Maximum Combustion Temperature Research Articles

Comparative study on combustion and emission characteristics of methanol/gasoline blend fueled DISI engine under different stratified lean burn modes

Combining stratified lean-burn techniques with methanol offers a promising path to achieving high efficiency and low emissions in direct-injection spark-ignition (DISI) engines. This work compares the stratified and homogeneous-stratified lean-burn characteristics of methanol/gasoline fuels on a DISI engine. Combustion and emissions characteristics under two stratified lean-burn strategies were investigated. The results indicate that compared to double-injection stratified lean-burn (DISL), single-injection stratified lean-burn (SISL) leads to more timely combustion, which deteriorates more slowly as the excess air ratio increases. Using M20 fuel with SISL achieves a higher tolerance for air dilution. At the same excess air ratio, SISL results in higher maximum in-cylinder pressure and combustion temperature, but lower exhaust temperature. The economic zone for SISL occurs with M40 fuel at λ = 1.3–1.6, whereas DISL's economic zone is within λ = 1.1–1.3. When λ is below 1.5, SISL produces higher hydrocarbon (HC) emissions but lower nitrogen oxides (NOx) emissions. However, as λ exceeds 1.5, HC emissions from DISL increase sharply while NOx emissions decrease significantly. The particle concentration from SISL is at least an order of magnitude higher than that from DISL, with particle size distribution forming a unimodal curve centered around accumulation mode particles. Conversely, DISL exhibits a quasi-bimodal distribution.

Combustion Characteristics and Performance of Nanoflower Structure AlB2@AP Energetic Composites

ABSTRACT Boron-based solids have garnered significant attention due to their high calorific value. However, during combustion, the formation of boron oxide (B₂O₃) on the surface hinders the interaction between the oxidizing components and the internal active boron (B), thereby limiting its reactivity and combustion efficiency. Modifying boron-based solids represents an effective strategy for overcoming the limitations associated with fuel energy release efficiency. In this study, a shell-structured AlB₂@AP composite was designed and fabricated utilizing etching and recrystallization methods. The structure comprises AlB₂ as the core, B as the middle shell, and AP as the embedded outer shell. The key strategy involves employing an etching process to augment the reactive surface area of boron on the aluminum diboride surface, while also coating it with ammonium perchlorate (AP) to enhance the composite particles. This innovative approach demonstrates that the etching method can effectively utilize the boron present in AlB₂. The composite particles were characterized and analyzed for morphology employing a scanning electron microscope and X-ray techniques. Thermal analysis indicated that the decomposition stage of AP facilitated the oxidation of etched AlB₂, moreover, as the AP coating content increased, the temperature at which vigorous reactions initiated occurred earlier. In combustion experiments, the maximum combustion temperatures of AlB₂@10AP, AlB₂@20AP, and AlB₂@30AP increased by 36.4%, 15.1%, and 3.8%, respectively. The combustion formulation prepared with elemental boron exhibited different characteristics. The average combustion temperatures increased by 33.1%, 23.4%, and 14.4%, respectively. The combustion durations were reduced by 60.8%, 33.7%, and 31.7%, respectively. AlB2@AP is anticipated to further enhance its applications in propellants, explosives, and pyrotechnics.

The effect of cobalt content and mechanical activation on combustion in the Ni + Al + Co system

The effect of mechanical activation (MA) and cobalt content on the combustion velocity and maximum combustion temperature, elongation of samples during synthesis, the size of composite particles of the mixture after MA, phase composition and morphology of combustion products in the Ni + Al + Co system is investigated in this work. Activation of the Ni + Al + xCo mixture allowed the samples to burn at room temperature, with a cobalt content of up to 50 wt. %. An increase in the cobalt content in Ni + Al + xCo mixtures led to a decrease in the size of composite particles after MA, elongation of product samples and the maximum synthesis temperature. After MA, the elongation of the product samples and combustion velocity increased many times, the maximum synthesis temperature increased. With an increase in the cobalt content in the Ni + Al + Co mixture, combustion velocity first increases (at 10% Co), then decreases. Solid solutions based on NiAl and Ni3Al intermetallides were synthesized by the SHS method.

Experimental study of combustion characteristics fuelled with biodiesel/diesel blends in high-pressure common rail electronically controlled diesel engines

Abstract Under the pressure of petroleum shortage and more stringent vehicle emission regulations at present, finding green and renewable alternative fuels has become an important research direction for the internal combustion engine. Due to the increment in oil imports, it is urgent to find a clean alternative fuel that will meet the diesel power and economic performance requirements. Biodiesel, with its renewable characteristics and wide resources, was considered, applied, and promoted extensively. The biodiesel studied in this paper is acidified oil biodiesel. The composition and ratio of acidified oil biodiesel were detected. The physicochemical indexes of acidified oil biodiesel/diesel fuel blends were measured and compared. In the electronically controlled high-pressure common rail diesel engine on different blending ratios of biodiesel/diesel fuel blends for a bench test, we analyze the combustion and characteristics. The results indicate that with the increasing biodiesel proportion, the peak of the premixed combustion and diffusion combustion in the cylinder increase, the combustion start point advances, the combustion duration shortens, and the maximum combustion temperature rises.

Analysis of the Effect of More Fuel and Air Variations Excess Air on Combustion Process Simulation at a 10 kW Biomass Power Plant Using ASPEN PLUS

Abstract The utilization of biomass as an alternative energy can support the achievement of Net Zero Emissions. Each type of biomass fuel can provide different combustion effects from one another. This is due to the different heating values of each fuel. The calorific value is one of the things that affect the combustion performance of the biomass power plant. The main purpose of this study is to examine how different amounts of excess air used during the combustion process affect the outcomes. Combustion is a chemical reaction involving decomposition and gasification that simultaneously occurs in a space where a large amount of energy is released. The modeling and simulation of the decomposition and gasification processes were carried out using Aspen Plus. In this simulator, the decomposition process takes place in the Yields Reactor, while the gasification process occurs in the Gibbs Reactor. The biomass and ash components are characterized by their ultimate, proximate, and sulfur analysis. Then the excess air is varied to analyze its impact on the flame temperature from the reaction. The simulation findings emphasize crucial considerations for achieving complete combustion and reducing harmful gas emissions. Maintaining excess air close to the stoichiometric level ensures maximum combustion temperature at 1616.15 °C while minimizing excess air reduces NOx gas concentration. Approaching stoichiometric air level decreases CO gas and increases CO2, indicating more thorough combustion. However, excess air leads to lower adiabatic flame temperature due to nitrogen formation.

Enhanced combustion performance of Al–Zn alloys with property optimization inspired by “two-way tunneling” strategy

Fluorinated polymers (PVDF) are widely used due to their pre-ignition reaction with Al2O3 to improve the combustion of Al. In this study, a homogeneous PVDF coating layer was constructed on the surface of Al–Zn alloys by solvent evaporation, and Al-Zn@PVDF composites with “two-way tunneling” function during thermal decomposition and combustion were prepared. The constructed PVDF coating layer can react with Al2O3 to destroy the protective layer and promote the oxidation and combustion of Al–Zn from the outside to the inside. At the same time, the energy provided by the Al-Zn@PVDF during the ignition and combustion process also promotes the melting and vaporization of Zn, which achieves the rapid and full combustion of Al–Zn alloy from the inside to outside. The “ two-way tunneling” function of Al-Zn@PVDF composites significantly improves the combustion performance, resulting in a maximum combustion temperature of 1346.9 °C for Al-Zn@PVDF-40 % and a minimum combustion duration of 1.39 s for Al-Zn@PVDF-30 %, which is a significant improvement in combustion performance. The good chemical stability of PVDF also improves the hydrophobicity of Al–Zn and enhances its applicability. In conclusion, the construction of composites with “two-way tunneling” function first proposed in this study can significantly improve the thermal decomposition and combustion properties of Al–Zn, which is expected to further facilitate its application in propellants, explosives and pyrotechnics.

The Effect of Nickel Content and Mechanical Activation on Combustion in the 5Ti + 3Si + <i>х</i>Ni System

Intermetallic alloys were synthesized in the 5Ti + 3Si + xNi system by the method of self-propagating high-temperature synthesis (SHS) and mechanosynthesis. The influence of nickel content on the morphology, size and yield of composite particles after mechanical activation (MA) of mixtures was studied. The dependences of the maximum temperatures and combustion rates, phase composition, morphology and elongation of synthesis products on the nickel content for the initial and MA mixtures are studied. Under the conditions of the experiments conducted in this work, combustion process was able to realize and at the same time the samples burned completely at a nickel content of 10 to 60 wt.% in the 5Ti + 3Si + xNi system. After MA, the samples from the 5Ti + 3Si mixture burned to the end, and during the activation of the 5Ti + 3Si + 40% Ni mixture, mechanochemical synthesis occurred. With increasing nickel content combustion temperature decreases, and combustion velocity behaves nonmonotonically, increases the size of composite particles and decreases the yield of the mixture after MA. MA practically did not affect the maximum combustion temperatures of mixtures of 5Ti + 3Si + xNi. A multiple (from 0.7 to 2.9 cm/s) increase in the burning rate of samples from MA mixtures with an increase in the Ni content from 20 to 30 wt. % was recorded. An increase in the nickel content leads to an increase in the content of triple phases and the amount of melt in the synthesis products of mixtures of 5Ti + 3Si + xNi. Shrinkage of product samples increases with increasing nickel content in the initial mixtures. After MA, the shrinkage of the product samples is replaced by their growth. Explanations of the observed dependencies are proposed.

Combustion and heat release characteristics of micron aluminum with extremely large specific surface area obtained by L-malic acid surface corrosion

Aluminum (Al) particles are widely used in propellants, thermite and pyrotechnics. However, commonly used micro Al has drawbacks such as agglomeration, high ignition temperature and slow burning rate, making its energy potential not fully exploited in applications. Therefore, exploring pathways to enhance the combustion of Al particles has become the focus at present. Herein, L-malic acid (LMA) was used to corrode the surface of Al particles to obtain a sample (named LMAl) with an average specific surface area of 11.456 m2/g (corresponding to Al particles with a diameter of 194 nm). The particle size distribution of LMAl did not change significantly compared to pristine Al. The XPS results showed that a small amount of LMA and corrosion products remained on the surface of the LMAl particles. Thermal analysis tests showed that the thermal oxidation rate and efficiency of LMAl was dramatically higher than that of pristine Al. Compared with the pristine Al, the combustion characterization parameters of LMAl such as combustion intensity, ignition delay time, maximum combustion temperature, mass burning rate and combustion efficiency were all improved. This trend was maintained after blending the ammonium perchlorate (AP). The condensed combustion products (CCPs) of Al revealed a large number of agglomerates and unburned Al particles. While many broken particles and tentacle-like structures were found in the CCPs of LMAl. Overall, compared to Al, the combustion of LMAl is significantly enhanced. The thermal reaction and combustion behaviors of the two are quite different. This study provides new insights into improving the ignition and combustion of Al.

Influences of ultra-low load operation strategies on performance of a 300 MW subcritical bituminous coal boiler

To reveal the operational characteristics of subcritical boilers under ultra-low loads, numerical simulations were conducted based on a 300 MW subcritical bituminous coal boiler. The impacts of boiler load and low-load operation strategies on coal combustion behavior, heat transfer process, and NOx emission were thoroughly examined. Results indicate that acceptable aerodynamic and temperature fields can still be formed at 25 % ultra-low load, but the boiler performance is significantly reduced, with the maximum cross-sectional average combustion temperature being reduced by 225.98 K compared with the full-load condition. At 25 % load, the use of only two layers of burners results in a substantial increase in NOx emission from 290.32 mg/m3 to 445.56 mg/m3. The position of in-service burners affects the region where the intense coal combustion and heat release process occurs, and using the middle three layers of burners helps to maintain heat absorption by the suspended heating surfaces and to minimize NOx emissions. Furthermore, increasing primary air velocity at ultra-low loads can promote coal combustion and heat transfer processes in the lower furnace, but increase NOx emission by 14.23 % when primary air velocity is increased from 14.90 m/s to 23.00 m/s at 25 % load. These findings provide valuable insights for optimizing the ultra-low load operation of subcritical boilers engaged in deep peak-shaving processes under the carbon neutrality goal.

Pengaruh Penambahan Butanol Pada Bahan Bakar Solar Terhadap Karakteristik Pembakaran Single Droplet

Dependence on fossil fuels is one of the most serious threats to the global environment. In addition, petroleum reserves are also decreasing. Meanwhile, the level of oil consumption is always increasing to meet the demand for fuel. Economical and sustainable alternative energy solutions are essential to meet the growing global energy demand without compromising environmental sustainability. One type of alternative fuel that shows very promising potential is biofuel, especially biodiesel. Biodiesel has potential as a more environmentally friendly alternative to diesel fuel, but its low combustion rate and higher viscosity compared to conventional diesel fuel present technical challenges that need to be overcome. The different chemical properties of butanol from biodiesel allow it to have a positive impact on combustion characteristics, such as viscosity, flash point, heating value, and combustion rate. The combustion characteristics that will be studied in this research using single droplet combustion testing include droplet visualization to measure the dimensions of the flame, temperature during the combustion process recorded by a thermocouple, data logger, and video recording during the combustion process to obtain information regarding the ignition delay value. The test steps were repeated five times for each fuel variation and then averaged. In this study, the samples tested included pure diesel, diesel blend with 10% butanol, diesel blend with 20% butanol, diesel blend with 30% butanol, diesel blend with 40% butanol and diesel blend with 50% butanol. From this study, the visualization of the flame is obtained, where the combustion of pure diesel oil droplets has a higher and wider flame, while the flame of the butanol diesel mixture produces a flame whose maximum height is lower than pure diesel oil. The ignition delay time of pure diesel oil is greater than the ignition delay time of the diesel butanol blend. In addition, the maximum combustion temperature produced by each blend is different

Retrofitting Natural Gas–Fired Boiler for Hydrogen Combustion: Operational Performance and NOx Emissions

Abstract The effects of hydrogen fraction (HF: volumetric fraction of H2 in the fuel mixture of CH4 + H2) from 0% to 100% by volume, on the thermal and environmental performance of a 207-MW industrial water tube boiler, are investigated numerically at a fixed excess air factor, λ = 1.15. This study aims to determine the hardware modifications required for boilers to be retrofitted for pure hydrogen operation and investigates how NOx emissions are affected by hydrogen enrichment. The results showed insignificant increases in maximum combustion temperature with increasing the HF, though the distributions of temperature profiles are distinct. In reference to the basic methane combustion, H2 flames resulted in a positive temperature rise in the vicinity of the burner. Increasing the HF from 0% to 2% resulted in higher average thermal NOx emissions at the boiler exit section from 37 up to 1284 ppm, then it decreased to 1136 ppm at HF = 30%, and later it leveled up to 1474 ppm at HF = 100%. The spots for higher differences in NO formation compared to the reference case are shifted downstream at higher HFs. The effect of hydrogen enrichment on CO2 and H2O as radiation sources, as well as the volumetric absorption radiation of the furnace wall and the heat flux at furnace surfaces, has all been presented in relation to the effect of hydrogen addition on boiler performance.

Physical and chemical processes during nitriding of chromium ferrosilicon by filtration combustion

In this paper, the nitriding of chromium ferrosilicon is carried out in the combustion mode under the condition of natural nitrogen filtration. The authors studied the effect of the key parameters (pressure of gaseous nitrogen, diameter and dispersity of starting samples) on the maximum temperature and combustion of the starting powder mixture based on chromium ferrosilicon. The combustion synthesis of chromium ferrosilicon proceeds steadily in the stationary mode with formation of a macrohomogeneous nitrided composition which, according to the results of X-ray phase analysis, contains two nitride phases - chromium nitride and silicon nitride. Interaction of the initial powder with gaseous nitrogen in the filtration combustion mode proceeds by the following probable chemical reaction: 3CrSi2 + 3Si + 3FeSi2 + 11.5N2 = 3CrN + 5Si3N4 + 3Fe. Increasing the diameter of the starting samples slightly affects the amount of absorbed nitrogen and slows the propagation of the combustion wave front. An increase in the pressure of gaseous nitrogen increases the amount of absorbed nitrogen and the combustion rate. Increasing the dispersity of the starting powder increases the amount of absorbed nitrogen and the combustion rate. It was found that the combustion reaction is not possible with a dense initial sample. The maximum combustion temperature, depending on the nitriding conditions, varies between 2400 and 2650 °C and increases with increasing gaseous nitrogen pressure, diameter of the initial samples and dispersion of chromium ferrosilicon powder. It is possible to realise nitriding of chrome ferrosilicon in the combustion mode at the pressure of gaseous nitrogen not less than 3 MPa, diameter of initial samples not less than 3.5 cm and size of initial particles not more than 100 μm. Optimal parameters of nitriding are gaseous nitrogen pressure of 5 MPa, diameter of samples 5 cm, size of initial particles less than 100 μm and bulk density of samples (2.23 g/cm3).

Combustion Characteristics of Coal with Palm Kernel Shells (PKS) Using Thermogravimetric Analysis

Indonesian government is commitment to reduce greenhouse gas emissions, so it is necessary to utilize biomass in power generation as an alternative fuel. This study aims to analyze and evaluate combustion characteristics using TG-DTA (Thermo et al.) with coal, palm kernel shells (PKS), and a mixture of palm kernel shells (PKS) with coal. Sample testing was carried out with four variations of the mixture between PK and coal, namely 10%, 20%, 30%, and 40%, Tests were carried out with nitrogen gas and air with a constant heating rate of 20 °C/min at flow gas of 50 mL/min. Then, the mass reduction is calculated as the heating rate increases up to a temperature of 900 °C. Combustion characteristics can be analyzed by observing the combustion profile graph to obtain derived thermogravimetric data (DTG) to obtain the initiation temperature, temperature burnout, maximum combustion temperature, combustion reactivity, and energy activity of palm kernel shells (PKS), and a mixture of palm kernel shells (PKS) with coal with various composition variations. This research obtained the optimal composition for mixing palm kernel shells (PKS) and coal by TG-DTA.

Preparation and study on combustion performance of AP@ZrH2 core-shell composite energetic materials with high volume energy density

The development of composite energetic material with high volume energy density could increase the range and loading capacity of solid propellants. In this study, a series of core-shell composite energetic materials AP@ZrH2 were fabricated by decorating ZrH2 on the ammonium perchlorate (AP) through a solvent-nonsolvent method. A substantial increase in combustion heat (13373.67 J/g) and maximum burning temperature (1415.33 °C) are detected in composites in contrast to physically mixed sample (10660.46 J/g and 837.22 °C). This is due to the enhancement of the decomposition performance of AP, which provides sufficient oxidation gas atmosphere for combustion of ZrH2. In addition, the delay time (524 ms) and burning time (114 ms) of composites are significantly decreased compared to the physical mixed sample (2145 and 256 ms). The remarkable combustion performance and burning rate could be attributed to reduced mass and heat transfer distances. Finally, the improvement of combustion efficiency in the composites makes the size of the residual particles smaller.

Numerical simulation of the effect of multiple factors on the ignition process of a solid rocket motor

AbstractWith the continuous development of manned space technology, higher requirements have been proposed for solid rocket motors. The ignition process of solid rocket motors affects the reliability, stability and safety of their operation. The ignition powder, cover opening pressure and grain length‐diameter ratio are the main factors affecting the ignition process. Therefore, the influence of different factors on the ignition process of solid rocket motors is studied with numerical simulations. Based on the finite volume method, the ignition process of a solid rocket motor is modelled and experimentally verified. Then, the pressure and temperature distribution characteristics during the ignition delay, flame propagation and gas filling times are analysed. Finally, the effects of different ignition powders, cover opening pressures and length‐diameter ratios on the ignition process are compared and analysed. The results show that the model has high prediction accuracy. When the ignition powder is 6 g, the maximum combustion temperature of solid rocket motor increases from 2590 K to 2620 K between 0.1 ms and 0.44 ms. Between 0.44 ms and 3.18 ms, intermittent flame propagation and pressure oscillations occur. In the gas filling time, the flow field gradually stabilizes. Increasing the ignition powder mass is beneficial to the ignition process, but the disadvantages of pressure oscillations should be considered. Increasing the cover opening pressure enhances the ignition process, while increasing the length‐diameter ratio increases the ignition pressure building time. The study results provide technical support for the structural design of solid rocket motors.

Ignition and combustion characteristics of micro/nano-Al and Al@Ni alloy powders at elevated pressures

Nanosizing and alloying of aluminum (Al) promisingly improve ignition and combustion performance of Al-based propellants. To aim this, lased-induced ignition and combustion characteristics of micro/nano-Al and aluminum@nickel (Al@Ni) alloy powders at elevated pressures (0.1–3.0 MPa) were investigated and the pressure effect on these characteristics was correspondingly evaluated. Comparative results demonstrate that nanosizing and alloying significantly shorten ignition delay and total burn time at elevated pressures, with ignition delay reduction of 98.04% and 52.28% at 1.0 MPa for nano-Al and Al@Ni alloy compared to micro-Al counterpart. Nanosizing and alloying can decrease crucial pressure values (‘mid-pressure extinction domains’) influencing ignition delay, and promote the transfer from the surface to gaseous combustion mode. Maximum combustion temperatures of nano-Al are higher than micro-Al and Al@Ni alloy. During combustion, the combustion of Al@Ni alloy is further intensified due to the microexplosion, while possibly inhibited at higher pressures.

Effect of AP coating or blending on the ignition and combustion of Al particles under a high-pressure water vapour–Ar environment

Overcoming the difficulty of ignition and combustion of aluminium in water vapour is the key to being applied in underwater propellant applications. The effect of coating or blending 20 mass% ammonium perchlorate (namely, AP@Al or AP–Al samples) on the ignition and combustion of Al particles in a 1.0 MPa water vapour–Ar environment was investigated using a constant temperature pressurized combustion chamber and a CO2 laser. The results show that the combustion of Al particles in a water vapour–Ar environment is a non-homogeneous reaction and that agglomeration processes of Al droplets are observed. The ignition and combustion properties of the AP@Al and AP–Al samples under water vapour were greatly improved due to the decomposition of AP for heat/oxygen (particularly, O2 provided a new pathway for AlO(g) generation) supply and the effect of dispersed particles. The maximum pressure change and combustion temperature (Tmax) were increased significantly for the AP@Al and AP–Al samples combustion, while their ignition delay time (ti) and combustion time (tc) decreased remarkably. In addition, the coating form is more effective in the combustion-promoting effect of AP than the blending form. Interestingly, the increase in water vapour concentration is not conducive to the ignition and combustion of samples in this work. It is probably because the reaction system is lean-fuel where the excess water vapour absorbs some of the heat and prevents effective collisions among the radicals. In addition, the chemical equilibrium largely influences the combustion temperature, resulting in a conspicuous effect of changes in water vapour concentration on the Tmax values. The reaction interface largely influences the combustion reaction rate of Al, so changes in particle size have a significant effect on the ti and tc values.

Charcoal analysis for temperature reconstruction with infrared spectroscopy

The duration and maximum combustion temperature of vegetation fires are important fire properties with implications for ecology, hydrology, hazard potential, and many other processes. Directly measuring maximum combustion temperature during vegetation fires is difficult. However, chemical transformations associated with temperature are reflected in the chemical properties of charcoals (a by-product of fire). Therefore, charcoal could be used indirectly to determine the maximum combustion temperature of vegetation fires with application to palaeoecological charcoal records. To evaluate the reliability of charcoal chemistry as an indicator of maximum combustion temperature, we studied the chemical properties of charcoal formed through two laboratory methods at measured temperatures. Using a muffle furnace, we generated charcoal from the woody material of ten different tree and shrub species at seven distinct peak temperatures (from 200°C to 800°C in 100°C increments). Additionally, we simulated more natural combustion conditions by burning woody material and leaves of four tree species in a combustion facility instrumented with thermocouples, including thermocouples inside and outside of tree branches. Charcoal samples generated in these controlled settings were analyzed using Fourier Transform Infrared (FTIR) spectroscopy to characterize their chemical properties. The Modern Analogue Technique (MAT) was employed on FTIR spectra of muffle furnace charcoal to assess the accuracy of inferring maximum pyrolysis temperature. The MAT model temperature matching accuracy improved from 46% for all analogues to 81% when including ±100°C. Furthermore, we used MAT to compare charcoal created in the combustion facility with muffle furnace charcoal. Our findings indicate that the spectra of charcoals generated in a combustion facility can be accurately matched with muffle furnace-created charcoals of similar temperatures using MAT, and the accuracy improved when comparing the maximum pyrolysis temperature from muffle furnace charcoal with the maximum inner temperature of the combustion facility charcoal. This suggests that charcoal produced in a muffle furnace may be representative of the inner maximum temperatures for vegetation fire-produced charcoals.

A comprehensive fluid–solid coupling dynamic simulation for spatiotemporal distribution of regression rate in hybrid rocket motors

The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor (HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination (R2) of 0.9765 and 0.9298, respectively. This research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.

Study on Temperature Field in Common-rail Diesel Engine Combustion Chamber at Different Altitudes

The plateau covers 26% of China’s land area, the higher altitude, the lower atmospheric pressure, the smaller air density, the lower average temperature. Therefore diesel engine power decreases significantly, fuel consumption increases, starting performance deteriorates, and soot emissions increase. In this paper, virtual simulation and simulation test methods are used to study the temperature field change in the combustion chamber of CA6DL2-35E3R common-rail diesel engine at different altitudes and atmospheric pressures. The results show that the altitude has a great influence on the temperature field in the combustion chamber. The maximum combustion temperature gradually increases with increase of altitude, post-combustion is serious and the exhaust temperature increases.