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European standards have set stringent PN (particle number) regulation (6×1011 #/km) for gasoline direct injection (GDI) engine, posing a great challenge for the particulate emission control of GDI engines. Dual-injection, which combines direct-injection (DI) with port-fuel-injection (PFI), is an effective approach to reduce particle emissions of GDI engine while maintaining good efficiency and power output. In order to investigate the PN emission characteristics under different dual-injection strategies, a DMS500 fast particle spectrometer was employed to characterize the effects of injection strategies on particulates emissions from a dual-injection gasoline engine. In this study, the injection strategies include injection timing, injection ratio and injection pressure of direct-injection.

Recently, all world countries facing the stringent emission regulations have been encouraged to explore the clean fuel. The diesel from indirect coal liquefaction (DICL) has been verified that can reduce the soot and NOx emissions of compression-ignition engine. However, the atomization characteristics of DICL are rarely studied. The aim of this work is to numerically analyze the inner nozzle flow and the atomization characteristics of the DICL and compare the global and local flow characteristics of the DICL with the NO.2 diesel (D2) at engine conditions. A surrogate fuel of the DICL (a mixture of 72.4% n-dodecane and 27.6% methylcyclohexane by mass) was built according to its components to simulate the atomization characteristics of the DICL under the high-temperature and high-pressure environment (non-reacting) by the Large Eddy Simulation (LES).

Stringent particulate emission regulations are applied to spark-ignition direct-injection (SIDI) engines, calling for a significant in-cylinder reduction of soot particles. To enhance fundamental knowledge of the soot formation and oxidation process inside the cylinder of the engine, a new in-flame particle sampling system has been developed and implemented in a working optical SIDI engine with a side-mounted, wall-guided injection system. Using the sampling probes installed on the piston top, the soot particles are directly sampled from the petrol flame for detailed analysis of particle size distribution, structure, and shape. At the probe tip, a transmission electron microscope (TEM) grid is stored for the soot collection via thermophoresis, which is imaged and post-processed for statistical analysis. Simultaneously, the flame development was recorded using two high-speed cameras to evidence the direct exposure of the sampling grids to the soot-laden diffusion flames and pool fires.

Nozzle length has been proven influencing fuel spray characteristics, and subsequently fuel-air mixing and combustion processes. However, almost all existing related studies are conducted when fuel is subcooled, of which fuel evaporation is extremely weak, especially at the near nozzle region. In addition, injector tip can be heated to very high temperature in SIDI engines, which would trigger flash boiling fuel spray. Therefore, in this study, effect of nozzle length on spray characteristics is investigated under superheated conditions. Three single-hole injectors with different nozzle length were studied. High speed backlit imaging technique was applied to acquire magnified near nozzle spray images based on an optical accessible constant volume chamber. Fuel pressure was maintained at 15 MPa, and n-hexane was chosen as test fuel.

The turbulent in-cylinder air flow and the unsteady high-pressure fuel injection lead to a highly transient air fuel mixing process in spark-ignition direct-injection (SIDI) engines, which is the leading cause for combustion cycle-to-cycle variation (CCV) and requires further investigation. In this study, crank-angle resolution particle image velocimetry (PIV) was employed to simultaneously measure the air flow and fuel spray structure at 1300 rpm in an optically accessible single-cylinder SIDI engine. The measurement was conducted at the center tumble plane of the four-valve pent-roof engine, bisecting the spark plug and fuel injector. 84 consecutive cycles were recorded for three engine conditions, i.e. (1) none-fueled motored condition, (2) homogeneous-charge mode with start of injection (SOI) during intake (50 crank-angle degree (CAD) after top dead center exhaust, aTDCexh), and (3) stratified-charge mode with SOI during mid compression (270 aTDCexh).

The electricity energy consumption for passenger cabin heating can drastically shorten the driving range for electric vehicles in cold climates. Mobile heat pump system is considered as an effective method to improve heating efficiency. This study investigates the system characteristics of mobile heat pump systems for electrical vehicle application. Based on KULI thermal management software, simulation models including HFC-R134a direct heat pump (DHP) and secondary loop heat pump (SLHP) were developed. The secondary loop employed in the SLHP includes a coolant pump, an indoor heater core and a plate heat exchanger, instead of an indoor condenser in the DHP. The use of a secondary loop has advantages to improve air outlet temperature uniformity. The simulation models were verified by measured data obtained from calorimeter experiments. By adopting simulation models, the effects of indoor and outdoor temperatures on system performance and cycle characteristics were discussed.

Biodiesel is a potential alternative fuel which can meet the growing need for sustainable energy. Partially premixed compression ignition (PPCI) is an important low-temperature combustion strategy to reduce NOx and soot emission of diesel engines. To investigate partial premixing impact on particle formation in flames of biodiesel or biodiesel surrogates, an experimental study was performed to compare the soot morphology and nanostructure evolution in laminar co-flow methyl decanoate non-premixed flame (NPF) and partially premixed flame (PPF). The thermophoretic sampling technique was used to capture particles along flame centerlines. Soot morphology information and volume fraction were obtained from TEM analysis and nanostructure features were evaluated by HR-TEM. With primary equivalence ratio of 19, gas temperature of PPF is higher along flame centerline compared with NPF. The results show an initially stronger sooting tendency in PPF at lower positions.

A novel normal measurement device for robotic drilling and countersinking has been developed. This device is mainly composed of three contact displacement sensors and a spherically compliant clamp pad. The compliance of the clamp pad allows it to be perpendicular to the part when the Multi-Function End Effector (MFEE) drives it to clamp the part surface prior to drilling, while the displacement sensors are used to measure the movement of the clamp pad relative to the MFEE. Once the sensors’ position is calibrated, the rotation angle of the clamp pad can be calculated by the displacement of the sensors. Then, the normal adjustment of MFEE is obtained, and the adjustment process can be achieved by the Rotation Tool Center Point (RTCP) function of robot. Thus, an innovative method based on laser tracker to identify the position of sensors is proposed.

The interaction of fuel sprays and in-cylinder flow in direct-injection engines is expected to alter kinetic energy and integral length scales at least during some portions of the engine cycle. High-speed particle image velocimetry was implemented in an optical four-valve, pent-roof spark-ignition direct-injection single-cylinder engine to quantify this effect. Non-firing motored engine tests were performed at 1300 RPM with and without fuel injection. Two fuel injection timings were investigated: injection in early intake stroke represents quasi-homogenous engine condition; and injection in mid compression stroke mimics the stratified combustion strategy. Two-dimensional crank angle resolved velocity fields were measured to examine the kinetic energy and integral length scale through critical portions of the engine cycle. Reynolds decomposition was applied on the obtained engine flow fields to extract the fluctuations as an indicator for the turbulent flow.

Manufacturing tolerances are inevitable in nature. For the bearings used in internal combustion engines, the manufacturing tolerances of roundness, which is of the micron scale, can be very close to the bearing radial clearance, and as a result the roundness could affect the lubrication of the bearings and thus affecting the friction loss of the engine. However, there is insufficient understanding of this mechanism. This study aims to find out the effects of the amplitude and the phase of journal roundness in the shape of ellipse on the lubrication of engine bearings. The elastohydrodynamic (EHD) theory is applied to model the bearing since the EHD model takes account of the elastic deformation of the journal and the bearing shell. The analysis of the DOE results shows the existence of roundness can be beneficial to the lubrication in some cases.

Combustion efficiency of internal combustion engine is closely influenced by the air flow pattern in the engine cylinder. Some researchers use high-speed particle image velocimetry to visualize and measure the temporally and spatially resolved in-cylinder velocity flow fields in the optically assessable engine. However, the transparent cylindrical liner makes it difficult to accurately determine the particle displacements inside the cylinder due to the optically distorted path of scattering light from seeding particles through the curved liner. To correct for the distortion-induced error in the seeding particle positions through the optical liner, the distortion mapping function is modeled using the Gaussian optics theory. Two artificial flow patterns with 5 by 5 vectors were made to illustrate the mapping correction. Distortion-induced error of velocity vectors was precisely mapped in six different planes inside the cylinder.

Conventionally, the engines are calibrated under the assumption that engines will be made exactly to the prints, and all the engines from the same batch will be identical. However, engine-to-engine variations do exist which will affect the engine performances, and part-to-part variations, i.e., the tolerance, is an important factor leading to engine-to-engine variations. There are researches conducted on the influence of dimensional tolerances on engine performance, however, the impact of straightness, which is an important geometric tolerance, on lubrication is an unsolved issue. This study presents a systematic method to model the straightness and to analyze its effects on the friction loss. The bearing model is built based on elastohydrodynamic (EHD) theory. Meanwhile a novel modeling method to represent any form of straightness in three-dimensional space is proposed.

Taking advantages of high speed RGB video cameras, the two-color method can be implemented with a relatively simple setup to obtain the temporal development of the two dimensional temperature and soot (KL) distributions in a reacting diesel jet. However, several issues such as the selection of the two wavelengths, the role of bandpass filters, and the proper optical settings, etc. should be known to obtain a reliable measurement. This paper, at first, discusses about the uncertainties in the measurement of temperature and KL distributions in the diesel flame by the two-color method using the high speed RGB video camera. Since n-butanol, as an alternative renewable fuel, has the potential application in diesel engines, the characteristic of spray combustion of diesel-butanol blends under the diesel-like ambient conditions in a pre-burning constant-volume combustion chamber is studied.

The diesel premixed low-temperature combustion mode avoids the generation of thick mixture and the high temperature region in which a great amount of NOx and PM generates. It makes a significant reduction in the emissions of both NOx and PM available at the same time. However, with the quantity of pre-injection increases and the injection time advances, the emission of HC increases significantly, which causes a decrease in the combustion efficiency. Studies have shown that the flame quench caused by too thick or too lean mixture and the oil film on the chamber is the main source for the emission of HC. As a result, understanding the mechanism of atomization and evaporation of the fuel and the formation of the mixture makes significant sense. This paper focuses on the mixture formation process. And the methods of testing the distribution of the mixture, the influential factors and control methods are studied.

The proper formation of fuel-air mixture, which depends to a large extend on the complex in-cylinder air flow, is an important criterion to control the clean and reliable combustion process in spark-ignition direct-injection (SIDI) engines. The in-cylinder flow vorticity field presents highly transient complex characteristics, and the corresponding vorticity field also evolves in the entire engine cycle from intake to exhaust strokes. It is also widely recognized that the vorticity field plays a key role in the in-cylinder turbulent field because it influences the air-fuel mixing and flame development process. In this investigation, the in-cylinder vortex structure and vorticity field characteristics are analyzed using the phase-invariant proper orthogonal decomposition (POD) method.

The improvement mechanism of fuel consumption at partial and full loads of a boosted direction-injection gasoline engine with the elevated geometrical compression ratio and Miller cycle by either early or late intake valve closing (EIVC or LIVC) are analyzed based on the first law of thermodynamics and one dimensional engine simulation. An increase in geometric compression ratio increases the theoretical thermal efficiency for all the operating loads, but deteriorates the fuel economy at full loads, owing primarily to the full-load knock limit. Use of Miller cycle improves the fuel economy for both the partial and full load operations by reducing the pumping loss and optimizing the combustion phasing, respectively. A comparison between EIVC and LIVC on the influencing factors on the thermal efficiency at the partial load shows that EIVC leads to higher mechanical efficiency and less heat transfer loss than LIVC, and hence its efficiency improvement is superior over LIVC.

This work investigates the suitability of n-butanol for enabling PCCI, HCCI, and RCCI combustion modes to achieve clean and efficient combustion on a high compression ratio (18.2:1) diesel engine. Systematic engine tests are conducted at low and medium engine loads (6∼8 bar IMEP) and at a medium engine speed of 1500 rpm. Test results indicate that n-butanol is more suitable than diesel to enable PCCI and HCCI combustion with the same engine hardware. However, the combustion phasing control for n-butanol is demanding due to the high combustion sensitivity to variations in engine operating conditions where engine safety concerns (e.g. excessive pressure rise rates) potentially arise. While EGR is the primary measure to control the combustion phasing of n-butanol HCCI, the timing control of n-butanol direct injection in PCCI provides an additional leverage to properly phase the n-butanol combustion.

Superheated spray is expected to improve the fuel atomization and evaporation processes by introducing fuel temperature as a new control parameter in spark-ignited direct-injection (SIDI) engines. In this study, flow fields of n-hexane spray from a multi-hole injector in both vertical and cross-sectional directions were investigated by using high-speed particle image velocimetry (HS-PIV) within the lower density regions. The results provide insight to the spray-collapsing processes under various superheated conditions. It was found that in axial direction, the vertical velocity increases while the radial velocity decreases with increasing superheat degree, which determines the convergent spray structure. In cross-sectional direction, the dynamic variation of the spray structure and interaction among spray plumes were investigated. The relationship between the spray structure and flow field was found. The flow patterns during and after the injection are significantly different.

Combustion and emission characteristics of diesel and biodiesel blends (soybean methyl ester) were studied in a single-cylinder Direct Injection (DI) engine at different loads and a constant speed. The results show that NOx emission and fuel consumption are increased with increasing biodiesel percentage. Reduction of smoke opacity is significant at higher loads with a higher biodiesel ratio. Compared with the baseline diesel fuel, B20 (20% biodiesel) has a slight increase of NOx emission and similar fuel consumption. Smoke emission of B20 is close to that of diesel fuel. Results of combustion analysis indicate that start of combustion (SOC) for biodiesel blends is earlier than that for diesel. Higher biodiesel percentage results in earlier SOC. Earlier SOC for biodiesel blends is due to advanced injection timing from higher density and bulk modulus and lower ignition delay from higher cetane number.

In this paper, the characteristics of performance and emissions of diesel and biodiesel blends are studied in a four-cylinder DI engine employing common rail injection system. The results show that engine output power is further reduced and brake specific fuel consumption (BSFC) increased with the increase of the blend concentration. B100 provides average reduction by 8.6% in power and increase by 11% in BSFC. With respect to the emissions, although NOx emissions were increased with increasing the blend concentration, the increase depends on the load. Filter smoke number is reduced with increasing the blend concentration. At the same time, NO, NO2 and other specific emissions are also investigated. In addition, difference of performance and emission between standard parameters of ECU and modified parameters of ECU is investigated for B10 and B20 based on same output power. The results show that NOx emission and FSN are still lower than baseline diesel.