Compressor Wheel Research Articles

Cooling System of A High-Pressure Centrifugal Compressor: Development and Impact on Wheel Temperatures (GT2024-121464)

Abstract High power density, low fuel consumption, and a compact design with competitive total costs of ownership are key requirements for internal combustion engines for conventional fuels and carbon-free or carbon-neutral future fuels. These requirements influence the development targets of charging systems and call for single-stage charging systems with increased charge air pressures. However, high compressor pressure ratios of the turbocharger lead to challenging material temperatures in aluminum alloy wheels. Consequently, creep becomes the fundamental lifetime-limiting damage mechanism for these wheels. In order to meet customer requirements regarding total costs of ownership, the lifetime is of major importance for the development of aluminum compressor wheels for turbochargers with pressure ratios beyond 6. This paper focuses on a high-pressure compressor design with a water-cooling system for a new turbocharger generation. The development of its components and their validation based on numerically predicted and measured wheel temperatures are discussed. After introducing the need for high-pressure ratios and the accompanying lifetime challenges, the paper presents the design strategy and methods of the development process. Finally, the paper summarizes the achievements obtained by this procedure. Detailed and rarely before documented temperature measurements from the rotating compressor wheel are published. As will be shown, the temperature measurements confirm the predictions from the pre-development phase. A comparison of the temperature measurements from the recently developed wheel with measurements carried out for a state-of-the-art wheel reveals the improvements achieved by this new generation of high-pressure compressors.

Evaluation Strength of Materials of the Compressor Wheel and Engine Power in the Turbocharger

Evaluation Strength of Materials of the Compressor Wheel and Engine Power in the Turbocharger

Design of herringbone grooved thrust bearing for locomotive turbocharger rotor

The herringbone texture exhibited excellent tribological performance to minimize friction and wear. However, the application of this texture in the development of grooved thrust bearings is limited. Therefore, in this study, an attempt was made to design an oil-lubricated herringbone grooved thrust bearing for high-speed locomotive turbochargers. The designed bearing accommodates the axial load generated due to the pressure difference between the turbine and compressor wheel. The bearing design starts with applying Newton’s second law to predict the thrust load acting on the locomotive turbocharger rotor. The thrust load is calculated analytically and is found to be 4.54 kN for a design rotor speed of 1,00,000 rpm. Further, the herringbone grooved thrust bearing has been modeled numerically using non-linear Reynolds equation. The modified Reynolds equation is discretized using the finite volume method (FVM) and solved by successive over-relaxation (SOR) methodology to determine the static characteristics over the bearing surface. The developed HGTB is found to have a suitable load-carrying capacity of 4.6 kN, frictional torque of 0.25 N.m, and power loss of 2.98 kW. Further, a parametric analysis has been carried out to study the influence of design parameters such as the number of grooves, helix angle, angular groove width, groove depth, and speed on load-carrying capacity, frictional torque, and power loss.

Microstructure and properties of high-entropy-superalloy microlattices fabricated by direct ink writing

Ni-Co-Fe-based high-entropy superalloys (HESAs) are fabricated into microlattices via a three-step process: (i) layer-by-layer extrusion of inks containing elemental powders (Ni, Co, Fe, Cr, Ti) and TiAl3 powders; (ii) sintering to densify and homogenize the struts; (iii) aging to achieve a γ/γ’ microstructure. The struts of the microlattices show a nearly pore-free and fully-homogenized microstructure. Increasing the Ti concentration from 4 at% (Al9Co26Cr7Fe16Ni38Ti4) to 9 at% (Al8Co25Cr7Fe15Ni36Ti9) leads to a significant increase in the volume fraction of strengthening γ’ precipitates, from 51 to 78 %. Furthermore, in the Ti-rich composition, the γ' precipitates exhibit a sharp-edged cubic morphology with larger sizes and higher lattice misfit (0.63 %) with respect to the γ matrix. As a result, Ti-rich HESA microlattices show higher strength at ambient temperature than Ti-poor ones, while retaining high compressive ductility (> 60 %). They also demonstrate superior specific strengths when compared to bulk Inconel 617 and other representative bulk HESA, up to 1000 °C. The combination of low-density (2.29–3.15 g/cm3), high strength at elevated temperatures, and high processability positions HESA microlattices from direct ink writing as promising candidates for structural components in extreme operating conditions. The versatility of the process is demonstrated by printing and sintering three miniature HESA objects with complex shapes (hollow turbine blade, gyroid heat exchanger, and compressor wheel).

Water Droplet Collison and Erosion on High-Speed Spinning Wheels

<div>The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage. One such fluid is the condensed water in the low-pressure exhaust gas recirculation channel (LP-EGR) formulated at cold starts and low-speed high load conditions. This kind of design has been developed to reduce nitrogen oxide emissions and is used in both gasoline and diesel engines. This article presents a state-of-the-art review of this WDE process, focusing on the formation of the condensed water before the compressor wheel, summarizing the influencing factors of WDE and the effects of the damage including using component testbench experiences and simulation methodologies. Inspection possibilities such as high-speed camera measurement and vibration analysis are also an important part of the document.</div>

Parallel turbochargers for small-scale power generation

For countries with insufficient power supply and failing power grid infrastructure, it is usually also expensive to import microturbines. Local manufacturing or local assembling in these countries is therefore an attractive solution. Off-the-shelf turbochargers used in the motor vehicle industry are readily available at relatively low costs because of large-scale manufacturing in this sector. A turbocharger can be developed into a microturbine for power generation; however, coupling a turbocharger shaft directly to a high-speed generator or gearbox can be challenging and complex due to the high speeds and high temperatures involved, as well as the limited space available on the shaft for such a conversion. The novelty of this work was to investigate the effect of mounting two off-the-shelf turbochargers in parallel, where the second turbocharger’s compressor wheel is replaced with a generator. This allows for a higher pressure ratio over the power turbine. A parallel configuration may also have an advantage over a series configuration in terms of cost since the power turbine can be smaller in size. Two different parallel configurations were modelled, namely, a low-temperature turbine (LTT) and a high-temperature turbine (HTT), where the only difference was the position of the power turbine in parallel with the main shaft. Both configurations were modelled at steady state up to compressor pressure ratios of 2, with and without a recuperator, and with and without pressure losses. It was found that the recuperated LTT configuration outperformed the recuperated HTT configuration in terms of efficiency when pressure losses were introduced. Results showed that the optimum LTT combination generated up to 4.06 kW of power at 87 kPa ambient pressure, with a thermal efficiency of 13.26 %, when coupled with a 90 % effective recuperator. For the same case, the HTT configuration produced a maximum efficiency of 8.66 % with a power output of 5 kW.

Rotordynamic Analysis and Operating Test of an Externally Pressurized Gas Bearing Turbo Expander for Cryogenic Applications

This study designed an externally pressurized bearing and analyzed the rotordynamics of a turbo expander for a hydrogen liquefaction plant. The turbo expander, comprising a turbine and compressor wheel assembled to a shaft, lowered the temperature of the helium refrigerant. Its rated speed was 75,000 rpm, and an externally pressurized gas bearing was selected to support the rotor. Pressurized helium was used as the lubricant for the bearing operation. To design the rotor–bearing system, we conducted a bearing performance analysis and rotordynamic characteristic prediction using the developed numerical model. We calculated the bearing stiffness and flow rate of the bearing gas for various feed parameters and selected the appropriate orifice diameter for maximum stiffness. The predicted Campbell diagram showed that the system had a sufficient separation margin with the critical speed, and the predicted critical speed correlated well with the nonlinear orbit simulation. A successful operation was achieved with the manufactured turbo expander within the rated speed. The shaft vibration was monitored during the operation test, and the test results revealed two critical speeds below the rated speed, as predicted by the analytical model. In addition, the shaft vibration was maintained at <3 μm.

СОЗДАНИЕ ЦИФРОВОГО ДВОЙНИКА ПРОЦЕССА СБОРКИ РАБОЧЕГО КОЛЕСА КОМПРЕССОРА

A digital dual compressor wheel assembly process has been developed to predict the angular rotations of the blade assembly rotating as it rotates. The calculated angles characterize the tension in the joints of the end flanges of the blades. At the input of a digital double sequence of data on geometry deviations with control of operations on parts. During the implementation, the random forest method was used, the study of which was carried out on a set of calculated experiments performed in the ANSYS environment using the element model of the assembled impeller. The experimental results show that the calculation error does not exceed 15 minutes of arc.

Influence of the low-pressure exhaust gas recirculation injection point on engine performance

The use of low-pressure exhaust gas recirculation (EGR) has been extended in spark-ignited engines in recent years due to advantages from efficiency perspective. However, the potential condensation of the water contained in the exhaust gases and eventual compressor erosion can limit the usage of such systems during engine warm-up and/or cold ambient conditions. One possibility to avoid condensation at cold ambient is to place the EGR injection close to the compressor wheel, avoiding a complete mixture of both streams, but it alters the flow distribution upstream of the compressor, potentially affecting its performance. In order to assess the impact of this phenomenon in engine operation, a detailed experimental campaign in a state-of-the-art spark-ignition engine was performed comparing this close-coupled configuration with another one where the injection point was far upstream the compressor, ensuring a perfect mixing. A previously developed and validated one-dimensional model of the variable geometry turbocharger was used to analyze in further detail the compressor and turbine operation. The results show a general deterioration of the engine pumping mean effective pressure (up to 0.02 bar) and the specific fuel consumption (up to 4 g/kWh) when applying the close configuration, higher as the EGR rate increases, which is partially due to the change in turbine operation induced by the new compressor working point.

Engine performance improvements through turbocharger matching and turbine design

AbstractIt is interesting to improve engine system performance with turbocharger technologies. In this study, a systematic simulation for engine and turbocharger matching to provide full utilization of the turbocharger potential and improve the engine performance without sacrificing the emission is developed. A velocity ratio concept was proposed to count the turbocharger performance impacts due to the diameter ratio of compressor and turbine wheels. A design of experiments was used to optimize the turbocharger and engine performance for different turbocharger factors. A better‐matched turbocharger was obtained. A multidisciplinary optimization method was used to design a mixed flow turbine wheel to reduce the turbine velocity ratio at peak efficiency and increase the overall turbocharger efficiency. Results showed that about 0.4% torque improvements and 1.2% reductions in the engine brake‐specific fuel consumption were obtained without making any other changes to the engine. This study demonstrated that systematic simulations for engine systems and considering turbocharger wheel diameter ratio effects could further improve the turbocharged engine system matching and the engine performance.

Flow-noise characteristics of turbocharger compressors with rotational balance cuttings

To correct the balance of the rotating assembly of a turbocharger, some parts of the compressor wheel are removed by cutting. A numerical investigation of the turbulent flows and flow noises produced by compressor wheels modified with such cutting parts was performed by a turbulence model and detached-eddy simulations. For the 6-cutting case, 0, 2, 4, and 6 circular cuttings and two additional—rectangular and triangular—shapes were used. To investigate the effects of the balance cuttings in a compressor wheel, the evaluation process using computational fluid dynamics was tried. It was found that the fluid forces due to the various wheel shapes have the potential to restore the eccentricity by approximately 50%. Severe variations of velocity, pressure, and turbulent kinetic energy in the interspace between the wheel and volute were observed. In particular, the wavelike patterns of pressure and turbulent kinetic energy were intensified for the modified wheels. The turbulent kinetic energy of the 6-cutting case had a dominant frequency at approximately 3000 Hz. The spectrum of the sound-pressure level of the modified compressor wheels exhibited the features of buzz-saw noise. The flow fields suggested that this feature of the sound pressure is related to the tip-clearance flow affected by the balance cuttings. In addition, the acoustic pressure and flow characteristics of the different types of modified compressor wheels were discussed and the resulting acoustic power was evaluated.

Effect of balanced edge cutting configurations on the aeroacoustics of high-speed turbomachinery

Abstract Flow-noise corresponding to the balanced edge cutting configurations on the compressor wheel of a turbocharger is investigated in this study. The turbocharger is a type of high-speed turbomachinery that rotates at up to 2.0×105 RPM. Microscopic air bubbles are generated inside the compressor wheel due to inaccuracies in the cast introduced in the production process. These bubbles cause a mass-unbalance phenomenon when operated at high rotational speeds, which even leads to breakage in severe cases. To prevent theses problems, cutting configurations are utilized at various locations on the rear of the wheel. However, the cutting shapes rather produce severe vortices from a flow perspective, which has a significant effect on the flow noise. Therefore, after calculating the steady-state shear stress transport k-ω based on the Reynolds-averaged Navier-Stokes equation model, transient large eddy simulation was conducted from initial values using the commercial computational fluid dynamics software, ANSYS FLUENT V20.2. The flow-noise was calculated based on unsteady analysis data with the Ffowcs-Williams and Hawkings equation. The flow-noise of the balanced edge cutting configurations of turbocharger compressor wheels was calculated according to various receiver points, and rotational velocities. Results show that various noise characteristics occur depending on the rotational speeds and the receivers depending on the cutting configurations.

Aerodynamic investigation on compact variable compressor for vehicular turbochargers

Abstract In order to install a turbocharger which has wider operating range and higher boost pressure than a current supercharging system to an internal combustion engine (ICE) and a hybrid vehicle (HV), one development focus lies on a variable trim compressor (VTC) which can change passage area upstream a compressor wheel. In this paper, a new variable geometry device which was developed from the VTC mechanism proposed by Fujiwara et al. in 2018 is studied. The experimental result confirmed the performance enhancement associated with the design concept change and the improvement of trim actuation. In addition, the effect of the throat area ratio as design parameter in the new device on performance was numerically analysed. As a result, the optimal design value of passage area size in the VTC was around 60% and the passage area change position should be placed as close as possible to the compressor wheel.

Integral Design of a Turbocharger for Internal Engine Energy Saving: Centrifugal Compressor Design

Abstract Energy savings and emission reductions are essential for internal engines. Turbocharger is critical for engine system performance and emission. In this study, the engine simulation program was used to systematically optimize the engine turbocharger system performance. The velocity ratio concept was used in the engine simulation program to consider the performance impacts of the wheel diameter ratio between compressor and turbine. An integral consideration for both compressor and turbine was proposed to design the new turbocharger. An optimization process was used to design the compressor. The performance and mechanical integrity assessments for final designs by using computational fluid dynamics (CFD) and finite element analysis (FEA) solvers were reported in this paper. The optimized compressor wheel has some distiguished features comparing with conventional designs. In this design, the splitter is not located at the middle between the two main blades; the compressor wheel exit diameter at shroud is larger than exit diamerer at the hub. The new compressor was tested on both gas stand and engine. The numerical results are fairly agreed with gas stand tests. The tests showed about 1.2% of the engine BSFC reduction without sacrificing the emission and cost. This study demonstrated that a systematic method in simulation and a compressor design optimization process could optimize the engine system and improve the engine performance.

The analysis of a hybrid turbocharger main parameters applied to an internal combustion engine

Internal combustion engines are constantly developing. Currently, a solution in full development is a hybrid car that has an internal combustion engine propulsion combined with an electrical motor. The electrical motor is powered by a battery which in turn is connected to other electricity suppliers for recharging. Therefore, the aim is to recover the thermal energy from the car, through various solutions, in order to transform it into electricity. Electricity is for the car’s battery as well as for its consumers. After an analysis of the energy balance of the internal combustion engine, it can be seen that the engine energy still has great potential to be transformed into electrical energy through various solutions. Electrical energy can be produced even from braking or other mechanical devices that transform mechanical energy into electrical energy. For example, a co generator of energy hybrid electric turbocharger aims to recover exhaust gas energy and to capitalize it. The turbocharger is connected through a shaft with a generator. Between the compressor wheel and the generator is a speed reducer with a gear ratio of 1:10. This article aims to present the analysis based on the results of the experimental and simulation research of the hybrid turbocharger. The tests were performed using a diesel internal combustion engine with 4 cylinders at a capacity of 1.9 liters. The simulations will be performed using AMESim software developed by Siemens. The main parameters, which are highlighted, are: pressure ratio of the turbocharger, the rotation speed of the turbocharger and the power from the experimental results in relation to time and engine power at 100% load.

Development of efficient compressor wheel for turbocharger by varying number of blades

The present work is done to find out the change in the efficiency of the compressor wheel by varying the number of blades and the velocity and pressure variation at a particular speed. Efficiency values are observed oncalculated pressure ratio versus corrected air flow graph for varying number of blades on standard compressor map of GT-15 Turbocharger. GT–15 Turbocharger is considered for the analysis, which is used in sports vehicles. Modelling of compressor wheel is done by 3D modelling software PTC Creo parametric 2.0 and mesh generation is done by using Computational Fluid Dynamics (CFD) tools. The model is solved with a different number of blades i.e., 10, 12, and 15. An approach to increase the efficiency of the compressor wheel by increasing the number of blades is studied.

Numerical assessment of mixing of humid air streams in three-way junctions and impact on volume condensation

Flow mixing at three-way junctions is widely studied due to its usage in countless applications. Particularly, in air conditioning and internal combustion engines, the mixing of humid air streams can lead to volume condensation, provided that any local temperature achieves dew conditions. This work investigates and quantifies the correlation between mixing intensity and generated condensation. A method to define mixing indexes is developed, comparing its performance against literature references that employ temperature or passive scalar to evaluate mixing. A numerical campaign of 128 Reynolds-Averaged Navier Stokes three-dimensional (3D) simulations is designed to explore different junction operating conditions. A validated condensation submodel embedded in the 3D model enables the quantification of condensation at the junction outlet, which also can be estimated by means of a 0D model that provides the psychrometric state of a homogeneous mixture between the inlet streams. A strong linear correlation is found between condensation and the product of mixing indexes and 0D condensation mass flow rate, since the latter carries the psychrometric information of the working point. This connection allows to find junction design guidelines to reduce mixing and therefore condensation. Additional simulations confirm that removing junction valves, reducing mixing length, increasing the branch duct diameter and aligning the branch leg with the outlet duct significantly decrease condensation. In the framework of low pressure exhaust gas recirculation (EGR), this condensation damages the compressor wheel. If junctions are designed as suggested, the current constraints over EGR rates to limit condensation can be removed, which will result in internal combustion engines with lower emissions and better fuel consumption. • A new definition of mixing index is developed by calculating the unmixed area. • Flow mixing and condensation at T-junctions is assessed using 0D and 3D models. • Condensation is strongly correlated with psychometric conditions and mixing. • Mixing is reduced by decreasing length and momentum ratio and relocating valves. • Guidelines to design junctions with reduced volume condensation are provided.

Erosive wear characteristic of Mo-TiN composite coatings on turbocharger compressor wheel using Taguchi experimental design

In the present work, Mo coating (S1) and Mo–TiN coatings with varied compositions (S2: Mo–5 wt% TiN, S3: Mo–10 wt% TiN, and S4: Mo–15 wt% TiN) were deposited using atmospheric plasma spray system on to Al-Si substrate. The solid particle erosion wear response of these coatings was studied following Taguchi experimental design. The signal-to-noise ratio was analyzed to investigate the influence of operating parameters (torch input power, erodent size, impact velocity, erodent temperature, impingement angle) on the erosion wear rate. In the case of Mo-coatings, erodent size is found to be the most influencing parameter. However, with incorporation of TiN powder to the molybdenum matrix, torch input power level is playing a significant role. Erosion rate is found to be decreased with increasing torch input power in the range of 15–30 kW in Mo-TiN coatings. In Mo–10 wt% TiN coating (S3), the least erosion rate is observed at 30 kW. The surface morphology of the eroded coatings shows less micro-cracks in S3 coating compared to others.

Design of Aircraft Air Conditioning System Turbomachine with Electric Compressor and Use of Vapor Compression and Water Evaporation Cooling

BACKGROUND: Traditionally, air is taken from engine compressors to address the needs of aviation air conditioning systems (ACSs) because the air in the environment is rarefied, and maintainining a high pressure that is comfortable for passengers is required in the cabins [1–3]. This solution consumes a considerable amount of energy because the air is extracted from compressors at significantly high pressure. Therefore, the ACS works at all flight altitudes.
 The use of ACS without air extraction from airplane engines with an autonomous electric compressor is proposed [5–7]. As a cooling unit, the utilization of a combined scheme using a traditional air cycle with a turbo cooler and a vapor compression refrigeration machine with the possibility of operation in heat pump mode and additional water evaporative cooling is proposed.
 This work aims to calculate and justify the energy efficiency of the proposed scheme of aircraft ACS without air extraction from the marching engines and auxiliary propulsion system using an electric compressor, a steam compression refrigeration machine with heat pump mode, and water vapor cooling. The paper also aims to design and compare the turbo compressor impeller using traditional methods and modern modeling tools to conclude its prospects.
 METHODS: Computational comparative study of traditional and proposed schemes of ACS. Calculation of compressor wheel flow part using traditional methods and CFX modeling.
 RESULTS: A reduction in power consumption of ACS during summer parking on the ground by 10 times and that in cruising flight by 16.6 times is observed when using the proposed scheme. The comparison result of calculations of the turbine unit using the classical method and CFX modeling revealed that the same initial data yielded a slightly different geometry of the impeller. This difference is due to modeling, which considers the reality of the properties of the working gas and internal overflows.
 CONCLUSION: The proposed scheme of ACS has considerable energy efficiency. Thus, conducting a comprehensive comparative analysis with traditional solutions on all indicators is reasonable. Overall, 3D modeling of the turbomachine flow part shows a real illustration of parameter changes. However, using 2D modeling for approximate and preliminary calculations is reasonable because it solves the problem quite accurately.

Design and Modeling of 2 MW AMB Rotor With Three Radial Bearing-Sensor Planes

Active magnetic bearings (AMBs) provide reliable solution for high-speed rotors, where oil-free and reliable operation are crucial. In high-power applications benefits of AMBs, compared to traditional rolling element bearings or fluid film bearings, are highly valued. Typical AMB rotors comprise two radial AMBs, which are designed with compressor or generator wheels integrated on the rotor. AMB dimensions and locations are carefully selected for each new application. The system design is being iterated such that the nodes of the lowest frequency rotor bending modes are sufficiently far away from the AMB and sensor nodes to ensure robust AMB control. The design is very challenging and cost sensitive. This work focuses on electromagnetic design, modeling, and control of fully levitated AMB-rotor with three radial AMBs. The additional bearing ensures that the same design can be reused with different applications and regardless of the changes in locations of nodes of the first bending mode. The control plant is modeled based on flexible rotor dynamics; while bearing inductances and forces are modeled with 2-D and 3-D finite element method (FEM) electromagnetic simulations. The presented multi-input multi-output (MIMO) model-based control is coupled and centralized with three actuator-sensor pairs for radial suspension. The control design is verified in simulations using nonlinear engineering models. Additionally, experimental identification results are included.