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Surrogates for JP-8 have been developed in the high temperature gas phase environment of gas turbines. In diesel engines, the fuel is introduced in the liquid phase where volatility plays a major role in the formation of the combustible mixture and autoignition reactions that occur at relatively lower temperatures. In this paper, the role of volatility on the combustion of JP-8 and five different surrogate fuels was investigated in the constant volume combustion chamber of the Ignition Quality Tester (IQT). IQT is used to determine the derived cetane number (DCN) of diesel engine fuels according to ASTM D6890. The surrogate fuels were formulated such that their DCNs matched that of JP-8, but with different volatilities. Tests were conducted to investigate the effect of volatility on the autoignition and combustion characteristics of the surrogates using a detailed analysis of the rate of heat release immediately after the start of injection.

The study relates air/fuel ratio, fuel injection timing, and engine speed to exhaust smoke levels and performance of the diesel engine. Additional data were obtained under supercharged and turbocharged inlet air conditions to investigate the applicability of the derived relationships under these conditions. Limited data using a variance in fuel type were obtained. Insight into the basic mechanism of smoke formation in diesel engines was gained. The relative percentages of fuel injected before ignition (i.e., premixed fuel) and after initiation of combustion (i.e., unmixed diffusion burning fuel) were found to be extremely significant in determining smoke levels. A smoke factor (the ratio of equivalence ratio in the combustion chamber at initial ignition to overall equivalence ratio) was formulated and found to be useful in predicting smoke phenomena in diesel engines.

A quantitative and time-resolved technique has been developed to probe the dense spray structure of direct-injection (DI) gasoline sprays in near-nozzle region. This technique uses the line-of-sight absorption of monochromatic x-rays from a synchrotron source to measure the fuel mass with time resolution better than 1 μs. The small scattering cross-section of fuel at x-rays regime allows direct measurements of spray structure that are difficult with most visible-light optical techniques. Appropriate models were developed to determine the fuel density as a function of time.

This paper documents the successful operation of a modified Cummins T46 turbocharger with a ceramic rotor. This turbocharger is modified to incorporate a 4.6 inch diameter ceramic turbine rotor (pressureless sintered silicon nitride) on the hot end. These results document the most complete ceramic turbine rotor performance map, for a large ceramic turbocharger rotor, available to date.

For the application of advanced clean combustion technologies, such as diesel HCCI/LTC, a compressor with high efficiency over a broad operation range is required to supply a high amount of EGR with minimum pumping loss. A compressor with high pitch of vaneless diffuser would substantially improve the flow range of the compressor, but it is at the cost of compressor efficiency, especially at low mass flow area where most of the city driving cycles resides. In present study, an ultra low solidity compressor vane diffuser was numerically investigated. It is well known that the flow leaving the impeller is highly distorted, unsteady and turbulent, especially at relative low mass flow rate and near the shroud side of the compressor. A conventional vaned diffuser with high stagger angle could help to improve the performance of the compressor at low end. However, adding diffuser vane to a compressor typically restricts the flow range at high end.

Analysis of flow field and charge distribution in a gasoline direct-injection (GDI) engine is performed by a modified version of the KIVA code. A particle-based spray model is proposed to simulate a swirl-type hollow-cone spray in a GDI engine. Spray droplets are assumed to be fully atomized and introduced at the sheet breakup locations as determined by experimental correlations and energy conservation. The effects of the fuel injection parameters such as spray cone angle and ambient pressure are examined for different injectors and injection conditions. Results show reasonable agreement with the measurements for penetration, dispersion, global shape, droplet velocity and size distribution by Phase Doppler Particle Anemometry(PDPA) in a constant-volume chamber. The test engine is a 4-stroke 4-valve optically accessible single-cylinder engine with a pent-roof head and tumble ports.

Integrated control strategies for the O.P.E.R.A.S. (Optimization of injection Pressure, EGR ratio, injection Retard or Advance and Swirl ratio) are demonstrated. The strategies are based on an investigation of combustion and emissions in a small bore, high speed, direct injection diesel engine. The engine is equipped with a common rail injection system and is tested under simulated turbocharged engine conditions at two loads and speeds that represent two key operating points in a medium size HEV vehicle. A new phenomenological model is developed for the fuel distribution in the combustion chamber and the fractions that are injected prior to the development of the flame, injected in the flame or deposited on the walls. The investigation covered the effect of the different operating parameters on the fuel distribution, combustion and engine-out emissions.

By taking advantage of high-intensity and high-brilliance x-ray beams available at the Advanced Photon Source (APS), ultrafast (150 ps) propagation-based phase-enhanced imaging was developed to visualize high-pressure high-speed diesel sprays in the optically dense near-nozzle region. The sub-ns temporal and μm spatial resolution allows us to capture the morphology of the high-speed fuel sprays traveling at 500 m/s with a negligible motion blur. Both quality and quantitative information about the spray feature can be readily obtained. In the experiment, two types of single-hole nozzles have been used, one with a hydroground orifice inlet and the other with a sharp one. Within 3 mm from the nozzle, the sprays from these nozzles behave differently, ranging from laminar flow with surface instability waves to turbulent flow. The sprays are correlated with the nozzle internal geometry, which provides practical information for both nozzle design and supporting numerical simulation models.

This paper presents tribological modeling, experimental work, and validation of tribology parameters of a single cylinder turbocharged diesel engine run at various loads, speeds, intake boost pressures, and cylinder liner temperatures. Analysis were made on piston rings and liner materials, rings mechanical and thermal loads, contact pressure between rings and liner, and lubricant conditions. The engine tribology parameters were measured, and used to validate the engine tribology models. These tribology parameters are: oil film thickness, coefficient of friction between rings and liner, friction force, friction power, friction torque, shear rate, shear stress and wear of the sliding surfaces. In order to measure the oil film thickness between rings and liner, a single cylinder AVL turbocharged diesel engine was instrumented to accept the difference in voltage drop method between rings, oil film, and liner.

A long-distance microscope with pulse-laser as optical shutter up to 25kHz was used to magnify the diesel spray at the nozzle hole vicinity onto 35-mm photographic film through a still or a high-speed drum camera. The injectors examined are high-pressure valve-covered-orifice (VCO) nozzles, from unit injector and common rail injection systems. For comparison, a mini-sac injector from a hydraulic unit injector is also investigated. A phase-Doppler particle analyzer (PDPA) system with an external digital clock was also used to measure the droplet size, velocity and time of arrival relative to the start of the injection event. The visualization results provide very interesting and dynamic information on spray structure, showing spray angle variations, primary breakup processes, and spray asymmetry not observed using conventional macroscopic visualization techniques.

A high output experimental single cylinder diesel engine that was fully coated and insulated with a ceramic slurry coated combustion chamber was tested at full load and full speed. The cylinder liner and cylinder head mere constructed of 410 Series stainless steel and the top half of the articulated piston and the cylinder head top deck plate were made of titanium. The cylinder liner, head plate and the piston crown were coated with ceramic slurry coating. An adiabaticity of 35 percent was predicted for the insulated engine. The top ring reversal area on the cylinder liner was oil cooled. In spite of the high boost pressure ratio of 4:1, the pressure charged air was not aftercooled. No deterioration in engine volumetric efficiency was noted. At full load (260 psi BMEP) and 2600 rpm, the coolant heat rejection rate of 12 btu/hp.min. was achieved. The original engine build had coolant heat rejection of 18.3 btu/hp-min and exhaust energy heat rejection of 42.3 btu/hp-min at full load.

Low cetane JP-8 fuels have been identified as being difficult to use under conventional diesel operation. However, recent focus on low-temperature combustion (LTC) modes has led to an interest in distillate hydrocarbon fuels having high volatility and low autoignition tendency. An experimental study is performed to evaluate low-temperature combustion processes in a small-bore optically-accessible diesel engine operated in a partially-premixed combustion mode using low-cetane Sasol JP-8 fuel. This particular fuel has a cetane number of 25. Both single and dual injection strategies are tested. Since long ignition delay is a consequence of strong autoignition resistance, under the conditions examined, low cetane Sasol JP-8 combustion can only take place with a double injection strategy: one pilot injection event in the vicinity of exhaust TDC and one main injection event near firing TDC.

The nozzle configuration for an injector is known to have an important effect on the fuel atomization. A comprehensive experimental and numerical investigation has been performed to determine the influence of various internal geometries on the primary spray breakup and development using the electronically controlled high-pressure diesel injection systems. Different types of multi-hole minisac and VCO nozzles with cylindrical and tapered geometries, and different types of single-hole nozzles with defined grades of Hydro Grinding (HG) were investigated. The global characteristics of the spray, including spray angle, spray tip penetration and spray pattern were measured from the spray images with a high-speed drum camera. A long-distance microscope with a pulsed-laser as the optical shutter was used to magnify the diesel spray at the nozzle hole vicinity. A CFD analysis of the internal flow through various nozzle geometries has been carried out with a commercial code.

Advanced valvetrain coupled with Direct Injection (DI) provides an opportunity to simultaneous reduction of fuel consumption and emissions. Because of their robustness and cost performance, multi-hole injectors are being adopted as gasoline DI fuel injectors. Ethanol and ethanol-gasoline blends synergistically improve the performance of a turbo-charged DI gasoline engine, especially in down-sized, down-sped and variable-valvetrain engine architecture. This paper presents Mie-scattering spray imaging results taken with an Optical Accessible Engine (OAE). OAE offers dynamic and realistic in-cylinder charge motion with direct imaging capability, and the interaction with the ethanol spray with the intake air is studied. Two types of cams which are designed for Early Intake Valve Close (EIVC) and Later Intake Valve Close (LIVC) are tested, and the effect of variable valve profile and deactivation of one of the intake valves are discussed.

This paper investigates theoretically the benefits of the Miller cycle diesel engine with and without low heat rejection on thermodynamic efficiency, brake power, and fuel consumption. It further illustrates the effectiveness of thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model which includes a friction model is used to estimate the overall improvement in engine performance. Miller cycle is accomplished by closing the intake valve late and the engine components are coated with PSZ for low heat rejection. A significant improvement in brake power and thermal efficiency are observed.

The instantaneous frictional torque (IFT) of many components of a single cylinder diesel engine was determined by considering the forces acting on each component and the resulting change in the angular velocity. The IFT for the basic system, consisting of the crankshaft with the flywheel and oil pump, was first determined. The effect of adding each of the following to the basic system was determined: balancer shaft, cam shaft, piston with different ring combinations, inlet valve, exhaust valve and fuel injection pump. All the tests were conducted without gas pressure in the cylinder in a coast down mode. The results indicated the contribution of each component in the total frictional torque and its mode of lubrication. The energy absorbed by the valve springs and released back to the system was clearly Identified. The effect of speed on IFT and energy lost in friction was determined.

This paper deals with the analysis of heat release characteristics of an insulated turbocharged, six cylinder, DI contemporary diesel engine. The engine is fully insulated with thin thermal barrier coatings. Effect of insulation on the heat release was experimentally verified. Tests were carried over a range of engine speeds at 100%, 93%, 75% and 50% of rated torque. Fuel injection system was instrumented to obtain injection pressure characteristics. The study shows that rate of heat release, particularly in the major portion of the combustion, is higher for the insulated engine. Improvement in heat release and performance are primarily attributed to reduction in heat transfer loss due to the thin thermal barrier coating. Injection pressure at the rated speed and torque was found to be 138 MPa and there was no degradation of combustion process in the insulated engine. Improvements in BSFC at 93% load are 3.25% and 6% at 1600 and 2600 RPM, respectively.

Significant progress has been achieved in the development of advanced high-temperature, insulated, in-cylinder components for high-power-output miliraty diesel engines. Computer aided modeling and small-bore engine component testing have both been utilized extensively during the exploratory development process. Specific insulated optimal designs for the piston, cylinder headface, and cylinder liner have been identified. The designs all utilize thermal barrier coatings, titanium alloy, and interfacial air-gaps to provide thermal resistance. Finite element modeling including diesel cycle simulation has been utilized to screen and optimize material and design concepts relative to program objectives, while small-bore engine testing has been utilized to demonstrate component integrity. An improved slurry densified thermal barrier coating has been demonstrated by testing on a high temperature small-bore engine.

High-pressure fuel injection combustion is being applied as an approach to increase the power density of diesel engines. The high-pressure injection enables higher air utilization and thus improved smoke free low air-fuel ratio combustion is obtained. It also greatly increases the injection rate and reduces combustion duration that permits timing retard for lower peak cylinder pressure and improved emissions without a loss in fuel consumption. Optimization of these injection parameters offers increased power density opportunities. The lower air-fuel ratio is also conducive to simpler air-handling and lower pressure ratio turbocharger requirements. This paper includes laboratory data demonstrating a 26 percent increase in power density by optimizing these parameters with injection pressures to 200 mPa.

Development of in-cylinder spray targeting, plume penetration and atomization of the gasoline direct-injection (GDi) multi-hole injector is a critical component of combustion developments, especially in the context of the engine downsizing and turbo-charging trend that has been adopted in order to achieve the European target CO2, US CAFE, and concomitant stringent emissions standards. Significant R&D efforts are directed towards the optimization of injector nozzle designs in order to improve spray characteristics. Development of accurate predictive models is desired to understand the impact of nozzle design parameters as well as the underlying physical fluid dynamic mechanisms resulting in the injector spray characteristics. This publication reports Large Eddy Simulation (LES) analyses of GDi single-hole skew-angled nozzles, with β=30° skew (bend) angle and different nozzle geometries.