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Regulated emissions (THC, CO, NOx, and PM) and particulate SOF and sulfate fractions were determined for a 1995 Detroit Diesel Series 50 urban bus engine at varying fuel sulfur levels, with and without catalytic converters. When tested on EPA certification fuel without an oxidation catalyst this engine does not appear to meet the 1994 emissions standards for heavy duty trucks, when operating at high altitude. An ultra-low (5 ppm) sulfur diesel base stock with 23% aromatics and 42.4 cetane number was used to examine the effect of fuel sulfur. Sulfur was adjusted above the 5 ppm level to 50, 100, 200, 315 and 500 ppm using tert-butyl disulfide. Current EPA regulations limit the sulfur content to 500 ppm for on highway fuel. A low Pt diesel oxidation catalyst (DOC) was tested with all fuels and a high Pt diesel oxidation catalyst was tested with the 5 and 50 ppm sulfur fuels.

Efficient and accurate ordinary differential equation (ODE) solvers are necessary for powertrain and vehicle dynamics modeling. However, current commercial ODE solvers can be financially prohibitive, leading to a need for accessible, effective, open-source ODE solvers designed for powertrain modeling. Rust is a compiled programming language that has the potential to be used for fast and easy-to-use powertrain models, given its exceptional computational performance, robust package ecosystem, and short time required for modelers to become proficient. However, of the three commonly used (>3,000 downloads) packages in Rust with ODE solver capabilities, only one has more than four numerical methods implemented, and none are designed specifically for modeling physical systems. Therefore, the goal of the Differential Equation System Solver (DESS) was to implement accurate ODE solvers in Rust designed for the component-based problems often seen in powertrain modeling.

We have designed and tested a prototype dish/Stirling hybrid-receiver combustion system. The system consists of a pre-mixed natural-gas burner heating a pin-finned sodium heat pipe. The design emphasizes simplicity, low cost, and ruggedness. Our test was on a 1/6th-scale device, with a nominal firing rate of 18kWt, a power throughput of 13kWt, and a sodium vapor temperature of 750°C. The air/fuel mixture was electrically preheated to 640°C to simulate recuperation. The test rig was instrumented for temperatures, pressures, flow rates, overall leak rate, and exhaust emissions. The data verify our burner and heat-transfer models. Performance and post-test examinations validate our choice of materials and fabrication methods. Based on the 1/6th -scale results, we are designing a full-scale hybrid receiver.