Dual Mode NOx Sensor: Measuring Both the Accumulated Amount and Instantaneous Level at Low Concentrations

The accumulating-type (or integrating-type) NOx sensor principle offers two operation modes to measure low levels of NOx: The direct signal gives the total amount dosed over a time interval and its derivative the instantaneous concentration. With a linear sensor response, no baseline drift, and both response times and recovery times in the range of the gas exchange time of the test bench (5 to 7 s), the integrating sensor is well suited to reliably detect low levels of NOx. Experimental results are presented demonstrating the sensor’s integrating properties for the total amount detection and its sensitivity to both NO and to NO2. We also show the correlation between the derivative of the sensor signal and the known gas concentration. The long-term detection of NOx in the sub-ppm range (e.g., for air quality measurements) is discussed. Additionally, a self-adaption of the measurement range taking advantage of the temperature dependency of the sensitivity is addressed

Experimental and numerical study of using of LPG on characteristics of dual fuel diesel engine under variable compression ratio

In this work, an experimental and numerical investigation are carried out to study the impact of adding Liquefied Petroleum Gas (LPG) on the characteristics of diesel engine. New injection control system (ICS) is designed to manage an LPG injector on intake manifold a single-cylinder diesel engine. The engine test rig is powered with traditional diesel fuel to generate the base line data for comparison. Different conditions of load (0%, 25%, 50%, 75%, and 100%) in terms of brake power with three compression ratios of 14.5, 15.5 and 16.5 at constant engine speed of 1500 rpm. LPG is tested in four rates (5 L/min, 10 L/min, 15 L/min, and 20 L/min). The numerical analysis is performed with the help of Diesel-RK simulation software. The multizone combustion model is adopted. Same operating conditions in the experimental work are followed in the numerical simulation. The obtained results revealed that brake thermal efficiency (BTE) and exhaust temperature are reduced while brake specific fuel consumption (BSFC) is increased as the rate of LPG increased. Inducting LPG with (5,10,15,20) L/min reduced carbon monoxide (CO) by 16.6%, 14.7%, 20.3%, and 18.8% respectively. The maximum reduction in hydrocarbon emission (HC) is 8% at the rate of 15 L/min compared to diesel. The volumetric efficiency and NOx emissions are decreased with the use of LPG. As the compression ratio increases, BTE increases and BSFC decreases because of increasing combustion temperature and pressure which decreases delay period, ignites fuel fast and produces more power in small time. The impact of increasing compression ratio reported significant reduction in, CO, HC while NOx are increased. The experimental findings are compared to the results of the Diesel-RK software, as well as with the results of other researchers and good harmony among them is noticed

NOx uptake mechanism on Pt/BaO/Al2O3 catalysts

The NO (x) adsorption mechanism on Pt/BaO/Al2O3 catalysts was investigated by performing NO (x) storage/reduction cycles, NO2 adsorption and NO + O-2 adsorption on 2%Pt/(x)BaO/Al2O3 (x = 2, 8, and 20 wt%) catalysts. NO (x) uptake profiles on 2%\Pt/20%BaO/Al2O3 at 523 K show complete uptake behavior for almost 5 min, and then the NO (x) level starts gradually increasing with time and it reaches 75% of the inlet NO (x) concentration after 30 min time-on-stream. Although this catalyst shows fairly high NO (x) conversion at 523 K, only similar to 2.4 wt% out of 20 wt% BaO is converted to Ba(NO3)(2). Adsorption studies by using NO2 and NO + O-2 suggest two different NO (x) adsorption mechanisms. The NO2 uptake profile on 2%Pt/20%BaO/Al2O3 shows the absence of a complete NO (x) uptake period at the beginning of adsorption and the overall NO (x) uptake is controlled by the gas-solid equilibrium between NO2 and BaO/Ba(NO3)(2) phase. When we use NO + O-2, complete initial NO (x) uptake occurs and the time it takes to convert similar to 4% of BaO to Ba(NO3)(2) is independent of the NO concentration. These NO (x) uptake characteristics suggest that the NO + O-2 reaction on the surface of Pt particles produces NO2 that is subsequently transferred to the neighboring BaO phase by spill over. At the beginning of the NO (x) uptake, this spill-over process is very fast and so it is able to provide complete NO (x) storage. However, the NO (x) uptake by this mechanism slows down as BaO in the vicinity of Pt particles are converted to Ba(NO3)(2). The formation of Ba(NO3)(2) around the Pt particles results in the development of a diffusion barrier for NO2, and increases the probability of NO2 desorption and consequently, the beginning of NO (x) slip. As NO (x) uptake by NO2 spill-over mechanism slows down due to the diffusion barrier formation, the rate and extent of NO2 uptake are determined by the diffusion rate of nitrate ions into the BaO bulk, which, in turn, is determined by the gas phase NO2 concentrationclose333