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It was important for predicting wall heat flux to apply wall heat transfer model by taking into account of the behavior of turbulent kinetic energy and density change in wall boundary layer. Although energy equation base wall heat transfer model satisfied above requirements, local physical amounts such as turbulent kinetic energy in near wall region should be applied. In this study, in order to predict wall heat transfer by zero dimensional analysis, how to express wall heat transfer by using mean physical amounts in engine combustion chamber was considered by experimental and numerical approaches.

Simplified visualization of the fuel spray developing process in a small D.I. diesel engine was made by the liquid injection technique. In this technique, a liquid fuel was injected into another liquid to simulate injection into a high pressure gaseous atmosphere. For obtaining spray characteristics in the liquid similar to a diesel spray in a high-pressure gaseous atmosphere, the similarity principles based on the Reynolds number of the fuel flow at a nozzle hole and empirical equations of the spray penetration including the breakup length were introduced in this study. Especially, the injector was newly designed for the liquid injection technique based on these similarity principles. The behavior of the spray in a swirling flow was investigated. The spray with different breakup length shows different behavior in the same swirling flow.

Some experimental investigations have shown that the trade-off curve of NOx vs. particulate of a D.I. diesel engine with split-injection strategies can be shifted closer to the origin than those with a single-pulse injection, thus reducing both particulate and NOx emissions significantly. It is clear that the injection mass ratios and the dwell(s) between injection pulses have significant effects on the combustion and emissions formation processes in the D.I. diesel engine. However, how and why these parameters significantly affect the engine performances remains unexplained. The effects of both injection mass ratios and dwell between injections on vapor/liquid distributions in the split-injection diesel sprays impinging on a flat wall have been examined in our previous work.

TWC exposure to extreme temperature could result in irreversible damage or thermal failure. Thus, a strategy embedded in the engine control unit (ECU) called catalyst overheating protection (COP) will be activated to prevent TWC overheating. When COP is activated, the command air-fuel ratio will be enriched to cool the catalyst monolith down. Fuel enrichment has been proven a main prerequisite for ammonia formation in hot TWCs as a by-product of NOx reduction. Hence, COP events could theoretically be a source of post-catalyst ammonia from petrol vehicles, but this theory is yet to be confirmed in published literature. This paper validated this hypothesis using a self-programmed chassis-level test. The speed of the test vehicle was set to constant while the TWC temperature was raised stepwise until a COP event was activated.

An experimental study was made of the two-dimensional distributions of the fuel vapor concentration simulated by Freon-12 in the combustion chamber of a SI engine. Laser Rayleigh scattering was applied for this remote, nonintrusive and highly space- and time-resolved measurement. The original engine was modified to introduce YAG laser-induced sheet light into the combustion chamber and the scattered light was captured by a CCD camera fitted with a gated double-microchannel plate image intensifier. The results showed that the fuel vapor concentration was highly heterogeneous during the intake stroke and the inhomogeneity decreased in the compression stroke. But, even at the end of the compression stroke, a number of small lumps of inhomogeneous mixture still existed randomly in the engine combustion chamber, which is assumed to cause the heterogeneity of the mixture strength field at the spark discharge.

An experimental study on emission formation processes, such as these of nitric oxide, particulate and total hydrocarbon in a small direct injection (D.I.) diesel engine was carried out by using a newly developed total in-cylinder sampling technique. The sampling method consisted of rapidly opening a blowdown valve attached to the bottom of the piston bowl, and quickly transferring most of the in-cylinder contents into a large sampling chamber below the piston. No modification of the intake and exhaust ports in a cylinder head was required for the installation of the blowdown apparatus. The sampling experiment gave a history of spatially-averaged emission concentrations in the cylinder. The effects of several engine variables, such as the length-to-diameter ratio of the nozzle hole, the ratio of the piston bowl diameter to the cylinder bore and the intake swirl ratio, on the emission formation processes were investigated.

Experiments and modeling of a spray impinged onto a cavity wall of a simulated piston were performed under simulated diesel engine conditions (pressure and density) at an ambient temperature. The diesel fuel was delivered from a Bosch-type injection pump to a single-hole nozzle, the hole being drilled in the same direction as the original five-hole nozzle. The fuel was injected into a high-pressure bomb in which an engine combustion chamber, composed of a piston, a cylinder head and a cylinder liner, was installed. Distributions of the spray impinged on the simulated combustion chamber were observed from various directions while changing some of the experimental parameters, such as combustion chamber shape, nozzle projection and top-clearance. High-speed photography was used in the constant volume bomb to examine the effect of these parameters on the spray distributions.

In this paper, a new method for the driving of the hydraulic free piston engine (HFPE) is proposed. Hydraulic differential drive achieves the compression stroke automatically rather than special recovery system, which has a great influence on the engine dynamic performance. The purpose of this paper is to solve the key operation and control problems for HFPE to commix fuel with air. HFPE adopts two-stroke loop-scavenging and semi-direct injection. The semi-direct injection nozzle is located in the liner wall inside the main intake port, with the axes oriented towards the piston at the Bottom Dead Center (BDC). Different scavenging pressures and injection angles result in different impacts on the mixture of fuel and air in the cylinder. This study analyzes the changes of the combustion heat release rate by simulation.

A new concept of “synthetic performance coefficient of inlet port” in D.I. diesel engines has been proposed from a viewpoint of efficiency of energy conversion in this paper. It makes the performance of various kinds of inlet ports in D.I. diesel engines compared with each other. Based on the regression analysis of the experimental results, it is found that the synthetic performance coefficient of inlet port has a close linear relation to the engine performance, and it can be used as a criterion to optimize the design of inlet port in D.I. diesel engines.

Due to the latent heat of vaporization, the efficiency of boiling heat transfer is several times and even dozens of times higher than that of the convection heat transfer. With the improvement of power density of the engine, there are more requirements for engine cooling system design. It has been confirmed that the subcooled boiling did exist in the engine cooling. If boiling heat transfer can be reasonablely used, we can achieve the objective of enhancing heat transfer without changing the existing structure. In this paper, in order to quantitatively research the subcooled boiling in the engine, we simulated the subcooled boiling in the analog channel with the Euler multiphase model, found the importance of the turbulent dispersion. In additon, we explored the applicability of existing models to subcooled boiling, and compared the results with the experiment.

Taking a specific diesel engine as a calculation example, three kinds of ptimized calculation methods are studied in detail for the optimization of the performance of Diesel Engine cycle and the following conclusions are drawn: Sequential Linear Programming (S.L.P) suits for the rough optimized calculation of the performance of Diesel Engine cycle. Sequential Unconstrained Minimization Technique (S.U.M.T) suits for the precise optimized calculation of the performance of Diesel Engine cycle with less variables. Orthognal Network Optimization Method (O.N.O.M) has a wide adaptability, but calculating time is longer, it suits for the precise optimized calculation of the performance of Diesel Engine cycle with more variables.

The starting knock of R4102 D.I. diesel engine are analyzed experimentally based on the transient speed and first and third cylinder indicator diagrams that were taken from updated data acquisition system developed by the authors[1][2]. The influence of the starting knock on the strength of connecting rod, piston and piston ring are also studied. The results show that the influence of the starting knock is larger than the influence of the rated conditions. So the starting knock must be thought in the engine design.

The combustion of cylinder lubricating oil (called as cylinder oil for short) is one of the major sources of PM emissions of low-speed 2-stroke marine diesel engines. For pre-mixed combustion low-speed 2-stroke marine gas engines, the auto-ignition of cylinder oil might result in knock or more hazard abnormal combustion - pre-ignition. Evaporation is a key sub-process of the auto-ignition process of cylinder oil droplets. The evaporation behavior has a profound impact on the auto-ignition and combustion processes of cylinder oil droplets, and a great influence on engine combustion performance and emission characteristics. This paper applied an oil suspending apparatus to investigate the evaporation behavior of cylinder oil droplets and base oil droplets. The effects of ambient temperatures on the evaporation process were measured and analyzed. The results indicate that the evaporation of cylinder oil includes heating, evaporating, pyrolysis, and polymerization.

Droplets impacting onto the heated surface is a typical phenomenon either in CI engines or in GDI SI engines, which is regarded significant for their air-fuel mixing. Meanwhile, alcohols including ethanol and butanol, has been widely studied as internal combustion engine alternative fuels due to their excellent properties. In this paper, under different component ratio conditions, the ethanol-butanol droplet impacting onto the heated aluminum surface has been studied experimentally. The falling height of the droplets were set at 5cm. A high-speed camera, set at 512×512pixels, 5000 fps and 20 μs of exposure time, was used to visualize the droplet behavior impinging onto the hot aluminum surface. The impact regimes of the binary droplet were identified. The result showed that the Leidenfrost temperature of droplets was affected by the ratio of ethanol to butanol. The higher the content of butanol in the droplet, the higher the Leidenfrost temperature.

The new shape ceria-based support material for a lean NOx trap catalyst (LNT) was developed and its catalytic characteristics were investigated. It has a unique shape that each fine particle of raw material is formed into hollow sphere. Samples of platinum loaded powder catalysts were obtained with either the hollow sphere ceria-based material or two kinds of the conventional shape one, and their catalytic activities were evaluated with the synthetic gas. The aged powder catalyst using the hollow sphere ceria-based material had higher CO oxidation performance at low temperature as compared to the conventional shape one with the same composition. The characterization results indicated that the hollow sphere ceria-based material had high thermal stability.

A study was performed on a lean NOx trap in which the loading of a ceria-containing mixed oxide in the washcoat was varied. After a mild stabilization of the traps, the time required to purge the NOx trap generally increased with increasing amount of mixed oxide. The purge NOx release also increased with increasing mixed oxide level but was greatly diminished after thermal aging. The sulfur tolerance of the NOx trap improved as the mixed oxide content was increased from 0% to 37%. The sample with 0% mixed oxide was more difficult to desulfate than the other samples due to poor water-gas-shift capability. After thermal aging, the NOx reduction efficiency on a 60 second lean/5 second rich cycle was highest for the samples with 0% to 37% mixed oxide at evaluation temperatures of 400°C to 500°C.

Urea SCR technology is the most promising technique to reduce NOx emissions from heavy duty diesel engines. 32.5wt% aqueous urea solution is widely used as ammonia storage species for the urea SCR process. The thermolysis and hydrolysis of urea produces reducing agent ammonia and reduces NOx emissions to nitrogen and water. However, the application of urea SCR technology has many challenges at low temperature conditions, such as deposits formation in the exhaust pipe, lack deNOx performance at low temperature and freezing below -12°C. For preventing deposits formation, aqueous urea solution is hardly injected into exhaust gas stream at temperature below 200°C. The aqueous urea solution used as reducing agent precursor is the main obstacle for achieving high deNOx performances at low temperature conditions. This paper presents a solid SCR technology for control NOx emissions from heavy duty diesel engines.

This paper describes the application of Human Simulation Intelligent Control(HSIC) method to improve the idle speed performance of heavy-duty diesel engines on the basis of diesel engine electronic control system. The HSIC is a kind of intelligent control method which can be used without knowing the system's model and it can on line choose control models and it is also easy to be used under the condition of diesel engine electronic control system. In our system, we used electronic control system to control fuel quantity by double loop control of pump rack position and engine speed. From the experimental results, The engine minimum idle speed has been reduced from 800 rpm at first to 500 rpm, and the speed fluctuation have been reduced by 50 percent. From the system's design and test, the simplicity and efficiency of the HSIC control method were demonstrated.

A simple, but useful method is described for predicting the swirl speed during the compression process in a direct injection diesel engine. The method is based on the idea of dividing the combustion chamber into two volumetric regions and computing the variation of the angular momentum in each region. Laser doppler velocimeter measurements in a motored engine proved the validity of the idea that the volume in the combustion chamber should be treated as two regions, that is, the cylindrical volume inside the piston-cavity radius, and the annular volume outside the piston-cavity radius. Distributions of tangential velocities were measured for different conditions, including the intake port configuration, the piston cavity shape, the compression ratio and the engine speed. These results were integrated in the two regions and provided the measured “two volume-regions” swirl ratio. At the same time, the computation was carried out for the same experimental conditions.

Radial flow Variable Nozzle Turbine (VNT) enables better matching between the turbocharger and engine. At partial loading or low-end engine operating points, the nozzle vane opening of the VNT is decreased to achieve higher turbine efficiency and transient response, which is a benefit for engine fuel consumption and emission. However, under certain small nozzle opening conditions (such as nozzle brake and low-end operating points), strong shock waves and strong nozzle clearance flow are generated. Consequently, strong rotor-stator interaction between turbine nozzle and impeller is the key factor of the impeller high cycle fatigue and failure. In present paper, flow visualization experiment is carried out on a linear turbine nozzle. The turbine nozzle is designed to have single-sided clearance, and the Schlieren visualization method is used to describe the formation and development process of clearance flow and shock wave under different clearance and expansion ratio configurations.