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Components in ducts systems that create flow separation can for certain conditions and frequencies amplify incident sound waves. This vortex-sound phenomena is the origin for whistling, i.e., the production of tonal sound at frequencies close to the resonances of a duct system. One way of predicting whistling potential is to compute the acoustic power balance, i.e., the difference between incident and scattered sound power. This can readily be obtained if the scattering matrix is known for the object. For the low frequency plane wave case this implies knowledge of the two-port data, which can be obtained by numerical and experimental methods. In this paper the procedure to experimentally determine whistling potential will be presented and some examples are given to show how this procedure can be used in some applications for automotive intake and exhaust system components.

Exhaust noise is a major contributor to the radiated noise level of a vehicle, especially at idle. The radiated noise level has to meet a certain criteria based on regulation and consumer demand. In many cases, the problem appears after the vehicle is manufactured and the tailpipe noise measurement is performed indicating a high noise level that needs to be reduced. This paper describes one of those cases where the radiated noise level of a certain passenger car at idle was required to be reduced by 6 dB(A). The exhaust system consists of one main muffler and one auxiliary muffler. A 1D two-port model of the exhaust system including the two mufflers was built using commercial software. This model was validated against the measurement of the two-port matrix of both mufflers. The model was then used together with tailpipe noise measurements to estimate the characteristics of the source strength and impedance.

Improving turbocharger performance to increase engine efficiency has the potential to help meet current and upcoming exhaust legislation. One limiting factor is compressor surge, an air flow instability phenomenon capable of causing severe vibration and noise. To avoid surge, the turbocharger is operated with a safety margin (surge margin) which, as well as avoiding surge in steady state operation, unfortunately also lowers engine performance. This paper investigates the possibility of detecting compressor surge with a conventional engine knock sensor. It further recommends a surge detection algorithm based on their signals during transient engine operation. Three knock sensors were mounted on the turbocharger and placed along the axes of three dimensions of movement. The engine was operated in load steps starting from steady state. The steady state points of operation covered the vital parts of the engine speed and load range.

As vehicles become electrified and more intelligent in terms of sensing, actuation and processing; a number of interesting possibilities arise in controlling vehicle dynamics and driving behavior. Over-actuation with in- wheel motors, all wheel steering and active camber is one such possibility, which facilitate the control strategies that push boundaries in energy consumption and safety. Optimal control can be used to investigate the best combinations of control inputs to an over-actuated system. This paper shows how an optimal control problem can be formulated and solved for an over-actuated vehicle case, and highlights the translation of this optimal solution to a real-world scenario, enabling intelligent means to improve vehicle efficiency. This paper gives an insight into Dynamic Programming (DP) as an offline optimal control method that guarantees the global optimum.

The global demand for decreased emission from engines and increased efficiency drives manufactures to develop more advanced fuel injection systems. Today's compression-ignited engines use common rail systems with high injection pressures and fuel injector nozzles with small orifice diameters. These systems are highly sensitive to small changes in orifice diameters since these could lead to deteriorations in spray characteristics, thus reducing engine performance and increasing emissions. Phenomena that could create problems include nozzle fouling caused by metal carboxylates or biofuels. The problems increase with extended use of biofuels. This paper reports on an experimental study of nozzle hole fouling performed on a single-cylinder engine. The aim was to identify if the solubility of the fuel has an effect on deposit build-up and, thus, the reduction in fuelling with associated torque loss, and if there is a probability of regenerating the contaminated injectors.

In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio.

A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow.

The compressor surge line of automotive turbochargers can limit the low-end torque of an engine. In order to determine how close the compressor operates to its surge limit, the Hurst exponent of the pressure signal has recently been proposed as a criterion. The Hurst exponent quantifies the fractal properties of a time series and its long-term memory. This paper evaluates the outcome of applying Hurst exponent based criterion on time-resolved pressure signals, measured simultaneously at different locations in the compression system. Experiments were performed using a truck-sized turbocharger on a cold gas stand at the University of Cincinnati. The pressure sensors were flush-mounted at different circumferential positions at the inlet of the compressor, in the diffuser and volute, as well as downstream of the compressor.

Turbochargers are commonly used in automotive engines to increase the internal combustion engine performance during off design operation conditions. When used, a most wide operation range for the turbocharger is desired, which is limited on the compressor side by the choke condition and the surge phenomenon. The ported shroud technology is used to extend the operable working range of the compressor, which permits flow disturbances that block the blade passage to escape and stream back through the shroud cavity to the compressor inlet. The impact of this technology on a speed-line at near optimal operation condition and near surge operation condition is investigated. A numerical study investigating the flow-field in a centrifugal compressor of an automotive turbocharger has been performed using Large Eddy Simulation. The wheel rotation is handled by the numerically expensive sliding mesh technique. In this analysis, the full compressor geometry (360 deg) is considered.

Typically the combustion in a direct injected compression ignited internal combustion engine is open-loop controlled. The introduction of a cylinder pressure sensor opens up the possibility of a virtual combustion sensor which could enable closed-loop combustion control and thus the potential to counteract effects such as engine part to part variation, component ageing and fuel quality diversity. Closed-loop combustion control requires precise, robust and preferably cheap sensors. This paper presents a virtual cylinder pressure sensor based on the signal from the inexpensive but well proven knock sensor. The method used to convert the knock sensor signal into a pressure estimate included the stages: Phase correcting the raw signal, Filtering the raw signal, Scaling the signal to known thermodynamic laws and provided engine sensors signals and Reconstructing parts of the signal with other known models and assumptions.

A method developed in SAE 2019-01-0058 to correct for deviations from quasi-steady exhaust valve flow is implemented on a single-cylinder GT-Power model and the effects on pumping work and blowdown pulse characteristics are investigated. The valve flow area is always reduced compared to the reference quasi-steady case. It decreases with higher pressure ratios over the valve and increases with higher engines speeds. The reduced flow area increases pumping work with load and engine speed, though primarily with engine speed. The magnitude of the blowdown pulse is reduced and the peak is shifted to a later crank angle.

The paper gives an overview of techniques used for characterization of IC-engines as acoustic sources of exhaust and intake system noise. Some recent advances regarding nonlinear source models are introduced and discussed. To calculate insertion loss of mufflers or the level of radiated sound information about the engine as an acoustic source is needed. The source model used in the low frequency plane wave range is often the linear time invariant one-port model. The acoustic source data is obtained from experimental tests or from 1-D CFD codes describing the engine gas exchange process. The IC-engine is a high level acoustic source and in most cases not completely linear. It is therefore of interest to have models taking weak non-linearity into account while still maintaining a simple method for interfacing the source model with a linear frequency domain model for the attached exhaust or intake system.

Diesel engine manufacturers strive towards further efficiency improvements. Thus, reducing in-cylinder heat losses is becoming increasingly important. Understanding how location, thermal insulation, and engine operating conditions affect the heat transfer to the combustion chamber walls is fundamental for the future reduction of in-cylinder heat losses. This study investigates the effect of a 1mm-thick plasma-sprayed yttria-stabilized zirconia (YSZ) coating on a piston. Such a coated piston and a similar steel piston are compared to each other based on experimental data for the heat release, the heat transfer rate to the oil in the piston cooling gallery, the local instantaneous surface temperature, and the local instantaneous surface heat flux. The surface temperature was measured for different crank angle positions using phosphor thermometry.

In an ever-transforming sector such as that of private road transport, major changes in the propulsion systems entail a change in the perception of the noise sources and the annoyance they cause. As compared to the scenario encountered in vehicles equipped with an internal combustion engine (ICE), in electrically propelled vehicles the heating, ventilation, and air conditioning (HVAC) system represents a more prominent source of noise affecting a car’s passenger cabin. By virtue of the quick turnaround, steady state Reynolds-averaged Navier Stokes (RANS)- based noise source models are a handy tool to predict the acoustic power generated by passenger car HVAC blowers. The study shows that the most eminent noise source type is the dipole source associated with fluctuating pressures on solid surfaces.

Noise generated by low Mach number flow in duct networks is important in many industrial applications. In the automotive industry the two most important are the ventilation duct network and the engine exhaust system. Traditionally, design is made based on rule-of thumb or slightly better by simple semi-empirical scaling laws for flow noise. In many cases, strong curvatures and local deviations from circular cross-sections are created due to outer geometry restrictions. This can result in local relatively high flow velocities and complex flow separation patterns and as a result, rule-of thumb and scaling law methods can become highly inaccurate and uncertain. More advanced techniques based on time domain modelling of the fluid dynamics equations together with acoustic analogies can offer a better understanding of the local noise generation, the propagation and interaction with the rest of the system.

Piston cooling galleries are critical for the pistons’ capability to handle increasing power density while maintaining the same level of durability. However, piston cooling also accounts for a considerable amount of heat rejection and parasitic losses. Knowing the distribution of the heat transfer coefficient (HTC) inside the cooling gallery could enable new designs which ensure effective cooling of areas decisive for durability while minimizing parasitic losses and overall heat rejection. In this study, an inverse heat transfer method is presented to determine the spatial HTC distribution inside the cooling gallery based on surface temperature measurements with an infrared (IR) camera. The method utilizes a piston specially machined so it only has a thin sheet of material of a known thickness left between the cooling gallery and the piston bowl. The piston - initially at room temperature - is heated up with warm oil injected into the cooling gallery.

Cremer impedance, first proposed by Cremer (Acustica 3, 1953) and then improved by Tester (JSV 28, 1973), refers to the locally reacting boundary condition that can maximize the attenuation of a certain acoustic mode in a uniform waveguide. One limitation in Tester’s work is that it simplified the analysis on the effect of flow by only considering high frequencies or the ‘well cut-on’ modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest, with the vehicle intake and exhaust system included. A recent modification done by Kabral et al. (Acta Acustica united with Acustica 102, 2016) has removed this limitation and investigated the ‘exact’ solution of Cremer impedance for circular waveguides, which reveals an appreciable difference between the exact and classic solution in the low frequency range. Consequently, the exact solution can lead to a much higher low-frequency attenuation level.

Modern spark-ignited (SI) engines offer excellent emission reduction when operated with a stoichiometric mixture and a three-way catalytic converter. A challenge with stoichiometric compared to diluted operation is the knock propensity due to the high reactivity of the mixture. This limits the compression ratio, thus reducing engine efficiency and increasing exhaust temperature. The current work evaluated a model of conditions at inlet valve closing (IVC) and top dead center (TDC) for steady state operation. The IVC temperature model is achieved by a cycle-to-cycle resolved residual gas fraction estimator. Due to the potential charge cooling effect from methanol, a method was proposed to determine the fraction of fuel sourced from a wall film. Determining the level of charge cooling is important as it heavily impacts the IVC and TDC temperatures.

The use of turbochargers with downsized internal combustion engines improves road vehicles’ energy efficiency but introduces additional sound sources of strong acoustic annoyance on the turbocharger’s compressor side. In the present study, direct noise computations (DNC) are carried out on a passenger vehicle turbocharger compressor. The work focuses on assessing the influence of grid parameters on the acoustic predictions, to further advance the maturity of the acoustic modelling of such machines with complex three-dimensional features. The effect of the boundary layer mesh structure, and of the spatial resolution of the mesh, on the simulated acoustic signatures is investigated on detached eddy simulations (DES). Refinements in the core mesh are applied in areas of major acoustic production, to generate cells with sizes proportional to the local Taylor microscale values.

To conduct system level studies on internal combustion engines reduced order models are required in order to keep the computational load below reasonable limits. By its nature a reduced order model is a simplification of reality and may introduce modeling errors. However what is of interest is the size of the error and if it is possible to reduce the error by some method. A popular system level study is gas exchange and in this paper the focus is on the exhaust valve. Generally the valve is modeled as an ideal nozzle where the flow losses are captured by reducing the flow area. As the valve moves slowly compared to the flow the process is assumed to be quasi-steady, i.e. interpolation between steady-flow measurements can be used to describe the dynamic process during valve opening. These measurements are generally done at low pressure drops, as the influence of pressure ratio is assumed to be negligible.