Gas Engine Research Articles

Thermodynamic Model for Hydrogen Production from Rice Straw Supercritical Water Gasification.

Supercritical water gasification (SCWG) technology is highly promising for its ability to cleanly and efficiently convert biomass to hydrogen. This paper developed a model for the gasification of rice straw in supercritical water (SCW) to predict the direction and limit of the reaction based on the Gibbs free energy minimization principle. The equilibrium distribution of rice straw gasification products was analyzed under a wide range of parameters including temperatures of 400-1200 °C, pressures of 20-50 MPa, and rice straw concentrations of 5-40 wt%. Coke may not be produced due to the excellent properties of supercritical water under thermodynamic constraints. Higher temperatures, lower pressures, and biomass concentrations facilitated the movement of the chemical equilibrium towards hydrogen production. The hydrogen yield was 47.17 mol/kg at a temperature of 650 °C, a pressure of 25 MPa, and a rice straw concentration of 5 wt%. Meanwhile, there is an absorptive process in the rice straw SCWG process for high-calorific value hydrogen production. Energy self-sufficiency of the SCWG process can be maintained by adding small amounts of oxygen (ER < 0.2). This work would be of great value in guiding rice straw SCWG experiments.

Thermodynamic modeling and performance analysis of chemical looping gasification combined with steam reforming for municipal solid waste: An Aspen Plus approach

Chemical looping gasification combined with steam reforming (CLG-SR) holds great promise for improving energy efficiency and streamlining the production of renewable H2 and synthetic fuels. In this investigation, the process underwent simulation and analysis using Aspen Plus, offering valuable insights into product outcomes, environmental impacts, and economic performance. The accuracy of the model was validated against experimental results from the literature, yielding a root mean square (RMS) of 4.17 %, thereby demonstrating its high feasibility. The findings demonstrate that within the temperature range of 700–800 °C, H2 achieves notable selectivity, reaching 60.68 % selectivity at 700 °C. When the steam-to-municipal solid waste (MSW) ratio surpasses 0.9, H2 demonstrates elevated selectivity. Notably, it is crucial to observe that the selectivity of CO2 also escalates concurrently with that of H2. Specifically, at steam-to-MSW ratio (SMR) of 0.9, the selectivity of H2 attains 60.72 %, whereas the selectivity of CO2 attains 27.69 %. Under these parameter conditions, H2, purified through pressure swing adsorption (PSA), constitutes 68.59 % of the total input H elements, leading to an impressive energy efficiency of 47.76 %. The economic analysis, based on the model, discloses a material consumption of 7.40 tons per ton of H2, resulting in a total production cost of 2487.20 USD per ton of H2. The study bears paramount strategic significance for advancing the in-depth research and development of chemical looping gasification technology.

Performance evaluation of red mud-based oxygen carriers in the chemical looping gasification of wet sludge rich in iron

A high-performance and low-cost oxygen carrier (OC) is the key for industrialization of chemical looping gasification (CLG) technology for sludge treatment. In this work, four OCs (RM_15 %CuO, RM_10 %CuO, RM, RM_POC) were prepared in an industrial-scale granulation equipment. The red mud was composited by mixing with different amounts of CuO and MnO2, then subjecting to different calcination temperatures. Firstly, the oxygen decoupling and oxygen carrying capacities of the OCs were compared using 5% H2 as the reducing agent. RM_15%CuO and RM_POC showed excellent oxygen release capabilities, with oxygen release loss of −1.99 % for RM_15%CuO. The catalytic gasification performances of RM_15%CuO and RM_POC were evaluated in a lab-scale fluidized bed reactor with wet sludge as the feedstock. Both OCs were able to maintain the H2 concentration of over 44.6% and no less than 79.2% sludge gasification efficiency after 30 cycles. However, the H2 content was clearly higher in case of RM_POC. SEM-EDS was used to analyze the influence of sludge ash, rich in Fe, on the performance of two OCs after the fluidized bed operation. The results showed that the sludge ash sample with more than 20% Fe2O3 could transfer its lattice oxygen to assist OC and prevent the in-situ segregation of Fe phase in the POC surface. However, the inhibitory effect of RM_15%CuO was much lower. The degradation performance of RM_POC carrier was slower and thus the H2 content was higher. This performance evaluation provides a theoretical guide for chemical looping gasification of sludge in future with an idea of mixed ratio of recycling sludge ash to the RM_POC.

Numerical simulation of ash deposition behavior in radiant syngas cooler coupled with impact surface temperature

Radiant syngas cooler (RSC) is a crucial heat recovery device for entrained-flow coal gasification technology. However, ash deposition in an RSC can severely affect operating efficiency and safety. An ash deposition model coupled with the impact surface temperature was established based on the ash particle deposition morphology. The effects of different operating conditions on ash deposition characteristics are discussed. The simulated data agreed well with the industrial data. The results indicate that ash particles were primarily deposited in the collision deposition zone. The maximum deposition thickness of radiation screen and cylinder membrane wall is 9.82 mm and 1.88 mm, respectively. The ash deposition hindered heat transfer process and the highest heat flux was observed in the middle part of the RSC. Ash deposition around 5.3 m increases significantly with an increase in the inlet syngas temperature. Increasing the load increased probability of ash particle collision and the area of influence.

ANALYSIS OF ACCIDENTS DURING DRILLING WITH FLOATING DEVICES IN THE CASPIAN SEA

At drilling of chinks on areas Gunashli, May 28, Bahar, Neft Dashları, Bulla with density of a chisel solution above (1.9-2,0)·104 N/m3 on depth 2000÷4500 m with balance in system the chink-layer is observed decrease in density of a chisel solution to 1,25÷1,30 g/sm3 with the subsequent open gas fountains. The gas getting in chink by diffusion basically comes to light at washing after lifting and descent of the boring tool. In trenches there are elements of the aerated solution, which density a little above before the circulating. Diffusion is the phenomenon caused by movement of molecules. A principal cause of diffusion of gas is presence of a gradient of concentration. Receipt of gas with diffusion from a layer in a chink will take place until gas molecules goes from a zone with high concentration in zones with low concentration, i.e. in chink. Getting to a chisel solution, diffusion gas, go up together with solutions and passing from zones of high pressures in zones low, extends, therefore its density decreases, that, in turn, conducts to decrease in hydrostatic pressure in a face of a chink and to serious complications. The article examines and analyzes the main causes of complications and accidents that arise during the construction, operation and repair of oil and gas wells, and leading to gas and oil shows, open fountains and fires in the fields of Azerbaijan. The ways in which complications arise during the extraction of hydrocarbons are briefly discussed. The conditions and nature of the occurrence of complications leading to accidents, gas manifestations, open fountains and fires are analyzed. Based on an analysis of the complications that arise during the construction, operation and repair of oil and gas wells, technologies and technical means are presented that make it possible to improve the quality of repair work carried out on oil and gas wells during their construction and operation. Equipment and tools for emergency response are considered. Technologies are proposed for eliminating accidents associated with the breakage and fall of downhole tool equipment onto the bottom, with cleaning the bottom of foreign objects, and with the elimination of stuck pipes. Modern technologies for eliminating gas shows and open fountains complicated by a fire at the mouth of a gushing well are proposed. In a chink it is required to make washing of a chisel solution for prevention of complications with closed preventer with dispersing of a boring column. Keywords: well, manifestation, gas, diffusion, pressure, washing solution.

Deflagration Dynamics of Methane–Air Mixtures in Closed Vessels at Elevated Temperatures

In this paper, we explore the deflagration combustion of methane–air mixtures through both experimental and numerical analyses. The key parameters defining deflagration combustion dynamics include maximum explosion pressure (Pmax), maximum rate of explosion pressure rise (dP/dt)max, deflagration index (KG), and laminar burning velocity (SU). Understanding these parameters enhances the process of safety design across the energy sector, where light-emissive fuels play a crucial role in energy transformation. However, most knowledge on these parameters comes from experiments under standard conditions (P = 1 bar, T = 293.15 K), with limited data on light hydrocarbon fuels at elevated temperatures. Our study provides new insights into methane–air mixture deflagration dynamics at temperatures ranging from 293 to 348 K, addressing a gap in the current process industry knowledge, especially in gas and chemical engineering. We also conduct a comparative analysis of predictive models for the laminar burning velocity of methane mixtures in air, including the Manton, Lewis, and von Elbe, Bradley and Mitcheson, and Dahoe models, alongside various chemical kinetic mechanisms based on experimental findings. Notably, despite their simplicity, the Bradley and Dahoe models exhibit a satisfactory predictive accuracy when compared with numerical simulations from three chemical kinetic models using Cantera v. 3.0.0 code. The findings of this study enrich the fundamental combustion data for methane mixtures at elevated temperatures, vital for advancing research on natural gas as an efficient “bridge fuel” in energy transition.

Research on the ignition mechanism and structural optimization of turbulent jet pre-chamber in GDI engines

Turbulent jet ignition has been widely studied, but it is mainly focused on gas engines, the igniting mechanisms of pre-chamber (PC) on GDI engines and the contributions of heat and radicals of the jet in inhomogeneous charge still remain to be clarified. Thus, 3-D simulations with comprehensive spray mixing process were performed under variable structural parameters. The decoupling results of thermal and chemical effects show that the influence of jet temperature on the heat release rate (HRR) inside main chamber (MC) is greater than that of free radicals. The mechanism of hot jet ignition containing free radicals in MC is flame propagation without ignition delay. However, compared to jet temperature, the free radicals in the jet have less effects on HRR in MC after the ignition. The nozzle diameter significantly affects fuel entry into the PC, influencing the pressure difference between PC and MC, and thus the jet velocity and duration. The optimal diameter in this study is 1.0 mm, and the jet duration is prolonged for too small or too large diameters. The nozzle angle is constrained by combustion chamber geometry, with the optimal angle being 140° to avoid jet impingement on cylinder head or piston.

Separation behavior of metal and oxide: Vacuum gasification for metal recovery advanced from lead anode slime

Lead anode slime (LAS), a significant secondary resource, was utilized to separate andrecycle of rare and precious metals such as Te, Au, and Ag, along with essential metals Cu, Pb, and Bi. The conventional pyrometallurgical and hydrometallurgical processes generated hazardous waste, including high levels of As, Sb, smoke, heavy metal waste. Extraction of these key metals is both laborious and ineffective. A novel vacuum gasification technology was employed to explore the separation patterns and migration distribution principles of metal and oxide (MO) in LAS. The theoretical results of phase transition enthalpy change (ΔH), saturated vapor pressure, and molecular average free path investigated the gasification and volatilization potential of MO in LAS. Furthermore, the experimental results revealed separation behavior of MO. As and Sb were evaporated into the gaseous phase to facilitate their separation from other substances at 773 K. Pb and Bi behavior were similar to them at 823 K, As, Sb, Pb and Bi to enter the gaseous phase for the purpose of separation with Ag, Au, and Cu. By exploiting the differences of gasification specificity, it is possible to separate Ag, Au, Cu, and other elements at 1173 K, finally leading to the formation of Ag–Au–Cu alloys.

Techno-Economic Potential of a Polygeneration System Integrated with Conventional or Hybrid Solar Dual Fluidized Bed Gasification Technology in an Australian Sugar Mill

Techno-Economic Potential of a Polygeneration System Integrated with Conventional or Hybrid Solar Dual Fluidized Bed Gasification Technology in an Australian Sugar Mill

Effects of critical structure parameters on conversion performance enhancement of a Pd–Rh dual-carrier catalytic converter for heavy-duty natural gas engines

In this work, the effects of structure parameters on the conversion performance of the dual-carrier catalytic converter for heavy-duty natural gas engines are investigated. A three-dimensional numerical model adopting an empirical global reaction mechanism for the Pd–Rh dual-carrier catalytic converter is established. The results show that the conversion efficiency slightly increase with the increase of the carrier cell density ratio, the maximum conversion efficiency differences of CH4, CO and NO are 5.7 %, 8.3 % and 7.9 %, respectively. When the carrier wall thickness decreases from 0.24 mm to 0.10 mm, the conversion efficiencies of CH4, CO and NO slightly increase, and the maximum differences are 5.5 %, 8.0 % and 8.0 %, respectively. Additionally, the fuzzy grey relational analysis (FGRA) is employed to make a comprehensive evaluation. For the conversion efficiencies of CH4 and NO, the primary and secondary relationships of the influence factors are carrier diameter > carrier length > carrier cell density ratio > carrier wall thickness. The orthogonal experiment analysis indicates that case 7 shows the best total conversion performance (CH4: 91.9 %; CO: 99.7 %; NO: 83.9 %) at 673K. Compared with the baseline case 2, the conversion efficiencies of CH4 and NO are increased by 14 % and 19.9 %, while the volume increased by 36.1 %.

Quantitative analysis of the relationship between charge motion and knocking combustion in spark-ignition natural-gas engines under critical knocking conditions

Increasing the in-cylinder flow intensity is considered to have the potential to restrain engine knock and improve thermal efficiency. However, the effect of charge motion on the knocking combustion in natural gas (NG) engines is unclear. Therefore, swirl, tumble, and squish motions of different intensities were organized by changing the shape of the combustion chamber and initializing the in-cylinder flow velocity. Subsequently, the effect of charge motion on the knocking combustion of a spark-ignition NG engine under critical knocking conditions was investigated via numerical simulations. The results indicate that the knock intensity (KI) first increases and then decreases with an increase in swirl and tumble intensities and linearly increases with an increase in squish intensity. Swirl had the smallest impact on KI, followed by tumble, whereas squish had the greatest impact. The differences in flame propagation resulted in differences in KI under different charge motion patterns. The obvious non-uniformity of the radial and axial flame propagation is a potential cause of the significant increase in KI. Therefore, while increasing the flow intensity, matching a suitable combustion chamber to make the flame propagation more uniform helps achieve anti-knock and rapid combustion. Improving the swirl and tumble intensities can help NG engines achieve anti-knock and rapid combustion, whereas improving the squish intensity does not. This study provides an important reference for determining whether increasing flow intensity can improve NG engines’ knock characteristics and combustion performance.

Evaluation of fatigue life prediction models and investigation of fracture mechanisms of mild steel

Fatigue is one of the dilemmas of coiled tubing (CT) in oil and gas engineering. This study investigated the fatigue behavior of CT employing mild steel, which is commonly utilized in the CT110. Two fatigue life prediction methods based on cyclic strain-life principles, the Manson–Coffin and Landgraf models, as well as the Smith and Ellyin models based on energy-life principles, were evaluated. The Ellyin model demonstrated superior accuracy in predicting the low-cycle fatigue life of CT110, displaying dispersion within the 1.5 scatter band. This research integrated mechanical property analysis and microscopic deformation assessments for CT110. Fatigue mechanics studies show cyclic softening behavior in the CT110 of mild steel. The results of the microscopic analysis show that the fatigue fracture of CT110 has typical fatigue striations and equiaxial dimples as a plastic fracture. Combined with TEM and EBSD analysis, fatigue deformation increases grain deformation and dislocation density. In addition, the increase in dislocation density results from the combination of cycles and strain amplitude. The results of in situ EBSD further support this view. At 8% strain amplitude, the dislocation density increases to 0.196B when the cycle increases from 0 number to 10 number. Furthermore, the ferrite grain slip becomes accessible, but the 〈111〉 // Z0 direction is still the main texture. These are fundamental reasons for the cyclic softening of the CT110 mild steel, supported by a decrease in stress amplitude.

Hydrogen Comes in from The Cold

While electric vehicles have long been seen as the best alternative to gas and diesel engines, momentum is growing behind the use of hydrogen as an increasingly viable clean energy source. World Pumps looks at how liquid hydrogen pumps are playing a critical role in this fuel of the future

CALCULATION OF WEAR VELOCITY IN PROFILE PART OF CAM

In the article, taking into account the increasing wear of the profile, the intensity of wear of the surface of the cam in contact with talc during operation is studied, and the change in this intensity depending on the pressure angle is estimated. The effect of chamber profile wear on the gas distribution mechanism (GDM) and engine operation has been studied. the possibility ofa significant improvement in the tribological properties of a cam-pusher pair is analyzed on the basis of a numerical method for formulating the law of motion of the pusher.

Research on the underground ignition mechanism of ignition fuel and ground simulation experiments

Abstract In the increasingly severe environment of the “dual carbon” situation and the urgent objective demand for national energy transformation and upgrading, the development and use of clean energy have become a new research field and direction. Underground coal gasification technology (UCG) is a clean coal technology that completely bypasses the traditional coal combustion process by converting coal underground into gas and then classifying and recycling it. This method removes sulfur before fuel combustion Nitrogen compounds and particles make it clean like natural gas. The most commonly used ignition method in this technology is chemical ignition. A certain proportion of ignition fuel and main fuel is injected into the underground through pipelines, and then combustion supporting gas is introduced to cause a chemical reaction and generate an open flame to ignite the coal. However, due to the complex internal environment of the pipeline, uneven bending of the pipeline column, and the length of the pipeline exceeding one kilometer, the concentration threshold of the ignition fuel when it reaches the underground igniter cannot be accurately controlled, resulting in ignition failure. In response to the above difficulties, this article has conducted research on the ignition mechanism of ignition fuel, and developed a dedicated ground simulation test bench to conduct ground simulation experiments. The research has strong support for the on-site pilot testing and engineering services of underground coal gasification technology.

Decelerating catalyst aging of natural gas engines using organic Rankine cycle under road conditions

High exhaust temperature is an intrinsic nature of natural gas engines which underlies power de-rating and thermal aging of after-treatment system; therefore, this study integrates an organic Rankine cycle (ORC) system between engine and it's three-way catalyst (TWC) to address these challenges. ORC facilitates power output enhancement through exhaust energy recovery and alleviates thermal aging by reducing exhaust temperature. To estimate the effectiveness of this hypothesized system, a simulation-based investigation is performed. First, simulation models, including engine, TWC, and vehicle dynamic models, are built and validated by experimental data. According to the temperature characteristics of different TWCs, three scenarios, representing old, current, and prospective TWC technology, are formulated to estimate the ORC performance under Worldwide Harmonized Light Vehicles Test Cycle. Results show that ORC system can substantially alleviate the thermal damage caused by high exhaust temperature and extend TWC lifespan. It is estimated that over 98.5 % of thermal damage can be decreased by proper ORC setting, and the average TWC lifespan extension can be at least 55.4, making a reduced noble metal usage and cost of TWC. Meanwhile, with the decrease of the working temperature of TWC, ORC can recover exhaust energy under more road conditions, further improving the net power and shortening the payback period of extra ORC hardware costs. A reduction in the working temperature of TWC from 770.5 K to 618 K yields a 109 % enhancement in maximum power, coupled with a 62.30 % reduction in the payback period. These findings fully reflect the advantage of ORC-TWC coupling and indicate that ORC is supposed to be used more for the TWC with a low working temperature to maximize economic effectiveness. This study provides a novel pathway for thermal aging alleviation of TWC and a valuable reference for prospective studies on matching ORC with TWC under road conditions.

Analysis of the technical and economic aspects of gas engine heat pumps in various climates in Iran

Due to the scarcity of fossil fuels and the potential for energy shortages, the use of energy-efficient devices is of utmost importance. There is an increasing trend in the utilization of heat pumps in air conditioning systems (heating/cooling) for both residential and commercial buildings. This article focuses on the analysis of the technical and economic aspects of gas engine heat pumps (GEHP) in various climates throughout Iran. The evaluation of this article revolves around two perspectives: that of the consumers and the government. The implementation of GEHP has been carefully considered from the consumers' perspective to ensure it does not have any negative effects on them. Additionally, from the government's point of view, the available resources are considered, and the supply of electricity and gas, along with their cost and energy consumption, are thoroughly investigated by the Ministries of Energy and Petroleum. The findings indicate that, from the consumers' perspective, the economic efficiency of GEHP can be up to 11 times higher than that of electric heat pumps (EHP). Moreover, from the government's viewpoint, GEHP leads to a reduction of over 92 % in electricity consumption, 5 % in gas consumption, and 92 % in annual expenses for the Ministry of Energy. Furthermore, the implementation of GEHP increases the income of the Ministry of Petroleum by 9.8 times.

Theoretical and experimental study on total heat recovery of condensing gas boiler flue gas by gas engine-driven compression heat pump

How to improve the utilization efficiency of natural gas and achieve the goal of carbon reduction has gradually become the focus of people’s attention. The exhaust temperature of the condensing gas boiler is between 50℃ and 80℃, which still contains some heat that is not used, so it is necessary to recover this part of the heat. This paper mainly studies the total heat recovery and utilization of waste heat from low-temperature flue gas of condensing gas boiler. In the research field of gas boiler flue gas waste heat recovery, the use of gas compression heat pump to recover gas boiler flue gas waste heat is still very few. Based on the principle of reducing the cold source temperature, a low-temperature flue gas recovery scheme of a gas engine-driven compression heat pump coupled condensing gas boiler is proposed. The low-temperature chilled water produced by gas engine-driven compression heat pump is used to recover flue gas waste heat from condensing gas boiler and gas engine, which can improve the utilization efficiency of natural gas and eliminate the “white smoke phenomenon” simultaneously. In addition, the waste heat of flue gas is used as the low-temperature heat source of gas engine-driven compression heat pump to ensure the stable operation of the heat pump in the low-temperature environment. The flue gas waste heat recovery technology has been improved compared with other flue gas waste heat recovery technologies in terms of primary energy utilization efficiency, system stability, corrosion resistance of flue gas heat exchangers, and investment recovery cycle. The experimental results show that when the water inlet temperature of the flue gas heat exchanger is 15℃, the overall power of the unit can reach 645 kW, and the final exhaust temperature is below 25℃. The overall primary energy utilization rate of the GEHP&CB can reach 110 %, which is 10 %∼20 % higher than that of the condensing gas boiler. The payback period of the increased initial investment is 1.4 heating seasons. Due to the improvement of natural gas utilization efficiency significantly reduces natural gas consumption and pollutant discharge.

Performance analysis of combining solid oxide electrolysis cell hydrogen production and marine hydrogen compressed natural gas engine system

Natural gas holds promise as an alternative energy source for ships, and its combustion blended with hydrogen can achieve better beneficial of energy saving and emission reduction. Nevertheless, the current challenges in hydrogen, characterized by its high cost and difficulties in storage and transportation, hinder its application in maritime technology. To address the issue, this study proposes a system that integrates a marine hydrogen compressed natural gas (HCNG) engine, a supercritical carbon dioxide Brayton cycle (SCBC), and a solid oxide electrolysis cell (SOEC). In this system, SCBC is capable of recovering waste heat for electricity generation, while SOEC serves as an energy storage device to adjust engine load and enhance fuel economy. The generated hydrogen can be utilized as a source of hydrogen in HCNG fuel, thereby improving engine performance and reducing pollutant emissions. Various system numerical simulation schemes with different engine hydrogen volume fractions were studied. The results show that the electrical efficiency of SOEC is improved by 17.86% by heating the feed stream with engine exhaust gas. In addition, the hydrogen fraction in which SOEC can act as a complete hydrogen source ranges from 30% to 40%. The results of the sensitivity analysis show that the cycle efficiency reaches a peak of 31.5% at a compressor outlet pressure of 16 MPa, while the efficiency of the whole system reaches a maximum of 50.8% at 21 MPa. The optimal operating temperature for the SOEC falls within the range of 650–700 °C for the 30, 40 HCNG schemes, and between 750 and 800 °C for the 50, 60 HCNG schemes.

A new modelling approach for in-situ hydrogen production from heavy oil reservoirs: Sensitivity analysis and process mechanisms

The increasing demand for eco-friendly and renewable energy has positioned hydrogen as a viable solution for global energy and environmental challenges. In-situ combustion gasification of heavy oil reservoirs offers potential for large-scale hydrogen production, injecting steam and air (or alternative gases) to trigger complex chemical reactions leading to hydrogen and syngas generation. However, a research gap exists due to the lack of a comprehensive numerical model for accurately simulating hydrogen production under SARA-based (saturate, aromatic, resin, asphaltene) hydrocarbon characterization in experiments and field study. This study addresses the gap by investigating in-situ combustion gasification for hydrogen generation in heavy oil reservoirs. A novel model based on SARA characterization is proposed, showing fidelity with experimental and numerical results. Different injection strategies, like pure oxygen and CO2, impact hydrogen production. Oxygen injection yields less hydrogen than air injection, highlighting the importance of oxygen control. CO2 injection reduces hydrogen but aids carbon management. The oxygen to nitrogen ratio (61/39) demonstrates the highest hydrogen-to-syngas ratio. Practical implementation requires economic feasibility, operational practicality, safety, and environmental considerations. This study advances in-situ combustion gasification technology, facilitating efficient and sustainable hydrogen generation from heavy oil reservoirs.