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The present article proposes to apply a Risk-Based Maintenance methodology in a gas compression system. This risk calculation is based on a semi-quantitative mathematical model that uses the interdependence of process variables and predictive maintenance data applied in a Condition-Based Maintenance methodology, in order to obtain the calculation of the dynamic risk. This promotes a review of maintenance and reliability strategies proactively in real time. The dynamic risk applied to the system involves the interface of predictive maintenance and process variables with the reliability and risk analyses of the system. This value, which is associated with the financial aspects, safety, people and environment, can be compared to the tolerable risk of production plant operation, providing operation or maintenance decisions. An example demonstrates the integration of process and maintenance data using this model methodology for a gas compression system. This framework can be applied to evaluate the integrity of systems, providing critical risk-based information for the maintenance and operation teams, assisting then in the mitigation of failures in the production systems. [ABSTRACT FROM AUTHOR]

Multi-Skill Manpower Constrained Project Scheduling Problem suggested with alternative Activity Chains for gas compressor station commissioning and Start-up project to select one alternative activity chain from each alternative set, schedule selected activities, and allocating multi-skill manpower to these activities. Li's two-phase approach is used to convert the model into crisp single objective problem. Also, a meta-heuristic based on the Genetic Algorithm is developed for a large scale. Results derived from the solved model reply efficiently employer's objectives and employees' preferences based on minimum delay in project completion time and minimum deviation of working days determined at the beginning of planning. [ABSTRACT FROM AUTHOR]

Rapid identification of anomalous methane sources in oil/gas fields could enable corrective action to fight climate change. The GHGSat‐D satellite instrument measuring atmospheric methane with 50‐meter spatial resolution was launched in 2016 to demonstrate space‐based monitoring of methane point sources. Here we report the GHGSat‐D discovery of an anomalously large, persistent methane source (10–43 metric tons per hour, detected in over 50% of observations) at a gas compressor station in Central Asia, together with additional sources (4–32 metric tons per hour) nearby. The TROPOMI satellite instrument confirms the magnitude of these large emissions going back to at least November 2017. We estimate that these sources released 142 ± 34 metric kilotons of methane to the atmosphere from February 2018 through January 2019, comparable to the 4‐month total emission from the well‐documented Aliso Canyon blowout. Plain Language Summary: Methane is a potent greenhouse gas that is emitted from a variety of natural processes and human activities. Reducing methane emissions from oil/gas production and transmission facilities is considered to be one of the most immediately actionable ways to abate climate change, because the captured methane can be sold. Studies of U.S. oil/gas fields have shown that a small number of high‐emitting facilities are responsible for the bulk of the total emission from oil/gas operations. So far, the only way to identify and quantify these sources has been through field studies involving aircraft and ground‐based observations, but these are expensive, and much of the world cannot be observed in this way. Here we use satellite instruments to identify and quantify anomalously large point sources from an oil/gas field in Central Asia. Our work shows how satellite instruments can be used to monitor methane emissions from individual point sources across the world. It points to an observing strategy where instruments with global coverage at coarse spatial resolution can first identify methane hot spots and then instruments with fine spatial resolution but limited coverage can zoom in to identify the facilities responsible for the hot spots. Key Points: The GHGSat‐D satellite instrument with 50‐m resolution discovered very large methane point sources from oil/gas production in Central AsiaThese large emissions were confirmed by the TROPOMI satellite instrument and extended over at least a yearPersistently large emissions from a gas compressor station (10–43 t hr−1 in >50% of observations) were observed over an 11‐month period [ABSTRACT FROM AUTHOR]

A gas compressor station only had its about 35% design processing capacity as a result of the abnormal piping vibrations on the inlet pipelines. Characterization, diagnostics, analysis, and elimination of piping vibration were performed. The root causes and sources of the abnormal vibration were investigated by on-site measurements and analysis of vibration and pulsation under various load conditions of compressors. The results revealed that it was not mechanical resonance, but the high pressure pulsation and acoustic resonance occurred on the inlet pipelines, which resulted in the severe vibration. Three different modification models against vibration were proposed by shortening the length of the pipe to avoid acoustic resonance, enlarging the volume of the gathering manifold to buffer pressure pulsation, and adding supports to increase the stiffness. A better modification model was applied by performing modal analysis and fluid-structure interaction (FSI) vibration analysis using the finite element method. The effect of countermeasures was evaluated by vibration and pulsation measurements during operation after modifications, which results showed the level of piping vibration and pressure pulsation was within the allowable limits. The processing capacity of the gas station has reached its design requirement as a result of the desired reduction in vibrations. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Natural Gas (NG) is constantly increasing its importance and widening its penetration in the world energy mix, so that the topic of its reliable and efficient transportation represents an enduring challenge of utmost importance. Within this framework, the design and operation of NG compression stations is a key aspect, significantly influencing the operation expenses of gas transport companies. Such plants are characterized by an increasing level of complexity both for the choice of the technology to adopt for gas compression and for the plant layout and integration, facing a combination of diverse energy demands including electric power, thermal and cooling demands. The present study is developed mining the data provided by the Italian natural gas infrastructure company, Snam Rete Gas, for a key compression station in the North-East of Italy. A feasibility study to increase the capacity of the compressor station has been carried out and an innovative trigenerative application has been proposed to fulfill the overall plant energy requirements, reducing primary energy needs by nearly 30%. Thanks to the outcome of the study, such trigenerative solution has been deployed by Snam Rete Gas. • A case study of a North Italian compression station owned by Snam Rete Gas. • A solution to increase efficiency and reliability of natural gas compression stations. • A comprehensive analysis of the diverse energy demands of the compression station. • Feasibility study of a trigenerative application to fulfill overall energy loads. • The trigenerative plant allows the reduction of primary energy needs by nearly 30%. [ABSTRACT FROM AUTHOR]

• A new graphical technique for inherent safety assessment for preliminary design stage. • Incorporates information obtainable from the process flow diagram (PFD). • Introduces accident statistics as an indicator to hazard level. • Incorporates the amount of the chemical substances as a hazard weightage for root-cause evaluation. User-friendly plants are needed for equipment failure to not seriously affect its safety, productivity, or efficiency. Safer and user-friendly plants can be designed through the implementation of hazard prevention strategies during the design phase, which is known as the concept of inherent safety. The Graphical Inherent Safety Assessment Technique (GISAT) for preliminary engineering design stage is presented in this paper. GISAT incorporates information obtainable from the process flow diagram (PFD) in the assessment of inherent safety features of a process. This technique evaluates three inherent safety parameters, namely flammability, explosiveness, and toxicity. GISAT also utilises accident statistics in the construction of its graphical rating as the hazard level indicator for chemical process equipment assigned under five groups—reactor, heat transfer equipment, separation equipment, storage tank, and other equipment. In this technique, quantity of the chemicals involved in an equipment represents the weightage of the assessment that is used to identify the root-cause of hazards in each equipment. Hydrodealkylation process of toluene (HDA) to produce benzene is used as a case study to demonstrate the application of GISAT. The results indicate that heat transfer equipment E102 as safer in terms of flammability compared to other equipment while all equipment were found to be safer in term of explosiveness. Separation equipment V102, heat transfer equipment E102, and recycle gas compressor C101 were found to be safer in terms of toxicity. Meanwhile, heat transfer equipment E101, E102, and E103 as well as gas compressor C101 are regarded as safer in terms of fire, explosion, and toxic release combination type of accident as represented by the GISAT Total Score. After the level of hazard in each equipment have been identified, hazard prevention strategies can be applied to equipment with higher level of hazard for hazard reduction. [ABSTRACT FROM AUTHOR]

Latest guidelines, novel technical notes, new technical knowledge and recent lessons learned are discussed for emerging market of coal seam gas (CSG) centrifugal compressor trains. Optimum configurations and novel arrangements for coal seam gas (CSG) centrifugal compressor trains driven by gas turbines are addressed. Untreated and saturated nature of CSG need special considerations. Operation, performance, degradation, reliability and maintenance issues of centrifugal compressors, gas turbines, gear units and couplings are also explained. The focus is on new technical knowledge, latest experiences and recent lessons learned on these topics. New recommendations regarding centrifugal compressor train components, gas turbines, machinery arrangement, auxiliaries, gear units, lubrication oil systems, bearings, casing and condition monitoring are also presented. A case study is discussed. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Existing devices available on offshore gas/oil platforms are incapable of realizing complete separation of the liquid phase from wet natural gas. This results in eccentric motion of rotors and eventually causes trouble halting of natural-gas compressors. To tackle this problem, use of a novel gas-liquid separator has been reported for offshore oil platform applications. A pilot scale test was performed using the proposed equipment. Results of the test demonstrate that the optimum operating point of the pilot plant corresponds to a flow rate of 90 m3/h (30 °C, 5.0 MPa), and this could be used as a reference for subsequent industrial scale-ups. The results of the pilot test lead to the conclusion that the said novel separator has higher separation efficiency when compared against conventional industrial devices used on oil platforms. Using of the proposed equipment is aimed at alleviating the problem of liquid entrainment of natural gas entering the compressor, increasing compressor service life, and reducing operational and maintenance costs. The proposed study provides a new outlook towards engineering design of offshore-oil-platform equipment of theoretical as well as practical value. • Use of a novel gas–liquid separator to separate the liquid phase from natural gas extracted from the seafloor is proposed. • Operating conditions during the pilot test were maintained identical to those corresponding to industrial operation. • An improvement in separation efficiency was achieved over conventional separators employing cyclone and wire-mesh demisters. • The service life of compressors will be improved. [ABSTRACT FROM AUTHOR]

• Novel technique is proposed to diagnose vibration data from rolling bearing. • Method indicates perfect fault signature in the presence of multiple impulsive components. • Bi-frequency representation, matrix factorization, spatial denoising are used. • Presented results are based on real data from reciprocating compressor operating in industrial conditions. In this paper, authors present the original procedure for local damage detection in rolling bearings based on vibration data. The aim is to obtain envelope spectrum (ES) of the signal component related to damage, that is clear and easy to interpret. The method is especially aimed at cases, when multiple cyclic impulsive components are present and interfere with each other, which makes ES of such signal very difficult to evaluate. In order to deal with such situation properly, authors propose to choose Cyclic Spectral Coherence (CSC) map as a two-dimensional data representation that will be the basis for the analysis. Nonnegative Matrix Factorization (NMF) is used to analyze such map in two ways: first, it helps to initially separate cyclic components by producing a set of filters for input vibration data, and second, to identify proper damage-related frequency components in envelope spectrum. In addition, an intermediate step of spatial denoising allows enhancing the properties of CSC map. Finally, Monte Carlo simulation improves statistical significance of the result and increases robustness by reducing the impact of random initialization effects. The method has been evaluated using real-life vibration data measured on rolling bearing operating in the industrial gas compressor. [ABSTRACT FROM AUTHOR]

Hydrocarbons in the form of natural gas can be used in long-term energy production and could strengthen the defossilisation of the energy sector. However, operational reliability will decrease due to gas shortages in integrated energy systems. Correlations exist among the multiple failure patterns such as overloads of the transmission lines, overloads of the combined heat and power generator, and over-limit operations of gas compressors. The energy reliability assessment problem becomes more difficult to resolve for integrated energy systems than for power systems. This paper proposes an analytical method to address the multiple correlated risks that are caused by the energy network interactions in an integrated energy system. Three case results in MATLAB demonstrate the accuracy and computational efficiency of the proposed method. Compared to the Monte Carlo algorithm, which required approximately 550 s to obtain a precise failure probability with 50 thousand samples, the proposed method takes approximately 12.7 s to obtain an exact failure probability. The advantage is that, different from wide-bound theory and narrow-bound theory, the proposed method can offer a certain value rather than two bounds with respect to the failure probability. • The correlations among different failure patterns are established for integrated energy systems. • Theoretical analysis and statistical experiments are presented to estimate IES reliability. • Network constraints are modelled to fully analyse the nonlinearity of the IES failure estimation. • Both the estimation accuracy and efficiency are ensured using the proposed analytical method. [ABSTRACT FROM AUTHOR]

• Air/mist phase transition cooling with time-dependent is numerically simulated in a compressor. • Fast Fourier transform is used to analyze the frequency attributions of fluctuating quantities. • Effect of mist injection on flow field is discussed by the arithmetic-averaged result within one period. • Relationship between transient characteristic and mist injection is investigated. A comparative study of performance characteristics in a gas turbine compressor before and after water injection into the air is carried out to explore the relationships between the transient characteristic and mist injection. The Eulerian-Lagrangian particle tracking method is used for solving a process of phase transition cooling of water/air coupling, and the fast Fourier transform (FFT) is adopted to analyze the frequency attributions of fluctuating quantities with time-dependent including total pressure ratio, total temperature ratio, and efficiency. Results show, after mist injection into the compressor, droplet evaporation phase change leads to a higher characteristic fluctuation in the low-frequency region. The sensitivity of efficiency fluctuation is easily affected by the mist injection by comparing with the dry air condition. Within the mist conditions of 1–5 μm droplet sizes and 0.5–5% water/air ratios, the fluctuation of pressure in the compressor reaches a peak in small mist particle and low water/air ratio, resulting in a greater total pressure ratio. The temperature fluctuation gets the minimum in small droplet diameter and large water/air ratio, leading to a lower total temperature ratio. The fluctuation intensity of total pressure ratio, total temperature ratio and efficiency of compressor are increased to 3 times, reduced to 7/9 times and dropped to 3/5 times as water/air ratio increases from 0.5% to 5%, respectively; then, the fluctuation strength correspondingly increases 2 times, decreases 3/4 times and descends 6/7 times with the increase of droplet sizes from 1 μm to 9 μm. Thus, the fluctuation caused by low water/air ratio is higher than the small droplet diameter. Furthermore, efficiency fluctuation gets a minimum in small droplet size and appropriate water/air ratio. [ABSTRACT FROM AUTHOR]

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes. [ABSTRACT FROM AUTHOR]

The global rising demand for civil air travel shows good prospects for the industry, however, this growth is inevitably matched with higher levels of emissions and fuel consumption. In this study, demineralised water injection is presented as an alternative to reduce NO x emissions and enhance engine performance. The experimental study firstly presents the droplet size characterisation of a spray nozzle. This is done for varied injection pressure, water temperature and at varied axial and radial locations using an impaction pin nozzle. The single-shaft Artouste engine is used in conducting the compressor water injection test with water-to-air ratios of 0.5, 1 and 2%. The water droplet diameter, engine gas path and exhaust emissions are all monitored in real time. For the engine tests, droplets are measured at the spraying point and correlations are used to account for the droplet size at the inlet of the compressor due to measurement difficulties in this region. The test showed a reduction in compressor discharge temperature by up to 34 K and a NO x decrease by 25%. Nevertheless, the higher reductions in NO x at higher water-to-air ratios are attributed to a predominant cooling in the combustor because of unevaporated water in the compressor. At 0.5% water-to-air ratio, the drop in NO x is mainly due to compressor cooling and signified by the only case in which the fuel-to-air ratio reduces. The study presents evidence of the combined effects of compressor and combustor water ingestion. The CO is seen to increase significantly and associated with reduced combustor efficiency. • Droplet size sensitivity study is conducted. Factors affecting these are quantified. • Spraying nozzles are used to inject water into the compressor of a gas turbine. • Compressor water injection at 2% leads to a drop in compressor temperature of 37 K. • The reduced cycle temperature results in a 25% reduction in NOx emissions. • Droplet size, engine performance and emissions are all monitored simultaneously. [ABSTRACT FROM AUTHOR]

The Diesel–Brayton combined cycle engine was proposed previously to achieve the goal of lower fuel consumption, higher power density and good startup performance under low-temperature conditions. The prototype engine was designed and tested based on an off-the-shelf gas turbine and a diesel engine. To achieve a more compact and lighter design, the air supply system was designed based on the centrifugal compressor of the gas turbine. In the coupling operation mode aiming to generate the maximum power, a large amount of compressed air must be extracted into the diesel engine. The present paper presents the design methodology of the compact air supply system. The bleeding slot configuration was selected based on a parametric study and proven by systematic experiments. Three-dimensional simulations were conducted to investigate the performance and flow field of the compressor. Backflow appeared in several passages of the axial diffuser caused by air bleeding, which further distorted the air flow in the combustion chamber. Such distortion may cause compressor and combustion instabilities. In the future, the combustion chamber and the axial diffuser must be designed in combination with an air bleeding system to improve the engine performance. [ABSTRACT FROM AUTHOR]

• Dedicated and integrated subcooling systems for CO 2 booster plants are analyzed. • A supermarket of 41 kW at low and 140 kW at medium temperature is considered. • Systems are simulated in 282 locations in Europe and 395 in Asia. • R-290 dedicated subcooling offers benefits for warm and hot regions. • Integrated subcooling reduces energy consumption in tempered climates. Energy improvements offered by dedicated and integrated mechanical subcooling systems in CO 2 booster systems for supermarket applications are analyzed here through the use of thermodynamic models close to reality. Using a reference supermarket with 41 kW and 140 kW thermal loads at low and medium temperature, respectively, and considering as state-of-the-art system the CO 2 booster with parallel compressor and flash gas by-pass, it has been concluded that both systems allow to reduce energy consumption. However, its operation is highly dependent on environmental conditions. The dedicated mechanical subcooling system offers annual energy reductions for tempered places from 1.5% to 2.9%, for warm between 2.9% and 3.4% and for hot from 3.0% to 5.1%. The integrated subcooling system obtains reductions between 3.1% and 4.0% for cold regions, from 1.4% to 2.9% for tempered, from 2.9% to 3.4% for warm and from 1.3% to 2.4% for hot regions. [ABSTRACT FROM AUTHOR]

Highlights • An identification method for misalignment-induced synchronous vibration is proposed. • Changes in rotor static and dynamic response characteristics as key features. • Combination plot and its feature trend plot of average rotor centerline and synchronous orbit. • Synchronous vibrations of a compressor and a flue gas expander are identified. Abstract Misalignment is one of the commonly encountered faults that generate excessive rotor vibration. The diversity of its characteristic frequency brings great trouble for fault diagnosis. Especially when misalignment-induced vibration manifests it as only synchronous (1x) component, properly diagnosing this fault becomes more difficult, since other faults often show the similar frequency signature. To extract discriminative information from the view of fault development, a diagnostic method is proposed with comprehensive utilization of changes in rotor static and dynamic response characteristics. First, rotor static and dynamic responses are deduced, the average rotor centerline (ARC) plot and orbit plot are introduced separately to represent these responses. The results indicate that ARC position changes considerably and 1x-orbit synchronously becomes more flattened with the increase of misalignment, when all machine operating conditions remain constant. Combination of these symptoms can be used to better distinguish misalignment from other 1x vibration problems related to changes in unbalance force, e.g. rotor unbalance and temporary thermal bend. Subsequently, the combination plot and its feature trend plot of ARC and 1x-orbit are developed to fully describe the changes in rotor static and dynamic responses with time and their correlation. Finally, the proposed method was successfully applied to 1x vibrations of a NOx compressor and a flue gas expander. [ABSTRACT FROM AUTHOR]

Abstract Natural gas compressor stations represent a huge potential in terms of waste heat recovery. Typical installations consist of multiple gas turbine units, in mechanical drive arrangement, operated most of the time under part-load conditions. The paper investigates the feasibility of Organic Rankine Cycle application as bottomer recovery technology in natural gas compressor facilities. The aim of the performed analysis is to obtain a detailed techno-economic and environmental scenario of the integrated system on yearly base. Different commercial gas turbine models, in the size range from 3 to 30 MW, have been taken into account as representative of mechanical driver units. Bottomer configurations (with & without intermediate loop) are modelled and compared assuming two different organic fluids. A sensitivity analysis of the bottomer cycle is carried out aimed at maximizing ORC shaft power output for each investigated layout. Off-design part-load operation of the integrated cycles have been simulated with reference to one minute data typical GT operation on a yearly base. The goal of this work is: (i) to assess the actual performance of merging gas turbines and ORC units for efficient power generation under variable operating conditions; (ii) to analyze the real potential of state-of-the art technology in the proposed innovative application. Highlights • Techno-economic investigation of ORC potential, in a real NG compression stations. • Retrofit with ORC commercial GTs, widely diffused in compression facilities. • Simulate part-load of selected GTs according to different control load strategies. • Investigate different organic fluids and topper-bottomer integrated layouts. • Define, for each GT-ORC layouts, optimal design and estimate off-design behavior. [ABSTRACT FROM AUTHOR]

Abstract An industrial highly loaded gas compressor with the large turning angles in gas turbines always causes the serious flow separations, which leads to the significant increase in aerodynamic losses and the evident deterioration of the pressure rise ability. In order to solve this issue, a novel active flow control technique inspired by the Coanda effect is introduced in this study. Here, the Zierke & Deutsch airfoil with the camber angle of 65° is selected for the reference profile of the highly loaded compressor cascade. Design of Experiment (DOE) is firstly used to obtain the sensitivity information of the geometric parameters in building the Coanda jet flap. The cascade shape with the optimal aerodynamic performance is then figured out based on the optimization method. The comparison of the flow details between the optimization result and the prototype is performed to further understand the flow mechanisms behind the performance enhancement. Finally, the experimental measurements are conducted to validate the effectiveness of the well-designed Coanda jet flap in the wind tunnel. The numerical and experimental results show that the Coanda jet can effectively improve the aerodynamic performance of the highly loaded cascade. A tradeoff exists between the increased mixing losses near the slot and the decreased shearing effects near the trailing edge when the mass flow rate of the Coanda jet is increased. The total pressure losses can be reduced by up to 18.4% when the normalized mass flow rate of the jet flow is equal to 1%. Meanwhile, the static pressure rise coefficient can be increased by 8.8% when the mass flow rate of the Coanda jet is equal to 1.5%. Highlights • Coanda jet flap efficiently enhances the performance of industrial gas compressors. • Flow control mechanisms of Coanda jet in highly loaded compressor are summarized. • Optimal Coanda jet flap design is obtained by employing the optimization method. • Experimental measurements validate the effectiveness of Coanda jet flap. • Some design criterions are proposed to guide the further Coanda jet flap designs. [ABSTRACT FROM AUTHOR]

The paper proposes a robust faults detection and forecasting approach for a centrifugal gas compressor system, the mechanism of this approach used the Kalman filter to estimate and filtering the unmeasured states of the studied system based on signals data of the inputs and the outputs that have been collected experimentally on site. The intelligent faults detection expert system is designed based on the interval type-2 fuzzy logic. The present work is achieved by an important task which is the prediction of the remaining time of the system under study to reach the danger and/or the failure stage based on the Auto-regressive Integrated Moving Average (ARIMA) model, where the objective within the industrial application is to set the maintenance schedules in precisely time. The obtained results prove the performance of the proposed faults diagnosis and detection approach which can be used in several heavy industrial systems . [ABSTRACT FROM AUTHOR]

Highlights • We provide the NEW low temperature ignition delay times of 1,3,5-trimethylbenzene. • Available models fail to capture the low temperature reactivity of this fuel, with significant overestimation. • We found that the side chain length effect is stronger than the number of side methyl in accelerating ignition. Abstract Due to the increased interest on understanding the combustion chemistry of the larger alkyl aromatic as jet fuel surrogate component, we provide new ignition delay time data of 1,3,5-trimethylbenzene/O2/Ar mixtures, for the temperature range between 880 and 1090 K, at the pressure of 20.0 and 30.0 bar and for different mixture equivalence ratio and fuel concentration, by using a well validated rapid compression machine with heating system. Measurements show that no negative temperature coefficient behavior was observed for this fuel. Subsequently, these low temperature ignition delay time data were used to validate several kinetic mechanisms including those of Gudiyella and Brezinsky (Combust Flame 2012), Diévart et al. (Fuel 2013), and Wang et al. (Combust Flame 2018), all of which significantly overestimate the reactivity of 1,3,5-trimethylbenzene in this temperature range. Sensitivity analysis at typical condition and comparisons of the rate constants of the ignition dominant reactions in different models indicate that a more complete reaction scheme for 1,3,5-trimethylbenzene (T135MB) and more accurate rate constant should be further pursued, especially for the reactions of H abstraction from T135MB and fuel radical consumption reactions. Finally, ignition delay times of toluene is lower than T135MB and n-propylbenzene at the same condition, which indicate that the larger number of side chain and the longer side chain length enhances the low temperature reactivity. In addition, for the same fuel isomer, the effect of the side chain length is stronger than the number of side methyl in accelerating ignition since n-propylbenzene presents an even shorter ignition delay times than T135MB. We believe the present work will be of merit for future jet fuel surrogate model development. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to describe the methodic and the software developed by authors, which has aimed to simulate operation modes of a centrifugal gas compressor and associated equipment. In this paper, the computer-based design and the analysis of control systems for centrifugal gas compressors are presented. The structure of the mathematical models and the solution methods are discussed. A Visual Basic-based application has been built to solve the system dynamics and to generate the model in installation executable format. The application allows simulating the behavior of a gas compression network through an individual simulation of each component in the network like gas compressor, valve, heatexchanger, gas-liquid separator, pipe line. Flow through the system elements is modeled as a multi-component compressible gas flow and the Redlich-Kwong Equation of State is used to solve the mass conservation equation. Based on the centrifugal gas compressor theory an anti-surge control strategy has been applied to the model in order to predict and control surge cases. The one-stage gas compression model has been used to verify how the software responds to changes in the suction and discharge conditions. [ABSTRACT FROM AUTHOR]

Abstract Employing the systems which make use of waste heat for upgrading its temperature is of great importance for their energy saving potential. In this research, the thermoeconomic analysis of a novel ejector boosted hybrid heat pump (EBHP) is evaluated and compared with three other types of heat pumps namely the absorption, compression, and absorption/compression heat pumps. The analysis uses the exergy costing method that combines the exergy concept with the economic analysis to evaluate the unit cost of final product at the wide operating range. The results reveal that the advantages of the proposed heat pump from the thermoeconomic view point are clear in higher upgraded temperatures. A detailed analysis of the different thermoeconomic variables is also conducted and the contributions of each component in the overall cost of the heat pumps are evaluated. In addition, effects of various decision variables on the economic performance of the systems are studied. The investigations demonstrate that the concentration of ammonia in hybrid heat pumps and the pinch point temperature difference in all of the studied heat pumps affect the final unit product cost of the systems considerably. Highlights • An ejector boosted hybrid heat pump is compared with three other types of heat pumps. • Thermoeconomic variables are used to analyze the economic performance of each component. • For low temperature lifts, the absorption heat pump has lower unit product cost. • As the temperature of upgraded heat increases, the EBHP shows better performance. • The effect of operating parameters on the product cost of the systems is investigated. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a method for improving the efficiency of the cascade mechanical compression–ejector cooling cycle is described. The considered cooling cycle is the combination of the electrically driven carbon dioxide (CO 2) subcritical mechanical compression cooling cycle as a bottoming cycle, and the heat driven ejector cooling cycle as a topping cycle. This cooling cycle is proposed to use superheated CO 2 vapor to preheat the working fluid supplied to the vapor generator, thus improving the whole system's efficiency. This paper provides thermodynamic analysis results for the cascade cooling system in a wide range of evaporating temperatures. Refrigerants R245ca, R600, and R601b were investigated as the working fluids for the ejector cooling cycle, and the results show that the proposed cooling cycle is the most effective at low evaporating temperatures. Highlights • A cascade CO 2 mechanical compression–ejector cooling cycle is studied. • Refrigerants R245ca, R600 and R601b are used for the ejector cooling cycle. • Performance improvement regarding COP, COP THERM and exergy efficiency is evaluated. • The refrigerant preheating has considerable influences on the cascade cycle performance. • The proposed cascade cooling cycle is compared with conventional cycle. [ABSTRACT FROM AUTHOR]

Calculation formulas for estimating the influence of the state parameters of temperature, pressure, and moisture content on the operation of a piston compressor are obtained. It is shown that at the start of compression in a compressor temperature depends mainly on heating of the gas produced by the walls and its moisture content. The pressure at the start of compression depends on the speed of the piston and the moisture content of the gas. The principal factors responsible for a reduction of the feed rate and efficiency of the compressor are the increase in temperature and the decrease in pressure at the start of compression. [ABSTRACT FROM AUTHOR]

In this paper, a study of gasdynamic processes that occur in a low-flow aerothermopressor has been done. The aerothermopressor is a two-phase jet apparatus for contact cooling, in which, due to the removal of heat from the air flow, the air pressure is increased (thermogasdynamic compression) and its cooling is taken place. Highly effective operation of the aerothermopressor is influenced by primarily the flow part design and the water injected method in the apparatus. Constructive factors that influence energy costs to overcome friction losses and local resistances on the convergent-divergent sections of the aerothermopressor are exerted a significant impact on the working processes in the apparatus. In this paper, a study of a number of typical low-flow aerothermopressor models has been conducted by using computer CFD modeling. Determination of the main parameters of the air flow (total pressure, dynamic pressure, velocity, temperature, etc.) has been carried out for a number of taper angles of a confuser α and a diffuser β , as well as for a number of values of the relative air velocity in the working chamber M = 0.4-0.8. Comparison of the obtained data with experimental data has been carried out. The deviation of the calculated values of local resistances coefficients in the confuser and in the diffuser from those obtained by computer CFD modeling does not exceed 7-10%. The recommended angles were determined: confuser convergent angle - 30° and diffuser divergent angle - 6°, corresponding to the minimum pressure loss is 1.0 - 9.5 %, and therefore also to the maximum pressure increase as a result of the thermogasdynamic compression that occurs during injection and evaporation of liquid in the working chamber. Thus, analytical dependences are obtained for determining the local resistance coefficients for the confuser (nozzle) and the diffuser, which can be recommended to use in the design methodology for low-flow aerothermopressors. [ABSTRACT FROM AUTHOR]

• EEMD and HT approaches are adopt for the internal leakage detection. • EMD and DWT based methods are applied on the same pressure signals. • The developed scheme owns the best performance among three approaches. This paper investigates the detection of the internal leakage in the hydraulic inlet guide vane (IGV) system at the gas turbine compressor. Based on methods of ensemble empirical mode decomposition (EEMD) and Hilbert transform (HT), we propose the internal leakage detection method. Firstly, EEMD is applied to decompose the pressure signal at chamber A of the cylinder into intrinsic mode functions (IMFs). Secondly, the instantaneous amplitude of the first IMF (IMF1) is obtained through HT. Finally, the mean of IMF1 instantaneous amplitude at a time period is adopted for the detection of the internal leakage fault and its levels. After setting the proper number of ensemble size and threshold value of the white noise amplitude to reduce the root mean-squared deviation for the multi-mode distribution of the IMFs, the developed method can identify the internal leakage in the IGV cylinder during experiments under the time-varying cylinder position and load at a built hydraulic IGV emulator. The empirical mode decomposition (EMD) and discrete wavelet transform (DWT) based methods are applied on the same pressure signals, respectively. The results show that the developed scheme owns the best performance comparing with the EMD and DWT based approaches in our case. [ABSTRACT FROM AUTHOR]

Abstract This paper aims to investigate the flow of natural gas in the cyclotubes of scrubber installed in gas compressor station. The boundary conditions of this cyclotube are similar to the actual condition of the facility and static pressure, tangential velocity, axial velocity and radial velocity in different lengthwise and transverse sections have been investigated. After simulating the flow, black powder particles were injected into cyclotubes and the number of particles trapped and exited from the cyclotube was measured. These particles are studied in five different diameters and at six velocities, and the cyclotube efficiency is obtained for 30 states. In the end, by measuring the pressure drop in the cyclotube, its effectiveness is discussed. The efficiencies were found in cyclotubes that have a particle diameter between 40% and 60% is lower than the predicted value. Also, the results show that with increasing velocity, the pressure drop increases. Graphical abstract Unlabelled Image Highlights • Investigation the flow of natural gas in the cyclotubes of scrubber installed in gas compressor station • Boundary conditions are similar to the actual condition of the facility. • Black powder particles were injected into cyclotubes. • Number of particles trapped and exited from the cyclotube was measured. • By measuring the pressure drop in the cyclotube, its effectiveness is discussed. [ABSTRACT FROM AUTHOR]

Abstract In this study effects of compression ratio on HCCI combustion, performance and emissions was investigated parametrically. In addition to parametric investigation and as a novel way of the paper engine BSFC maps were obtained for RON20 andRON40 fuels and each compression ratios of 9:1, 10:1, 11:1 and 12:1. The parametric experiments were carried out at 800 rpm engine speed. In both parametric and mapping experiments were conducted at intake temperature of 353 K. In-cylinder pressure, ROHR, combustion duration, start of combustion, indicated mean effective pressure, thermal efficiency and CO, HC and NO x emissions were examined. It was determined that in-cylinder pressure and rate of heat release decreased while the mixture getting leaner. The increase of octane number of fuel led to extension of combustion duration. On the contrary, combustion duration decreased along with the increase of compression ratio. It was found that the CO and HC emission were high while NO x emissions were low at lower CR. With the increase of CR, CO and HC emissions decreased however NO x emissions increased. The maximum thermal efficiency was obtained as 38.2% at 800 rpm and 12:1 CR with RON40 fuel. The widest operational region was obtained with RON20 fuel at CR of 10:1 with a minimum BSFC value of 210 g/kWh. Highlights • RON20 and RON40 fuels were tested in A HCCI engine at different compression ratios. • RON, lambda and compression ratio effects on HCCI engine was examined parametrically. • Additionally BSFC and operation maps were determined for each compression ratio. • RON40 seems more suitable fuel due to controlling the HCCI combustion in all compression ratios. • Largest operation map in terms of engine load and speed was obtained with RON20. [ABSTRACT FROM AUTHOR]

Abstract As known that the cooling technology is commonly used in the turbine to protect the turbine blade. The mixing and heat transfer between the high pressure cooling air from the compressor and the turbine main flow would cause energy loss, and it will influence the gas turbine cycle performance. However, the existing definitions of the cooled turbine efficiency always take no account of the work which is added to the cooling air to product high pressure in the compressor, thus, the cooling influence on the gas turbine cycle performance cannot be indicated by using the existing cooled turbine efficiency. In this paper, a definition of cycle based comprehensive efficiency for a cooled turbine is presented, in which the work added to the cooling air during its compression process is considered. The existing efficiency definitions are first reviewed, then, the definition of the cooled turbine comprehensive efficiency is presented and validated numerically to show its capacity. Finally, the redesign of a high-pressure turbine is provided. The result shows that the new efficiency can evaluate a cooled turbine performance comprehensively, and can be used as a reliable evaluation criterion for the optimal design of a turbine or a gas turbine cycle. Highlights • Provide a definition of cycle based comprehensive efficiency for cooled turbines. • Compare the new definition with the existing efficiency definitions. • Capable of considering the influence of coolant fraction on cycle performance by affecting turbine efficiency directly. • Capable of providing a more reliable method to evaluate the optimization design of cooled turbines. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a hybrid power generation system comprising of Photovoltaic (PV) panels, Molten Carbonate Fuel Cell (MCFC), Gas Turbine (GT), Thermal Energy Storage (TES), Battery (Bat) and a Compressed Air Energy Storage (CAES) system. The CAES pressure was considered to be regulated using a water reservoir system located at a suitable height place. The described system was designed to supply the electricity needs of 500 households with peak electricity demand of 500 kW. A set up MCFC/GT with power generation rate of 500 kW was considered in the calculations, and the PV system capacity was considered to be changed from 100 kW to 600 kW. The optimal configuration and operational conditions of the system were conducted based on the Levelized Cost of Electricity (LCOE) definition as well as the total annual emission that is occurred by the auxiliary fossil fuel boiler and MCFC systems. The results showed that the overall system efficiency would be increased by about 25%, when the CAES is used and the compressor is switched off. Also, the optimal operational pressure of MCFC was found to be 6 bar for 2000 number of PVs, 1500 kWh of battery storage and CAES capacity of 685 m3. Highlights • Investigate the combination of MCFC/PV/GT system for generating a determined electricity load. • Using of the storage systems to obtain the high reliability. • Consider the effect of different parameters on operation of the hybrid system. • Suggestion of using a water reservoir with CAES to generate a constant pressure supply air. • Using a hybrid electrical energy storage to reduce the waste of PVs generated power. [ABSTRACT FROM AUTHOR]

Highlights • Transient gas compressor modeling for estimating process state trajectories. • Dynamic time to surge computation using process and electrical measurements. • Model predictive surge protection for safe under-voltage ride-throughs. • Analysis of two under-voltage occurrences on an industrial-sized gas compressor. Abstract This article is concerned with the impact of voltage or power dips on large electric driven gas compressors (EDC) in typical oil and gas applications. EDCs are sensitive to voltage dips affecting the operation of the gas compression process through the complete or partial loss of motor torque. These events result in unpredictable shutdowns and plant trips typically leading to large economic losses in production. The loss of motor torque often puts the process at risk of surge conditions resulting in unstable operating conditions and possibly also in severe damage of the centrifugal compressors and their surrounding equipment. The critical nature of this problem and the fast dynamics involved, pose challenging requirements for the control and safety systems of the gas compressor and the variable-speed drive system. The main aim of the present paper is to present a model-based protection algorithm to safely decide if the EDC can ride-through or needs to be shutdown during voltage dips. This is done by dynamically computing the time to surge using online information from the process, from the electrical system and a process model to predict the behavior of the compression system. The time to surge value is then compared to a safety limit in order to reach a ride-through or shut-down decision. The approach is tested in simulation and after the deployment on an industrial sized compressor, two recorded voltage dips from the field are presented and discussed. [ABSTRACT FROM AUTHOR]