Comparative Life-Cycle Assessment of Liquefied Natural Gas and Diesel Tractor-Trailer in China

Many countries, especially China, have extensively promoted liquefied natural gas (LNG) to replace diesel in heavy-duty vehicles for to achieve sustainable transport aims, including carbon peaks and neutrality. We developed a life-cycle calculation model for environmental load differences covering vehicle and fuel cycles to comprehensively compare the LNG tractor-trailer and its diesel counterpart in China on a full suite of environmental impacts. We found that the LNG tractor-trailer consumes less aluminum but more iron and energy; emits less nitrogen oxide, sulfur oxide, nonmethane volatile organic compounds, and particulate matter but more greenhouse gases (GHG) and carbon monoxide (CO); and causes less abiotic depletion potential, acidification potential, and human toxicity potential impacts but more global warming potential (GWP) and photooxidant creation potential (POCP) impacts. Poor fuel economy was found to largely drive the higher life-cycle GHG and CO emissions and GWP and POCP impacts of the LNG tractor-trailer. Switching to the LNG tractor-trailer could reduce carbon dioxide by 52.73%, GWP impact by 44.60% and POCP impact by 49.23% if it attains parity fuel economy with its diesel counterpart. Policymakers should modify the regulations on fuel tax and vehicle access, which discourage improvement in LNG engine efficiency and adopt incentive polices to develop the technologies.

Experimental Analyses of the Additive Effect of TiO2 Nanoparticles on the Tribological Properties of Lubricating Oil

Titanium dioxide (TiO2) is a promising lubricant additive for enhanced engine efficiency. In this study, pure base engine oil 10 W-30 was improved with titanium dioxide (TiO2) nanoparticles at different concentrations and experimentally evaluated with the scope of tribological behavior improvement. The tribological tests were performed at ambient temperature as well as at 75°C using a four ball tribometer for 30 minutes. Due to their small particle size (approx. 21 nm), the TiO2 nanoparticles were properly dispersed in oil based on optical microscopy evaluation. The tribological results indicate that the friction coefficient of engine oil with 0.075 wt.% TiO2 reached 0.05 at 75°C, which was much lower that of pure oil (1.20), and at room temperature (23°C), it decreased from 1.8 for pure oil to 0.4 for oil with 0.075 wt.% TiO2 due to the formation of a stable tribofilm formed by the MoS2, MoO3, FeS, and FeSO4 composite within the wear track. The lowest wear volume was measured on samples tested at 75°C for the oil with 0.075 wt.% TiO2. The TiO2 additive lubricant effect on the tribofilm properties led to a decrease in friction and wear at an operating temperature of 75°C. The main objective of the paper is to present the recent progress and, consequently, to develop a comprehensive understanding of the tribological behavior of engine oil mixed with TiO2 nanoparticles.

Estimates of the air-fuel ratio at the time of ignition in a pre-chamber using a narrow throat geometry

The benefits of pre-chamber combustion (PCC), such as improved engine efficiency and reduced NOx emissions, are primarily observed when operating at lean conditions with an active pre-chamber, where auxiliary fuel is supplied directly to the pre-chamber. Estimating the pre-chamber excess air ratio (λ) is important in the active pre-chamber concept to gain insights into the pre-chamber combustion phenomenon. Experimental investigations were performed using a narrow-throat pre-chamber at global-λ 1.6, 1.8, and 2.0. The fraction of fuel energy injected in the pre-chamber over the total fuel energy was fixed at 3%, 7%, and 13% for each global-λ. The mixture formation process inside the pre-chamber is first simulated using the 1-D simulation software GT-Power to analyze the pre-chamber λ at the ignition timing. However, the 1-D results were unable to reproduce the experimental observations on the pre-chamber pressure buildup accurately. Upon simulating the same conditions using the 3-D CFD software CONVERGE, the pre-chamber λ estimated from the CFD model is well-correlated to the experimental data. The CFD results indicate that the amount of fuel trapped in the pre-chamber at the inlet valve closing timing is over-predicted by the 1-D simulations. A correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models and applied to the 1-D simulation results to improve pre-chamber λ prediction accuracy.

Application of Ultrasonic Atomization on a Micro Jet Engine Using Biofuel for Improving Performance

Jet engines are commonly used in aeronautical applications, and are one of the types of gas turbine engines. The circulation of air releases heat energy to expand the volume of hot fluids and impact the turbine wheel to generate power of hot gases. The present study investigates the potential of using ultrasonic atomization technology to assist in the combustion process. An experimental rig was set up to determine the performance of jet engines using ultrasonic droplets. A gas analyzer was used to measure various greenhouse emissions of exhaust gas. The performance of the engine was tested under three load levels (high, medium, low), starting from 10 psi at a steady state, to the minimum value. A significant result was tested for a low value of nitrogen monoxide at the three levels of load, and a specific result was tested for an efficiency value of 2% at the three levels of load. Carbon dioxide was found to decrease at the low load level. The use of an ultrasonic atomization device to assist in the combustion process was useful in achieving engine efficiency of 1% and a reduction of 25% in carbon dioxide exhaust gas.

Improving Search Engine Efficiency through Contextual Factor Selection

Learning to rank (LTR) is an important artificial intelligence (AI) approach supporting the operation of many search engines. In large-scale search systems, the ranking results are continually improved with the introduction of more factors to be considered by LTR. However, the more factors being considered, the more computation resources required, which in turn, results in increased system response latency. Therefore, removing redundant factors can significantly improve search engine efficiency. In this paper, we report on our experience incorporating our Contextual Factor Selection (CFS) deep reinforcement learning approach into the Taobao e-commerce platform to optimize the selection of factors based on the context of each search query to simultaneously maintaining search result quality while significantly reducing latency. Online deployment on Taobao.com demonstrated that CFS is able to reduce average search latency under everyday use scenarios by more than 40% compared to the previous approach with comparable search result quality. Under peak usage during the Single’s Day Shopping Festival (November 11th) in 2017, CFS reduced the average search latency by 20% compared to the previous approach.

Experimental Investigation of the Influence of Engine Operating and Lubricant Oil Parameters on Sliding Bearing and Friction Behavior in a Heavy-Duty Diesel Engine

In order to rise to global challenges such as climate change, environmental pollution and conservation of resources, internal combustion engine manufacturers must meet the requirements of substantially reduced emissions of CO2 and other greenhouse gases, zero pollutant emissions and increased durability. This publication addresses approaches that can help improve engine efficiency and durability through the engine crankshaft bearing and lubricant system. An understanding of the operating behavior of key engine components such as crankshaft main bearings in fired engine operation allows the development of appropriate tools for bearing condition monitoring and condition-based maintenance so as to avoid critical engine operation and engine failure as well as unnecessary engine downtime. Such tools are especially important when newly developed low viscosity oils are employed. Though these oils have the potential to reduce friction and to increase engine efficiency, their use comes with a higher risk of accelerated bearing wear and ultimately bearing failure. The specific target of this paper is therefore to obtain detailed knowledge of the influence of engine operating parameters and oil parameters on crankshaft main bearing temperature behavior and engine friction behavior in fired operation as a starting point for condition monitoring and condition-based maintenance approaches and as a basis for improving the bearing and lubricant system as a whole. To achieve this target, experimental investigations were carried out on an engine test bed employing an in-line six-cylinder heavy-duty diesel engine with a displacement of approximately 12.4 dm3. Defined and accurately reproducible engine operating conditions were ensured by comprehensive external conditioning systems for the coolant, lubricating oil, fuel, charge air and ambient air. Since the focus was on investigating the bearing and friction behavior by means of the base engine, several auxiliary systems were removed; these included the lubricating oil and coolant pumps, the front-end accessory drive and the generator. Each crankshaft main bearing was instrumented with a thermocouple on the back of its bottom bearing shell to measure the bearing temperature. Piezoelectric pressure transducers were applied to all six cylinders in order to facilitate the accurate determination of the friction mean effective pressure (FMEP) based on indicated and brake mean effective pressures. The variations in engine operating parameters (engine speed and torque) mainly serve as a reference for the variations in oil parameters. They confirm the existing knowledge that engine speed has a significant impact on FMEP and bearing temperature while the impact of engine torque is comparatively low. The variations in oil parameters reveal that lowering the viscosity grade from SAE 10W-40 to 5W-20 leads to a decrease in both bearing temperature and FMEP, which can be explained by the lower fluid friction in the bearing system and the increased mass flow and convective heat transport with the lower viscosity oil. An increase in the lubricating oil temperature at the engine inlet leads to a significant increase in bearing temperature and a decrease in FMEP; the former is explained by the increased heat influx from the lubricant oil, and the latter is caused mainly by the temperature dependency of the lubricant oil viscosity and its impact on fluid friction. The impact of engine oil inlet pressure on bearing temperature and FMEP is generally found to be low. The results will serve as the basis for future research that includes approaches to condition monitoring and evaluating improved engine operating strategies with regard to oil parameters.

Modifikasi Mesin Pencacah Plastik PET Tipe Gunting dengan Kapasitas 50 kg/jam

Abstrak Mesin pencacah plastik merupakan sebuah mesin yang dirancang untuk mencacah sampah plastik agar mengurangi volume sampah. Mesin pencacah dirancang mampu mencacah sampah dengan kapasitas pencacahan 50 kg/jam, hasil analisa kinerja mesin pencacah memperlihatkan bahwa kapasitas mesin pencacah adalah 36.68 kg. Analisis kinerja mesin lain adalah: efisiensi mesin nilainya 73,37 %; tingkat kebisingan mencapai 80,6 dB; getaran yang dihasilkan saat melakukan pencacahan adalah 4,9 mm/s2, dan rendemen cacahan 73,45 %. Hasil analisa kinerja memperlihatkan bawah mesin pencacah perlu dimodifikasi agar sesuai dengan hasil perancangan awal. Modifikasi dilakukan dengan mengubah saringan, mengatur ulang jarak antara mata pisau, dan menambahkan pisau pada pisau putar. Modifikasi yang dilakukan berhasil meningkatkan kapasitas mesin pencacah menjadi 42,59 kg/jam; tingkat kebisingan menjadi 76,8 dB; tingkat getaran mesin 3,84 mm/s2; dan kualitas hasil cacahan menjadi baik yaitu plastik terpotong. Kata kunci: modifikasi, kinerja, sampah, daur ulang, mata pisau Abstract The plastic chopping machine is a machine designed to chop plastic waste in order to reduce the volume of waste. The chopping machine is designed to be able to chop waste with a chopping capacity of 50 kg / hour, the results of the chopping machine performance analysis show that the chopping machine capacity is 36.68 kg. Other engine performance analyzes are: the engine efficiency is 73.37%; noise level reaches 80.6 dB; The vibration generated during the counting was 4.9 mm / s2, and the chopping yield was 73.45%. The results of the performance analysis show that the chopping machine needs to be modified to match the results of the initial design. Modifications were made by changing the filter, resetting the distance between the blades, and adding blades to the rotary knife. The modifications made were successful in increasing the capacity of the chopping machine to 42.59 kg / hour; noise level to 76.8 dB; machine vibration level 3.84 mm / s2; and the quality of the chopped results is good, namely the plastic is cut. Key words: modification, performance, waste, recycling, blade

Daily performance of a solar hybrid regenerative gas turbine in Colombia

This work presents the evolution of the operation of a regenerative hybrid solar gas turbine in an average day of the year. The system is evaluated by means of a thermodynamic model that includes a solar concentrated heliostat field solar concentrator with central receiver, a combustion chamber, and the thermal engine. The model is applied in Barranquilla, Colombia using local temperature and the solar radiation estimated with a theoretical model. Power output, the global efficiency and thermal engine efficiency are estimated. Additionally, to estimate the temperatures in different states of the cycle with and without regenerator. Finally, the impact of the regenerator is evaluated, which can increase the temperature of the solar receiver by up to 13.6%, and the inlet temperature to the combustion chamber increases by 17.3% at noon, when solar radiation is maximum.

Comparative analysis of Unity and Unreal Engine efficiency in creating virtual exhibitions of 3D scanned models

The main purpose of this work was to compare two game engines (Unreal Engine and Unity) in creating virtual exhibitions. The article is a scientific description of a test of their efficiency. For the needs of the research two identical test applications built on the basis of the same assets were created. Those applications enabled researchers to examine and compare the efficiency of engines in question, as well as familiarizing themselves with the workflow on each platform. The comparative analysis of gathered data let more effective solution to emerge, which happens to be Unity engine.