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Technical Paper

Variation in Squish Length and Swirl to Reach Higher Levels of EGR in a CNG Engine

2019-01-15
2019-01-0081
Gaseous methane fuel for internal combustion engines have proved to be a competitive source of propulsion energy for heavy duty truck engines. Using biogas can even reduce the carbon footprint of the truck to near-zero levels, creating fully environmentally friendly transport. Gas engines have already been on the market and proved to be a popular alternative for buses and waste transport. However, for long haulage these gas engines have not been on par with the equivalent diesel engines. To improve the power and efficiency of EURO VI gas engines running stoichiometrically, a direct way forward is adding more boost pressure and spark advance in combination with more EGR to mitigate knock. Using in-cylinder turbulence to achieve higher mixing rate, the fuel can still be combusted efficiently despite the increased fraction of inert gases.
Technical Paper

Turbocharger Speed Estimation via Vibration Analysis

2016-04-05
2016-01-0632
Due to demanding legislation on exhaust emissions for internal combustion engines and increasing fuel prices, automotive manufacturers have focused their efforts on optimizing turbocharging systems. Turbocharger system control optimization is difficult: Unsteady flow conditions combined with not very accurate compressor maps make the real time turbocharger rotational speed one of the most important quantities in the optimization process. This work presents a methodology designed to obtain the turbocharger rotational speed via vibration analysis. Standard knock sensors have been employed in order to achieve a robust and accurate, yet still a low-cost solution capable of being mounted on-board. Results show that the developed method gives an estimation of the turbocharger rotational speed, with errors and accuracy acceptable for the proposed application. The method has been evaluated on a heavy duty diesel engine.
Technical Paper

Torque Estimation Based Virtual Crank Angle Sensor

2016-04-05
2016-01-1073
In engine management systems many calculations and actuator actions are performed in the crank angle domain. Most of these actions and calculations benefit from an improved accuracy of the crank angle measurement. Improved estimation of crank angle, based on pulse signals from an induction sensor placed on the flywheel of a heavy duty CI engine is thus of great importance. To estimate the crank angle the torque balance on the crankshaft is used. This torque balance is based on Newton’s second law. The net torque gives the flywheel acceleration which in turn gives engine speed and crank angle position. The described approach was studied for two crankshaft models: A rigid crankshaft approach and a lumped mass approach, the latter having the benefit of being able to capture the torsional effects of the crankshaft twisting and bending due to torques acting on it. These methods were then compared to a linear extrapolation of the engine speed, a common method to estimate crank angle today.
Technical Paper

Theoretical Assessment of Rigs for Accelerated Ash Accumulation in Diesel Particulate Filters

2020-09-15
2020-01-2175
Renewable fuels from different feedstocks can enable sustainable transport solutions with significant reduction in greenhouse gas emissions compared to conventional petroleum-derived fuels. Nevertheless, the use of biofuels in diesel engines will still require similar exhaust gas cleaning systems as for conventional diesel. Hence, the use of diesel particulate filters (DPF) will persist as a much needed part of the vehicle’s aftertreatment system. Combustion of renewable fuels can potentially yield soot and ash with different properties as well as larger amounts of ash compared to conventional fossil fuels. The faster ash build-up and altered ash deposition pattern lead to an increase in pressure drop over the DPF, increase the fuel consumption and call for premature DPF maintenance or replacement. Prolonging the maintenance interval of the DPF for heavy-duty trucks, having a demand for high up-time, is highly desirable.
Technical Paper

Surge Detection Using Knock Sensors in a Heavy Duty Diesel Engine

2017-09-04
2017-24-0050
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.
Technical Paper

Study of Nozzle Fouling: Deposit Build-Up and Removal

2019-12-19
2019-01-2231
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.
Technical Paper

Pressure Ratio Influence on Exhaust Valve Flow Coefficients

2017-03-28
2017-01-0530
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.
Technical Paper

Pressure Amplitude Influence on Pulsating Exhaust Flow Energy Utilization

2018-04-03
2018-01-0972
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.
Technical Paper

Particle Emission Measurements in a SI CNG Engine Using Oils with Controlled Ash Content

2019-01-15
2019-01-0053
Clean combustion is one of the inherent benefits of using a high methane content fuel, natural gas or biogas. A single carbon atom in the fuel molecule results, to a large extent, in particle-free combustion. This is due to the high energy required for binding multiple carbon atoms together during the combustion process, required to form soot particles. When scaling up this process and applying it in the internal combustion engine, the resulting emissions from the engine have not been observed to be as particle free as the theory on methane combustion indicates. These particles stem from the combustion of engine oil and its ash content. One common practice has been to lower the ash content to regulate the particulate emissions, as was done for diesel engines. For a gas engine, this approach has been difficult to apply, as the piston and valvetrain lubrication becomes insufficient.
Journal Article

Optimal Pressure Based Detection of Compressor Instabilities Using the Hurst Exponent

2017-03-28
2017-01-1040
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.
Technical Paper

On the effects of Turbocharger on Particle Number and Size Distribution in a Heavy - Duty Diesel Engine

2020-09-27
2020-24-0007
Particles emitted from internal combustion engines have adverse health effects. The severity varies based on the particle size as they deposit at different parts in the respiratory system. After-treatment systems are employed to control the particle emissions from combustion engines. The design of the after-treatment system depends on the nature of particle size distribution at the upstream and is important to evaluate. In heavy-duty (HD) diesel engines, the turbocharger turbine is an important component affecting the flow and particles. The turbine wheel and housing influence particle number and size could potentially be used in reducing particle number or changing the distribution to become more favourable for filtration. This work evaluates the effect of HD diesel engine’s turbine on non-volatile particle number and size distribution.
Technical Paper

On the Effects of Urea and Water Injection on Particles across the SCR Catalyst in a Heavy - Duty Euro VI Diesel Engine

2020-09-15
2020-01-2196
Particle emissions from heavy-duty engines are regulated both by mass and number by Euro VI regulation. Understanding the evolution of particle size and number from the exhaust valve to the tail pipe is of vital importance to expand the possibilities of particle reduction. In this study, experiments were carried out on a heavy-duty Euro VI engine after-treatment system consisting of diesel oxidation catalyst, diesel particulate filter and selective catalytic reduction (SCR) unit with AdBlue injection followed by ammonia slip catalyst. The present work focusses on the SCR unit with regard to total particle number with and without nucleation particles both. Experiments were conducted by varying the AdBlue injection quantity, SCR inlet temperature [to vary the reaction temperature], exhaust mass flow rate [to vary the residence time in SCR], and fuel injection pressures [to vary inlet particle number and inlet NOx].
Video

On the Effects of Urea and Water Injection on Particles across the SCR Catalyst in a Heavy - Duty Euro VI Diesel Engine

2020-09-17
Particle emissions from heavy-duty engines are regulated both by mass and number by Euro VI regulation. Understanding the evolution of particle size and number from the exhaust valve to the tail pipe is of vital importance to expand the possibilities of particle reduction. In this study, experiments were carried out on a heavy-duty Euro VI engine after-treatment system consisting of diesel oxidation catalyst, diesel particulate filter and selective catalytic reduction (SCR) unit with AdBlue injection followed by ammonia slip catalyst. The present work focusses on the SCR unit with regard to total particle number with and without nucleation particles both. Experiments were conducted by varying the AdBlue injection quantity, SCR inlet temperature [to vary the reaction temperature], exhaust mass flow rate [to vary the residence time in SCR], and fuel injection pressures [to vary inlet particle number and inlet NOx].
Technical Paper

Numerical Investigation of Increasing Turbulence through Piston Geometries on Knock Reduction in Heavy Duty Spark Ignition Engines

2019-12-19
2019-01-2302
Knock in heavy duty (HD) spark ignition (SI) engines is exacerbated by a large bore diameter and a higher flame travel distance. An increase in turbulence close to TDC can improve combustion speed and reduce knock through low residence time for end gas auto-ignition. Since HD SI engines are usually derived from diesel engines, it is common to have a swirl motion that does not dissipate into turbulence. To increase flame speed and limit knock, squish can be used to produce turbulence close to TDC. In this study, two different piston bowl geometries are examined: the re-entrant and quartette. The influence of squish area on turbulence production by these piston geometries were investigated using motored simulations in AVL FIRE. The effect of increased turbulence on knock reduction was analyzed using a calibrated 1D GT-Power model of a HD SI engine and the performance improvement was estimated.
Technical Paper

Numerical Flow Analysis of a Centrifugal Compressor with Ported and without Ported Shroud

2014-04-01
2014-01-1655
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.
Technical Paper

Knock Sensor Based Virtual Cylinder Pressure Sensor

2019-01-15
2019-01-0040
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.
Technical Paper

Knock Sensor Based Virtual Combustion Sensor Signal Bias Sensitivity

2018-04-03
2018-01-1154
The combustion in a direct injected internal combustion engine is normally open-loop controlled. The introduction of cylinder pressure sensors enables a virtual combustion sensor which in turn enables closed-loop combustion control, and the possibility 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 an investigation of the robustness and the limitation of a knock sensor based virtual combustion sensor. This virtual combustion sensor utilize the common heat release analysis using a knock sensor based virtual cylinder pressure signal. Major virtual sensor error sources in a heavy-duty engine were identified as: the specific heat ratio model, the boost pressure and the crank angle phasing. The virtual sensor errors were quantified in relation to both the measured cylinder pressure and the total virtual sensor error.
Technical Paper

Heavy-Duty Engine Intake Manifold Pressure Virtual Sensor

2019-04-02
2019-01-1170
Increasing demands for more efficient engines and stricter legislations on exhaust emissions require more accurate control of the engine operating parameters. Engine control is based on sensors monitoring the condition of the engine. Numerous sensors, in a complex control context, increase the complexity, the fragility and the cost of the system. An alternative to physical sensors are virtual sensors, observers used to monitor parameters of the engine thus reducing both the fragility and the production cost but with a slight increase of the complexity. In the current paper a virtual intake manifold cylinder port pressure sensor is presented. The virtual sensor is based on a compressible flow model and on the pressure signal of the intake manifold pressure sensor. It uses the linearized pressure coefficient approach to keep vital performance behaviors while still conserving calibration effort and embedded system memory.
Journal Article

Heat Loss Analysis of a Steel Piston and a YSZ Coated Piston in a Heavy-Duty Diesel Engine Using Phosphor Thermometry Measurements

2017-03-28
2017-01-1046
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.
Video

Experimental and Numerical Investigation of a Turbocharger Turbine Using Exergy Analysis at Non-Adiabatic Conditions

2020-09-17
Heat transfer in a turbocharger plays a crucial role in the optimization of turbocharger-engine matching process. Due to high temperature gradients between the hot exhaust gas compared to the compressor as well as the environment, it is well-known, that the heat loss from a turbocharger turbine is significant. Investigations of turbocharger performance are commonly done by quantifying the performance parameters under adiabatic conditions, following the paradigm of the first law of thermodynamics, based on the energy balance method. It turns out that an adiabatic assumption and the energy balance method is insufficient to provide a deep understanding about the aerothermodynamic effects on the turbine performance due to heat transfer. Based on the current state-of-the-art, this study aims to improve the characterization methods for passenger car turbocharger turbines, considering the impacts of heat transfer. Firstly, the turbocharger is measured on a hot gas test bench.
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