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In recent years, investigations into the formation of mixture or combustion characteristics of diesel spray-wall impingement have been summarized. On one hand, the air entrainment strength and fuel concentration distribution in the near-wall area during the spray-wall collision process have been studied. On the other hand, the combustion characteristics of the impinged spray, including ignition and combustion characteristics, have also been discussed. Additionally, the effect of impingement between spray and wall on real diesel engines’ operating condition has been analyzed and summarized. Results showed that increasing the pressure of the injection and shortening the collision distance could enhance the air entrainment strength of spray-wall impingement. Moreover, increasing the injection pressure, shortening the impingement distance, decreasing the environmental pressure, increasing the wall temperature, and reducing the nozzle diameter all improved the mixture formation. Conversely, reducing the environmental temperature, decreasing the nozzle diameter, and increasing the impingement distance all reduced the concentration of soot, and even achieved no soot formation. Under real diesel engine operation conditions, some of the soot formed in the spray-wall collision and deposited on the wall. The structure of these deposits was mainly a simple cluster structure composed of several basic particles, and the porous structure of the deposits was conducive to the oxidation of soot and reduced the deposition rate.

As the existence of the gap between real-road vehicle fuel consumption rate and type-approval, the researches focused on real-road fuel consumption characteristics are increasing in recent years. However, the quantitative analysis about the reasons caused the real-road high fuel consumption scenarios are rarely reported. In this paper, based on the real-road driving data, the high fuel consumption scenarios in urban, suburb, and high-way conditions have been extracted, which was defined as HFC (high fuel consumption) set, and the reasons caused the HFC set were discussed from the aspect of driving characteristics and driver’s operating characteristics. Results showed that for vehicle speed and gear state factors, it showed a negative correlation with HFC set’s fuel consumption, and the effects became weaker varying to high-way condition, which were just the opposite of vehicle positive acceleration, acceleration pedal opening, and speed per positive acceleration. While the variation rate of acceleration pedal opening showed a weak or no correlation with HFC’s fuel consumption. To sum up, the ranking of each factor’s effect on real-road vehicle fuel consumption of HFC set under all the conditions, from strong to weak, should be vehicle speed per positive acceleration > acceleration pedal opening ≈ vehicle positive acceleration > gear state > vehicle speed, and the effects of acceleration pedal opening and vehicle positive acceleration were almost the same.

The surrogate fuel chemical reaction kinetic mechanism is widely used in computational fluid dynamics (CFD) model to improve the simulation accuracy. The present work developed a new surrogate fuels of heavy fuel oil. The new surrogate fuel includes eight components: C14H16, C16H34, C20H42, C21H44, C5H10, C7H8, C10H8, and C14H10, which were employed according to HFO's measured chemical composition. The newly developed mechanism includes 113 species and 418 reactions. The mechanism was validated with experimental data in shock tube. The surrogate fuel of HFO was chose by comparing heat release rate in fuel ignitability analyzer (FIA). The different ratios of components were researched in surrogate fuel. The surrogate fuel S6 was used as surrogate fuel of HFO. The surrogate fuel S6 of HFO was validated with experimental data in visual constant volume combustion chamber (VCVCC) and marine engine. Satisfactory prediction of spray and combustion development by the present model was shown by comparison with flame images from VCVCC experiments. Last, simulated in-cylinder pressure for a three-dimensional (3D) marine engine CFD model was consistent with experimental and one-dimensional (1D) results. Overall, the S6 mechanism can accurately simulate HFO combustion, bringing the simulation of marine engine a step closer.

In order to further reduce fuel consumption, a double input and single output fuzzy logic controller has been established for the energy management of a parallel hybrid electric vehicle (HEV). In this paper, the fuel economy and battery state of charge(SOC) of vehicles has been numerically investigated under both NEDC and WLTC driving cycles. Results showed that compared with the logic threshold control strategy, the fuel consumption under the NEDC and WLTC driving cycles are reduced by 13.3% and 4.5%, respectively, when the fuzzy logic control strategy was adopted. In addition, compared with the logic threshold control strategy, the fluctuation of SOC variation of the fuzzy logic control strategy is much smaller under both driving cycle, which has a positive effect on increasing the effectiveness of the battery discharge, maintaining stability the battery operating, and extending the battery life.

IMO issued latest environmental regulations Tier Ⅲ has strengthened the emission standards, in which the NOx emission should be less than 3.4g/(kWh) for marine two-stroke engines (engine speed lower than 130r/min) in NOx ECAs. In order to meet the strengthened emission regulations, EGR and fuel injection strategies have been used in marine two-stroke engines to reduce emissions. In this paper, a full cycle computation fluid dynamics (CFD) simulation model has been established in GT-Power software to study the effects of EGR rate, post-injection and pilot-injection on emissions and overall performance of a low speed two-stroke marine engine. By changing the EGR rates and the degree and mass of the post-injection and pilot-injection, an optimal combination among different fuel injection strategies and EGR rates is proposed in this paper. The results indicate that the degree and mass of injection strategies with EGR play an important role in NOx and soot emissions. The trade-off relationship between NOx and soot is improved by changing the fuel injection strategies with different EGR rates.

The chemical mechanism is directly related to the combustion, so it has a great influence on the generation of soot. The aim of this article is to compare the performance of three different mechanisms on soot generation of marine diesel engine (6S35ME-B9) and find out which mechanism has the best performance. The results show that for the influence of soot generation, the difference between the n-tetradecane mechanism and the n-tetradecane-toluene mechanism is not significant, but there are some significant differences compared with the n-heptane mechanism. When the exhaust valve opens, the number densities of soot produced by using n-heptane mechanism is twenty times that of the n-tetradecane and n-tetradecane-toluene mechanism. But the mass of soot produced by using n-tetradecane and n-tetradecane-toluene mechanism is about three times that of the n-heptane mechanism. Then the average particle mass and size of soot produced by using n-tetradecane and n-tetradecane-toluene mechanism is much more than that of the n-heptane mechanism. Ultimately the n-tetradecane mechanism is more suitable for soot simulation of low-speed two-stroke marine engines.

In 2019, China issued the first national standard for vehicle driving cycle, in which China light-duty vehicle test cycle for passenger car (CLTC-P) is the driving cycle for light-duty passenger cars. CLTC-P is of great significance to the development of China’s automobile industry, and has a great impact on the development and calibration of vehicles of automobile enterprises. In this paper, firstly, the driving characteristics of CLTC-P are analyzed systematically. Then it is compared with the third-party navigation big data to prove the rationality and effectiveness. Finally, CLTC-P is compared with other legal cycles in terms of time, distance, speed, and acceleration characteristics. The result shows that by comparing the characteristics of CLTC-P with other typical cycles and the GIS weighted results, the CLTC-P is more in line with Chinese reality and is significantly different from other typical cycles.

To reduce vehicle emissions and control air pollution, China adopted CHINA VI emission standard in 2016, which is one of the most stringent emission standards in the world. In this paper, the emission characteristics of a total of 152 China VI gasoline passenger cars have been investigated in order to understand the present situation of the emission level. Results showed that considering the CHINA VIa limits, the passing rate of A-class passenger cars was higher, while that of B-class was higher. In addition, the influence of the engine types, vehicle models and origin countries on the emission characteristics is also discussed. For both A-class and B-class gasoline passenger cars, CO emissions of vehicles with T engines (Turbocharger engines) were lower, however PN and PM emissions were higher, compared to NA engines (Naturally aspirated engines). NOx, PN and PM emissions were lower for sedan compared to SUV. THC, PN and PM emissions of own independent brand vehicles need to be improved. The qualified rates of Japanese and Korean brand vehicles were the highest, whether it was CHINA VIa or CHINA VIb limits.

China's dual-credit regulation is introduced by Ministry of Industry and Information Technology of China, and its implementation has promoted the development of the new energy vehicles and improved the fuel efficiency of the traditional-fuel vehicle simultaneously in recent years. The amount of production of new energy passenger car reached 0.94 million in 2019, which increased 191.95% compared to the amount of 2016. Meanwhile, the corporate average fuel consumption decreased to 5.73L/100km for domestic production companies and 6.91L/100km for import companies in recent years, and the average annual decreasing rate reached 4.16% and 4.62% per year. In this paper, the development of passenger car's CAFC-NEV dual Credits in China has been discussed including both domestic production and import companies. Results showed that the qualification rate of CAFC for either domestic production or import companies decreased continuously in recent years, which indicated that the difficulties for CAFC compliance were highlighted gradually, especially for the sino-foreign joint companies.

China's dual-credit regulation introduced by Ministry of Industry and Information Technology of China is a big innovation attempt to promote the development of the new energy vehicles and improve the fuel efficiency of the traditional-fuel vehicle simultaneously. Since the implementation of this regulation, it has a significant impact on China's automotive industry trends and auto company's business decisions. As the original edition will expire in 2020, the update edition of this regulation for 2021 and after has been issued on June. 15th, 2020. In this paper, the modifications of this regulation under the lasted update edition have been discussed in detail including the variation of calculation method of NEV credits and its management strategies. In additions, the effects of this update on the NEV credits calculation and management have also been investigated.

The electric mileage of the electric passenger car decreased obviously under high and low temperature conditions due to the use of air conditioning and battery performance fading. In this paper, test procedure under high and low temperature conditions has been established, and the effects of the vehicle type and battery type on energy consumption characteristics under normal, high temperature and low temperature conditions have been investigated based on the results of 18 electric passenger cars. Results showed that a linear relationship between curb weight and energy consumption rate was obtained under all the test conditions, the average energy consumption rate increased 19.82% and 67.3% under high and low temperature conditions, respectively. The differences of the energy consumption characteristics according to the vehicle type was mainly caused by the air conditioning, while the differences according to the battery type was due to the batteries’ low temperature performance including the aspects of discharging voltage, resistance and charging/discharging capacity.

According to the requirements of Normal Temperature Cold Start for the current China six automobile, choose four different light-duty gasoline vehicles, use Beijing six gasoline to carried out type I emission test. Assess WLTC emissions of each interval under the condition of different emission difference, and the causes of pollutant formation in different stages were analyzed. The results show that the WLTC circulation under the cold start phase is still the most pollutants discharge stage, specific performance in cold start phase before the 50s, the main reason is that the exhaust temperature is too low and the catalyst does not light up; Secondly, more pollutants will be produced in the extra-high speed stage, in this stage, open-loop control is used.

This work assessed two types of two-stage injection strategies for the operation of a diesel engine: pilot and early injection. The effects of the two-stage injection interval and the first-stage fuel injection proportion on the combustion and emission characteristics when employing these two injection strategies were investigated by numerical modeling, dividing the in-cylinder zone into three different regions. Variations in the NOx, soot, HC and CO emissions in each region were determined at various values of two-stage injection interval and first-stage fuel injection proportion for both strategies. The results demonstrate that, considering both the engine combustion and emission characteristics, a two-stage injection strategy in conjunction with an injection interval of 30–40°CA and a first-stage fuel injection proportion of 30–60% is advisable.

Referring to GB/T 18386-2017, the impact of NEDC, WLTC and CLTC on the energy consumption of pure electric vehicle is simulated and analysed. Combined with the characteristic parameters of the driving cycles, from the perspective of energy flow loss of each system of the vehicle, the influences of driving cycles on the energy consumption of each part of the vehicle and the working efficiency of the power components are analyzed in detail, and the internal mechanism of the influence rule of driving cycles on energy consumption is revealed. Based on the CLTC, the effects of load mass, ambient temperature and air conditioning on the energy consumption of the electric vehicle are explored. The research results show that the electric vehicle has the longest driving range and the lowest energy consumption under CLTC; as the loading quality increases, the driving range decreases, and the energy consumption per 100 kilometers increases; test temperature and the air conditioner have a great influence on the driving range, especially in the low temperature environment.

Wall wetting in the early injection period has been proved to be unavoidable in the HCCI (Homogeneous charge compression ignition) diesel engine using early injection strategy, which directly affects in-cylinder fuel-air mixture formation. In this study, the effects of the early injection parameters (injection timing, injection angle and injection pressure) on wall wetting characteristics of an HCCI diesel engine using early injection strategy have been numerically investigated. The variations of maximum wall film mass, evaporated wall film mass and residual wall film mass have been summarized. The concept of MHI (Mixture Homogenous Index) is introduced to evaluate the homogeneity of fuel-air mixture in the wall wetting region. In additions, the effects of the early injection parameters on the HC (Hydrocarbon Compounds) and CO (Carbon Monoxide) emissions have also been discussed. Results showed that in order to decrease the HC and CO emission caused by wall wetting as low as possible, it was better to increase the injection pressure and to advance the injection timing. The most effective method was to narrow the injection angle, In addition, the impingement target should be considered for choosing the injection timing and injection angle, and the impingement target of the piston bowl lip was recommended due to the enhancement of the atomization and the higher surface temperature.

In this paper, the effects of the two-stage injection interval and first injection proportion on the combustion and emission characteristics in a diesel engine using two-stage injection strategy have been investigated by numerical modeling methods. Results showed that the combustion and emission characteristics of the diesel engine using two-stage injection strategy were both improved comparing to the original engine. Together considering the fuel economy and emissions problems, the two-stage injection strategy with the injection interval of 30 to 50° CA and first injection proportion of 50% to 70% was recommended.

Effects of viscosity index improver on morphology and graphitization degree of diesel particulate matter were investigated. Three lubricating oils with different viscosity were tested and compared in a two cylinder, four stroke, direct injection diesel engine. 5.0 wt. % and 10 wt. % viscosity index improver were added into lubricating oil to improve the viscosity-temperature performance respectively. Transmission Electron Microscope and Raman spectroscopy were employed to analyze the primary particle size distribution and graphitization degree of diesel particles from different lubricating oils. The primary particles size distribution conformed to Gaussian distribution. When the higher viscosity lubricating oil was used, the primary particle boundaries tend to be clearer and the mean diameter is smaller at 1600 rpm and 2200 rpm. As to the graphitization degree, the ratio of the D1 band to G band areas (AD1/AG) increased with the increasing viscosity at 1600 rpm and 2200 rpm, indicating that the graphitization degree was lower when the higher viscosity lubricating oil was used.

The chemical mechanisms have direct relationship with combustion, so the research of mechanism has been attended by researchers. The aim of article is to compare n-heptane, n-dodecane, n-tetradecane, n-hexadecane, which can give a direction for alternative fuels. This article compared the performance of alkanes in different conditions, such as shock tube and HCCI. The results show that difference of ignition delay time is relatively little at two ends of temperature. The large difference can be found in NTC range, especially the pressure is 13.5 atm and equivalence ratio is 1. The results also show that the trends of main species are same for different alkanes. The increasing time of CO and H2O2 are earlier than that of others for the n-tetradecane. The changes of in-cylinder temperature and pressure are same for alkanes with increasing equivalence ratio and inflow pressure.

Different combustion models and alternative fuels can be used in simulations under the same operating conditions to study their effects on marine diesel engine performance. In-cylinder pressure and temperature, emission products (NOx, HC, CO, CO2), and the distributions of equivalence ratio, temperature and emission products were simulated. The simulation model was validated with experimental data. Errors in in-cylinder pressure and emissions were in the acceptable range. Results show that the maximum in-cylinder combustion pressure calculated using the detailed chemistry solver combustion model (SAGE) is closer to the experimental data than the results of others models. There is little difference in pressures between n-heptane and n-tetradecane in the same combustion model. The integrated heat releases are almost the same for the different models. However, the n-heptane-SAGE model has a larger error than do the other models for the quantity of NOx. Comparing the errors of NOx, HC, CO and CO2, the n-heptane-CTC/shell simulation model data are closest to the experimental data. The important element reactions of the alternative fuel mechanism needs to be adjusted to ensure the emissions are consistent with experimental data. Finally, the contours of temperature, equivalence ratio and emission products are validated by comparing the results of different models.

Spray wall impingement in the early injection period has been proved be unavoidable in the diesel engine using early injection strategy. The formation of wall film directly affects fuel/air mixture formation, combustion, exhaust emissions and oil quality. In this study, experiments were carried out to investigate the wall film ratio of pure diesel, butanol/diesel, DME (Di Methyl Ether)/diesel and gasoline/diesel blended fuels. The variations of wall film ratio with different injection pressures, impingement distances, impingement angles and blending ratios were compared under both dry wall and wet wall conditions. For both dry wall and wet wall conditions, with increasing injection pressure and blending ratio, wall film ratio decreased, which is the opposite trend to impingement distance and impingement angle variations. Some dimensionless numbers also have been introduced in order to evaluate the effect of each impact factor on the variation of wall film ratio. Results showed that impingement momentum is the major impact factor on wall film ratio when varying the injection pressure or impingement distance. Impingement flow mass is the major impact factor when varying the impingement angle. For different blending ratios, the wall film ratio is mainly influenced by surface tension, followed by viscosity and saturated vapor pressure. In addition, the equations between the wall film ratio and Weber number of the impingement droplet were derived for each test fuel.

Rigorous current regulation requires decrease emissions from marine engines. It is difficult to test all technologies for marine engines using experimental methods. It is important to develop simulated models for alternative fuels. A semireduced kinetic mechanism can be constructed to investigate the performance of the marine diesel engine, which consists of 341 elementary reactions and 74 species. Then, the Directed Relation Graph with Error Propagation (DRGEP) and the sensitivity analysis methods were used to reduce this mechanism. The reduced mechanism consists of 279 elementary reactions and 62 species. The ignition delay times with the semidetailed and reduced mechanisms were validated with the experimental data. At the same time, the results were compared with the data of published mechanisms. Good agreements of ignition delay times were obtained. It was also found that the trends of in-cylinder temperature, pressure, and main species mole fractions were almost the same as results of the published m...

Due to the increasing awareness of environmental protection, limitations on exhaust emissions of diesel engines have become increasingly stringent. This challenges diesel engine manufacturers to find a new balance between engine performance and emissions. Advanced combustion modes for diesel engines, such as homogeneous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI), which can simultaneously reduce exhaust emissions and substantially improve thermal efficiency, have drawn increasing attention. In order to allow enough time to prepare the homogeneous mixture, the early injection strategy has been utilized widely in HCCI and PCCI diesel engines. This paper is aimed at providing a comprehensive review of the effects of early injection parameters on the performance and emissions of HCCI and PCCI engines fueled by both diesel and alternative fuels. Various early injection parameters, including injection pressure, injection timing, and injection angle, are discussed. In addition, the effect of the blending ratio of alternative fuels is also summarized. Every change in parameters has its own advantages and disadvantages, which are explained in detail in order to help researchers choose the best early injection parameters for HCCI and PCCI engines.

The simulation model of two-stroke heave fuel oil marine diesel engine was developed in this paper. The model was validated with the experimental data. The ability of NOx reduction was researched for exhaust gas recirculation, humid air motor and miller cycle based on the simulation model. The results show that the EGR has the most potential to reduce the NOx emission. It can make the quantity of NOx meet the requirement of Tier Ⅲ. The reduction value of NOx was less for miller cycle. The HAM can be reduced the NOx. However, the depth of HAM was limited.

As the application of several energy saving technologies and the continuous tightening fuel consumption standards, the fuel consumption of China’s gasoline passenger cars is decreasing continuously. In this paper, the development of the standards related to fuel consumption was reviewed firstly, and the development of the fuel consumption for China’s gasoline passenger cars has been investigated based on the declared fuel consumption data of over 4800 vehicle models produced or imported in recent 5 years (2014-2018). Results showed that the average fuel consumption in 2018 decreased 6.4% compared to 2014, about 1.6% per year. In additions, the development of gasoline passenger cars with turbocharge engines and auto transmissions had a more significant effect on the fuel consumption reduction, and the annual decreasing rate reached 2.4% per year and 3.6% per year, respectively.

In order to verify the necessity of the application of China Automotive Test Cycle which is constructed through actual driving data in china of more than 55 million kilometers in the energy consumption test of electric vehicles in China, this paper compares the characteristics of New European Test Cycle (NEDC), World-wide harmonized Light duty Test Cycle (WLTC) and China light-duty vehicle test cycle for passenger car(CLTC-P), and analyzes the differences of vehicle energy demand under different test cycles from theoretical and simulation point, simulation results show that the endurance mileage is longest and the energy recovery strategy is more effective under CLTC-P cycle. Finally, four types of vehicles are selected to carry out the endurance mileage test under these three test cycles. The test results are consistent with the simulation results. Therefore, in order to make the test results of electric vehicle energy consumption closer to the actual use of our country, CLTC-P should be selected to replace NEDC and WLTC cycle.

n-Butanol is one of the most promising conventional fuel alternatives for diesel engines using advanced combustion modes such as homogeneous charge ignition and premixed charge compression ignition. However, effects associated with the structural design of these engines as well as early injection strategies still result unavoidable spray–wall impingement when using n-butanol/diesel blended fuels, which directly affects the combustion and emission characteristics of the diesel engines. The present work therefore investigated the spray–wall impingement characteristics of n-butanol/diesel blended fuels under various environmental conditions and when applying different injection strategies. The parameters that were varied included fuel temperature, environmental temperature and pressure, impingement distance, blending ratio, and the presence or absence of an oil film. The impingement spray radius (Rw) and height (Hw) were obtained experimentally so as to evaluate the impingement characteristics, and the effects of each parameter on Rw and Hw were assessed. In addition, based on the momentum transition of the impinged spray, the variations in Rw and Hw were attributed to four factors: the mass and momentum of the impinged spray; the spreading or splashing resistance of the spray, and the strength of air entrainment. The relative effects of each of these factors on Rw and Hw were examined, and results showed that the spray impingement momentum had the greatest effect on Rw, followed by air entrainment, while the impact of the fuel viscosity and surface tension (or spreading resistance) were limited. However, the effects of spray impingement momentum and air entrainment on Hw were less pronounced, while the viscosity and surface tension had a greater impact.

This study focuses on the effects of an anti-wear oil additive on physical characteristics of particles exhausted from a diesel engine, by using fast particulate spectrometer, transmission electronic microscopy techniques. Results show that the oil additive may increase the number of particles via impacting the combustion reactions. We also conclude that, given the low fractal dimensions of aggregates, the particles exhausted from the fuel blended with the additive were mainly bonded in a cluster–cluster fashion. In addition, analysis of the nanostructure highlights that the degree of graphitization of the particles has also been influenced by anti-wear additive.

As the test cycle used for evaluating the fuel consumption and emission characteristics of the heavy-duty commercial vehicle in China will be replaced from C-WTVC to CHTC in a round 2020, the investigation on the variation of fuel consumption and emission test results after the replacement is well needed for further vehicle’s development and calibration. In this paper, the fuel consumption and emission characteristics of a China VI coach under these two test cycles have been discussed and compared. Results showed that fuel consumption, CO, HC and NOx emissions of the test coach all increased after changing the test cycle from C-WTVC to CHTC, which were due to the low rotation speed and low torque operating points, and the aggressive and frequent acceleration under CHTC. In addition, Acceleration driving condition contributed most to the deterioration of fuel consumption, CO, HC and NOx emissions under CHTC, which attention should be especially paid in the further vehicle calibration.

Due to the stricter roles of the government and the higher requirement of a comfortable automobile, the NVH (Noise Vibration and Harshness) performance of vehicles has become one of the most important traits at the automobile market. Considering the cost, it is more economical and practical to improve the NVH performance by using the vibration-isolating or noise-reducing materials. Vibration damping alloy as one of the new material has a promising prospect due to its great damping characteristics. In this paper, the vibration-isolating and noise-reducing performances of the vibration damping alloy have been experimentally investigated in a semi-anechoic room. Frequency response function test has been carried with the test rod made of vibration damping alloy and 45 steel to calculate the damping ratio of the two materials based on the half-power bandwidth method. The radiation noise characteristics of the two test rods under different excitation forces have also been evaluated. Conclusions drawn from the experiment suggested that the damping ratio of 45 steel rod were 0.0125 in vertical axial direction and 0.0165 in axial direction. While, the damping ratio of vibration damping alloy rod were 0.0236 in vertical axial direction and 0.0234 in axial direction, 89% and 42% higher than the 45 steel sample, respectively. With the increase of the exciting force, the radiation noise increased for both two materials, and the radiation noise level of the vibration damping alloy rod was much lower than 45 steel rod. And the difference between these two materials remained unchanged with the increase of exciting force. In addition, the duration of noise attenuation for vibration damping alloy rod was much shorter than the 45 steel.

The involute spur gear system has been widely utilized in the mechanical transmission domain, and the control of the acceleration noise of the involute spur gear system has become the key technology to solve the NVH performance of the power transmission system, especially in the automobile industry. In the process of the gear meshing, the unavoidable acceleration noise of the involute spur gear system is mainly caused by the meshing stiffness and error excitation due to the structural parameters. Therefore, the investigation on the effects of structure parameters on acceleration noise of the involute spur gear system is necessary. In this paper, the numerical model for predicting the acceleration noise of the involute spur gear system has been established. The simulation results of the acceleration noise were compared with the experimental results, and the errors between these two results were only 2.9%, within permission. The effects of structure parameters including base pitch error and pressure angle on the acceleration noise of the involute spur gear system have been discussed. Results showed that increasing the base pitch error, the acceleration noise level of the involute spur gear increased, and the gap of the noise level between different base pitch errors narrowed according to the increase of gear load and rotation speed. Increasing the pressure angle also increased the acceleration noise level, however, the gap between different pressure angles remained the same regardless the variations of gear load and rotation speed, which was different than the variations of base pitch error.

The effect of wall roughness with different lubricant film thicknesses on the characteristics of adhered fuel films of diesel-n-butanol blending fuels after spray impingement has been investigated. Four steel plates with different types of roughness (root mean square height-Sq) that were coated with different lubricant film thicknesses (hl) were used as impinged walls. The experimental conditions included dry walls (hl = 0), semi-wetted walls (SWW) with different thin oil films (0 &lt, hl/Sq &lt, 1), and fully wetted walls (FWW) with a thick lubricant film (hl &gt, Sq). The results indicate that the adhered fuel mass ratio (&epsilon, ) of blended fuel with 25% n-butanol (B25) was higher than that of blended fuel with 15% n-butanol (B15) under the same conditions. &epsilon, increased with an increase in Sq on the dry walls, but, under SWW conditions, it decreased with an increase in oil film thickness. The fuel film morphology was almost unaffected by the change in Sq, but the results implied that the roughness parameter-Skewness (Ssk) exerted a greater impact. The mean thickness ha and accumulated diameter Dl of the adhered fuel film increased with an increase in hl, but, under FWW conditions, the effect of the roughness on the adhered film&rsquo, s features was insignificant.