Volumetric Heat Release Research Articles

Analysis of the thermally stressed state of the heat-generating element in the form of an ellipsoid

The paper considers the thermally stressed state of fuel rods when their geometric shape changes. The temperature fields for the sphere and the ellipsoid are determined. It is shown that, while maintaining volumetric heat release, maximum stresses occur in fuel rods of circular cross-section. Similar results were obtained when changing the geometric shape of a spherical fuel element: all other things being equal, maximum thermal stresses occur in spherical fuel elements.

Ammonia as a Fuel for Gas Turbines: Perspectives and Challenges

The paper addresses the prospects and challenges associated with the use of ammonia in gas turbine plants. The complexity of the chemical kinetic mechanisms of ammonia combustion and the insufficient amount of experimental data that can confirm the results still require a lot of scientific research. In this sense, this application is even less technologically mature than other sectors such as the marine engine one. From the point of view of combustion in gas turbines, the techniques in use and being perfected to deal with flame instability, low laminar burning velocity (about 20% of that of methane-air flames), the long ignition delay time and low volumetric heat release rate. In particular, the use of ammonia blended with other combustion enhancers such as hydrogen, methane and alcohols has been analyzed. Mild combustion is also being analyzed as a valid technique for dealing with the difficulties of ammonia combustion. The combustion of ammonia generates significant quantities of nitrogen oxides, both for the thermal mechanism and for the “fuel” one, which must therefore be mitigated, together with the emission of unburnt ammonia. Even in this case, blending with other fuels allows for improved emissions performance. The paper compares the different techniques and the relative advantages both in terms of combustion efficiency and emissions. Finally, the perspectives for the use of ammonia in gas turbines are outlined, highlighting the challenges still to be overcome, in a panorama of energy transition towards an increasingly decarbonized future, with the aim of mitigating climate change as much as possible.

A Multiple-Burner Approach to Passive Control of Multiple Longitudinal Acoustic Instabilities in Combustors

Abstract Presently, passive methods of controlling combustion instability fall short when one considers stabilizing multiple acoustic modes. In this paper, we present a passive control approach based on the locations of the burners to stabilize multiple acoustic modes. The approach is demonstrated using linear stability analysis performed on a canonical open–open rectangular tube enclosing a flame. A linear flame model based on the kinematic description of the flame surface is used. A simultaneous solution method, as opposed to a segregated method, is developed to calculate the mean flow and to evaluate mode shapes and eigenvalues. The stability analysis is performed both on single and on multiple-burner combustors. In the latter case, the axial and transversal arrangement of burners considered preserves the net volumetric heat release rate and exit temperature. The problem of stabilizing the first three acoustic modes is cast as a multi-objective optimization problem for both types of combustors using the location(s) of the burner(s) as decision variable(s). We show that the use of multiple burners markedly increases the stability of the first three modes while not disturbing the combustor design parameters.

Research on neutron diffusion equation and nuclear thermal coupling method based on gradient updating finite volume method

To solve the problem that the neutron diffusion equation has infinite solutions when the deterministic method is used to calculate the neutron diffusion equation, this paper uses the power calculation equation as a supplementary equation to form a differential and integral equation groups with the neutron diffusion equation, and designs a numerical analysis and machine learning coupling algorithm based on the gradient updating finite volume method that can be used to solve the above differential and integral equation groups. The algorithm decouples the multigroup neutron diffusion equations by source iteration. Then the finite volume method is used to solve the one group neutron diffusion equation and the reactor core power. Based on the power difference calculated by two adjacent iterations, the neutron flux density is updated by the gradient descent method until it converges. Finally, the algorithm can be used to calculate the neutron flux density and volumetric heat release rate of each energy group under the specified power. Taking 5 × 5 rod bundle channel as an example, the feasibility of the algorithm is verified in Fluent 18.0 by writing the UDF script. In addition, the thermal–hydraulic parameters such as temperature and velocity in the reactor can be further calculated according to the volumetric heat release rate, and a same set of grids can also be used to achieve the nuclear thermal coupling calculation. This algorithm can provide a new calculation method for the neutron diffusion equation, and also provide a theoretical basis for the development of application algorithms in the field of reactor physics using deep learning.

MICROWAVE TECHNOLOGY OF LIQUID-GLASS HEAT-INSULATING MATERIALS BASED ON A GRANULAR PRODUCT

The paper investigates the properties of liquid glass thermal insulation products obtained on the basis of granular products under the influence of microwave radiation. Due to the volumetric heat release in the thickness of the liquid glass composition, it is possible to obtain homogeneously structured materials by applying the technology of simultaneous porosization with volumetric expansion of both granules and binder. Thanks to volumetric heating and the mechanism of "non-thermal" effect of microwave radiation on the processing objects, the duration and temperature of their heating is significantly reduced, as well as the operational properties of the products are improved. The properties of materials obtained by this technology are compared with the properties of materials obtained by binding pre-swollen granules. It was proved that the simultaneous swelling of granules with a binder made it possible to obtain materials of a monolithic, uniformly porous structure with high physical and mechanical parameters and an order of magnitude lower indicators of water absorption and sorption moisture due to the dense packing of the granules and the uniform distribution of the binder in the intergranular space. The developed technology for the production of composite materials in the form of heat-insulating products of various configurations by means of simultaneous porosization with volume expansion of granules and binding under the action of microwave radiation allows to obtain materials with a better set of operational characteristics than in the case of binding pre-swollen granules at lower energy costs for their production because it excludes the stage of separate swelling of the granules. The resulting composite thermal insulation materials do not deform and have a fairly high strength for their average density. They are practically incompressible, and this is a very important fact, since the compression of heat insulating materials over time leads to an increase in its thermal conductivity and a decrease in the heat-shielding properties of the structure.

Effect of Co- and Counterswirl Air on Swirl Airblast Atomization

For swirl-stabilized gas turbine combustor, liquid fuel distribution in the near field dictates local equivalence ratio, volumetric heat release, and heat transfer to the chamber wall, and hence its understanding is essential. The effect of inlet air aerodynamics on spray characteristics in a primary zone of a simulated gas turbine burner is studied using a phase Doppler particle analyzer, high-speed Mie scatter imaging, and an orthogonal decomposition method. By employing intense coswirl air, the luminous spray region shifts upstream to the burner exit, where lower mass flux can be observed in the central region and higher mass flux in the outer region of the spray due to the recirculation zone formation. Based on the size velocity joint probability distribution functions (JPDFs) and the individual droplet transport with acquisition time, we conclude that the recirculation zone entraps the smaller droplets and transports them from the downstream to the upstream spray region. Compared to coswirl, counterswirl air exhibits torsion instability, intensifies the concentration of drops in the central region, and improves secondary atomization. Finally, five distribution functions are curve-fitted to the experimental data to capture the atomization process accurately.

Inlet pulsation-induced extinction and plasma-assisted stabilization of premixed swirl flames

• The flame and flow dynamics under air flow pulsations are resolved by performing validated LES and simultaneous OH-PLIF/PIV. • Temporal variations of stretch rate and heat release rate can be used as a criterion for flame extinction/reignition. • A novel decoupled simulation which integrates the plasma source terms and the CFD model is developed. • Thermal and kinetic effects of microsecond repetitively pulsed discharge on combustion are quantitatively interpreted. This paper intensively investigates the inlet pulsation-induced extinction of a premixed swirl flame (PSF) and its plasma-assisted stabilization using the microsecond repetitively pulsed (MRP) discharge. A well-designed low-frequency flow pulsation is applied to the air feedline for the mimicking of transient operations/disturbances in practical engines, which exhibits significant deterioration on the lean blowout (LBO) limit. The MRP discharge is utilized to improve the stability of perturbed flames. It extends the LBO limit at a proper time delay between the air flow pulsation and the discharge, with discharge power less than 1% of the combustion power. Further, the validated large-eddy simulations (LES) and the simultaneous OH planar laser-induced fluorescence/particle imaging velocimetry (OH-PLIF/PIV) measurements are performed to capture the unsteady evolution of flames approaching lean blowout. The nonlinear flame response to the flow pulsation quantitatively reveals the phase difference between the maximum local stretch rates ( κ max ) and volumetric heat release rates ( q ̇ c ). A combined effect of the excessive stretch and the reduction of heat release due to flow pulsation can be used to interpret the flame extinction. Finally, a novel LES-ZDPlasKin combined approach, which decouples the discharge and combustion processes, is dexterously developed to simulate plasma-assisted combustion behaviors. The reignition and stabilization due to the plasma effects are well reproduced in the predictive model, pronouncing the indispensable and synergistic thermal and kinetic effects of the MRP discharge on flame stabilization.

Post-test debris characterisation of molten corium interaction with sacrificial material in a scaled down core catcher

Core catchers are being installed in advanced light water reactors after TMI and Fukushima. The core catchers are designed to stabilise and cool molten corium within the reactor containment for a long time, reducing the risk of core meltdown. Some core catchers use sacrificial material to lower the specific volumetric heat release of the molten corium. The low density oxidic component of molten pool migrate to the top layer of the core catcher after melt-sacrificial material interaction. The high density metallic component migrate to the bottom layer. In the event that the core catcher is top flooded, this prevents metallic components from reacting with water and generate hydrogen. Post experimental analysis of the cooled stratified melt pool was performed. The experimental scaled down core catcher used reactor the prototypic sacrificial material while maintaining the actual reactor flooding conditions. About 550 kg of simulant corium was melted at about 2500 °C using heat of thermite reaction. The core catcher vessel was partially filled with sacrificial bricks. After the test, solidified debris samples from different locations of the core catcher model were analysed for density and SEM-EDS for quantitative and qualitative characterisation. Post-test analysis showed the melt inversion characteristics.

Modeling of Thermal Processes in a Technological System during Electromechanical Processing

The article presents mathematical models of thermal processes of combined methods of electromechanical processing, which are based on the heat conduction equations, which take into account thermophysical properties (thermal diffusivity, heat capacity, thermal conductivity and heat transfer), initial and boundary conditions, technological and other features of the studied processing methods. In view of the fact that electromechanical processing (EMT) is characterized by a process with a volumetric heat release zone, with sufficiently small dimensions and high intensity, it is assumed that the determination of temperature fields can be carried out using the superposition principle. In this case, the main factors affecting the amount of heat propagating into the contacting bodies are the intensity of heat removal, the thermophysical properties of the contacting bodies, and the speed of their relative movement. Dependences are proposed that allow one to describe the temperature fields in the volumes of parts subjected to thermal deformation during electromechanical processing, which have significant geometric parameters that ensure sufficient heat removal from the treated surfaces into the part. It has been established that in the case of processing parts of small dimensions, with insignificant heat removal, it becomes necessary to take into account the accumulation of heat, which will lead to a general increase in temperature in the technological system during processing, and a decrease in the efficiency of the hardening process. The derived mathematical dependencies in the form of heat conduction equations with the established restrictions make it possible to determine the parameters of thermal fields during electromechanical processing in the system “working tool” - “local microvolume of the surface layer”, while these presented mathematical relationships are presented in a linear formulation with thermophysical coefficients. It has been theoretically established and experimentally confirmed that in the process of processing the main factors affecting the amount of heat propagating into the contacting bodies are the intensity of heat removal, the thermophysical properties of the contacting bodies, and the speed of their relative movement. The performed experimental studies have confirmed the adequacy of the mathematical dependencies used to calculate the temperatures in the local microvolumes of the treated surface layer.

Effect of sub-atmospheric pressure on the characteristics of concurrent/upward flame spread over a thin solid

The variation of ambient pressure is a potential tool for studying the driving parameters of fire dynamics and heat release in low-pressure environments such as high-altitude locations, aircraft, and spacecraft. The study of upward flame spread over a solid fuel has direct implications on material flammability and fire development, and low pressure environments have recently gained more attention for the possible comparison with the reduced gravity conditions encountered during space missions. In this work, we consider upward spreading flames over thin acrylic sheets in ambient pressures between 30 and 100 kPa. A forced flow velocity of 20 cm/s is added to the naturally-driven buoyant flow, creating a mixed flow field (natural and forced) that varies with pressure. Flame characteristics such as spread rate and standoff distance are measured from the video analysis of the experiments. It is observed that the former decreases with pressure while the latter increases. The larger flame stand-off distance at low pressures partially explains the decrease of the flame spread rate since the convective heat flux from the flame to the solid decreases. Additionally, volumetric concentrations of the combustion products are measured during the experiments. The results show lower O2 consumption and CO2 production rates at lower pressures. Based on these rates, we could calculate the heat release rate from upward spreading flames at low pressure, providing fundamental information for better understanding pressure-gravity correlations. According to the results, the volumetric heat release rate is proportional to pressure, which is consistent with previous studies on pressure modeling of fires. This suggests that chemical kinetics is not a constraint for the conditions tested in this study, which could help make future flammability tests comparable to low gravity ones.

Non premixed operation strategies for a low emission syngas fuelled reverse flow combustor

In the present study, we investigate the combustion of low-calorific value syngas in a reverse-flow combustor at a fuel thermal input of 3.3 kW. A reverse-flow combustor is known to improve stability while reducing pollutant emissions due to internal recirculation. The study is significant for renewable energy applications of syngas obtained from biomass gasification. Equivalence ratio and O2% in the oxidizer have been varied to establish different modes of operation at atmospheric pressure (P = 1.013 bar). Temperature, heat release, CO, and NOx emissions have been measured to characterize the operation modes. The heat release varies significantly with O2% and influences the CO emissions. The NOx emission is insensitive to the parameters due to the low-calorific value of syngas which limits the maximum temperature to around 1700 K. The lowest CO emission of 32 ppm and NOx < 1 ppm has been achieved in the present study. The combustion efficiency of the combustor is greater than 99%. The variations in pollutant formation were explained using reactor network models. The instantaneous images of heat release revealed key features of the operation modes. As the N2 dilution level is increased, the chemical timescale increases, leading to a volumetric heat release. Suppression of localized heat release reduces the maximum temperature and consequently the NOx emissions.

Generation of skeletal and reduced reaction mechanisms for bio-derived syngas generated from biomass gasification – Experimental and numerical approach

Skeletal and reduced reaction mechanisms replicate the behavior of full reaction mechanism within the band/regime of optimization criteria and provide specific computational advantages for resource-intense multi-physics domain analysis. The current work reports on the development of skeletal and reduced mechanisms for bio-derived Producer gas and Hydrogen-rich Syngas by using GRI Mech 3.0 mechanism. The mechanisms are generated adopting graph-based approach, and timescale analysis are validated for laminar flame speed based on experiments in the equivalence ratios regime of 0.6–1.6 adopting a flame tube apparatus built in-house to mimic a freely propagating double infinity domain premixed reactor. Extending the analysis, the reduced/skeletal mechanisms are numerically validated for ignition delay time, major species profile, and volumetric heat release rate with validity established within the 5% tolerance limit. The current work is a first of its kind to propose optimized mechanism for compositions typical of bio-derived Producer gas and Syngas.

Вариационная формулировка математической модели процесса стационарной теплопроводности с учетом пространственной нелокальности

In creating and using new structurally sensitive materials, it is essential to construct mathematical models which make it possible to describe the materials’ behavior in widely changing external influences. Modeling of non-local media is a class of methods of generalized continuum mechanics. The capability of analyzing mathematical models of a continuous medium can be extended through variational methods. The paper describes the construction of a functional for the problem of stationary heat conduction in a homogeneous body, taking into account the effects of nonlocality and with a temperature-independent heat conduction coefficient. A variational formulation used in the case of a linear problem in combination with acceptable admissible functions allowed us to quantify this effect. The study gives an example of using the variational formulation, which takes into account the influence of the spatial nonlocality of the stationary heat conduction process on the parameters that determine the well-known phenomenon of thermal explosion with an exponential temperature dependence of the volumetric heat release rate in the plate. The quantitative analysis was carried out for two versions of the function that is admissible for the constructed integral functional and describes the possible temperature distribution over the thickness of the plate under consideration. Having compared the obtained results, we opted for the admissible function, as its use leads to a smaller difference between the maximum value of the parameter characterizing the intensity of heat release in the plate and the known result found with no account for the influence of spatial nonlocality

Numerical Analysis of the Characteristics of the Heat Treatment Process of Multilayer Composite Products in Heat Technology Installations

. The results of numerical studies carried out on the basis on a mathematical model developed by the authors of this paper devoted to the investigation of the influence of various factors on the characteristics of the process of heat treatment of composite products in industrial heat technology installations in the presence of internal heat emissions distributed over the volume of individual layers of the product are presented. The formulation of boundary conditions for this model is proposed, considering the multilayer structure of products and the peculiar properties of the organization of their heat treatment process in a heat technology installation. A detailed description of the mathematical model was presented in the previous works. In this study, the functions of temperature distribution and the coefficient (degree) of hydration in the spatial regions that make up the product have been studied as characteristics of the heat treatment process. Model composite products of the same shape and structure but of different volume, consisting of two layers of material in which an exothermic hydration reaction takes place separated by a layer of expanded polystyrene were considered. The temperature-time regime of heat treatment was assumed to be close to that used in industrial conditions in the production of three-layer external wall panels. The boundary and initial conditions corresponded to the conditions of heat treatment on flat stands with water heating and sheltering products from above. It has been determined that the presence of a thermal insulation layer in the core of the product separating the layers that have an internal heat source, changes the distribution of temperature values and the hydration coefficient in the upper and lower layers significantly. An increase in the characteristic volume of the product leads to an increase in the influence of internal volumetric heat release on the processes of heating and hydration, while heat release caused by the course of the hydration reaction begins to have a decisive influence on them.

Theoretical Study of Combustion Processes in Aero Gas Turbines for Air Craft Engines

Combustion process involves various physical and chemical processes which govern and control flames initiation in aero gas turbine engines. During certain flying conditions, at full load, unexpected critical situation may take place in such engines called blow off conditions, which leads to flames diminishing in the combustion chamber of such engines. Gas motion, flow velocity and turbulence kinetic energy are the most important parameters in ensuring flame stabilities. These parameters play a tremendous role and effects on this phenomenon. In gas turbines, the flame exists within a high velocity, non-uniform and intensely turbulent flow field, therefore careful temperature control is vital. Another important factor which must be considered to avoid blow off conditions, is mixture strength. Nearly, all modern gas turbines, due to emissions restrictions, operate on lean mixture conditions which are hard to ignite and lower flame temperatures and thus more risk to reach blow off conditions which leads to a complete flame extinction. These conditions may exist in an air craft engines due to sharp changes in loading parameters, (θL): pressure (Pu), temperature (Tu), mass flow rate (), and cross sectional area (Au). At present there is no detailed theory of gas turbine combustion. Therefore, we must resort to simple models and experimental correlations. This paper investigates the blow-off phenomena in aero gas turbine engines, its causes and estimation of required energy to ensure recovery (re-ignition) again inside the combustion chamber. Identifying the conditions at which blow-off takes place and associated loading parameters (θL) which are a function of (A, T, P, and ). The paper also, quantify the recovery conditions (required energy to re-ignition, change in loading parameter (Δq) Power, Required VHRR: (Volumetric Heat Release Rate) and changes in other loading variables (ρ: density, T: Temperature, P: Pressure, and : mass flow rate) tarts with discussing causes of blow off along with effecting operating conditions.

Lewis number effects on lean premixed combustion characteristics of multi-component fuel blends

Variation in natural gas composition, alongside the potential for H2 enrichment, creates the potential for significant changes to premixed flame behaviour. To strengthen fundamental understanding of lean multi-component alternative fuel blends, an outwardly propagating spherical flame was employed to measure the flame speeds and Markstein lengths of C1C4 hydrocarbons, alongside precisely mixed blends of CH4/C2H6, CH4/C3H8 and CH4/H2. Theoretical relationships between Markstein length and Lewis Number are explored alongside effective Lewis number formulations. Under lean conditions, equal volumetric additions of H2 and C3H8 (30% vol.) to CH4 resulted in similar augmentation of burning velocity, however, opposite susceptibility to preferential diffusional instability was noted. At a fixed equivalence ratio of 0.65, limited changes in composition provide a marked change in the premixed flame response with the addition of C2H6 and C3H8 to CH4. For lean CH4/H2 mixtures, a diffusional based Lewis Number formulation yielded a favourable correlation, whilst a heat-release model resulted in better agreement for lean CH4/C3H8 blends. Modelling work suggests that measured enhancement of lean CH4 flames upon H2 or C3H8 is strongly correlated to changes in volumetric heat release rates and production of H radicals. Furthermore, a systematic analysis of the flame speed enhancement effects (thermal, kinetic, diffusive) of H2 and C3H8 addition to methane was undertaken. Augmented flame propagation of CH4/H2 and CH4/C3H8 was demonstrated to be principally an Arrhenius effect, predominantly through reduction of associated activation energy. Finally, plausible short-term variations in composition with hydrogen-enriched multi-component natural gas flames were investigated experimentally and numerically. At the leanest conditions, small variations in CH4:C3H8 content at a fixed H2 fraction resulted in discernible changes in stretch related behaviour, a reflection of the thermo-diffusive behaviour of each fuel's response.

Effect of environmental conditions on fire combustion regimes in mechanically-ventilated compartments

This publication deals with under-ventilated combustion regimes in case of pool fire in a confined- and mechanically-ventilated enclosure. The objective is to improve the understanding of combustion regimes in a ventilated compartment focusing on the effect of fire size and the ventilation rate. It is based on dodecane pool fire tests conducted on a reduced scale (1.875 m3) enclosure and considering two varying parameters, the pool diameter and the ventilation air flow rate prior to ignition. Three combustion regimes were identified: two steady burning regimes with extinction by lack of fuel or oxygen (fuel burnout) and a transient burning regime with extinction by lack of oxygen. A representation of these regimes is proposed with two scaling parameters: the reference global equivalence ratio, φo, and the volumetric fire heat release rate. Results demonstrate that increasing φo reduces the burning rate in comparison to its value in an open atmosphere. While for a low volumetric fire heat release rate (HRR), the reduction in burning rate is mainly due to oxygen depletion, gas temperature has an additional effect at higher volumetric HRR (about 16 kW/m3). The effect of gas temperature compensates for the effect of oxygen depletion and increases the burning rate. The conditions leading to the highest gas temperature inside the enclosure were obtained in fire scenarios with high volumetric fire HRR and moderate φo.

Laminar flame propagation in nitrogen-diluted stoichiometric H2-N2O mixtures – a numerical study

The paper reports results of the detailed chemical modelling of isobaric deflagrations in stoichiometric H2-N2O-N2 mixtures (N2 = 20 - 60 vol%) at various initial temperatures (300 - 500 K) and various initial pressures (1 - 10 bar): laminar burning velocities, and profiles of temperature, volumetric heat release rate and species concentrations across the flame front. The dependence of the laminar burning velocity on temperature and pressure is examined by empirical power laws, for restricted ranges of pressure (or temperature) variation. For each examined composition, the laminar burning velocity correlates well with the volumetric rate of heat release and with the sum of mass fractions of reactive species in the flame front.

Pengaruh Variasi Arah Aliran Udara pada Stove terhadap Karak-teristik Pembakaran Wood Pellet

This research was conducted to investigate the effect of inlet airflow direction on the combustion characteristics of a wood pellet stove. The direction of the airflow into the wood pellet stove is varied for four methods, namely inlet I, inlet II, inlet III, and inlet IV. At inlets, I, II, and III air is injected into the plenum in the radial direction with the injection points at r = -8, 0, and 8 cm respectively, whereas at inlet IV the direction of airflow into the plenum is in the axial direction with the injection point at r = 0. The combustion characteristics were observed in the wood pellet stove with a continuous fuel feeding system. The combustion characteristics investigated in this research consist of flame visualization, flame temperature, combustion rate, and the efficiency of the wood pellet stove. The results showed that wood pellet stoves with inlet IV had a lower combustion rate and flame height, however, this stove indicates a higher flame temperature and stove efficiency. Air entrance through the inlet IV induces most of the airflow to enter the combustion chamber through the primary channel, compared to that through the secondary and tertiary channels. The primary airflow through the wood pellet encourages a better devolatilization and combustion process. These conditions conduce the flame dimension which is a zone where the combustion reaction occurs is smaller with a higher flame temperature, due to higher volumetric heat release rate. This matter results in better heat transfer from the flame to the test fluid and higher stove efficiency.

Development of extended formulations of the relative concentration of chain carrier method for knock prediction in spark-ignited internal combustion engines fueled with gaseous fuels

This work contributes to improve the understanding of the link between the well-known integral method and the kinetics involved for predicting ignition delay time and knock occurrence crank angle. Extensions of the Relative Concentration of Chain Carriers method, originally developed for predicting ignition delay time under variable thermodynamic conditions of surrogate liquids fuels, were proposed. These extensions are composed of four formulations, which were deduced from the Glassman's kinetic model for predicting knock occurrence crank angle in spark-ignition engines fueled with gaseous fuels. Cases of study of engines fueled with CH4/H2, H2/CO/CO2 and iC8H18/nC7H16 mixtures under Spark Ignition and Homogeneous Charge Compression Ignition mode were considered to assess the performance of the formulations working with hydrogen peroxide (H2O2), formaldehyde (CH2O), hydroperoxyl (HO2) and hydroxyl (OH) as chain carriers. According to the experimental measurements of knock occurrence crank angle for mixtures of CH4/H2, the formulation 1 defined as CC/CCcrit=1, had the best performance working with H2O2 as a chain carrier. Moreover, to understand the role of the so-called chain carrier, a thermal sensitivity analysis, based on the relative contribution of key elementary reactions of the GriMech3.0 chemical kinetic mechanism on the total volumetric heat release rate was carried out. The analysis revealed that the elementary reactions that play an important role in the autoignition of a stoichiometric mixture of CH4/H2/50/50 were the chain propagating reactions R36, R116, and R168, the third body reactions R85 and R33, and finally, the chain branching reaction R119.