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Technical Paper

Design & Validation of Low-Cost Sound Intensity Probe

2019-06-05
2019-01-1462
Sound intensity measurement techniques, that used a two-microphone setup, were first developed in the late 1970s. Back then, the focus was on improving precision during testing or post-processing because the equipment available was inherently inaccurate. However, with the advent of modern, sophisticated equipment, the focus has shifted to the apparatus. Availability of phase-matched microphones has made post-test correction obsolete as the microphones eliminate a majority of the errors before the data is even collected. This accuracy, however, comes at a price, as phase-matched microphones are highly priced. This paper discusses employing the method of improving post-processing precision, using inexpensive, current equipment. The phase error of the system is corrected using a simple calibration technique and a handheld phase calibrator that is similar to the one used for amplitude calibration of microphones.
Technical Paper

Tonal Annoyance Metric Development for Automotive Electric Vehicles

2019-06-05
2019-01-1467
Historical metrics intended to drive the development of vehicle powertrains have focused on sounds that are characteristic of IC engines. The interior noise contribution of the propulsion system in electric vehicles has significantly more tonal noise than their IC engine counterparts. This tonal noise is not adequately represented by current propulsion systems metrics. While metrics exist today that were developed to represent the presence of tones in sounds most have focused on the level aspect of the tones relative to the surrounding noise or masking level, some examples include tonality, tone-to-noise ratio, and prominence ratio. A secondary, but also important aspect of tones is the annoyance as a function of frequency. This paper will highlight the development of a tonal annoyance weighting curve that can be used to account for the frequency aspect of tonal annoyance relative to electric vehicles.
Technical Paper

Effectiveness of Power-law Profile Indentations on Structure-Borne Noise

2019-06-05
2019-01-1496
With the focus shifting towards to the electric drives, owing to the stringent requirements for noise and vibrations, different measures are being taken to reduce the energy loss from the system via noise or heat dissipation but the conventional N&V approach of increasing the stiffness of the flexible component and reducing the mass may not always help in avoiding the resonance condition with the unwanted excitations owing to a wide range of operating range for motors and absence of engine noise makes it worse. Apart from any structural modifications, implementation of sound barriers like acoustic covers for sound absorption is also generally adopted for noise treatment. Locally modifying the structure thickness between two spatial locations helps in decreasing the reflection coefficient at the terminating edges thus reducing reflection of flexural waves.
Technical Paper

Sound Analysis Method for Warble Noise in Electric Actuators

2019-06-05
2019-01-1521
Multiple automotive applications exist for small electric motors that are activated by vehicle occupants for various functions such as window lifts and seat adjusters. For such a motor to be described as high quality, not only should the sound it produces be low in amplitude, but it also needs to be free from pulsations and variations that might occur during its (otherwise) steady-state operation. If a motor’s sound contains pulsations or variations between 2 and 8 cycles per second, the variation is described as warble. Warble noise needs to be measured and quantified in parts and vehicles, such that appropriate limits can be established whereby quality noise performance is conveyed in vehicles. Building on existing Sound Quality metrics such as Loudness and Pitch Variation, a method is established by which processed sound data is further processed via Fourier Analysis as a secondary operation.
Technical Paper

CAE Methods for Predicting Radiated Noise From Large Diameter Single-Piece Aluminum Propeller Shafts With Liner Treatments

2019-06-05
2019-01-1560
In recent truck applications, single-piece large-diameter propshafts, in lieu of two-piece propshafts, have become more prevalent to reduce cost and mass. These large-diameter props, however, amplify driveline radiated noise. The challenge presented is to optimize prop shaft modal tuning to achieve acceptable radiated noise levels. This paper will cover the development of a two-step CAE method to predict modal characteristics and airborne noise sensitivities of large-diameter single piece aluminum propshafts fitted with different liner treatments. The first step is the use of a traditional CAE software to calculate prop surface response. The second step is a boundary element simulation to calculate prop surface radiating noise under the excitation obtained from the first step. Finally, test data, acceleration and acoustic, in both subsystem and vehicle levels are presented to assess the accuracy of the CAE method.
Technical Paper

Aluminum Foil Perforation Impact on Acoustic and Thermal Performance of Automotive Sound Absorbers

2019-06-05
2019-01-1580
Adding aluminum foil on sound absorber surface has broad application in automotive industry. The foil layer offers thermal insulation for the parts close to exhaust pipes, turbo charge and other heat sources in engine compartment, it also adds physical protection in tough water-splashing/stone-impinging environment at vehicle exterior. It is known that adding impermeable plain foil will impact the sound absorption negatively, so micro perforated aluminum foil is widely used based on micro perforated absorption principle[]. Analytical results of sound absorption from micro-perforated panel or panel with fibrous substrate materials matches very well with measurement when perforation is well controlled in lab environment.
Technical Paper

PHEV Real World Driving Cycle and Energy and Fuel Consumption Reduction Potential for Connected and Automated Vehicles

2019-04-02
2019-01-0307
This paper presents real world driving energy and fuel consumption results for the second-generation Chevrolet Volt plug-in hybrid electric vehicle (PHEV). A drive cycle, local to Michigan Technological University, was designed to mimic urban and highway driving test cycles in terms of distance, transients and average velocity, but with significant elevation changes to establish an energy intensive real world driving cycle for assessing potential energy savings for connected and automated vehicle control. The investigation began by establishing baseline and repeatability of energy consumption at various battery states of charges. It was determined that drive cycle energy consumption under a randomized set of boundary conditions varied within 3.4% of mean energy consumption regardless of initial battery state of charge.
Technical Paper

Impinged Diesel Spray Combustion Evaluation for Indirect Air-Fuel Mixing Processes and Its Comparison with Non-Vaporing Impinging Spray Under Diesel Engine Conditions

2019-04-02
2019-01-0267
Under low-temperature combustion for the high fuel efficiency and low emissions achievement, the fuel impingement often occurs in diesel engines with direct injection especially for a short distance between the injector and piston head/cylinder wall. Spray impingement plays an important role in the mixing-controlled combustion phase since it affects the air-fuel mixing rate through the disrupted event by the impingement. However, the degree of air entrainment into the spray is hard to be directly evaluated. Since the high spray expansion rate could allow more opportunity for fuel to mix with air, in this study, the expansion rate of impinged flame is quantified and compared with the spray expansion rate under non-vaporizing conditions. The experiments were conducted in a constant volume combustion chamber with an ambient density of 22.8 kg/m3 and the injection pressure of 150 MPa.
Technical Paper

Computationally Efficient Reduced-order Powertrain Model of a Multi-mode Plug-in Hybrid Electric Vehicle for Connected and Automated Vehicles

2019-04-02
2019-01-1210
This paper presents the development of a reduced-order powertrain model for energy and SOC estimation of a multi-mode plug-in hybrid electric vehicle with velocity and elevation inputs. Such a model is intended to overcome the computational inefficiencies of higher fidelity powertrain and vehicle models in short and long horizon optimization efforts such as Coordinated Adaptive Cruise Control (CACC), Eco Approach and Departure (Eco AND), Eco Routing, and PHEV mode blending. The reduced-order powertrain model enables Connected and Automated Vehicles (CAVs) to utilize the onboard sensor and connected data to quickly react and plan their maneuvers to highly dynamic road conditions with minimal computational resources. Although overall estimation accuracy is less than neural network and high-fidelity models, emphasis on runtime minimization with reasonable estimation accuracy enables energy optimization of CAV without a need for computationally expensive server-based models.
Technical Paper

Numerical Parametric Study of a Six-Stroke Gasoline Compression Ignition (GCI) Engine Combustion

2019-04-02
2019-01-0207
Numerical investigation of engine performance and emissions of a six-stroke gasoline compression ignition (GCI) engine combustion at low load conditions is presented. In order to identify the effects of additional two strokes of the six-stroke engine cycle on the thermal and chemical conditions of charge mixtures, an in-house multi-dimensional CFD code coupled with high fidelity physical sub-models along with the Chemkin library was employed. The combustion and emissions were calculated using a reduced chemical kinetics mechanism for a 14-component gasoline surrogate fuel. Two power strokes per cycle were achieved using multiple injections during compression strokes. Parametric variations of injection strategy viz., individual injection timing for both the power strokes and the split ratio that enable the control of combustion phasing of both the power strokes were explored.
Technical Paper

Investigation of the Effects of Heat Transfer and Thermophysical Properties on Dynamics of Droplet-Wall Interaction

2019-04-02
2019-01-0296
Fuel spray-wall interaction frequently occurs on intake manifold wall in the port fuel injection engine and on the piston in the direct injection engine, especially during the cold start. The heat transfer between the spray and wall is involved in this interaction process and influences the dynamics of the impinged spray which can further affect the engine performance. The physics of impact dynamics of a single droplet serves as a fundamental for better comprehension of spray impingement. In our previous studies, we have focused on diesel droplets, at ambient temperature, impinging on both heated and non-heated wall and found impinged droplet morphology differences. To understand the effect of heat transfer and thermophysical properties on dynamics of droplet-wall interaction better, droplet temperature variation was introduced in this study. Therefore, different conditions were framed to explore the impact of thermophysical properties of the droplet.
Technical Paper

Route Optimized Energy Management of a Connected and Automated Multi-mode Hybrid Electric Vehicle using Dynamic Programming

2019-04-02
2019-01-1209
This paper presents a methodology to optimize the blending of Charge Depleting (CD) and Charge Sustaining (CS) modes in a multi-mode plug-in hybrid electric vehicle (PHEV) that reduces overall energy consumption when the selected route cannot be drive purely electric. The PHEV used in this investigation is the second generation Chevrolet Volt and as many as four instrumented vehicles were utilized simultaneously on road to acquire validation data. The optimization method utilized is dynamic programming (DP) and is paired with a reduced fidelity propulsion system and vehicle dynamics model to enable compatibility with embedded controllers and be computationally efficient of the optimal blended operating scheme over an entire drive route.
Technical Paper

Fast Gas Analyzer Observations of Stochastic Preignition Events

2019-04-02
2019-01-0254
The goal of this study was to generate exhaust fast gas data that could be used to identify phenomena that occur before, during, and after stochastic preignition (SPI), also called low-speed preignition (LSPI), events. Crank angle resolved measurement of exhaust hydrocarbons, NO, CO, and CO2 was performed under engine conditions prone to these events. Fuels and engine operating strategies were varied in an attempt to understand similarities and differences in SPI-related behavior that may occur between them. Several different uncommon (typically occurring in less than 1% of engine cycles) features of the fast gas data were identified, and the correlations between them and SPI events were explored. Although the thresholds used to define and identify these observations were arbitrary, they provided a practical means of identifying behavior in the fast gas data and correlating it to SPI occurrence.
Technical Paper

A Qualitative and Quantitative Aerodynamic Study of a Rotating Wheel inside a Simplified Vehicle Body and Wheel Liner Cavity

2019-04-02
2019-01-0658
As automotive OEMs (Original Equipment Manufacturer) struggle to reach a balance between Design and Performance, environmental legislations continues to demand more rapid gains in vehicle efficiency. As a result, more attention is being given to the contributions of both tire and wheels. Not only tire rolling resistance, but also tire and wheel aerodynamics are being shown to be contributors to overall efficiency. To date, many studies have been done to correlate CFD simulations of rotating wheels both in open and closed wheeled environments to windtunnel results. Whereas this ensures proper predictive capabilities, little focus has been given to thoroughly explaining the physics that govern this complex environment. This study seeks to exhaustively investigate the complex interactions between the ground, body, and a rotating tire/wheel.
Technical Paper

Methods of Pegging Cylinder Pressure to Maximize Data Quality

2019-04-02
2019-01-0721
Engine cylinder pressure is traditionally measured with a piezo-electric pressure transducer, and as such, must be referenced or pegged to a known value. Frequently, the cylinder pressure is pegged to the pressure in the intake manifold plenum whereby the manifold absolute pressure (MAP) at the end of the intake stroke is measured and the cylinder pressure trace for the entire cycle is adjusted such that the cylinder pressure is set equal to the manifold pressure at the end of the intake stroke. However, any error in pegging induces an error in the cylinder pressure trace, which has an adverse effect on the entire combustion analysis. This research is focused on assessing the pegging error for several pegging methods across a wide range of engine operating conditions, and ultimately determining best practices to minimize error in pegging and the calculated combustion metrics. The study was conducted through 1D simulations using the commercially available GT-Power.
Technical Paper

Spark Mechanism in High Speed Flow

2019-04-02
2019-01-0729
An experimental study was performed to investigate spark ignition and subsequent spark stretch evolution in an inert environment at high- flow velocities up to 32 m/s across the spark plug gap in a constant-volume optical combustion-vessel at pressures representative of those in an engine. The vessel is capable of generating various in-cylinder thermodynamic conditions representative of light-duty spark ignition engines. The characteristic behavior of the spark was investigated using both a high-speed optical diagnostics and electrical measurement. Charge gas pressures were varied from 15 to 45 bar. Results show that the spark, flowing downstream the spark plug, is subject to short circuits of the spark channel and/or restrikes. The frequency of the restrike increased with increased flow velocity and charge gas pressure and decreased discharge current level.
Technical Paper

Investigation and Optimization of Cam Actuation of an Over-Expanded Atkinson Cycle Spark-Ignited Engine

2019-04-02
2019-01-0250
An over-expanded spark ignited engine was investigated in this work via engine simulation with a design constrained, mechanically actuated Atkinson cycle mechanism. A conventional 4-stroke spark-ignited turbo-charged engine with a compression ratio of 9.2 and peak brake mean effective pressure of 22 bar was selected for the baseline engine. With geometry and design constraints including bore, stroke, compression ratio, clearance volume at top dead center (TDC) firing, and packaging, one over-expanded engine mechanism with over expansion ratio (OER) of 1.5 was designed. Starting with a validated 1D engine simulation model which included calibration of the in-cylinder heat transfer model and SI turbulent combustion model, investigations of the Atkinson engine including cam optimization was studied. The engine simulation study included the effects of offset of piston TDC locations as well as different durations of the 4-strokes due to the mechanism design.
Technical Paper

Influence of Elevated Injector Temperature on the Spray Characteristics of GDI Sprays

2019-04-02
2019-01-0268
When fuel at elevated temperatures is injected into an ambient environment at a pressure lower than the saturation pressure of the fuel, the fuel vaporizes in the nozzle and/or immediately upon exiting the nozzle; that is, it undergoes flash boiling. It is characterized by a two-phase flow regime co-located with primary breakup, which significantly affects the spray characteristics. Under flash boiling conditions, the near nozzle spray angle increases, which can lead to shorter penetration because of increased entrainment. In a multi-hole injector this can cause other impacts downstream resulting from the increased plume to plume interactions. To study the effect of injector temperature and injection pressure with real fuels, an experimental investigation of the spray characteristics of a summer grade gasoline fuel with 10% ethanol (E10) was conducted in an optically accessible constant volume spray vessel.
Technical Paper

Control-Oriented Modeling of a Vehicle Drivetrain for Shuffle and Clunk Mitigation

2019-04-02
2019-01-0345
Flexibility and backlash of vehicle drivelines typically cause unwanted oscillations and noise, known as shuffle and clunk, during tip-in and tip-out events. Computationally efficient and accurate driveline models are necessary for the design and evaluation of torque shaping strategies to mitigate this shuffle and clunk. To accomplish these goals, this paper develops a full-order physics-based model and uses this model to develop a reduced-order model (ROM), which captures the main dynamics that influence the shuffle and clunk phenomena. The full-order model (FOM) comprises several components, including the engine as a torque generator, backlash elements as discontinuities, and propeller and axle shafts as compliant elements. This model is experimentally validated using the data collected from a Ford vehicle. The validation results indicate less than 1% error between the model and measured shuffle oscillation frequencies.
Technical Paper

Control Strategy and Energy Recovery Potential for P2 Parallel Hybrid Step Gear Automatic Transmissions

2019-04-02
2019-01-1302
The purpose of this investigation is to present a control strategy and energy recovery potential for P2 parallel hybrid step gear automatic transmissions. The automatic transmission types considered for the investigation are rear wheel drive 8 speed dual clutch transmission and 8 speed planetary automatic equipped each equipped with an electric motor between the engine and transmission. The governing equations of clutch-to-clutch upshift controls are presented and are identical for each transmission type. Various strategies are explored for executing the upshift under a range of input torques, shift times and engine torque management approaches. The differences in energy recovery potential based upon control strategy is explored piecewise as well as through a DFSS study. On a comprehensive drive cycle consisting of FTP 75, US06 and HWFET test cycles, it is shown that upshift regen torque management can be equivalent to approximately 0.8% of the total fuel energy used.
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