turbine flow channels were blocked and thus could only be completely cleaned by cleaning the

turbine internals. The system was reinstalled but the optimum operating parameters of the plant were not

considered when restoring the system. Moreover, the changes in the air filtration system in the compressor

inlet will be done to reduce the external pollutants that cause blade contamination in the turbine.

Agbadede et al. (2020) conducted a comprehensive experiment of the impact of water injection on the

emissions of nitrogen oxide (NOx) to the combustor of an aero-derivative gas turbine. The focus of their study

model was based on GE LM2500 series which is a widely established type of gas turbines. To evaluate the

effectiveness of water injection, they did various ratios of water/fuels 0.0-0.8 in small steps of 0.2 directly in

the combustion chamber.

As the results of the simulation showed, there was a clear tendency, the higher the water-to-fuel ratio, the less

the severity index of the NOx emissions, which means the successful decrease in the harmful substances. The

lowering was attributed to a lower flame temperature because of the injected water which disrupts the thermal

environment necessary to generate NOx. The paper has observed that the rate of heat and the power output to

the shaft of the turbine increased as the level of water injection increased. This improvement in performance

came at the cost of high fuel consumption and there is a need to balance between pollution control and energy

effectiveness.

The rate of water injection applied in the simulation was 0.5 to 3.0 to assess the level of impact at the different

levels of operation. The results had significant effect on the engine performance even when minor water was

added. The presence of water droplets also led to a higher inlet mass flow rate which enhanced pressure ratios

during the compression as well as the expansion cycle of the turbine. This had an improvement in terms of a

measurable increase in engine performance and thermal efficiency, which was mainly due to the ability of

water to absorb heat and reduce the severity of radiative energy inside the combustion chamber.

Besides, the paper highlighted numerous environmental and operational benefits associated with water

injection. One such conclusion was that a reduction in relative specific fuel consumption, which indicates

improved fuel efficiency at water-assisted conditions. Additionally, the existence of water helped to reduce

temperatures on both the combustor and turbine exits that is fundamental to keeping materials intact and

great importance on the thermofluid mechanics of turbine systems, and they can help in the further

development of the more efficient and less polluting power generation and technology.

Lebele-Alawa et al. (2015) have implemented a transformational engineering project to enhance the

operational performance and energy production of a 25MW gas turbine power plant originally intended to

operate on a single-cycle mode and in a dry state. To address the limitation of this arrangement, in terms of

energy recovery and total efficiency, the researchers redesigned the plant as a combined cycle system with a

steam bottoming cycle. The retrofit was achieved through the installation of Heat Recovery Steam Generator

This strategic change was pegged on the development of a thorough thermodynamic model that was meant to

which is a powerful computational instrument of the engineering study. The simulation generated critical

thermodynamic information which approved the feasibility and effectiveness of the retrofit. This adaptation

led to a significant raise in the power production; 25MW to 37.9MW. This was achieved with no proportional

increase in fuel consumption or other pollutants, indicating the efficiency gains achieved due to the use of

waste heat of the gas turbine to create steam to run an auxiliary steam turbine. The two-turbo system increased

the power conversion and further encouraged a more sustainable and environmentally friendly process of

power production.

The paper was aware that adding additional heat by means of external sources like a duct burner could help

to increase power production, although it was deliberately not included in the scope of the research. The focus

was kept on maximizing performance with the fuel supply and infrastructure that were available, thus

demonstrating the effectiveness of combined cycle retrofitting as a cost-effective and energy-efficient

approach to the upgrading of the existing gas turbine stations.

The computational fluid dynamics (CFD) was used to model and analyze the dynamics of the combustion in

the turbine. The simulation demonstrated that fuels enriched with hydrogen offer great benefit, especially in

reducing the amount of greenhouse gases emitted and in improving combustion efficiency especially of fuels

with a low Lower Heating Value (LHV). However, the researcher has pointed out a major shortcoming in that

The authors examined the effect of humid air and water injection on the stabilization of the combustion

experiment concluded that maintaining mass flow rate of a steam injection up to 125% relative to the flow of

fuel was necessary to maintain a consistent and reliable rate of combustion under such circumstances.

The way ensured that the work of the micro gas turbine system is safe and at the same time improved

efficiency. The study identifies the opportunities of using hydrogen-enriched fuels in conjunction with the

latest humidification technologies to increase the energy and environmental performance of small gas

turbines. They also make their findings to be of great importance in design and optimization of the next-

generation turbine systems that will run effectively on alternative fuels, as well as covering the pressing need

emissions in diesel engines, based on comparing ammonia and water injection processes. They used the

Wartsila 6L 46 commercial marine diesel engine as the focal point of their studies and applied the simulations

determine the effectiveness of ammonia injection as an alternative to water considering its ability to interact

with combustion gases and reduce the emission of NOx.

To isolate and study the mechanism of specific reduction of NOx, the researchers used an artificial inert

species method. In this method, inert substances that resembled the physical characteristics of water, ammonia

and air were used and allowed individual analysis of the chemical, thermal and dilution effects of each

injection process. In this manner, they would better understand the effect of each variable on emission control

in the absence of combustion reactions. This approach was used to explain the different roles that chemical

reactivity, thermal absorption, and gas dilution played in the reduction of NOx.

It was shown that ammonia injection proved to be most effective when introduced in the expansion stroke of

the engine cycle. Chemical reaction between ammonia and combustion byproducts is maximized leading to a

On the other hand, water injection showed an increased reduction in NOx, which was observed at the top dead

center (TDC). Water at this point in the cycle is the main agent in the process of controlling emissions due to

a thermal effect that cools the combustion chamber and the second factor of controlling the emissions is

through the dilution of the gases of the reactants. It is worth noting that, the heating, as well as the diluting

effects of ammonia increase when it is added at TDC, but the overall reduction of NOx is worse than that of

water. Such an analogy highlights the complexity of every fluid and emphasizes the need to tailor the injection

time and approach in terms of the specific features and mechanisms of the used drug.

Xue et al. (2015) conducted a comprehensive research to compare the introduction of the steam in an aircraft

combustor with internal flow characteristics and the formation of nitrogen oxide (NOx) during the use of Jet-

A fuel. In order to achieve this they provided an integrated strategy of combining performance modeling with

computational fluid dynamics (CFD) and chemical reactor network (CRN). Such a mixed technique allowed

modeling complex processes in the combustor and the influence of the steam on the properties of combustion

and the formation of pollutants.

The CFD simulation showed that when the steam is added to the combustion process, the flame temperature

Further studies suggested that in cases where steam is mixed with air at very high levels, the region in which

NOx normally forms is moved to the post-flame region. Such spatial change reduces the NOx emissions

significantly, especially in the condition that the steam mass fraction is elevated. The findings further show

that steam is an inhibitor of NOx by altering the thermal and chemical environment within which the

pollutants are formed. This effect increases with increase in volume of steam, which highlights its feasibility

It is important to note that though steam injection has a major impact on the combustion temperature and

parameters such as thermal efficiency, specific fuel consumption and power output. These characteristics were

modeled and analyzed by the researchers using DWSIM software to be able to model the simple cycle and

advanced versions of the simple cycle, such as those with intercooling, warming and regeneration. This form

of thermodynamic modeling provided a complete system of analyzing the effect of every change on the overall

performance of the system.

The analysis showed that most of the modified cycles had improved thermal efficiency as compared to the

simple traditional cycle. However, not every modification resulted in positive results, in some cases the

thermal efficiency was lower than in the original system. Similarly, the differences in the use of particular

fuel and power generation were observed across different combinations. The differences demonstrate that a

complex relationship exists between design of the cycle and performance outcomes that not all the changes

are beneficial across the board.

trade-offs because some innovations can uplift one aspect of performance and negatively impact another.

A thorough study conducted by Igoma et al., (2016) on the effect of ambient temperature on the performance

environmental temperature and the output of the turbines which has allowed researchers to come up with

important insights on performance patterns when subjected to various thermal conditions.

by 1.17 per cent and the heat rate which is a measure of energy consumption required per unit output fell

substantially by 27.18. The specific fuel consumption rose by 3.57, which is an indication that high

temperatures lead to reduced fuel efficiency. These results highlight how gas turbine systems are vulnerable

to the environment and why temperature-sensitive processes should be used.

The determination found out that the optimal ambient temperature that would reduce the level of fuel

consumption in the Trans-Amadi station was 30degC. This temperature gave the best performance to the

turbine and this implies that there was a thermal sweet spot that can be used in future operational strategies.

The researchers recommended the introduction of inlet air cooling sources, i.e. either misting systems or heat

exchangers, to maintain or to reach this ideal state. Such systems can modify the temperature of incoming air,

of fuel, and enhance the reliability of turbine operations. The study has valuable contributions to the

engineering of thermal power, as it focused on the importance of the environmental variables in the

functionality of an energy system.

Ogbonnaya (2011) enhanced the utility of a gas turbine power plant through a computer based model of the

engine, which was used to optimize performance of a gas turbine. Various data on operation were used to

model the system and eventually simulated. The result shows that the total system efficiency has improved

by 39.2 to 46.25 after the main maintenance. It was established that compressor fouling has a negative impact

on the system, resulting in the reduction of the efficiency. To obtain the best performance of gas turbine, it is

recommended that the operators combine the manual cleaning of the compressor with the offline and online

washing. The air filtration system design is a very important aspect of the gas turbine that determines its

performance based on the quality of air intake.

Aderibigbe et al. (2019) conducted a wide-scale performance evaluation of a 270MW gas power plant, which

included nine units, each with a rating of 30MW. In their study they have focused on two main thermodynamic

indicators which are exergy and heat rate to establish the performance of the plant. They attempted to quantify

the greatest contribution in terms of inefficiencies. This made it possible to make accurate suggestions on how

the system can be improved to make it more effective.

It was found that the major exergy destruction in every unit is in the combustion chamber. The result is

consistent with the nature of the combustion processes, which inherently are highly irreversible due to the

rapid chemical reactions and heat transfer. It was highlighted in the analysis that these losses needed to be

reduced either by improved combustion methods or by design modification to increase thermodynamic

efficiency of the plant. In addition to Exergy analysis, the paper highlighted the necessity of the understanding

of the heat rate, that is, the amount of fuel energy consumed to produce one unit of electrical energy, of the

plant. The researchers used the data of heat rate to correlate with exergy losses to obtain important information

about the performances of individual components. This two-volume approach strategy provided a detailed

view of the plant performance and generated practical recommendations regarding optimization of their

could be necessary to maintain the optimum performance in different operating environments. The study

presents huge information on the analysis of power plant performance. Their analysis offers a detailed

approach to the definition of inefficiencies and the control of gas turbine system improvements by combining

Exergy and heat rate data. The study will contribute to our understanding of thermodynamic behavior in large-

scale power plants and provide some practical implications to engineers and operators who would like to

Omar et al. (2017) conducted an in-depth investigation of how regeneration affects the work of gas turbines

temperature, regeneration efficiency and compression ratio that greatly affect the efficiency of the turbine

cycle.

The results of the simulation showed that application of a regenerator into the gas turbine system had a great

effect on the thermal efficiency and output power. This was enhanced by a reduction of exhaust gas

temperature which indicated an increase in the efficiency of energy retrieval and utilization in the cycle. The

effectiveness of the regenerator and ambient temperature were used to establish the magnitude of these

benefits. The best performance improvements were observed using an exceptionally effective regenerator

with optimal temperature settings, which indicated that optimization, is required in the system. Even though

these advantages are present, the paper has also highlighted the possible drawbacks associated with

regeneration. Of great concern is the fact that the heat recovery process increases the turbine inlet temperature.

When improperly controlled, this high temperature may subject the turbine blades to thermal stress and may

Another risk that was noted in the study is the rise in the emissions of nitrogen oxide (NOx) with high

are also problems related to thermal stress and pollutant emission. They have found the necessity of the

holistic approach to turbines optimization considering both the technical aspect and environmental

sustainability. The research holds much value in the mind of the engineers and decision-makers who are

interested in ensuring that the efficiency of power generation systems is enhanced without compromising the

integrity of operations and being environmentally responsible.

Hanna et al. (2016) carried out a large-scale study to evaluate the performance of a solar chimney power plant

turbine by comparing experimental results to numerical models. The researchers put up a physical testing

At the same time as the physical experiments, the team performed a numerical experiment with the help of

airflow in the turbine was simulated to reflect the overall performance of the system. The authors aimed to

estimate the validity of the theoretical model by trying to simulate internal flow dynamics on the basis of their

predictive power concerning life behavior. The experimental-numerical methodology allowed making a full

comparison and provided better insight into the working nature of the turbine.

The results of the two methods showed a consistent power production of 1.2W to 4.4W. Trend in pressure

drop was observed to increase simultaneously with turbine acceleration though the study had slight variation

before the rotating speed exceeded 1800 rpm. This behavior signaled that there was stability at high speeds.

Moreover, the high level of correlation between the experimental data and the calculations results highlighted

reduces the need to perform significant physical testing. The results obtained by Hanna et al. established that

a combination of both experimental validation and numerical modeling can provide a solid framework of

evaluating and improving the effectiveness of sustainable energy systems.

The use of solar thermal power generation in this study significantly contributes to the field since it offers a

valid means of assessing the work of turbines. It reiterates the importance of the use of ambient-condition-

matched experiments in ensuring realistic and practical results. The findings of the research suggest the greater

use of CFD models in the investigations of renewable energy, specifically in systems when the environmental

variables considerably influence the operational efficiency. There is limited integration of hydrodynamic

optimization and firefighting performance, particularly regarding monitor recoil forces, stability, and station-

keeping requirements (Chuku & Dilosi, 2026).

The findings showed that water injection particularly in turbofan engines could potentially reduce NOx

emissions by a maximum of 80 and still maintaining the fuel efficiency of the aircraft. This large reduction is

attributed to the cooling effect of water which, in turn, lowers the combustion temperatures, and therefore,

adding water to the downstream of the compressor led to lowered fuel efficiency, and therefore a trade-off

that needs ample care during the design and operation of the engine.

injection interventions. In the case of short range missions, typically at less than 3000 kilometers, the extra

weight of extra water is compensated by the performance improvement gains achieved through upstream

of the combustor design of the engine highlighting the need to have custom solutions based on the mission

profiles and engine design.

Conversely, over long range flights (more than 3000 kilometers) the weight disadvantage of water injection

is often counterbalanced by the disadvantage of performance and water injection is a less efficient method of

power addition. The trade-offs are more pronounced, in such cases, and the gains of the reduction of NOx

might not justify the costs of operation. The paper emphasizes the importance of a strategic implementation

of water injection, as it depends on the duration of the missions, engine set up, and the location of injection

to investigate the effects of water injection on nitrogen oxide (NOx) emissions in a twin-shaft aero-derivative

gas turbine combustor. Their analysis was based on a gas turbine which was the design after the GE LM2500

various conditions of operation, and thus, the behaviour of both the design point and the off-design point was

modelled. Such approach has enabled the researchers to test how the engine will respond to water injection

in different operating conditions that creates a comprehensive framework on how to test the effectiveness of

the emission control measures.

The study focused on the direct water injection into the combustor and evaluating its effects at different levels

of water fuel ratios. The researchers could change this ratio to see the changes in NOx production under

incremental changes in water content during combustion. The principle of this method relies on the

thermodynamic principle according to which, before being introduced to the combustion chamber, water

absorbs heat and decreases the temperature of the flame. Since the rate of NOx formation is highly affected

by temperature, it is possible to reduce NOx emissions by lowering the maximum combustion temperature.

Simulation results revealed a clear and consistent pattern: the higher the water to fuel ratio, the higher the

corresponding reduction in the emissions of NOx. This finding shows the effectiveness of water injection as

amount of NOx emissions in the aero-derivative gas turbines through the use of selective water injection.

Sharafoddini et al. (2021) conducted a detailed experiment of the effects of water vapor injection on the fuel

The systematic modeling approach allowed performing a large-scale modeling of combustion dynamics in a

variety of settings. The authors sprayed water vapor into the chamber using different types of fuels and varied

test their simultaneous effects on the thermal profile and the overall performance of the combustor. One of

the main conclusions was the fact that the temperature distribution across the combustion chamber