Optimization Of Nozzle Geometry Research Articles

Designing a new bell-type primary air nozzle for large-scale circulating fluidized bed boilers

The design of energy efficient engineering systems is crucial for sustainable operation when economic and environmental consequences are considered. Circulating Fluidized Bed (CFB) boilers, which are among the major contributors to world electricity production, are still increasing in numbers and unit sizes. Primary air nozzles are key components of CFB boilers that may decrease energy consumption and increase energy efficiency, and they need to be carefully designed. There are certain types of nozzles commonly used in the air distribution grate, but even minor design improvements on the nozzle can significantly decrease the pressure loss. This work is about optimizing the bell-type primary air nozzle used in the Turkish lignite-fired ÇAN Thermal Power Plant (CTPP), which has two 160 MWe CFB boilers, through computational fluid dynamics (CFD). Initially, the bell-type nozzle was designed newly by changing the inner head holes geometry. After that, the nozzle geometry was optimized by changing the orifice size and angle to decrease the pressure drop, increase the orifice velocity outlet, and flow uniformity through CFD simulations. With the optimum nozzle geometry, the velocity at the outlet orifices was increased, and a decrease of 2.86 kPa was achieved in the total pressure loss. Furthermore, when the nozzle orifices were designed downwardly with an angle of 105°, pressure drop across the nozzle decreased by 7.6 %, and the uniformity index increased by 2 % at the outlet orifices. Using the bell-type primary air nozzle, which is newly designed, in the CTPP boiler not only will save 2.26 GWh/year of energy consumption but also minimize the backflow risk in the boiler operation.

Insights into ZrO2- and Al2O3-based submerged entry nozzle clogging for the continuous casting of RE-treating sulfur resistant casing steel

The ZrO2- and Al2O3-based submerged entry nozzle (SEN) clogging during continuous casting of a RE-treating sulfur resistant casing steel is studied experimentally based on morphological analysis and the related thermodynamic calculations. The results show that the ceramic cloggings exists both in the inner-wall and outlet regions of SEN, while the latter is the main reason for terminating the casting with its clogging reaching 77% in the nozzle cross section area. The clogging is caused by RE-containing inclusions from molten steel and reoxidation products by the reaction between RE in molten steel and the initial formed cloggings on nozzle refractory. The possible existence state of RE in molten steel with its content has been discussed, and the clogging mechanism studied in detail. To prevent nozzle clogging, suggestions are given for continuous casting of the RE-treating steel with a modified RE treatment strategy for less solid inclusions and solute [RE] presented in liquid steel during refining process. Additionally, the optimization of nozzle geometry and its refractory materials may help as well.

Experimental evaluation of nozzles to mitigate liquid loading in gas wells

An optimally designed nozzle can be used as an efficient artificial lift system to deliquify gas wells. The objective of this work is to determine the most optimum nozzle parameters and geometry that would maximize critical pressure ratio while minimizing pressure drop across the nozzle under two-phase flow conditions. Six optimum nozzle geometries, evaluated under single-phase flow conditions in a previous study, are evaluated in this work. Two separate facilities were used to conduct the two-phase (air and water) experiments: a horizontal facility with 1.5 in. inner diameter (ID) PVC pipelines and a 30 ft long lateral pipeline section, and a vertical facility with 1.5 in. ID PVC pipelines and a 30 ft long vertical pipeline section. The horizontal facility was used to study the effect of introducing water into the system as a second phase, and the vertical facility was used to simulate conditions of a gas well with a nozzle installed as an artificial lift system. Horizontal flow experimental results showed that critical pressure ratio decreases for two-phase flow relative to single-phase flow. The distance of the annular churn flow pattern observed downstream the nozzle may be related to the nozzle performance; significantly lower performance was observed for the LJ nozzle in two phase horizontal testing relative to other nozzles – one characteristic this might be attributed to is the peculiarly longer distance of downstream annular churn flow pattern observed for this particular nozzle compared to other nozzles. Based on data analysis, the ASTAR nozzle group showed the most improved performance, similar to results obtained in single-phase horizontal testing. Based on vertical experimental results, the most optimum nozzle geometry to deliquify a loaded gas well was identified as the ASTAR nozzle 2, a parabolic nozzle geometry. A significant temperature drop downstream the nozzle was observed during these experiments. It is important to account for temperature change while designing a nozzle in order to avoid flow assurance problems, such as gas hydrate formation. The trends observed in relative performance between different nozzle geometries (rankings based on critical pressure ratio and pressure drop) for two-phase vertical experiments were similar to those observed for single-phase horizontal experiments. Therefore, single-phase experiments could be sufficient to evaluate relative nozzle geometry performance based on critical pressure ratio, for the conditions used in this study.

Effect of nozzle geometry on critical-subcritical flow transitions

The geometry of converging-diverging nozzles affects the conditions at which critical-subcritical flow transition occurs. The objective of this work is to develop guidelines to identify the optimum nozzle geometry that maximizes critical pressure ratio while minimizing pressure drop across the nozzle. Experiments were conducted in a facility with 1.5 in. ID PVC pipelines and a 30 ft. long lateral pipeline section. In total, 27 different nozzle geometries were tested, divided into two groups – conical and parabolic nozzles. Nozzles from the ASTAR, Deich, LJ and Moby Dick nozzle groups showed improved performance compared to other nozzle groups. It was determined that a smaller diverging angle and absence of an elongated throat resulted in a higher critical pressure ratio. Length of converging and diverging sections of nozzles did not have as much of an impact on nozzle performance as the throat diameter and shape of converging and diverging sections.

Effect of nozzle and combustion chamber geometry on the performance of a diesel engine operated on dual fuel mode using renewable fuels

Renewable and alternative fuels have numerous advantages compared to fossil fuels as they are biodegradable, providing energy security and foreign exchange saving and addressing environmental concerns, and socio-economic issues as well. Therefore renewable fuels can be predominantly used as fuel for transportation and power generation applications. In view of this background, effect of nozzle and combustion chamber geometry on the performance, combustion and emission characteristics have been investigated in a single cylinder, four stroke water cooled direct injection (DI) compression ignition (CI) engine operated on dual fuel mode using Honge methyl ester (HOME) and producer gas induction. In the present experimental investigation, an effort has been made to enhance the performance of a dual fuel engine utilizing different nozzle orifice and combustion chamber configurations. In the first phase of the work, injector nozzle (3, 4 and 5 hole injector nozzle, each having 0.2, 0.25 and 0.3 mm hole diameter and injection pressure (varied from 210 to 240 bar in steps of 10 bar) was optimized. Subsequently in the next phase of the work, combustion chamber for optimum performance was investigated. In order to match proper combustion chamber for optimum nozzle geometry, two types of combustion chambers such as hemispherical and re-entrant configurations were used. Re-entrant type combustion chamber and 230 bar injection pressure, 4 hole and 0.25 mm nozzle orifice have shown maximum performance. Results of investigation on HOME-producer gas operation showed 4–5% increased brake thermal efficiency with reduced emission levels. However, more research and development of technology should be devoted to this field to further enhance the performance and feasibility of these fuels for dual fuel operation and future exploitations.

Numerical study of impinging jets heat transfer with different nozzle geometries and arrangements for a ground fast cooling simulation device

In this paper, a comparative study is performed to check the nozzle geometry and arrangement effects on impinging jets heat transfer performance to help the design of a ground fast cooling simulation device which is used for the thermal tests of high speed flight vehicles. Based on the simplified physical model, the impinging jets heat transfer is modeled using the shear-stress transport (SST) k-ω turbulence model. A total of 21 different nozzle configurations including 7 geometries are considered in the numerical simulation. Heat transfer performances concerning heat transfer intensity and heat flux uniformity in different cases are compared with each other. Analysis is given on the corresponding flow fields and surface heat flux distributions. To help the optimization of nozzle geometry and arrangement in designing the device, an indicator named QU ratio is proposed for the overall performance evaluation of the nozzle configurations. The effectiveness of the QU ratio is validated based on the numerical results and it can be used to help determine the best design for certain given conditions of the ground fast cooling device.

3D-printed slit nozzles for Fourier transform microwave spectroscopy

3D printing is a new technology whose applications are only beginning to be explored. In this report, we describe the application of 3D printing to the design and construction of supersonic nozzles. Nozzles can be created for $0.50 or less, and the ease and low cost can facilitate the optimization of nozzle performance for the needs of any particular experiment. The efficacy of a variety of designs is assessed by examining rotational spectra of OCS (carbonyl sulfide) and Ar-OCS using a Fourier transform microwave spectrometer with tandem cavity and chirped-pulse capabilities. A slit geometry which, to the best of our knowledge has not been used in conjunction with Fourier transform microwave spectrometers, was found to increase the signal-to-noise ratio for the J = 1←0 transition of OCS, by a factor of three to four compared with that obtained using our standard circular nozzle. Corresponding gains for the Ar-OCS complex were marginal, at best, but further optimization of nozzle geometry should be possible. The spectrometer itself is designed to allow rapid switching between cavity and chirped-pulse modes of operation without the need to break vacuum. This feature, as well as the newly incorporated chirped-pulse capability, is described in detail.

Tentative Study on Performance of Darriues-Type Hydroturbine Operated in Small Open Water Channel

The development of small hydropower is one of the realistic and preferable utilizations of renewable energy, but the extra-low head hydropower less than 2 m is almost undeveloped yet for some reasons. The authors have developed several types of Darrieus-type hydro-turbine system, and among them, the Darrieus-turbine with a wear and a nozzle installed upstream of turbine is so far in success to obtain more output power, i.e. more shaft torque, by gathering all water into the turbine. However, there can several cases exist, in which installing the wear covering all the flow channel width is unrealistic. Then, in the present study, the hydraulic performances of Darrieus-type hydro-turbine with the inlet nozzle is investigated, putting alone in a small open channel without upstream wear. In the experiment, the five-bladed Darrieus-type runner with the pitch-circle diameter of 300 mm and the blade span of 300 mm is vertically installed in the open channel with the width of 1,200 mm. The effectiveness of the shape of the inlet nozzle is also examined using two types of two-dimensional symmetric nozzle, the straight line nozzle (SL nozzle) with the converging angle of 45 degrees and the half diameter curved nozzle (HD nozzle) whose radius is a half diameter of runner pitch circle. Inlet and outlet nozzle widths are in common for the both nozzles, which are 540 mm and 240 mm respectively. All the experiments are carried out under the conditions with constant flow rate and downstream water level, and performances are evaluated by measured output torque and the measured head difference between the water levels upstream and downstream of the turbine. As a result, it is found that the output power is remarkably increased by installing the inlet nozzle, and the turbine with SL nozzle produces larger power than that with HD nozzle. However, the peak efficiency is deteriorated in both cases. The speed ratio defined by the rotor speed divided by the downstream water velocity at the peak efficiency is larger in both cases with the inlet nozzle, partly due to the increase of inflow velocity into the turbine. In order to understand the cause of the differences of power, i.e. torque characteristics of the turbine with SL and HD nozzles, twodimensional CFD simulation is carried out. It is found that the instantaneous torque variation is important for the overall turbine performances, indicating the possibility of further performance improvement through the optimization of nozzle geometry.

Optimum Nozzle Angle of a Micro Solid-Propellant Thruster

The characteristics of supersonic flow field and thrust for a micronozzle used in a microthruster were analyzed numerically to determine the optimum nozzle geometry. Typical parameter values are 300 μm throat diameter, 10 bar and 1000 K for stagnation conditions, and 1–100 ms for combustion completion. The effects of the boundary layer, heat loss, and unsteady stagnation conditions were considered. Thrust was much more dependent on the nozzle expansion angle than the area ratio or length. Optimum nozzle expansion angle for maximum thrust was close to 30° for a planar 2D nozzle and 25° for a 2D axisymmetric nozzle.

Studies on ejector-venturi fume scrubber

Experimental studies on diesel fume scrubbing have been conducted in a down-flow type liquid-jet ejector-venturi scrubber. The fume particulates have been captured in the throat of the ejector-venturi by a mechanism involving inertial impaction and impingement. The effect of nozzle geometry and the motive fluid flow rates on the suction created and the volumetric fume aspiration rates have been analyzed, in order to select the optimum nozzle geometry. Using the optimum nozzle geometry the efficiency of fume collection has been experimentally investigated as function of various hydrodynamic parameters. A theoretical analysis has been performed to interpret the experimental findings and determination of nozzle loss coefficients.

Optimum geometries for scarfed perfect nozzles

The results of an investigation to determine the optimum geometry for length constrained scarfed nozzles employing perfect expansion contours is presented. A scarfed perfect nozzle performance analysis, based on an axisymmetric flowfield model and utilizing the method of characteristics solution technique, was developed. The performance model was utilized hi an optimization procedure to determine, for a range of nozzle projected lengths, the optimum set of scarfed perfect nozzle geometries. For each projected length, the respective optimum nozzle geometry was selected to maximize motor axial thrust coefficient. The set of optimum scarfed nozzle geometries was compared against optimum length constrained scarfed nozzles employing conical expansion contours. The optimum scarfed perfect nozzle geometries generated by this investigation were specifically produced for utilization hi a design methodology developed to minimize the length of tactical solid propellant propulsion systems. Used in conjunction with the design methodology, the results of the present investigation provide the designer with a means of further reducing propulsion system length.

Amputation

In this paper, a comparative study is performed to check the nozzle geometry and arrangement effects on impinging jets heat transfer performance to help the design of a ground fast cooling simulation device which is used for the thermal tests of high speed flight vehicles. Based on the simplified physical model, the impinging jets heat transfer is modeled using the shear-stress transport (SST) k-ω turbulence model. A total of 21 different nozzle configurations including 7 geometries are considered in the numerical simulation. Heat transfer performances concerning heat transfer intensity and heat flux uniformity in different cases are compared with each other. Analysis is given on the corresponding flow fields and surface heat flux distributions. To help the optimization of nozzle geometry and arrangement in designing the device, an indicator named QU ratio is proposed for the overall performance evaluation of the nozzle configurations. The effectiveness of the QU ratio is validated based on the numerical results and it can be used to help determine the best design for certain given conditions of the ground fast cooling device.

Sheath Flow Focusing in Supersonic Jet Spectroscopy

The mechanism of cooling in sheath-flow-focused supersonic jet expansions is examined. Cooling is found to be strongly influenced by the sheath gas flow properties but independent of the carrier gas in the sample stream. These results indicate that considerable turbulence and mixing between the sheath and sample gases occur downstream from the orifice. However, mixing cannot be complete, since, relative to results with a conventional jet expansion, a substantial enhancement of analyte is obtained along the centerline of a sheath-flow-focused jet expansion. Spectral broadening at “high” analyte mass flow rates within the sample stream is found to arise from inefficient cooling. There are limits to both how large and how small the nozzle orifice can be. Small orifices result in spectral broadening, even at very low analyte mass flow rates. Large orifices may have Reynolds numbers sufficient to cause turbulent flow, which degrades the focusing effect. The optimum nozzle geometry and gas flow conditions for sheath-flow-focused jet expansions are discussed.