Joell Randolph Ii Hibshman

Correlation of Single-Cylinder to Multi-Cylinder Performance for a Medium Speed Diesel Engine

Single-cylinder research engines are valuable tools in the development of multi-cylinder reciprocating engines. The financial advantages of single-cylinder testing increases with engine size offering even larger benefits for medium-speed engines than light-duty automotive or heavy-duty truck engines. While testing on a single-cylinder engine provides a number of economic and technical advantages [1], careful planning and setup are required to maximize the usefulness of single-cylinder results as predictive of multi-cylinder performance. This paper describes the methodology used to set up and operate a single-cylinder medium speed diesel engine for combustion performance testing. An overview of the test cell design, infrastructure and instrumentation is provided, along with detailed specifications of the engine. There is good correlation between the single-cylinder and multi-cylinder performance when the gas-exchange-and frictional loss differences are taken into account. The strategy and results for this correlation effort are presented and discussed. The apparent rate of heat release was very consistent between the MCE and the SCE for the same load and injection timing. For other parameters, it was found that the single-cylinder engine contains biases relative to the absolute values observed from a full multi-cylinder engine, but the single-cylinder results are very useful in identifying relative performance trends and in performing in-cylinder optimization.Copyright

Experimental Study of Entrance Effects on Laminar Gas Flow Through Silicon Orifices

This study summarizes a fundamental investigation of flow through an array of silicon micromachined rectangular slots. The purpose of the study is to evaluate the effect of entrance pressure, flow area, orifice thickness, slot length, and slot width of the orifice on flow rate. These orifices were fabricated using a simple frontside through wafer DRIE process on a 385 μm thick wafer and wafer bonding to create thicker orifices. The dies were then packaged as part of a TO8 can and flow tested. To complement the results of this experimental work, two simple flow models were developed to predict the effect of geometrical and entrance conditions on the flow rate. These models were based on macroscale assumptions that were not necessarily true in the case of thin orifices. One relationship was based on Pouiselle flow which assumes fully developed flow conditions. Calculation of the entry length required for fully developed flow indicate that in the low Reynolds Number regime (32-550) evaluated, the entry flow development requires 2-8 times the thickness of the thickest orifices used for this study. Therefore, calculations of orifice flow based on a Pouiselle model are an overestimate of the actual measured flow rates. Another model examined typical orifice relationships using head loss at the entrance and exit of the slots did not accurately capture the particular flow rates since it overestimated the expansion or constriction losses. A series of experiments where the pressure was varied between 75 and 1000 Pa were performed. A comparison of the Pouiselle flow solution with experimental results was made which showed that the Pouiselle flow model overpredicts the flow rates and more specifically, the effect of width on the flow rates. The results of these tests were used to develop a transfer function which describes the dependence of flow rate on orifice width, thickness, length, and inlet pressure.Copyright