Injection Position Research Articles

Ultrasound-Guided Off-Plan Lumbar Seated Erector Spinae Plane Blocks : Are There Advantages?

The erector spinae plane block (ESPB) has been widely used as a treatment strategy for a variety of acute and chronic painful conditions. ESPBs are typically performed under ultrasound guidance [USG] in an in-plane long axis approach, targeting the tip of the lumbar transverse process while the patient lies prone. Off-Plane Seated Injection Technique-ESPB [OPSIT-E] represents a useful alternative in situations where a standard prone spine injection would be technically challenged by circumstances which may include morbid obesity, orthopnoea, recent upper limbs surgeries, chest pain from recent pacemaker implant, and in a subjects were in-plane approaches may be complicated by skin lesions. A seated forward flexed off-plane injection position, may also flatten the lumbar lordosis, shift adipose tissue more anteriorly, lessening skin to target distance and facilitating bony landmark identification, in high BMI and hyperlordotic subjects. The relatively larger curved transverse arc radius of the curvilinear probe [GE G1-5] in comparison to its transverse arc, also appears to offer improved central field of skin-transducer contact, earlier needle visualization, improved acute angle trajectory visualization of deep structures, which may be due to less crepuscular beam dispersion in comparison to transverse probe orientation. Even with a linear probe, the orthogonal technique facilitates a more perpendicular vector, lessening needle transit to target distance, which may in turn decrease procedure time, and improve patient comfort. The OPSITE, may also be easier to teach, learn, and master, as other studies have generally reported a higher rate of off-lane injection success among novice vascular interventionists.

Paradigm for Determining the Optimal Ultradeep and Super‐thick Saline Aquifer for High‐TDS Mine Water Geological Storage

AbstractSaline aquifers are the most popular waste and CO2 injection and storage reservoirs worldwide. This project proposes that several optimal injection positions should be investigated as hydraulic pressure‐focused positions, in order to relieve the high demands of pump performance. The comprehensive indices (Fi) representing the injectivity of different burial depths were obtained by using information entropy, based on the mercury injection experimental data of 13 rock samples. The results demonstrated that the burial depths of No. 4, No. 1 and No. 2 in the Liujiagou Formation were the most suitable positions for hydraulic focused injection, which means the upper 30 m thickness could be regarded as the hydraulic focused range in the saline aquifer with an average thickness of 400 m. In addition, some laboratory experiments and in situ tests were carried out for the purpose of certifying and analyzing results, including SEM, XRD, brittleness index and logging. The results suggested that the rock samples at the No. 4, No. 1 and No. 2 burial depth ranges have loose microstructure, weak cementation, as well as dual pores and fractures. The lithology is mainly quartz and feldspar, but the clay mineral content is high (10%–25%), which is positive for dissolution. The lithology is suitable for hydraulic fracturing to form extended cracks and micro‐fissures during high‐TDS (total dissolved solids) mine water injection, because of the high brittleness index. Finally, a theoretical and technical framework for high‐TDS mine water injection was established, based on operating pilot engineering. Some theoretical defects and drawbacks learned from the field practices were summarized and solutions proposed. The research in this study could provide guidance and a paradigm for the inexpensive treatment of high‐TDS mine water by injection and storage.

Investigation on mixing characteristics of rotating detonation combustor with convergent inlet

Mixing characteristics play an important role on the operational process of rotating detonation combustor (RDC). In this paper, a series of numerical calculations were conducted to analyze the influence of injection diameter, injection position, reactant mass flow rate, and equivalence ratio on mixing characteristics. Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed in detail. The findings indicated that all four injection conditions had significant influence on mixing characteristics, among which injection position was the most significant factor. When injection position was in convergent section, the mixing characteristics were better than those in ignition section. Reducing the fuel diameter gradually improved mixing characteristics, but also increased total pressure loss. The change of reactant mass flow rate had a minimal effect on mixing characteristics. As equivalence ratio decreased, mixing characteristics decreased and total pressure loss decreased. In addition, the comparative analysis also showed that penetration depth of hydrogen had an impact on flow field disturbance and distribution of return region, which led to the difference in mixing characteristics. When hydrogen was injected into the convergent structure section where air flow velocity did not reach sonic speed and was in acceleration phase, total pressure loss would be effectively reduced in combustor dome.

Optimization of pellet design parameters to achieve deep fueling depth in EAST plasma with PAM code

Deep pellet fueling depth is necessary to achieve a high-density high confinement operation and to conduct some pellet-related researches in current devices, such as trigger of internal transport barrier, and to achieve high fusion power and tritium burn-up fraction in future fusion devices. The newly developed PAM code which can make a fast evaluation on pellet ablation and deposition is applied to optimize injection parameters to achieve deep pellet fueling. Systematic scans on pellet injection parameters including pellet injection positions, injection angles, sizes and speeds are performed for optimization purpose, while at the same time demonstrating flexibility and time efficiency of the PAM code. Dependences of the pellet fueling depth on these injection parameters are revealed by simulation results and analyzed. Simulation results indicate that pellet penetration contributes more to the deep pellet deposition than the ∇B -induced plasmoid drifts in low temperature plasmas, while deep pellet fueling in reactor relevant high temperature plasmas has to rely on plasmoid drifts. Though a shallow penetration is expected in high temperature plasmas, the ∇B -induced plasmoid drift is expected to be larger than that in relatively low temperature plasmas.

Parametric Study of Flow and Combustion Characteristic in a Cavitied Scramjet with Multi-Position Injection

This study focuses on the three-dimensional flow and combustion characteristics of a cavitied scramjet engine with multi-position injection. A single-equation large eddy simulation (LES) turbulence model is employed, with a detailed reaction mechanism for hydrogen combustion, as described by Jachimowski. The combustion characteristics of hydrogen in the scramjet combustion chamber are analyzed. Based on the combustion chamber model, the influence of different equivalence ratios, injection timing, injection positions, and injection pressures on the flame formation and propagation process are compared. The results indicate that within a certain range, an increase in the equivalence ratio enhances the combustion intensity and chamber pressure. In the case of multi-position injection, the order of injection from different nozzles has little effect on the final flame stabilization mode and pressure distribution. The opposite-side distribution of nozzles can effectively improve the fuel efficiency and the internal pressure. Furthermore, when the nozzles are closely placed in the opposite-side distribution, the combustion efficiency increases, although this leads to a higher total pressure loss. In scenarios where the fuel injection duration is short, an increase in the injection pressure at the upstream nozzles of the cavity results in a higher local equivalence ratio, as well as reduced fuel mixing and ignition time.

Migration and cooling characteristics of low-temperature gaseous CO2 in high-temperature loose coal

To investigate the extinguishing effect of low-temperature gaseous CO2 on coal spontaneous combustion, a similar simulation experiment was designed and conducted to test its migration and cooling characteristics in high-temperature loose coal. During the injection of low-temperature gaseous CO2, the temperature along the central axis of the release port decreases rapidly. The size of the cooling range and the diffusion rate of the cooling area are inversely proportional to the distance from the center axis and directly proportional to the injection time. The injection time plays a dominant role in the cooling effect of the high temperature coal, followed by the injection position. Gaseous CO2 diffuses inside the loose coal body rapidly, filling the vicinity of the release port within 5s and the container within 30s. The average diffusion velocity of CO2 within the loose coal is 0.051 m/s. The results of this study provide a theoretical basis for the application of low-temperature carbon dioxide to combat coal fire disasters.

Dynamic coupling effects of injection on spray and mixture formation in an asymmetrically vibrating combustion engine

Enhanced methods of energy conversion present a viable solution for addressing energy load challenges. This study introduces a vibrating combustion engine designed to enhance energy conversion efficiency by harnessing flexible dynamics and variable asymmetric motion. However, the consideration of its unique dynamic effects has emerged as a pivotal challenge in fuel-air mixing and combustion research. This study introduces a fuel spray and mixing simulation method that facilitates the reciprocal exchange of coupling parameters between the combustion and dynamics models. It iterates the simulation outcomes of motion and combustion to predict mixture formation. Subsequently, the method is employed to explore the impact of injection position on fuel spray and mixture formation. Results show that there is an optimum injection position for the operation frequency, and retarding or advancing leads to slow compression and weak gas motion for fuel spray and mixing, although retarded injection provides high in-cylinder gas pressure and temperature. The early injection generally causes long penetration, small droplet diameter, slight impingement, and fast evaporation, unless it is too early. The results further indicate that when IAP = 6 mm, a more uniform mixture can be attained at the beginning of combustion, leading to a thermal efficiency of up to 42.9% for the engine.

Systematic numerical analysis of ECCD exploring injection conditions with high CD efficiency and current profile controllability in JA DEMO

Systematic Electron Cyclotron Current Drive (ECCD) simulations were performed in JA DEMO plasma (Te=34keV and ne=1.0×1020m−3 at the center) for various injection conditions of EC waves, including wave frequency, injection direction and injection position. Different injection positions surrounding the plasma are comprehensively scanned, including midplane and upper launch on the high/low field side (HFS/LFS) of the plasma. Numerical results indicated that higher harmonic absorptions deteriorate the ECCD efficiency regardless of injection positions. High ECCD efficiencies for each injection position were obtained when avoiding higher harmonic absorptions. The maximum ECCD efficiency of 46kA/MW was obtained for upper LFS launch with an optimal frequency and direction. An important finding from the systematic analysis is that such an efficient ECCD exceeding 40kA/MW is expected for a wide range of injection positions of upper and midplane LFS launch. This result is favorable for fusion reactor design, indicating flexibility in EC port arrangement for efficient ECCD. Current profile controllability in JA DEMO was also discussed in two injection cases: the upper LFS launch and the conventional midplane LFS launch. Driven current density profiles with various injection angles from each injection position successfully cover the regions from the center to mid-radius of the plasma, where external current drive is required to achieve a weak reversed shear. Furthermore, sufficient ECCD efficiencies of 35–46kA/MW at the upper LFS launch and of 35–43kA/MW at the midplane LFS launch are obtained.

Hydrogen Injection Position Impact: Experimental Analysis of Central Direct Injection and Side Direct Injection in Engines

<div>A detailed investigation was carried out on the performance, combustion, and emissions of a single-cylinder direct injection hydrogen spark ignition (SI) engine with either a side-mounted direct injection (SDI) or a centrally installed direct injection (CDI) injector.</div> <div>The first part of the study analyzed the performance and emissions characteristics of CDI and SDI engine operations with different injection timings and pressures. This was followed by comparing the engine’s performance and emissions of the CDI and SDI operations at different engine speeds and relative air-to-fuel ratios (lambda) with the optimized injection pressure and timings. Furthermore, the performance and emission attributes of the hydrogen engine with the CDI and SDI setups were conducted at a fixed λ value of 2.75 across a broad spectrum of engine loads.</div> <div>The study’s main outcome demonstrates that both direct injection systems produced near-zero CO<sub>2</sub>, CO, and HC emissions. Stable engine operations could be achieved over a wide range of air-to-fuel ratios by the CDI and SDI setups, though the CDI enabled a wider range from stoichiometric to lambda = 3.8. The CDI system also offered noticeably higher thermal efficiencies than the SDI engine. The study also illustrated the sensitivity of each injection system to the variation of the injection pressure and timing and identified the optimum operation settings for each system. Finally, the study indicates that the emissions characteristics of CDI and SDI are similar at low and mid-load, although SDI resulted in both higher NOx and hydrogen emissions than CDI.</div>

Experimental study on suppressing thermal runaway propagation of lithium-ion battery modules by using liquid nitrogen: Influence of injection pipe diameter and position

This paper aims to address the safety threats posed by thermal runaway (TR) in lithium-ion battery (LIB) modules. The focus is on evaluating the effectiveness of liquid nitrogen (LN) in inhibiting TR and its propagation in large-capacity lithium iron phosphate batteries. The following conclusions emerge by adjusting the LN injection pipe diameter and position: The best effective heat utilization efficiency of 6.1 % and total heat absorption of 526.9 kJ from the LIB by LN observed for a 20 mm diameter and top injection position. For diameters of 15 or 25 mm, the total heat absorbed by LN from LIB and effective heat utilization efficiency is lower at 470 kJ/5.3 % and 433.1 kJ/4.9 %, respectively. Injecting LN from the top of the module exposes the LIB undergoing TR directly to LN, resulting in optimal suppression of TR propagation. However, in other positions (back, left), TR propagates to the second battery, with the total heat absorbed by LN from the LIB and the effective heat utilization efficiency being only 222.2 kJ/2.6 % and 298.5 kJ/3.3 %, respectively. This work would provide valuable guidelines for suppressing TR and TR propagation in LIB modules.

The effect of fertilizer injection on the mixing patterns of lateral‐move sprinkler irrigation systems with double wings

AbstractIn irrigation systems, water–fertilizer mixing within pipelines profoundly affects the fertilization process and strategy development. Taking irrigation machine pipelines as the research object, a numerical simulation method is used to investigate the mixing and distribution patterns of water and fertilizer in pipelines under a steady oscillatory flow fertilization mode with different injection positions, angles, flow rates (Q) and fertilization ratios (δ). Increasing the flow rate initially increased the fertilizer concentration in the lateral pipes, but further increasing the mainline central injection flow rate significantly reduced the concentration in the lateral pipes. For δ = 2%, elevating Q from 6 to 8 m3/h increased the average fertilizer concentration in the lateral pipes by 0.4%. However, a subsequent increase to Q = 10 m3/h led to a 1% decrease. In left‐side injection, lateral pipes on the same side as the injection pipe had considerably higher concentrations than those on the opposite side. In central injection, larger inclination angles increase the lateral pipe fertilizer concentration, while in left‐side injection, 60°‐downward injection results in the best lateral pipe fertilizer concentration. The above‐mentioned results can provide valuable insights for the design of injection ports on lateral‐move sprinkler irrigation systems.

Combustion characteristics and performance analysis of a heavy-fuel rotary engine by designing fuel injection position

The heavy fuel rotary engine commonly operates under high-pressure direct injection, lean-burn and spark-assisted ignition modes, this characteristic feature further highlights the significance of the distance between fuel injection position (FIP) and assisted spark plug in engine combustion organization and performance improvement. Thus, a computational fluid dynamics (CFD) means coupled with chemical reaction kinetics is used to investigate the FIP effects on the fuel stratification rule and combustion performance of a heavy-fuel rotary engine. Meanwhile, the flow and combustion transient information in the narrow combustion chamber is analyzed by considering five specially designed FIPs, whose distances to the assisted spark plug along the X-axis (major axis) are 25, 30, 35, 40 and 45 (mm). The results indicate that the distance increases to 40 mm (FIP-40) and 45 mm (FIP-45), the fuel stratified distribution rule is more rational, the mixture burn rate accelerates, combustion time reduces, and combustion performance improves significantly. The FIP-45 scheme is the preferred engineering application scheme after comprehensively assessing engine performance parameters, and when compared to the FIP-35 (original scheme) its peak cylinder pressure (Pmax) increases by 5.3 %, CA10-90 accelerates by 20.4 %, and main emissions of Soot, NO and CO reduce by 48.1 %, 50.0 % and 36.2 % respectively, while CO2 increase.

Experimental study and kinetic analysis of NO emission characteristics in ammonia/coal co-firing process with different ammonia injection methods

Ammonia/coal co-firing in coal-fired power plants is an effective way to achieve CO2 reduction. In this paper, the ammonia/coal co-firing study was carried out in a 45 kW wall-temperature-controlled staged combustion downstream furnace at 1100 °C. Bituminous coal was used as the experimental object to analyze the effects of ammonia injected at the main combustion zone, reduction zone, with the burnout air, and at the burnout zone on NO release characteristics at different ammonia co-firing ratios. To ascertain the significant reaction of NO production in the ammonia/coal co-firing, chemical reaction kinetics calculations were performed. When co-firing ratios of 10∼30%, the NO emission concentration is lower by the ammonia injection position of the main combustion zone which is 275–346 mg/m3. When co-firing ratios reach to 40% and 50%, NO releases are lower by the ammonia injection position of burnout zone which is 511–574 mg/m3. In addition to exhibiting a greater capacity to decrease NO in environments with low oxygen concentrations and high NO concentrations, ammonia can also, under specific circumstances, have a significant capacity to decrease NO in environments with high oxygen concentrations. Based on the experimental results and chemical kinetic calculations, the NO release pattern and mechanism during ammonia-coal co-combustion with different ammonia injection methods under air staged combustion were investigated, which provides a technically feasible solution to reduce CO2 and NOx emissions from coal-fired power plants.

Study of hydrogen injection strategy on fuel mixing characteristics of a free-piston engine

The formation of the gas mixture in the cylinder has a significant effect on the combustion and emission of the engine. The main difference between a conventional engine and a free piston engine is that the piston movement mode is different. Therefore, a new coupled iterative method is adopted in this paper to study the injection position and duration of hydrogen fuel in a free piston engine where diesel fuels hydrogen, and reveal its influence on gas mixing and combustion in the cylinder of a free piston engine. The results show that it is suitable to spray hydrogen 55 mm from TDC. At this time, the mass fraction of H2 in the cylinder is relatively uniform, the cumulative heat release is about 620 J, and the pressure and temperature are relatively low, which are 7.2 MPa and 1529 K respectively. The duration of hydrogen injection is 0.4 ms, at this time, the mixing degree in the cylinder and the gas flow speed are better, although there is a little shortage of unburned equivalent ratio, but this has little impact on the overall, and the final cumulative heat release reaches 655 J.

Research on energy harvesting characteristics of a flapping foil with trailing edge jet flap

Flapping foils offer a potential means for extracting hydrokinetic energy from ocean and river flows by utilizing a combined pitching and heaving motion of the airfoil. In this paper, the effectiveness of trailing edge active flow control in enhancing the energy harvesting performance of the conventional flapping foil is examined through numerical simulations. In this approach, an injections slot is opened at the trailing edge of the flapping foil, from which a high velocity jet is discharged into ambient water. Since the water jet is issued vertically downwards perpendicular to the airfoil surface, it operates like a Gurney flap and thus is known as jet flap in aeronautics. Parametric studies show that the optimal injection position should be as far as possible from the leading edge of the flapping foil. In addition, it is also found when the width of the exit slot of jet equals to 2.6 % of the airfoil chord and the momentum coefficient of jet is 0.02, the flapping foil with the jet flap can increase the maximum net energy harvesting efficiency obtained after deducting the energy consumption for the flow control from 39.22 % to 47.6 % compared to its baseline counterpart, indicating the effectiveness of this method. Furthermore, the dynamic mode decomposition (DMD) method is also adopted to reveal the spatial-temporal features of the coherent structures in the wake flow behind the proposed flapping foil in an attempt to gain a deep understanding of the underlying flow mechanism involved in promoting its energy harvesting performance.

Laminar mixing of Newtonian and non‐Newtonian fluids in SMX static mixer

AbstractThis report is focused on understanding the mixing performance of Newtonian and non‐Newtonian fluids in an SMX static mixer through computational fluid dynamics (CFD) study in Simcenter STAR‐CCM+. For this, the standard SMX mixer with four mixer elements of radius 26 mm was chosen. The aspect ratio (L/D) was taken as 1. The model constructed was compared using pressure drop ratio values available in literature. First, the design was validated for Newtonian fluid, then for shear‐thinning fluid (non‐Newtonian). Mixing patterns produced through particle tracking approach revealed how blending improved as the fluid moved downstream and interacted with increasing number of mixer elements. A sensitivity study was undertaken to investigate the effect of particle injection mechanism on the mixing process. Two injection methods, vertical and horizontal, were explored to check the influence of injection position on mixing. The results indicate that for the given configuration irrespective of the injection location, at least four mixing elements are needed to achieve good mixing for both Newtonian and shear‐thinning fluids investigated in this study. Statistical reports were used to quantify mixing to understand the mixing behaviour for Newtonian and non‐Newtonian fluids with change in Reynolds number. At high Reynolds number, non‐Newtonian fluids exhibited better mixing abilities. Further, efforts were taken to optimize the various design parameters to produce the most optimum solution with a single mixer element for Newtonian fluid.

Dual-Alloy Sand Mold Casting: Main Principles and Features

AbstractThe multi-material injector casting (MMIC) process allows the production of castings with two different alloys in a single process. The metal is introduced into the mold through a ceramic down sprue (injector) that moves with the rising surface of the melt. This results in a beneficial temperature distribution in the casting with enhanced filling and feeding properties. Combining two alloys in one casting affects the chemical composition, microstructure, and mechanical properties, which differ from those of the original alloys. The main goal of producing the dual-alloy castings is to adapt the alloy locally in the mixing zone according to the application needs. The original composition and characteristics of both alloys have to be ensured as much as possible. This article discusses the peculiarities of dual-alloy sand mold casting, considering the oxidation processes of the components under different conditions and the microstructure of the resulting ingots. The results of thermodynamic simulation, experimental dual-alloy sand mold casting, chemical composition, and macrostructure of the resulting castings are given in the article. The following factors have been investigated: the method of pouring two alloys (AlSi12 and AlSi9Cu3), which simulate two injector positions; the time between pouring each alloy (60, 90, and 120 s); the influence of a directional solidification with the bottom chill. The mixing zone was identified by the changes in the content of Cu measured by spark spectroscopy and EDS.

Coupled effect of injection position variation on gas exchange stability of a free-piston engine

Gas exchange fluctuations may lead to operation instability of the free-piston engine (FPE), because the engine has a coupling effect between the gas exchange and the piston motion, which is different from a conventional engine. It is, therefore, important to study the gas exchange instability to ensure the stable operation of the engine. This study focuses the effect of variable piston position when injecting on the gas exchange stability of a looped scavenging FPE, and a systematic full-cycle gas exchange model is presented by developing a dynamic model, a combustion model, and a multidimensional scavenging model. Meanwhile, an iterative method between motion and scavenging is used to solve the model numerically for gas exchange simulation, and the effects of variable piston position when injecting on piston motion, thermodynamic in cylinder, and gas exchange process are studied. The results indicate that retarding injection induces instability of gas exchange duration which first increases and then decreases, and there is an injection position which is most conducive to the increase of capture efficiency of gas exchange, although the scavenging efficiency is lowest under this condition. This result also suggests that more complete exhaust may be achieved by a different injection position.

Experimental study on the effects of ammonia cofiring ratio and injection mode on the NOx emission characteristics of ammonia-coal cofiring

Ammonia (NH3) cofiring is a promising approach to reduce the CO2 emissions from coal-fired power plants. However, the potential drastic increase of NOx emissions may inhibit the wide implementation of NH3 cofiring. To explore the potential NOx control strategies, the effects of NH3 cofiring ratio (RNH3), NH3 injection mode and overfire air (OFA) rates on the NOx emission characteristics of NH3/coal cofiring are studied in a test furnace that allow for flexible control of the injection positions and combustion environment of NH3. The results show that when NH3 is injected with coal stream (top mixing mode), the NOx emissions increase and then decrease with the increase of RNH3 under all OFA rates. However, when NH3 is fed through the side port of furnace separately (side mixing mode), the NOx emissions exhibit distinct trends under different OFA rates. Under lower OFA rates, the NOx emissions show monotonical decrease with the increase of RNH3, while under higher OFA rates the NOx emissions first decrease and then increase with the increase of RNH3. Consequently, higher OFA rates could produce higher NOx emissions than lower OFA rates. This indicates that air-staging is not always effective in the NOx reduction of NH3 cofiring. Thus, although the side mixing mode of NH3 cofiring exhibits overall better performance in NOx control, caution is needed to accommodate the OFA rate with NH3 cofiring ratio. Although a variety of trends of NOx emissions were observed in this study, the results demonstrate that all these trends are in fact governed by the same mechanism – the competition between the NO-formation and NO-reduction reactions of NH3 in the varying O2 environment in the furnace. By creating appropriate O2 environment in the furnace, the NOx emissions of NH3/coal cofiring could be substantially lower than that of pure coal combustion. The findings of these paper are instrumental in the design and operation of NH3 cofiring system in full scale coal-fired boilers to achieve effective NOx control.

Influences of removable gas injection methods on the temperature field and gas composition of the underground coal gasification process

In this paper, the effects of changing the injection position of a gasification agent on temperature fields and gas compositions are investigated through an experimental model of the underground gasification of coaxial coal. A 3D model of the temperature field is constructed based on the experimental temperature parameters using kriging interpolation; the 900 °C isothermal surface is used as the reference plane to define the oxidation zone, and its plane and volume expansion rate are analyzed. The underground coal gasification experiment is divided into five stages according to the injection location. The average expansion rates of the oxidation zone in each stage are 2.04 cm/h, 1.93 cm/h, 3.44 cm/h, 3.68 cm/h, and 3 cm/h along the X-direction and 0.69 cm/h, 0.09 cm/h, 0.56 cm/h, 1.69 cm/h, and 1.01 cm/h along the Z-direction; the expansion rate along the X-direction is greater than that along the Z-direction. The expansion volumes of the oxidation zone after the five stages increase from 0.0097 m3 to 0.0168 m3, 0.0321 m3, 0.0521 m3 and 0.0657 m3. An analysis of the expanded volume of the oxidation zone compared with the volume of the cavity shows that both features are similar in shape and that the final volume of the cavity is smaller than the final expanded volume of the oxidation zone; the volume of the cavity is approximately 77.3 % of the expanded volume of the oxidation zone. The formation of a cavity requires the temperature to reach the conditions for the oxidation reaction of the coal and the rupture and flaking of the ash layer that accumulates after the reaction by the actions of certain stresses, such as thermal. The composition of the product gas and the strength of the chemical reactions involved are evaluated based on stoichiometric conservation. A short period after a shift in the injection position of the gasifier greatly impacts the chemical equilibrium of the UCG process with a large change in the strength of the chemical reaction, followed by a relatively small change when the gasification process stabilizes.