Swirl Chamber Research Articles

The Performance of an Air-Cooled Diesel Engine with a Variable Cross-Section Dual-Channel Swirl Chamber

In order to improve the performance of a mini-type air-cooled diesel engine in terms of the overall efficiency and engine emissions, a swirl chamber of a variable cross-section dual-channel model was developed. This study proposed nine turbulent swirl chambers with a variable cross-section for a dual-channel combustion solution, which applied a dual-channel cross-section to the insert between the original swirl chamber and the main chamber. Model-based design, simulation and experiments were applied as a feasible approach to address this issue to find out the influence of the dual-channel inclination angle and divergence angle on the swirl rate in the swirl chamber, the power and the emissions performance, including the fuel efficiency. By comparing the tests, the performance of the diesel engine with a variable cross-section dual-channel swirl chamber was superior to the original one with a single channel in terms of the swirl rate, fuel consumption rate and emissions.

Numerical investigation on multi-stage swirl cooling at mid-chord region of gas turbine blades

Compared with the single-stage one, the multi-stage swirl cooling technique has great potential at the mid-chord region of gas turbine blades. Currently, the effect of the chamber structure at the mid-chord region of the blades on the multi-stage swirl cooling is still unknown. In this study, four kinds of the multi-stage swirl chamber models are built: Case 1 has two swirl nozzles and three chambers, and cases 2–4 have six swirl nozzles and seven chambers. Fluid flow and heat transfer characteristics of the coolant in the swirl cooling configurations are numerically investigated. The standard k-ε turbulent model is adopted in current study and the Reynolds number of the coolant varies from 12,000 to 52000. The results show that the long swirl chamber in case 1 has negative effect on the performance of the swirl cooling this is because the swirl velocity along the axial direction is gradually reduced and the Nusselt number is decreased remarkably. For cases 2–4, the chambers are separated into several short ones. Therefore, the swirl velocity could keep high value and so is the Nusselt number. Although more swirl chambers could lead to higher pressure loss coefficient, cases 2–4 show better comprehensive thermal performance as compared to case 1. Among the current cases, the swirl chamber structure in case 4 shows the highest cooling effectiveness and obtains more uniform temperature distributions on the external surface of the blade.

Effects of circumferential ribs on suppressing cross-flow and enhancing heat transfer in swirl cooling

This paper proposed a swirl chamber with circumferential ribs to avoid the impacting of cross-flow to jets, thus enhancing the penetration ability of jet and swirl cooling heat transfer intensity. To reveal the mutual effects between jets and cross-flow, the heat transfer features and flow structures under different Reynolds numbers of smooth swirl chamber and novel rib-roughened swirl chambers were studied and compared using 3D steady numerical analysis. The influence of rib height ratio on flow and heat transfer features was investigated further. The investigation revealed that for smooth swirl chamber, the cross-flow seriously weakened the heat transfer intensity. In contrast, the novel rib-roughened swirl chamber had an excellent suppression effect on cross-flow, thus greatly enhancing the penetration ability of jet and strengthening the swirl cooling heat transfer intensity. Under the Reynolds number of 10,500, for smooth swirl chamber, the peak number of circumferentially-averaged Nusselt number decreased from 80 to 58 from the first pitch to the last pitch. While for the case that rib height ratio is equal to 0.5, it increased from 80 to 120. In addition, the suppression effects of circumferential ribs on cross-flow increased when the rib height ratio increased, likewise the heat transfer enhancement effect. When the rib height ratio is less than 0.5, the Nusselt number ratio was larger than the friction factor ratio, while when the rib height ratio is larger than 0.5, the Nusselt number ratio was less than the friction factor ratio. The best thermal performance can be achieved when the rib height ratio was 0.5. Besides, the heat transfer enhancement effect of circumferential ribs was more significant under a higher Reynolds number in the studying range.

EFFECT OF GEOMETRICAL AND OPERATIONAL PARAMETER ON OIL-WATER SEPARATION IN AXIAL INLET HYDROCYCLONE

To overcome the high water content in numerous oil fields, axial inlet hydrocyclone is considered an alternative device of oil-water separation technique that is used downfield. This type of hydrocyclone has a rare previous work compared to other vortex tube separators. Additionally, the accurate mechanism of the enhanced separation process by optimizing the separation technologies remains unclear. Therefore, an extensive study was conducted to expand the application range of the axial inlet hydrocyclone. This workpresents a literature review of the different separation technologies for the axial inlethydrocyclone. These are categorized into two groups: (i) geometrical parameters including, internal swirl element (ISE), swirl chamber, and (ii) operational parameters including, inlet flow rate, feed temperature, mixture fraction, and droplet size. The influence of these parameters on the velocity components profile and pressure drop were analyzed based on the separation performance parameters such as separation efficiency and pressure drop. This work could serve as an engineering tool that results in the enhanced economic workability of separation by hydrocyclone.

Numerical study of swirl cooling enhancement by adding mist to air: Effects of droplet diameter and mist concentration

Swirl cooling with air/mist mixture coolant is a promising heat transfer method, for which the combined influence of swirl and mist should be clearly understood. In this work, numerical simulations on the swirl cooling performance of the leading edge of a turbine vane using mist/air mixture and air are implemented for comparative study. The Eulerian-Lagrangian particle tracking method is adopted to investigate the two phase cooling. The coolant air impacts tangentially the inner surface of the circular swirl chamber through two rectangular nozzles, and the mists with different concentrations (5%, 10%, and 20%) and droplet diameters (1 μm, 2.5 μm, 5 μm, 7.5 μm, and 10 μm) are included to explore their effects on the cooling performance. The results demonstrate that the circumferentially-averaged Nusselt number, Nucir, increases with the increase of mist concentration, and this effect becomes prominent when the droplet diameter increases. For droplet diameter of 10 μm and mist concentration of 20%, Nucir can increase by 12.6% to 309.7% as compared to pure air. In addition, the empirical correlations of the global-averaged Nusselt number, and friction coefficient to the mist diameter and mist concentration are given for the first time. It is concluded that the thermal performance factor, which can be used to evaluate comprehensively the cooling characteristics, increases with the increase of mist concentration and droplet diameter. The empirical correlations and thermal performance evaluation provide the basis for further theoretical analysis of the cooling performance using air/mist mixture.

Combustion performance and energy distributions in a new multi-swirl combustion system

Previous research has demonstrated that the separated swirl combustion system (SSCS) based on double swirl and TCD combustion chamber improves direct-injection diesel engine combustion performance. A new multi-swirl combustion system based on lateral swirl and TCD combustion chamber (MSCS-LT) was proposed in this study. Experimental research was performed using single-cylinder diesel engine to study MSCS-LT and SSCS combustion performance and energy distribution characteristics. Simulation research was performed to reveal the influence mechanisms of the combustion chamber structure on in-cylinder fuel-air mixing quality and heated part surface temperatures.Experimental results show that MSCS-LT provides better combustion performance and lower energy losses under various working conditions than SSCS, especially at high loads and low excess air coefficients. Simulation results show that MSCS-LT enhances fuel diffusion in the axial and circumferential directions, producing better fuel-air mixing quality. Since most of the fuel is kept in the combustion chamber, direct contact between the high-temperature gases and heated parts is avoided. However, in SSCS, the interference of adjacent fuel sprays causes the accumulation of the rich fuel-air mixture, deteriorating the fuel-air mixing quality. Meanwhile, the excessive injection angle causes direct contact between the high-temperature gases and the cylinder head as well as the cylinder liner, resulting in higher surface temperatures.

Performance, emission, and exergy analysis of an IDI dual swirl combustor diesel engine with blended waste Chia seed oil as a biofuel

This study aims to investigate the performance characteristics of an IDI engine with a novel dual swirl chamber and using biodiesel from waste chia seed oil blended with diesel. To the author’s best knowledge, this is the first study on waste Chia seed oil as a fuel in IDI engine. The injection pressure and CR of the test engine were increased from their recommended values. Biodiesel blends BC05 to BC25 with diesel in volumetric ratios of 5% to 25% respectively with 5% increments were used for experiment purpose. The results showed that biodiesel blends have lesser BTE (from 2.2% to 5%) and higher BSFC (from 3.5 to 5.2%) compared with diesel due to lower CV. With the increase in injection pressure and CR, the difference in BTE and BSFC got reduced because of better atomisation and mixing. The CO and NOx emissions are 9.26% and 27% lesser for the BC20 blend.

Numerical simulation of collision removal of inclusion in swirling flow tundish

Abstract The SFT (swirling flow tundish) is a kind of tundish with SC (swirl chamber) placed in the flow injection zone. The gravity potential energy of the molten steel is converted into rotation kinetic energy as entering into the tundish from the bottom of the SC along the tangential direction. The inclusions tend to collide and aggregate as following the rotating molten steel in the SC. In this work, the collision-coalescence behavior of inclusion was investigated by the mathematical simulation with PBM (population balance model) model, and the removal rate of the inclusion was investigated by the DPM model. The results show that, under the same operating conditions, the average diameter of inclusion at the outlet of the tundish increases from 4.25 μm to 4.35 μm with the introduction of the SC, which means that the SC promotes the collision and aggregation of inclusion. The inclusion removal rate of SFT is 33.09% without considering the collision-coalescence, and it increases into 43.20% as considering the collision-coalescence. The results of considering the collision-coalescence of inclusion is more consistent with the actual movement of inclusion in the tundish.

Experimental studies on the unsteady atomization characteristics of a swirl injector

This paper studies the spray and dynamic respond characteristics of a swirl injector under the different unsteady experimental conditions. The flow pulsation and injector geometric parameters, such as the pulsation frequency and swirl chamber length, on the atomization features like average liquid sheet thickness and spray angle have been comprehensively measured. It is indicated that the whole pulsation range could be divided into different parts based on the pulsation frequencies of incoming flow. Experimental results reveal that the liquid sheet thickness and Sauter Mean Diameter (SMD) amplitude would decrease in the square and bimodal regions and then remain unchanged in the triangular region. Both of them would increase with the tangential channel diameter and swirl chamber length while the steady incoming pressure drop shows an opposite impact on them. Besides, the spray performance of swirl injector could be improved by rising the swirl chamber diameter.

EFFECTS OF TRAPEZOIDAL SWIRL CHAMBER ON CROSS-FLOW SUPPRESSION AND HEAT TRANSFER ENHANCEMENT IN TURBINE BLADE LEADING-EDGE SWIRL COOLING

EFFECTS OF TRAPEZOIDAL SWIRL CHAMBER ON CROSS-FLOW SUPPRESSION AND HEAT TRANSFER ENHANCEMENT IN TURBINE BLADE LEADING-EDGE SWIRL COOLING

Effects of Variable Jet Nozzle Angles on Cross-Flow Suppression and Heat Transfer Enhancement of Swirl Chamber

Effects of Variable Jet Nozzle Angles on Cross-Flow Suppression and Heat Transfer Enhancement of Swirl Chamber

Investigation on the performance of an IDI engine using a novel dual swirl combustor

Indirect injection of Diesel fuel using swirl chambers is an interesting research option ever since the concept was coined by the researchers across the globe. In this typical concept, fuel is sprayed into the swirl chamber incorporated in the cylinder head of engine for primary combustion for the obvious benefit of getting lower NOx emissions keeping a low injection pressure.Typical systems use a single swirl chamber for this purpose. In this study, a novel design of swirl chamber which can produce dual swirl leading to higher turbulence, better mixing of compressed air and fuel is proposed and tested. Comparative performance and exergy analysis are done with a single swirl chamber and the newly developed dual swirl chamber. Performance testing on both the single and novel dual swirl chamber IDI engine showed that at higher loads both designs have equally good. At a load of 10kgf the BSFC and Brake thermal efficiency is identical and experimental results showed that dual swirl has lower NOx emissions, CO emission but, at the penalty of slightly higher SFC (as compared to single swirl chamber) respectively by 11.18%, is 4.47% and 0.36%. The exergy analysis of the novel dual swirl chamber and the single swirl chamber shows that the destroyed exergy of DSC is 5.65% higher compared to SSC, though input availability is more in DSC. This is the area where further research work must be done, to minimize it.

Effect of geometric parameters on spray characteristics of air assisted pressure swirl atomizer

In the present work, a modified Pressure Swirl Atomizer (PSA) was introduced to operate as an Assisted Pressure Swirl Atomizer (AAPSA). Different mass flow rates of assisted air were experimentally tested. The studied parameters are the orifice length to diameter ratio (L/Do), swirl chamber length/diameter ratio (Ls/Ds) and swirling passage size (width × depth). The spray characteristics were studied using water as the atomized liquid. The spray was photographed using a high-speed camera to determine the spray shape, the cone angle and the spray breakup length. Moreover, photos taken by the high-speed camera were processed using IMAGE J software to obtain the droplet size diameters. The spray concentrations were measured by the patternator tubes technique. The results indicated that the spray cone angle increased by increasing the value of the L/Do ratio or by decreasing the assisted air mass flow rate. The spray concentration maximum value is shifted inward with the assist air injection. The breakup length decreased by about 65% for the PSA and 77% for the AAPSA when the value of the Ls/Ds ratio is decreased from 1.163 to 0.664. With the injection of assist air at a rate of 2 g/s, the Sauter Mean Diameter (SMD) is reduced by about 64% compared to a PSA having the same geometry.

Convection in Scaled Turbine Internal Cooling Passages With Additive Manufacturing Roughness

Abstract Additive manufacturing processes, such as direct metal laser sintering (DMLS), enable the creation of novel turbine cooling internal passages and systems. However, the DMLS method produces a significant and unique surface roughness. Previous work in scaled passages analyzed pressure losses and friction factors associated with the rough surfaces, as well as investigated the velocity profiles and turbulent flow characteristics within the passage. In this study, the heat transfer characteristics of scaled additively manufactured surfaces were measured using infrared (IR) thermography. Roughness panels were CNC machined from plates of aluminum 6061 to create near isothermal roughness elements when heated. Fluid resistance differences between the aluminum roughness panels and roughness panels constructed from ABS plastic using the same roughness patterns from McClain et al. (2020, “Flow in a Simulated Turbine Blade Cooling Channel With Spatially Varying Roughness Caused by Additive Manufacturing Orientation,” ASME Turbo Expo 2020, Turbomachinery Technical Conference and Exposition, Virtual Conference, Sept. 21–25, GT2020-16069) were investigated. Finally, the overall thermal performance enhancements and friction losses were assessed through the calculation of surface averaged “global thermal performance” ratios. The global thermal performance characterizations indicate results in-line with those found for traditional commercial roughness and slightly below traditional internal passage convection enhancement methods such as swirl chambers, dimples, and ribs. The passages investigated in this study do not include compressibility effects or the long-wavelength artifacts and channel geometric deviations observed by Wildgoose et al. (2020, “Impact of Additive Manufacturing on Internal Cooling Channels with Varying Diameters and Build Directions,” ASME Turbo Expo 2020, Turbomachinery Technical Conference and Exposition, Virtual Conference, Sept. 21–25, GT2020-15049). However, the results of this study indicate that, based on the roughness augmentation alone, artificial convective cooling enhancers such as turbulators or dimples may still be required for additively manufactured turbine component cooling.

The statistical characteristic study of bubble trajectory in an axial separator by a Lagrange method

Centrifugal separation is a kind of common technology, which is used in a broad range of applications. And the axial inlet separators using the swirler to generate vortex are caught great attention owing to their compact size, low pressure drop and high separation efficiency. Some axial separators with different light phase outlet designs are introduced and their macroscopic parameters such as separation efficiency and pressure drop are investigated under different flow conditions. In order to figure out the change on flow field at different conditions, a Lagrange method was used to analyze the bubble trajectory inside an axial separator with two light phase outlets. In this paper, the single bubble was injected into the swirl chamber and the motion of the bubble was tracked by a high-speed camera. Besides, separation length defined as a parameter to evaluate the swirl intensity in the pipe was processed by statistical method. The experimental results show that a higher Reynolds number and a larger split ratio lead to a smaller separation length. Additionally, improving the proportion of split ratio of light phase outlet 1 is effective to decrease the separation length.

Study of pressure-swirl atomizer with spiral path at design point and outside of design point

Studies on pressure-swirl atomizers have mainly focused on pressure-swirl atomizers with tangential input while there are limited studies on pressure-swirl atomizers with a spiral path. This study applies experimental and computational methods to provide a better understanding of flow development in this type of atomizer at the design point and outside the design point. Experimental results showed that as the pressure increases, the spray cone angle increases. This increase initially occurs with a higher slope and then the slope is toned down. While the drainage coefficient remains constant, the droplet diameter decreases as the pressure increases. It is observed that similar to the pressure-swirl atomizer with tangential input, the pressure-swirl atomizer with a spiral path has a conical hollow spray. At the constant mass flow rate, as the spiral path cross-section, the length of the swirl chamber and orifice diameter increase, the fluid film thickness and average diameter of droplets increase while the spray cone angle reduces. Further, increasing the number of spiral paths causes a wider spray cone angle, higher discharge coefficient, larger fluid film thickness, and larger droplet diameter. The results also showed that increasing the length of the orifice marginally affected the properties of the spray while significantly reducing the spray cone angle. It is important to note that the numerical results are in good agreement with the experimental data.

A comprehensive investigation of LSTM-CNN deep learning model for fast detection of combustion instability

In this paper, we propose a deep learning model to detect combustion instability using high-speed flame image sequences. The detection model combines Convolutional Neural Network (CNN) and Long Short-Term Memory network (LSTM) to learn both spatial features and temporal correlations from high-speed images, and then outputs combustion instability detection results. We also visualize the extracted spatial features and their temporal evolution to interpret the detection process of model. In addition, we discuss the effect of different complexity of CNN layers and different amounts of training data on model performance. The proposed method achieves superior performance under various combustion conditions in swirl chamber with high accuracy and a short processing time about 1.23 ms per frame. Hence, we show that the proposed deep learning model is a promising detection tool for combustion instability under various combustion conditions.

INFLUENCE OF THE MEASURING TOOLS ON THE FLOW CHARACTERISTICS IN VORTEX CHAMBER PUMP

Problem. Perturbation of the flow by measuring instruments forces researchers to choose optical research methods. But these methods significantly increase the cost of experimental research, due to the high cost of optical-type measuring equipment. On the other hand, using contact methods for measuring the flow velocity, such as Pitot tubes, hot-wire anemometers, the researcher must be sure that the measurement results can really be compared with the calculations results and the equipment influence on the flow parameters is minimal. The aim of this work is to study the measuring tool influence on the flow characteristics in the swirl chamber pump, as well as to compare the results obtained due to the measurements with the parameters of the undisturbed flow. The research methodology consisted of two stages: 1) modeling the flow in the model pump; 2) comparison of flow characteristics, as well as the values of velocity and pressure at the points of installation of the measuring tool. Results. Although the total velocity at the measuring point is practically independent of the measuring tool, the tangential component of the velocity is significantly reduced. It indicates that there is a significant error in velocity measuring. For a more accurate rotational velocity component measurement, it is necessary to orient the instrument perpendicular to the measured component. Scientific novelty. Installing the measuring tool in the end cover of the swirl chamber reduces the flow rate sucked by the pump through the lower axial channel. The size of the tool has practically no effect on the energy characteristics of the swirl chamber pump. Practical value. To ensure measurement accuracy, the ratio of the swirl chamber dimensions and the tool should be ensured in the way that the relative diameter of the tool does not exceed 0.25 of the swirl chamber neck diameter.

Modified selective non-catalytic reduction system to reduce NOx gas emission in biodiesel powered engines

Biodiesel fuels releases higher NOx emissions than fossil diesel. The Selective Catalytic Reduction (SCR) technique used in the OEM industry is not suitable for application in small engines due to back pressure and clogging problems. Selective Non-Catalytic Reduction (SNCR) is used in relatively large combustion operations. This study introduces a new design by combining SCR and SNCR systems, for use in low power density diesel engines. The system composed of injection-expansion pipe and swirl chamber. The working principle is maximum mixing of the injected fluid and exhaust gas in the expansion chamber, then creating a maximum turbulence in the swirl chamber. This way NOx emission can be reduced at relatively lower exhaust temperatures without using any catalyst. The CFD models of three design candidates were examined in terms of velocity magnitudes, turbulence intensity and particle residence time. The selected design was manufactured and tested. Distilled water and urea-water solution were injected separately at the same flow rate of 375 ml/min. Exhaust emissions of fossil diesel, sheep fat biodiesel – waste cooking oil biodiesel blend and chicken fat – cottonseed biodiesel blend were tested. No significant changes in CO2 and HC gases were observed. Distilled water injection reduced CO and NO emissions by about 10% and 6% for fossil diesel; and by about 9% and 7% for biodiesels operation respectively. The urea-water injection led to reductions in CO and NO emissions by about 60% and 13% for fossil diesel; and by about 45% and 15% for biodiesels respectively.

Numerical study on swirl cooling flow, heat transfer and stress characteristics based on fluid-structure coupling method under different swirl chamber heights and Reynolds numbers

In this study, a three-dimensional swirl cooling model coupled with high temperature mainstream cascade channel and blade leading edge solid region is established to simulate the flow, heat transfer and stress characteristics. The fluid-structure coupling model is utilized to analyze the interaction of external mainstream, solid blades and swirl cooling air. Six different swirl chamber heights are selected to explore the optimal height which is the most beneficial to gas turbine blade operation. Finally, influences of coolant chamber inlet Reynolds number on swirl cooling performance are discussed in detail. Results show that the temperature distribution of blade solid region is highly related to swirl cooling effect. Compared with aerodynamic load, the thermal load behaves more significant effects for blade stress conditions. As the swirl chamber height increases, the swirl cooling heat transfer performance gradually decreases, and the flow resistance also gradually decreases. The comprehensive heat transfer factor is introduced to evaluate the swirl cooling overall performance. When swirl chamber height is 19 mm, it has higher heat transfer capacity and lower flow resistance, and the comprehensive heat transfer factor is the highest. The Reynolds number has a strong influence on heat transfer performance. In order to avoid high aerodynamic losses, the Reynolds number should be selected appropriately.