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Technical Paper

Turbocharger Performance Prediction: A Review of Map Modelling

Supercharging has been increasingly more employed as an approach to improve the internal combustion engine (ICE) thermal efficiency. The turbocharger (TC) stands out as a well-established technology which recovers waste energy from exhaust gases to increase the ICE intake pressure and mass flow rate. Nevertheless, the increasingly stringent restrictions on greenhouse gases emission, concomitantly with performance improvement required from customers, impose a tighter pairing between TC and ICE and higher control of TC operational conditions. Matching a proper TC for a given ICE has a major importance for the global efficiency, having direct impact on specific consumption, emission levels and drivability. This process is typically performed using computational simulations via interpolations of TC tabular performance maps, which details the flow status for given shaft speed and mass flow rate.
Technical Paper

Improving Brake Thermal Efficiency Using High-Efficiency Turbo and EGR Pump While Meeting 2027 Emissions

Commercial vehicles are moving in the direction of improving brake thermal efficiency while also meeting future diesel emission requirements. This study is focused on improving efficiency by replacing the variable geometry turbine (VGT) turbocharger with a high-efficiency fixed geometry turbocharger. Engine-out (EO) NOX emissions are maintained by providing the required amount of exhaust gas recirculation (EGR) using a 48 V motor driven EGR pump downstream of the EGR cooler. This engine is also equipped with cylinder deactivation (CDA) hardware such that the engine can be optimized at low load operation using the combination of the high-efficiency turbocharger, EGR pump and CDA. The exhaust aftertreatment system has been shown to meet 2027 emissions using the baseline engine hardware as it includes a close coupled light-off SCR followed by a downstream SCR system.
Journal Article

Mathematics of Turbomachinery: Centrifugal Impeller

Abstract The mathematics required to design and analyze turbomachinery were gathered from many sources and presented in its entirety as a single source, step-by-step procedure. An impeller was then designed and analyzed. A one-dimensional (1D) model explains the mathematics for performance in detail. The 1D model lacked the ability to predict flow-related phenomena such as flow surge but highlighted the direct connection between blade angle and rotation direction with pressure rise and efficiency. For the present study, positive blade angles pointing in the direction of rotation (clockwise in the present study) provided higher pressure rise and higher losses. Negative blade angles pointing in the opposite direction of rotation (counterclockwise in the present study) resulted in lower pressure rise and lower losses. Flow surge was studied with a three-dimensional (3D) model.
Journal Article

Comparison of Cold Start Calibrations, Vehicle Hardware and Catalyst Architecture of 4-Cylinder Turbocharged Vehicles

Higher fuel costs and lower greenhouse gas standards, especially CO2, have compelled vehicle manufacturers to downsize engines while simultaneously using turbochargers on more of their applications. The application of turbochargers improves fuel economy as well as torque and power. However, this also results in lower exhaust temperatures which can challenge the ability of three-way catalysts to achieve low emission levels. This work investigates and compares the catalyst heat-up strategies, hardware, and catalyst architecture of four turbocharged 4-cylinder vehicles: a 2010 VW 2.0L DI, a 2013 Chevy Malibu 2.0L DI, a 2013 Ford Fusion 1.6L DI, and a 2013 Dodge Dart 1.4L Multi-Air. In addition, three emission studies are presented. One study will show a strategy to reduce PGM concentrations in a close-coupled (CC) catalyst.
Journal Article

Analysis of Transient Operation of Turbo Charged Engines

Transient operation of turbocharged engines is mostly optimised in the light of quickness of response and the provision of the demanded torque. The time from demanded boosted torque to delivered torque above the maximum torque provided by the natural aspirated torque value is known as turbo-lag. This could reveal as an issue for small gasoline turbo-charged engines with a displacement of 1.0ltr or lower. These small types of engines are moving more and more in the focus for automobile applications. To provide the required power and torque, gasoline direct injection and turbo-charging are helpful in order to enable a reduction of fuel consumption by both de-throttled operation over a large area of operation and improved thermal efficiency among others achieved by maintaining an appropriate compression ratio.
Journal Article

Diesel Cylinder Charge Properties: Feed-Forward Control and Cycle-by-Cycle Analysis Using an In-Cylinder Gas Sampling System

Common-rail fuel injection systems on modern light-duty diesel engines are effectively able to respond instantaneously to changes in the demanded injection quantity. In contrast, the air-system is subject to significantly slower dynamics, primarily due to filling/emptying effects in the manifolds and turbocharger inertia. The behavior of the air-path in a diesel engine is therefore the main limiting factor in terms of engine-out emissions during transient operation. This paper presents a simple mean-value model for the air-path during throttled operation, which is used to design a feed-forward controller that delivers very rapid changes in the in-cylinder charge properties. The feed-forward control action is validated using a state-of-the-art sampling system that allows true cycle-by-cycle measurement of the in-cylinder CO₂ concentration.
Journal Article

Physical-Based Algorithms for Interpolation and Extrapolation of Turbocharger Data Maps

Data maps are easy to put in place and require very low calculation time. As a consequence they are often valued over fully physic-based models. This is particularly true when it is question of turbochargers. However, even if these maps are directly provided by the manufacturer, they usually do not cover the entire engine operating range and are poorly discretized. That's why before implementing them into any model they need to be interpolated and extrapolated. This paper introduces a new interpolation/extrapolation method based on the idea of integrating more physics into the widespread Jensen and Kristensen's method [6]. It essentially relies on the turbo machinery equation analysis performed by Martin during his PhD thesis [9, 10, 11] and the interpolation and extrapolation strategies that he proposed. In most cases the new strategies presented in this paper rely on improvements of the models he proposed.


This SAE Draft Technical Report is intended to document the technical consensus of the current design state of converter/mufflers for heavy-duty emission classification diesel vehicle applications. This will maximize standardization and promote interchangeability of parts from different manufacturers.

Power Cylinder Blow-By: Blow-By Mechanisms

This document covers the mechanisms associated with the power cylinder system which might affect blow-by. It will not discuss in detail the blow-by mechanisms from other systems or engine subsystems.
Technical Paper

NVH Optimization of HMC 3.0L V6 Diesel Engine

Hyundai has developed a brand new 3.0L V6 diesel engine for luxury vehicle with electronic VGT, piezo injector and bedplate block structure. In addition to challenging targets for fuel consumption and emission levels, engine specifications were focused on performance and NVH. This paper presents the detailed process of reinforcing engine components such as block, cylinder head and oil pan in view of low sound pressure and high quality. Generally, the fast reaction speed of piezo injector can improve the emission, but it usually causes injector noise. We reduced this noise through developing new ECU logic and isolating this part with noise reduction foam. In addition to that, we could reduce the combustion noise using DoE method for the optimization of injection parameters considering the emission and fuel economy. As a result of these attempts, 3∼4dBA of overall sound pressure level from engine itself could be reduced without any loss of fuel economy and power characteristics.
Technical Paper

Development of an Automotive Turbocharger Test Stand Using Hot Gas

This work presents the development of an automotive turbocharger test stand where a hot gas generator is used to drive the turbocharger. The burner consists in a tubular combustion chamber, projected to operate burning gaseous fuels. The development of the test stand became necessary within the must to know turbochargers operational characteristics, since those information's are not always supplied by their manufacturers. By using a combustion chamber it's possible to simulate the real operational condition of the set. The test consists in recording the characteristic curves of the turbochargers, known as flow maps or performance maps. The necessary instrumentation is based on virtual instrumentation, where acquisition and control of the sensors are made by computer. In the development of the test stand, a MP-357 Master Power turbocharger, used in commercial heavy trucks, is used.
Technical Paper

High Speed Hydraulic Turbine Driven Supercharger System and Controls Optimization

High speed hydraulic turbine driven superchargers provide a unique option for supercharging naturally aspirated and turbocharged engines. Typical characteristics of the hydro-supercharging system are: compactness, high power level, high efficiency and durability. Hydraulic controls allow for adjustment of turbine speed and power level to match the engine requirements. A typical system utilizes commercially available hydraulic gear pump driving a miniature hydraulic turbine attached to the compressor. Varying the hydraulic flow, allows one to “custom tailor” air flow and boost. When used with a turbodiesel, the hydro-supercharger can produce almost constant engine torque from idle to full speed while increasing the Lambda factor by 50%. A typical 300 to 400 HP modern turbodiesels requires on average 15 HP compressor supercharging power to produce high torque from idle until the turbocharger becomes self sufficient.
Technical Paper

Development of a New Small Passenger Car Turbocharger

Efforts to improve emissions and fuel economy have spawned many opportunities for turbocharging small displacement engines. The focus on efficiency and economy emphasizes the need for low manufacturing costs and selling price as well. To meet these goals, a new small turbocharger was conceived and developed, addressing traditional manufacturing and performance issues accountable for significant portions of production cost. The resulting design features a one-piece bearing system and a significant reduction in parts count compared to conventional designs. Simplified machining and ease of balancing reduce overall cost, while improved rotordynamic characteristics make the design less susceptible to noise during operation.
Technical Paper

Development of Reduction Method for Whirl Noise on Turbocharger

The whirl noise on turbochargers is generated by the self-induced vibration of the oil film in the bearing system. The noise is characterized by its frequency behavior that doesn't increase proportionately to the turbo shaft speed. It tends to be felt annoying. In this paper, to improve the whirl vibration, a statistical analysis approach was applied to the bearing specifications. The results from experiments showed that the bearing clearances played an important role in the reduction of the whirl vibration. To further investigate into this phenomenon, the shaft oscillation behavior was measured. And a vibration simulation program for the turbocharger bearing system was also developed.
Technical Paper

Fuel Economy and Emissions of the Ethanol-Optimized Saab 9-5 Biopower

Saab Automobile recently released the BioPower engines, advertised to use increased turbocharger boost and spark advance on ethanol fuel to enhance performance. Specifications for the 2.0 liter turbocharged engine in the Saab 9-5 Biopower 2.0t report 150 hp (112 kW) on gasoline and a 20% increase to 180 hp (134 kW) on E85 (nominally 85% ethanol, 15% gasoline). While FFVs sold in the U.S. must be emissions certified on Federal Certification Gasoline as well as on E85, the European regulations only require certification on gasoline. Owing to renewed and growing interest in increased ethanol utilization in the U.S., a European-specification 2007 Saab 9-5 Biopower 2.0t was acquired by the Department of Energy and Oak Ridge National Laboratory (ORNL) for benchmark evaluations. Results show that the vehicle's gasoline equivalent fuel economy on the Federal Test Procedure (FTP) and the Highway Fuel Economy Test (HFET) are on par with similar U.S.-legal flex-fuel vehicles.
Technical Paper

Applying Ball Bearings to the Series Turbochargers for the Caterpillar® Heavy-Duty On-Highway Truck Engines

Fuel is a significant portion of the operating cost for an on-highway diesel engine and fuel economy is important to the economics of shipping most goods in North America. Cat® ACERT™ engine technology is no exception. Ball bearings have been applied to the series turbochargers for the Caterpillar heavy-duty, on-highway diesel truck engines in order to reduce mechanical loss for improved efficiency and lower fuel consumption. Over many years of turbocharger development, much effort has been put into improving the aerodynamic efficiency of the compressor and turbine stages. Over the same span of time, the mechanical bearing losses of a turbocharger have not experienced a significant reduction in power consumption. Most turbochargers continue to use conventional hydrodynamic radial and thrust bearings to support the rotor. While these conventional bearings provide a low cost solution, they do create significant mechanical loss.
Technical Paper

Unsteady Behavior in Turbocharger Turbines: Experimental Analysis and Numerical Simulation

The flow in engine turbocharger compressors and turbines is highly unsteady in nature, as it responds to the intake and exhaust manifolds of the internal combustion engine. The optimization of the turbocharger system is therefore a very difficult task, since the devices operate at off-design conditions for most of the engine cycle. Experimental studies allow for improving the understanding on the behavior of the engine components, in particular when tests are performed under real engine operating conditions; however, the experimental tests can be more efficient if they are combined with theoretical simulation tools, which help to select significant engine operating conditions. In this paper, experimental investigations were performed on a flexible component test rig (expressly suited to perform tests on automotive turbochargers) at ICE Laboratory of the University of Genoa (ICEG-DIMSET).
Technical Paper

Diesel Engine Turbocharger Performance Monitoring Using Vibration Analysis

This work will present the use of vibration signal analysis as a tool to extract the physical characteristics of a turbocharger. It will also be shown that through this method it is possible to diagnose faults in a turbocharger. The methodology used consists of comparing the vibration signature of a turbocharger under normal operational conditions against that of the same turbocharger under a simulated fault. To extract the signature, Fourier spectra and envelope spectra of a turbocharger vibration signal were applied directly on the data sets recorded from an accelerometer fixed on the turbocharger. It was observed that there was a distinct difference between the signatures, conclusive evidence to the validity of this work and the effectiveness of the proposed method.