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Exhaust gas recirculation technology is one of the main methods to reduce engine emissions. The pressure of the intake pipe of turbocharged direct-injection diesel engine is high, and it is difficult to realize EGR technology. The application of Venturi tube can easily solve this problem. In this paper, the working principle of guide-injection Venturi tube is introduced, the EGR system and structure of a turbocharged diesel engine using the guide-injection Venturi tube are studied. According to the working principle of EGR system of turbocharged diesel engine, the model of guide-injection Venturi tube is established, the calculation grid is divided, and it is carried out by using Computational Fluid Dynamics method that the three-dimensional numerical simulation of the internal flow of Venturi tube under different EGR rates injection.

During current design process of vehicle engine exhaust system, the frequently-used approach mainly concerns an individual component, which usually results in not meeting the overall design requirements or unreasonable design parameters. Here a concept of comprehensive evaluation metrics for vehicle engine exhaust system was established, of which a new weight factor assignment method was proposed, named change rate method, as the core of evaluation system to be especially studied. Taking muffler as an instance, six weight factor assignment schemes were adopted to compare with each other. And the rationality and practicability of the change rate assignment method was verified by the muffler noise experiments. The results show that, the change rate method makes the weight assignment more scientific and rigorous. And the new method can reflect the wishes of designers and completely displays the performance comparison and evaluation between schemes.

It has been revealed by researches that lubricant properties have a great effect on the low-speed pre-ignition (LSPI) frequency in downsizing turbocharged direct-injection engines which are developed for better fuel economy. Droplets of lubricant or lubricant-gasoline mixture are considered to be the potential pre-ignition sources. Those droplets fly into the combustion chamber and ignite the gasoline-air mixture. To study lubricant droplets fundamentally, a novel set of droplet auto-ignition system is designed based on a Dibble Burner for this experiment. Influences of metallic additive contents, viscosities, lubricant diluted with gasoline and waste lubricant on the ignition delay of droplets are investigated by testing 12 groups of lubricants or lubricant-gasoline mixture. The equivalent diameter of each droplet generated by micro-syringes is around 2.1 mm. The co-flow temperature varies from 1123 K to 1223 K, and the experiments are carried out at atmospheric pressure.

Recently Hybrid Electric Buses (HEBs) have been widely used in China for energy saving and emission reduction. In order to study the real road emission performance of HEBs, the emission tests of an in-use diesel-electric hybrid bus (DHEB) are evaluated both on chassis dynamometer over China City Bus Cycles (CCBC) and on-road using Portable Emissions Measurement Systems (PEMS). The DHEB is powered by electric motor alone at speed of 0~20km/h. When the speed exceeds 20km/h, engine gets engaged rapidly and then works corporately with the electric motor to drive the bus. For chassis dynamometer test over CCBC, emissions of NOx, particulate number, particulate mass, and THC of the DHEB are 7.68g/km, 5.88E+11#/km, 0.412mg/km, and 0.062g/km, respectively. They have all decreased greatly compared to those of the diesel bus. But the CO emission which is 3.48g/km has increased significantly. Then the Real Driving Emissions (RDE) of the DHEB are compared with the dynamometer test results.

Engine compartment thermal management can achieve energy saving and emission reduction. The structural design of the components in the engine compartment affects the thermal fluid flow performance, which in turn affects the thermal management performance. In this paper, based on the phenomenon that the surface of the parts in the engine compartment is abnormally high due to design defects of an SUV engine compartment bottom shield, the engine compartment is modeled and analyzed by CFD using the software STAR-CCM+. It is not conducive to the heat dissipation, so the bottom shield needs to be redesigned. To redesign the shape of the bottom shield, four dimensions and one coordinate value were selected as the design parameters, and the oil pan maximum surface temperature was selected as the optimization target. The Latin hypercube sampling method was used to sample the space uniformly, and the experimental design plan was constructed and simulated.

In order to investigate the impacts of recirculated exhaust gas temperature on gasoline engine combustion and emissions, an experimental study has been conducted on a turbocharged PFI gasoline engine. The engine was equipped with a high pressure cooled EGR system, in which different EGR temperatures were realized by using different EGR coolants. The engine ran at 2000 r/min and 3000 r/min, and the BMEP varied from 0.2MPa to 1.0MPa with the step of 0.2MPa. At each case, there were three conditions: 0% EGR, 10% LT-EGR, 10% HT-EGR. The results indicated that LT-EGR had a longer combustion duration compared with HT-EGR. When BMEP was 1.0 MPa, CA50 of HT-EGR advanced about 5oCA. However, CA50 of LT-EGR could still keep steady and in appropriate range, which guaranteed good combustion efficiency. Besides, LT-EGR had lower exhaust gas temperature, which could help to suppress knock. And its lower exhaust gas temperature could reduce heat loss. These contributed to fuel consumption reduction.

PN(Particle Number) emission limits are more stringent for gasoline vehicles in Chinese VI emission standards (6×1011 #/km). A EEPS engine exhaust particle size spectrometer was employed to characterize the effects of injection strategies on particulates emissions from a turbocharged gasoline direct injection (GDI) engine. The effects of operating parameters (injection pressure, second injection ratio and second injection end time) on particle diameter distribution and particle number density of emission was Investigated. The experimental result indicates that the quantity of particles decrease with the increase of injection pressure obviously, especially at high load including the 20% reduction of the particle number density. When the engine is at low load, the accumulation mode particle emissions are higher than the nucleation mode particle emissions compared with high load, which present opposite results. The second injection can restrain engine knock at low speed.

Urea-SCR system is one of the after-treatment methods for diesel engines, which could effectively reduce the NOX emissions and enable diesel engines to meet increasingly stringent emission legislations. Within the urea-SCR system, characteristics of urea-solution spray, especially the distribution uniformity of spray droplets as well as gaseous NH₃ within the exhaust pipe, play an important role in the efficiency of catalytic reduction. In this paper, an SCR spray visualization test bench was set up. Urea-solution from a non-air-assist injector is injected into the steady stream of simulated exhaust gas flow. The transient characteristics of spray are recorded by high-speed photography. Specific spray characteristics in the original photographs, i.e., mixing distance and degree of uniformity are extracted. The influence of injection pressure and injection angle on spray characteristics are tested in different sets of experiments.

Argon power cycle hydrogen engine is an internal combustion engine that employs argon instead of nitrogen of air as the working fluid, oxygen as the oxidizer, and hydrogen as the fuel. Since argon has a higher specific heat ratio than air, argon power cycle hydrogen engines have theoretically higher indicated thermal efficiencies according to the Otto cycle efficiency formula. However, argon makes the end mixture more susceptible to spontaneous combustion and thus is accompanied by a stronger knock at a lower compression ratio, thus limiting the improvement of thermal efficiency in engine operation. In order to suppress the limitation of knock on the thermal efficiency, this paper adopts a combination of experimental and simulation methods to investigate the effects of port water injection on the knock suppression and combustion characteristics of an argon power cycle hydrogen engine.

With regulatory standards for diesel engine emissions becoming stricter worldwide, integrated catalytic systems are becoming increasingly necessary. One of the better approaches is to use an after-treatment system consisting of a diesel oxidation catalyst (DOC), a catalyzed diesel particulate filter (CDPF), and a selective catalytic reduction (SCR), but many factors can affect how well this system works. This study investigates the effects of DOC and CDPF catalyst composition on emissions characteristics for DOC + CDPF + SCR systems by collecting reactor and engine data. The reactor results show that the light-off temperatures (T50) of CO and C3H6 increase with the growth of Pt:Pd ratio while the T50 of NO degrades. An engine dynamometer test was conducted on a light-duty diesel engine equipped with DOC + CDPF + SCR. The results show light-off curves of CO and THC that are smoother than the reactor data.

To improve the thermal efficiency and inhibit the knock tendency of gasoline direct injection (GDI) engines, water injection technology has a bright application prospect. Utilize gasoline/water mixture as a way to realize this technology can lower the cost of modifying the engines and bring potential for better spray qualities. Hence it is essential to give deep insight into the effects of water on spray atomization, evaporation and mixture formation for gasoline/water mixtures. A spray synchronous measurement experimental system with a single hole nozzle is used to investigate the spray morphology, spray width and droplet size distribution of gasoline/water mixtures sprays under different water volume fractions (0 %, 20 %, 35 %) and different initial fuel temperatures (50 °C~ 130 °C). There are critical temperatures of 80 °C(G100), 100 °C(G80) and 120 °C(G65), above which the ‘collapsed’ spray appears.

To meet the increasingly stringent nitrogen oxides (NOx) emission regulations of diesel engines, the selective catalytic reduction (SCR) of NOx with ammonia (NH3) has become the current mainstream technical route. Experiments in the present study included the performance of Cu-Beta catalyst and Cu-CHA catalyst before and after hydrothermal aging, and the effects of Cu content, feed gas space velocity (GHSV), NH3/NOx ratio, and sulfur poisoning on the performance of Cu-CHA catalyst. In the low temperature range (T≤250 °C), the T50 and T90 of Cu-Beta catalyst are 139 °C and 165 °C, respectively, while those of Cu-CHA catalyst are 150 °C and 183 °C, respectively. In the high temperature range (T>400 °C), the NOx conversion of Cu-CHA catalyst is generally higher than that of Cu-Beta catalyst. The temperature window of Cu-Beta catalyst is 154 to 514 °C, while that of Cu-CHA catalyst is 168 to 522 °C. Cu-CHA catalyst exhibits better catalytic activity at medium and high temperatures.

Argon Power Cycle (APC) is an innovative future potential power system for high efficiency and zero emissions, which employs an Ar-O2 mixture rather than air as the working substance. However, APC hydrogen engines face the challenge of knock suppression. Compared to hydrogen, methane has a better anti-knock capacity and thus is an excellent potential fuel for APC engines. In previous studies, the methane is injected into the intake port. Nevertheless, for lean combustion, the stratified in-cylinder mixture formed by methane direct injection has superior combustion performances. Therefore, based on a methane direct injection engine at compression ratio = 9.6 and 1000 r/min, this study experimentally investigates the effects of replacing air by an Ar-O2 mixture (79%Ar+21%O2) on thermal efficiencies, loads, and other combustion characteristics under different excess oxygen ratios. Meanwhile, the influences of varying the methane injection timing are studied.

With the continuous upgrading of emission regulations, NOx emission limit is becoming more and more strict, especially in the cold start phase. Passive NOx absorber (PNA) can adsorb NOx at a relatively low exhaust temperature, electrically heated catalyst (EHC) has great potential to improve exhaust gas temperature and reduce pollutant emissions of diesel engines at cold start conditions, while experimental research on the combined use of these two kinds of catalysts and the coupling mode of the electrically heated catalyst and the aftertreatment system under the cold start condition are lacking. In this paper, under a certain cold start and medium-high temperature phase, the exhaust gas temperature and emission characteristics of PNA, EHC and aftertreatment system under different coupling modes were studied.

Due to the oil crisis and the requirements of energy saving and emission reduction, the research of alternative energy sources for sustainable development has made good progress. Methanol has proven to be a very suitable alternative clean fuel. Compared with gasoline, methanol has a wide range of source and the higher oxygen content and octane number and combustion efficiency, which are beneficial for the engine performance. The effect of different proportions of methanol-gasoline mixed fuel on the performance of SI engine was studied experimentally (lower proportion and higher proportion). It was found that the engine power performance, fuel economy and exhaust emissions were related to the methanol ratio under different operating conditions. In order to adapt to different operating conditions to improve the performance of methanol-gasoline engine, an on-board flexible fuel mixed system was proposed.

In this paper, a low-speed pre-ignition (LSPI) diagnostic strategy is designed based on the ion current signal. Novel diagnostic and re-injection strategies are proposed to suppress super-knock induced by pre-ignition within the detected combustion cycle. A parallel controller system that integrates a regular engine control unit (ECU) and CompactRIO (cRIO) from National Instruments (NI) is employed. Based on this system, the diagnostic and suppression strategy can be implemented without any adaptions to the regular ECU. Experiments are conducted on a 1.5-liter four-cylinder, turbocharged, direct-injected gasoline engine. The experimental results show two kinds of pre-ignition, one occurs spontaneously, and the other is induced by carbon deposits. Carbon deposits on the spark plug can strongly interfere with the ion current signal. By applying the ion current signal, approximately 14.3% of spontaneous and 90% of carbon induced pre-ignition cycles can be detected.

Due to much higher pressure and pressure rising rate, knocking is always of potential hazards causing damages in the engine and high NOX emissions. Therefore, the researchers have focused on knocking diagnosis and control for many years. However, there is still lack of fast response sensor detecting in-cycle knocking. Until now, the feedback control based on knocking sensor normally adjusts the injection and ignition parameters of the following cycles after knocking appears. Thus in-cycle knocking feedback control which requires a predictive combustion signal is still hard to see. Ion current signal is feasible for real-time in-cylinder combustion detection, and can be employed for misfiring and knocking detection. Based on incylinder pressure and ion current signals, the in-cycle knocking feedback control is investigated in this research. The 2nd-order differential of in-cylinder pressure, which means the response time of pressure rising rate dPR, is employed for knocking prediction.

A computational study was conducted in order to characterize the heat transfers in a sedan vehicle underbody and the exhaust system. A steady-state analysis with consideration for both the radiation and conjugate heat transfers was undertaken using the High-Reynolds formulation of the k-epsilon turbulence model with standard wall function and the DO model for the radiation heat transfer. All three mechanisms of heat transfer, i.e., convection, conduction, and radiation, were included in the analysis. The convective heat transfer due to turbulent fluid motion was modeled with the assumption of constant turbulent Prandtl number; and heat conduction was solved directly for both fluid and solid.

Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which replaces air with argon/oxygen mixtures as working fluid. However, one major challenge is severe knock caused by elevated in-cylinder temperature resulting from high specific heat ratio of Argon. A typical knock-limited compression ratio is around 5.5:1, which limits the thermal efficiency of Argon Power Cycle engines. In this article, preliminary experimental research on the effect of water direct injection at late exhaust stroke is presented at 1000 r/min with IMEP ranging from 0.3~0.6 MPa. Results show that, with temperature-reducing effect of water evaporation, knock is greatly inhibited and the engine can run normally at a higher compression ratio of 9.6:1. Water injected at the exhaust stroke minimizes its reducing effect on the specific heat ratio of the working fluid during the compression and expansion strokes.

In order to meet the ever more stringent demands on the CO2 emission reduction, downsized modern gasoline engine with highly boosted turbo charger meets new challenges such as super knock and pre-ignition, which will influence the engine combustion efficiency, smooth operation and even cause mechanical failure. A spark plug type ion current detection sensor was used in a 1.8L turbo charged gasoline engine. The ion-current wave signal differed greatly under different engine operating conditions such as without knock, with knock of different knock intensities. The frequency spectrum of ion-current was also studied, by the method of discrete Fourier transform (DFT). In knocking cycles, there were fluctuations of frequency 8-13 kHz both in the combustion pressure signal and in the ion current signal, proving the existence of knock information.