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The study of spray-wall interaction is of great importance to understand the dynamics that occur during fuel impingement onto the chamber wall or piston surfaces in internal combustion engines. It is found that the maximum spreading length of an impinged droplet can provide a quantitative estimation of heat transfer and energy transformation for spray-wall interaction. Furthermore, it influences the air-fuel mixing and hydrocarbon and particle emissions at combusting conditions. In this paper, an analytical model of a single diesel droplet impinging on the wall with different inclined angles (α) is developed in terms of βm (dimensionless maximum spreading length, the ratio of maximum spreading length to initial droplet diameter) to understand the detailed impinging dynamic process.

The Reynolds stress turbulence model (RSM) has been developed to go beyond the Boussinesq hypothesis and to improve turbulence modeling of flows with significant mean streamline curvature and secondary flow. In this paper the RSM in commercial CFD software CONVERGE is tested for its performance and robustness when applying to complex flows. Several validation cases including flow over flat plate, vortex combustor, diesel engine spray and combustion were selected to test the RSM. The swirling flow in vortex combustor, non-reacting but vaporizing ECN Spray A (free jet) and Sandia small bore diesel engine case are used to demonstrate the benefits of the RSM over the widely used RNG k-epsilon model without model tuning. The vortex combustor case shows the RSM can provide good prediction for strong swirling flow. ECN spray A case was used to demonstrate that the RSM can accurately predict the liquid and vapor penetration lengths of a free jet under diesel engine conditions.

Time-averaged temperatures at critical locations on the piston of a direct-fuel injected, two-stroke, 388 cm3, research engine were measured using an infrared telemetry device. The piston temperatures were compared to data [7] of a carbureted version of the two-stroke engine, that was operated at comparable conditions. All temperatures were obtained at wide open throttle, and varying engine speeds (2000-4500 rpm, at 500 rpm intervals). The temperatures were measured in a configuration that allowed for axial heat flux to be determined through the piston. The heat flux was compared to carbureted data [8] obtained using measured piston temperatures as boundary conditions for a computer model, and solving for the heat flux. The direct-fuel-injected piston temperatures and heat fluxes were significantly higher than the carbureted piston. On the exhaust side of the piston, the direct-fuel injected piston temperatures ranged from 33-73 °C higher than the conventional carbureted piston.

The development of new high power diesel engines is continually going for increased mean effective pressures and consequently increased thermal loads on combustion chamber walls close to the limits of endurance. Therefore accurate CFD simulation of conjugate heat transfer on the walls becomes a very important part of the development. In this study the heat transfer and temperature on piston surface was studied using conjugate heat transfer model along with a variety of near wall treatments for turbulence. New wall functions that account for variable density were implemented and tested against standard wall functions and against the hybrid near wall treatment readily available in a CFD software Star-CD.

As the incentive to produce cleaner and more efficient engines increases, diesel engines will become a primary, worldwide solution. Producing diesel engines with higher efficiency and lower emissions requires a fundamental understanding of the interaction of the injected fuel with air as well as with the surfaces inside the combustion chamber. One aspect of this interaction is spray impingement on the piston surface. Impingement on the piston can lead to decreased combustion efficiency, higher emissions, and piston damage due to thermal loading. Modern high-speed diesel engines utilize high pressure common-rail direct-injection systems to primarily improve efficiency and reduce emissions. However, the high injection pressures of these systems increase the likelihood that the injected fuel will impinge on the surface of the piston.

A novel two-stroke engine concept is introduced. The cylinder scavenging takes place during the upward motion of the piston. The gas exchange valves are similar to typical four-stroke valves, but the intake valves are smaller and lighter. The scavenging air pressure is remarkably higher than in present-day engines. The high scavenging air pressure is produced by an external compressor. The two-stroke operation is achieved without the drawbacks of port scavenged engines. Moreover, the combustion circumstances, charge pressure and temperature and internal exhaust gas re-circulation (EGR) can be controlled by using valve timings. There is good potential for a substantial reduction in NOx emissions through the use of adjustable compression pressure and temperature and by using the adjustable amount of exhaust gas re-circulation.

The necessity to study spray-wall interaction in internal combustion engines is driven by the evidence that fuel sprays impinge on chamber and piston surfaces resulting in the formation of wall films. This, in turn, may influence the air-fuel mixing and increase the hydrocarbon and particulate matter emissions. This work reports an experimental and numerical study on spray-wall impingement and liquid film formation in a constant volume combustion vessel. Diesel and n-heptane were selected as test fuels and injected from a side-mounted single-hole diesel injector at injection pressures of 120, 150, and 180 MPa on a flat transparent window. Ambient and plate temperatures were set at 423 K, the fuel temperature at 363 K, and the ambient densities at 14.8, 22.8, and 30 kg/m3. Simultaneous Mie scattering and schlieren imaging were carried out in the experiment to perform a visual tracking of the spray-wall interaction process from different perspectives.

The present work aims to determine the gas pressure acting in the ring pack area in a medium-speed four stroke diesel engine. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, with telemetric data transmission, and an instrumented cylinder liner in a 6-cylinder test engine. The results, in terms of inter-ring gas pressure are compared with the results of computer simulations. Moreover, the computer simulations were carried out to predict and compare the effects of the piston running clearance and the ring face wear on the inter-ring pressures. The study comprises aspects on inter-ring pressures under a set of loads. The measured inter-ring gas pressures indicate steady ring operation. The simulation results show good agreement with measurement results.

The objective of this investigation was to identify the impingement event on a diesel piston surface. Eight fast-response, surface thermocouples were installed in one of the pistons of a 2.0 liter, four-cylinder, turbo-charged diesel engine (97 kW @ 3800 rpm). Piston temperatures were transmitted from the engine using wireless microwave telemetry. An impingement signal was identified on the piston bowl lip. A simple parameter for characterizing the impingement event is proposed. The results show an impingement signature at one of the bowl lip thermocouples, under specific operating conditions.

The development of diesel engines is constantly leading to greater increases in the power density. The heat load into the combustion chamber walls increases with the increased power density. Estimating correct local heat fluxes inside the combustion chamber is one of the most challenging tasks in engine simulation. In this study, the heat load of the piston was estimated with the help of the modern simulation tools CFD and FEM. The objective of the work was to evaluate the thermal stress of a research engine designed for an exceptionally high maximum and mean pressure. The local heat transfer coefficient and gas temperature were simulated with a CFD code with the standard and modified wall functions and used as boundary values for the FEM analysis. As a reference case, a model of a production engine with measured piston surface temperatures was used to validate the combined CFD and FEM analysis.

A study has been made of piston ring wear and total engine wear using literature data and new experimental results. The main purpose of the study was to establish the effects of oil and coolant temperatures on engine wear. Wear trends that were found in the early 1960's may not be valid any longer because of the development of higher BMEP turbocharged diesel engines, better metallurgical wear surfaces and improved lube oil properties. New data are presented for the purpose of describing present wear trends. A direct-injection, 4-cycle, turbocharged diesel engine was used for the wear tests. The radioactive tracer technique was used to measure the top piston ring chrome face wear. Atomic emission spectroscopy was employed to determine the concentration of wear metals in the oil to determine total engine wear based on iron and lead. The data were analyzed and compared to the results found in the literature from previous investigators.

Fuel spray interactions with piston surfaces and cylinder walls in internal combustion engines have been extensively studied in the past decades. However, there still exists an imperative knowledge gap on the fundamental understanding of dynamic droplet-wall interactions. Particularly, the impinging angle of droplet has been barely investigated as it renders asymmetrical droplet behaviors. This paper aims to provide detailed data of droplet-inclined surface impingement physics which could further support spray-wall model development. The experimental work of single diesel droplet impinging on an inclined dry surface was conducted under isothermal (25°C) conditions. Various droplet impact angle (φ) was achieved by adjusting surface tilting angle which was set from 0° to 45° in current study. A single diesel droplet impinged onto the inclined surface with different Weber number (around 20 ~ 800).

Under low-temperature combustion for the high fuel efficiency and low emissions achievement, the fuel impingement often occurs in diesel engines with direct injection especially for a short distance between the injector and piston head/cylinder wall. Spray impingement plays an important role in the mixing-controlled combustion phase since it affects the air-fuel mixing rate through the disrupted event by the impingement. However, the degree of air entrainment into the spray is hard to be directly evaluated. Since the high spray expansion rate could allow more opportunity for fuel to mix with air, in this study, the expansion rate of impinged flame is quantified and compared with the spray expansion rate under non-vaporizing conditions. The experiments were conducted in a constant volume combustion chamber with an ambient density of 22.8 kg/m3 and the injection pressure of 150 MPa.

Fuel spray-wall interaction frequently occurs on intake manifold wall in the port fuel injection engine and on the piston in the direct injection engine, especially during the cold start. The heat transfer between the spray and wall is involved in this interaction process and influences the dynamics of the impinged spray which can further affect the engine performance. The physics of impact dynamics of a single droplet serves as a fundamental for better comprehension of spray impingement. In our previous studies, we have focused on diesel droplets, at ambient temperature, impinging on both heated and non-heated wall and found impinged droplet morphology differences. To understand the effect of heat transfer and thermophysical properties on dynamics of droplet-wall interaction better, droplet temperature variation was introduced in this study. Therefore, different conditions were framed to explore the impact of thermophysical properties of the droplet.

The aim of this paper is to computationally investigate the combustion behavior and energy recovery processes of a six-stroke gasoline compression ignition (6S-GCI) engine that employs a continuously variable valve duration (CVVD) technique, under highly diluted, low-temperature combustion (LTC) conditions. The effects of variation of parameters concerning injection spray targeting (number of fuel injector holes. injector nozzle size and spray included angle) and combustion chamber geometry (piston bowl design) are analyzed using an in-house 3D CFD code coupled with high-fidelity physical sub-models with the Chemkin library in conjunction with a skeletal chemical kinetics mechanism for a 14-component gasoline surrogate fuel.

The fuel spray impingement on the piston head and/or chamber often occurs in compact IC engines. The impingement plays one of the key roles in combustion because it affects the air-fuel mixing process. In this study, the impinged combustion has been experimentally investigated to understand the mechanism and dynamics of flame-wall interaction. The experiments were performed in a constant volume combustion chamber over a wide range of ambient conditions. The ambient temperature was varied from 800 K to 1000 K and ambient gas oxygen was varied from 15% to 21%. Diesel fuel was injected with an injection pressure of 150 MPa into ambient gas at a density of 22.8 kg/m3. The natural luminosity technique was applied in the experiments to explore the impinged combustion process. High-speed images were taken using a high-speed camera from two different views (bottom and side). An in-house Matlab program was used to post-process the images.

A computational fluid dynamics (CFD) guided combustion system optimization was conducted for a heavy-duty diesel engine running with a gasoline fuel that has a research octane number (RON) of 80. The goal was to optimize the gasoline compression ignition (GCI) combustion recipe (piston bowl geometry, injector spray pattern, in-cylinder swirl motion, and thermal boundary conditions) for improved fuel efficiency while maintaining engine-out NOx within a 1-1.5 g/kW-hr window. The numerical model was developed using the multi-dimensional CFD software CONVERGE. A two-stage design of experiments (DoE) approach was employed with the first stage focusing on the piston bowl shape optimization and the second addressing refinement of the combustion recipe. For optimizing the piston bowl geometry, a software tool, CAESES, was utilized to automatically perturb key bowl design parameters. This led to the generation of 256 combustion chamber designs evaluated at several engine operating conditions.