Gas Throttling Research Articles

Numerical Simulation of Secondary Hydrate Formation Characteristics and Effectiveness of Prevention Methods

The exploitation of natural gas hydrates by the pressure reduction method is affected by the decomposition heat absorption effect, and the range of the formation temperature reduction area is expanding. At the same time, the temperature reduction phenomenon is more significant around the production wells under the influence of gas throttling and expansion effects, and hydrate formation will occur under certain temperature and pressure conditions, leading to blockage of effective seepage channels in the reservoir in the region and elevation of seepage resistance, which may affect the output of hydrate decomposition gas. A numerical simulation model is constructed for the purpose of studying the secondary hydrate generation pattern around the well, analyzing the impact of secondary hydrates around wells on the production capacity, and assessing the effectiveness of prevention methods to inform the actual production of hydrates. The results demonstrate that secondary hydrate is typically formed in the near-well area of the upper part of the production well, and the secondary hydrate around the upper part of the production well is the first to be formed, exhibiting the highest saturation peak and the latest decomposition. The formation of the secondary hydrate can be predicted based on the observed change in temperature and pressure, and the rate of secondary hydrate formation is markedly rapid, whereas the decomposition rate, approximately 0.285 mole/d, is relatively slow. Additionally, the impact of secondary hydrates on cumulative gas production is insignificant, and the effect of secondary hydrates on capacity can be ignored. Hot water injection, wellbore heating, and reservoir reconstruction can effectively eliminate secondary hydrates around the well. Reservoir reconstruction represents a superior approach to the elimination of secondary hydrates, which can effectively enhance production capacity while preventing the generation of secondary hydrates.

Mixing Enhancement Mechanism of Liquid Jet in Supersonic Crossflow with Gas Throttling

Numerical and experimental studies were conducted to uncover the physical aspects of a liquid jet injected into a supersonic crossflow with gas throttling systematically. The results were obtained with the inflow conditions of a Mach number of 2.0, a total temperature of 300 K, and a total pressure of 0.55 MPa. The results show that fuel–air mixing is considerably enhanced due to shock-induced flow distortion by adding gas throttling. The strength of downstream backpressure determines the distance of forward movement of the throttling shock wave train and the flowfield structure in the channel. When the mass flux of gas throttling is high, the influence of throttling gas spreads across the expansion section, resulting in significant flow separation in front of the liquid jet. It is found that the spray flashback phenomenon is similar to the flame flashback phenomenon that occurs in the supersonic combustion process under the action of a precombustion shock train. The wall counterrotating vortex pair and induced cavity streamwise vortices are enhanced with the increase of the flux of gas throttling. The relatively high-pressure environment generated by gas throttling promotes the atomization of droplets. As a result, the mixing enhancement mechanism of a liquid jet in a supersonic crossflow with gas throttling is mainly due to the combined effects of 1) the shock waves separating the side wall boundary layer and modifying the local flow state of air in the combustor, which lead to a dramatic increase in fuel–air mixing, and 2) the streamwise vorticity values as well as the residence time resulting from channel blockage elevating.

Analysis of methods for improving the efficiency of “Iceberg” gas air coolers

Russia has the largest volume of natural gas reserves in the world. Recoverable natural gas reserves amount to about 67 trillion cubic meters, according to the Ministry of Natural Resources and Environment of the Russian Federation for 2023. In recent years, the development of the Unified Gas Supply System has been growing rapidly. Since 2021 the Government of the Russian Federation has been actively introducing draft laws and regulations related to the scaling of the country’s gasification. In June 2021 came out the Federal Law No. 184-FZ, which instructed the Government of the Russian Federation to adopt regulations aimed at implementation of provisions of free gasification of the country [1]. In September 2021 there was issued Decree No. 1547, [2] approving the new Rules for connecting gas-using equipment and capital construction facilities to gas distribution networks, which introduces the concept of pre-gasification. It is worth noting that new gas mains, compressor stations (CS) are put into operation, active reconstruction of the existing shops with exhausted gas compressor units (GCU) is carried out. One of the most urgent issues of the gas industry today is the efficient use of energy resources. Besides using the energy of flue gases from gas turbine drive of GPA, energy at gas throttling at gas distribution stations and other methods of energy saving, the significant role is played by the effective operation of air coolers of gas (ACG), the operation of which affects the reliable transportation of gas in the main gas pipeline (MG). The paper analyzes the methods of technical condition of gas air cooling devices of “Iceberg” type operated at the production site of the booster compressor station of “Gazprom Dobycha Nadym” LLC. The thermal efficiency of air coolers with all fans turned on and off was determined for the coldest and hottest months of the year. The electric energy savings of the frequency controlled drive (VFD) were calculated.

Performance prediction of a distributed Joule-Thomson effect cooler with pillars

• Heat transfer and throttling coupling is used to replace the traditional constant enthalpy throttling. • The performance of the J-T cooler is predicted by simulation. • A novel J-T cooler with multi-layer, multi-pillar micro-channels was designed. Hampson type Joule-Thomson (J-T) throttle coolers are widely used for cooling infrared detectors and many electronic components. The conventional J-T throttle coolers are not compact, with low heat transfer efficiency and small cooling capacity. In this paper, a stacked column cluster type microchannel distributed J-T throttle cooler is designed through combining a compact microchannel etched and shaped by photolithography and an atomic diffusion fusion welding process with a J-T throttle cooler. The dimensions of the cooler are 10 mm for the inlet section, 145 mm for the throttling and heat exchange section,10 mm for the expansion chamber, with 6 layers staggered high pressure channels and 6 low pressure channels. The cooling performance of the cooler under various low-temperature and high-pressure operating conditions were studied through simulations, and the results showed that the cold-end temperatures were 158.0, 147.9, 146.1, 144.1, and 141.1 K for an inlet pressure of 5.20 MPa and inlet temperatures of 280.0, 270.0, 260.0, 250.0, and 240.0 K, respectively, with argon as the work gas. The cold-end temperatures were 163.6, 159.4, 156.8, 154.6, and 152.7 K for an inlet pressure of 5.60, 6.00, 6.40, 6.80, and 7.20 MPa respectively in 288.0 K inlet temperature. In the process of working medium flow and heat transfer in the microcolumn group channel of the cooler, the temperature and pressure change significantly. When the working medium in the flow reaches the phase change state, that is, the phase change temperature and pressure reach, due to the gas liquefies and the flow rate drops, the working medium loses the gas throttling refrigeration effect, and the temperature no longer decreases significantly, and the refrigeration temperature is limited by this. In addition, compared with different inlet pressures, when the inlet temperature is 280.0 K, the 5.20 MPa nitrogen throttling refrigeration temperature is close to the argon gas at 2.98 MPa, which are 223.4 K and 234.9 K, respectively. Therefore, high pressure nitrogen can be considered to replace low pressure argon in engineering applications. In view of the problems involved in the research process of traditional micro-channel throttling coolers, the innovative solutions are put forward in this paper, which can bring new innovations and thoughts for the future research and application of such problems.

Numerical study on the condensation characteristics of natural gas in the throttle valve

Due to the cooling effect of natural gas throttling, spontaneous condensation will occur in the throttle valve, which may affect pipeline system efficiency. However, the condensation characteristics (such as nucleation rate and condensation rate) remain unclear, and the traditional method based on the isenthalpic hypothesis can hardly solve this non-equilibrium issue. Based on the geometry differences between the throttle valve and the Laval nozzle, this paper explored the condensation parameters of the CH4–C2H6 binary mixture in the throttle valve and the Laval nozzle using CFD techniques (solving non-equilibrium condensation at a lower cost). This paper discussed the influence of the inlet pressure and inlet temperature on the spontaneous condensation process in the throttle valve as well. The findings are that the nucleation and droplet growth regions in the throttle valve are closer to the throat but narrower than that of the Laval nozzle, and the liquid mass fraction decreases after reaching the peak value. The onset of droplet nucleation and droplet growth is closer to the throat when increases inlet pressure or decreases inlet temperature. The condensation rate of ethane in the throttle valve is lower than that in the Laval nozzle, and the sensitivity of the nucleation rate and the Wilson point to the inlet parameters is higher and lower than that in the Laval nozzle, respectively.. The main innovation of the paper lies in revealing the differences in the condensation between the throttle valve and the Laval nozzle using the non-equilibrium method.

Research on modeling method of porous air bearing materials based on random particles

The porous air bearing materials enable the gas throttling effect through internal pore structures. The simulation modeling of the pore structure is the prerequisite for researching the gas flow state and the bearing air film stiffness parameters. Aiming to solve the distortion problems of a single pore structure and simplified boundary conditions in the current porous material modeling process, a filling model generated via random spherical particles was proposed. Based on the normal distribution of particle diameter as well as the random position distribution, the model was used to simulate the real pore structure of porous restrictor. Along with the composite modeling DIGIMAT software, the 3D model with micro-hardness simulation was generated using ABAQUS software. The feasibility of the random filling modeling method was verified by comparing the simulation results with those obtained through hardness experiments. Hence, a reference for the modeling of high-density porous materials was provided for studying the lubricating medium flow state and material cutting mechanism in porous materials.

ИССЛЕДОВАНИЕ РЕЖИМОВ РАБОТЫ СХЕМ С ДЕТАНДЕР-ГЕНЕРАТОРНЫМИ АГРЕГАТАМИ НА КОГЕНЕРАЦИОННЫХ КОТЕЛЬНЫХ С ГАЗОПОРШНЕВЫМИ ДВИГАТЕЛЯМИ ВНУТРЕННЕГО СГОРАНИЯ

In this mode, due to a decrease in the pressure drop used in the expander, useful effect has been shown to decrease. The paper considers the operating modes of various schemes for the use of expander-generator units in cogeneration boilers with gas-piston internal combustion engines. In the scheme with the absence of gas heating before the expander at low air temperatures, crystallohydrates may fall out after the expander. In order to prevent this pheno­menon, a mode with gas throttling after the expander is proposed. In this mode, due to a decrease in the pressure drop used in the expander, its useful effect will decrease. The study also shows that the scheme with gas heating in front of the expander enables the available pressure drop to be fully realised. At a certain outdoor air temperature in the summer, the use of gas heating may become unprofitable due to a decrease in the efficiency of internal combustion engines for a heated circuit. At higher outdoor temperatures, the study proposes a mode with gas heating turned off. Annual and average monthly fuel economy from the use of various schemes of expander-generator units for a cogeneration boiler house in comparison with the scheme with drosseling is calculated. It is shown that heating the gas before the expander to 100 °С allows annual fuel economy to be increased by about 1.4 times, when compared to a scheme using an expander without heating.

Organization of Six-Cylinder Tractor Diesel Working Process

The purpose of the work is to consider the organization of the working process of six-cylinder diesel engines with a power of 116 and 156 kW and exhaust gas recirculation. The following systems and components were used in the experimental configurations of the engine: Common Rail BOSСH accumulator fuel injection system with an injection pressure of 140 MPa, equipped with electro-hydraulic injectors with seven-hole nozzle and a 500 mm3 hydraulic flow; direct fuel injection system with MOTORPAL fuel pump with a maximum injection pressure of 100 MPa, equipped with MOTORPAL and AZPI five-hole nozzle injectors; two combustion chambers with volumes of 55 and 56 cm3 and bowl diameters of 55.0 and 67.5 mm, respectively; cylinder heads providing a 3.0–4.0 swirl ratio for Common Rail system, 3.5–4.5 for mechanical injection system. The recirculation rate was set by gas throttling before the turbine using a rotary valve of an original design. The tests have been conducted at characteristic points of the NRSC cycle: minimum idle speed 800 rpm, maximum torque speed 1600 rpm, rated power speed 2100 rpm. It has been established that it is possible to achieve the standards of emissions of harmful substances: on the 116 kW diesel engine using of direct-action fuel equipment and a semi-open combustion chamber; on the 156 kW diesel using Common Rail fuel supply system of the Low Cost type and an open combustion chamber.

Organization of the Six-Cylinder Tractor Diesel Working Process

The purpose of the work is the organization of the six-cylinder diesel engines (with a power of 116 and 156 kW) working process with exhaust gas recirculation. The following systems and components were used in the experimental configuration of the engine: Common Rail BOSСH accumulator fuel injection system with an injection pressure of 140 MPa equipped with electro-hydraulic injectors with 7-hole nozzle and a 500 mm3 hydraulic flow; direct fuel injection system with MOTORPAL fuel pump with a maximum injection pressure of 100 MPa, equipped with MOTORPAL and AZPI five-hole nozzle injectors; two combustion chambers with volumes of 55 and 56 cm3 and bowl diameters of 55 and 67.5 mm; cylinder heads providing a 3-4 swirl ratio for Common Rail system, 3.5-4.5 for mechanical injection system; recirculation rate was set by gas throttling before the turbine using original design rotary valve. The tests were conducted at characteristic points of the NRSC cycle: minimum idle speed 800 rpm, maximum torque speed 1600 rpm, rated power speed 2100 rpm. It is established: achievement of emission standards for the 116 kW diesel engine is possible with the use of direct-acting fuel equipment and a semi-open combustion chamber; on the 156 kW diesel - using the Low Cost type common Rail fuel supply system and an open combustion chamber.

The effects of cell density and intrinsic porosity on structural properties and adsorption kinetics in 3D-printed zeolite monoliths

Herein, we report the evaluation of dynamic performance of 3D-printed zeolite monoliths for CO2/N2 separation at 5 bar 25 °C. Monoliths with various cell densities (200, 400, 600 cpsi) and porosities (0.23–0.46) were printed and the effects of cell density, wall porosity, and inlet gas velocity on their separation performance were investigated. Dynamic breakthrough tests with 10% CO2/N2 revealed that increasing cell density gives rise to gas throttling, inadequate time for molecular mass transfer, and broad wavefronts. For 200 cpsi monoliths, upon increasing wall porosity from 0.23 to 0.46, the mass transfer zone (MTZ) length decreased from 0.40 cm to 0.07 cm at the feed velocity of 1.8 cm/s. The mass transfer coefficients estimated from modeling the breakthrough profiles were found to decrease steadily with both velocity and monolith cell density. In the macroporous samples, the best mass transfer coefficient was found to be 0.049 s−1 for the 200 cpsi monolith with kaolin binder substitution. Both increasing the plasticizer concentration and substituting a macroporous binder promoted mass transfer rate, however, the former method increased the number of zeolite-bentonite bonds around large surface defects during burnout and reduced the CO2 adsorption capacity by 27% from the other formulations. On the basis of adsorption capacity and kinetics, utilization of a macroporous binder was found to be the best method of developing 3D-printed zeolite monoliths because it could reduce intraparticle resistance without compromising adsorption capacity or mechanical integrity.

Analysis of the Efficiency of Circuits using Natural Gas Additional Energy Potentials on Cogenerating Boiler Houses with Internal Combustion Engines

The article studies the energy efficiency of various circuits using the energy of natural gas excessive pressure in expander-generator units installed before gas reciprocating engines in cogeneration boiler houses. The circuits with and without gas heating before the expander are considered. As an energy effect from the expander use at the cogeneration boiler house fuel economy is taken as compared with the circuits with gas throttling with constant production schedules of electrical and thermal power. The dependence on specific fuel economy determination is obtained. For the circuits being compared, the areas of the energy effect magnitude dependence on the outside temperature are allocated. It is shown that the circuit with heated gas before the expander will have the greatest energy effect at the outside air temperature up to the value corresponding to the equal values of specific fuel economy for the considered circuits and with disconnection of gas heating at higher air temperatures. The method proposed in the paper can be used to calculate the energy effect from various circuits of the expander application in cogeneration boiler houses with internal combustion engine both in exisiting ones and the ones which are under design.

SOME ASPECTS OF PREVENTION OF CRYSTALLINE HYDRATES FORMATION AT GAS DISTRIBUTION STATIONS

The existing methods for natural gas dehydration both in fields and at compressor stations cannot always provide standatdized values of natural gas dehydration. The analysis of operation of gas distribution systems shows that dehydration units are improperly placed and are often installed out of condensation and freezing zones. This is due to the lack of consideration of phase transitions impact in gas throttling on its temperature condition. Due to insufficient natural gas dehydration, crystalline hydrates can be formed on wellbores, distribution lines and main gas pipelines and at its reduction, disturbing the operation of the equipment of compressor stations, gas distribution stations, deranging instrumentation and automation. The issues of reliability of gas pipeline systems considering the formation of crystalline hydrate plugs in pipelines have been studied. The analysis of the methods and devices preventing hydrates formation and eliminating existing crystalline hydrate plugs has shown that to provide normalized parameters of the transported gas it is necessary to perform additional water vapor, condensate drops and crystalline hydrate particles removal from natural gas at gas distribution stations during winter months. Currently applied methods used to deal with crystalline hydrate plugs in main gas pipelines require significant expenses and do not effectively ensure the reliability of pipelines operation. An energy-efficient design of an integrated treatment unit which provides an additional natural gas treatment at GDS, increases the reliability of gas pipelines protection against hydrate blockage and improves the efficiency of gas supply systems as a whole have been proposed at the Department of Heat and Gas Supply and Ventilation of the SWSU.

Optimal piston speed ratio analyses for irreversible Carnot refrigerator and heat pump using finite time thermodynamics, finite speed thermodynamics and direct method

AbstractAn irreversible Carnot refrigeration and heat pump cycle model with external irreversibilities caused by finite rate of heat transfer, heat leakage from heat sink to heat source and internal irreversibilities caused by finite piston speed, friction and gas throttling is established by using the combination of finite time thermodynamics, finite speed thermodynamics and direct method. Different from the model of constant speed of the piston on the four branches, the piston speeds on the four branches in this model are assumed to be unequal. Expressions of cooling load and coefficient of performance (COP) of the Carnot refrigeration cycle as well as heating load and COP of the heat pump cycle are derived for a fixed cycle period. Numerical examples show that the curves of COP versus cooling load and COP versus heating load are parabolic like ones, and there exist optimal finite piston speed ratios on the four branches, which lead to the maximum COPs. Moreover, the effects of the heat leakage coeffici...

Optimum thermodynamic conditions for upper pressure limits of transcritical carbon dioxide refrigeration cycle

It is well known that the choice of upper pressure limit in a transcritical CO 2 refrigeration cycle is independent of the gas cooler approach temperature. This is in contrast to sub-critical cycles, where the condensing pressure is invariably governed by the ambient conditions. The criteria used for limiting the upper pressure limit in a transcritical cycle are the state of maximum COP for a given set of evaporating and gas cooler exit temperatures. The latter is governed by the local ambient conditions and the possible approach. This paper provides a thermodynamic basis for the evaluation of this pressure for the case of ideal compression and with some compressors available in the market. In addition, it also provides an additional criterion that minimizes the cycle irreversibility which is predominantly due to gas throttling. This paper evaluates the pressure limits for these two criteria for some typical evaporating temperatures and ambient conditions. The possible compressor discharge temperatures in each case are calculated and criteria for two-stage compression are identified.

Capacity Control for Refrigeration and Air-Conditioning Systems: A Comparative Study

The capacity control of a vapor-compression refrigeration system is investigated for three different capacity control schemes. In a hot-gas by-pass control scheme, the refrigerant is by-passed from the compressor and injected back into the suction line to decrease the cooling capacity, whereas in cylinder-unloading scheme, one or more cylinders are unloaded to decrease the refrigerant mass flow rate in the system, which decreases the cooling capacity. However, in suction gas throttling, the suction gas throttled at the inlet of the compressor, decreases the refrigerant mass flow rate, and hence a corresponding decrease in the system capacity. These schemes are investigated for HFC-134a by considering finite size of the components that are used in the refrigeration systems. The models consider the finite-temperature difference in the heat exchangers, thus allowing the variations in the condenser and evaporator temperatures with respect to capacity and external fluid inlet temperatures. A comparative study is performed among these schemes in terms of the system coefficient of performance (COP), the operating temperatures, and percentage of refrigerant mass fraction as a function of the percentage of full-load system capacity.

A Numerical Investigation of the Cooling Effect of Compressed Natural Gas Throttling on Engine Delivery Ratio

A theoretical study was conducted to investigate the cooling effect of throttling compressed natural gas during the pressure regulation process. The concept of using this effect in cooling down the induction air was investigated. A thermodynamic model was developed for a typical fuel delivery system used on a vehicle fueled with compressed natural gas. The model was based on a set of integral conservation laws applied to each component of the fueling system. Several heat exchanging arrangements between the throttled gas and the inlet air were examined. The effect of the added heat exchanger on engine delivery ratio was examined for different engine sizes as well as for different operating conditions. An increase of 1 to 2.5% in engine delivery ratio was predicted due to the added heat exchanger.

Approximate account of double gas throttling in the pressurization openings of gas bearings

Approximate account of double gas throttling in the pressurization openings of gas bearings

Drop condensation and coagulation during gas throttling

The authors investigate the formation and growth of droplets during throttling of a gas mixture. They take account of coagulation of droplets and also interphase mass transfer. The parameters at the throttle exit are determined, from which one can estimate the droplet growth rate in the tube behind the throttle.