Combustion Chamber Surface Research Articles

On convection vive in mixing-controlled combustion with thermal barrier coatings

Thermal barrier coatings (TBCs) could improve the efficiency of internal combustion engines by reducing heat losses. TBC modeling has demonstrated efficiency gains at all loads in compression ignition, including in gasoline compression ignition (GCI). However, after GCI testing of 13 coated pistons of various materials, thicknesses, and surface preparations in this work, a clear trend was observed: TBCs result in an efficiency gain at 6 bar IMEPn (low load) and an efficiency penalty at 15 bar IMEPn (high load). This can be explained by “convective vive”, which was originally presented by Woschni for engines with TBCs. Convection vive refers to a reduction in the quench distance of a reacting flame when the quenching surface temperature is elevated, resulting in an increased heat transfer coefficient and heat transfer rate despite the lower temperature difference between the gas and the wall. Although this work is unable to provide direct experimental evidence for convection vive, several experiments were performed to rule out alternate theories including differences in heat release rate, radiation heat transfer, combustion chamber deposits, and surface catalytic effects. Experiments also showed that at 6 bar IMEPn, injection pressure did not impact the performance of the TBC compared to the metal baseline, but at 15 bar IMEPn, the efficiency penalty increased with rail pressure. These results provide indirect evidence of convection vive: as the surface temperature of the TBC increases with load past a threshold, the quench distance decreases to the point where exothermic reactions can occur in the boundary layer, which raises the convective heat transfer coefficient. This implies that in mixing controlled combustion systems, the TBC should not be present on combustion chamber surfaces that experience high fuel-wall interaction during combustion.

Quantitative analysis of heat transfer characteristics and advantages in opposed-piston 2-stroke diesel engines

Opposed-piston 2-stroke diesel engines (OP2S) have lower combustion chamber surface-area-to-volume ratio, resulting in lower transfer loss but also excessive surface temperature. Investigation of combustion parameters on heat transfer, which provide a chance in improving combustion efficiency and solving surface overheating issue in OP2S at the same time, is yet to be undertaken. In this paper CFD simulation by CONVERGE software has been carried out to study heat transfer advantages in OP2S. Effect of initial swirl ratio and injection phase on combustion efficiency and heat transfer of combustion chamber surface area is investigated. Results show that OP2S has obtained peak combustion efficiency of 0.97, which is 0.02 higher than that of conventional diesel engine (4S). Also, combustion efficiency loss due to undesirable swirl ratio is only 20 % of 4S. Lowest heat transfer ratio achieved by OP2S is 0.045 of fuel energy, which is 34 % lower than that of 4s. However, heat transfer ratio of cylinder wall in OP2S is at least twice of that in 4S, and increase significantly with swirl. Unable to utilize squish, OP2S would suffer from at most 0.1 lower combustion efficiency compared to 4S when injection is retarded to TDC. Heat transfer ratio in OP2S is less sensitive to variation of injection phase, and stays at least 0.01 lower than 4S for all injection phase studied. In conclusion, OP2S achieved higher combustion efficiency while significantly cutting heat transfer loss compared to 4S at optimized swirl ratio and injection phase, proving its potential as a high-efficiency power source. Thermal load issue on cylinder wall in OP2S can be fixed by lowering swirl ratio. Reducing heat transfer loss in OP2S with delayed injection is undesirable, however, since combustion efficiency would suffer.

A two-material thermal barrier coating spatially tailored for high-efficiency GCI combustion

Continued research into thermal barrier coatings (TBCs) for internal combustion engines has generated insights into the design of TBCs that can increase fuel conversion efficiency. In this work, two low thermal inertia TBCs (a commercially available Gen 1 material, Gadolinium Zirconate, and a proprietary Gen 2 material) were experimentally tested in gasoline compression ignition (GCI) on a light-duty single cylinder research engine. Compared to a metal baseline, a 250-micron thick Gen 1 coated piston produced an efficiency benefit of 0.4 percentage points (pp) at 6 and 10 bar net indicated mean effective pressure (IMEPn) and a 0.2 pp penalty at 15 bar IMEPn. The Gen 1 coating also showed an uHC and smoke penalty. An 80-micron thick Gen 2 coated piston showed an efficiency benefit of 0.9 pp at 6 bar IMEPn and 0.4 pp at 10 bar IMEPn, but an efficiency penalty of 0.5 pp at 15 bar IMEPn. The Gen 2 coating, which has a lower thermal inertia than the Gen 1 coating, displayed durability problems while the Gen 1 coating did not. A third piston was coated with a 120-micron thick Gen 2 coating everywhere except the high failure outer bowl region, which was coated with a 120-micron Gen 1 coating. This hybrid coating displayed good durability, an uHC emission penalty, a smoke benefit, an efficiency benefit of 0.1 pp at 6 bar IMEPn, an efficiency benefit of 0.4 pp at 10 bar IMEPn, and no change in efficiency at 15 bar IMEPn. These results indicate that a durable Gen 1/Gen 2 coating can provide an efficiency benefit to GCI combustion, and that further improvements on piston-spray interaction optimization and surface sealing of the TBC, as well as increasing the coated combustion chamber surface area (e.g. head and valves) can add further improve efficiency.

Thermodynamic analysis of heat transfer reduction in spark ignition using thermal barrier coatings

This work uses a 0D thermodynamic engine model coupled to a 1D surface temperature solver to study the potential of low thermal inertia thermal barrier coatings (TBCs) on combustion chamber surfaces to increase the efficiency of spark ignition engines. Under ideal conditions, coating the piston crown, head, and valve faces with a TBC with a thermal inertia of 640 J/m2 K s1/2 resulted in less than a 1% relative improvement in efficiency. Despite using a low thermal inertia coating to avoid open cycle charge heating, the reduction in closed cycle heat transfer, which is the pathway to increasing efficiency, increased knock propensity. Therefore, any efficiency gain through closed cycle heat transfer reduction in spark ignition is offset by the need to retard spark timing to counter knock. An exergy analysis of completely blocking heat transfer for a 10 crank-angle degree window showed that on a low compression engine, like those used for stoichiometric gasoline spark ignition, the maximum efficiency gain achievable was limited compared to a higher compression ratio engine. Furthermore, the high gas temperatures of stoichiometric operation mean that even state-of-the-art TBCs cannot elevate surface temperatures enough purely through temperature swing to achieve a significant reduction in heat transfer near top dead center, where work availability is highest. Overall, these results indicate that low thermal inertia TBCs are ill-suited for achieving an efficiency benefit in spark ignition through a heat transfer reduction pathway. Instead spark ignition TBC research should explore ways to use low thermal inertia TBCs to achieve open cycle charge cooling to reduce knock propensity.

Exploration of low heat rejection engine characteristics powered with carbon nanotubes-added waste plastic pyrolysis oil

Compression ignition (CI)-powered alternative energy sources are currently the main focus due to the constantly rising worldwide demand for energy and the growing industrialization of the automotive sector. Due to their difficulty of disposal, non-degradable plastics contribute significantly to solid waste and pollution. The waste plastics were simply dropped into the sea, wasting no energy in the process. Attempts have been made to convert plastic waste into usable energy through recycling. Waste plastic oil (WPO) is produced by pyrolyzing waste plastic to produce a fuel that is comparable to diesel. Initially, a standard CI engine was utilized for testing with diesel and WPO20 (20% WPO+80% diesel). When compared to conventional fuel, the brake thermal efficiency (BTE) of WPO20 dropped by 3.2%, although smoke, carbon monoxide (CO), and hydrocarbon (HC) emissions were reasonably reduced. As a result, nitrogen oxide (NOx) emissions decreased while HC and CO emissions marginally increased in subsequent studies utilizing WPO20 with the addition of 5% water. When combined with WPO20 emulsion, nanoadditives have the potential to significantly cut HC and CO emissions without impacting performance. The possibility of incorporating nanoparticles into fuel to improve performance and lower NOx emissions should also be explored. In order to reduce heat loss through the coolant, prevent heat transfer into the cylinder liner, and increase combustion efficiency, the thermal barrier coating (TBC) material is also coated inside the combustion chamber surface. In this work, low heat rejection (LHR) engines powered by emulsion WPO20 containing varying percentages of carbon nanotubes (CNT) are explored. The LHR engine was operated with a combination of 10 ppm, 20 ppm, and 30 ppm CNT mixed with WPO20. It was shown that while using 20 ppm of CNT with WPO20, smoke, hydrocarbons, and carbon monoxide emissions were reduced by 11.9%, 21.8%, and 22.7%, respectively, when compared to diesel operating in normal mode. The LHR engine achieved the greatest BTE of 31.7% as a result of the improved emulsification and vaporization induced by CNT-doped WPO20. According to the study's findings, WPO20 with 20 ppm CNT is the most promising low-polluting fuel for CI engines.

Analytical solution of unsteady heat conduction in multilayer internal combustion engine walls

An analytical solution of the unsteady heat conduction problem in multilayer walls was developed and applied to study thermal barrier coatings for reciprocating internal combustion engines. The mathematical solution was derived using the matrix method and complex analysis/residue-calculus Laplace transform inversion techniques. The one-dimensional domain includes a time-varying heat flux on the combustion chamber surface, and a time-varying temperature on the backside coolant surface. These boundary conditions are simulated as the superposition of two adjacent triangular, unit-magnitude pulses, which gives a piece-wise linear representation of the applied flux or temperature history. The temperature at any location of interest is found as the convolution of the transfer function, which results from the inversion, with the discrete-time heat flux or backside temperature history. The transfer functions describe the exact response and only depend on multilayer architecture, therefore, they can be computed a priori. The triangular pulse method provides a more than two order of magnitude reduction in computation time compared to a finite difference solution at the same level of accuracy. A 104-fold speed increase relative to a finite difference solution was realized when using the Overlap-add convolution technique for a full drive cycle simulation, i.e., a long time record. The surface response or transfer function acts like a finite impulse response and can be viewed in the frequency domain to reveal complementary information about coating performance.

A combined Combustion-Conjugate heat transfer analysis for Design of partially insulated pistons

Insulating engine combustion chamber surfaces with thermal barrier coatings (TBCs) provides engine thermal efficiency improvement by reducing the heat transfer to the coolant when done appropriately. However, reducing heat losses using traditional ceramic insulation increases combustion chamber wall temperatures during the whole engine cycle, including intake stroke resulting in a decreased engine volumetric efficiency due to excessive intake air heating. This paper presents the concept of partial insulation coverage on a selective area of combustion chamber wall by simulations to improve the engine's thermal efficiency. A combined combustion–conjugate heat transfer analysis methodology was developed to determine the partial-coverage insulation area by analyzing the heat flux and surface temperature distribution across the combustion chamber wall. Engine cycle simulations were run to compare the engine performance with various partial insulation designs, and an optimal insulation area was proposed. To validate the simulation results, the full-coverage coated piston technology with 0.5 mm thick Yttria Stabilized Zrconia (YSZ) coating has been experimentally evaluated on a prototype engine and compared to the non-insulated baseline aluminum piston. It was found that the partial coverage insulation showed a thermal efficiency improvement of 1.98% relative to a full-coverage insulated piston efficiency of 2.06%.

Waste plastic oil to fuel: An experimental study in thermal barrier coated CI engine with exhaust gas recirculation

AbstractThe disposal of waste plastic has intensified into a massive environmental crisis. A sound disposal technology may be extremely expensive or complex in operation. As a result, experts are investigating alternative methods of recycling waste plastic. Waste plastic oils (WPO) are gaining interest as a replacement for petroleum‐based fuels since they can deliver substantial performance while having a low environmental impact. The goal of this research is to look into the use of WPO in a retarded timing (RT) engine with a partially stabilized zirconium combustion chamber surface (PSZ). In addition, Exhaust Gas Recirculation (EGR) augmentation was used to realize WPO performance fully. With 20% EGR, the engine's thermal efficiency increased by 6.33%, along with the significant reduction of NOx. However, CO, HC, and smoke particle emissions increased by 4.56%, 5.76%, and 3.54%. More research on the sustainability aspects of the WPO is required before considering it as a fuel for the transportation sector.

Direct Improvement in the Combustion Chamber and the Radiant Surface to Reduce the Emission of Particles in Biomass Cooking Stoves Used in Araucanía, Chile

Solid particle emissions from burning wood in three internal combustion biomass cooking stoves commonly used in southern Chile were compared. Each stove was used to show differences in sealing systems, combustion chamber shape, and heating surfaces in order to optimize biomass combustion and the energy produced at a low manufacturing cost. The influence of cooking stove design along with particle and gas emissions that resulted from the biomass combustion within the cooking stove was investigated in this study. Levels of diverse atmospheric contaminants, such as particulate matter, emission factor, NOx, CO2, and CO, and the temperature of the flue gases were determined with the Ch-28 method and UNE-EN 12815. The average emission of particulate matter was significantly reduced by modifying the geometry of the combustion chamber and heating surface of each stove, resulting in 5 g/h particle emissions in conventional equipment and 2 g/h in the improved equipment. In relation to gas emissions, there was a 25% maximum decrease in NOx gases and 35% in CO after modifying the heating surface of each stove. This background supports the evidence of technological improvement with high environmental impact and low economic cost for local manufacturers.

On Optical Semi-Quantitative Spectral Study of Low-Speed Pre-Ignition Sources in Spark Ignition Engines

<div class="section abstract"><div class="htmlview paragraph">Low-Speed pre-ignition (LSPI) in modern-day, heavily downsized, boosted, and direct-injection spark ignition (SI) engines is a well-known problem. Several mechanisms contribute towards stochastic pre-ignition (SPI), the most prominent being crevice material droplet induced and deposit induced pre-ignition mechanisms. The droplet mechanism is typically dominated by the detergent additives present in the lubricant formulation; more specifically calcium and sodium-based detergent additives correlate strongly with the increased LSPI rates. Deposits flaking off the combustion chamber surfaces can also induce LSPI under certain conditions.</div><div class="htmlview paragraph">This study aimed to develop an optical method designed to investigate the nature of pre-ignition precursors. Southwest Research Institute (SwRI) utilized an optically accessible GM 2.0 L LHU engine to study the pre-ignition phenomenon and studied the nature of pre-ignition precursors using spectral information from one of the cylinders in this engine. A custom, simplified borescope was employed to gather visible light from the combustion chamber to detect the glowing pre-ignition precursors. Further, this light signal was sent to an array of four photomultiplier tube (PMT) detectors which were tuned to visible light emission wavelength bands of interest. Three of the four wavelengths (555, 623, 645 nm) were selected to be representative of calcium and CaOH while the fourth wavelength of 715 nm (red emission) was selected to be representative of glowing soot-like aggregates. A high calcium first-generation Dexos™ 1 compliant oil with moderate LSPI activity was used in this study. The analysis revealed that the precursors contained both the signals for calcium as well as the deposit wavelengths in different proportions. More specifically, it was observed that in a series of LSPI events, the first event was usually more biased towards calcium wavelengths suggesting a pre-ignition initiated by the droplet ejecting from the crevice. A relative semi-quantitative metric was developed to compare the light signals for different frequencies to further delve into the pre-ignition mechanism. Two additional fuels were tested with different particulate matter index (PMI) values to assess the impact of PMI on pre-ignition precursors. A bulk comparison of around 30,000 combustion cycles of the two additional test fuels revealed that the high PMI fuel showed more bias towards a deposit induced mechanism while the lower PMI fuel exhibited signs of both droplet and deposit induced pre-ignition precursors.</div></div>

Trace elements microanalysis of metal oxides in deposit formed on combustion chamber surface of landfill gas engine using focused ion beam/scanning electron microscopy technique

The aim of this study is to investigate the deposit formed on the inner surface of the combustion chamber of the landfill gas engine based on its morphological structure and elemental composition. The responsible elements for deposit formation that affects the engine's operating performance were determined on the differences of the microstructural and chemical composition of deposits using Scanning Electron Microscope with Energy Dispersive Spectrometry and Focused Ion Beam. The Oxygen element of metal oxides made up about half of the deposit mass. Nitrogen was also detected in the deposit by FIB analysis. The amount of elements on the bottom surface to the engine part were ordered Si > S > Ca > Al > Mg > Sn > Sb, on the other side, the elements on the top surface of the accumulated deposit were Ca > S > Si > Sn. The elemental distribution of the top surface was overlapped with both results of the elemental distribution of the longitudinal lateral section area and the cross-sectional area. The amount of Si increased from the top surface to the bottom surface, and the amount of Ca and S decreased. These findings revealed that Si, S, and Ca have various roles in deposit formation from start to end. WDXRF Spectrometer analysis confirmed that Si, S, and Ca are the major elements with approximately half of the deposit is made up of oxygen element. The detected Sb and Sn made the deposits to be considered as hazardous material in the disposal process.

Specific features of n-decane vapors self-ignition in air at temperatures of 600–800 K

Experiments of n-decane/air self-ignition at the temperature range 600–800 K were carried out by rapid compression machine. It allowed obtaining temperature-concentration limits of transition from single-stage to two-stage ignition. High-speed video recording has let established that hot stage ignition always initiates near the piston surface or quartz window. These locations depend on gas temperature. Combustion of the test mixture occurs in the entire volume after that. Couple sequential photos of cool flame shows that it starts same near piston surface and has a complicated volumetric structure caused by the roll-up gas vortex. It is shown that partial n-decane pressure increasing during compression causes the non-equilibrium condensation process near the inner surfaces of combustion chamber. This leads to significant redistribution of n-decane concentration and determines local characteristics self-ignition of n-decane/air mixture.

Piston Crown Profile Modifications for Various Combustion Mode Strategies of Modified GDI Engine towards NOx and PM Reduction

In the current development of automotive engines, the major target is to design a combustion chamber in such a way that the combustion process must provide very less concentrations of emissions. To satisfy current worldwide emission norms, petrol engines also equipped with direct fuel in-jection (gasoline/petrol directly injected into engine cylinder) same as like diesel engines. The main drawback of GDI engine is NOx and PM emissions due to lean burn combustion and rich mixture formation over the combustion chamber surface because of wall wetting. In GDI engines, the gasoline fuel injector is placed at various positions with different angles over an engine cylinder head as per the mode of combustion strategy. Based on the mode of combustion with fuel injection angle, the piston crown shape design in much important that the crown surface must not involved in wall wetting during injection. The piston crown shapes were modified for Spray guided combustion mode, Wall guided combustion mode and Air guided combustion mode by keeping in mind that the position of injector with fuel spray angle and the position of spark plug tip on the cylinder head. The main aim of modifying the crown surface profiles of piston is to impart swirl and squish effects for better mixing of air and injected fuel, maintain combustion chamber surface temperature range within the limits and also to avoid wall wetting results in chances of reducing soot particle/PM emission and NOx emission from combustion process.

Enhancing the efficiency benefit of thermal barrier coatings for homogeneous charge compression ignition engines through application of a low-k oxide

Prior experiments reported by the authors have proven the hypothesis that achieving a dynamic temperature swing on the combustion chamber surface will lead to improved thermal and combustion efficiencies of the homogeneous charge compression ignition engine. A thin layer of yttria-stabilized zirconia, roughly 150 μm, was plasma sprayed on the piston top. It led to markedly advanced ignition and heat release in the gasoline homogeneous charge compression ignition engine, accompanied with reduced unburnt hydrocarbon and carbon monoxide emissions, improved combustion efficiency, and a higher thermal efficiency. A related computational study highlighted the critical role of coating thermal conductivity in achieving a desired dynamic response; hence, the second phase of experimental investigations focused on introducing structured porosity in the yttria-stabilized zirconia coating, as a means of reducing effective conductivity. Indeed, additional incremental improvements were observed, as well as limitations related to adverse effects of the surface roughness and the fuel interactions with the surface roughness and open pores. Erosion can also be a problem in a direct injection engine. Therefore, the third round of investigations focused on a material with a natively low conductivity (low-k), sprayed on the top of an Al piston in a relatively dense form, and in a way that yields a smooth surface. The objective was to capitalize on the low conductivity, while avoiding the pitfalls accompanying high-porosity formulations. The heat-storage capacity was limited by keeping the thickness relatively low. The results verify the paramount importance of thermal conductivity in the context of high “temperature swing” behavior and indicate a potential to improve the homogeneous charge compression ignition engine’s combustion efficiency roughly 1.5%, with the overall indicated efficiency improvement on the order of 5%, on a relative basis. In addition, the low-k oxide thermal barrier applied to the piston extended significantly the low-load homogeneous charge compression ignition operability limit.

Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures

Liquid-fueled combustion systems demand optimal performance over a range of operating conditions—requiring predictable fuel injection events, spray breakup, and vaporization across a range of temperatures and pressures. In direct injection combustors, these sprays impinge directly on combustion chamber surfaces. Although the outcome of fuel droplets impacting a wall is primarily driven by the wall temperature and the Leidenfrost effect, the shifting liquid-vapor saturation point with pressure may influence the droplet-wall heat transfer rate and transition from nucleate to film boiling. In this paper, the role of ambient pressure on the droplet impact regimes, spreading rate, and droplet rebound velocity during impact are explored for representative low boiling point and high boiling point pure hydrocarbon liquids (n-heptane and n-decane). High-speed image sequences of the drop-wall impact were acquired for ambient pressures of 1–20 bar and wall temperatures ranging from 35–300 ∘C with a drop Weber number of ~ 50. Droplet impact sequences were recorded using a high-speed CMOS camera and were processed to measure the droplet spread, droplet rebound velocity and track the droplet centroid motion. The dynamics of the drop spreading and rebound show similar behavior across a range of ambient pressures with the largest differences observed for wetted versus non-wetted cases (above the Leidenfrost temperature). For both fluids, the onset of drop rebound remains bounded by the saturation temperature (shifting with ambient pressure) and the thermodynamic limit of liquid superheat. This leads to a decrease in the superheat temperature above the saturation point as the critical pressure is approached.

Energy efficiency of automotive gasoline engine: current approaches

Introduction. To meet the promising requirements fuel consumption and CO 2 emissions of passenger cars and commercial vehicles of 2025-2030 further improvement of the design and workflowof a gasoline internal combustion engine (ICE) is required in the full range of the working map, especially at high loads. The purpose of the study was to review and analyze ways to improve the indicator efficiency of a gasoline ICE and approaches aimed at increasing efficiency by reducing heat losses. Methodology and research methods . The review of barriers to increasing the indicator efficiency of a gasoline ICE was based on the analysis of the ideal and real Otto cycle and the results of experimental and calculated foreign and domestic studies of recent years aimed at increasing fuel efficiency by reducing heat losses. Scientific novelty and results . It was shown that effective new approaches to reduce the heat losses of the ICE of the future were: organization of combustion of a stoichiometric mixture diluted with a large amount of cooled recirculated exhaust gases (up to 25-35%) at high loads; increasing the ratio of the piston stroke to the cylinder diameter S/D to a value of the order of 1.5; the use of thin thermal barrier coatings that provide a “temperature swing” of the combustion chamber surface. Combined with proven modern technologies (direct fuel injection, variable valve drive, etc.), they can significantly increase the optimal geometric compression ratio, significantly reduce heat loss to the walls of the combustion chamber and the tendency of the ICE to detonate, and provide an increase in the indicator efficiency up to 49-53%. The practical significance lies in the possibility of using the results of the work when choosing a scheme and design solutions for a promising gasoline ICE with reduced fuel consumption and CO 2 emissions.

An experimental investigation on a low heat rejection diesel engine using waste plastic oil with different injection timing

The disposal of waste plastic solids are becoming more than a crisis with respect to environmental safety. Proper disposal system may either be very expensive or leads to side effect. Hence researchers are looking for suitable methods to reuse them. Oils as substitute for petroleum products in internal combustion engines are gaining focus in India, because of its potential to generate large scale employment and relatively low environmental poverty. The present work aims at utilizing this waste plastic oil in a low heat rejection retarded timing engine whose combustion chamber surface is coated with partially stabilized zirconia (PSZ) ceramic. The influence of fuel injection timing was studied to completely understand the waste plastic oil performance in low heat rejection engine. The results revealed great improvement in performance, and emission characteristics. As a compensation, NOx formation was slightly increased. Overall performance of the low heat rejection engine with waste plastic oil fuel was better with 14⁰ bTDC retarded injection time.

Combustion in Circulating Fluidized Bed: Competitive Technology for the Coal-Fired Power Industry

The object of the study is the circulating fluidized bed (CFB) steam generator BKZ 500–13.8 using an off-specification fuel (anthracite screenings of the Listvyanka coal field in the Novosibirsk region). The purpose of the study is to apply the zone method of calculation of the basic elements of the CFB steam generator when switching to a new fuel. The calculations determined the geometric characteristics of the combustion chamber and heating surfaces (zones of the superheater, economizer, and air preheater). The most important indicators of the CFB steam generator operating on anthracite culm were found: boiler efficiency of 92.42%, anthracite consumption of 14.4 kg/s, sulfur oxide emissions of 22.2 kg/s, and nitrogen oxide emissions of 12.8 kg/s. This steam generator can operate on the lowest-grade fuels with minimum environmental damage.

EFFECT OF IN-СYLINDЕR CATALYSIS IN DIESEL ENGINES

On the basis of analysis of the features of intra-cylinder catalysis during the coating of the combustion chamber surface by the catalytic layer, of combustion kinetics and experimental studies, an attempt was made to disclose the mechanism of positive fuel-ecological effects in diesel engines with direct injection of fuel. Acceleration of catalytic reactions is ensured by adsorption of reagents on the surface of the catalyst, action on the force field of the catalyst and on active particles. Enhancement of the catalytic effect can be achieved by changing the properties of the catalyst, coating technology, the optimal combination of the velocity of the charge, the angle of dispersion of the fuel jet and the shape of the combustion chamber. The characteristics of the heat release rate determined as a result of processing the indicator diagrams of a single-cylinder diesel engine when working with a uncoated piston and with a piston having a catalytic coating on the surface of a MnxOy-based chamber allowed to confirm the positive catalysis effect and determine the combustion periods at which this effect manifests itself.

Heat Transfer Correlations on Combustion Chamber Surface of Diesel Engine - Experimental Work

Design and control of recently developing engines have much important towards better fuel economy and reduction in exhaust emissions from an engine. Since the ignition takes place due to high compression (or) self ignition of temperature in case of diesel engines, the temperature distribution and heat flux on the combustion chamber surface are an important phenomenon. While modifying the profile of combustion chamber of diesel engine, it is important to relocate the hot spot regions on the combustion chamber surface which supports combustion initiation. With these hot spot regions on combustion chamber surface regulates/controls ignition delay period which results in controlled detonation. In diesel engines, controlled detonation which in turn improves engine performance and reduced emissions. Therefore, to include the hot spot regions at proper locations, it is required to measure the temperature values at different locations/coordinates with the help of thermocouples on the cylinder head surface exposed to combustion chamber. Also the adiabatic flame temperature, the engine performance parameters, heat balance date, convection and radiation heat transfer related terms were calculated and analyzed