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An Approach for Heavy-Duty Vehicle-Level Engine Brake Performance Evaluation

SAE International Journal of Commercial Vehicles

Navistar, Inc., USA-Peirong Jia
  • Journal Article
  • 02-12-01-0005
Published 2019-01-08 by SAE International in United States
An innovative analysis approach to evaluate heavy-duty vehicle downhill engine brake performance was developed. The vehicle model developed with GT-Drive simulates vehicle downhill control speeds with different engine brake retarding powers, transmission gears, and vehicle weights at sea level or high altitude. The outputs are then used to construct multi-factor parametric design charts. The charts can be used to analyze the vehicle-level engine brake capabilities or compare braking performance difference between different engine brake configurations to quantify the risk of engine retarding power deficiency at both sea level and high altitude downhill driving conditions. The methodology and the models can address the following topics in steady-state operation with a robust engine analysis approach: (1) design criteria of the engine brake in vehicle system integration, (2) vehicle braking capability evaluations, (3) comparison between different engine brakes or different transmissions at both sea level and high altitude, (4) vehicle braking power shortage analysis and risk evaluation, (5) extra absorbed power and energy of service brakes of the vehicle due to retarding power shortage, and (6) comprehensive interactions…
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Design of High-Lift Airfoil for Formula Student Race Car

SAE International Journal of Commercial Vehicles

Ain Shams University, Egypt-Abdelrahman Ibrahim Mahgoub, Hashim El-Zaabalawy, Walid Aboelsoud, Mohamed Abdelaziz
  • Journal Article
  • 02-12-01-0002
Published 2018-12-05 by SAE International in United States
A two-dimensional model of three elements, high-lift airfoil, was designed at a Reynolds number of 106 using computational fluid dynamics (CFD) to generate downforce with good lift-to-drag efficiency for a formula student open-wheel race car basing on the nominal track speeds. The numerical solver uses the Reynolds-averaged Navier-Stokes (RANS) equation model coupled with the Langtry-Menter four-equation transition shear stress transport (SST) turbulence model. Such model adds two further equations to the k − ω SST model resulting in an accurate prediction for the amount of flow separation due to adverse pressure gradient in low Reynolds number flow. The k − ω SST model includes the transport effects into the eddy-viscosity formulation, whereas the two equations of transition momentum thickness Reynolds number and intermittency should further consider transition effects at low Reynolds number. Starting with a baseline design using the understanding of high-lift airfoils, all elements were arranged using an Eppler E421 profile. The lift coefficient was improved by varying the flaps’ overlaps, gaps, and deflection angles sequentially, thus testing 31 rigging combinations. Finally, these data…
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Numerical Analysis of Blast Protection Improvement of an Armored Vehicle Cab by Composite Armors and Anti-Shock Seats

SAE International Journal of Commercial Vehicles

Beijing Mechanical Equipment Institute and Tsinghua University, China-Yan-Peng Dong
Tsinghua University, China-Zhen-Hua Lu
  • Journal Article
  • 02-12-01-0001
Published 2018-12-05 by SAE International in United States
The objective of this article is to evaluate the effects of different blast protective modules to military vehicle structures and occupants. The dynamic responses of the V-shape integral basic armor, the add-on honeycomb sandwich structure module, and the anti-shock seat-dummy system were simulated and analyzed. The improvements of occupant survivability by different protective modules were compared using occupant injury criteria. The integral armored cab can maintain the integrity of the cab body structure. The add-on honeycomb sandwich armor reduces the peak structural deformation and velocity of the cab floor by 34.9% and 47.4%, respectively, compared with the cab with integral armors only. The integral armored cab with the anti-shock seat or the honeycomb sandwich structures reduces the occupant shock responses below the injury criteria. For different blast threat intensities, the selection of appropriate protective modules can meet protection requirements.
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Fatigue Evaluation of Multi-Degree of Freedom, Frequency Domain, Stochastic, Truck Road Load Models

SAE International Journal of Commercial Vehicles

TitanX Engine Cooling, USA-Karl Holmgren
  • Journal Article
  • 02-12-01-0006
Published 2019-02-11 by SAE International in United States
A number of semi-deterministic and stochastic formulations of multi-degree of freedom, frequency domain load models for heavy truck chassis are proposed and evaluated. The semi-deterministic models aim at reproducing the damage of a specific vehicle, while the stochastic ones aim to describe a collection of vehicle loads. The stochastic models are divided into two groups: Monte Carlo based and models based on single spectrum matrices. In both cases, the objective is to provide a load model that may be used to produce a design with a certain probability of survival. The goodness of the models is evaluated through a comparison of their damage outcomes with the corresponding damages of a set of time domain loads. This original time domain load set consists of chassis accelerations collected from seven physical trucks. Model parameters investigated included spectrum formulation (averaged vs damage equivalent spectra), polar vs rectangular formulation, and the effect of sorting of outcomes in the Monte Carlo models. For semi-deterministic load models, damage equivalent formulations performed well independent of number of load degrees of freedom, while…
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Onboard Natural Gas Reforming for Heavy Duty Vehicles

SAE International Journal of Commercial Vehicles

ExxonMobil Annuitant, USA-Walter Weissman
ExxonMobil Research and Engineering Company, USA-Brian Weiss, Tilman W. Beutel, Bryan R. Chapman, Jonathan D. Saathoff, Shamel Merchant, Gerardo J. Majano
  • Journal Article
  • 02-12-01-0004
Published 2019-01-07 by SAE International in United States
Powertrain simulations and catalyst studies showed the efficiency credits and feasibility of onboard reforming as a way to recover waste heat from heavy duty vehicles (HDVs) fueled by natural gas (NG). Onboard reforming involves 1) injecting NG into the exhaust gas recycle (EGR) loop of the HDV, 2) reforming NG on a catalyst in the EGR loop to hydrogen and carbon monoxide, and 3) combusting the reformed fuel in the engine. The reformed fuel has increased heating value (4-10% higher LHV) and flame speed over NG, allowing stable flames in spark ignition (SI) engines at EGR levels up to 25-30%. A sulfur-tolerant reforming catalyst was shown to reform a significant amount of NG (15-30% conversion) using amounts of precious metal near the current practice for HDV emissions control (10 g rhodium). Engine simulations showed that the high EGR levels enabled by onboard reforming are used most effectively to control engine load instead of waste-gating or throttling. This leads to 3% efficiency gain due to reduced pumping losses and enables the engine to run while the…
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Assessing Road Load Coefficients of a Semi-Trailer Combination Using a Mechanical Simulation Software with Calibration Corrections

SAE International Journal of Commercial Vehicles

University of Wyoming, USA-Milhan Moomen, Mahdi Rezapour, Amirarsalan Mehrara Molan, Khaled Ksaibati
  • Journal Article
  • 02-12-01-0003
Published 2019-01-07 by SAE International in United States
The study of road loads on trucks plays a major role in assessing the effect of heavy-vehicle design on fuel conservation measures. Coastdown testing with full-scale vehicles in the field offers a good avenue to extract drag components, provided that random instrumentation faults and biased environmental conditions do not introduce errors into the results. However, full-scale coastdown testing is expensive, and environmental biases which are ever-present are difficult to control in the results reduction. Procedures introduced to overcome the shortcomings of full-scale field testing, such as wind tunnels and computational fluid dynamics (CFD), though very reliable, mainly focus on estimating the effects of aerodynamic drag forces to the neglect of other road loads which should be considered. The development of mechanical simulation software in recent years suggests it is becoming much easier to incorporate the effects of other road load forces in drag analyses and fuel conservation measures. This study analyzed road loads obtained using a typical mechanical simulation software under calm and zero-wind conditions. The results were compared to drag coefficients derived from field…
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