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Technical Paper

ICICLE: A Model for Glaciated & Mixed Phase Icing for Application to Aircraft Engines

2019-06-10
2019-01-1969
High altitude ice crystals can pose a threat to aircraft engine compression and combustion systems. Cases of engine damage, surge and rollback have been recorded in recent years, believed due to ice crystals partially melting and accreting on static surfaces (stators, endwalls and ducting). The increased awareness and understanding of this phenomenon has resulted in the extension of icing certification requirements to include glaciated and mixed phase conditions. Developing semi-empirical models is a cost effective way of enabling certification, and providing simple design rules for next generation engines. A comprehensive ice crystal icing model is presented in this paper, the Ice Crystal Icing ComputationaL Environment (ICICLE). It is modular in design, comprising a baseline code consisting of an axisymmetric or 2D planar flowfield solution, Lagrangian particle tracking, air-particle heat transfer and phase change, and surface interactions (bouncing, fragmentation, sticking).
Technical Paper

A Case Study on Golf Car Powertrain NVH Sources and Mitigation Methods

2019-06-05
2019-01-1478
The golf market has remained flat in North America. Whereas, it has grown worldwide. A trend is seen where the number of young adults and adults over the age of 65 years involved with the game has increased. The demographics in golf showing the most growth also have high standards for the operation of the golf car. They have transcended their expectations to align with some of the qualities expected of automobiles. There is a shift in consumer expectations. Moreover, the market competition has also increased. This drives the OEMs to deliver refined golf cars with NVH being a key aspect in development. This paper showcases a recent study to improve the powertrain N&V performance of an internal combustion engine golf car. Primarily, a test-based approach is followed. Chassis rolls and on road testing are performed for benchmarking and target setting. System and component tests are performed to root cause issues.
Technical Paper

Test and Analysis of Electromagnetic Noise of an Electric Motor in a Pure Electric Car

2019-06-05
2019-01-1492
Compared with the low-frequency ignition order of mechanical and combustion noise of an internal combustion engine, the noise of electric drive assembly of electric vehicles is mainly the high-frequency whining noise generated by electromagnetic forces of motors and gear meshing of reducers, as well as the high-frequency umbrella-shape noise generated by DC/AC pulse width modulation. Although the radiated sound power of these high frequency noise is far less than that of an internal combustion engine, the high frequency noise of the motor and the reducer is subjectively quite annoying. This paper studies the characteristics of electromagnetic noise of a permanent magnet synchronous motor in an electric car. By testing and analyzing of noise sources of an electric motor in the car and on a test rig, the spatial order characteristics and amplitude-frequency characteristics of the electromagnetic forces are revealed. The noise orders are multiples of the number of motor poles.
Technical Paper

On the Measurement and Simulation of Flow-Acoustic Sound Propagation in Turbochargers

2019-06-05
2019-01-1488
Internal combustion engines are increasingly being equipped with turbochargers to increase performance and reduce fuel consumption and emissions. Being part of exhaust and intake systems, the turbocharger strongly influences the orifice noise emission. Although 1D-CFD simulations are commonly used for the development of intake and exhaust systems, validated acoustic turbocharger models are not yet state-of-the-art. Consequently, the aim of the paper is the investigation of the turbocharger’s influence on the orifice noise and the development of an accurate 1D-CFD model. The passive acoustic transmission loss was measured for a wide operating range of four turbochargers, including wastegate and VTG-system variations. Low frequency attenuation is dominated by impedance discontinuities, increasing considerably with mass flow and pressure ratio.
Technical Paper

The New Challenges of NVH Package for BEVs

2019-06-05
2019-01-1452
Battery electric vehicles (BEVs) bring new challenges when it comes to NVH package development, which are affected by many new factors. The noise sources from the powertrain are different, for instance due to the presence of tonal components, strong harmonics and potential whining noise. Another important aspect is the missing effect of masking noise from a combustion engine. As a consequence, other noise sources, such as tires, become more predominant. This means that the NVH package has to be re-engineered considering new noise sources and cannot just be significantly decontented in general. At the same time, NVH package weight reduction should at least partly counterbalance the vehicle weight increase due to the presence of a large and heavy battery pack in order to maximize the driving range. In the early days of BEVs, OEMs mostly carried over technologies used on combustion engine vehicles to electric cars.
Technical Paper

Benefit of a Lightweight Frunk

2019-06-05
2019-01-1456
Due to the increasing number of battery electric vehicles (BEVs), the engineering fields regarding driving comfort and NVH issues are becoming more and more challenging: many new factors affect the development of BEVs NVH package. The noise sources related to the powertrain are different from the traditional ones of internal combustion engines, for instance due to the presence of tonal components, strong harmonics and potential whining noise. To satisfy NVH specifications and the need for lightweight solutions to increase driving range, it is important to mask as much as possible the noise coming from the engine bay with materials both lightweight and acoustically performing. Moreover, for electric vehicles new interesting solutions are possible with the introduction of new components that do not find room under the hood of ICE or hybrid vehicles. These components, if properly designed, could lead to significant NVH benefits.
Technical Paper

Machine Learning Algorithm for the Prediction of Idle Combustion Uniformity

2019-06-05
2019-01-1551
Combustion stability is a key contributor to engine shake at idle speed and can impact the overall perception of vehicle quality. The sub-firing harmonics of the combustion torque are used as a metric to assess idle shake and are, typically, measured at different levels of engine break mean effective pressure (BMEP). Due to the nature of the combustion phenomena at idle, it is clear that predicting the cycle-to-cycle and cylinder-to-cylinder combustion pressure variations, required to assess the combustion uniformity, cannot be achieved with the state of the art simulation technology. Inspired by the advancement in the field of machine learning and artificial intelligence and by the availability of a large amount of measured combustion test data, this paper explores the performance of various machine learning algorithms in predicting the idle combustion uniformity.
Technical Paper

Model Verification of CAE with NVH-Test Acting on Downsized Car Engines

2019-06-05
2019-01-1550
Today’s trend of combustion engine development for cars is characterized with; high torque, low engine speed, low weight, high degree of cyclic irregularity, low excitation frequency due to fewer cylinders active e.g. 4-cylinder or less. This implies in respect of vibrations that it is crucial to control powertrain rigid body modes and place these were they cannot be reached and induced by the low exciting harmonic frequencies for low engine speeds or idling. It is also important to control the overall flexible vibration modes. A mathematical CAE model is created in simulation software AVL-EXCITE in order to handle the vibration phenomenon as a first step. But it is absolutely necessary to “verify” these models with real measurements in respect of NVH and if needed upgrade the CAE model if there are detected deviations. The NVH-test is done with testing tool DEWESoft. The purpose of below paper is to do model verification on a concrete example in respect of powertrain vibrations.
Technical Paper

The Influence of Connecting-Rod Specifications on the Combustion-Noise Generation from a Diesel Engine

2019-06-05
2019-01-1590
We experimentally investigated the influence of shifting natural frequencies of the internal transmission system depending on the connecting-rod specifications on the characteristics of noise radiated from a single-cylinder diesel engine. We used FFT analysis to investigate the influence of shifting natural frequencies of the internal transmission system on the radiated noise characteristics. By changing the thinned portion of the connecting-rod, we confirmed that the natural frequency of the piston-connecting-rod-coupled vibration differed from another natural frequency of the engine structure, and thus the engine noise was reduced. This research studied the time-frequency characteristics of combustion impact and engine noise by wavelet analysis of in-cylinder pressure and sound pressure.
Technical Paper

Structure-Borne Path Identification of Rumbling Noise in a Passenger Car Based on In-Situ Blocked Force Transfer Path Analysis

2019-06-05
2019-01-1587
It is known that the major source of rumbling noise the combustion force of an engine. The combustion force excites the engine and induces vibrations of the powertrain. These vibrations are then transferred to the body of the vehicle via its structural transfer path. Moreover, the vibrations of the vehicle’s body emit internal vibra-acoustic noise. This noise is often referred to as the rumbling noise due to the structural borne path. If there are structural resonances among the structural paths such as the engine, transmission, mount bracket, suspension, and the vehicle’s body, the rumbling noise could be amplified. To identify the major resonances of the structural transfer path, classical transfer path analysis (CTPA) has been traditionally utilized. The method has a significant limitation in that it is necessary to decouple the substructures to obtain the contact force between individual components and to identify the transfer path of the structure-borne sound.
Technical Paper

Improved Measurement Procedures for Engine Noise Reduction with Advanced Microphones

2019-06-05
2019-01-1463
The acoustic environment inside the car is a primary comfort parameter. With the change from internal combustion engines (ICE) to electrical (BEV) or electrically assisted (HEV) propulsion systems, a renewed focus on old and new noise sources in the engine bay and the transmission paths to the cabin is required. A way to study this is by using a reverse transmission technique, placing a sound source in the receiver position in the cabin and measure the resulting sound pressure levels in the engine bay. Assuming reciprocity, the attenuation of transmission from sound sources in the engine bay to the cabin can be estimated. These measurements are cumbersome as they involve the placement of 20 or more microphones in the engine bay. This has traditionally been performed using off-the-shelf free-field measurement microphones. To optimize this procedure a new pressure-field microphone has been tested by Volvo Cars.
Technical Paper

Noise and Vibration End-of-Line Production Testing and Analysis Challenges

2019-06-05
2019-01-1464
Theoretical modeling continues to play a larger role in noise and vibration engineering; however, until products are perfectly made, there will be a need to evaluate their end of the production line performance. Manufacturing production of a wide range of items has classically involved some amount of subjective and/or evolved objective quality testing along, or at the end of the production line. This testing can have goals of determining product safety, durability, functionality, and/or the vibration/sound quality. A vibration-based measurement approach is frequently used for many of those goals. Often, many modern products utilize some combination of electric motors, internal combustion engines, and power transmission rotational components. The end-of-line testing for many of these rotational components is after many years now heavily refined in the measurement and analysis methods, and the separation of good, bad and marginally bad samples may not always be challenging.
Journal Article

Role of Piston Bowl Shape to Enhance Late-Cycle Soot Oxidation in Low-Swirl Diesel Combustion

2019-04-25
Abstract Late-cycle soot oxidation in heavy-duty (HD) diesel engine low-swirl combustion was investigated using single-cylinder engine and spray chamber experiments together with engine combustion simulations. The in-cylinder flow during interactions between adjacent flames (flame-flame events) was shown to have a large impact on late-cycle combustion. To modify the flame-flame flow, a new piston bowl shape with a protrusion (wave) was designed to guide the near-wall flow. This design significantly reduced soot emissions and increased engine thermodynamic efficiency. The wave’s main effect was to enhance late-cycle mixing, as demonstrated by an increase in the apparent rate of heat release after the termination of fuel injection. Combustion simulations showed that the increased mixing is driven by enhanced flow re-circulation, which produces a radial mixing zone (RMZ).
Standard

Oxygen Cylinder Installation Guide

2019-04-11
CURRENT
ARP5021B
This document provides guidance for oxygen cylinder installation on commerical aircraft based on airworthiness requirements, and methods practiced within aerospace industry. It covers considerations for oxygen systems from beginning of project phase up to production, maintenance, and servicing. The document is related to requirements of DOT-approved oxygen cylinders, as well to those designed and manufactured to standards of ISO 11119. However, its basic rules may also be applicable to new development pertaining to use of such equipment in an oxygen environment. For information regarding oxygen cylinders itself, also refer to AIR825/12.
Standard

Misfire Generator Functional Requirements

2019-04-11
CURRENT
J2901_201904
The intent of the specification is to present a functional set of requirements which define the user and hardware interfaces while providing sufficient capability to meet the misfire patterns for compliance demonstration and engineering development. Throughout this requirement, any reference to “ignition or injector control signal” is used interchangeably to infer that the effected spark ignition engine’s ignition control signal or the compression ignition engine’s injector control signal is interrupted, timing phased, or directly passed by the misfire generator. For spark ignition engines, the misfire generator behaves as a spark-defeat device which induces misfires by inhibiting normal ignition coil discharge. It does so by monitoring the vehicle’s ignition timing signals and suspends ignition coil saturation for selected cylinder firing events. The misfire generator will thereby induce engine misfire in spark ignited gasoline internal combustion engines; including rotary engines.
Technical Paper

Scavenged Pre-Chamber Volume Effect on Gas Engine Performance and Emissions

2019-04-02
2019-01-0258
This work presents development and results of experimental and numerical investigations of an advanced ignition system with a scavenged pre-chamber for a natural gas fueled engine with a bore of 102 mm and stroke of 120 mm. Two combustion concepts are taken into account. The lean burn concept is used to minimize engine out emissions of nitric oxides (NOx) and to achieve high thermal efficiency at low load. The in-house designed scavenged pre-chamber enables the engine to be operated up to the air-excess ratio (lambda) of 2. A stoichiometric (lambda=1) operation is also possible. It is compatible with a three-way catalyst concept, at high load and potentially transient modes and can provide as high as possible engine power density. The influence of the scavenged pre-chamber volume on the combustion and performance within the range of the operational points of the naturally aspirated engine is presented in this paper.
Technical Paper

Experimental and Numerical Analysis of Pre-Chamber Combustion Systems for Lean Burn Gas Engines

2019-04-02
2019-01-0260
The current trend in automobiles is towards electrical vehicles, but for the most part these vehicles still require an internal combustion engine to provide additional range and flexibility. These engines are under stringent emissions regulations, in particular, for the reduction of CO2. Gas engines which run lean burn combustion systems provide a viable route to these emission reductions, however designing these engines to provide sustainable and controlled combustion under lean conditions at λ=2.0 is challenging. To address this challenge, it is possible to use a scavenged Pre-Chamber Ignition (PCI) system which can deliver favorable conditions for ignition close to the spark plug. The lean charge in the main combustion chamber is then ignited by flame jets emanating from the pre-chamber nozzles. Accurate prediction of flame kernel development and propagation is essential for the analysis of PCI systems.
Technical Paper

Achieving Ultra-Lean Combustion Using a Pre-Chamber Spark Ignition System in a Rapid Compression-Expansion Machine

2019-04-02
2019-01-0236
Combustion processes operating under fuel lean conditions are a promising technology for internal combustion engines, achieving low emissions and very high efficiency. In traditional spark ignition engines, the charge dilution affects the flame propagation speed, leading to a combustion instability. A way to overcome these limits consists on the replacement of the spark with a pre-chamber ignition system. The combustion starts in the pre-chamber and develops in the main chamber through multiple and distributed ignition points, ensuring fast burn rate and stability. This paper focuses on the performance evaluation of a pre-chamber spark ignition system operating under ultra-lean conditions. An experimental campaign is carried out using a rapid compression-expansion machine fueled with liquid iso-octane as a surrogate fuel for gasoline.
Technical Paper

Computational Optimization of Pressure Wave Reflection on the Piston Surface for Single Point Autoignition Gasoline Engine with Colliding Pulsed Supermulti-Jets Leading to Noiseless-High Compression and Nearly-Complete Air-Insulation

2019-04-02
2019-01-0235
A new engine concept based on pulsed supermulti-jets colliding at a small area around the chamber center was proposed in our previous research. It was expected to provide noiseless high compression ratio and nearly-complete air-insulation on chamber walls, leading to high thermal efficiency. In the previous reports, three-dimensional computations for the unsteady compressible Navier-Stokes equation were conducted, which were qualitative because of using regular grid method. This time, we develop a new numerical code in order to quantitatively simulate the compression level caused by the jets colliding with pulse. It is achieved by applying a staggered grid method to improve conservatibity of physical quantities at very high compression in combustion phenomena. Computations at a simple condition were fairly agreed with a theoretical value. Computational results obtained for a complex geometry of an engine by the new code had less error than one with previous codes.
Technical Paper

A Dynamic Test Bench for the Assessment of Common Rail Fuel Injection Systems Impact on CO2 Emissions over the WLTP Cycle

2019-04-02
2019-01-0292
The internal combustion engine technological development is today driven by the pollutants and carbon dioxide (CO2) emission reduction targets imposed by law. The request of lowering CO2 emission reflected in a push towards the improvement of engine efficiency, without sacrificing performances and drivability. The latest generations of Diesel engines for passenger cars are characterized by increasing injection pressure levels (250 MPa for the current production). Enhancing the injection pressure has the drawback of increasing the energy needed to pressurize the fuel and thus the high-pressure fuel pump energy request. A small but not negligible quantity of fuel has to be burned in order to provide this energy, generating a contribution in CO2 emission. In this frame, the injector back-flow represents a significant energy loss for the fuel injection system and for the whole engine.
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