Uma maneira ecologicamente correta de manejar os recursos energéticos disponíveis e reduzir as emissões de gases de efeito estufa é utilizar biocombustíveis ao invés de combustíveis de origem fóssil em motores de combustão interna. Entretanto, o preço mais alto dos biocombustíveis pode ser um fator limitante para o aumento e viabilização do seu uso. Em relação ao etanol, para se obter misturas com mais de 80% de etanol em água o custo de produção cresce exponencialmente. Assim, se misturas de etanol com alto percentual de água, de menor custo, puderem ser utilizadas em motores de combustão interna com sucesso, esse combustível pode se tornar mais atrativo e mais amplamente utilizado. Este trabalho analisa o desempenho de um motor de ignição por centelha operando com etanol em diferentes percentuais de hidratação, através de simulações computacionais e procedimentos experimentais. Foi utilizado um motor monocilíndrico de 0,668L e naturalmente aspirado, com relação de compressão de 19:1 e injeção direta em pré-câmara, ciclo Diesel, foi modificado para operação em ciclo Otto - injeção de combustível no duto de admissão e relação de compressão de 12:1. Testes em dinamômetro foram conduzidos com o etanol hidratado comercial (95% de etanol e 5% de água) e com misturas de etanol e água com maiores percentuais de hidratação (conteúdo volumétrico de até 60% de etanol e 40% de água). Simulação computacional através de software de volumes finitos unidimensional foi utilizada para realizar a análise da combustão. Foi possível alcançar operação estável com misturas de até 40% de água em etanol e ocorreu aumento de eficiência térmica para misturas de até 30% de água. / An environmentally friendly way to manage the available energetic resources and to reduce greenhouse gas emissions is to use bio instead of fossil fuels in internal combustion engines. However, the sometimes higher prices of biofuels can be a limiting factor for their widespread and viable use. Concerning ethanol and its production costs, to obtain above 80% ethanol-in-water mixtures demands an exponentially increasing energy supply. Hence, if a low-cost high water content ethanol could be successfully burned in internal combustion engines it would be even more attractive and extensively used. This work analyzes the performance of a spark ignition engine running with ethanol with different percentages of hydration through numeric and experimental simulations. To achieve this goal, a 0,668L naturally aspirated single cylinder engine, with compression ratio of 19:1 and pre-chamber direct injection, operating at Diesel cycle was modified to operate in Otto cycle - port fuel injection, with a compression ratio of 12:1. Dynamometer tests were carried out with commercial hydrous ethanol (95% ethanol and 5% water) and water-in-ethanol blends with higher hydration levels (volumetric content up to 60% ethanol and 40% water). Computer simulation through one-dimensional finite volume software was carried out to perform a heat release analysis. It was possible to achieve stable operation with up to 40% water-in-ethanol blends and thermal efficiency increase was achieved for blends with up to 30% of water.

A 0.24 degrees C jump of record warm global mean surface temperature (GMST) over the past three consecutive record-breaking years (2014-2016) was highly unusual and largely a consequence of an El Nino that released unusually large amounts of ocean heat from the subsurface layer of the northwestern tropical Pacific. This heat had built up since the 1990s mainly due to greenhouse-gas (GHG) forcing and possible remote oceanic effects. Model simulations and projections suggest that the fundamental cause, and robust predictor of large record-breaking events of GMST in the 21st century, is GHG forcing rather than internal climate variability alone. Such events will increase in frequency, magnitude, and duration, as well as impact, in the future unless GHG forcing is reduced.

Uma maneira ecologicamente correta de manejar os recursos energéticos disponíveis e reduzir as emissões de gases de efeito estufa é utilizar biocombustíveis ao invés de combustíveis de origem fóssil em motores de combustão interna. Entretanto, o preço mais alto dos biocombustíveis pode ser um fator limitante para o aumento e viabilização do seu uso. Em relação ao etanol, para se obter misturas com mais de 80% de etanol em água o custo de produção cresce exponencialmente. Assim, se misturas de etanol com alto percentual de água, de menor custo, puderem ser utilizadas em motores de combustão interna com sucesso, esse combustível pode se tornar mais atrativo e mais amplamente utilizado. Este trabalho analisa o desempenho de um motor de ignição por centelha operando com etanol em diferentes percentuais de hidratação, através de simulações computacionais e procedimentos experimentais. Foi utilizado um motor monocilíndrico de 0,668L e naturalmente aspirado, com relação de compressão de 19:1 e injeção direta em pré-câmara, ciclo Diesel, foi modificado para operação em ciclo Otto - injeção de combustível no duto de admissão e relação de compressão de 12:1. Testes em dinamômetro foram conduzidos com o etanol hidratado comercial (95% de etanol e 5% de água) e com misturas de etanol e água com maiores percentuais de hidratação (conteúdo volumétrico de até 60% de etanol e 40% de água). Simulação computacional através de software de volumes finitos unidimensional foi utilizada para realizar a análise da combustão. Foi possível alcançar operação estável com misturas de até 40% de água em etanol e ocorreu aumento de eficiência térmica para misturas de até 30% de água. / An environmentally friendly way to manage the available energetic resources and to reduce greenhouse gas emissions is to use bio instead of fossil fuels in internal combustion engines. However, the sometimes higher prices of biofuels can be a limiting factor for their widespread and viable use. Concerning ethanol and its production costs, to obtain above 80% ethanol-in-water mixtures demands an exponentially increasing energy supply. Hence, if a low-cost high water content ethanol could be successfully burned in internal combustion engines it would be even more attractive and extensively used. This work analyzes the performance of a spark ignition engine running with ethanol with different percentages of hydration through numeric and experimental simulations. To achieve this goal, a 0,668L naturally aspirated single cylinder engine, with compression ratio of 19:1 and pre-chamber direct injection, operating at Diesel cycle was modified to operate in Otto cycle - port fuel injection, with a compression ratio of 12:1. Dynamometer tests were carried out with commercial hydrous ethanol (95% ethanol and 5% water) and water-in-ethanol blends with higher hydration levels (volumetric content up to 60% ethanol and 40% water). Computer simulation through one-dimensional finite volume software was carried out to perform a heat release analysis. It was possible to achieve stable operation with up to 40% water-in-ethanol blends and thermal efficiency increase was achieved for blends with up to 30% of water.

The utilization of ammonia as a fuel is a pragmatic approach to pave the way towards a low-carbon economy. Ammonia compromises almost 18 % of hydrogen by mass and accepted as one of the hydrogen combustion enablers with existing infrastructure for transportation and storage. From an environmental and sustainability standpoint, ammonia combustion is an attractive energy source with zero carbon dioxide emissions. However, from a practical point of view, the direct combustion of ammonia is not feasible due to the low reactive nature of ammonia. Due to the low combustion intensity, and the higher nitrogen oxide emission, ammonia was not fully investigated and there is still a lack of fundamental knowledge of ammonia combustion. In this thesis, the computational study of ammonia premixed flame characteristics under various hydrogen addition ratios and moderate or intense low oxygen dilution (MILD) conditions were investigated. Particularly, the heat release characteristics and dominant reaction pathways were analyzed. The analysis revealed that the peak of heat release for ammonia flame occurs near burned gas, which raises a question regarding the physics of this. Further analysis identified the dominant reaction pathways and the intermediate species (NH2 and OH), which are mainly produced in the downstream and back diffused to the leading edge and produce some heat in the low-temperature zone. To overcome low reactivity and poor combustion performance of pure ammonia mixture, the onboard ammonia decomposition to hydrogen and nitrogen followed by blending ammonia with hydrogen is a feasible approach to improve ammonia combustion intensity. With increasing hydrogen amount in the mixture, the enhancement of heat release occurs due to both transport and chemical effect of hydrogen. Another approach to mitigate the low reactive nature of ammonia may be eliminated by applying the promising combustion concept known as MILD combustion. The heat release characteristics and flame marker of ammonia turbulent premixed MILD combustion were investigated. The high fidelity numerical simulation was performed to answer fundamental questions of ammonia turbulent premixed combustion characteristics.

As of now, the environmental issue is very topical and there is also an underutilization of different biological material where these can be used in ways that are typically not thought of. One way to increase the degree of utilization is to convert various biomasses such as natural rubber, olive pits, wood chips, and reed pellets into biochar. These biochars can then be added to materials, such as polymers, to improve their reaction-to-fire properties with a low impact on the environment. The process to convert biomasses into biochars, takes place through so-called pyrolysis, i.e., heating under high temperatures and low oxygen concentrations. During pyrolysis, the volatile substances in the biomasses are released and a material is left behind where the compounds that can sustain fire are minimal and a carbon skeleton consisting of strong C-C covalent bonds is prevalent. This biochar then has significantly different material properties compared to its corresponding biomass, where one of the differences is its improved reaction-to-fire properties. This study aims to investigate whether it is possible to determine the final reaction-to-fire properties of different biochars based on the corresponding biomass and its chemical composition. The basis of this study consists of a literature review, laboratory experiments and an analysis. The literature review has been carried out to find the chemical composition of the various biomasses, the laboratory experiments has been carried out to obtain the reaction-to-fire properties of said biomasses and biochars, and the analysis to determine the possibility of predicting the final reaction-to-fire properties of various biochars. The results obtained in this study are that despite the unfavorable reaction-to-fire properties of natural rubber, biochar made from natural rubber had the most desirable reaction-to-fire properties (i.e., fire safe). Of the seven parameters assessed for its reaction-to-fire properties, natural rubber performed worst in five of these compared to the remaining biomasses. However, after conversion to biochar, rubber had the best parameters in three out of five cases where the two additional parameters could not be assessed as these are based on the specimen igniting, which they did not. The parameters in which biochar made from natural rubber obtained the best results were peak heat release rate (PHRR), total heat released per unit area (THRPUA), and maximum average rate of heat emission (MARHE). However, biochar made from natural rubber also obtained the worst results in terms of time to peak heat release rate (TTPHRR) and fire growth rate (FIGRA), where FIGRA is inversely proportional to TTPHRR. Although the lignocellulosic biomasses showed difference in their chemical composition, no major difference in PHRR, THRPUA, and MARHE could be detected between them when their corresponding biochars were tested in the cone calorimeter. The conclusions that can be drawn from this study are that it is possible to predict the final reaction-to-fire properties of the lignocellulosic biochars since they react almost equally when exposed to fire. However, more tests and studies are required to be able to predict the final reaction-to-fire properties of the non-lignocellulosic biochars. This is to understand the chemical compounds and bonds that are formed during pyrolysis, as well as how these affect the biochar’s reaction-to-fire properties.

Experimental measurements of the lift-off velocity and lift-off height, and numerical simulations were conducted on the liftoff and stabilization phenomena of laminar jet diffusion flames of inert-diluted C3H8 and CH4 fuels. Both non-reacting and reacting jets were investigated, including effects of multi-component diffusivities and heat release (buoyancy and gas expansion). The role of Schmidt number for non-reacting jets was investigated, with no conclusive Schmidt number criterion for liftoff previously known in similarity solutions. The cold-flow simulation for He-diluted CH4 fuel does not predict flame liftoff; however, adding heat release reaction leads to the prediction of liftoff, which is consistent with experimental observations. Including reaction was also found to improve liftoff height prediction for C3H8 flames, with the flame base location differing from that in the similarity solution - the intersection of the stoichiometric and iso-velocity contours is not necessary for flame stabilization (and thus lift-off). Possible mechanisms other than that proposed for similarity solution may better help to explain the stabilization and liftoff phenomena. The stretch rate at a wide range of isotherms near the base of the lifted tribrachial flame were also quantitatively plotted and analyzed.

Разработаны алгоритмы расчета температурных полей и оценки термонапряженного состояния массивных железобетонных фундаментов в стадии охлаждения. / Algorithms for calculating temperature fields and assessing the thermally stressed state of massive reinforced concrete foundations in the cooling stage have been developed.

Climate change and its accompanying environmental issues have caused the building industry to use more environmentally friendly building materials. Wood have always been a buildingmaterial but due to the renewed interest in imparting sustainability and renewability, its usage has increased over the recent years. With a rising interest in wood, it is of great importance to enhance the knowledge of its burning behaviour in order to predict and prevent fire hazards. Fire development is often characterized in terms of heat release rate (HRR) as a function oftime. Therefore, HRR is considered one of the most important variables in the evaluation of material fire hazards. This study aims to generate greater knowledge of the HRR curve of wood when exposed to heating in the cone calorimeter and how the curve can be described quantitatively. Furthermore, it was attempted to comprehend the properties and functions of char and its effects on HRR during combustion. The study is based on laboratory tests carried out with a cone calorimeter and a Scanning Electron Microscope (SEM). The cone calorimeter was set to generate a heat flux of 35 kWm-2. Spruce wood samples of three thicknesses were analysed, namely 10, 20 and 30mm. The samples were assembled with one of three types of material on the rear side of the samples, which were Kaowool, steel plates and aluminium foil wrapped around wood. The different materials were used as they are greatly dissimilar in their thermal properties. Wood with both low and normal moisture content was also analysed. Char was analysed with SEM. The results show that there are four major points of interest in the HRR curve of wood. The first point is the initial peak heat release rate (PHRR) that occurs when the sample surface ignites causing great production of heat which increases the HRR. The second point of interest is the vast decrease in HRR soon after the first PHRR, this is due to char formation, which acts as a protective barrier preventing the exchange of volatile gases and oxygen. The third point of interest is a second PHRR close to the end of the combustion that occurs as a response to sample burn through, which means that the heat gradient reaches the rear side of the sample. The second PHRR is highly dependent on the boundary condition defined by the rear material, which determines the heat losses at the rear side of the specimen, and consequently the temperature of the specimen. The higher is the specimen temperature, the higher is the pyrolysis rate, and therefore also the higher the second PHRR. Moreover, high moisture content delays the time of occurrence of the second PHRR as more water needs to undergo phase change, which requires a high amount of energy. The final point of interest is the final decrease in HRR as a result of fuel depletion leading to the sample smouldering or the fire being extinguished. Char, formed by mainly lignin and some cellulose in wood, affects the overall HRR. The SEM analysis showed that the char cracks grew wider during the second PHRR. It is, however, observed that char cracking has no significance in the time of occurrence of the second PHRR as this is based on sample burn through, and it was difficult to determine to what extent char cracking affected the intensity of the PHRR. This systematic study is considered adequate to justify the research questions and aim of this study. It has also created new questions for further study in the area as well as provided a deeper understanding of the fundamental burning behaviour of wood. / Klimatförändringen och dess medföljande miljöfrågor har fått byggbranschen att använda mer hållbara och miljövänliga byggmaterial. Trä har alltid varit ett byggmaterial men på grund av ett förnyat intresse för hållbarhet och förnybarhet har användningen av materialet ökat under de senaste åren. Med ett stigande intresse för trä är det av stor vikt att öka kunskapen om dess förbränningsbeteende för att kunna förutse och förebygga brandrisker. Brandutveckling karakteriseras ofta i termer av värmeavgivningshastighet (HRR) som funktion av tid. Det är därför en av de viktigaste variablerna i utvärderingen av brandrisker. Denna studie syftar till att skapa större kunskap om HRR-kurvan för trä när det utsätts för värme i konkalorimetern och hur kurvan kan beskrivas kvantitativt. Vidare, att studera kollagrets egenskaper och funktioner samt hur det påverkar HRR under förbränning. Studien bygger på laborativa försök utförda med en konkalorimeter och ett svepelektronmikroskop (SEM). Konkalorimetern genererade strålning med intensitet 35 kWm-2. Tre tjocklekar av granprover testades, 10, 20 och 30 mm. Proverna placerades ovanpå en av tre typer av material i en provform, Kaowool, stålplattor och trä invirat i aluminiumfolie. Materialen användes då deras termiska egenskaper skiljer sig åt. Vidare testades även trä av både låg och normal fukthalt. Kollagret analyserades med SEM. Resultatet visar att det finns fyra intressanta områden på HRR-kurvan för trä. Det första är den initiala maximala värmeavgivningshastigheten (PHRR) som inträffar när provytan antänder vilket orsakar en stor värmeproduktion som ökar HRR. Det andra är en kraftig minskning av HRR strax efter den första PHRR. Detta beror på att kol börjat bildas på provytan, kollagret fungerar som en skyddande barriär som förhindrar utbyte av flyktiga gaser och syre. Det tredje är en andra PHRR som inträffar nära brandprovets slut. Detta sker till följd av provkroppsgenombränning som innebär att värmegradienten når provets baksida. Intensitetenav PHRR är starkt beroende av materialet bakom provet. Det bestämmer värmeförlusten på provets baksida och därmed även provkroppens temperatur. Ju högre provkroppstemperaturenär, desto högre är pyrolyshastigheten vilket leder till en högre andra PHRR. Hög fukthalt fördröjer även tidpunkten för uppkomsten av den andra PHRR eftersom fasomvandling av vatten kräver en stor mängd energi. Det sista och fjärde området av intresse är en minskning av HRR efter den andra PHRR, detta sker när allt bränsle förbränts och det som kvarstår är endast ett glödande prov. Kollagret, som främst bildas av lignin och en del cellulosa i träet, påverkar den totala HRR. SEM-analysen visade att sprickorna i kollagret blev bredare under den andra PHRR. Däremot observerades det att sprickbildningen inte har någon betydelse för tidpunkten av den andra PHRR uppkomst då denna enbart är baserad på provets genombränning. Det är även svårt att avgöra i vilken utsträckning sprickbildningen påverkar intensiteten av PHRR. Metoden som används för att besvara frågeställningarna och syftet anses vara adekvat. Studien har öppnat upp för ytterligare frågeställningar och idéer till fortsatta försök inom området. Vidare har även studien gett en djupare förståelse om förbränningsbeteendet av trä.

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In the effort to reduce emission and fuel consumption in industrial gas turbines, lean premixed combustion is utilized but is susceptible to thermoacoustic instabilities. These instabilities occur due to an in-phase relationship between acoustic pressure and unsteady heat release in a combustor. Thermoacoustic instabilities have been shown to cause structural damage and limit operability of combustors. To mitigate these instabilities, a variety of active and passive methods can be employed. The addition of porous inert media (PIM) is a passive mitigation technique that has been shown to be effective at mitigating an instability. Practical industrial application of a mitigation strategy requires early-stage design considerations such as reduced order modeling, which is often used to study a systems' stability response to geometric changes and mitigation approaches. These reduced order models rely on flame transfer functions (FTF) which numerically represent the relationship between heat release and acoustic perturbations. The accurate quantification of heat release is critical in the study of these instabilities and is a necessary component to improve the reduced order model's predictive capability. Heat release quantification presents numerous challenges. Previous work resolving heat release has used optical diagnostics. For perfectly premixed, laminar flames, it has been shown there are proportional relationships between OH* or CH* chemiluminescence to heat release. This is an ideal case; in reality, practical burners produce turbulent and partially premixed flames. Due to the additional straining of the flame caused by turbulence, the heat release is no longer proportional to chemiluminescence quantities. Also, partially premixed systems have spatially varying equivalence ratios and heat release rates, meaning analysis reliant on perfectly premixed assumptions cannot be used and techniques that can handle spatial variations is needed. The objective of this thesis is to incorporate PIM effects into a reduced order model and resolve quantities vital to understand how PIM is mitigating thermoacoustic instabilities in a partially premixed, turbulent combustion environment. The initial work presented in this thesis is the development of a reduced order model for predicting mode shapes and system stability with and without PIM. This was the first time that a reduced order model was developed to study PIM effects on the thermoacoustic response. Model development used a linear FTF and can predict the system frequency and stability response. Through the frequency response, mode shapes can be constructed which show the axial variation in acoustic values, along with node and anti-node locations. Stability trends can be predicted, such as the independent effects of system parameter variation, to determine its stability response. The model was compared to canonical case studies as well as experimental data with reasonable agreement. With PIM addition, it was shown that a combustor would be under stable operation at more flow conditions than without PIM. The work also shows the stability sensitivity to different porous parameters and PIM locations within the combustor. The model has been used to aid in the design of other combustion systems developed at Virginia Tech's Advanced Propulsion and Power Laboratory. To better understand how PIM is affecting the system stability and demonstrate measurements for the improvement of a numerical FTF, experimental work to resolve the spatially varying equivalence ratio fluctuations was conducted in an atmospheric, swirl-stabilized combustor. The experimental studies worked to improve the fundamental understanding of PIM and its mitigation effects through spatially and temporally resolved equivalence ratios during a self-excited instability. The experimental combustor has an optically accessible flame region which allowed for high speed chemiluminescence to be captured during the instability. Equivalence ratio values were calculated from a relation involving OH*/CH* chemiluminescence ratio. The acoustic perturbations were studied to show how the equivalence ratio fluctuations were being generated and coupling with the acoustic waves. The fluctuation in equivalence ratio showed about 65% variation around its mean value during the period of an instability cycle. When porous media was added to the system, the fluctuation in equivalence ratio was mitigated and a reduction in peak frequency (sound pressure level) SPL of 38 dB was observed. Changes in the spatial distribution of equivalence ratio with PIM addition were shown to produce a more stable operation. Effects such as locally richer burning and changes to recirculation zones promoted more stable operation with PIM addition. Testing with forced acoustic input was also conducted to quantify the flame response. The results demonstrated that a flame in a system with PIM responds differently than without PIM, highlighting the need to develop FTF for systems with PIM. This experimental study was the first to study equivalence ratio in a turbulent, partially premixed combustor using PIM as a mitigation technique. A final experimental investigation was conducted to resolve the spatially defined heat release and its fluctuation during a thermoacoustic instability period. This was the first time that heat release had been investigated in a partially premixed, thermoacoustically unstable system, using PIM as a migration method. Heat release was quantified using equivalence ratio, strain rate, OH* intensity, and a correction factor determined from a chemical kinetic solver. The heat release analysis built upon the equivalence ratio study with additional flow field analysis using PIV. The velocity vectors showed prominent corner and central recirculation zones in the no PIM case which have been shown to be feedback mechanisms that support instability formation. With PIM addition, these flow features were reduced and decoupled from the combustor inlet reactants. The velocity results were decomposed using a spectral proper orthogonal decomposition (SPOD) method. The energy breakdown showed how PIM reduced and distributed the energy in the flow structures, creating a more stable flow field. Heat release results with velocity information demonstrated the significant coupling mechanisms in the flow field that were mitigated with the PIM addition. The no PIM case showed high heat release areas being directly influenced by the incoming flow fluctuations. The feedback mechanisms, both mean flow and acoustic, have a direct path to the incoming flow to the combustor. In the PIM case, there is significant mixing and burning taking place in locations where it is less likely that feedback can reach the incoming flow to couple to form an instability. The methodology to quantify heat release provides a framework for quantifying a non-linear FTF with PIM. The development and testing to determine a non-linear FTF with PIM are reserved for future work and discussed in the final chapter. The methodologies and modeling conducted here provided insight and understanding to answer why PIM is effective at mitigating a thermoacoustic instability and how it can be studied using a reduced order numerical tool. / Doctor of Philosophy / In the effort to reduce emission and fuel consumption in industrial gas turbines, lean premixed combustion is utilized but is susceptible to thermoacoustic instabilities. These instabilities occur due to a relationship between acoustic pressure and unsteady heat release in a combustor. Thermoacoustic instabilities have been shown to cause structural damage and limit operability of combustors. To mitigate these instabilities, a variety of active and passive methods can be employed. The addition of porous inert media (PIM) is a passive mitigation technique that has been shown to be effective at mitigating an instability. Implementation of these mitigation strategies require early-stage design considerations such as reduced order modeling, which is often used to study a systems' stability response to geometric changes and mitigation approaches. These reduced order models rely on flame transfer functions (FTF) which numerically model the flame response. The accurate quantification of heat release is critical in the study of these instabilities and is a necessary component to improve the reduced order model's predicative capability. Heat release quantification presents numerous challenges. Previous work resolving heat release has used optical diagnostics with varying levels of success. For perfectly premixed, laminar flames, it has been shown there are proportional relationships between flame light emission and heat release. This is an ideal case; in reality, practical burners produce complex turbulent flames. Due to complex turbulent flame, the heat release is no longer proportional to the flame light emission quantities. Also, partially premixed systems have spatially variant flame quantities, meaning analyses reliant on perfectly premixed assumptions cannot be used and techniques that can handle spatial variations are required. The objective of this thesis is to incorporate PIM effects into a reduced order model and resolve quantities vital to understand how PIM is mitigating thermoacoustic instabilities in a partially premixed, turbulent combustion environment. The initial work presented in this thesis is the development of a reduced order model for predicting mode shapes and system stability with and without PIM. The model uses a simple relationship to model the flame response in an acoustic framework. To improve the model and understanding of PIM mitigation, experimental data such as the local heat release rates and equivalence ratios need to be quantified. An experimental technique was utilized on an optically accessible atmospheric, swirl-stabilized combustor, to resolve the spatially variant equivalence ratio and heat release rates. From these results, better understanding of how PIM is improving the stability in a combustion environment is shown. Quantities such as velocity, acoustic pressure, equivalence ratio, and heat release are all studied and used to explain the improved stability with PIM addition. The methodologies and modeling conducted here provided insight and understanding to answer why PIM is effective at mitigating a thermoacoustic instability and how it can be studied using a reduced order numerical tool. Furthermore, the present work provides a framework for quantifying spatially varying heat release measurements, which can be used to develop FTF for use with thermoacoustic modeling approaches.