Combustion Chamber Of Engine Research Articles

Fuel Injection Optimization for Large-Bore Two-Stroke Natural-Gas Engines

Recent methane emissions regulations present a challenge for the large-bore, natural-gas-fueled engines used at over 1700 compression stations across the US. Poor air–fuel mixing in the main combustion chamber of these engines results in low combustion efficiency and the resulting methane emissions. High-pressure fuel injection is believed to be a significant development in improving air–fuel mixing in natural-gas engine combustion chambers. This study aims to determine the sensitivity of in-cylinder mixing to injection pressures using Computational Fluid Dynamics (CFD) simulations, determine the limits of high-pressure fuel injection, and explore high-momentum low-pressure fuel injection. The engine, modeled using Converge Studio for CFD, was a Cooper-Bessemer large-bore, four-cylinder, GMV-4TF spark-ignited natural-gas engine with direct injection. The model was simulated for four sets of configured cases—baseline; ideal mixing; injection pressure variation; and low-pressure, high-momentum injection. The results show that fuel injection at 700 psi and −115 degrees BTDC gives the best in-cylinder mixing and improved mixing, potentially reducing methane emissions by half. The optimal timing for the injection at different injection pressures was determined. The level of mixing in low-pressure fuel-injection systems was also improved by the high-momentum fuel injector design. It was concluded that mixing can be further improved in integral gas compressor engines through fuel injection optimization.

Comparative study on the adaptability of diesel/aviation kerosene in rotary engines

It is of great significance to compare the spray characteristics and combustion characteristics of aviation kerosene and diesel in rotary engine condition when looking for the alternative of diesel in rotary engines. In this paper, several combustion characteristics of diesel and aviation kerosene were obtained by spray experiment, including ignition characteristics, ignition delay period, flame floating length, and other combustion characteristics under rotary engine conditions. After that, a three-dimensional dynamic model of the rotary engine is established and verified by the experimental data. On this basis, the combustion process of diesel engine and aviation kerosene engine under different injection strategies is simulated. Normal ignition of diesel requires environmental conditions to reach 750 K/2.5 MPa, while aviation kerosene needs to reach 800 K/2.0 MPa to achieve stable combustion, which indicates that aviation kerosene has higher requirements for the environment. However, under the rotary engine condition, the atomization quality of aviation kerosene is better than that of diesel, and it has higher combustion, heat release and work capacity and faster flame propagation speed. Therefore, aviation kerosene can be used as the fuel of rotary engine instead of diesel. Especially in Case A3, the peak pressure in the combustion chamber of the aviation kerosene rotary engine reaches 38.89 bar, showing obvious advantages over the diesel rotary engine. In addition, the soot emissions of aviation kerosene engines are significantly lower than those of diesel rotary engines.

Data-driven multifidelity surrogate models for rocket engines injector design

Abstract Surrogate models of turbulent diffusive flames could play a strategic role in the design of liquid rocket engine combustion chambers. The present article introduces a method to obtain data-driven surrogate models for coaxial injectors, by leveraging an inductive transfer learning strategy over a U-Net with available multifidelity Large Eddy Simulations (LES) data. The resulting models preserve reasonable accuracy while reducing the offline computational cost of data-generation. First, a database of about 100 low-fidelity LES simulations of shear-coaxial injectors, operating with gaseous oxygen and gaseous methane as propellants, has been created. The design of experiments explores three variables: the chamber radius, the recess-length of the oxidizer post, and the mixture ratio. Subsequently, U-Nets were trained upon this dataset to provide reasonable approximations of the temporal-averaged two-dimensional flow field. Despite the fact that neural networks are efficient non-linear data emulators, in purely data-driven approaches their quality is directly impacted by the precision of the data they are trained upon. Thus, a high-fidelity (HF) dataset has been created, made of about 10 simulations, to a much greater cost per sample. The amalgamation of low and HF data during the the transfer-learning process enables the improvement of the surrogate model’s fidelity without excessive additional cost.

Determining the optimal oxidation temperature of non-isothermal liquid fuels injections using modeling based on statistical droplet distribution

Single-hole injections of liquid hydrocarbon fuels (isooctane and dodecane) under high turbulence have been investigated using direct numerical simulation based on the statistical model considering the droplets’ atomization, distribution, and combustion. The study objects are the heat and mass transfer processes during atomization and combustion of liquid fuels injections within the combustion chambers of thermal engines. The temperature and carbon dioxide concentration distributions of the fuel-air mixture, the distributions of the droplets, their velocities, and the Sauter mean radius within the isooctane and dodecane oxidation in the engine’s combustion space were obtained. An investigation of the oxidizer’s initial temperature influence on the droplets’ atomization and combustion processes showed that the optimal temperature for both fuels is 900 K. The obtained modeling results were confirmed in good agreement with theoretical and experimental data. Thanks to the integrated use of approaches from statistical theory, numerical algorithms and 3D computer modeling techniques, the results obtained are distinguished by high accuracy, efficiency in reducing computational resources, scientific novelty in the type of droplet atomization and suitability for practical application for technological solutions not only for single-hole, but also for multi-hole injections of liquid fuels and studying the jet-to-jet interaction phenomena. The obtained research results can be applied in miscellaneous internal combustion engines development with different atomization types, which will allow us to contemporaneously settle the concerns of streamlining the combustion process, improving the completeness of fuel combustion and reducing emissions of harmful substances

Model of interaction between laser radiation and metal powder composition during direct laser growth

This paper presents a model for analyzing the interaction of laser radiation and a metal-powder composition in the process of direct laser growing of large-sized combustion chambers of gas turbine engines. The metal-powder composition is fed into the melting zone coaxially with laser radiation; the task is to completely melt the powder with laser radiation before it enters the melt bath on the construction platform. The laser radiation is absorbed as it passes through the gas-powder jet, and its energy is also used to melt the construction platform or the previous layer. Thus, in order to determine the parameters of the operating conditions that provide the possibility of melting powder particles, it is necessary to determine the boundaries of the parameters at which each particle of the metal-powder composition completely melts in a gas-powder jet. To simulate heat transfer inside a particle, the Beer – Lambert laser radiation absorption law was used using the lumped parameter approach. The required energy for melting the powder material was determined through enthalpy. The resulting one-dimensional differential equation of enthalpy increment is solved numerically by the Euler method. Using this model, the distance from the point of origin of the interaction of the laser beam with a metal-powder composition to the zone of its complete melting was determined and the effect of the velocity of the gas-powder jet, the power of laser radiation, the bulk density of the metal-powder composition and the average radius of the powder particles on the distance to the zone of complete melting was studied.

MATHEMATICAL MODELING OF THE DYNAMICS OF THE AEROELASTIC "PIPELINE – PRESSURE SENSOR" SYSTEM

This paper proposes mathematical models of mechanical systems "pipeline - pressure sensor" designed to control the pressure of the working medium in the combustion chambers of engines. In such systems, to mitigate the impact of vibration accelerations and high temperatures, the sensor is connected to the engine using a pipeline and is located at some distance from it. The movement of the working medium is described by linear models of fluid and gas mechanics. To describe the dynamics of an elastic sensitive element, linear models of the mechanics of a solid deformable body are used. Based on linear differential equations with partial derivatives, mathematical formulations of problems are proposed that correspond to three-dimensional models of pressure measurement systems in gas-liquid media for some pipeline cross-sectional shapes, namely, for a pipeline with a rectangular cross-section, with a section in the form of a sector and in the form of a ring. By introducing integral characteristics, the solution of problems is reduced to studying one-dimensional models. Equations have been obtained that make it possible to determine the pressure of the working medium in the combustion chamber at each moment of time by the value of deformation of the sensitive element of the sensor. Analytical and numerical-analytical methods for solving the corresponding initial-boundary value problems for systems of differential equations are proposed. In the analytical approach, the solution of the problem is reduced to solving a differential equation with a deviating argument. The numerical-analytical study of the problem is based on the application of the Galerkin method. Also, a numerical experiment was carried out and examples of calculating the deformation of the sensitive element of the sensor in the case of rigid fastening when specifying specific values of the mechanical parameters of the system are presented, also during setting the law of change in the excess pressure of the working medium in the engine.

The Effect of Engine Noise on the Comfort of WA-360 Loader Heavy Equipment Operators Based on Capacity and Distance of 100, 150 and 200 cm

The existence of a limited volume of machine room and coupled with the existence of various kinds of machinery in it, both main drive machinery such as the main motor and other supporting machinery such as electric motors, compressors, pumps and so on, all of which are sources of noise, will cause high noise noise. Where heavy equipment is a tool used to simplify the work process so that it becomes faster, easier and the results are in accordance with expectations and one example is the Whell Loader WA-360 heavy machine. Therefore, research is needed to measure the level of noise produced by the Whell Loader WA-360 heavy equipment engine to operator comfort. According to NAB According to Kepmenaker No. per-51/MEN/1999,2008 and SNI 16-7063-2004, the noise level that results in hearing damage of 90 dB for workers who are working for 8 hours per day. That the threshold value for the noise of the combustion chamber of the Wheel Loader WA-360 heavy equipment engine with a bucket capacity of 3.4 and 5 tons produces a noise level of 106.5 dB with a hearing scale and it is recommended that the operator of the Whell Loader heavy equipment use Earphones while doing work.

Mathematical models of system of measure of pressure variation in combustion chambers of engines

In this paper the mathematical modelling of a mechanical system designed to control changes in the pressure of the working medium in aircraft engines and consisting of a pipeline and a pressure sensor is carried out. The pipeline is necessary to take the sensor to some distance from the engine in order to mitigate the impact of high temperatures and vibration accelerations on the sensitive element of the sensor, which is an elastic plate. The system takes into account the aerohydrodynamic and thermal effects of the working medium on the plate. Asymptotic equations of aerohydrodynamics in the models of compressible and incompressible medium are used to describe the working medium motion in the pipeline. Both linear and nonlinear models of a deformable solid body are proposed to describe the plate dynamics. When using the compressible medium model, the solution of the problem is reduced to the study of an equation with a deviating argument. To solve the problem using the incompressible medium model, Fourier and Galerkin methods are applied. As a result, for both models the solution of the problem is reduced to the study of ordinary differential equations relating the magnitude of pressure in the motor with the magnitude of deformation of the sensing element, which can be used to control the mode of operation of the motor. The solution of these equations is found with the developed software program using standard functions of Mathematica 12.0. The paper was presented at PhysCon2024.

Experimental Analysis of Long-Term Fuel Trim Performance in a Gasoline Engine Under Various Operating Conditions

This paper analyzes the effect of operating conditions on the enrichment of the fuel-air mixture in a car engine due to a decrease in air mass with increasing altitude above sea level. This study focuses on fuel trim, particularly long-term fuel trim, in optimizing the composition of the fuel-air mixture before it enters the engine's combustion chamber. Experimental studies were conducted on the Bishkek–Osh highway in the Kyrgyz Republic, a road characterized by flat, mountainous, and high-altitude sections with complex terrain. Based on the research objectives, experimental results were obtained, and graphs of long-term fuel trim as a percentage of terrain altitude were constructed and analyzed for flat, mountainous, and high-altitude sections of the Bishkek–Osh highway. The study established that fuel trim indicators can be used to analyze changes in the air-fuel mixture's air excess coefficient (λ = 1, stoichiometric ratio). The reduction in long-term fuel trim was observed in flat, mountainous, and high-altitude sections as air density and pressure decreased with increasing altitude above sea level. The results show that with a reduction in long-term fuel trim to -6.25% to -7.81% at altitudes between 1500 and 3000 meters above sea level, the air excess coefficient (λ) drops to 0.92–0.94. At an altitude of 770 meters (flat terrain), λ was measured at 0.97. The difference in λ (0.03–0.05) indicates that an increase in altitude significantly affects the air-fuel ratio (AFR), impacting mixture formation during vehicle operation in mountainous and high-altitude conditions.

Velocity-driven optimization of film cooling in methane/oxygen rocket engines using coupled wall function

This study investigates the application of coupled wall functions to the research of film cooling in methane/oxygen rocket engine combustion chambers. By manipulating film mass flow rate and inlet size, the influence of different film-mainstream velocity ratios on flow dynamics, combustion, wall heat transfer, and cooling efficiency within the combustion chamber is explored. Results indicate that as the ratio of film velocity to mainstream velocity (RV) increases, the combustion chamber pressure initially decreases before increasing, with a corresponding trend observed in vortex intensity at the inlet section. Comparative analysis reveals that, while maintaining a constant mass flow rate, reducing the film inlet height results in lower pressures and weaker swirl strength. Furthermore, wall heat transfer decreases gradually with increasing RV, with lower heat transfer observed in cases involving additional low-temperature methane injection. Notably, the introduction of coupled wall functions minimally impacts mainstream flow and combustion. Analysis of Net Heat Flux Reduction (NHFR) indicates a rapid decrease in cooling efficiency in the front half of the combustion chamber, emphasizing the suitability of employing a film cooling inlet every one-fifth section in a methane/oxygen engine. Moreover, increasing the mass flow rate enhances cooling efficiency as RV increases, while altering the inlet size yields nearly constant cooling efficiency. Therefore, maximizing film mass flow rate is deemed preferable for film cooling arrangements in a specific rocket engine; however, comparative studies reveal a gradual reduction in engine specific impulse with increasing mass flow rate, underscoring the necessity for engine-specific determinations.

Comparative analysis of metal oxide nanoparticle accumulation in landfill gas engine combustion chambers: Insights from three sites

Combustion chamber deposits adversely affect the operating performance of gas engines. In this study, the elemental composition of deposit samples collected from the inner surface of combustion chambers in gas engines across three different facilities was examined using various methods. The proportional changes in metal oxides along the internal cross-sectional surfaces of the deposits were examined to depict the deposit formation process from beginning to end. Additionally, the study investigated the identification of metals accumulated in the engine oil, their contribution to deposit formation, and the accumulation mechanisms of metal oxide nanoparticles on the engine’s interior metal surfaces. The main elements identified in the deposits from the Odayeri and Kömürcüoda facilities were Si, S, and Ca, whereas deposits from the Dilovası facility contained Si and Sb. These major elements, identified by SEM-EDS, were confirmed through XRF analysis. XRD analysis further confirmed the presence of Ca and S as CaSO4 crystals in the deposits. Ca originates from additives used to increase the total base number of engine oil and control the corrosive effects of landfill gas. It has been determined that silicon accumulates in engine oil over time. An important finding is that metal oxides in the combustion chamber primarily accumulate through impaction, sticking, and thermophoresis mechanisms.

BSO algorithm and artificial neural network aided emission optimisation for gas turbine engine

Abstract Aircraft play a major role in meeting the fast and efficient transportation needs of modern society, thanks to their advanced features. However, gas turbine engines used in aircraft have many negative effects on human health. One of the negative effects is the exhaust gases released by these engines to nature. In this study, it is discussed to present alternative models based on heuristic methods to reduce the emission values of the synthetic fuel mixture used in the combustion chamber of gas turbine engines. For this purpose, a model based on artificial neural networks (ANN) based on the back-tracking search optimisation (BSO) algorithm is proposed by using experimentally obtained emission values found in the literature. In the proposed model, the parameters of the optimum ANN structure are first determined by the BSO algorithm. Then, by using the optimum ANN structure, the most appropriate input values were found with the BSO algorithm, and the emission values were reduced. The simulation results have shown that the proposed method will be a fast and safe alternative method for reducing emission values.

Diagnosing the Process of Forming Biofuel Combustion Mixtures in Diesel Engines by a Program to Compute Spray Volume

A diesel engine's injection and combustion mixture formation process are essential; it determines the engine's economic, technical, and environmental criteria. When the engine uses biofuel, fuel parameters such as viscosity, density, and surface tension affect the above process. Each engine using a specific fuel type will have to adjust injection parameters such as injection pressure and timing to ensure the injection process and formation of a homogeneous air-fuel mixture. Therefore, through the spray structure, it is possible to diagnose the process of combustion mixture formation, thereby making adjustments to the fuel injection system that will improve engine performance and reduce emissions of toxic exhaust gases. In this study, the article presents the content of building a program to compute spray volume using Matlab software. Through the spray volume, quickly diagnose the process of forming the biofuel-air mixture in the diesel engine combustion chamber, thereby determining the appropriate fuel injection system adjustment. Results of simulation and experimental research on 4CHE Yanmar engines installed on fishing vessels with fuel types DO, B5, B10, and B15 show that the B15 fuel mixture when used for the engine needs to be increased injection pressure is about 10% higher than DO fuel injection pressure.

Comprehensive Analysis of Tubular Combustion Chambers in Turbo-Ramjet Engines for Enhanced Hypersonic Propulsion

Comprehensive Analysis of Tubular Combustion Chambers in Turbo-Ramjet Engines for Enhanced Hypersonic Propulsion

Research on accelerated thermal fatigue testing and life prediction of Al-Si alloy pistons under start-stop cycles

As one of the most critical components in the combustion chamber of diesel engines, pistons operate under high temperature and pressure conditions for extended periods, which increases the likelihood of failures such as thermal fatigue. This paper first utilizes finite element simulation to obtain the temperature and stress field distribution of an Al-Si alloy piston under actual engine conditions. The results indicate that the throat area of the piston is the most susceptible to fatigue failure. Based on this, accelerated thermal fatigue tests were conducted to study the influence of various experimental factors on piston life, as well as to analyze the weight of each factor. Results from macroscopic and microscopic analyses of cracks using a scanning electron microscope show that fatigue cracks originate at the interface between the aluminum matrix and the detached hard particles. The cracking at the piston throat exhibits clear characteristics of ductile fracture, which is the result of cumulative fatigue damage. Therefore, from the perspective of continuum damage mechanics, it is considered to characterize the equivalent stress using the average loading rate during the loading phase and the maximum axial temperature gradient, establishing an experimental life prediction model for Al-Si alloy pistons.

A microwave discharge in high-velocity flows initiated by a half-wave antenna

A microwave discharge in high-velocity (150—250 m/s) air flows induced on a half-wave vibrator is studied. A cw magnetron microwave generator with a frequency of 2.45 GHz and an output power of up to 5 kW was used for initiation of the microwave discharge. The high-speed video imaging was used for studying the discharge structure, determining the diameter and length of the plasma channel as a function of flow velocity and pressure. Electron concentration and temperature, along with characteristic gas temperature, were determined based on the optical spectra. The possibility of using this microwave discharge for ignition of hydrocarbon–air mixtures in combustion chambers of ramjet engines is proved experimentally.

Numerical study on hydrogen mixing for different scramjet Engine combustion chamber configurations

Numerical study on hydrogen mixing for different scramjet Engine combustion chamber configurations

Experimental Study on the Mass Flow Rate Characteristics of a Fluidized Bed Powder Fuel Feeding System

In this study, a fluidized bed powder fuel feeding system that controls flow using the principle of two-phase gas-solid choking is proposed. Experiments based on real-time weighing methods were conducted to explore the flow rate characteristics under various total pressure and throttle-orifice area conditions. The experimental results showed that as the total pressure increased, the powder flow rate first decreased and then increased. To achieve the same increase in powder mass flow rate by altering the pressure, fine powder requires a greater pressure increment than coarse powder. A choked flow formula based on the gas-solid two-phase nonequilibrium model was derived, for investigating the influence of these two factors on the powder flow rate. Compared with the experimental results, this formula predicts the powder flow rates within a 20 % error margin. This model provides more precise guidance for engineering designs. The studied powder fuel-feeding system was connected to a powder engine, and hot-fire tests were conducted. The results showed that the pressure fluctuation in the powder engine combustion chamber did not exceed 2.5 %, confirming the feasibility and stability of the powder supply in the fluidized bed powder fuel feeding system.

Design and Analysis of Cooling Systems for Combustion Chambers in Turbine Engines: A Comparison of Oil and Gas Cooling Fluids

This study focuses on the design and analysis of a cooling system for a combustion chamber in a turbine engine. The objective is to compare the cooling performance of oil and gas as cooling fluids using CAD modeling in CATIA and computational fluid dynamics (CFD) simulations in ANSYS Fluent. The design requirements, including cooling rate, pressure drop, temperature requirements, fluid properties, material compatibility, and environmental impact, were defined and incorporated into the CAD model. The CFD simulations were conducted to evaluate the temperature distribution and pressure dynamics within the combustor chamber. The results provided insights into the advantages and drawbacks of using oil and gas as cooling fluids, considering factors such as heat absorption, thermal conductivity, viscosity, pressure drop, and power consumption. Material compatibility and environmental considerations were also addressed. The findings offer a foundation for informed decision-making regarding the selection of the most suitable cooling fluid. However, real-world testing is recommended to validate the simulation results and ensure the chosen cooling fluid meets the design requirements effectively and efficiently. By combining computational simulation and physical testing, this study contributes to the design of efficient and durable cooling systems for gas turbine engines.

A molecular dynamics study on the supercritical evaporation of liquid ammonia under forced convection conditions

Although the behavior of the supercritical transition during the evaporation of liquid fuels in engine combustion chambers has been studied by many researchers, the effects of convection on the phase transition of liquid fuel in supercritical environments have been little studied. Previous studies mainly focused on hydrocarbon fuels for supercritical evaporation, with fewer on the zero-carbon liquid ammonia fuel. Aiming at the above deficiencies, this study used molecular dynamics simulations (MD) to explore the phase transition of liquid ammonia in a nitrogen supercritical environment under forced convection conditions. The Peng-Robinson equation of state (PR-EoS) was used to calculate the vapor–liquid equilibrium of the ammonia–nitrogen system to determine the supercritical transition time of liquid ammonia under forced convection conditions. The effects of forced convection on the heat and mass transfer process and the evolution of the liquid-phase region and the vapor–liquid interface region were analyzed. It was found that forced convection can promote the mass and heat transfer process and accelerate the phase transition of liquid ammonia to some extent. Forced convection may have a greater effect on the single-phase diffusive mixing process compared to the two-phase evaporation process. The increase in the interfacial thickness under forced convection conditions is mainly attributed to the temperature increase promoted by convection. The interfacial temperature dominates the development of its thickness and the thickness is approximately linear with temperature during the diffusive mixing stage. The shear effect induced by convection has an inhibitory effect on the diffusion of ammonia molecules within the interface region along the vertical convection direction. The cases in this study indicate that forced convection may promote the supercritical transition of liquid ammonia. In addition, a dimensionless number κ was proposed to explore the possibility of scaling up the MD results to the engineering scale.