Miniature Pressure Transducers Research Articles

Experimental investigation of instantaneous lift on NACA 0018 airfoil section due to a non-harmonic pitching motion

In this study, we explore the problem of an airfoil in a harmonic and arbitrary periodic pitching motion and seek to understand how theoretical estimation with first-order potential theory match experiments. We adopt Jones’ approximation for the Wagner function for lift computations in the time domain and Theodorsen’s model in the frequency domain. We experimentally investigate a two-dimensional symmetric NACA 0018 airfoil in pitching motion under attached flow with reduced frequencies up to 0.25 and Reynolds number varying from 1.5×105 to 3×105. To eliminate the influence of the laminar separation bubble, free-stream turbulence intensity was elevated above the baseline level by placing turbulence generating grid, thus, obtaining better compatibility between the flow conditions in the experiments and the theoretical assumptions. Time-resolved sectional lift is determined by simultaneous static pressure measurement with miniature pressure transducers. The transient response is captured with accuracy in the time domain by quantifying the non-circulatory contribution. Excellent agreement is achieved in the time and frequency domains due to the highly accurate measurement of the instantaneous magnitude and phase of the time-resolved surface pressures. We further explore the applicability of the theory for high-pitching amplitudes, which results in a temporary deviation of the measured lift from the theoretical predictions. As the frequency domain unsteady theory is more widely studied than its time domain counterpart, this study provides a unique opportunity to highlight the significance of time-domain analysis in estimating instantaneous lift in non-harmonic motion.

Abstract 14769: Peripheral Venous Pressure Measured With a Novel Miniature Pressure Transducer Correlates With Central Venous Pressure in Heart Failure, Heart Transplant, and Left Ventricular Assist Device Patients

Introduction: Peripheral venous pressure (PVP) has been shown to accurately correlate with central venous pressure (CVP) when measured using a conventional manometer and pressure tubing. We investigated the correlation between PVP as measured by a novel pressure transducer and CVP in heart failure (HF), heart transplant (HTx), and left ventricular assist device (LVAD) patients. Methods: A prospective, cross-sectional study examining PVP from February 2022 to May 2023 was conducted. The analysis was limited to patients undergoing right heart catheterization (RHC) admitted for HF, post-HTx monitoring, or LVAD hemodynamic testing. PVP was transduced from an antecubital or more distal peripheral intravenous (IV) catheter site using a miniature digital, disposable pressure transducer (Centurion Compass Universal HG, Medline). Pressures were compared using Pearson’s correlation coefficient. Results: 99 patients were enrolled with a mean age of 62 ± 12 years and a mean ejection fraction (EF) of 41 ± 21%. 74% of the patients had heart failure, 17% were HTx patients, and 9% were LVAD patients. The PVP measured with the novel pressure transducer was found to be highly correlated to CVP measured by RHC (r=0.80, p < 0.0001) (Figure). High correlation was also noted when broken down by HF (r=0.77, p < 0.0001), HTx (r=0.95, p < 0.0001), and LVAD groups (r=0.90, p < 0.0003). There was a high degree of correlation for HF patients with EF < 50% (r=0.74, p < 0.0001) and EF > 50% (r=0.90, p < 0.0001). A high degree of correlation was found for all peripheral IV insertion sites: antecubital (r=0.86, p=0.000071), forearm (r=0.76, p<0.00001), and hand (r=0.84, p<0.00001). Conclusions: There is a high degree of correlation between PVP measured by a novel pressure transducer and CVP in HF, HTx, and LVAD patients. PVP measurements using this transducer are a reliable estimate of volume status in these patient populations.

Measurement of Excess Pore-Water Pressure in Frozen Soil at Subfreezing Temperatures Close to 0°C

Response of pore-water pressure has crucial effect on the engineering geological performance of permafrost ground. However, there is a dearth of literature on the measurement of pore-water pressure in frozen soils due to challenges with regard to technical and operational method. To validate the generation of pore-water pressure and to reveal its variation property in frozen soils at subfreezing temperatures close to 0°C, a miniature pressure transducer was utilized to conduct a number of confined compression tests. Double-wall structure avoided damage to the transducer during frozen soil sampling. The transducer at sample bottom perceived a pressure fluctuation as varying air pressure imposed on sample surface, proving the connectivity among the pores in frozen soils with a hysteretic effect on pressure transmission. Pore-water pressure experienced a progressive increase followed by a slow dissipation under invariable load and temperature conditions when water drainage was permitted, while a monotonic increase in pressure was observed for an undrained sample. With decreasing temperature, a smaller peak and a more dilatory dissipation were displayed. When the sample was exposed to a stepwise warming process, a similar performance for the pressure was obtained with abrupt rise at the turning point of temperature.

Experimental analysis of embankment on soft soil improved with bottom ash columns

Bottom ash is a byproduct formed during the combustion of coal and can be used as an alternative to aggregate and sand as a green material in columns to achieve sustainability in ground improvement. In this study, the bearing capacity performance of highway embankment models constructed on bottom ash columns reinforced soil was investigated. Model tests were carried out with various area replacement ratios (Ar) of 10.91 %, 16.37 % and 21.83 % and column length to diameter ratios (L/D) of 6 and 8. Load cell and three miniature pressure transducers were used for the measurement of vertical stress on the embankment surface, top and base of the column and adjacent soil surrounding the columns. A Pore pressure transducer was employed to record the excess-pore water pressure during the loading test. The stress concentration ratio and column failure modes were investigated for the stress transfer mechanism. The tests results revealed that bottom ash columns, whether floating or end bearing, was most effective in enhancing the ultimate bearing capacity (qult) of improved soil at almost 1.24, 1.39 and 1.63 times and 1.27, 1.42 and 1.83 times that of unreinforced soil for Ar of 10.91 %, 16.37 % and 21.83 % with L/D of 6 and 8, respectively. The stress concentration ratio (SCR) increased with higher Ar and L/D values. The highest improvement ratio was obtained for the model improved with bottom ash columns at Ar = 21.83 % and L/D = 8. The end-bearing bottom ash columns fail by bulging and floating bottom ash columns fail by bulging along with punching at the base. Furthermore, a mathematical expression with R2 = 0.9913 was developed for calculating the approximate qult. The approximate qult are in good agreement with actual qult. The findings of this study resulted in the utilization of bottom ash as a sustainable granular material in the column for the ground improvement underneath embankments.

Laboratory Measurements of the Impact of Fracture and Fluid Properties on the Propagation of Krauklis Waves

AbstractThe Krauklis wave is a slow dispersive wave, generated in fluid‐filled fractures. By analyzing the resonant frequency and quality factor of the Krauklis wave, the fracture dimension and fluid properties can be estimated. However, the accuracy of the estimation of fracture dimension and fluid properties depends on deciphering factors affecting the Krauklis wave such as fluid viscosity, fracture geometry, fracture compliance, and stiffness ratio, some of which have not been experimentally studied yet. We have developed an experimental apparatus to study the Krauklis wave within a trilayer model consisting of a pair of aluminum plates and a mediating viscous fluid layer. We utilize a piezoelectric source and miniature pressure transducers in our measurements. To evaluating the effects of the fracture aperture and fluid viscosity, we examine the impact of complex and realistic fracture geometry by introducing spatially varying aperture, surface roughness, and compliant partial surface contact provided by springs. The phase velocity, resonant frequencies, and quality factors (a) increase with the expansion of fracture aperture and (b) decrease with the increase of the fluid viscosity. Additionally, (c) phase velocity, resonant frequencies, and attenuation decrease with the increase of mechanical compliance. Furthermore, rough and wedge‐shaped fracture surfaces tend to slow down the Krauklis wave. Since the Krauklis wave is used by different disciplines such as volcanology, glaciology, and the petroleum industry to characterize fracture dimensions and properties of the fluids involved, our experimental findings can be used as a benchmark to develop comprehensive theoretical models to better interpret the Krauklis waves.

An Indirect Measurement Methodology to Identify Load Fluctuations on Axial Turbine Runner Blades.

Smooth integration of intermittent energy sources, such as solar and wind power, into the electrical grid induces new operating conditions of the hydraulic turbine by increasing the off-design operations, start/stops, and load variations. Therefore, hydraulic turbines are subject to unstable flow conditions and unfavorable load fluctuations. Predicting load fluctuations on the runner using indirect measurements can allow for optimized operations of the turbine units, increase turbine refurbishment time intervals, and avoid structural failures in extreme cases. This paper investigates an experimental methodology to assess and predict the flow condition and load fluctuations on a Kaplan turbine runner at several steady-state operations by performing measurements on the shaft in the rotating and stationary frame of references. This unit is instrumented with several transducers such as miniature pressure transducers, strain gages, and proximity probes. The results show that for any propeller curve of a Kaplan turbine, the guide vane opening corresponding to the minimum pressure and strain fluctuations on the runner blade can be obtained by axial, torsion, and bending measurements on the shaft. Torsion measurements on the shaft could support index-testing in Kaplan turbines particularly for updating the cam-curve during the unit operation. Furthermore, a signature of every phenomenon observed on the runner blade signals, e.g., runner frequency, rotating vortex rope components, and rotor-stator interaction, is found in the data obtained from the shaft.

Direct Evidence for Fluid Pressure, Dilatancy, and Compaction Affecting Slip in Isolated Faults

AbstractEarthquake instability occurs as a result of strength loss during sliding on a fault. It has been known for over 50 years that fault compaction or dilatancy may cause significant weakening or strengthening by dramatically changing the fluid pressure trapped in faults. Despite this fundamental importance, we have no real understanding of the exact conditions that lead to compaction or dilation during nucleation or rupture. To date, no direct measurements of pore pressure changes during slip in hydraulically isolated faults have been reported. We show direct examples of fluid pressure variations during nucleation and rupture using a miniature pressure transducer embedded in an experimental fault. We demonstrate that fluids not only are significant in controlling fault behavior but can provide the dominant mechanism controlling fault stability. The effect of fluid pressure changes can exceed frictional variations predicted by rate‐ and state‐dependent friction laws, exerting fundamental controls on earthquake rupture initiation.

Axillary intranodal pressure measurement: A complementary technique for detection of lymph node metastasis in breast cancer patients

Background: There is growing evidence that intranodal pressure (INP) can predict metastatic sentinel lymph nodes (SLNs). The objective of this study was to measure and utilize INP to evaluate the metastatic involvement of axillary SLNs in breast cancer patients. Materials and Methods: INP was measured in 73 clinically node-negative (cN0) breast cancer patients who were candidate for SLN biopsy. Clinical evaluation of the lymph node, coupled with frozen section analysis of the same excised SLN, was conducted. The level of suspicion (LOS) was used to assess the likelihood of metastases in the SLNs by the surgeons. Then, the miniature catheter tip pressure transducer was used to measure INP in the operation room. Finally, excised SLN was sent for permanent pathologic analysis as a gold standard for the evaluation of SLNs metastatic.Results: We identified the statistically significant increase in INP in nodes containing tumor metastasis in comparison with tumor-free SLNs (19.17 ± 13.63 vs. 8.82 ± 4.23) (P = 0.003). We considered the cutoff value for INP at 16 mmHg, which resulted in sensitivity of 80% and specificity of 87%. When the combination of INP above 16 mmHg and the LOS were taken into account for determining the likelihood of metastatic involvement of the LNs, the sensitivity and specificity were 87.5% and 91.7%, respectively. Conclusion: Our data suggest that INP measurement has the potential to help surgeons differentiate metastatic and nonmetastatic SLNs in combination with LOS. Meanwhile, it can be used along with frozen analysis to decrease false-negative rate.

Past Developments and Current Advancements in Unsteady Pressure Measurements in Turbomachines

The aim of this paper is to review, summarize, and record long-term experience with development and application of aerodynamic probes with built-in miniature pressure transducers for unsteady pressure measurement and industrial research in turbomachine components. The focus of the first half of the paper is on the work performed at VZLU Prague, Czech Republic (Secs. 3–8). The latest development in unsteady pressure measurement techniques and data reduction methodology suitable for future research in highly loaded, high-speed turbine engine components performed at NASA GRC Cleveland, OH, is reported in Secs. 8–15 of this paper. Excellent reviews of similar activities at ETH Zürich, Switzerland by Kupferschmied, et al. (2000, “Time-Resolved Flow Measurements With Fast-Response Aerodynamic Probes in Turbomachines,” Meas. Sci. Technol., 11(7), pp. 1036–1054) and at VKI Rhode-Sain-Genèse, Belgium by Sieverding, et al. (2000, “Measurement Techniques for Unsteady Flows in Turbomachines,” Exp. Fluids, 28(4), pp. 285–321) were already reported and are acknowledged here. A short list of reported accomplishments achieved by other researchers at various laboratories is also reported for completeness. The authors apologize to those whose contributions are not reported here. It is just an unfortunate oversight, not an intentional omission.

Investigation of self-pulsation characteristics for a liquid-centered swirl coaxial injector with recess

A combined experimental and numerical investigation was conducted to explore the self-pulsation characteristics generated by a liquid-centered swirl coaxial injector with an inner post recess of 5 mm. A back-lighting photography technique was employed to capture the instantaneous flow patterns in recess chamber with a high speed camera. Pressure oscillations in recess chamber were also measured by the miniature pressure transducer. 2-D unsteady numerical simulations basing on swirl axi-symmetric model were performed. Good agreements were generally achieved between numerical simulation and experiment in aspect for the mechanism and characteristic frequency of self-pulsation. It was found that the blocking actions of the conical liquid sheet play a crucial role in self-pulsation for the coaxial injector with recess. Self-pulsation occurs coinciding with strong pressure oscillation in recess chamber. The frequencies of spray oscillation and gas pressure in recess chamber correspond well with each other. Self-pulsation frequencies are approximately linearly proportional to the liquid Reynolds number under certain conditions. In addition, the spray oscillation transforms from high frequency pulsation (at about 3000 Hz) to ultra-high frequency pulsation (ranging from 8000 Hz to 9000 Hz) with an increase in the gas Reynolds number when the mass flow rate of liquid is large enough.

Experimental investigations on aerodynamic response of panel structures at high subsonic and low supersonic mach numbers

Panel flutter is an aeroelastic phenomenon known since the mid 1940’s. Extensive experimental and theoretical studies followed in the 1960’s and 70’s. The theoretical models applied at that time yield satisfactory results for subsonic and high supersonic Mach numbers but are inaccurate in terms of predicting the aerodynamic loads at transonic flows. In the recent years new Fluid-Structure-Interaction (FSI) methods by means of coupled CFD and FE computations have shown an increased accuracy in that Mach number domain. Within a common research project of the Airbus Company and the German Aerospace Center (DLR) such a computational approach is used for theoretical panel flutter analysis. Experiments were performed in 2015 and 2017 to validate the numerical results and to study the flow characteristics in the Mach number range 0.7 < M∞ < 1.2. For this purpose the aerodynamic response on the first eigenmode of a clamped rectangular plate is measured by means of forced motion experiments. Hydraulic actuation is used to realize small sinusoidal deflections of the plate over a wide range of amplitudes and frequencies, which has been verified by a stereo camera marker tracking system. The flow conditions in the wind tunnel are varied by means of the Mach number and the total pressure (Reynolds number) and the flow response is measured by high sensitive miniature pressure transducers.

Investigation of submerged waterjet cavitation through surface property and flow information in ambient water

To illuminate primary factors influencing the morphology of the surface impinged by submerged waterjet, experiments were performed at high jet pressures from 200 to 320MPa. The cavitation phenomenon involved in the submerged waterjet was emphasized. Copper specimens were used as the targets enduring the impingement of high-pressure waterjets. The microhardness of the specimen was measured. Surface morphology was observed using an optical profiling microscope. Pressure fluctuations near the jet stream were acquired with miniature pressure transducers. The results show that microhardness increases with jet pressure and impingement time, and the hardening effect is restricted within a thin layer underneath the target surface. A synthetic effect is testified with the plastic deformation and cavities on the specimen surfaces. Characteristics of different cavitation erosion stages are illustrated by surface morphology. At the same jet pressure, the smallest standoff distance is not corresponding to the highest mass removal rate. Instead, there is an optimal standoff distance. With the increase of jet pressure, overall mass removal rate rises as well. Low-frequency components are predominant in the pressure spectra and the dual-peak pattern is typical. As the streamwise distance from the nozzle is enlarged, pressure amplitudes associated with cavitation bubble collapse are improved.

Flow structures and cavitation in submerged waterjet at high jet pressure

Complexity of the submerged waterjet driven by high pressure resides in the jet itself and ambient water as well. To explore the traits of the high-pressure submerged waterjet, an experimental study is carried out at jet pressures of 13, 16 and 18MPa. The submerged waterjet flow is measured using particle image velocimetry in conjunction with seeded Rhodamine 6B fluorescence particles. Vorticity is calculated from velocity distribution. High-speed photography is utilized to capture the evolution of cavitation phenomenon near the nozzle. Pressure fluctuations excited in the water tank are acquired with miniature pressure transducers. At the three high jet pressures, submerged waterjet velocity attenuates remarkably along the streamwise direction, demonstrating substantial difference in comparison with low-pressure submerged waterjet. The semi-width of the waterjet stream increases downstream in a nearly linear manner. Pressure fluctuations in the water tank are featured by a wide frequency band within which low frequencies are most predominant. Meanwhile, relatively high frequencies are associated with cavitation evolution. Cavitation cloud development encompasses three distinct stages, namely cavitation cloud extending, cavitation cloud preserving and cavitation cloud shrinking. Of significance is the cavitation cloud profile, it is represented by disperse cavity elements at 13MPa. And the coherence of the cavitation cloud, as well as cavitation area fraction, is enhanced as jet pressure increases.

An Investigation of Coolant Within Serpentine Passages of a High-Pressure Axial Gas Turbine Blade

Cooling flow behavior is investigated within the multiple serpentine passages with turbulators on the leading and trailing walls of an axial gas turbine blade operating at design-corrected conditions with accurate external flow conditions. Pressure and temperature measurements at midspan within the passages are obtained using miniature butt-welded thermocouples and miniature Kulite pressure transducers. These measurements, as well as airfoil surface pressure field data from a full computational fluid dynamics (CFD) simulation, are used as boundary conditions for a model that provides quantitative values of film-cooling blowing ratio for each film-cooling hole on the blade. The model accounts for the continuously changing cross-sectional area and shape of the channels, frictional pressure loss, convective heat transfer from the solid portion of the blade, massflow reduction as coolant bleeds out through film-cooling or impingement holes, compressibility effects, and the effects of blade rotation. The results of the model provide detailed coolant ejection information for a film-cooled rotating turbine airfoil operating at design-corrected conditions and also account for the highly variable freestream conditions on the airfoil. While these values are commonly known for simpler experimental geometries, they have previously either been unknown or estimated crudely for full-stage experiments of this nature. The better-quantified cooling parameters provide a bridge for better comparison with the wealth of film-cooling work already reported for simplified geometries. The calculation also shows the significant range in blowing ratio that can arise even among a single row of cooling holes associated with one of the turbulated passages, due to significant changes in both coolant and local freestream massfluxes.

Pressure and shear stress in trabecular bone marrow during whole bone loading

Skeletal adaptation to mechanical loading is controlled by mechanobiological signaling. Osteocytes are highly responsive to applied strains, and are the key mechanosensory cells in bone. However, many cells residing in the marrow also respond to mechanical cues such as hydrostatic pressure and shear stress, and hence could play a role in skeletal adaptation. Trabecular bone encapsulates marrow, forming a poroelastic solid. According to the mechanical theory, deformation of the pores induces motion in the fluid-like marrow, resulting in pressure and velocity gradients. The latter results in shear stress acting between the components of the marrow. To characterize the mechanical environment of trabecular bone marrow in situ, pore pressure within the trabecular compartment of whole porcine femurs was measured with miniature pressure transducers during stress-relaxation and cyclic loading. Pressure gradients ranging from 0.013 to 0.46kPa/mm were measured during loading. This range was consistent with calculated pressure gradients from continuum scale poroelastic models with the same permeability. Micro-scale computational fluid dynamics models created from computed tomography images were used to calculate the micromechanical stress in the marrow using the measured pressure differentials as boundary conditions. The volume averaged shear stress in the marrow ranged from 1.67 to 24.55Pa during cyclic loading, which exceeds the mechanostimulatory threshold for mesenchymal lineage cells. Thus, the loading of bone through activities of daily living may be an essential component of bone marrow health and mechanobiology. Additional studies of cell-level interactions during loading in healthy and disease conditions will provide further incite into marrow mechanobiology.

A Physical Head and Neck Surrogate Model to Investigate Blast-Induced Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) resulting from the exposure to a blast shock wave is a challenging problem due to the broad long-term neurological deficits on the victims. The blast-related injury is not only due to the prevalence of military conflicts, but also due to increase terrorist attacks and domestic/industrial accidents. Mechanisms of blast-induced mild traumatic brain injury (BImTBI) have been controversial for a long time and nowadays are one of the most attentive topics among the neurotrauma researches. A physical head and neck model (PHNM) equipped with a surrogate gel brain was developed, and its dynamic responses to a blast wave were evaluated using a predesigned compressed air-driven shock tube. The neck model was constructed and tuned to simulate the actual human neck stiffness. The history of intracranial pressure (ICP) at different locations within the brain was monitored with four miniature pressure transducers. The acceleration of the head as well as the brain model was recorded using two accelerometers mounted internally and outside the PHNM. The shockwave effects on the PHNM were examined at different distance orientations from shock tube exit. The PHNM was exposed to free-field blast tests with controlled reliable positive peak pressure (PPP). The ICP amplitudes/profiles and the acceleration results vary according to the PHNM locations and orientations with respect to shock tube exit. The most vital parameters of ICP wave profiles including PPP, positive phase duration, and positive impulse values were greatly affected by the PHNM locations/orientations from the shock tube exit.

Experimental Investigations on DI Diesel Engine with Different Combustion Chambers Insulation

Aim: The four-stroke single cylinder diesel engine’s performance with various low heat rejection (LHR) combustion chambers was determined Critical comparison was made for various configurations of the combustion chambers with neat diesel operation. Design Parameters: Direct injection diesel engine with various configurations of the combustion chambers–Combustion chamber with air gap insulation and ceramic coating (LHR–3); air gap insulation (LHR–2); and ceramic coated combustion chamber (LHR–1) Injection pressure and timing. Original Research Article Krishna et al.; BJAST, 6(3): 239-260, 2015; Article no.BJAST.2015.084 240 Materials and Methods: Exhaust emissions and performance parameters and were evaluated at different values of brake mean effective pressure (BMEP) of the engine. Combustion parameters were evaluated at its peak load operation. Particulate emissions were determined by smoke opacity meter (AVL 437), while nitrogen oxide levels were noted by NOx Analyzer (Netel Chromatograph NOx Analyzer (VM 4000). Combustion characteristics of the engine were determined at peak load operation of the engine using TDC (top dead centre) encoder, miniature Piezo electric pressure transducer, and special p (pressure)– (crank angle) software package. Brief Results: Deteriorated performance was shown by the engine with air gap insulated and ceramic coated (LHR–3) combustion chamber, when compared with engine with other configurations of the combustion chamber at recommended injection timing of 27° bTDC.(before top dead centre) Conclusions: Engine with LHR–1, LHR–2 and LHR–3 combustion chambers with mineral diesel operation showed deteriorated performance at 27° bTDC and improved at optimum injection timings and with increased injection pressure.

Total pressure fluctuations and two-phase flow turbulence in hydraulic jumps

The large-scale turbulence and high air content in a hydraulic jump restrict the application of many traditional flow measurement techniques. This paper presents a physical modelling of hydraulic jump, where the total pressure and air–water flow properties were measured simultaneously with intrusive probes, namely a miniature pressure transducer and a dual-tip phase-detection probe, in the jump roller. The total pressure data were compared to theoretical values calculated based upon void fraction, water depth and flow velocity measured by the phase-detection probe. The successful comparison showed valid pressure measurement results in the turbulent shear region with constant flow direction. The roller region was characterised by hydrostatic pressure distributions, taking into account the void fraction distributions. The total pressure fluctuations were related to both velocity fluctuations in the air–water flow and free-surface dynamics above the roller, though the time scales of these motions differed substantially.

Comparative studies on performance evaluation of DI diesel engine with high grade low heat rejection combustion chamber with carbureted alcohols and crude jatropha oil

Abstract Search for renewable fuels such as vegetable oils and alcohols (ethanol and methanol) has become pertinent in the context of fossil fuel crisis and vehicle population explosion. The drawbacks associated with vegetable oils (high viscosity and low volatility) and alcohols (low cetane number) for use in diesel engines call for a hot combustion chamber, with its significant characteristics of higher operating temperature, maximum heat release, higher brake thermal efficiency and ability to handle the lower calorific value fuel. Investigations were carried out to evaluate the performance of a direct injection compression ignition engine with high grade low heat rejection (LHR) combustion chamber consisting of air gap insulated piston with 3 mm air gap with superni (an alloy of nickel) crown, air gap insulated liner with superni insert and ceramic coated cylinder head fueled with crude jatropha oil and carbureted alcohol (ethanol/methanol) with varied injection timings and injector opening pressures. Carbureted alcohol was inducted into the engine through a variable jet carburetor, installed at the inlet manifold of the engine at different percentages of crude vegetable oil at full load operation on mass basis. Comparative studies were made with engine with LHR combustion chamber with data of conventional engine with test fuels of diesel, crude vegetable oil and carbureted alcohol at recommended injection timing and optimized injection timing. Comparative studies were also made with methanol operation with data of ethanol operation on both versions of the combustion chamber with different operating conditions. Performance parameters, exhaust emissions and combustion characteristics were determined at full load operation of the engine with varied injection timings and injector opening pressures. Aldehydes were measured by the dinitrophenyl hydrazine (DNPH) method. Combustion diagnosis was carried out with a miniature piezoelectric pressure transducer, top dead center (TDC) encoder and special pressure–crank angle software package. The optimum injection timing was observed to be 32° bTDC with conventional engine while it was 29° bTDC for insulated engine with vegetable oil operation. The maximum induction of alcohol (methanol/ethanol) in conventional engine was found to be 35%, while it was 60% for the engine with LHR combustion chamber at recommended injection timing (27° bTDC). However, the maximum induction of alcohol was observed to be 55% with engine with LHR combustion chamber at its optimum injection timing. With maximum induction of methanol, at an injector opening pressure of 190 bar, engine with LHR combustion chamber at its optimum injection timing increased peak brake thermal efficiency by 3%; at full load operation brake specific energy consumption comparable, decreased exhaust gas temperature by 3%, decreased coolant load by 6%, volumetric efficiency comparable, increased formaldehyde levels by 30%, decreased acetaldehyde levels by 35%, decreased particulate emissions by 20%, decreased nitrogen oxide levels by 14%, increased peak pressures by 3% and maximum rate of pressure rose by 3%, when compared with ethanol operation on engine with LHR combustion chamber at its optimum injection timing.

Experimental investigation of pressure drop in pulse tube cryocooler

Highly efficient Pulse Tube Cryocooler (PTC) is subject of recent research and development activities. High efficiency can be obtained by increasing the available refrigeration effect at desired temperature. Various geometrical and operating parameters affect the performance of PTC. Pressure drop is one of the significant parameters. A major pressure drop occurs in regenerator compared to other components of PTC. Experimental investigation is carried out on two different single stage U-type Pulse tube cryocoolers. Regenerator and pulse tube volumes are kept same in both the cases. SS meshes with mesh number400 are used. Length to Diameter (L/D) ratio of regenerator is changed from 1.93 to 9. A noticeable pressure drop of 2.07 bar is measured for higher L/D ratio as compared to 0.29 bar in the lower one. The effect of pressure drop is studied on no load temperature as well as refrigeration effect. The study is further extended to understand the effect of pressure drop using coarse meshes in the regenerator. The pressure drop for oscillating flow prevailing in the pulse tube cryocooler is measured using the high frequency miniature pressure transducers.