Compression Pressure Research Articles

Parametric evaluation of neat methanol combustion in a light-duty compression ignition engine

Methanol is currently considered a promising alternative fuel for energy de-fossilization due to its simplicity and adequacy for renewable production. This study investigates the feasibility of using neat methanol in high-efficiency compression ignition engines, with a focus on its potential to reduce CO2 emissions compared to conventional diesel. However, achieving efficient combustion of neat methanol in compression ignition engines presents challenges due to its low ignition capability, requiring higher compression ratios, intake temperatures, and pressures than diesel for autoignition. Furthermore, the high latent heat of vaporization contributes to significant cycle-to-cycle combustion variability. This work evaluates the combustion characteristics of neat methanol in a light-duty multi-cylinder compression ignition engine with a 19:1 compression ratio, examining its suitability for commercial applications. Performance indicators such as engine efficiency, fuel consumption, and engine-out pollutant emissions are assessed. The findings contribute to advancing research and implementation of methanol fuel as an energy source for internal combustion engine vehicles, addressing both the advantages of the fuel and the challenges that need to be overcome, particularly with respect to its low auto-ignition characteristics. Notably, despite methanol's lower energy density compared to diesel, the achieved combustion efficiency is comparable, with remarkable improvements in NOx and soot emissions trade-off.The study reveals that neat methanol combustion poses difficulties, especially at low loads, speeds, and during engine startup, due to its high ignition energy requirement and long ignition delay. Even with modifications such as increased compression ratio, and the addition of intake heaters and glow plugs, sustaining combustion at low load conditions remains a challenge. However, once the engine is warmed up, methanol combustion can be sustained at medium to high loads without additional heating accessories, although the use of such accessories improves combustion stability.

An ex-situ investigation of the effect of clamping pressure on the membrane swelling of a polymer electrolyte water electrolyzer using X-Ray tomography

Due to water uptake, the polymer membrane of polymer electrolyte membrane water electrolyzers (PEMWE) swells, increases in thickness and so induces swelling pressure. The water content in the membrane and catalyst coated membrane (CCM), respectively, defines the protonic conductivity, which has a significant impact on the performance of a PEMWE. In order to ensure the gas tightness of the PEMWE and increase the thermal and electrical connectivity between the different layers, the entire electrolyzer is compressed. Whether and in which way the swelling of the CCM is influenced by applying pressure or influences the surrounding layers is investigated in this study using a special compression device and X-ray computer tomography (CT). CT scans were carried out and the resulting cross-sectional images analyzed. Five different compression pressures between 0.36 and 1.63MPa were applied for the dry (28°C, atmospheric humidity) and wet (28°C, surrounded by liquid water) states. The thickness change of the CCM and adjacent porous transport layers (PTL) was then measured. Due to the compression pressure, the thickness of the CCM decreased by 5%. For lower pressures, the carbon paper PTL compensates more of the swelling than the titanium felt PTL. For higher pressures, the ratio is inverse.

An Axi-Symmetric Problem of Suspensions Filtering with the Formation of a Cake Layer

In this paper, we consider a vertically positioned cylindrical filtering element. Filtering occurs in the radial direction, therefore, the direction of the velocities of the liquid and suspended particles coincide with this radial direction. The flow can be considered to be one-dimensional and radially axisymmetric. To describe such a filtering process, the axisymmetric Stefan problem will be formulated. The radial mass balance formalism and Darcy’s law are utilized to obtain a basic equation for cake filtration. The boundary condition at the moving surface is derived and the cake filtration is formulated in a Stefan problem. Equations are derived that describe the dynamics of cake growth in the cake filtration, and they are numerically solved. The influence of different model parameters on the compression and fluid pressure across the cake and the growth of its thickness are studied.

An ex vivo preliminary investigation into the impact of parameters on tissue welding strength in small intestine mucosa-mucosa end-to-end anastomosis.

Background: Tissue welding is an electrosurgical technique that can fuse tissue for small intestine anastomosis. However, limited knowledge exists on its application in mucosa-mucosa end-to-end anastomosis. This study investigates the effects of initial compression pressure, out-put power, and duration time on anastomosis strength ex vivo in mucosa-mucosa end-to-end anastomosis. Methods: Ex vivo porcine bowel segments were used to create 140 mucosa-mucosa end-to-end fusions. Different experimental parameters were employed for fusion, including initial com-pression pressure (50kPa-400kPa), output power (90W, 110W, and 140W), and fusion time (5, 10, 15, 20s). The fusion quality was measured by burst pressure and optical microscopes. Results: The best fusion quality was achieved with an initial compressive pressure between 200 and 250kPa, an output power of 140W, and a fusion time of 15s. However, an increase in output power and duration time resulted in a wider range of thermal damage. There was no significant difference between the burst pressure at 15 and 20s (p > 0.05). However, a substantial increase in thermal damage was observed with longer fusion times of 15 and 20s (p < 0.05). Conclusion: The best fusion quality for mucosa-mucosa end-to-end anastomosis ex vivo is achieved when the initial compressive pressure is between 200 and 250kPa, the output power is approximately 140W, and the fusion time is approximately 15s. These findings can serve as a valuable theoretical foundation and technical guidance for conducting animal experiments in vivo and subsequent tissue regeneration.

Performance comparison of one cylinder combustion engine with variations of compression pressure &amp; octane number gasoline

Nowadays, automobiles and motorcycles manufacturer produced more powerful and efficient engines. This engine usually has high compression pressure to achieve high performance and economic gasoline consumption. Unfortunately, only few people known that high compression engine requires high octane number gasoline. The aim of this research were to find out the differences of power &amp; torsion output of one cylinder combustion engine which given several compression pressure variances using Pertamax &amp; Pertamax racing gasoline. Dynamometer test has been carried out to find the performance difference of one cylinder combustion engine. The results shown that the highest compression pressure engine (11,8 Kg/cm2) using Pertamax racing gasoline (RON 100) produced highest power output at 7,8 KW with torsion output at 10 Nm. Meanwhile, the lowest compression pressure engine (10 Kg/cm2) using Pertamax gasoline (RON 92) produced lowest power output at 4,2 KW with torsion output at 3,8 Nm.

A Data-Driven Approach to Predicting Tablet Properties after Accelerated Test Using Raw Material Property Database and Machine Learning.

The purpose of this study was to develop a model for predicting tablet properties after an accelerated test and to determine whether molecular descriptors affect tablet properties. Tablets were prepared using 81 types of active pharmaceutical ingredients, with the same formulation and three different levels of compression pressure. The tablet properties measured were the tensile strength and disintegration time of tablets after two weeks of accelerated test. The material properties measured were the change in tablet thickness before and after the accelerated test, maximum swelling force, swelling time, and swelling rate. The acquired data were added to our previously constructed database containing a total of 20 material properties and 3381 molecular descriptors. The feature importance values of molecular descriptors, material properties and the compression pressure for each tablet property were calculated by random forest, which is one type of machine learning (ML) that uses ensemble learning and decision trees. The results showed that more than half of the top 25 most important features were molecular descriptors for both tablet properties, indicating that molecular descriptors are strongly related to tablet properties. A prediction model of tablet properties was constructed by eight ML types using 25 of the most important features. The results showed that the boosted neural network exhibited the best prediction accuracy and was able to predict tablet properties with high accuracy. A data-driven approach is useful for discovering intricate relationships hidden within complex and large data sets and predicting tablet properties after an accelerated test.

Thermal transport characteristics of diamond under stress

Diamond exhibits extremely high hardness and thermal conductivity, which makes it widely used in industrial fields such as diamond cutting tools and piezoelectric materials. At the same time, during the diamond applications, the internal characteristics and thermal transport properties of diamond will change under high stress, which has an important impact on its service life and device accuracy. However, the internal properties and thermal transport response of diamond under high stress have not been systematically studied. This paper employed first-principles software to investigate the reaction of the diamond lattice structure, electronic properties, lattice vibration properties, thermodynamic properties, lattice thermal conductivity, phonon group velocity, and phonon free path when subjected to uniaxial compressive stress, shear stress, and hydrostatic pressure. The results show that at a stress of 120 GPa, the response of diamond exhibited distinct anisotropic properties in three kinds of stress states. Changes occur in the position of the carbon atoms, CC bond length, and CC bond angle within the diamond structure when subject to the three kinds of stress fields. The main reason for the above phenomenon is that the stress caused the redistribution of charges around the C atoms in the diamond. Furthermore, the symmetry of the diamond crystal was broken, and the diamond lattice vibration properties undergone alteration, leading to a state of dynamic instability. The thermodynamic properties and phonon group characteristics of diamond changed, and the lattice thermal conductivity of diamond is 2380, 99, and 806 W·m-1K-1, respectively. This theoretical study offers valuable insights into the impact of stress fields on the heat transfer properties of diamonds, providing practical guidance for their use in high-stress environments.

Molecular Ferroelectric Based Biocompatible Flexible Piezoelectric Pressure Sensor

This paper presents a biocompatible flexible pressure sensor fabricated by employing a biocompatible organic ferroelectric, namely, single protonated 1,4-diazabicyclo[2.2.2]octane fluoroborate ([Hdabco]BF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) embedded in poly(vinylidene fluoride) (PVDF) polymer. The presented device generated an output voltage of 6.5 V, which is more than twice the voltage generated by pristine polymeric device. When used as pressure sensor, the device showed a high sensitivity of 0.4 V/kPa and a linear response for external compressive pressures that ranged between 1.6 kPa to 12.8 kPa. These results demonstrate that [Hdabco]BF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> @ PVDF composite is a promising material for applications such as wearable electronics where biocompatible and self-powered sensors are much needed.

Uncovering the effects of local pressure and cooling rates on porosity formation in AA2060 Al-Li alloy

The third generation of Al-Li alloys (e.g. AA2060) have been widely used in aerospace engineering. The formation of porosity during casting is a major obstacle for improving its mechanical properties due to the 10 times the equilibrium hydrogen concentration in the liquid than the traditional aluminum alloys. In this study, the effects of two fundamental parameters are investigated: cooling rate and pressure on the formation of porosity. The centrifugal casting process was used to apply external pressure during solidification and quantify the 3D porosity morphology as a function of the external parameters using X-ray computed tomography (X-CT). Subsequently, a Cellular Automata (CA) model was used to predict porosity as a function of pressure and thermal boundary conditions. It was found that the externally applied compressive pressure contributes to porosity closure within certain limits. In addition, the cooling rate not only refines the grain size but also minimizes porosity defects by increasing their number density, and the experimental results validated the predictions by the CA model. By increasing the solidification pressure and cooling rate, a high-performance AA2060 Al-Li alloy with a tensile strength of 490 MPa and an elongation of 6.1% was obtained.

Measurement of gastric wall thickness after laparoscopic sleeve gastrectomy: obesity comorbidities and gastric wall in Chinese patients with obesity.

Leakage of the sleeve remains constant after laparoscopic sleeve gastrectomy (LSG). This complication may be due to a mismatch between the staple height and gastric wall thickness (GWT). Our aim was to measure the GWT in Chinese patients with obesity and investigate the relationship between GWT and gender, body mass index (BMI), body weight, and obesity-related comorbidities. The GWT of 210 resected specimens after LSG was measured using a tissue measuring device, at a compression pressure of 8g/mm2 at three predetermined locations: antrum, midbody, and fundus. Two hundred ten patients (171 female/39 male). The gastric wall was thickest at the antrum followed by the midbody and thinnest at the fundus (3.02mm, 2.22mm, and 1.6mm, respectively). Patients with gastritis and those with reflux esophagitis had thicker GWT at the antrum; male had thicker GWT at the antrum and fundus; patients with body weight > 100kg, and those with BMI > 40kg/m2 had thicker GWT at the fundus. Linear regression analysis revealed a significant association between GWT with body weight and BMI at the antrum and fundus; Furthermore, hypertension associated with the GWT at the fundus (P < 0.01, P < 0.01, P < 0.02, P < 0.01; and P < 0.04, respectively). This study showed that the anatomical location of the gastric wall is a major predicting factor of GWT. Furthermore, gastritis, reflux esophagitis, male gender, BMI > 40kg/m2, body weight > 100kg, and hypertension may increase the GWT at the antrum and fundus in Chinese patients with obesity.

Calculation and analysis of optimal layer density for variable density multilayer insulation based on layer by layer model and Lockheed equation

The extremely high energy density and carbon-free characteristics of liquid hydrogen (LH2) make it suitable for replacing liquefied natural gas (LNG) as a future energy commodity. However, the extremely low evaporation temperature of LH2 results in high heat leakage. Multilayer insulation (MLI), which is the most thermally efficient insulation system known, is widely used in the fields of hydrogen energy, aerospace, and other cryogenic fields. Variable density multilayer insulation (VDMLI), which has emerged in the last two decades, has improved the performance of MLI by adding spacers to change the density of MLI. However, there has been no significant progress in the optimization theory for VDMLI. In this paper, based on the layer by layer model and the Lockheed equation, a generalized optimal layer density calculation model for VDMLI is established by considering the influences of spacers, compressive pressure, gas pressure, etc. The results indicate that compared to general VDMLI and MLI on liquid hydrogen tanks, the optimal layer density VDMLI (OVDMLI) can reduce heat leakage by 21.1% and 25.3%, respectively. After comparison and analysis, the characteristics and reasons for temperature and heat transfer conductivity profiles of MLI, VDMLI, and OVDMLI are pointed out. The effect of the spacer number on heat flux and spacer profile is analyzed. Additionally, gas pressure profile and heat transfer are investigated with consideration given to the vacuum degree at both boundaries.

Measurement and Simulation of Autoignition-Assisted Flame Speed of N-Heptane Mixture at Elevated Gas Temperature

Laminar flame speed and autoignition are two fundamental characteristics of a hydrocarbon’s combustion. These two characteristics are extensively studied due to their importance in designing and developing combustion systems. However, a regime in which these two characteristics simultaneously affect the combustion process is not well understood. Thus, the primary focus of this investigation is to understand the autoignition-assisted flame regime prior to the first-stage heat release. The premixed mixture of n-heptane in oxygen–nitrogen–diluent at an equivalence ratio of 1.0, a compressed gas pressure of 6.85 bar, and compressed gas temperatures of 621 K (when using argon) and 616 K (when using helium) were studied in this work. At these initial conditions, the mixture ignition delays are 32.31 ms (using argon) and 53.92 ms (using helium). The flame-propagating images were recorded using a high-speed camera at different spark ignition times to measure the flame locations. The Rapid Compression Machine─Flame (RCM-Flame) apparatus was used to perform experiments, and one-dimensional modeling and three-dimensional numerical modeling were performed. The simulations provided data to understand the effect of stretch on the measured spherical burning velocity. The measured and simulated autoignition-assisted laminar flame speeds were in excellent agreement, the linear method can be used to remove the stretch from the spherical burning velocity, and the autoignition-assisted flame speeds show a negligible dependency on the spark ignition times when the first-stage heat release is negligible.

Effects of non-uniform needled microstructure on failure mechanisms of 3D needled composites thick-walled cylinder under axial compression and internal pressure

Effects of non-uniform needled microstructure on failure mechanisms of 3D needled composites thick-walled cylinder under axial compression and internal pressure

A Narrative Review of Patellar Resurfacing Versus Non-resurfacing in Total Knee Arthroplasty.

The number of individuals who experience the symptoms of gonarthrosis rises proportionally as life expectancy rises and the population becomes more active. The purpose of total knee arthroplasty (TKA) is to lessen pain and restore knee function, and it has a high success rate. The restoration of patellar tracking in addition to the proper alignment of the femoral and tibial components contributes to the success of the arthroplasty and the patient's happiness. Replacement of the knee is not an easy process. One of the major objectives of total knee replacement is to achieve the proper rotation of the femoral components. A critical step that affects postoperative outcomes in total knee arthroplasty is the correct alignment of the femoral component. The axial plane of the femoral component is to blame for flexion stability, knee joint kinematics, flexion alignment, and patellar tracking. The patella is the largest sesamoid bone in the human body, and its major role is to enhance the quadriceps' moment arm, which allows the knee to expand. The distribution of patellofemoral compressive pressures during knee flexion and the centralization of the quadriceps muscles' multidirectional pull during extension are both critical functions of the patella. After primary knee arthroplasty, there are 8% more cases of anterior knee discomfort than there were before. Whether or not the patella was resurfaced, patients with primary TKA experience anterior knee discomfort. Patella baja is caused by excessive joint line elevation, which causes persistent overload and discomfort. The design of the TKR might have an impact on postoperative patellofemoral problems. After TKR, patellofemoral maltracking and patellar dislocation are often caused by surgical mistakes.

Dead-end forward osmosis as an alternative for deep sludge dewatering: Evaluation method and characteristics analysis

Sludge deep dewatering technologies that are effective and energy-saving are urgently required. Forward osmosis (FO) technology was recently used for dewatering sludge. However, the final moisture content was too high—above 95.0%—to meet the treatment and disposal requirements. In this study, a novel dead-end forward osmosis (DEFO) technique was proposed and verified for deep dewatering of excess sludge. In DEFO, the feed side is in dead-end mode, while the draw side is in cross-flow mode. Further, when 30.8 g/L excess sludge, 2.0 M NaCl draw solute, 3.0 cm/s cross velocity on the draw side, and 3‰ cationic polyacrylamide dosage was used, the moisture content of the filter cake was as low as 69.2%, equating to 90.0% sludge reduction. A proposed evaluation model for DEFO sludge dewatering behavior includes critical characteristics, such as water flow osmosis resistance and water permeability coefficient of the FO membrane. The sludge dewatering process continued regardless of whether the filter cake broke. In contrast to the conclusions endorsed in traditional dead-end pressure filtration, the DEFO filter cake exhibits an abnormal structure with a dense upper cake and a loose structure for the lower cake, resulting in a permeable filter cake. The photographs, moisture content distribution, and filter cake frozen scan verified this. The solid compressive pressure and hydraulic pressure in the DEFO filter cake were negligible, resulting in low water flow resistance of the filter cake. These findings provide further insights into the use of DEFO technology for deep sludge dewatering.

Speed and torque control of pneumatic motors using controlled pulsating flow

Pneumatic motors have several advantages and have many robotics and automation applications. The importance of the study is that it is a cheap and possible way to apply it to the fixed displacement pneumatic motors with simple directional control valve used. The purpose of the addition to any traditional pneumatic motors is to change the fixed displacement pneumatic motor to be variable speed and torque compared to the expensive systems such as the proportional control valve in many industrial applications. The study also included validated simulations using the Automation Studio program to control the pneumatic motor’s speed and torque. In addition, the results showed remarkable success in controlling the pneumatic motor outputs depending on the frequency of the compressed air-source pulses and pressure. The pulsating air frequencies of 1.5, 3, and 4.5 Hz were considered at different inlet source pressure changes from 1.72, 3.45, and 5.17 bar. As the pulsating flow frequency of compressed air decreased from 4.5, 3, and 1.5 Hz, the motor pressure and torque decreased. Furthermore, empirical correlations related to frequency and pressure effect have been developed. The error is 6.3–9.5% in predicting the motor speed and torque outputs. The limitation of the proposed method in real-life applications is about a maximum of 7.5 bar. On the other hand, the frequency is limited to 9 Hz using a mechanical solenoid.

Inducing Fiber Entanglement to Achieve Realistic Tow Fiber Volume Fractions in Textile Reinforced Composite Models

Meso-scale modeling can be an effective way to predict textile-reinforced composite performance when the geometry of the textile is known. Digital element fiber models can be used to obtain the geometry of the textile reinforcement, but these are frequently too compact because the fibers are parallel within a tow and do not provide as much resistance to compaction as tows with fiber entanglement found in textiles. A novel entanglement simulation procedure was created to obtain more realistic textile geometry. By combining artificial fiber entanglement with manufacturing process simulation, a method was developed to create fiber bundle models using entanglement to control the compaction behavior. To introduce fiber entanglement into a tow, select fibers are swapped with each other in the tow at a cross-section. This allows entanglement to be introduced after the basic textile structure is already made, and prevents individual fibers from leaving the tow and getting entangled into neighboring tows. This fiber entanglement process was controlled by three parameters, which dictate how many, how often, and how far away from each other fibers are swapped. A parametric study was conducted which showed that the entanglement within a fiber bundle could be used to control the compaction pressure versus fiber volume fraction response of the bundle. The method was then applied to a woven textile model where it was found that increasing the amount of entanglement within the tows increased the pressure required to compact the textile to the desired thickness. This method for artificial fiber entanglement and manufacturing process simulation shows the potential to be able to predict the entanglement required to create fiber bundles using a desired mold compression pressure to achieve a desired compaction behavior.

A general scaled model design method of stiffened plate subjected to combined longitudinal compression and lateral pressure considering the ultimate strength and collapse modes

A general and efficient scaled method for stiffened plates subjected to combined longitudinal compression and lateral pressure is proposed based on slenderness, simply by adjusting the number of stiffeners. The design method makes it easier to determine the dimensions of the scaled model for a given scale ratio compared with the previously proposed method. The emphasis is on the influence of the plate slenderness, the column slenderness, and the non-dimensional parameter of the lateral pressure on the ultimate strength. By maintaining the consistency of the plate slenderness and column slenderness, the proposed method is applicable for designing scaled models with materials of different yield stresses and Young's moduli. A similar effect of the lateral pressure on the ultimate strength of the prototype and scaled models is achieved by maintaining the non-dimensional parameter. In addition, the applicability of the scaled method to the initial deflection is considered, which provides a reference for similar models. The similitude of the scaled method is verified for several typical buckling modes, including the beam–column, tripping, web and overall collapse modes. Given the numerical results, the proposed general and fast scaled method can provide reasonable dimensions of scaled stiffened plates subjected to combined loads.

A wing-structured sensor with multiple mechanical stimuli differentiation capabilities toward multifunctional applications

Wearable sensing electronics capable of detecting and differentiating multiple mechanical stimuli are promising devices in the applications of healthcare monitoring, robotics, etc. However, most wearable sensors are developed for detecting only uniaxial mechanical stimuli, which severely hinders their practical applications that usually involve complex mechanical stimuli. Here, a wing-like multifunctional sensor (WMS) consisting of pressure sensing module in the middle and stretching sensing module in both wings is developed with the capability of detecting and differentiating pressure, stretching, convex and concave bending through distinct electrical signals variation trends. The hierarchical in-situ filling porous as pressure sensing layer and micro-wrinkled carbon nanotubes (CNTs)/Ag nanoflakes as stretch sensing layer achieve high sensitivity over a broad range in both pressure (sensitivity of 0.25 kPa−1 at 500 kPa) and strain sensing (Gauge factor of 140 at 150%). The pressure and stretch sensing module can work without interfering with each other, which is realized by structural design of lower Young’s modulus stretch sensing module and higher thickness and compressibility pressure sensing module. Then WMS is demonstrated in accurate detection of human kinesthesia, human-computer interface, identification of objects of various hardnesses and sizes by robotic gripper, and perception of environmental information through a crawling robot.

Intergranular Hotspots: A Molecular Dynamics Study on the Influence of Compressive and Shear Work

Numerous crystal- and microstructural-level mechanisms are at play in the formation of hotspots, which are known to govern high explosives initiation behavior. Most of these mechanisms, including pore collapse, interfacial friction, and shear banding, involve both compressive and shear work done within the material and have thus far remained difficult to separate. We assess hotspots formed at shocked crystal–crystal interfaces using quasi-1D molecular dynamics simulations that isolate effects due to compression and shear. Two high explosive materials are considered (TATB and PETN) that exhibit distinctly different levels of molecular conformational flexibility and crystal packing anisotropy. Temperature and intramolecular strain energy localization in the hotspot are assessed through parametric variation of the crystal orientation and two velocity components that respectively modulate compression and shear work. The resulting hotspots are found to be highly localized to a region within 5–20 nm of the crystal–crystal interface. Compressive work plays a considerably larger role in localizing temperature and intramolecular strain energy for both materials and all crystal orientations considered. Shear induces a moderate increase in energy localization relative to unsheared cases only for relatively weak compressive shock pressures of approximately 10 GPa. These results help isolate and rank the relative importance of hotspot generation mechanisms and are anticipated to guide the treatment of crystal–crystal interfaces in coarse-grained models of polycrystalline high-explosive materials.