768 research outputs found
Randomized Benchmarking for Individual Quantum Gates
Any technology requires precise benchmarking of its components, and the
quantum technologies are no exception. Randomized benchmarking allows for the
relatively resource economical estimation of the average gate fidelity of
quantum gates from the Clifford group, assuming identical noise levels for all
gates, making use of suitable sequences of randomly chosen Clifford gates. In
this work, we report significant progress on randomized benchmarking, by
showing that it can be done for individual quantum gates outside the Clifford
group, even for varying noise levels per quantum gate. This is possible at
little overhead of quantum resources, but at the expense of a significant
classical computational cost. At the heart of our analysis is a
representation-theoretic framework that we develop here which is brought into
contact with classical estimation techniques based on bootstrapping and matrix
pencils. We demonstrate the functioning of the scheme at hand of benchmarking
tensor powers of T-gates. Apart from its practical relevance, we expect this
insight to be relevant as it highlights the role of assumptions made on unknown
noise processes when characterizing quantum gates at high precision.Comment: 4+13 pages, 4 figures, small changes, references adde
CFD investigation of the radiative heat transfer effects on the adoption of an electrical heated catalyst to increase the abatement efficiency
A preliminary computational analysis towards the use of Electrically Heated Mixing Catalyst for innovative SCR after-treatment systems
Numerical assessment of integrated thermal management systems in electrified powertrains
Temperatures in internal combustion engines (ICE) impact fuel consumption and pollutant emissions, especially under transient operating conditions. In hybrid powertrains, where the reciprocating internal combustion engine has intermittent operating conditions, a optimum control of these temperatures is critical. In this work, a detailed methodology for studying integrated thermal management systems for hybrid propulsion system was presented. Both experimental measurements and 0D/1D models were implemented and validated for the different components of the hybrid vehicle powertrain. The novelty of this work consists in the extensive experimental measurements involved for the development of the different models, specially the ICE, in order to study the integration of the different thermal flows of a hybrid powertrain. Furthermore, the simulation methodology used in this work integrates different modelling tools and takes advantage of their strengths when compared to using a single modelling tool. Two different thermal management systems have been evaluated under different Real Driving Emission (RDE) cycles at two different temperatures (at 20 °C and -20 °C). Results have shown that during the ICE warming up, the integrated thermal management system improved energy consumption by 1.74% and 3% for warm and cold conditions, respectively. This was because, the integrated TMS allows to avoid the temperature drop of the ICE when the propulsive system is in pure electric mode. Š 2022 Elsevier Lt
Development of a CFD methodology for fuel-air mixing and combustion modeling of GDI Engines
Simulation of GDI engines represents a very challenging task for CFD modeling. In particular, many sub-models are involved since the evolution of the fuel spray and liquid film formation should be modeled.
Furthermore, it is necessary to account for both the influence of mixture and flow conditions close to the spark plug to correctly predict the flame propagation process. In this work, the authors developed a CFD methodology to study the air-fuel mixing and combustion processes in direct-injection, spark-ignition engines. A set of sub-models was developed to describe injection, atomization, breakup and wall impingement for sprays emerging from multi-hole atomizers. Furthermore, the complete evolution of
the liquid fuel film was described by solving its mass, energy and momentum equations on the cylinderw wall boundaries. To model combustion, the Extended Coherent Flamelet Model (ECFM) was used in combination with a Lagrangian ignition model, describing the evolution of the flame kernel and
accounting for both for flow, mixture composition and properties of the electrical circuit. The proposed approach has been implemented into the Lib-ICE code, which is based on the OpenFOAMR technology.
In this paper, examples of application are provided, including the simulation of the fuel-air mixing process in a real GDI engine and the prediction of the premixed turbulent combustion process in a constant-volume vessel for different operating conditions
Real Driving Cycle Simulation of a Hybrid Bus by Means of a Co-Simulation Tool for the Prediction of Performance and Emissions
VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors
[EN] The paper describes the development in the OpenFOAMÂŽ
technology of a dynamic multiphase Volume-of-Fluid
(VoF) solver, supporting mesh handling with topological changes, that has been used for the study of the physics
of the primary jet breakup and of the flow disturbance induced by the nozzle geometry during the injector opening
event in high-pressure Gasoline Direct Injection (GDI) engines. Turbulence modeling based on a scale-resolving
approach has been applied, while phase change of fuel is accounted by means of a cavitation model that has been
coupled with the VOF solver. Simulations have been carried out on a 6-hole prototype injector, especially developed
for investigations in the framework of the collaborative project FUI MAGIE and provided by Continental Automotive
SAS. Special attention has been paid to the domain decomposition strategy and to the code development of the
solver, to ensure good load balancing and to minimize inter-processor communication, to achieve good performance
and also high scalability on large computing clusters.Giussani, F.; Montorfano, A.; Piscaglia, F.; Onorati, A.; Helie, J. (2017). VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 1009-1018. https://doi.org/10.4995/ILASS2017.2017.4989OCS1009101
A quasi 3D approach for the modelling of an automotive turbocharger's compressor
In this work the 3DCell method has been extended to the thermo-fluid dynamic simulation of an automotive turbocharger's compressor. The 3DCell, an approach continuously developed by the authors at Politecnico di Milano, is based on a pseudo-staggered leapfrog method that allows to decompose a generic 3D problem in a set of 1D scalar equation arbitrarily oriented in space. The system of equations has been solved referring to a relative rotating framework for the moving components, whereas to an absolute reference elsewhere. The domain has been discretized on a basis of a polar coordinate system, identifying five macro sub-domains, namely the inlet pipe, impeller, vaneless diffuser, volute, outlet pipe, each treated numerically in a specific way. The diffuser's momentum in the tangential direction has been modelled resorting to the conservation of the angular momentum, while the rotor channels are modelled as rotating pipes that exchange work and momentum with the blades as they experience a relative source term due to the centrifugal force field and its potential. The model has been validated against measurements carried out on a steady state flow test bench at University of Genoa
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