ГАЗОДИНАМИКА УСТОЙЧИВОГО ГОРЕНИЯ В КАМЕРЕ СГОРАНИЯ ГАЗОТУРБИННОЙ УСТАНОВКИ С ВНЕШНИМ ПОДОГРЕВОМ КОМПОНЕНТОВ

One of the rational ways of creating low-emission combustion chambers is the organization of low-temperature lean combustion with external heating of the components before they are fed into the combustion chamber. When organizing lowtemperature lean combustion with large excess air ratios, problems may arise with ensuring a stable position of the flame front. Combustion stability to a large extent depends on the ratio of the average flow rate and the rate of turbulent combustion. The rate of turbulent combustion depends on the composition, pressure and temperature of the components supply and the degree of turbulence in the combustion chamber. The average flow rate depends on the excess air ratio (oxidizer and fuel consumption) and the geometric dimensions of the chamber. Earlier it was shown that when developing a low-emission combustion chamber with low-temperature lean combustion, it is advantageous to use the relative flow rate as a generalized characteristic of the intra-chamber process, which takes into account the consumption, geometric and thermodynamic parameters in the combustion chamber. This work is devoted to the analysis of stable combustion of a fuel composition natural gas + air based on the experimental data available in the public domain by the authors from the University of Michigan (USA). With the help of the methods developed by the authors, the experimental data on the limiting feed rates of the components into the atmospheric burner were processed. The limiting flow rates of air and natural gas, the limiting values of the excess air ratio, the longitudinal values of the speed of the fuel-air mixture and the limiting values of the relative flow rate are obtained and analyzed. Areas of stable combustion by the listed parameters at different degrees of air swirl are graphically presented.

Low temperature combustion (LTC) is an advanced mode of combustion that has attained much attention due to ever increasing emission standards. LTC simultaneously reduces soot and nitric oxide (NO) emissions by having combustion take place at, for example bulk gas temperatures below 1200K (as observed in this study) so that soot and NO formation is substantially reduced. Soot is typically considered a building block for particulate matter (PM); both PM and NO are heavily regulated emissions by government agencies due to their potential effects on human and environmental health. Although LTC is believed to substantially reduce soot, it is not clear what is the end effect on PM. Because PM is composed of other agents, such as condensed liquid and solid hydrocarbons, there could potentially be non-negligible emission of PM from LTC combustion. This study will compare the gravimetric-based PM data from 3 different modes of combustion in a direct injection diesel engine; specifically: conventional combustion, combustion with high exhaust gas recirculation (EGR) at conventional injection timing, and combustion with high EGR and late injection timing (all other control parameters are the same, including fuel flow rate and engine speed). The objective of this study is to quantify PM emissions of LTC and assess potential differences relative to the soot concentration (the latter as assessed by a smokemeter). PM is gravimetrically measured using a mini-dilution tunnel. Further, chemical analysis of the collected PM is analyzed by an independent laboratory to develop an understanding of the constituent species composing conventional and LTC PM. PM results show that there are differences among the three modes of combustion. The PM differs in appearance as well as composition, and due to the change in appearance FSN may not correlate with PM when running LTC modes of combustion.

Combustion and emissions performance of a hybrid hydrogen–gasoline engine at idle and lean conditions

To establish normal reference ranges of urinary flow rates in children. From a screening programme, 200 healthy children (96 girls and 104 boys, between 3 and 18 years old) with no renal, urological, psychological or neurological disorders were selected, and they provided 433 micturitions for analysis. The children were divided into those with body surface areas of < 0.92 m2, between 0.92 and 1.42 m2 and > 1.42 m2. The voided volume, maximum and average flow rates of urine were measured. Data were fitted by several mathematical functions and goodness-of-fit determined. The relationship between maximal or average flow rates and voided volume was best fitted by a logarithmic function. The maximal and average urine flow rate nomograms are given in centile form for each body surface area group in both girls and boys. Flow rates showed a close relationship with voided volumes in both sexes and for all body sizes. The average maximal and average flow rates were higher in girls than in boys. Normal nomograms of maximal and average urine flow rates of girls and boys at three different body surfaces are presented in centile form. These may be useful for diagnosing lower urinary tract disturbances in children over a wide range of body size and voided volumes.

Thermal efficiency and emissions improvement of the lean burn high compression ratio HPDI NG engine at different combustion modes

Performance and emission characteristics of an IC engine under SI, SI-CAI and CAI combustion modes

The collection efficiency is the major indicator for the evaluation of the pollution rate and the environmental performance of the aluminium electrolysis process. This efficiency is proportional to the flow rate of the released gases at the chimney. Since December 2009, the normal flow rate has being decreasing and fluctuating in the Alucam smelting factory. At the Analysis step of the DMAIC methodology, the fundamental causes of the variations and the decrease in the gas normal fume flow rate were identified in a previous study. We intend here to stabilize the flow rate, to Improve the efficiency and to put into place a reliable mechanism of Control in order to maintain target variables within Six Sigma limits. Therefore, we propose an appropriate model of the pipeline network which permits us to identify the causes of the process low capability by excluding the interpretation controversy of the relation between the stopping of pots and the decrease in the fume collection and treatment installation. Then, we choose to achieve the modulation of the suction fan to adapt to changes in system load, and the replacement of the fan impeller to reach the continuous regulation of the flow rate. Benefits cannot be over emphasized because the company may improve on its collection and treatment efficiency, hence an effective reduction of dangerous gaseous fluoride emissions.

To meet current emission regulations and increasingly demanding global fleet CO2 standards on fuel economy and future trends towards life cycle GHG emissions, advanced combustion engines remain significant in the passenger vehicle sector to achieve high efficiency and low emissions over the full operating range. Lean burn gasoline compression ignition (GCI) technology has shown to have the most potential in reaching these goals, although it faces challenges in the operating range. In this study, an advanced GCI engine is considered with the capability to operate under two combustion modes, namely low temperature combustion (LTC) and GCI. They are enabled with the use of two Hyundai in-house developed technologies; an advanced valve control mechanism known as continuously variable valve duration (CVVD) and a high-pressure gasoline injection system. At low load, the engine utilizes dual CVVD and dual CVVT (continuously variable valve timing) mechanisms for both intake and exhaust valvetrains to enable NVO (negative valve overlap) to trap hot residuals. The hot residuals enable low load auto-ignition, and the phasing control of that auto-ignition is achieved by varying the degrees of NVO, and in turn, the amount of hot residuals. This is done in real time with respect to the changes in engine loads or operating conditions, significantly improving cylinder-phasing control in LTC mode, and subsequently is able to realize a fuel economy gain and reduced emission benefits. Early direct injection during NVO or intake stroke is used to form homogenous or quasi-homogenous air–fuel mixture for LTC. At mid to high loads, late direct injection of gasoline or GCI mode is employed to take advantage of the high volatility and high resistance to auto-ignition of gasoline fuel, so that diesel-engine like high combustion efficiency can be achieved with lower soot emissions for the same NOx level as diesel combustion. In this paper, the key control and fueling technologies that enable this multiple mode combustion are introduced, and the resultant analysis on engine test and CFD simulation at LTC and GCI operating conditions are presented in detail.

This experimental work studies a small-scale biomass combustor (5–12 kW) with an underfed fixed bed using low air staging ratios (15%–30%). This document focuses on the influence of the operative parameters on the combustion process, so gaseous emissions and the distribution and concentration of particulate matter have also been recorded. The facility shows good stability and test repeatability. For the studied airflow ranges, the results show that increasing the total airflow rate does not increase the overall air excess ratio because the burning rate is proportionally enhanced (with some slight differences that depend on the air staging ratio). Consequently, the heterogeneous reactions at the bed remain in the so-called oxygen-limited region, and thus the entire bed operates under sub-stoichiometric conditions with regards of the char content of the biomass. In addition, tests using only primary air (no staging) may increase the fuel consumption, but in a highly incomplete way, approaching a gasification regime. Some measured burning rates are almost 40% higher than previous results obtained in batch combustors due to the fixed position of the ignition front. The recorded concentration of particulate matter varies between 15 and 75 mg/Nm3, with a main characteristic diameter between 50 and 100 nm.

&lt;div class="htmlview paragraph"&gt;This paper describes the optimization process of a small single-cylinder research HSDI diesel engine, starting from a conventional combustion towards split-injection low-temperature combustion.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;Targets for emissions, fuel consumption and combustion noise are defined with the characteristics of low temperature combustion in mind, in other words, high CO, HC and combustion noise but low soot and NO&lt;sub&gt;X&lt;/sub&gt;.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;In this investigation the targets are defined for a medium-load working modes of a typical small four-cylinder turbo-charged diesel engine, equipped with a particulate trap and oxidation catalyst. They are introduced into an objective target function which is a guide for the optimization process.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;The statistical optimization procedure used is the method of consecutive screenings. With this methodology, six factors are optimized: mass distribution of the fuel injection pattern, injection pressure, combustion phasing, EGR rate, boost pressure and dwell time between injection events.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;For each consecutive screening round, a response surface of the objective target function is built which is optimized with a steepest ascent method. The optimum serves to define the next screening round. The final optimum settings are characterized by a late split-injection and a high EGR rate. The two injection events lead to two auto-ignition delay events, resulting in a highly premixed combustion. This combustion mode is characterized by very low levels of nitrogen oxides (10∼15 ppm) and low combustion noise at reasonable fuel consumption, soot, HC, and CO emission.&lt;/div&gt;

State of the art of NOx mitigation technologies and their effect on the performance and emission characteristics of biodiesel-fueled Compression Ignition engines

CFD analysis of combustion and emission characteristics of biodiesel under conventional and late-injection based premixed combustion conditions

Experiments and CFD-analysis of vaneless diffusers demonstrate that in wide range of relative width there is a risk of flow separation at design flow rate as a flow angle after an impeller is too small. To avoid it the inlet part of a diffuser is made with decreasing width along radius. By the elementwise calculation the diffuser with relative width about 2%, narrowed initial part and conical surfaces with the divergence angle 30 between them is turned out to be the best variant of the considered.The diffuser within the stage with narrowed initial part and zero divergence angle has the highest efficiency when relative flow rates are less than design regime flow rate. The stage with diffuser with walls divergence angle 0045’ after narrowed part is less effective on 0.5% when relative flow rates are less than design regime. The maximum efficiency of this stage is 1.5% higher and efficiency is sufficiently higher at big flow rates.

Low-temperature combustion in diesel engines offers attractive benefits through simultaneous reduction in the nitrogen oxide emissions and the soot emissions. However, it is known that the in-cylinder conditions typical of low-temperature combustion operation tend to produce high emissions of unburned hydrocarbons and carbon monoxide, reducing the combustion efficiency. The present study develops from the hypothesis that this characteristic poor combustion efficiency is due to the in-cylinder mixture preparation strategies which are non-optimally matched to the requirements of the low-temperature combustion mode. In this work, the effects of three key fuel path parameters, namely the injection fuel quantity ratio, the dwell and the injection timing, on the carbon monoxide and hydrocarbon emissions were examined using a central-composite-design design-of-experiments method. The experiments were performed on a single-cylinder diesel research engine operating in a mixing-controlled low-temperature combustion mode at high and moderate exhaust gas recirculation rates with a split fuel injection for all conditions. The experiments identified the potential of fuel metering control for optimising the hydrocarbon emissions in low-temperature combustion by showing the effects of the fuel control parameters on the fuel mixing quality and the emission formation mechanisms. The response surfaces created from the detailed statistical analysis give a potent visualisation of the constraints on low-temperature combustion operation. This in turn allowed improved prescription of combustion modifications with the potential to moderate the negative effects observed.

Milking Responses of Cows Given Premilking Stimulation at Four Lactational Stages