Raymond L. Speth

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In September 2015, the Volkswagen Group (VW) admitted the use of ‘defeat devices’ designed to lower emissions measured during VW vehicle testing for regulatory purposes. Globally, 11 million cars sold between 2008 and 2015 are affected, including about 2.6 million in Germany. On-road emissions tests have yielded mean on-road NOx emissions for these cars of(More)
A recent experiment showed that cylindrical segments of water filling a hydrophilic stripe on an otherwise hydrophobic surface display a capillary instability when their volume is increased beyond the critical volume at which their apparent contact angle on the surface reaches 90 (Gau et al 1999 Science 283 46–9). Surprisingly, the fluid segments did not(More)
We quantify the economic and environmental benefits of designing U.S. light-duty vehicles (LDVs) to attain higher fuel economy by utilizing higher octane (98 RON) gasoline. We use engine simulations, a review of experimental data, and drive cycle simulations to estimate the reduction in fuel consumption associated with using higher-RON gasoline in(More)
In this paper, we experimentally investigate the combustion dynamics in lean premixed flames in a laboratory scale backward-facing step combustor in which flame-vortex driven dynamics are observed. A series of tests was conducted using propane/hydrogen/air mixtures for various mixture compositions at the inlet temperature ranging from 300 K to 500 K and at(More)
This paper presents an experimental investigation into mode-transitions observed in a 50-kW, atmospheric pressure, backward-facing step combustor burning lean premixed C3H8/H2 fuel mixtures over a range of equivalence ratios, fuel compositions and preheat temperatures. The combustor exhibits distinct acoustic response and dynamic flame shape (collectively(More)
Many systems of equations fit naturally in the form du/dt = A(u) + B(u). We may separate convection from diffusion, x-derivatives from y-derivatives, and (especially) linear from nonlinear. We alternate between integrating operators for dv/dt = A(v) and dw/dt = B(w). Noncommutativity (in the simplest case, of eAh and eBh) introduces a splitting error which(More)
This paper presents an experimental investigation into mode-transitions observed in a 50-kW, atmospheric pressure, backward-facing step combustor burning lean premixed C3H8/H2 fuel mixtures over a range of equivalence ratios, fuel compositions and preheat temperatures. The combustor exhibits distinct acoustic response and dynamic flame shape (collectively(More)
TheUSEnvironmental ProtectionAgency (EPA)has alleged that VolkswagenGroup of America (VW) violated theCleanAir Act (CAA) by developing and installing emissions control system ‘defeat devices’ (software) inmodel year 2009–2015 vehicles with 2.0 litre diesel engines. VWhas admitted the inclusion of defeat devices. On-road emissions testing suggests that(More)
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