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

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 final designs employed Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) solvers for the performance and mechanical integrity assessments. The optimized compressor wheel has different features comparing with conventional designs. In this design, the splitter is not located in the middle between main blades; the compressor wheel exit diameter at shroud is larger than 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 sacrifice the emission and cost. This study demonstrated that a systematic method in simulation and an integral compress design process could optimize the engine system and improve the engine performance.

Advanced Engine Technologies for Turbochargers Solutions

Research in the process of internal combustion engines shows that their efficiency can be increased through several technical and functional solutions. One of these is turbocharging. For certain engine operating modes, the available energy of the turbine can also be used to drive an electricity generator. The purpose of this paper is to highlight the possibilities and limitations of this solution. For this purpose, several investigations were carried out in the virtual environment with the AMESim program, as well as experimental research on a diesel engine for automobiles and on a stand for testing turbochargers (Turbo Test Pro produced by CIMAT). The article also includes a comparative study between the power and torque of the naturally aspirated internal combustion engine and equipped with a hybrid turbocharger. The results showed that the turbocharger has a very high operating potential and can be coupled with a generator without decreasing the efficiency of the turbocharger or the internal combustion engine. The main result was the generation of electrical power of 115 W at a turbocharger shaft speed of 140,000–160,000 rpm with an electric generator shaft speed of 14,000–16,000 rpm. There are many constructive solutions for electrical turbochargers with the generator positioned between the compressor and the turbine wheel. This paper is presenting a solution of a hybrid turbocharger with the generator positioned and coupled with the compressor wheel on the exterior side.

On the Challenge of Determining the Surge Limit of Turbocharger Compressors: Part 1 – Experimental and Numerical Analysis of the Operating Limits

The surge limit of compressors is one key parameter in the design process of modern turbocharger compressors for automotive applications. Since the compressor is operated close to the surge limit, the determination of the surge limit is of high importance. Unfortunately, the determination of the surge limit with any numerical method with high accuracy is still an unsolved challenge. The numerical surge limit is often determined by the operating point with the minimum converged mass flow rate. But, as this investigation will clearly show, this cannot be used as a surge limit of the investigated compressor configuration. In this paper it will be shown that a more differentiated approach is required when it comes to operating limits. Especially, two different operating limits can be determined. A methodology for the determination of each limit will be presented. One is based on the system approach defined by Greitzer and the other one is based on the analysis of the low momentum fluid in the shroud region of the compressor wheel. Finally, experimental data will be used as benchmark data for both limits. The determination of the experimental surge limit is based on the analysis of transient experimental pressure signals. This is achieved through a fourier analysis of the unsteady compressor outlet pressure signal for transient surge runs.

Finite Element Method modeling of Additive Manufactured Compressor Wheel

Designing components is a complex task, which depends on the component function, the raw material, and the production technology. In the case of rotating parts with higher RPM, the creep and orientation are essential material properties. The PLA components made with the material extrusion process are more resistant than VeroWhite (material jetting) and behave similarly to weakly cross-linked elastomers. Also, based on the tensile tests, Young’s modulus shows minimal anisotropy. Multilinear isotropic hardening and modified time hardening models are used to create the finite element model. Based on the measurements, the finite element method simulation was identified. The deformation in the compressor wheel during rotation became definable. It was concluded that the strain of the compressor wheel manufactured with material extrusion technology is not significant.

Evaluation of Variable Compressor Technologies

A diverse set of technology solutions are in development for reducing vehicular CO2 emissions. Beside the conventional internal combustion engine, there are hybrid powertrains, fuel cells and full electric vehicles. The challenge is finding the right technology that can be quickly implemented into production as a cost effective solution. In addition to CO2 reduction during vehicle operation, the impact of CO2 in the production and recycling of future vehicles must also be considered. From this perspective, the role of turbocharging is evolving, becoming more important for the future. It is an enabler for mature technologies known to improve engine efficiency like Miller timing, lean burn, increased exhaust gas recirculation (EGR) dilution and exhaust heat recovery. As a boosting device, improved turbocharging can also benefit other powertrain types like fuel cells. All previously mentioned applications benefit from wider compressor maps and higher compressor ratios. To achieve an extension of the performance map to areas of low mass flow rate, different methods have been discussed with the two most promising being trim reduction introduced by IAV’s Variable Trim Compressor (VTC) and swirl generation. The most common device for inducing a swirl onto the incoming airflow is to use swirl generating wings in front of the compressor wheel. However, Iwakiri explained that putting a single plate in front of the compressor wheel disturbs the recirculating flow, which acts positively to extend the compressor map. On this basis, plates were developed that guide the strongly swirled back flowing air in such a way that they impose a swirl on the incoming air. Trim reduction is well known for its ability to shift the surge line and maintain compressor efficiency. To achieve this, a conical element before the compressor wheel guides the incoming flow to the inner area of the wheel resulting in reduced flow separation. An orifice can also achieve almost the same effect but with much less axial extension. The advantages and disadvantages of these measures are explained using numerical (CFD) and experimental (turbocharger test bench) to show the potential of each approach. In summary trim reduction using a conical geometry is still the best performing approach. However, considering package restrictions, an orifice is also a good choice. Whereas swirl producing principles have a moderate impact on shifting the surge line. The extension of high mass flow rate is also of interest and this study shows a simple method to improve the compressor performance map in this area. A combination of the measures to expand the map in both directions is conceivable and is presented here as a concept.

Finding the optimal compressor impeller material to improve the efficiency of the turbocharging system

Vehicles powered by diesel engines are equipped with superchargers in order to improve the ef-ficiency of vehicles. The efficiency of the turbochargers themselves partly depends on the optimum performance of their impellers, which in turn is achieved by choosing the right impeller materials. An important property of the material of the turbine wheel is heat resistance to the incoming exhaust gases, and for the compressor wheel it is the resistance to the pressure of the air simultaneously supplied to it and forced by it. In this paper, the issue of increasing the efficiency of the turbocharging system is considered in the context of comparing three materials (nickel and titanium alloys, structural steel), which are proposed for the manufacture of a compressor impeller by designing its model using computer software products. The measurements of real turbocharging elements and their characteristics are transferred to CREO, where the required dimensions are calculated and other necessary calculations are carried out, which are then imported into ANSYS for the purpose of subsequent research, in-cluding thermal and structural analyzes. Comparison of the analysis results allows us to conclude that the nickel alloy is superior to other materials under consideration in terms of its minimum sus-ceptibility to deformation and obtaining the lowest total heat flux in the compressor impeller, and to recommend this material for use in turbocharging or for its subsequent comparison with previously not considered materials, which, as suggested in the study, to some extent can contribute to an in-crease in the efficiency of the vehicle.

Additively Manufactured Parts Made of a Polymer Material Used for the Experimental Verification of a Component of a High-Speed Machine with an Optimised Geometry—Preliminary Research

This paper describes a novel method for the experimental validation of numerically optimised turbomachinery components. In the field of additive manufacturing, numerical models still need to be improved, especially with the experimental data. The paper presents the operational characteristics of a compressor wheel, measured during experimental research. The validation process included conducting a computational flow analysis and experimental tests of two compressor wheels: The aluminium wheel and the 3D printed wheel (made of a polymer material). The chosen manufacturing technology and the results obtained made it possible to determine the speed range in which the operation of the tested machine is stable. In addition, dynamic destructive tests were performed on the polymer disc and their results were compared with the results of the strength analysis. The tests were carried out at high rotational speeds (up to 120,000 rpm). The results of the research described above have proven the utility of this technology in the research and development of high-speed turbomachines operating at speeds up to 90,000 rpm. The research results obtained show that the technology used is suitable for multi-variant optimization of the tested machine part. This work has also contributed to the further development of numerical models.

ДІАГНОСТИКА ТУРБОКОМПРЕСОРА ДИЗЕЛЬНОГО ДВИГУНА ЗА ДОПОМОГОЮ АНАЛІЗУ ВІБРОАКУСТИЧНОГО СПЕКТРУ

The method considered in the article consists in the analysis of the vibroacoustic signal generated by the compressor of the gas turbocharger during the operation of the diesel engine under load. Spectral analysis shows that the compressor blades generate vibrations that are always present in the spectrum of the general vibration of a gas turbocharger, regardless of its technical condition. The "blade" harmonic in the spectrum corresponding to these oscillations is determined using the method of limitations. The then calculated instantaneous rotor speed of the turbocharger makes it possible to analyze the amplitude of the fundamental harmonic in the spectrum. For numerical analysis of the amplitude of the fundamental harmonic, the power leakage of the discrete spectrum is eliminated. Further analysis of the amplitude of the fundamental harmonic makes it possible to quickly assess the level of vibration of the rotor during operation. The first part of the experiment was carried out on a ship's main diesel engine 5S60MC at a crankshaft speed of 85 min-1. The recording and analysis of vibroacoustic signals from the TCA 66-20072 turbocharger was carried out. The analysis showed the possibility of highly accurate determination of the rotational speed and the relative amplitude of the turbocharger shaft oscillations. The second part of the experiment was carried out on an experimental stand, which is based on a KamAZ-740.10 engine with an original pressurization system. A turbocharger of the TKR-11 type is used as a pressurization unit. As a result of the experiment, it was shown that the method of diagnosing the operation of a turbocharger, which is based on the analysis of a vibroacoustic signal, can be extended not only to turbochargers of low-speed engines, but also to turbochargers of high-speed diesel engines. In this case, the spectrum of the measured signal contains harmonics, the frequencies of which make it possible to determine the crankshaft rotation frequency. It is also shown that measuring the signal outside the compressor, close to its casing, makes it possible to obtain all the necessary diagnostic parameters as accurately as when measuring the signal directly at the inlet to the compressor wheel. The method can be used in practice. To implement it, a smartphone and a computer with special software are enough. The proposed method can be used as the basis for a system for continuous monitoring of the frequency and vibration level of a marine diesel engine turbocharger.