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Govindswamy K.,FEV Inc. | Eisele G.,FEV Motorentechnik GmbH
SAE Technical Papers | Year: 2011

The electrification of vehicle propulsion has caused a significant change in many areas including the world of vehicle acoustics. Comments from the media currently range from "silently hums the future" to "electric car roars with V8 sound". Decades of experience in designing brand-specific vehicle sound based on noise and vibration generated by combustion engines cannot be simply transferred to the upcoming vehicles driven purely by electric powertrains. Although electric vehicles are almost always considerably quieter than those powered by internal combustion engines, the interior noise is characterized by high-frequency noise components which can be subjectively perceived as annoying and unpleasant. Moreover, such disturbing noise is no longer masked by combustion engine noise. Fundamental questions regarding the sound design of electric vehicles have yet to be answered: it remains unclear what exactly the interior noise of an electric vehicle should sound like. Also questions regarding the approach to achieving a particular interior sound (e.g., use of artificially generated noise for desired sound) are still open. There is also an ongoing debate on the need for electric vehicles to emit additional noise in order to prevent the endangerment of pedestrians. The use of additional noise sources could work against the hope for noise reduction. This paper is intended as a contribution to the current discussion on what the target noise of electric vehicles could sound like and what possibilities currently exist for NVH engineers to design the sound of electric cars. Copyright © 2011 SAE International.

Wellmann T.,FEV Inc. | Govindswamy K.,FEV Inc. | Eisele G.,FEV Motorentechnik GmbH
SAE Technical Papers | Year: 2011

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage. While this is a proven tool for powertrain level sound quality evaluations and correlates well for front wheel drive (FWD) vehicles, the interior noise for rear wheel drive (RWD) vehicles is often under-predicted on account of missing contributions from the driveline. RWD vehicles can have significant contributions through the rear axle mounting paths, especially for powertrains with manual transmissions or during lock up of the torque converter clutch with conventional automatic transmissions. Torsional vibrations are transmitted through the driveline, causing reaction forces at the rear axle, resulting in driveline boom. Resonances in the driveline system typically amplify the driveline boom excitation. This publication extends the dB(VINS) approach for interior noise simulation by determining the driveline-induced noise of a RWD vehicle. The influence of the structureborne path and firing order related torsional vibration through the rear axle is demonstrated with a time domain transfer path process. Generic transfer functions for extension of the dB(VINS) process are developed in order to capture driveline noise share of RWD vehicles. In addition to vehicle measurements, a multi body simulation (MBS) model is generated and rear axle vibrations are calculated via MBS simulation of the vehicle driveline. The results are discussed in the context of driveline NVH integration and appropriate conclusions provided. Copyright © 2011 SAE International.

Fraidl G.K.,AVL List GmbH | Beste F.,AVL List GmbH | Kapus P.E.,AVL List GmbH | Korman M.,Graz University of Technology | And 2 more authors.
SAE Technical Papers | Year: 2011

For a broad acceptance of electric vehicles, the trade-off between all electric range and battery cost respectively weight represents the most important challenge. The all electric range obtained under real world conditions most often deviates significantly from the nominal value which is measured under idealized conditions. Under extreme conditions - slow traffic and demanding requirements for cabin heating or cooling - the electrical range might become less a question of spatial distance but even more of total operation time. Whereas with conventional powertrain, high flexibility of the total driving range can be obtained without sacrificing cost, with a pure battery vehicle this results in extreme high cost and weight of the energy storage. Therefore the difference between the typical daily driving range (e.g. in Germany 80-90% is below 50 km) and the minimum total range requested by most customers for acceptance of battery vehicles (200- 250 km), becomes essential. Based on the current battery technology, the most attractive approach is a battery capacity designed for the typical daily driving distance (e.g. 50 km) and an ICE powered Range Extender, covering larger energy requirements (higher power demand or longer driving distances). The most effective technical solution for such a Range Extender is largely determined by the ratio between pure battery operation and vehicle operation supported by the ICE. With primarily battery driven vehicles, the priorities for the ICE have to be set completely different compared to the conventional powertrain: NVH, package and weight are the most important items whereas the efficiency of the ICE is less important due to the low share of ICE operation. Hence, even ICE concepts, which are not optimal for pure ICE driven powertrains, proving to be ideal ICE for this kind of Range Extender application. For lowest cost and best fuel economy AVL developed a Range Extender solution with a unique 2-cylinder piston engine based on a cost and friction optimized design originating from 2-wheelers. With focus on best NVH, packaging and weight, an extremely compact and low weight Range Extender unit based on a highly integrated combination of a Rotary engine and an electric generator, was developed which also convinces with an outstanding NVH performance. This makes Range Extender solutions essential enablers for an affordable electric mobility. Copyright © 2011 SAE International.

Govindswamy K.,FEV Inc. | Tomazic D.,FEV Inc. | Genender P.,FEV GmbH | Schuermann G.,FEV GmbH
SAE Technical Papers | Year: 2013

The electrification of vehicle propulsion has changed the landscape of vehicle NVH. Pure electric vehicles (EV) are almost always quieter than those powered by internal combustion engines. However, one of the key challenges with the development of range extended electric vehicles (ReEV) is the NVH behavior of the vehicle. Specifically, the transition from the EV mode to one where the range extender engine is operational can cause significant NVH issues. In addition, the operation of the range extender engine relative to various driving conditions can also pose significant NVH concerns. In this paper internal combustion engines are examined in terms of their acoustic behavior when used as range extenders. This is done by simulating the vibrations at the engine mounting positions as well as the intake and exhaust orifice noise. By using a transfer path synthesis, interior noise components of the range extenders are calculated from these excitations. The results from this study show a few promising internal combustion engines concepts such as the inline-six-cylinder engine, the single-rotor Wankel engine, and the two-cylinder-boxer engine in combination with a neutral torque axis mounting. When using other mounting positions, an internal rolling moment compensation system is shown to reduce the engine vibrations and hence the interior noise. Copyright © 2013 SAE International.

Tousignant T.,FEV Inc | Govindswamy K.,FEV Inc | Leibling C.,FEV Inc
SAE Technical Papers | Year: 2011

It is commonly accepted that refined "powertrain sound quality" is essential to the development of a vehicle which will be well received by today's discriminating automotive customer. However, though there are several metrics which correlate well with a subjective impression of powertrain level inputs, what is ultimately important is the sound quality at driver's ear. Vehicle level powertrain sound quality is influenced by the powertrain noise and vibration (source) as well as the vehicle airborne and structureborne transfer functions (path). In development as well as benchmarking activities, it can be difficult to separate the influence of source and path on overall vehicle sound quality. Two unique time domain transfer path analysis techniques will be discussed here, which enable independent evaluations of powertrain and vehicle performance as they relate to sound quality: The Vehicle Interior Noise Simulation (VINS) process is a time domain transfer path analysis (TPA) tool which fully characterizes vehicle transfer functions and predicts driver's ear sound pressure based on powertrain inputs. This tool can provide insight into the specific sources and paths which can drive improvements in vehicle level powertrain sound quality. A derivative of this process is called dBVINS. Rather than characterizing a specific vehicle, the dBVINS process utilizes standard vehicle transfer functions which are based on a database of vehicles to represent an industry median virtual vehicle. This paper describes the means in which the VINS and dBVINS process can be used together to provide valuable insight during the benchmarking and development processes through independent comparison to targets of powertrain source and vehicle transfer path characteristics. Copyright © 2011 SAE International.

Haenel P.,FEV Inc. | Seyfried P.,FEV Inc. | Kleeberg H.,FEV Inc. | Tomazic D.,FEV Inc.
SAE Technical Papers | Year: 2011

Downsized direct-injected boosted gasoline engines with high specific power and torque output are leading the way to reduce fuel consumption in passenger car vehicles while maintaining the same performance when compared to applications with larger naturally aspirated engines. These downsized engines reach brake mean effective pressure levels which are in excess of 20 bar. When targeting high output levels at low engine speeds, undesired combustion events called pre-ignition can occur. These pre-ignition events are typically accompanied by very high cylinder peak pressures which can lead to severe damage if the engine is not designed to withstand these high cylinder pressures. Although these pre-ignition events have been reported by numerous other authors, it seems that their occurrence is rather erratic which makes it difficult to investigate or reliably exclude them. This paper describes a systematic engine dyno testing approach to force the engine into pre-ignition in order to study and characterize these events. A sensitivity study of various parameters shows that pre-ignition can occur repeatedly at the same load levels if boundary conditions are controlled sufficiently, meaning pre-ignition occurrence is less erratic than previously thought. Several hundred pre-ignition events have been recorded and analyzed in this study. A post-processing tool was developed and applied to analyze and characterize all recorded pre-ignition events. The knowledge gained out of these investigations will help to better understand the pre-ignition phenomena and what combustion development activities need to be applied in order to avoid or counteract pre-ignition during an engine development program or afterwards during customer usage in a passenger car. Copyright © 2011 SAE International.

Tousignant T.,FEV Inc. | Govindswamy K.,FEV Inc.
SAE Technical Papers | Year: 2014

Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented. A process, based on a time-domain transfer path methodology was applied to provide focused engineering development of powertrain and vehicle level NVH enablers. Specifically, this paper describes the process of virtually installing a Diesel powertrain into a carryover gasoline vehicle, then later into a prototype development vehicle and target vehicle. Results from the "virtual swaps" were utilized to assess the gaps to NVH targets and to develop a focused plan for development of powertrain and vehicle level NVH enablers. Copyright © 2014 SAE International.

Dahodwala M.,FEV Inc. | Joshi S.,FEV Inc. | Koehler E.W.,FEV Inc. | Franke M.,FEV Inc.
SAE Technical Papers | Year: 2014

The advantages of applying Compressed Natural Gas (CNG) as a fuel for internal combustion engines are well known. In addition to a significant operating cost savings due to a lower fuel price relative to diesel, there is an opportunity to reduce the engine's emissions. With CNG combustion, some emissions, such as Particulate Matter (PM) and Carbon Dioxide (CO2), are inherently reduced relative to diesel fueled engines due to the nature of the combustion and the molecular makeup of the fuel. However, it is important to consider the impact on all emissions, including Total Hydrocarbons (THC) and Carbon Monoxide (CO), which can increase with the use of CNG. Nitrogen Oxides (NOx) emission is often reported to decrease with the use of CNG, but the ability to realize this benefit is significantly impacted by the control strategy and calibration applied. FEV has investigated the emissions and performance impact of operating a heavy-duty diesel engine with CNG in a dual fuel mode. The CNG was introduced via injectors mounted to an inlet pipe located upstream of the intake manifold. The fumigation approach included a mixer to improve the distribution of gas prior to delivery to the cylinder. The initial investigations sought to determine how the performance of a heavy-duty diesel engine would be affected by the introduction of CNG. For this effort there was no change to the base engine calibration, and the ability to maximize substitution of diesel with CNG was investigated. It was observed that the ability to maximize substitution of diesel with CNG across the operating map was limited by extremely high THC levels, combustion instability and limitations in peak cylinder pressure and exhaust gas temperature. With the application of a simplified engine calibration with a single diesel injection and Exhaust Gas Recirculation (EGR), timing adjustments allowed higher CNG substitution levels in several areas of the operating map. A further increase in gas substitution along with higher fuel conversion efficiency, improved combustion stability and even lower emissions could be achieved through Reactivity Controlled Compression Ignition (RCCI) combustion. This approach required a unique injection strategy along with a careful balance of EGR rates and boost pressure. Under this combustion regime it was possible to observe a simultaneous reduction of NOx and PM emissions, approaching engine-out emission levels that could avoid, or significantly minimize, aftertreatment of these species. With the desire to quickly apply CNG systems to existing diesel engine architecture in an effort to reap the benefit in fuel cost savings, manufacturers and system developers must be careful to understand the full impact on the engine's performance and emissions. Tests conducted as part of this investigation have revealed that an un-optimized approach to CNG introduction can lead to extreme THC emissions that mostly consist of Methane (CH4). In addition, the maximum gas substitution level is significantly limited in most regions of the engine operating map. Thus, the ability to specifically tune the calibration for operation with CNG is essential to achieving the maximum benefit in fuel cost savings and emission control. Copyright © 2014 SAE International.

Wellmann T.,FEV Inc. | Govindswamy K.,FEV Inc. | Tomazic D.,FEV Inc.
SAE International Journal of Engines | Year: 2013

Automatic engine start/stop systems are becoming more prevalent and increasing market share of these systems is predicted due to demands on improving fuel efficiency of vehicles. Integration of an engine start/stop system into a "conventional" drivetrain with internal combustion engine and 12V board system is a relatively cost effective measure to reduce fuel consumption. Comfort and NVH aspects will continue to play an important role for customer acceptance of these systems. Possible delay during vehicle launch due to the engine re-start is not only a safety relevant issue but a hesitating launch feel characteristic will result in reduced customer acceptance of these systems. The engine stop and restart behavior should be imperceptible to the driver from both a tactile and acoustic standpoint. The lack of masking effects of the engine during the engine stop phases can cause other "unwanted" noise to become noticeable or more prominent. Other comfort related criteria like a stable 12V board supply during the engine start phase or A/C usage during the engine stop phase need to be considered as well. This paper provides an overview of start/stop systems and starter concepts. The requirements for different transmission types and the associated start/stop challenges are described. The phases of an engine start are described in detail, and their influence on the vehicle vibration investigated. NVH related metrics for describing the engine start/stop and vehicle launch are introduced. Key design parameters of the powertrain and driveline on the start/stop NVH behavior are studied. In addition, the impact of engine start on the vehicle's launch behavior is analyzed. Comparisons of different start/stop systems are conducted and results from case studies on the influence to launch delay and "change-of-mind" engine restart are provided. Finally, the effect of missing masking noise during the engine stop phases is discussed. Copyright © 2013 SAE International.

Fev Inc. | Date: 2013-10-08

computer hardware and software sold as a unit for power train analysis.

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