Increase In Compression Ratio Research Articles

Numerical investigation on the bearing capacity of RC columns strengthened by HPFL-BSP under combined loadings

To study the effect of the axial compression ratio, torsion-bending ratio, and eccentricity on the mechanical performance of reinforced concrete (RC) columns under combined loadings, the numerical analysis is implemented based on ABAQUS and agrees well with the experimental results. The bearing capacity increased with the increase of the axial compression ratio, but the energy dissipation and ductility decreased. The bearing capacity and stiffness are degraded with the increase of the torsion-bending ratio. When the eccentricity increased from 0.125 to 0.25, the numerical results show the poor seismic performance. The results show that loading methods affected the mechanical performance, and the negative effect of the torque is noticeable. Moreover, the unified bearing capacity of RC columns under combined torsion is calculated by the modified existing Park & Ang failure criterion.

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study, an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load. The boundary column and shear wall were divided into fiber elements, and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens. The results show that the finite element analysis results were in good agreement with the experimental results. The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall. The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters: axis compression ratio, height to width ratio, ratio of vertical reinforcement, and ratio of longitudinal reinforcement in the boundary column. The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease. The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase. The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility. The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.

Experimental Study on the Influence of Second-Order Effect on Shear Bearing Capacity of Frame Columns with Cracks under Different Axial Compression Ratios

The construction joint is the weak part of the structure, and the P-δ effect is mostly ignored when considering the second-order effect, so it is necessary to study the influence of second-order effect on frame columns. Based on the above considerations, under different axial compression ratios, the mechanical properties of the construction joints of the frame columns with construction joints and the cast-in-situ frame columns were studied by low cycle repeated load testsand analyzed the influence of the second-order effect on the shear capacity of frame columns with joints. The test results indicate that the existence of construction joints reduces the shear-bearing capacity of the specimens, and the second-order effect has a greater impact on the columns with joints under the same axial compression ratio, and the shear capacity decreases more. With the increase of the axial compression ratio, the second-order effect will be weakened on the frame column with seam, but when the axial compression ratio exceeds a certain limit, the second-order effect will be increased.

Experimental Study of the Effect of Increased Compression Ratio on the Torque and Power of the Honda CB 150R Engine Using E85 Fuel

Switching from fossil fuels to alternative fuels requires adjusting several engine parameters to avoid a decrease in engine torque and power. This happens because of the different properties of different fuels. One of the parameters that must be set is the compression ratio. This study aims to determine the effect of increasing the compression ratio on the torque and power of the Honda CB 150R engine using 85% bioethanol (E85) as fuel. The research method used an experimental method with 2 types of fuel and variations in the compression ratio. From the research results, it can be seen that the torque and power using E85 fuel have increased respectively by 1.08% and 1.5% when compared to the standard compression ratio using fossil fuels.
 Pergantian bahan bakar dari fosil ke bahan bakar alternatif membutuhkan pengaturan pada beberapa parameter engine untuk menghindari terjadinya penurunan pada torsi dan daya mesin. Hal ini terjadi karena perbedaan dari properties bahan bakar yang berbeda. Salah satu parameter yang harus di atur adalah rasio kompresi. Penelitian ini bertujuan untuk mengatahui pengaruh dari peningkatan rasio kompresi terhadap torsi dan daya engine Honda CB 150R menggunakan bahan bakar bioetanol 85% (E85). Metode penelitian menggunakan metode eksperimen dengan 2 jenis bahan bakar dan variasi pada rasio kompresi. Dari hasil penelitian terlihat bahwa torsi dan daya dengan menggunakan bahan bakar E85 mengalami peningkatan masing-masing sebesar 1,08 % dan 1,5 % jika dibandingkan dengan rasio kompresi standard menggunakan bahan bakar fosil.

An analytical model for PVC-FRP confined reinforced concrete columns under low cyclic loading

Experimental investigations on the seismic behaviors of the PVC-FRP Confined Reinforced Concrete (PFCRC) columns under low cyclic loading are carried out and two variable parameters including CFRP strips spacing and axial compression ratio are considered. The PFCRC column finally fails by bending and is characterized by the crushing of concrete and yielding of the longitudinal reinforcement, and the column with a high axial compression ratio is also accompanied by the cracking of the PVC tube and the fracture of CFRP strips. The hysteretic curves and skeleton curves of the columns are obtained from the experimental data. With the increase of axial compression ratio, the stiffness degradation rate accelerates and the ductility decreases. With the decrease of CFRP strips spacing, the unloading sections of the skeleton curves become steep and the ductility reduces significantly. On the basis of fiber model method, a numerical analysis approach for predicting the skeleton curves of the PFCRC columns is developed. Additionally, a simplified skeleton curve including the elastic stage, strengthening stage and unloading stage is suggested depending on the geometric drawing method. Moreover, the loading and unloading rules of the PFCRC columns are revealed by analyzing the features of the skeleton curves. The quantitative expressions that are used to predict the unloading stiffness of the specimens in each stage are proposed. Eventually, an analytical model for the PFCRC columns under low cyclic loading is established and it agrees well with test data.

Effect of Strain Rate on the Microstructure and β-Texture Evolutions in β-Processed Forging of a Near-β Titanium Alloy

The effect of strain rate on the β texture evolution during two-step hot forging of Ti-6246 alloy was investigated. The two-step forging consisted of 15% or 50% prior-β forging at 980°C and subsequent 60% or 25% forging at 870°C in the (α + β) dual-phase region. The total compression ratio was 75%, and the investigated strain rates were 0.01 and 1.0 s−1. The β forging texture showed typical {001} and {111} body-centered cubic textures. With increasing compression ratio in the (α + β) region and at a strain rate of 0.01 s−1, the amount of precipitated α phase increased. Dynamic recrystallization was rarely observed after forging in the (α + β) region at a strain rate of 0.01 s−1. Large amounts of α precipitates lowered the {001} β texture intensity through slip transmission between the α and β phases under the Burgers orientation relationship. However, in specimens forged at a strain rate of 1.0 s−1, as the compression ratio in the β single-phase region increased, the growth of dynamic-recrystallized β grains was promoted at the prior-β grain boundaries, where α-phase precipitation was not substantial. These effects resulted in a higher {001} texture intensity of the β phase in specimens forged at 1.0 s−1 compared with that of the β phase in specimens forged at 0.01 s−1.

Experimental study the impacts of the key operating and design parameters on the cycle-to-cycle variations of the natural gas SI engine

High cycle-to-cycle variations (CCV) in the spark ignition (SI) engine will not only lead to incomplete combustion and even misfire, but also affect the fuel economy and even influence the drivability and conformability of a vehicle, particularly at the lean-burn condition. However, the detail information about the root causes of CCV are still relatively limited, particularly the natural gas SI engine. In this paper, the impacts of the key operating and design parameters were investigated on the CCV of the high compression ratio SI natural gas engine under lean mixture condition. The results indicated that the in-cylinder pressure distribution tended to be concentrated, the number of partial burning or incomplete combustion cycles also reduced with increasing the engine speed. With increasing the load, the in-cylinder pressure distribution, peak combustion pressure and its location were tended to be concentrated. Furthermore, the number of the partial combustion or post combustion cycles declined from low-load to medium- and high-load zones. Moreover, the relationship between the peak combustion pressure and its location was almost linear with increasing the engine load. Unfortunately, with further increasing engine load, in-cylinder pressure traces started to disperse slightly. Under the low-load condition, in-cylinder pressure traces were tended to be concentrated with increasing compression ratio (CR). As CR continually increased, its influence on the in-cylinder pressure distribution decreased. In addition, the number of the partial combustion or post combustion cycles decreased with increasing CR. However, under the high-load condition, increasing the CR has slightly effects on the in-cylinder pressure distribution.

Experimental analysis of CI engine using zirconia ceramic powder coated piston fuelled with Karanja biodiesel

The purpose of this research work is to find the performance of bio -diesel fueled compression ignition engine with and without Zirconia ceramic powder as a thermal barrier coating on the piston head by using plasma spray technique. Experiments were carried out on water cooled engine at constant speed and fixed loaded compression ignition engine, to find the brake thermal efficiency, brake specific fuel consumption and brake power for various injection operating pressures and compression ratios. With an increased compression ratio from 13.99 to 17.5 the brake power, brake specific fuel consumption and brake thermal efficiency were found to improve by 2.55%, 20.75% and 9.23% respectively, similarly as injection operating pressure was increased from 160 to 190 bar the brake power, brake specific fuel consumption and brake thermal efficiency were found to be improved by 1%, 9% and 3.26% respectively.

Experimental study on the ability of different biogas level dual fuel spark ignition engine: Emission mitigation, performance, and combustion analysis

The major aim of the research is to investigate the ability of biogas as an alternative fuel for gasoline-powered Spark Ignition (SI) engine. In this study, biogas/gasoline fuel mixtures containing different ratios of biogas, gasoline, and biogas were tested in an SI engine with an increased compression ratio at different engine loads and constant engine speed. According to the comparison with gasoline, the utilization of biogas generally decreased the Brake Thermal Efficiency (BTE), while the Brake Specific Fuel Consumption (BSFC) rose. The lowest BTE and the highest BSFC were obtained with 100% biogas. Compared to gasoline, a decrease of 16.04% and an increase of 75.52% were observed, respectively. On the other hand, the use of biogas has improved all emissions. The best emission values were obtained with 100% biogas. Compared to gasoline, Carbon monoxide (CO), HydroCarbon (HC), and Nitrogen Oxide (NOx) emissions decreased by 56.42%, 63%, and 48.96%, respectively. Finally, according to the results of the combustion analysis, the peak pressures were reduced with the utilization of biogas, and the position of the peak pressure shifted by 2° to 3° Crank Angle (CA). Compared to gasoline, the lowest pressure was obtained with 100% biogas, resulting in a reduction of approximately 24.69%.

Experimental Study on the Shear Performance of Steel‐Truss‐Reinforced Concrete Beam‐Column Joints

In order to study the influence of the axial compression ratio and steel ratio on the shear‐carrying capacity of steel‐truss‐reinforced beam‐column joints, five shear failure interior joint specimens were designed. The effect of different coaxial pressure ratios (0.1, 0.2, and 0.3) and steel contents on the strain, ultimate bearing capacity, seismic performance, and failure pattern of cross‐inclined ventral and chord bars in the joint core area was investigated. The experimental results show that the load‐displacement hysteretic curves of all test specimens exhibit a bond‐slip phenomenon. With the increase of the axial compression ratio, the ultimate bearing capacity of the joint core increases by 3.4% and 5.9%, respectively. While the ductility decreases by 10.3% and 13.1%, and the energy consumption capacity decreases by 3.2% and 5.8%, respectively. The shear capacity and ductility of the member with cross diagonal ventral steel angle in the joint core are increased by 12.9% and 13.4%, respectively. The shear capacity and ductility of the joint can be significantly improved by increasing the amount of steel in the core area. The expression of shear capacity suitable for this type of joint is obtained by fitting analysis, which can be used as a reference for engineering design.

The Influence of Axial Compression Ratio on the Seismic Behavior of RC Frame Column

In order to analyze the quantitative influence of the axial compression ratio on the seismic performance of reinforced concrete (RC) frame column, this paper carried out the numerical analysis of the quasi-static simulation of a RC frame column and analyzed its hysteresis performance, bearing capacity, stiffness degradation, energy consumption capacity and ductility capacity under different axial compression ratios, based on OpenSees finite element software, considering the buckling and fatigue damage model. The results show that the smaller the axial compression ratio, the fuller the hysteresis curve and the slower the stiffness degradation of the column. The ultimate bearing capacity of the column increases by 24.6% when the axial compression ratio increases from 0.3 to 0.8, but bearing capacity decreasing and stiffness degradation is faster and faster. When the deformation does not exceed the ultimate displacement, the equivalent viscous damping at each displacement level of high axial compression ratio column is greater than that of the low axial compression ratio, but the total hysteretic energy decreases about 64.2% at maximum amplitude. The ultimate displacement gradually decreases with the increase in the axial compression ratio, and the ductility factor decreases about 55.9% at maximum amplitude. The results can be referenced by the seismic design and analysis of RC frame.

Seismic behavior of prefabricated high-strength concrete columns confined by overlapping stirrups

Six specimens of prefabricated high-strength concrete columns with confining overlapping stirrups were tested under cyclic lateral loads, and a finite element analysis was performed using ABAQUS to investigate the seismic behavior of the columns. The influences of the axial compression ratio, stirrup diameter and stirrup spacing were considered. Comparative analyses indicate that the numerical simulation outcomes agree well with the experimental results, including the hysteretic curves, peak loads and failure modes. With an increase in the axial compression ratio, the ultimate load bearing capacity of the specimen increases, ductility worsens, strength descending part of the shear-displacement skeleton curves steepens, and energy dissipation capacity increases slightly. When the stirrup spacing decreases or the stirrup diameter increases, the ultimate load bearing capacity, ductility and energy dissipation capacity of the specimens increase. The effect of the axial compression ratio on the shear capacity of the test specimens is much more pronounced than that of the stirrup ratio. With an increase in the stirrup diameter, the initial stiffness of the specimen decreases, and stiffness deterioration during the late stages of loading cycles slows down. However, changing the spacing of the stirrups has little effect on the stiffness of the specimens.

Experimental Study and Failure Mechanism Analysis of Rubber Fiber Concrete under the Compression‐Shear Combined Action

In order to examine the compression‐shear combined mechanical properties of rubber fiber concrete, an experimental study was carried out on rubber fiber concrete of three different configurations using a material compression‐shear testing machine by considering different axial compression ratios. The failure modes and shear stress‐strain curves of rubber fiber concrete under different loading conditions were obtained. By comparatively analyzing the mechanical parameters of rubber fiber concrete under different axial compression ratios, the following conclusions were drawn. With the increase of the axial compression ratio, the failure mode in the shear direction gradually developed from a relatively straight crack to a main crack accompanied by a certain amount of axial cracks; meanwhile, the number of concrete slags on the shear failure section was gradually increased and the friction marks were gradually deepened. The addition of rubber particles increased the randomness and discreteness of the concrete upon failure, while fibers inhibited the development of oblique micro‐cracks and the dropping of concrete slags. The shear stress of the concrete specimen containing rubber particles was significantly lower than those without rubber particles. Comparatively, fibers showed little effect on the shear stress. As the axial compression ratio increased, the shear stress and shear strain of rubber fiber concrete were gradually increased, but the increasing amplitude of shear stress tended to become flattened. Under the influence of the axial compression ratio, the shear stress of C‐0%‐0%, C‐30%‐0%, and C‐30%‐0.6% was increased by 4.57 times, 3.26 times, and 2.69 times, respectively, suggesting a gradually decreasing trend. At the same time, based on the principal stress space and the octahedral stress space, the compression‐shear combined failure criterion was proposed for the three different rubber fiber concretes. The research findings are of great significance to the engineering application and development of rubber fiber concrete.

Shear behavior of steel reinforced concrete column-steel beam joints with or without reinforced concrete slab

As one of the key parts of a frame structure, joints are usually subjected to large shear forces under seismic loads. The calculation of joint shear capacity is an essential step in seismic design. In this paper, the existing calculation methods for shear capacity of steel reinforced concrete (SRC) column-steel beam joints from different standards were studied and compared in detail. Quasi-static cyclic tests were conducted on six SRC composite column-steel beam joint specimens with or without reinforced concrete (RC) slab. The corresponding shear capacities were calculated based on the stress mechanism of the joints, and several existing calculation methods were compared. The main design parameters in the tests were axial compression ratio and concrete slab width. Results showed that the shear capacity of the joints increased with an increase in the axial compression ratio. The addition of X-reinforcement had little effect on the shear capacity of the joints, while an RC slab could greatly increase the shear capacity of the joints. Finally, the formula for the shear capacity suggested by Chinese standard of JGJ138-2016 was improved to consider the effect of RC slabs on capacity of the SRC column-steel beam joints through finite element analysis. The modified formula was proven to be effective and feasible in engineering practice.

Study on the performance of concrete-filled steel tube beam-column joints of new types

In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.

Retraction Note to: Effect of piston bowl geometry modification and compression ratio on the performance and emission characteristics of DI diesel engine

The present study describes the experimental investigations carried out to study the influence of modified piston bowl geometry at a constant speed of the combustion, performance and emission characteristics of a direct injection compression ignition diesel engine. The modified piston profiles, namely hemispherical combustion chamber (HCC) and toroidal combustion chamber (TCC), are manufactured with a baseline compression ratio of 17:1, and the effects of compression ratio (16:1, 17:1 and 18:1) are analyzed. Experiments are carried out with pure diesel for low load to full load conditions for better understanding. With an increasing compression ratio of the engine, TCC piston geometry has shown better improvement in brake thermal efficiency, carbon monoxide and hydrocarbon emissions than HCC. However, a slight penalty in NOx emission is observed with increasing compression ratio and TCC piston geometry. In-cylinder peak pressure, net heat release rate and rate of pressure rise are increased significantly with increasing compression ratio and the use of TCC geometry.

Research on the operating boundary of the dual mode scramjet with a constant area combustor through thermodynamic cycle analysis

The maximum pressure ratio of the isolator is important for studying the operating boundary of the dual mode scramjet. In this paper, the pressure rise mechanism of the dual mode scramjet engine and the characteristic of the isolator maximum pressure rise are analyzed. The operating range and performance of scramjet under the pressure rise limit are investigated using the constant cross-sectional area combustor. The maximum pressure ratio of the isolator confines the back pressure from the combustor so that the scramjet engine has a minimum freestream Mach number of each equivalence ratio. When the freestream Mach number is smaller than the minimum freestream Mach number, an expansion section may be arranged between the combustor and the isolator to balance the pressure of the combustor and that of the isolator. The expression of the minimum freestream Mach number is derived and it is found that the minimum freestream Mach number of the dual mode scramjet in both modes increases with the increase of equivalence ratio and compression ratio of the inlet. A variable divergent section is suggested to balance the pressure under different freestream Mach numbers and equivalence ratios.

Modelling of combustion and knock onset risk in a high-performance turbulent jet ignition engine

The reduction of CO2 emissions, and hence of fuel consumption, is currently a key driver for the development of innovative SI engines for passenger car applications. In recent years, motorsport technical regulations in the highest categories have seen the introduction of limits concerning the fuel flow rate and the total amount of fuel per race, thus driving engine development toward further reduction of specific fuel consumption. Among the different techniques that can be shared between conventional and high-performance SI engines, turbocharging, compression ratio increase and Turbulent Jet Ignition (TJI) have shown a significant potential for fuel consumption reduction. The combination of turbocharging and compression ratio increase, however, can promote the onset of knocking combustion, with detrimental effects on engine's efficiency and durability. Additionally, engines equipped with TJI systems show unusual combustion development and knock onset.In this study a methodology for the 3D-CFD modelling of combustion and knock onset risk was developed for a high-performance turbocharged engine featuring a passive TJI system. First, a comprehensive numerical study was carried out in a commercially available software, CONVERGE 2.4, in order to develop a 3D-CFD model able to reproduce the available experimental data. The resulting 3D-CFD model was then validated on different working conditions featuring different spark advances. Lastly, a methodology for the assessment of knock onset risk was developed, which led to the definition of two novel knock-risk indexes based on the progress of chemical reactions within the combustion chamber. The proposed knock-risk indexes showed good agreement with the experimental data.

The seismic performance of precast short-leg shear wall under cyclic loading

In order to study the seismic performance of precast short-leg shear wall connected by grouting sleeves (PSSW), the three-dimensional numerical model was established by using the experiment of PSSW subjected to low cyclic loading. Based on good agreement between numerical results and experimental results, the numerical analysis models with different structural parameters of axial compression ratio and splicing position were designed in detail, and the effects of various parameters on the seismic performance of PSSW were analyzed. The results show that the PSSW exhibits wide and stable hysteresis loops, indicating a satisfactory hysteretic performance and an excellent energy consumption capacity. With the increase of the axial compression ratio, the shear capacity of horizontal splice seam is improved, but the ductility coefficient and total energy consumption decrease obviously. The most disadvantageous position of PSSW can be effectively avoided by changing the position of the post pouring seam. The bearing capacity of the specimens is basically stable, and the energy consumption increases significantly, so the post pouring seam of precast wall is recommended to be far away from the bottom section of the wall. In addition, the failure mechanism of different splicing positions was analyzed in detail.

Combustion investigation of waste cooking oil (WCO) with varying compression ratio in a single cylinder CI engine

Biodiesel is a popular alternative fuel of mineral diesel which is normally produced by using straight vegetable oils (SVO). Since the conversion of edible oils into biodiesel may affect its supply/availability as a food item, it is desirable to use non-edible oils for biodiesel production for a long time. Waste cooking oil (WCO) is one such non-edible oil, however superior in quality for biodiesel production through transesterification. The current study is mainly focused on the utilization of WCO as an alternative for mineral diesel in a typical agricultural compression ignition four stroke water-cooled engine. Effect of higher compression ratio (CR20) on various combustion and performance parameters such as in-cylinder pressure (P-θ), heat release rate (HRR), peak pressure (Pmax), maximum pressure rise rate (dP/dθ)max, combustion duration, combustion phasing etc. were investigated for WCO biodiesel and compared with mineral diesel. These experiments were performed for five different loading conditions (No load to full load) at 1500 rpm. Increase in compression ratio (CR) from 18 to 20 resulted in lower ignition delay for higher engine load condition which reduced by 6 CAD. Full load engine operation resulted in 32% brake thermal efficiency (BTE) for WCO biodiesel which was 18% higher than diesel. Peak in-cylinder pressures (Pmax) were observed similar for diesel and WCO biodiesel for same operating conditions except full load condition where it showed lower Pmax value. WCO biodiesel turned out to be more efficient with 6% lower BSFC for the full load operating conditions (CR20).