Nozzle Opening Research Articles

Estimation of the nozzle with the stepped divergent section in critical flow regime

A sonic nozzle with a toroidal inlet region, cylindrical throat and a stepped diffuser with cylindrical sections were considered. An analytical method was proposed for estimating the required pressure drop for the nozzle operating in a critical flow regime. The results of analytical estimation of the pressure buildup in the nozzle steps were compared with the ones of numerical simulation. It is shown that replacing the conical divergent section of ISO 9300 standard nozzle with easy-to-manufacture stepped divergent section leads to a twofold increase in the required pressure drop for the nozzle operating in the critical flow regime, which in many cases is acceptable.

Three-dimensional numerical thrust performance analysis of hydrogen fuel mixture rotating detonation engine with aerospike nozzle

The propulsive performance for an H2/O2 and H2/Air rotating detonation engine (RDE) with conic aerospike nozzle has been estimated using three-dimensional numerical simulation with detailed chemical reaction model. The present paper provides the evaluation of the specific impulse (Isp), pressure gain and the thrust coefficient for different micro-nozzle stagnation pressures and for two configurations of conic aerospike nozzle, open and choked aerospike. The simulations show that regardless of the nozzle, increase the micro-nozzles stagnation pressure increases the mass flow rate, the pre-detonation gases pressure and consequently the post-detonation pressure. This gain of pressure in the combustion chamber leads to a higher pressure thrust through the nozzle, improving the Isp. It was also found that the choked nozzle increases the chamber time-averaged static pressure by 50–60% compared with the open nozzle, inducing higher performance for the same reason explained before.

Impact of split injection strategy on combustion, performance and emissions characteristics of biodiesel fuelled common rail direct injection assisted diesel engine

In this work, the effect of single and split injection strategy on combustion, performance and emissions characteristics of biodiesel was experimentally investigated on a common rail direct injection assisted diesel engine. In single injection strategy, Nozzle opening pressure and fuel injection timing was varied from 200 to 600 bar and 19°–27° CA bTDC respectively. Experimental results revealed that B100 had the maximum brake thermal efficiency of 35.74% at 500 bar and 25° CA bTDC. Engine exhaust emissions of unburned hydrocarbon and smoke were decreased, whereas nitric oxide emission increased in B100 fuel at higher nozzle opening pressure and advanced fuel injection timing. In split injection strategy, start of main injection timing and post injection timing was varied from 19° to 25° CA bTDC and −5° CA bTDC to 5° CA aTDC respectively. The results exhibited that the B100-90%-10% has the maximum brake thermal efficiency of 34.43%. Minimum unburned hydrocarbon and smoke emissions were obtained in B100-75%-25%. Maximum nitric oxide emission was obtained in B100-90%-10%. Thus, the experimental studies clearly states that advanced injection strategy reduces the exhaust emissions and improves the engine performance.

Improvement of the smelting efficiency based on the use of composite nozzles in the oxygen lances of high-capacity converters

The nozzle designs of oxygen lances are proposed, which ensure the improvement of technical and economic parameters of converter smelting and metallurgical quality of steel. The developed solutions make it possible to ensure the operation of composite lance nozzles without possible erosion wear of the supercritical part of the nozzle with an acceptable off-design degree. The cylindrical nozzle allows the supersonic flow of oxygen to be stabilized, the length of the initial and transitional sections of the jet to be increased, which is important for organizing a “tough” blowing of the converter bath at the final stage of the operation in order to reduce the oxidation of metal and slag.

A model-scale test on noise from single-stream nozzle exhaust geometries in static conditions

A model-scale test with single-stream nozzle exhaust geometries was carried out at the anechoic chamber of Beihang University in Beijing, China. The spectral characteristics are investigated, and the effects of the following parametric variations are reported in this paper: impact of nozzle operating conditions on spectra; impact of the presence of a plug; and effectiveness of chevron configurations for noise mitigation. The measurement shows that the change of pressure values has more impact on spectra than the change of temperature values. The spectral change due to pressure is shown at all band numbers for unheated conditions whereas it is more pronounced at high-frequency ranges for heated conditions. An impact of the presence of a plug is also clearly observed. The reduction of noise is moderate up to band number of 35, and becomes more significant at higher band numbers. It is observed that chevron nozzles are more efficient at high pressure and temperature values. It is expected that the quantified analysis will be used to develop an empirical model of single jet noise, which will be the baseline for the development of prediction of noise from turbofan engines of high bypass ratios.

Rapid sample delivery for megahertz serial crystallography at X-ray FELs.

Liquid microjets are a common means of delivering protein crystals to the focus of X-ray free-electron lasers (FELs) for serial femtosecond crystallography measurements. The high X-ray intensity in the focus initiates an explosion of the microjet and sample. With the advent of X-ray FELs with megahertz rates, the typical velocities of these jets must be increased significantly in order to replenish the damaged material in time for the subsequent measurement with the next X-ray pulse. This work reports the results of a megahertz serial diffraction experiment at the FLASH FEL facility using 4.3 nm radiation. The operation of gas-dynamic nozzles that produce liquid microjets with velocities greater than 80 m s-1 was demonstrated. Furthermore, this article provides optical images of X-ray-induced explosions together with Bragg diffraction from protein microcrystals exposed to trains of X-ray pulses repeating at rates of up to 4.5 MHz. The results indicate the feasibility for megahertz serial crystallography measurements with hard X-rays and give guidance for the design of such experiments.

Interaction of external flow with linear cluster plug nozzle jet

Plug nozzle flow in the presence of external flow is experimentally investigated at free-stream Mach numbers of 0.0, 0.7, 0.9, 1.1, and 1.5. The internal nozzle is operated in overexpanded and underexpanded regimes for these external flow Mach numbers. For the subsonic external flow, slight changes in the plug jet flow are observed as compared to the no-external-flow case. The supersonic external flow introduces substantial changes to plug flow jet structure as well as the wave interactions within it, as compared to the no-external-flow case. For the overexpanded internal nozzle operation, the oblique shock waves are asymmetric within the plug core jet. For underexpanded internal nozzle operation, an oblique shock formation is noticed on the plug surface which induces flow separation downstream. The RMS of the pressure fluctuations indicates a distinct peak corresponding to the foot of the overexpansion shock on the plug surface. These peaks are observed at consistent pressure ratios for all the external flow conditions considered. Regarding the cluster plug nozzle flow field, three-dimensional flow features are noticed because of the intermodule interactions. For both the overexpanded and underexpanded internal jet conditions, the interactions between the modules are predominantly compression waves in the spanwise direction. The RMS of the pressure fluctuations measured along the intermodule centreline suggests that the spanwise wave interactions have considerable influence on the flow unsteadiness.

Simulation of Air Entrainment during Mold Filling: Comparison with Water Modeling Experiments

Oxide inclusions form during pouring of metal castings as a result of air entrainment. Recently, a model was developed by the authors to predict the volumetric air entrainment during pouring. It was found that the velocity, diameter, and turbulence intensity of the liquid stream affect the air entrainment rate during pouring. In this study, the developed air entrainment model is validated with water modeling experiments. In the water modeling studies, water was poured using a bottom pour ladle. The effects of nozzle opening, head height, nozzle diameter, and nozzle extension are simulated. The predictions compare favorably with the experimental measurements. Results indicate that low head height and short pouring time have a beneficial effect on reducing the air entrainment during pouring. In addition, a fully open nozzle and the use of a nozzle extension further reduce the amount of entrained air.

Performance of multi-cylinder diesel engine fueled with mahua biodiesel using Selective Catalytic Reduction (SCR) technique

ABSTRACTIndia is mainly an agricultural country. For irrigation, the farmers are primarily dependent on diesel engines which run on immaculate diesel. In order to reduce the consumption of diesel, oxygenated fuel additives seem to be a good proposition. In this connection, biodiesel is one of the best choices and this study is an attempt in that direction. Of the various non-edible vegetable oils available for making biodiesel, Mahua oil (Madhuca Indica) is preferred since it is widely available across the country. The problem with biodiesel is the higher emission of oxides of nitrogen (NOx). NOx emissions can be controlled with Ad-Blue (Urea) solution. Fortunately, for the irrigation sector, it may be considered as a blessing in disguise since, Urea which is used to control the NOx emissions is used as a fertilizer. In this work an experimental study has been carried out to assess the suitability of selective catalytic reduction (SCR) technique in reducing NOx. To arrive at accurate results, property characterization has been carried out for various blends. Tests were conducted on a multi-cylinder water cooled diesel engine at 2400 rpm. For loading an eddy current dynamometer was used. The injection nozzle opening pressure (NOP) was set to 220 bar with constant static injection timing (SIT) of 18° before top dead center (bTDC). This study presents the results at full load, employing SCR technique. The results were compared with conventional engine results under same operating condition where no reduction technique was employed. It was found that there was a significant reduction in NOx (around 3.91%) when the engine was operated with 25% biodiesel, thereby saving 25% diesel. This study establishes that SCR technique with 25% biodiesel addition as a viable option without any modification in the engine and without any compromise on the engine performance. Therefore, this option can be considered as sustainable one in agricultural operation.

Parametric study of interaction effect between closely-spaced nozzles in a thin cylindrical pressure vessel

The presence of nozzle openings in process vessels gives rise to stress concentration due to localization of stresses around openings. Introduction of second nozzle in vicinity of first nozzle will generate its own stress contours and will interact with stress contours of primary nozzle. To investigate the effect of a secondary nozzle, computational simulation has been carried out. The simulation is validated with established benchmarks. Geometry of vessel and nozzle openings, size of reinforcement and other geometric parameters like centre to centre distance, axial distance, etc. affecting maximum stress have been studied. Result for each case is plotted and discussed in detail.

Impact of nozzle operation on mass transfer in jet aerated loop reactors. Characterization and comparison to an aerated stirred tank reactor.

The impact of mass transfer on productivity can become a crucial aspect in the fermentative production of bulk chemicals. For highly aerobic bioprocesses the oxygen transfer rate (OTR) and productivity are coupled. The achievable space time yields can often be correlated to the mass transfer performance of the respective bioreactor. The oxygen mass transfer capability of a jet aerated loop reactor is discussed in terms of the volumetric oxygen mass transfer coefficient kLa [h-1] and the energetic oxygen transfer efficiency E [kgO2kW-1h-1]. The jet aerated loop reactor (JLR) is compared to the frequently deployed aerated stirred tank reactor. In jet aerated reactors high local power densities in the mixing zone allow higher mass transfer rates, compared to aerated stirred tank reactors. When both reactors are operated at identical volumetric power input and aeration rates, local kLa values up to 1.5 times higher are possible with the JLR. High dispersion efficiencies in the JLR can be maintained even if the nozzle is supplied with pressurized gas. For increased oxygen demands (above 120 mmolL-1h-1) improved energetic oxygen transfer efficiencies of up to 100 % were found for a JLR compared to an aerated stirred tank reactor operating with Rushton turbines.

Nozzle effects on the injection characteristics of diesel and gasoline blends on a common rail system

In this study, the injection characteristics of diesel and blends of diesel and gasoline were investigated on a common rail injection system, using two nozzles with different orifice diameter and opening pressure. The volumetric injection rate curves, volumetric and mass cycle injection quantities and the coefficient of variances within a range of changed injection pressure and energizing time were investigated. It was found that increased gasoline proportion in fuel blends produced higher peak volumetric injection rates and volumetric cycle injection quantities than those of diesel, but comparative mass cycle injection quantities with diesel. The nozzle opening pressure and the orifice diameter also influenced the injection rate curve and cycle injection quantity, but the influential behavior depended on the energizing time and injection pressure, which might be attributed to different needle lifting motions. Higher peak injection rate and cycle injection quantity were found with increased orifice diameter, injection pressure and energizing duration. Cycle injection quantity variance was strongly related with the length of energizing time and injection pressure, but nozzle parameters and test fuels were not observed to significantly influence the injection quantity variance.

Investigation of using multi-shockwave system instead of single normal shock for improving radial inflow turbine reliability

A variable nozzle turbine (VNT) has become an important technology for diesel engine applications. During the development and design process, one of the most important tasks is to minimize the risk of high cycle fatigue (HCF) failure. When a VNT operates with high inlet pressure and small nozzle opening, a shock wave may appear near nozzle vane trailing edge. The shock wave introduces strong excitation force on the downstream turbine blades and has a potential to damage the turbine wheel. To improve turbine reliability, a method of generating multi-shockwave system by using grooved surface nozzle was investigated. It was found that, in the multi-shockwave system, the intensity of the shock wave is weakened in comparison to original single normal shock wave, and its impact on the turbine wheel is therefore lowered. However, with the use of the grooved surface, penalty on the turbine efficiency is numerically found, but very small at the research point.

Inflow-rotor interaction in Tesla disc turbines: Effects of discrete inflows, finite disc thickness, and radial clearance on the fluid dynamics and performance of the turbine

The article establishes the physics of the complex interaction of discrete multiple inflows with the stationary shroud and the rotating channel of a Tesla disc turbine. Using a large number (150) of separate, fully three-dimensional computational fluid dynamic simulations, we demonstrate the (sometimes dramatic) role of four important input parameters, namely the number of nozzles ([Formula: see text]), rotational speed of the discs (Ω), radial clearance between the rotor and the shroud ([Formula: see text]), and disc thickness ( dt), in the fluid dynamics and performance of a Tesla turbine. An increase in [Formula: see text] or [Formula: see text] assists in the attainment of axisymmetric condition at rotor inlet. Ω influences significantly the distribution of radial velocity including the fundamental shape of its z-profile (parabolic, flat or W-shaped). The paper demonstrates the existence of an optimum [Formula: see text] for which the efficiency of the rotor (η) is maximized. Present computational fluid dynamics simulations for many combinations of [Formula: see text] and Ω establish that the η versus Ω curves, for each fixed value of [Formula: see text], are of the shape of an inverted bucket. With increasing [Formula: see text], the operable range of Ω decreases, the buckets become more peaky and the maximum possible η increases substantially (by a factor of 2 in the example calculation shown). The present systematic work thus demonstrates quantitatively, for the first time, that an axisymmetric rotor inflow condition represents the best possible design for the rotor. It is further shown that, as the disc thickness is increased, the efficiency may decrease substantially (even dramatically) and its maxima occur at lower rotational speeds. Chamfering of the disc edge or partial admission decreases the turbine efficiency. Thus, small disc thickness, flat disc edge, full nozzle opening, optimum radial clearance, and inlet condition as close to axisymmetry as is possible are recommended for the design of an efficient Tesla disc turbine.

Studies on Improvement of Performance of Compression Ignition Engine Fuelled with Mixture of Honge Biodiesel and Tire Pyrolysis Oil

Abstract The biodiesel has lower volatility and is costlier than the fossil diesel. Hence it is necessary to add a low cost fuel which has higher volatility, with the diesel. The tire pyrolysis oil (TPO) produced from waste tire and tubes have these desirable properties and hence in this work, we have mixed TPO with biodiesel to enhance the properties of the biodiesel. The engine tests were carried out on a single cylinder compression ignition engine with the mixture of biodiesel and TPO as fuel. From the engine tests, it is observed that the fuel mixture results in engine performance close to diesel operation at the higher injector nozzle opening pressure.

Comparison of Near-Nozzle Spray Performance of Gas-to-Liquid and Jet A-1 Fuels Using Shadowgraph and Phase Doppler Anemometry

The gas-to-liquid (GTL) fuel, a liquid fuel synthesized from natural gas through Fischer–Tropsch process, exhibits better combustion and, in turn, lower emission characteristics than the conventional jet fuels. However, the GTL fuel has different fuel properties than those of regular jet fuels, which could potentially affect its atomization and combustion aspects. The objective of the present work is to investigate the near-nozzle atomization characteristics of GTL fuel and compare them with those of the conventional Jet A-1 fuel. The spray experiments are conducted at different nozzle operating conditions under standard ambient conditions. The near-nozzle macroscopic spray characteristics are determined from the shadowgraph images. Near the nozzle exit, a thorough statistical analysis shows that the liquid sheet dynamics of GTL fuel is different from that of Jet A-1 fuel. However, further downstream, the microscopic spray characteristics of GTL fuel are comparable to those of the Jet A-1 fuel.

Direct Molecular Dynamics Simulation of Nucleation during Supersonic Expansion of Gas to a Vacuum.

We develop a methodology for direct molecular-level simulation of adiabatic expansion of gas through a small orifice to a vacuum. The gas attains supersonic speeds, cools, and nucleates. The proposed approach combines equations of frictionless fluid dynamics with molecular dynamics simulation in an expanding periodic box. There are two key components of the proposed algorithm: (i) a time-reversible integrator tailored to an expanding system, and (ii) an iterative procedure employed to satisfy the condition of steady flow. For a conical nozzle (opening angle of 60°), the simulations with argon and water vapor predict cluster sizes in agreement with the experiment. Clusters of irregular shapes observed in the experiment [J. Lengyel et al. Phys. Rev. Lett. 2014, 112, 113401] are not reproduced. The role of friction, turbulence, and sonic boom originating at the sharp nozzle edge is discussed.

Effect of compression ratio, nozzle opening pressure, engine load, and butanol addition on nanoparticle emissions from a non-road diesel engine.

Currently, diesel engines are more preferred over gasoline engines due to their higher torque output and fuel economy. However, diesel engines confront major challenge of meeting the future stringent emission norms (especially soot particle emissions) while maintaining the same fuel economy. In this study, nanosize range soot particle emission characteristics of a stationary (non-road) diesel engine have been experimentally investigated. Experiments are conducted at a constant speed of 1500rpm for three compression ratios and nozzle opening pressures at different engine loads. In-cylinder pressure history for 2000 consecutive engine cycles is recorded and averaged data is used for analysis of combustion characteristics. An electrical mobility-based fast particle sizer is used for analyzing particle size and mass distributions of engine exhaust particles at different test conditions. Soot particle distribution from 5 to 1000nm was recorded. Results show that total particle concentration decreases with an increase in engine operating loads. Moreover, the addition of butanol in the diesel fuel leads to the reduction in soot particle concentration. Regression analysis was also conducted to derive a correlation between combustion parameters and particle number emissions for different compression ratios. Regression analysis shows a strong correlation between cylinder pressure-based combustion parameters and particle number emission.

A detailed investigation of a variable nozzle turbine with novel forepart rotation guide vane

One of the disadvantages of a variable nozzle turbine in practical application is the stage performance degradation due to nozzle endwall leakage flow at small nozzle openings. Aiming at restricting the nozzle leakage flow rate to improve turbine stage performance, a novel forepart rotation guide vane has been proposed and numerically studied in present work. First, the numerical results of baseline turbine were validated by experimental data to ensure the accuracy of numerical methods. Then steady and unsteady simulations were performed on both baseline and forepart rotation guide vane turbines to demonstrate the effectiveness of the novel vane and to study the characteristics of nozzle leakage flow, respectively. Results indicate that there is up to 13.5% peak efficiency improvement that has been achieved at 10% nozzle opening with the forepart rotation guide vane design; besides, rotor–stator interaction for forepart rotation guide vane is also mitigated due to the reduced nozzle leakage flow rate, thus the intensity of loading fluctuation on rotor blades is weakened significantly, which is beneficial to improve rotor blade forced response.

Unsteady velocity measurements of model-scale supersonic exhaust jets in military-relevant configurations

Of the utmost importance is the need to better understand the high temperature, high velocity flow fields generated by military tactical aircraft during “run up” and take-off that gives rise to extremely hazardous conditions for personnel and equipment within the vicinity of the aircraft. The present study aims to fill the need for high frequency, two velocity component measurements throughout the flow fields produced by university-scale supersonic jets exhausting from nozzles in configurations relevant to practical, full-scale application. Specifically, this work focuses on studying the supersonic jets operating in two basic configurations: horizontal, free jets and jets impinging normal to a ground plane reminiscent of current short-takeoff and vertical landing aircraft. Experiments are conducted at nozzle operating conditions similar to those of full-scale aircraft. Both mean velocities and turbulence components are measured in both flow fields using a laser Doppler velocimeter. Axial components of the mean flow and turbulence are measured in the free jet. In the single impinging jet flow field two-component mean velocity and turbulence components are measured in the jet plume, impingement region, and outwash flow. Free jet velocity measurements show good consistency with 50% increase in jet Reynolds number. Turbulence intensities up to 15% of the mean jet exit velocity are observed at the nozzle exit plane. Laser Doppler measurements in the outwash of an impinging jet show turbulent fluctuations produce unsteady velocities well above the mean value. Two-component impinging jet unsteady velocity spectra show a distinct peak at the same frequency as the impingement tone observed in prior impinging jet acoustic field measurements.