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The objective of this research is a detailed investigation of unburned hydrocarbon (UHC) in a highly-dilute diesel low temperature combustion (LTC) regime. This research concentrates on understanding the mechanisms that control the formation of UHC via experiments and simulations in a 0.48L signal-cylinder light duty engine operating at 2000 r/min and 5.5 bar IMEP with multiple injections. A multi-gas FTIR along with other gas and smoke emissions instruments are used to measure exhaust UHC species and other emissions. Controlled experiments in the single-cylinder engine are then combined with three computational tools, namely heat release analysis of measured cylinder pressure, analysis of spray trajectory with a phenomenological spray model using in-cylinder thermodynamics [1], and KIVA-3V Chemkin CFD computations recently tested at LTC conditions [2].

A detailed comparison of cylinder pressure derived combustion performance and engine-out emissions is made between an all-metal single-cylinder light-duty diesel engine and a geometrically equivalent engine designed for optical accessibility. The metal and optically accessible single-cylinder engines have the same nominal geometry, including cylinder head, piston bowl shape and valve cutouts, bore, stroke, valve lift profiles, and fuel injection system. The bulk gas thermodynamic state near TDC and load of the two engines are closely matched by adjusting the optical engine intake mass flow and composition, intake temperature, and fueling rate for a highly dilute, low temperature combustion (LTC) operating condition with an intake O2 concentration of 9%. Subsequent start of injection (SOI) sweeps compare the emissions trends of UHC, CO, NOx, and soot, as well as ignition delay and fuel consumption.

A single cylinder CFR research engine has been run in HCCI combustion mode at the rich and the lean limits of the homogeneous charge operating range. To achieve a variation of the degree of charge stratification, two GDI injectors were installed: one was used for generating a homogeneous mixture in the intake system, and the other was mounted directly into the side of the combustion chamber. At the lean limit of the operating range, stratification showed a tremendous improvement in IMEP and emissions. At the rich limit, however, the stratification was limited by the high-pressure rise rate and high CO and NOx emissions. In this experiment the location of the DI injector was in such a position that the operating range that could be investigated was limited due to liquid fuel impingement onto the piston and liner.

A modification of the computational fluid dynamics code KIVA-II is presented that allows computations to be made in complex engine geometries. An example application is given in which three versions of KIVA-II are run simultaneously. Each version considers a separate block of the computational domain, and the blocks exchange boundary condition information with each other at their common interfaces. The use of separate blocks permits the connectedness of the overall computational domain to change with time. The scavenging flow in the cylinder, transfer pipes (ports), and exhaust pipe of a ported two-stroke engine with a moving piston was modeled in this way. Results are presented for three engine designs that differ only in the angle of their boost ports. The calculated flow fields and the resulting fuel distributions are shown to be markedly different with the different geometries.

A detailed thermodynamic analysis was performed to demonstrate the fundamental efficiency advantage of an opposed-piston two-stroke engine over a standard four-stroke engine. Three engine configurations were considered: a baseline six-cylinder four-stroke engine, a hypothetical three-cylinder opposed-piston four-stroke engine, and a three-cylinder opposed-piston two-stroke engine. The bore and stroke per piston were held constant for all engine configurations to minimize any potential differences in friction. The closed-cycle performance of the engine configurations were compared using a custom analysis tool that allowed the sources of thermal efficiency differences to be identified and quantified.

The objective of this research is a detailed investigation of particulate sizing and number count from a spark-ignited, direct-injection (SIDI) engine at different operating conditions. The engine is a 549 [cc] single-cylinder, four-valve engine with a flat-top piston, fueled by Tier II EEE. A baseline engine operating condition, with a low number of particulates, was established and repeatability at this condition was ascertained. This baseline condition is specified as 2000 rpm, 320 kPa IMEP, 280 [°bTDC] end of injection (EOI), and 25 [°bTDC] ignition timing. The particle size distributions were recorded for particle sizes between 7 and 289 [nm]. The baseline particle size distribution was relatively flat, around 1E6 [dN/dlogDp], for particle diameters between 7 and 100 [nm], before dropping off to decreasing numbers at larger diameters. Distributions resulting from a matrix of different engine conditions were recorded.

A 2.4L commercial diesel engine was developed for light-duty commercial and off-road applications such as skid-loader, forklift and construction equipments. This engine complies with US Tier 4-final regulation, without PM after-treatment device by virtue of improved combustion strategy which is named as ULPC (Ultra-Low Particulate Combustion). This paper explains how ULPC works to reduce particulate matter (PM) based on the optimization of combustion system - piston bowl and nozzle specification. A baseline, re-entrant shape piston bowl, is useful to improve mixing of fuel and air in the main combustion chamber due to squish jet flow, especially in high-speed diesel engines. However, operating speed of commercial engines is almost half slower than that of passenger car engines and the merits by squish flow become deteriorated.

This paper shows development challenges for 6 liter heavy duty off-road diesel engines to meet the Tier4 final emission regulations with a base diesel engine compliant with Tier4 interim emission regulations. Even if an after-treatment system helps to reduce emissions, quite amount of particulate matters (PM) reduction is still necessary since a diesel particulate filter (DPF) system is supposed to be excluded in Tier4 final diesel engine. The objective of this research is to see if the base engine has a feasibility to meet Tier4 final emission regulations by a change of piston bowl geometry without DPF. Quite amount of PM can be reduced by piston bowl geometry because piston bowl geometry is a very important part that enhances air and fuel mixing process that help the combustion process.

As presented in the previous study [1], a 2.4L ULPC(Ultra Low PM Combustion) diesel engine was achieved through optimal matching with piston bowl geometry and nozzle spray angle that significantly reduce the amount of engine out soot generated in the combustion. This engine complies with US Tier 4 Final regulation without DPF (only DOC) which was developed for off-road applications such as skid-loader, forklift and construction equipment. Improvement in fuel consumption of diesel engine for off-road applications and construction equipment which are operating continuously for a long time at high load conditions will be very important for reducing the operating costs. This paper explains a detailed review of improvement BSFC of 2.4L ULPC diesel engine by optimizing the combustion system with swirl ratio, nozzle flow rate and piston bowl geometry while maintaining non-DPF solution.