Low Heat Release Research Articles

Flame-Retardant multifunctional epoxy resin with high performances

High-performance and multifunctional epoxy resins (EPs) are of great use in the booming electric & electronic and 5G fields, however their fabrication shows huge challenges. Herein, through a facile strategy by simply incorporating a functional molecule DPI (phosphaphenanthrene polyethylenimine), which possessed a unique structure with hyperbranched polyethyleneimine as flexible inner core and phosphaphenanthrene groups as rigid outer shell, a high-performance and multifunctional epoxy resin was successfully fabricated. The hyperbranched rigid-flexible structure of DPI endowed the resultant thermoset EP-DPI with superb mechanical performance and high glass transition temperature, for which, at a low DPI content (≤4 wt%), EP-DPI exhibited 160%, 40%, and 31% improvement in impact toughness, tensile strength, and flexural strength compared with neat EP. At the same time, the good compatibility between DPI and the EP matrix enabled EP-DPI to be highly transparent, and the aromatic phosphorus structure endowed EP-DPI with excellent UV-shielding effect in the UV-A band. The dielectric performance of EP-DPI was enhanced due to the unique structure of DPI and its interaction with the EP matrix. Furthermore, the phosphaphenanthrene groups endowed EP-DPI with excellent anti-ignition, self-extinguishing, and low heat release during combustion. This work opens up a new strategy for developing novel high-performance and multifunctional EPs with potential versatile applications.

Expanded Polystyrene Beads Coated with Intumescent Flame Retardant Material to Achieve Fire Safety Standards.

The compatibility and coating ratio between flame retardant materials and expanded polystyrene (EPS) foam is a major impediment to achieving satisfactory flame retardant performance. In this study, we prepared a water-based intumescent flame retardant system and methylene diphenyl diisocyanate (MDI)-coated expandable polystyrene microspheres by a simple coating approach. We investigated the compatibility, coating ratio, and fire performance of EPS- and MDI-coated EPS foam using a water-based intumescent flame retardant system. The microscopic study revealed that the water-based intumescent flame retardant materials were successfully incorporated with and without MDI-coated EPS microspheres. The cone calorimeter tests (CCTs) of the MDI-coated EPS containing water-based intumescent flame retardant materials exhibited better flame retardant performance with a lower total heat release (THR) 7.3 MJ/m2, peak heat release rate (PHRR) 57.6 kW/m2, fire growth rate (FIGRA) 2027.067 W/m2.s, and total smoke production (TSP) 0.133 m2. Our results demonstrated that the MDI-coated EPS containing water-based intumescent flame retardant materials achieved flame retarding properties as per fire safety standards.

Effects of Fischer-Tropsch diesel blending in petrochemical diesel on combustion and emissions of a common-rail diesel engine

Fischer-Tropsch (F-T) diesel fuel from indirect coal-to-liquid (CTL) is a promising alternate fuel for diesel engines. To study the effects of F-T diesel/ petrochemical diesel blends on combustion and emission characteristics under various injection timing (IT) and engine loads, the experiment is conducted on a common-rail diesel engine fueled with pure petrochemical diesel (D100), F-T diesel blended in petrochemical diesel by volume of 30% (D70F30) and 60% (D40F60), respectively. Besides, the combustion stability, including cyclic variation and degree of rough work are compared. The results show that F-T blending fuels always have lower heat release rate (HRR) and pressure rise rate (PRR) than D100 during premixed combustion period, while the differences are not obvious during diffusion combustion period. Additionally, two blends have better ignition property and smaller coefficient of variation of peak cylinder pressure (COVpmax). The rough work has no clear difference for all test fuels at medium–high loads, while the engine has remarkably gentle operation with F-T blending fuels at low and partial loads. Although NOx emissions of two blends are only slight reduced, soot emissions are significantly reduced. So the NOx-soot trade-off can be obviously alleviated.

Theoretical Investigation of Combustion and Performance Analysis of Diesel Engine under Low Load Conditions

Diesel engine is using prominently in islands and remote areas due to its reliability and stability for power generation. In recent years, most of the isolated power systems (e.g., islands and remote areas) have integrated renewable energies to reduce both the cost and pollution in diesel power generating system. However, due to intermittent and stochastic behaviour of renewable sources (e.g., solar and wind), it is unable to eliminate diesel generation entirely. In that case, low-load diesel operation (operation < 30% of maximum rated load) is particularly relevant for its ability to support higher levels of renewable penetration. In this paper, a thermodynamic model was developed using MATLAB for diesel engine combustion and performance. This model includes sub models such as heat release rate, heat transfer, double-Wiebe function, and ignition delay correlation. Engine thermal efficiency (TE), brake power (BP), indicated mean effective pressure (IMEP) and brake specific fuel consumption (BSFC) has been taken into consideration for performance analysis. The simulation results show that at 25% load, in-cylinder pressure and temperature are 168 bar and 2300 K which are the cause of lower heat release rate (74 J/deg) and longer ignition delay (0.25 ∼0.5 ms higher than that of conventional mode) and significantly responsible for lower efficiency (18%), brake power (4kW) and higher brake specific fuel consumption (1.2 g/kWh).

Real-Time Temperature Monitoring of Photoinduced Cargo Release inside Living Cells Using Hybrid Capsules Decorated with Gold Nanoparticles and Fluorescent Nanodiamonds.

Real-time temperature monitoring within biological objects is a key fundamental issue for understanding the heating process and performing remote-controlled release of bioactive compounds upon laser irradiation. The lack of accurate thermal control significantly limits the translation of optical laser techniques into nanomedicine. Here, we design and develop hybrid (complex) carriers based on multilayered capsules combined with nanodiamonds (NV centers) as nanothermometers and gold nanoparticles (Au NPs) as nanoheaters to estimate an effective laser-induced temperature rise required for capsule rupture and further release of cargo molecules outside and inside cancerous (B16-F10) cells. We integrate both elements (NV centers and Au NPs) in the capsule structure using two strategies: (i) loading inside the capsule's cavity (CORE) and incorporating them inside the capsule's wall (WALL). Theoretically and experimentally, we show the highest and lowest heat release from capsule samples (CORE or WALL) under laser irradiation depending on the Au NP arrangement within the capsule. Applying NV centers, we measure the local temperature of capsule rupture inside and outside the cells, which is determined to be 128 ± 1.12 °C. Finally, the developed hybrid containers can be used to perform the photoinduced release of cargo molecules with simultaneous real-time temperature monitoring inside the cells.

A new flame‐retardant medium density fiberboard with no formaldehyde release: Wood fiber cell walls template zeolite via in situ thermocompression

AbstractFiberboard which is not flame retardant and releases formaldehyde is widely used in residents' life, which brings serious problems. Now, we use water glass and Al2(SO4)3 to form zeolite precursor, and use UP as adhesive to prepare zeolite‐based flame retardant formaldehyde‐free medium density fiberboard in situ within a few minutes. The molecular sieve structure was characterized by SEM, TEM, BET, and XRD. At the same time, we put forward the possible mechanism of zeolite formation according to the internal temperature and pressure test during fiberboard production. Wood fiber is coated with zeolite, which separates pyrolysis gas from air and avoids further combustion, resulting in low heat release, low smoke and toxic carbon monoxide emission, high residue, and good flame retardant performance. Furthermore, the formaldehyde emission of the formaldehyde‐free flame retardant board is 0.047 mg/L, which proves that it does not contain formaldehyde.

Polymeric fire-extinguishing coatings

Materials Science Although lightweight polymeric foams work well for thermal insulation, they tend to be flammable and do not bond well with most fire-retardant coatings. Drawing inspiration from the adhesion capabilities of snails and tree frogs, Ma et al. designed a polymeric coating based on a copolymer of hydroxyethyl acrylate (HEA) and sodium vinylsulfonate (VS). This waterborne, phase-separated polymer can be sprayed onto foams, where the hydroxyl groups in the HEA lead to strong H-bonding and the sodium sulfonate groups in the VS provide fire retardancy. The coating does not affect the thermal insulation properties of the foam but can self-extinguish a flame with low heat and smoke release because of its tendency to char. ACS Nano 10.1021/acsnano.1c02254 (2021).

Luteolin-based epoxy resin with exceptional heat resistance, mechanical and flame retardant properties

Recently, tremendous attentions have been paid to the fabrication of bio-based intrinsic fire-retarded epoxy resins with outstanding thermal and mechanical properties from renewable resources. Herein, the bio-based epoxy monomer of diglycidyl ether luteolin (DGEL) was synthesized via one-step method from sustainable luteolin. The biocompatible epoxy resin was manufactured via the curing reaction between DGEL and 4, 4′-diaminodiphenyl sulfone (DDS). DGEL/DDS showed higher glass transition temperature (Tg) (314.4 °C) than diglycidyl ether bisphenol A (DGEBA)/DDS (217.4 °C), demonstrating the distinguished heat resistance. Tensile testing results exhibited that DGEL/DDS possessed superior tensile strength (69.2 MPa) compared to DGEBA/DDS (57.2 MPa). Thermogravimetric analysis (TGA) illustrated that the char yield of DGEL/DDS was 44.0 wt%, much higher than that of DGEBA/DDS (11.6 wt%). In addition, DGEL/DDS passed the V-0 rating in UL-94 tests with a high limiting oxygen index (LOI) (32.5%) as well as extremely low peak heat release rate (107.5 W/g) indicating the excellent flame retardant properties. Smoke density testing results showed that the peak density of smoke for DGEL/DDS was 304.7, much lower than that for DGEBA/DDS (660.7), indicating the remarkable reduction of toxicity hazards. This work provides a facile approach for the preparation of bio-based epoxy resins with outstanding overall properties that show promising applications in high heat resistance and flame retardant fields.

Comparative investigation of ignition behavior of butanol isomers using constant volume combustion chamber under diesel-engine like conditions

Butanol is a sustainable carbon–neutral fuel that can be derived from a variety of biomass resources. It can be potentially be used as an alternative fuel to blend with diesel to decrease greenhouse gas and pollutant emissions. In this paper, three butanol isomers (n-butanol, tert-butanol, and iso-butanol) are blended with diesel in various volume ratios. The combustion characteristics of butanol isomers are experimentally determined in a constant volume vessel under engine-like conditions. The effects of blend ratio, chamber temperature, and chamber pressure on ignition delay and combustion process are investigated. It is shown that the ignition delay decreases at high temperature and at low butanol blend ratio regardless of the isomer type. The combustion characteristics of butanol/diesel blends differ from neat butanol. Both low temperature heat release (LTHR) and high temperature heat release (HTHR) are observed for the three butanol isomers/diesel blends. Under current operating conditions, the ignition delay of three butanol isomer/diesel blends is ordered according to iso-butanol > n-butanol > tert-butanol. Notwithstanding its higher octane number, tert-butanol/diesel blends show the fastest LTHR and thereafter the shortest ignition delay. This is because of the absence of H atom on the alpha carbon of tert-butanol, which contributes to consumption of OH radicals. Consequently, oxidation of diesel is less suppressed. However, the HTHR of tert-butanol/diesel blends is much slower than that of n-butanol/diesel. At 80% blend ratio, a higher chamber pressure is required to improve the reactivity and ignition. Overall, the low reactivity of butanol is beneficial to be applied in diesel engines to increase the fuel/air mixing time so as to attenuate soot emissions.

Bioinspired, Highly Adhesive, Nanostructured Polymeric Coatings for Superhydrophobic Fire-Extinguishing Thermal Insulation Foam.

Lightweight polymeric foam is highly attractive as thermal insulation materials for energy-saving buildings but is plagued by its inherent flammability. Fire-retardant coatings are suggested as an effective means to solve this problem. However, most of the existing fire-retardant coatings suffer from poor interfacial adhesion to polymeric foam during use. In nature, snails and tree frogs exhibit strong adhesion to a variety of surfaces by interfacial hydrogen-bonding and mechanical interlocking, respectively. Inspired by their adhesion mechanisms, we herein rationally design fire-retardant polymeric coatings with phase-separated micro/nanostructures via a facile radical copolymerization of hydroxyethyl acrylate (HEA) and sodium vinylsulfonate (VS). The resultant waterborne poly(VS-co-HEA) copolymers exhibit strong interfacial adhesion to rigid polyurethane (PU) foam and other substrates, better than most of the current adhesives because of the combination of interfacial hydrogen-bonding and mechanical interlocking. Besides a superhydrophobic feature, the poly(VS-co-HEA)-coated PU foam can self-extinguish a flame, exhibiting a desired V-0 rating during vertical burning and low heat and smoke release due to its high charring capability, which is superior to its previous counterparts. Moreover, the foam thermal insulation is well-preserved and agrees well with theoretical calculations. This work offers a facile biomimetic strategy for creating advanced adhesive fire-retardant polymeric coatings for many flammable substrates.

Mixing and combustion at low heat release in large eddy simulations of a reacting shear layer

In this paper, the mixing and combustion at low-heat release in a turbulent mixing layer are studied numerically using large eddy simulation. The primary aim of this paper is to successfully replicate the flow physics observed in experiments of low-heat release reacting mixing layers, where a duty cycle of hot structures and cool braid regions was observed. The nature of the imposed inflow condition shows a dramatic influence on the mechanisms governing entrainment, and mixing, in the shear layer. An inflow condition perturbed by Gaussian white noise produces a shear layer which entrains fluid through a nibbling mechanism, which has a marching scalar probability density function where the most probable scalar value varies across the layer, and where the mean-temperature rise is substantially over-predicted. A more sophisticated inflow condition produced by a recycling and rescaling method results in a shear layer which entrains fluid through an engulfment mechanism, which has a non-marching scalar probability density function where a preferred scalar concentration is present across the thickness of the layer, and where the mean-temperature rise is predicted to a good degree of accuracy. The latter simulation type replicates all of the flow physics observed in the experiment. Extensive testing of subgrid-scale models, and simple combustion models, shows that the WALE model coupled with the Steady Laminar Flamelet model produces reliable predictions of mixing layer diffusion flames undergoing with fast chemistry.

Experimental assessment of power generation using a compression ignition engine fueled by farnesane – A renewable diesel from sugarcane

This work reports the experimental study of a single-cylinder compression ignition engine fueled with a renewable diesel from sugarcane called farnesane. The engine is representative of current small-scale power generation in very isolated rural areas existing in Brazil. A complete experimental assessment was made on engine combustion, performance, and pollutant emissions at 1800 rpm under different loads (from 4 to 7 bar IMEP). Results showed reduced values for the ignition delay, in-cylinder peak pressure and mean temperature when using farnesane compared to conventional diesel fuel, as well as lower heat release rate peaks at the premixed combustion phase and shorter diffusion combustion duration. Physicochemical properties differences, such as cetane number, H/C ratio and the biofuel paraffinic structure led to interesting emission behavior. Farnesane reduced NOx emissions by up to 34% (and further 48.6% using EGR), and particulate matter by up to 92%. Despite the higher in-cylinder peak pressure and greater fuel conversion efficiency for diesel fuel at the highest load, the biofuel exhibited gains of up to 3.3% in combustion efficiency and 5.9% in fuel conversion efficiency at intermediate and lower loads. Such improvements are closely related to the HC and CO levels depletion and the absence of aromatic compounds.

High-flame retarding properties of polyacrylonitrile copolymer nanocomposites with synergistic effect of elemental sulfur-doped reduced graphene oxide and bio-derived catechol units

Polyacrylonitrile (PAN)-based flame retardants have been investigated as environmentally friendly high-flame retarding materials. High-flame retarding properties can be achieved in PAN copolymers via efficient thermal oxidative stabilization (TOS). In this study, PAN copolymers of dihydroxy styrene monomers with simple catechol units were synthesized as high-flame retardants using an efficient TOS process. To further improve the flame-retarding properties, PAN copolymer composites were prepared with graphene oxide (GO) and sulfur-doped reduced GO (SrGO). Differential scanning calorimetry (DSC) analysis revealed that the activation energy of the composites for cyclization reaction during TOS decreased with SrGO content. Micro combustion calorimeter revealed enhanced flame-retarding properties of P(AN-co-DHS3)-SrGO composites, resulting in a low heat release capacity (21 J/gK) and high limiting oxygen index (44.7%) (superior to Nomex®). The high-flame retarding properties could be attributed to the high char layer produced by efficient TOS of the copolymer with the catechol unit and radical scavenging effect of sulfur-functionalized SrGO. Therefore, the incorporation of SrGO into PAN copolymers with catechol units is a good alternative for developing environmentally friendly high-flame retardants.

Roles of nanoparticles on freezing process of water within a tank equipped within fins

In this article, solidification of water has been modeled based on Galerkin approach. In this numerical technique, transient phenomena can be simulated with high accuracy because time step is variable factor in this software and mesh can become denser in regions with higher temperature gradient. For verification test, empirical data has been examined and low deviation has been reported. To reach unit with higher efficiency, not only dispersion of nanomaterial but also utilizing extended surface has been suggested in this work. To increase the effective area, wavy wall has been utilized as well as installing the fin with various lengths inside the domain. Concentration of NEPCM is lower than 0.05, so homogeneous model can be utilized for calculating NEPCM features especially thermal conductivity in which shape factor effect has been incorporated. Installing longer fins and utilizing higher shape factor causes required time to reduce because of higher conduction mode. The needed time for m = 3 is 1.09 times greater than case with platelet. At L = 3.5, augment of m leads to change needed time form 315.9 s to 289.54 s. Time declines about 21% with augment of fin length. Also, utilizing loner fins leads to decrease time from 366.57 to 289.54 s when m = 5.7. The lowest performance among scrutinized cases is belongs to case with m = 3, L = 7. As time increases, the volume of liquid phase decrease which offers lower heat release and temperature drop. Outputs depicts that impact of L of profiles is more effective than that of m. With growth of solid fraction, temperature declines. Also, with augment of L and m, energy declines while solid fraction increases.

Investigation of Reverse Flow Slinger Combustor With Jet A-1 and Methanol

Abstract This paper describes an experimental investigation of the reverse flow slinger (RFS) combustor that has been developed in order to attain high flame stability and low emissions in gas turbine (GT) engines. The combustor employs centrifugal fuel injection through a rotary atomizer and performs flame stabilization at the stagnation zone generated by reverse flow configuration. The design facilitates entrainment of hot product gases and internal preheating of inlet air, which enhances flame stability and permits stable lean operation for low NOx. Moreover, a rotary atomizer eliminates the need for high injection pressures, resulting in a compact and lightweight design. Atmospheric pressure combustion was performed with liquid fuels, Jet A-1 and methanol, at ultralean fuel–air ratios (FARs) with thermal intensity varying from 30 to 52 MW/m3 atm. Combustor performance was evaluated by analyzing the lean blowout, emissions, and combustion efficiency. A very low lean blowout corresponding to global equivalence ratio of 0.1 was observed, which showed the combustor's high flame stability. Sustained and stable combustion at low heat release was attained, and NOx emissions as low as 0.4 g/kg and 0.1 g/kg were achieved with Jet A-1 and methanol, respectively. Combustion efficiency of around 55% and 90% was obtained in operation with Jet A-1 and methanol. The overall combustor performance was significantly better with methanol in terms of emissions and efficiency.

A desoxyanisoin- and furfurylamine-derived high-performance benzoxazine thermoset with high glass transition temperature and excellent anti-flammability

Highlights Poly(BHDB-Bz) exhibited a relatively high glass transition temperature (285 oC) Poly(BHDB-Bz) displayed a high LOI value (40.0%) and a UL-94 V-0 rating owing to its superior charring ability Poly(BHDB-Bz) showed an extremely low HRC (35.5 J/(g•K)) which is lower than most synthetic polymers Despite many superior advantages including high heat resistance, low dielectric constant, low water absorption, and low curing shrinkage, the flammability of polybenzoxazines restricts their widespread applications in electronic realms. It is thereby essential to synthesize flame retardant polybenzoxazines for broadening their applications. In this work, we synthesized an anti-flammable bio-based benzoxazine monomer (BHDB-Bz) derived from furfurylamine. As a control sample, another bio-based benzoxazine monomer (BPA-Bz) was also synthesized from furfurylamine and bisphenol A. The molecular structure of BHDB-Bz and BPA-Bz was confirmed by FTIR, and 1H- and 13C-NMR spectra. Two kinds of bio-based polybenzoxazines, poly(BHDB-Bz) and poly(BPA-Bz), were obtained through thermally-induced ring-opening polymerization. Poly(BHDB-Bz) exhibited a relatively high glass transition temperature (285 °C), a high initial decomposition temperature (379 °C under nitrogen and 388 °C under air), and an extremely high char yield under nitrogen (65.9%), all of which were better than poly(BPA-Bz). Benefitting from the superior charring ability of desoxyanisoin structure, poly(BHDB-Bz) exhibited outstanding anti-flammability, whereas poly(BPA-Bz) was flammable. Specifically, poly(BHDB-Bz) displayed a high LOI value (40.0%), a UL-94 V-0 rating, and an extremely low heat release capacity (35.5 J/(g•K)). This work provides a facile and sustainable strategy for developing an anti-flammable benzoxazine thermoset without introducing flame retardant additives.

Poly(vinylalcohol)/chitosan-based high-strength, fire-retardant and smoke-suppressant composite aerogels incorporating aluminum species via freeze drying

In this work, new types of organic-inorganic composite aerogels were fabricated via the freeze-drying method based on the chemical interaction between bio-based chitosan and aluminum chloride, in combination with physical cross-linking among chitosan, inexpensive polyvinyl alcohol (PVA) and alumina sols derived from the acidic hydrolysis of aluminum isopropoxide (AIP). The microstructural evolution of the freeze-dried chitosan-aluminum/PVA (CAP) aerogels revealed that varied amount of aluminum salt could influence the three-dimensional architecture. Especially, the CA1.5P aerogel with herringbone-like structure had high compressive strength of 8.55 MPa, corresponding to the specific modulus of 66.3 m2 s−2. Compared to the polymeric chitosan/PVA aerogel, the CAP aerogels showed better fire retardancy, as confirmed by limited oxygen index (LOI) tests and cone calorimeter (CC) tests. Remarkably, the introduction of inorganic components from AIP (about 7.7–20.1 wt%) led to an increased LOI value (35%–41.1%) and lower total heat release and total smoke release. The proposed mechanism suggested that the enhanced flame retardancy benefitted greatly from the formation of alumina-rich hybrid chars with the assistance of thermal degradation of chitosan, which resulted in barrier effects of controlling the heat and smoke hazards. In addition, silanization modification of the composite aerogel was performed by a facile chemical vapor deposition (CVD) treatment to improve the hydrophobicity. The aluminum-incorporated organic-inorganic aerogels with high mechanical strength, good fire-resistance and smoke-suppressant performance could be seen as potential alternatives to traditional flame-retardant foams.

Large eddy simulation on flame topologies and the blow-off characteristics of ammonia/air flame in a model gas turbine combustor

Ammonia (NH3) is recently identified as one of the suitable energy carriers in hydrogen energy system. However, regarding NH3 as a fuel is still facing several challenges which limit the direct use on modern combustion systems. The main challenge is the difficulty to stabilize NH3/air flames. To reveal and analyze the stabilization mechanism and the characteristics during blow-off processes in a swirl combustor, large eddy simulation with thickened flame model was performed to resolve the three dimensional swirl NH3/air flame. The CH4/air flame was also performed for comparison. The reacting flow fields and the flame structures were measured by PIV and OH-PLIF technique respectively. For NH3/air flame, flame fronts are burning to the higher equivalence ratio region, which leads to a larger trend of extinguishing. The curvature distribution at flame root is mainly dependent on the flame characteristics. Downstream the flows, the curvature distribution is mainly influenced by the flow field characteristics. Though the value of wall heat loss of NH3/air flame is less than that of CH4/air flame, the heat loss still shows greater influence on NH3/air flame stabilization when considering the lower heat release rate of NH3/air flame. The blow-off of CH4/air flame is mainly caused by the decreasing HRR and heat loss, while for NH3/air flame, it is a combined effect of the excessive stretch, the reduction of HRR as well as the greater heat loss effect.

Phosphorus-Free Vanillin-Derived Intrinsically Flame-Retardant Epoxy Thermoset with Extremely Low Heat Release Rate and Smoke Emission

Recently, the development of bio-based intrinsically flame-retardant epoxy thermosets has attracted increasing interest for the replacement of petroleum-based epoxy thermosets in fields that demand...

Potential of Semi-Empirical Heat Transfer Models in Predicting the Effects of Equivalence Ratio on Low Temperature Reaction and High Temperature Reaction Heat Release of an HCCI Engine

In this paper, the influence of equivalence ratio on the low-temperature reaction heat release (LTR-HR) and high-temperature reaction heat release (HTR-HR) of homogeneous charge compression ignition engine has been experimentally and numerically examined. The numerical study was performed using zero-dimensional (0D) single-zone model by considering the chemical kinetic of fuel combustion. Annand, Woschni, Hohenberg, Chang (Assanis), and Hensel semi-empirical heat transfer models were employed in the 0D single-zone simulations. In this study, the in-cylinder pressure, rate of heat release, LTR-HR and HTR-HR were investigated. The Hensel heat transfer model was the only model that predicted the combustion in all of the operating conditions. The Hohenberg model properly recognized the effects of equivalence ratio changes on the HTR-HR.