Charge Pressure Research Articles

Relationship between the Chemiluminescence Intensity Ratio of C2* and CH*, Charge Pressure, and Equivalence Ratio for Gasoline

This work presents the results of an intensity-based fuel–air calibration for a range of charge pressures for gasoline fuel. The radical intensity ratio of diatomic carbon (C2*) to methylidene (CH*) was acquired through line-of-sight chemiluminescence imaging at pressures up to 10 bar. Certified gasoline (99% iso-octane, 0.9% n-heptane, and 0.1% other additives) and air are injected into an optically accessible pressure vessel capable of handling pressures up to 200 bar and ignited with an automotive spark plug. Line-of-sight images of C2* and CH* are recorded simultaneously on a single image sensor utilizing an intensifier, a high-speed camera, and various optical components to split the light signals associated with C2* and CH* (centered at 513 and 427 nm, respectively). The ratio of the signals (C2*/CH*) are acquired and compared to the measured equivalence ratio of the exhaust gases and charge pressure. The approach allowed for characterization of the behavior of the intensity ratio at various charge ...

Mathematical modeling, simulation and optimization of solar thermal powered Encontech engine for desalination

This paper investigates a solar driven external combustion and regenerative engine, which can be used for desalination of seawater by using gaseous working fluids. The effect of operating and design parameters on engine performance for different suction (Pc) and discharge (Ph) pumping pressures, hot (Th) and cold (Tc) space temperatures, regenerator effectiveness (εR), displacer full stroke length (X0) and dead volume of hot (Xho) and cold (Xc0) spaces is studied in detail. Optimization of pumping discharge pressure based on energy and exergy performance for six different working fluids is simulated. The energetic and exergetic analysis is performed at steady state conditions for the proposed thermodynamic cycle. Predominantly, mass and energy balance equations are applied to optimize the effect of different operating (Th,Tc,Pc,Ph) and design (εR,Xh0,Xc0,X0) parameters on the output work and efficiencies. An open source SCILAB code is utilized to solve the derived equations for pressure, volume, temperature, mass, and heat loads. The simulation results provide profiles for energy efficiency, exergy efficiency, and optimization based on selected design and operating parameters. Obtained results show that for each charging pressure and hot space temperature, there is a different optimum discharge pressure and optimum hot temperature based on exergetic and energetic efficiency values. Besides, the net hydraulic work-output rises with the increase in the charged mass and displacer full stroke length. Simulation and thermodynamic analysis of proposed engine can be useful to design and select the optimum pumping heads for an accessible heat source and sink temperatures used for desalination to reduce the electricity consumption.

Study of charged anisotropic spherical collapse in f(𝒢) gravity

This paper studies the gravitational collapse of charged anisotropic spherical stellar objects in [Formula: see text] gravity. For this purpose, we derive dynamical equations by considering Misner–Sharp mechanism and explore physical impact of charge, anisotropy and effective pressure on the rate of collapse. We establish the relationship between matter variables, Weyl tensor and the Gauss–Bonnet (GB) terms. For constant value of [Formula: see text], it turns out that conformal flatness condition is no longer valid due to the effect of anisotropic factor in the present scenario. To obtain conformally flat metric, we impose the condition of isotropic matter distribution which provides energy density homogeneity and conformal flatness of the metric. We conclude that GB terms lead to decrease in the collapse rate due to their anti-gravitational effects.

The role of low air pressure in the variation of negative corona‐generated space charge in a rod to plane electrode

The corona-generated space charge may vary in different air pressures, and the quantitative law between the corona-generated space charge density and air pressure has never been investigated. This work utilised computational approaches to explore the role of air pressure in the variation of negative corona-generated space charge. A negative fluid model in which the air pressure could be varied was built up to calculate the charged-particle density and electric field under different applied voltages. The continuity equations were solved by flux corrected transport algorithm and the Poisson equation was computed by the successive over relaxation method. The variations of important parameters due to air pressure were analysed. The particles densities of electrons, positive ions and negative ions at standard and low atmosphere pressures were computed, which increased markedly due to the decrease of atmosphere pressure. At fixed applied voltages, the exponential decay law between the maximal values of electron/positive ion densities at the head of the streamer and air pressure could be obtained. The quantitative law between the maximal values of electron/positive ion densities at the head of the streamer and the applied voltage, relative air density was also achieved.

Thermodynamic and dynamic analysis of an alpha type Stirling engine and numerical treatment

In this study, the nodal thermodynamic and dynamic analysis of an alpha type Stirling engine driven by Scotch-yoke mechanism is presented. The nodal thermodynamic section of the analysis is performed via 15 nodal volumes. The temperature variations in nodal volumes are calculated by means of the first law of the thermodynamics given for the open systems. The pressures in all of the nodal volumes are assumed to be equal and calculated via Schmidt relation. The momentary masses in nodal volumes are calculated via the perfect gas relation. The dynamic section of the analysis involves the motion equations of pistons and crankshaft. The motion equations are derived by means of the Newton method. In the derivation of the motion equations of pistons, the working fluid forces and friction forces are considered beside the inertia forces. In the derivation of motion equation of the crankshaft, moments of working fluid forces, moments of friction forces, the moment of external load and the moment of starter motor are considered as well as mass inertia moments. It is estimated that an engine having 1.8 L swept volume, 1000 K hot end temperature, 400 K cold end temperature, 3000 cm2 total inner heat transfer area, 5.1 bar charge pressure and 2000 W/m2 K inner heat transfer coefficient is capable of producing a shaft power above 2 kW. For these inputs and shaft power; the speed, speed fluctuation and torque are optimized as 138 rad/s, 16% and 14.9 N m respectively. The presented analysis is useful for engine development studies.

Rayleigh-Taylor instability in oscillating liquid pistons

In this study, an experimental apparatus is used to excite four U-tube-shaped liquid pistons connected in series, and to study their behaviour. Some of the gas spaces are heated to induce piston oscillations; in others, gas expansion is utilised to produce a refrigeration effect. It was discovered that the liquid piston surface would become unstable and turbulent at relatively low gas charge pressures (2 bar–3 bar). Cylindrical polyethylene floats were employed at each piston surface in order to reduce the area of the free surface of each piston and allow experiments to be conducted over a wide range of operating conditions. Experiments were carried out using gas charge pressures in the range of 1 bar–6 bar. The resulting liquid piston oscillations were measured and analysed to assess the impact of any developing piston instability. Evidence of a liquid piston acceleration limit, likely resulting from the Rayleigh-Taylor instability phenomenon, is consistently observed during the experiments. The use of submerged polyethylene piston floats is found to increase the surface stability and enable maximum accelerations of 25 ms−2 to 30 ms−2.

Lipid bilayer composition modulates the unfolding free energy of a knotted α-helical membrane protein

α-Helical membrane proteins have eluded investigation of their thermodynamic stability in lipid bilayers. Reversible denaturation curves have enabled some headway in determining unfolding free energies. However, these parameters have been limited to detergent micelles or lipid bicelles, which do not possess the same mechanical properties as lipid bilayers that comprise the basis of natural membranes. We establish reversible unfolding of the membrane transporter LeuT in lipid bilayers, enabling the comparison of apparent unfolding free energies in different lipid compositions. LeuT is a bacterial ortholog of neurotransmitter transporters and contains a knot within its 12-transmembrane helical structure. Urea is used as a denaturant for LeuT in proteoliposomes, resulting in the loss of up to 30% helical structure depending upon the lipid bilayer composition. Urea unfolding of LeuT in liposomes is reversible, with refolding in the bilayer recovering the original helical structure and transport activity. A linear dependence of the unfolding free energy on urea concentration enables the free energy to be extrapolated to zero denaturant. Increasing lipid headgroup charge or chain lateral pressure increases the thermodynamic stability of LeuT. The mechanical and charge properties of the bilayer also affect the ability of urea to denature the protein. Thus, we not only gain insight to the long-sought-after thermodynamic stability of an α-helical protein in a lipid bilayer but also provide a basis for studies of the folding of knotted proteins in a membrane environment.

Manufacturing and testing of an α-type Stirling engine

This paper presents construction and performance tests of an α-type Stirling engine. Experiments were performed within the range of 1–4 bars charge pressure with air and helium as the working fluid. The outer surface of the expansion cylinder was heated with an electrical heater within the range of heater temperature 800–1000 °C with 50 °C increments. The outer surface of the compression cylinder was cooled by circulating water. Heater temperature and charge pressure were assumed as operating parameters and the engine torque was measured for different engine speeds with air and helium. The engine produced a maximum power of 30.7 W at 437 rpm engine speed, at the heater temperature of 1000 °C and 3.5 bars charge pressure with helium. Engine torque increased with the increase of charge pressure up to 3 bar then started to decrease. By looking the point of engine speed range of the engine, 1000 °C hot end temperature and 3 bar charge pressure was the optimal values.

Design and test of the Stirling-type pulse tube cryocooler

Stirling type pulse tube cryocoolers are very attractive for cooling of diverse application because it has it has several inherent advantages such as no moving part in the cold end, low manufacturing cost and long operation life. To develop the Stirling-type pulse tube cryocooler, we need to design a linear compressor to drive the pulse tube cryocooler. A moving magnet type linear motor of dual piston configuration is designed and fabricated, and this compressor could be operated with the electric power of 100 W and the frequency up to 60 Hz. A single stage coaxial type pulse tube cold finger aiming at over 1.5 W at 80K is built and tested with the linear compressor. Experimental investigations have been conducted to evaluate their performance characteristics with respect to several parameters such as the phase shifter, the charging pressure and the operating frequency of the linear compressor.

Available pressure amplitude of linear compressor based on phasor triangle model

The linear compressor for cryocoolers possess the advantages of long-life operation, high efficiency, low vibration and compact structure. It is significant to study the match mechanisms between the compressor and the cold finger, which determines the working efficiency of the cryocooler. However, the output characteristics of linear compressor are complicated since it is affected by many interacting parameters. The existing matching methods are simplified and mainly focus on the compressor efficiency and output acoustic power, while neglecting the important output parameter of pressure amplitude. In this study, a phasor triangle model basing on analyzing the forces of the piston is proposed. It can be used to predict not only the output acoustic power, the efficiency, but also the pressure amplitude of the linear compressor. Calculated results agree well with the measurement results of the experiment. By this phasor triangle model, the theoretical maximum output pressure amplitude of the linear compressor can be calculated simply based on a known charging pressure and operating frequency. Compared with the mechanical and electrical model of the linear compressor, the new model can provide an intuitionistic understanding on the match mechanism with faster computational process. The model can also explain the experimental phenomenon of the proportional relationship between the output pressure amplitude and the piston displacement in experiments. By further model analysis, such phenomenon is confirmed as an expression of the unmatched design of the compressor. The phasor triangle model may provide an alternative method for the compressor design and matching with the cold finger.

Design of the glass pulse-tube cryocooler

With the purpose of generating the curiosity of the public, a pulse-tube cryocooler with regenerator, pulse-tube, inertance tube and reservoir made of glass has been designed constructed and operated. The dimensions of the glass regenerator have been determined using REGEN3.3 [1] from given parameters of the conductive porous medium inside of the regenerator and a 150K target cooling temperature at the cold head. The geometry of the glass pulse-tube and glass inertance tube has been fixed using an approximate design method [2], and the entire system parameters checked using SAGE [3]. The thickness of each glass component is based on a charge pressure of around 7 bar and a pressure ratio of about 1.35. The dimensions of the after-cooler are calculated using ISOHX [4] assuming a gas temperature of 300 K at the inlet of the regenerator.

High efficiency 40 K single-stage Stirling-type pulse tube cryocooler

A high efficiency single-stage Stirling-type coaxial pulse tube cryocooler (SPTC) operating at around 40 K has been designed, built and tested. The double-inlet and the inertance tubes together with the gas reservoir were adopted as the phase shifters. Under the conditions of 2.5 MPa charging pressure and 30 Hz operating frequency, the prototype has achieved a no-load temperature of 23.8 K with 330 W of electric input power at a rejection temperature of 279 K. When the input power increases to 400 W, it can achieve a cooling capacity of 4.7 W/40 K while rejecting heat at 279 K yielding an efficiency of 7.02% relative to Carnot. It achieves a cooling capacity of 5 W/40 K with an input power of 450 W. It takes 10 minutes for the SPTC to cool to its no-load temperature of 40 K from 295 K.

The study on a gas-coupled two-stage stirling-type pulse tube cryocooler

A two-stage gas-coupled Stirling-type pulse tube cryocooler (SPTC) driven by a linear dual-opposed compressor has been designed, manufactured and tested. Both of the stages adopted coaxial structure for compactness. The effect of a cold double-inlet at the second stage on the cooling performance was investigated. The test results show that the cold double-inlet will help to achieve a lower cooling temperature, but it is not conducive to achieving a higher cooling capacity. At present, without the cold double-inlet, the second stage has achieved a no-load temperature of 11.28 K and a cooling capacity of 620 mW/20 K with an input electric power of 450 W. With the cold double-inlet, the no-load temperature is lowered to 9.4 K, but the cooling capacity is reduced to 400 mW/20 K. The structure of the developed cryocooler and the influences of charge pressure, operating frequency and hot end temperature will also be introduced in this paper.

Spin-dependent balance equations in spintronics**Project supported by the National Natural Science Foundation of China (Grant No. 11274378), the Key Research Program of the Chinese Academy of Sciences (Grant No. XDPB08-3), and the MOST of China (Grant No. 2013CB933401).

It is commonly known that the hydrodynamic equations can be derived from the Boltzmann equation. In this paper, we derive similar spin-dependent balance equations based on the spinor Boltzmann equation. Besides the usual charge current, heat current, and pressure tensor, we also explore the characteristic spin accumulation and spin current as well as the spin-dependent pressure tensor and heat current in spintronics. The numerical results of these physical quantities are demonstrated using an example of spin-polarized transport through a mesoscopic ferromagnet.

A study on performance of a liquid air energy storage system with packed bed units

Energy storage is a key technology required to manage intermittent or variable renewable energy, such as wind or solar energy. In this paper a concept of an energy storage based on liquid air energy storage (LAES) with packed bed units is introduced. First, the system thermodynamic performance of a typical cycle is investigated and temperature distribution in cold boxes is discussed. Then, the effects of inlet temperature of cold boxes, charge and discharge pressures on thermal behaviors of LAES system are analyzed, as well as the system round-trip efficiency. Finally, an overall comparison between this LAES system and an adiabatic compressed air energy storage (A-CAES) system is conducted. The system could achieve a round-trip efficiency in the range 50–62% depending on the values of process conditions. The system round-trip efficiency decreases with the increase of cold box inlet temperature, and increases with the rise of charge and discharge pressures. Although the round-trip efficiency of the present LAES system is a bit lower than the A-CAES system, however, the air storage volume decreases and the air storage energy density (ASED) increases remarkably for the same operational conditions. The main conclusions draw from this work is beneficial for future LAES development in particular the combination with the packed bed units and the fit with the requirements for large-scale energy storage.

Taguchi-based combined grey relational and principal component analyses for multi-response optimization of diesel engines

PurposeDiesel engine can produce power more efficiently with lower exhaust emissions when operated at optimum input parameter settings. To achieve this goal, the purpose of this paper is to optimize the input parameters of diesel engine which will lead to optimum performance and exhaust emissions.Design/methodology/approachTo achieve the goal of improving diesel engine performance and exhaust emissions, four input parameters were considered in the study. Five different levels of each input parameter were taken. Four response variables under no load, half load and full load conditions were recorded. Experiments were performed in random manner according to selected Taguchi L25 orthogonal array. The data were analyzed using grey relational analysis coupled with principal component analysis. Analysis of S/N ratio was performed to obtain the optimum combination of input parameters. The grey relational grade at optimum setting of the input parameters was obtained by regression analysis.FindingsResults of the current research work give the optimum input parameter settings for no load, half load and full load conditions of diesel engine. Engine produces power more efficiently with low exhaust emissions when operated at these optimum settings.Practical implicationsIn view of the compliance to the stringent air pollution norms of the nations and fast depleting fossil fuels, it is of the utmost importance to design and operate the engine in the optimum range of its input parameters so that it produces more power with low exhaust emissions. This paper aims at optimizing input parameters of diesel engine to improve performance and exhaust emissions. Results of the study presented in this paper are significantly useful for diesel engine-related researchers and professionals.Originality/valueFrom the literature review, it appears that only few researchers have conducted studies pertaining to the optimization of the input parameters of diesel engine to improve performance or exhaust emissions. Although few studies related to the optimization of compression ratio, fuel injection timing, fuel injection pressure and air pressure have been reported, no work related to optimization of temperature and pressure of turbocharged air has been reported. Therefore, the main focus of the current research work is on optimizing the charge air temperature and pressure with respect to performance and exhaust emissions.

An efficient miniature 120 Hz pulse tube cryocooler using high porosity regenerator material

A 1.22 kg coaxial miniature pulse tube cryocooler (MPTC) has been fabricated and tested in our laboratory to provide cooling for cryogenic applications demanding compactness, low mass and rapid cooling rate. The geometrical parameters of regenerator, pulse tube and phase shifter are optimized. The investigation demonstrates that using higher mesh number and thinner wire diameter of stainless steel screen (SSS) can promote the coefficient of performance (COP) when the MPTC operates at 120 Hz. In this study, the 604 mesh SSS with 17 μm diameter of mesh wire is constructed as filler of regenerator. The experimental results show the MPTC operating at 120 Hz achieves a no-load temperature of 53.5 K with 3.8 MPa charging pressure, and gets a cooling power of 2 W at 80 K with 55 W input electric power which has a relative Carnot efficiency of 9.68%.

Hot surface pre-ignition in direct-injection spark-ignition engines: Investigations with Tailor-Made Fuels from Biomass

Two promising alternative fuel candidates for spark-ignition engines, 2-butanone and 2-methylfuran, have been identified in the context of the Cluster for Excellence ‘Tailor-Made Fuels from Biomass’. To further explore the potential of these fuels for spark-ignition engine application, experimental and numerical investigations into the occurrence of the abnormal combustion phenomenon of hot surface–induced pre-ignition have been conducted, with pure ethanol, RON97 E10, and pure iso-octane as reference fuels. For the experimental investigations, a single-cylinder engine with a compression ratio of 11, equipped with a glow-plug to create a hot spot in the cylinder, was operated at 1500 r/min and 1500 mbar charge pressure. Each fuel was tested with several glow-plug temperatures until a minimum pre-ignition frequency of 2% was observed. The results show that 2-methylfuran reaches its 2% pre-ignition frequency at a glow-plug temperature of 880 °C, which is 16 °C higher than the 2% pre-ignition frequency of ethanol at 864 °C and 10 °C less than RON97 E10 with 890 °C. Iso-octane showed the lowest pre-ignition resistance with a 2% pre-ignition frequency at a glow-plug temperature of 853 °C, and 2-butanone was most resistant against pre-ignition in this study with a 2% pre-ignition frequency at 932 °C. Further numerical investigations, including zero-dimensional ignition delay time calculations and three-dimensional computational fluid dynamics simulations, revealed a clear connection between the surface ignition frequency of these fuels and their reaction kinetics.

Kinematic difference between a biological cell and an artificial vesicle in a strong DC electric field \u2013 a \u201cshell\u201d membrane model study

BackgroundCellular biomechanics can be manipulated by strong electric fields, manifested by the field-induced membrane deformation and migration (galvanotaxis), which significantly impacts normal cellular physiology. Artificial giant vesicles that mimic the phospholipid bilayer of the cell membrane have been used to investigate the membrane biomechanics subjected to electric fields. Under a strong direct current (DC) electric field, the vesicle membrane demonstrates various patterns of deformation, which depends on the conductivity ratio between the medium and the cytoplasm. The vesicle exhibits prolate elongation along the direction of the electric field if the cytoplasm is more conductive than the medium. Conversely, the vesicle exhibits an oblate deformation if the medium is more conductive. Unlike a biological cell, artificial vesicles do not migrate in the strong DC electric field.To reconcile the kinematic difference between a cell and a vesicle under a strong DC electric field, we proposed a structure that represents a low-conductive, “shell-like” membrane. This membrane separates the extracellular medium from the cytoplasm. We computed the electric field, induced surface charge and mechanical pressure on the fixed membrane surface. We also computed the overall translational forces imposed on the structure for a vesicle and a cell.ResultsThe DC electric field generated a steady-state radial pressure due to the interaction between the local electric field and field-induced surface charges. The radial pressure switches its direction from “pulling” to “compressing” when the medium becomes more conductive than the cytoplasm. However, this switch can happen only if the membrane becomes extremely conductive under the strong electric field. The induced surface charges do not contribute to the net translational force imposed on the structure. Instead, the net translational force generated on the shell structure depends on its intrinsic charges. It is zero for the neutrally-charged, artificial vesicle membrane. In contrast, intrinsic charges in a biological cell could generate translational force for its movement in a DC electric field.ConclusionsThis work provides insights into factors that affect cellular/vesicle biomechanics inside a strong DC electric field. It provides a quantitative explanation for the distinct kinematics of a spherical cell verses a vesicle inside the field.

Dynamic balancing and experience during the development of a single cylinder Beta-configuration Stirling engine using rhombic drive

The present work starts with analysis, and culminates in the development of engine. Hydrogen is selected as working fluid due to its favorable thermodynamic and thermo-physical properties. During fabrication and sub-assembly engine was run by electrical motor as in motoring test. It provided cooling at the cylinder head and confirmed that all the system components were performing well under low charge pressure. Dynamic balancing analysis is done to eliminate unbalanced couple. The same was included in the system by removal of pre-decided part of the gears which also acted as the flywheel. The engine performance was demonstrated by operating the centrifugal pump. LPG burner assembly designed, especially for this Stirling engine, is successfully demonstrated. Preliminary trials for approximately 3–5 min, with loading condition in engine mode, with LPG were conducted. The flame temperature near the cylinder head was maintained at about 1100 K. It needs to be ensured that uniform but sufficient heat input should be provided. In short, an experimental set-up is built in accordance with geometrical dimensions specified in the theoretical design. Theoretically predicted performance and experimental results have been compared and validated for the developed unit for a particular set of operating parameter with H2.