Turbocharger Speed Research Articles

Impact of cylinder deactivation on fuel efficiency in off-road heavy-duty diesel engines during high engine speed operation

Off-road heavy-duty diesel engines are equipped with complex aftertreatment systems to meet the stringent EPA Tier 4 emission standards. Traditionally, the thermal management of the aftertreatment system, aimed at efficiently reducing tailpipe emissions, involves controlling engine exhaust flow and temperature. However, this approach often leads to inefficient engine operation, especially in the low to mid-load regions, resulting in higher fuel consumption. Prior studies have highlighted the potential of cylinder deactivation (CDA) in reducing fuel consumption and increasing the exhaust temperature for thermal management in on-road applications. As the significance of controlling greenhouse gas (GHG) emissions from off-road machinery comes into focus, this study aims to experimentally demonstrate the fuel efficiency benefits and efficient aftertreatment thermal management achieved through CDA during high-speed operation on a Tier 4 level off-road heavy-duty diesel engine. In a typical off-road duty cycle, such as Non-Road Transient Cycle (NRTC), about 82.5% of cycle’s energy is produced in the engine speed range of 1750–2200 rpm, prompting investigation into the impact of CDA during high-speed operations. CDA results in airflow reductions and increased exhaust gas temperatures due to lower air–fuel ratio (AFR). The reduced airflow operation minimizes pumping work, allowing for higher open cycle efficiency, and thereby translating into lower fuel consumption. The study reveals a new finding: fuel benefits from CDA extend over a larger load range (up to 8.3 bar BMEP) during high-speed operation in off-road heavy-duty engines compared to findings in on-road heavy-duty engines. This phenomenon can be attributed to sufficient oxygen inducted during CDA operation, resulting from similar turbocharger speeds compared to all-cylinder firing operation, especially at high-loads, thereby maintaining particulate matter (PM) concentration within prescribed constraints. Steady-state test results demonstrate a reduction in fuel consumption from 33.7% at 0.4 bar to 1.4% at 8.3 bar BMEP, at 2100 rpm engine speed.

Diesel Engine Turbocharger Monitoring by Processing Accelerometric Signals through Empirical Mode Decomposition and Independent Component Analysis

In this study, a method for the monitoring of internal combustion engine operation by vibration signals is proposed. The work falls within the context of the increasingly stringent standards relating to the environmental impact of engines and the development of monitoring and control techniques to ensure increased engine performance as well as fuel saving and reduction of pollutant emissions. Experimentation was performed on a turbocharged light-duty compression ignition direct-injection engine. Two monoaxial accelerometers were installed on the engine compressor case, the speed of which has been demonstrated to be closely related to the engine operation. Vibration measurements of the engine compressor case have been processed by combining the Empirical Mode Decomposition technique with Independent Component Analysis and Short Time Fourier Transform to indirectly estimate the turbocharger speed. The obtained traces have been compared to the direct turbocharger velocity measures during the stationary running of the engine (speed and load conditions varied in the complete engine’s range of operation). The results point out the potentiality of the methodology in algorithms devoted to identifying modifications of the combustion development regarding regular operation via indirect turbocharger speed monitoring.

Applicability of Variable-Geometry Turbocharger for Diesel Generators under High Exhaust Back Pressure

The exhaust back pressure of diesel engines is becoming increasingly higher nowadays. In order to keep discharging exhaust unhindered and operating smoothly under high exhaust back pressure, a large reduction in engine maximum brake output is often observed, as well as increased fuel consumption and lower combustion efficiency with heavy exhaust smokes. In our previous study, “Applicability of Reducing Valve Timing Overlap for Diesel Engines under High Exhaust Back Pressure”, a reduced valve timing overlap of 12 °CA partially improves the brake output and BSFC for a fixed-geometry turbocharged diesel engine under high exhaust back pressures. A potential solution for restoring the brake output under high exhaust back pressures could be the use of variable-geometry turbochargers. In this study, a variable-geometry turbocharger is applied to a diesel engine to study the engine performance characteristics and applicability, especially the further improvement of brake output and the brake-specific fuel consumption of the engine. Continuing with the results of our previous research, a basic setting of 12 °CA for the valve timing overlap is set up for the subsequent engine performance simulations in this study (using GT-Power SW). Via simulation, exhaust back pressures of 25 kPa, 45 kPa, and 65 kPa gauge are studied for a turbocharged diesel engine. The results for the engine parameters, including brake output, brake-specific fuel consumption, compressor outlet temperature, turbine inlet temperature, intake air mass flow rate, and exhaust mass flow rate are analyzed. The results of the variable-geometry turbocharger, including turbocharger speed, pressure ratios and efficiencies of compressor and turbine are also analyzed. The results indicate that the brake output and brake-specific fuel consumption are effectively improved under full-load operation with an adequate variable-geometry turbocharger rack position. Operable ranges of rack position are also set up for different back pressures.

Turbocharger surge behavior for sudden valve closing downstream the compressor and effect of actuating variable nozzle turbine

Surge is an unstable phenomenon appearing when a valve closing reduces the compressor flow rate. This phenomenon is avoided for automotive turbochargers by defining a surge margin during powertrain system design. This surge margin established with measurements in steady state testing regime limits the maximal engine torque at low levels of output. An active control of the compressor could reduce the surge margin and facilitate a transient compressor operation for a short time in surge zone. In this paper, an experimental study of the transient operation of a turbocharger compressor entering the surge zone is performed. Control of the turbocharger speed is sought to avoid unsteady operation using the variable geometry turbine (VGT) nozzle actuator. From a given stable operating point, surge is induced by reducing the opening of a valve located downstream of the compressor air circuit. The effect of reducing the speed of rotation by controlling the VGT valve is investigated, as this should lead to more stable compressor operation. The rotation speed of the turbocharger is controlled to avoid an unstable operating point using servo-actuator of variable geometry turbine. From a stable operating point, the surge appearance is caused by closing a butterfly valve downstream the air circuit of the compressor. The effect on the compressor rotation speed when the opening of variable geometry turbocharger valve is modified is studied. Measurements have been conducted for different control profiles of the VGT valve placed downstream the compressor. This article presents the means used to carry out these tests as well as the results of the measurements of the instantaneous signals of pressure, temperature, flow rate and rotation speed, allowing the analysis of the surge phenomenon.

Experimental assessment of the rotor outlet flow in a twin-entry radial turbine by means of Laser Doppler Anemometry

The current paper presents the validation of some hypotheses used for developing a one-dimensional twin-entry turbine model with experimental measurements. A Laser Doppler Anemometry (LDA) technique has been used for measuring the axial Mach number and for counting the number of particles downstream of the rotor outlet. These measurements have been done for different mass flow ratio (MFR) and reduced turbocharger speed conditions. The flow coming from each turbine entry does not fully mix with the other within the rotor since, downstream of the rotor, they can still be differentiated. Thus, the hypothesis of studying twin-entry turbines as two separated single-entry turbines in one-dimensional models is corroborated. Moreover, the rotor outlet area corresponding to each flow branch has linear trends with the MFR value. Therefore, the rotor outlet effective area used for one-dimensional models should vary linearly with the MFR value.

Acoustic Method for Estimation of Marine Low-Speed Engine Turbocharger Parameters

The article presents the acoustic method of marine low-speed engine turbocharger parameter estimation under operating conditions when a prompt assessment of instantaneous turbocharger speed and rotor vibration level is required. The method lies in the analysis of the acoustic signal that is generated by the compressor of the turbocharger with the diesel engine running under load. The spectral analysis reveals that the compressor blades generate acoustic oscillations that are always present in the overall acoustic spectrum of the turbocharger regardless of its technical condition. The harmonic components corresponding to the blades can be detected in the spectrum using the limit method. The calculated instantaneous turbocharger speed makes it possible to analyze the main harmonic amplitude in the spectrum. The method presented in this paper helps eliminate discrete Fourier transform (DFT) spectral leakage so that the amplitude of the main harmonic can be estimated. Further analysis of the amplitude of the main harmonic allows for efficient estimation of the turbocharger rotor vibration level when in operation. The method can be practically applied by means of a smartphone or a computer that has the dedicated software installed. The proposed method lays the foundations for a permanent monitoring system of turbocharger speed and vibration in industrial and marine diesel engines.

EFFECT OF THERMAL INERTIA ON DIESEL ENGINES TRANSIENT PERFORMANCE

Transient operation of turbocharged diesel engines is affected by the thermal inertia of the cylinder parts, intake and exhaust manifolds. Because of thermal inertia the temperature of engine parts at steady operation fluctuates during the operating cycle near their average values in a relatively small range, but during transient operation it takes some time to warm or cool the engine parts. Thermal inertia is expressed in changes in fuel combustion, in-cylinder heat transfer and indicated efficiency of the cycle, and increase of general inertia of gas-turbine supercharging system, which determines the necessity to take into account this phenomenon when modeling unsteady engine operation. The conductance-capacitance model was proposed for online internal combustion engines operating cycle simulation tool Blitz-PRO to consider thermal inertia during engine’s transient process. The idea is to consider the heat capacity of engine parts during the heat transfer process, so they accumulate energy at warming and release it at cooling. Combined with equations of heat transfer and thermal conductivity it enables to calculate the change in the average temperatures during engine transient and consider the changes in the overall heat transfer process. The proposed method was tested by comparing the experimental data, obtained from the dyno test-bench based on modified KamAZ-740.10 diesel engine, and the results of modeling in Blitz-PRO. During the experiment, the instantaneous brake torque of the engine, crankshaft and turbocharger speed, supercharged air pressure and the pressure at the turbine’s inlet as well as the intake air mass flow were automatically measured during engine running. Calculations were executed for two setups: with the thermal inertia consideration and without it. As a result, it was found that the most influenced by thermal inertia is the supercharging system: by the 8th second of transient process the calculated supercharged air pressure without thermal inertia consideration is 19% greater, comparing to experimental data. The turbocharger’s rotor speed, intake air flow are influenced greatly too. Suggested method of thermal inertia assessment helps to provide much more accurate simulation of engine transient operation, especially in terms of turbocharging system behavior as it is shown.

Experimental Study on the Combustion Monitoring via the Turbocharger Speed Fluctuations by Vibration Measurement

Experimental Study on the Combustion Monitoring via the Turbocharger Speed Fluctuations by Vibration Measurement

A semi-analytical method applied to turbocharger engine model

In this study, we apply a new version of the Homotopy Analysis Method called decomposition of the homotopy analysis method (DHAM). The DHAM method is based on the decomposition of the right-hand side of a given system of differential equations into a sum of functions. After the decomposition one can apply the HAM method. The physical model that we investigate in this paper is a complex system of equations that contains nonlinear ordinary differential equations of the first order. The system of equations takes into account the important variables such as the pressure, the temperature, the mass flow, the torque due to the turbine turbocharger, the torque from the compressor, the speed of turbocharger, etc. This system is very complex and cannot be solved analytically. The HAM method includes an artificial small parameter that inserts into the physical model and hence it enables one to apply different asymptotic methods. We compared the results of DHAM and HAM to numerical simulations analyses. We concluded that the DHAM results are closer to the numerical simulation results.

An Internal Model Control-Based Approach for Characterization and Controller Tuning of Turbocharged Gasoline Engines

This brief develops a method for system characterization and controller tuning for the boost control system of automotive turbocharged gasoline engines. The method utilizes the relay feedback technique for system characterization, followed by the internal model control (IMC) technique for controller tuning. The novelty is that instead of a high fidelity plant model, an ultrasimplified gain-integrator-delay model is employed in the IMC controller. As we show, our method leads to a time-efficient calibration process, assigns a desired closed-loop bandwidth exactly , and leads to good stability margins. A detailed and thorough analysis of the method, including its fundamental limitations, is provided. The method is experimentally applied to the boost control system of a turbocharged gasoline engine, where it is shown that the controller gains can be reliably computed at various engine operating points. The method identifies turbocharger speed as the best scheduling parameter for the controller gains, and the resulting controller is experimentally shown to yield good tracking performance.

Design and testing a bespoke cylinder head pulsating flow generator for a turbocharger gas stand

Most turbocharger gas stands are designed to map performance under steady flow conditions. However, when connected to an internal combustion engine (ICE), the turbine is exposed to pulsatile flow. In order to enable a full analysis of the unsteady flow and turbocharger performance, it is crucial to quantify unsteady flow effects in the gas stand tests.This paper presents the development and use of bespoke experimental hardware that aims to generate flows in a gas-stand with characteristics similar to that produced by an ICE. This is achieved using a specially modified cylinder head placed between the hot supply and the turbocharger. The device has been designed, manufactured and tested on the gas stand showing its usefulness to study the energy exchange between the engine and the turbine.Testing a turbocharger where a cylinder is deactivated showed large changes in the instantaneous turbocharger speed, pressure and temperature profiles. These unsteady characteristics resulted in a change in the turbocharger behaviour. The insights into unsteady characteristics is expected to contribute to both engine calibration and turbocharger design. It also demonstrates the novelty of the approach in delivering a means to replicate hot, engine-like flow unsteadiness and thereby a wider, more representative data set.

Computational technique for turbocharger transient characterization using real driving conditions data

The use of turbochargers is linked to strategies such as engine downsizing or downspeeding, once the use of this device compensates performance losses observed with the reduction of the displaced volume by compressing the air to be admitted. Steady-state tests of turbochargers are common in literature although not consistent with real behavior associated with a vehicular transient operation. To approximate the experimental tests using gas standard test benches to these real conditions, this paper aims to identify transient behavior of a turbocharger in a vehicular application. Experimental data is collected in two tests: steady-state on a dynamometer and transient on a real highway cycle. Added to the experimental tests, a computational one-dimensional model is developed. The steady-state engine data is used in the model inputs and results of a real transient cycle simulation are validated with the experimental transient data. A standard driving cycle is used to analyze the turbocharger speed behavior when both gear shifting strategy and vehicle load are changed. The computational method presented errors below 5% for the engine and turbocharger speeds, resulting in a powerful tool to perform experimental test profiles and to evaluate operational turbocharger parameters.

Strategy on performance improvement of inverse Brayton cycle system for energy recovery in turbocharged diesel engines

The inverse Brayton cycle is a potential technology for waste heat energy recovery. It consists of three components: one turbine, one heat exchanger, and one compressor. The exhaust gas is further expanded to subatmospheric pressure in the turbine, and then cooled in the heat exchanger, last compressed in the compressor into the atmosphere. The process above is the reverse of the pressurized Brayton cycle. This work has presented the strategy on performance improvement of the inverse Brayton cycle system for energy recovery in turbocharged diesel engines, which has pointed the way to the future development of the inverse Brayton cycle system. In the paper, an experiment was presented to validate the numerical model of a 2.0 l turbocharged diesel engine. Meanwhile, the influence laws of the inverse Brayton cycle system critical parameters, including turbocharger speed and efficiencies, and heat exchanger efficiency, on the system performance improvement for energy recovery are explored at various engine operations. The results have shown that the engine exhaust energy recovery efficiency increases with the engine speed up, and it has a maximum increment of 6.1% at the engine speed of 4000 r/min (the engine rated power point) and the full load. At the moment, the absolute pressure was before final compression is 51.9 kPa. For the inverse Brayton cycle system development in the future, it is essential to choose a more effective heat exchanger. Moreover, variable geometry turbines are very appropriate to achieve a proper matching between the turbocharging system and the inverse Brayton cycle system.

Innovative Control Strategies for the Diagnosis of Injector Performance in an Internal Combustion Engine via Turbocharger Speed

In order to ensure a high level of performance and to comply with the increasingly severe limitations in terms of fuel consumption and pollution emissions, modern diesel engines need continuous monitoring of their operating conditions by their control units. With particular focus on turbocharged engines, which are presently the standard in a large number of applications, the use of the average and the instantaneous turbocharger speeds is thought to represent a valuable feedback of the engine behavior, especially for the identification of the cylinder-to-cylinder injection variations. The correct operation of the injectors and control of the injected fuel quantity allow the controller to ensure the right combustion process and maintain engine performance. In the present study, two different techniques are presented to fit this scope. The techniques are discussed and experimentally validated, leading to the definition of an integrated control strategy, which features the main benefits of the two, and is able to correctly detect the cylinder-to-cylinder injection variation and, consequently, properly correct the injection in each cylinder in order to balance the engine behavior. In addition, the possibility of detecting misfiring events was assessed.

Comparison study between two types of nozzles for a turbocharger balancing machine using ANSYS software

Turbocharger balancing machines require a specific tooling for spinning the center housing rotating assembly, in order to balance it dynamically. The tooling requires a nozzle to guide the air to the blades of the turbine wheel in order to spin it. Depending on the type of nozzle chosen, the maximum rotational speed achieved and the acceleration curve can be different. In today?s market there is anincreasing demand for a higher turbocharger speed, generally driven by the demand for engine downsizing and for a higher performance. Due to that, turbochargers need to be better balanced, thus requiring a wider measurement range of the unbalanced in order to see how the part performs in all its working range. Consequently, the nozzles used by turbocharger balancing machines need to be verified at a higher speed limit.

Modeling and Control of a Diesel Engine With Regenerative Hydraulic-Assisted Turbocharger

Diesel engines are of great challenges due to stringent emission and fuel economy requirements. Compared with the conventional turbocharger system, regenerative assisted system provides additional degrees-of-freedom for turbocharger speed control. Hence, it significantly improves control capability for exhaust-gas-recirculation (EGR) and boost pressure. This paper focuses on modeling and control of a diesel engine air-path system equipped with an EGR subsystem and a variable geometry turbocharger (VGT) coupled with a regenerative hydraulic-assisted turbocharger (RHAT). The challenges lie in the inherent coupling among EGR, turbocharger performance, and high nonlinearity of the engine air-path system. A control-oriented nonlinear RHAT system model is developed; and a linear quadratic (LQ) control design approach is proposed in this paper to regulate the EGR mass flow rate and boost pressure simultaneously and the resulting closed-loop system performance can be tuned by properly selecting the LQ control weighting matrices. Multiple LQ controllers with integral action are designed based on the linearized system models over a gridded engine operational map and the final gain-scheduling controller for a given engine operational condition is obtained by interpreting the neighboring LQ controllers. The gain-scheduling LQ controllers for both traditional VGT-EGR and VGT-EGR-RHAT systems are compared with the in-house baseline controller, consisting of two single-input and single-output (SISO) controllers, against the nonlinear plant. The simulation results show that the designed multi-input and multi-output LQ gain-scheduling controller is able to manage the performance trade-offs between EGR mass flow and boost pressure tracking. With the additional assisted and regenerative power available on the turbocharger shaft for the RHAT system, engine transient boost pressure performance can be significantly improved without compromising the EGR tracking performance, compared with the baseline control.

Impact of the Engine Tuning on its Technical Condition Assessment Based on Limited Number of Available Parameters

Abstract Due to the limited scope of the diagnostic equipment on the ship, the technical condition of the engine is based on the measurement of pressure and temperature at the available measuring points. Usually it is the exhaust temperature at the outlet of individual cylinders, supercharging pressure, oil temperature and cooling water temperature. Sometimes the bearing temperature and turbocharger speed are also measured. Normally, if the engine is adapted to this, the maximum combustion pressure is measured periodically although distorted through the channels with the indicator valves. The paper presents examples of the exploitation of marine diesel engines, where there is a discrepancy between the actual technical state of the engine and the technical state of the engine based on the traditional diagnostic method based on a limited set of available parameters. These discrepancies resulted, inter alia, from the regular fuel injection timing and fuel dose adjustment, so that the measured parameters were adequate to the actual load of the engine. This adjustment is justified, but leads to masking engine components wear symptoms. In this situation, it can only be stated that the state of the fuel injection equipment is suitable for the current technical state of the some engine components and does not provide a sufficient basis for the extension of the repair interval.

In-Vehicle Realization of Nonlinear MPC for Gasoline Two-Stage Turbocharging Airpath Control

Innovative charging concepts, such as two-stage turbocharging for gasoline engines, cause high demands on the process control. The open-loop process is characterized by a complex, nonlinear system behavior. In addition, the requirements on the closed-loop system are challenging: fast reference tracking has to be achieved without overshoots while respecting constraints on the turbocharger speeds in order to prevent damaging of the components. Nonlinear model predictive control (NMPC) offers a high potential for this purpose. It is capable of handling coupled multiple-input systems while achieving high control quality and respecting constraints on system states. This paper presents an NMPC scheme for a two-stage turbocharged gasoline airpath, which is based on a physically driven reduced-order model formulated as a set of differential-algebraic equations. The online optimal control algorithm uses the real-time iteration scheme and is implemented on a control prototyping platform. For validation of the algorithm, it is tested based on simulations and vehicle experiments. These experiments have been conducted on a vehicle dynamometer as well as on an automotive testing track. For this purpose, a modified production vehicle is used in which the airpath concept is implemented.

The methodology for determining of the energy costs for the probabilistic nature of the load of a machine-tractor unit

The random nature of the load is the main cause of deterioration of energy parameters and technical and economic indicators of machine-tractor units (MTU). Oscillations of the load lead to an increase in energy costs for technological processes. Direct fuel and energy costs should be determined and predicted with a high degree of reliability, taking into account the specifics of the work of the MTU and the dynamics of its performance of technological processes. The identification and optimization of energy costs of the MTU will ensure an increase in the efficiency of the technological processes and technologies of cultivation in crop production. The subject of the study is the development of mathematical models for determining and optimizing the direct energy costs of MTU equipped with advanced gas turbine engine (GTE) engines. The purpose of the research is to develop a methodology for determining the direct fuel and energy costs of MTU, taking into account the probabilistic nature of the load. The novelty of the research consists in the developed mathematical models and calculation algorithm, as well as optimization of the direct fuel and energy costs of MTU with GTE. The proposed methodology is developed on the basis of a systematic approach, generalization, and analysis of experimental data, mathematical modeling of processes. Experimental studies were carried out in laboratory facilities and in the field using modern measuring instruments and recording experimental data. The proposed methodology allows, with a probability of 0,90-0,95, to predict the optimal values of the direct fuel and energy costs of the MTU with GTE. As an example, the article gives examples of calculation and optimization of direct fuel and energy costs of plowing unit consisting of a Kirovets tractor with a GTD-350T gas turbine engine and a PNI-8/9-40 plow at various levels of turbocharger speed. It is established that at the 100 % level of the turbo compressor speed and the variation of the load variation coefficient from 0 to 0,333, the optimal values of the direct fuel and energy costs of the plowing unit increase from 543,0 to 723,12 MJ/ha. The same trend of increasing the direct fuel and energy costs of MTU is also observed in other levels of implementation of the turbo GTE turbocharger speed. It should be noted that with a decrease in the level of implementation of the turbocharger GTE's speed, direct fuel, and energy costs are increasing. The proposed methodology allows to determine and optimize the values of direct fuel and energy costs of MTU with GTE taking into account the probabilistic nature of the load under the specific conditions of their operation.

Vibration analysis to estimate turbocharger speed fluctuation in diesel engines

The optimum management of the engine system has a crucial role in order to achieve high efficiency and reduced pollutant emissions. Advanced methods have been proposed, in which several types of sensors are used to directly/indirectly sense the combustion and to provide a feedback signal to optimize the engine management.In turbocharged engines, it has been demonstrated that a relationship exists between the rotational speed of the turbocharger and the thermo-fluid dynamic condition of the gases at the exhaust valve opening. Such a relation allows to establish a link between the engine operating conditions in terms of speed, load and injection settings and the turbocharger speed.A research activity was performed aimed at developing a methodology in which the signal from an accelerometer mounted on the compressor housing was used to extract information about the turbocharger speed value. The activity was organized in two subsequent steps, each one focused on one specific objective:– estimation of the mean turbocharger rotational speed– evaluation of the turbocharger speed fluctuations.Tests were performed on a small displacement two-cylinder diesel engine mainly used in urban vehicles that was equipped with a turbocharger. The results obtained during the first step of activity demonstrated the opportunity of further investigations in order to compute the turbocharger speed fluctuation from the accelerometer signal processing. This paper is devoted to present the results of the second step of the research activity, with the final aim of realizing a non intrusive control of combustion process, in which the variation of combustion development as regards nominal condition is detected via the estimation of the turbocharger speed.