LITERATURE SURVEY

Diesel engines are widely used for transport and power generation applications because of their high thermal efficiency, and their easy adoption for power generation applications as well. Increased impetus on improving diesel engine performance, with lower noise and vibration levels and lower emissions several techniques involving fuel/engine modifications are essential. Increased energy demand, diminishing fossil fuel reserves in the earth crust and harmful exhaust gases from engine tailpipe have focused major attention on the use of renewable and alternative fuels. To overcome and meet these requirements, use of renewable fuels such as biodiesels and bio-fuels for diesel engines has gained greater momentum. Hence implementing new methods that improve the efficiency of diesel engine for both transport and power generation applications are the need of hour. Renewable energy sources can supply sustainable energy for longer periods of time than their counterparts fossil fuels and have many advantages as well (Goldemberg and Coelhobn, 2004). Liquid biodiesels in particular are more suitable for diesel engine applications as their properties are closer to diesel. A number of vegetable oils have been used for biodiesel production and their respective biodiesels are used as alternative fuels in diesel engines. Biodiesels derived from jatropha, honge (karanja), honne, palm, rubber seed, rape seed, mahua, and neem seed oils were used in diesel engine applications (Banapurmath et al. 2008; Banapurmath et al. 2009; Bari et al. 2002; GajendraBabu et al. 2006; Karnwal 2010; Onga et al. 2011; Ramadhas et al. 2005, 2005; Raheman and Phadatare 2004; Sahoo et al. 2007, 2009; Venkanna and Reddy, 2011; Sundraapandian and Devaradjane 2010). Slightly reduced engine performance with increased emissions and poor combustion patterns were reported for biodiesels engine operation by several researchers (Banapurmath, et al. 2008; Banapurmath et al. 2009; Nwafor, 2000, 2003; Ramadas, et al. 2005; Scholl and Sorenson, 1993). Effect of various engine parameters such as compression ratio (CR), injection timing (IT), injection pressure and engine loading on the performance and exhaust emissions of a single cylinder diesel engine operated on biodiesel and their blends with diesel were reported in the literature (GajendraBabu 2007). Varying injection timings affect the position of the piston and thereby cylinder pressure and temperature at the injection provided. Retarded injection timings showed significant reduction in diesel NOx and biodiesel NOx (Hountalas et al. 2001; Tao et al. 2005). Cylinder pressures and temperatures gradually decreased when injection timings were retarded (Roy 2009). Experiments on CI engine using different vegetable oils and their esters at different injection pressures have been reported. Better performance, higher peak cylinder pressure and temperature were reported at increased injection pressures (Bari et al. 2004; Puhan et al. 2009; Rosli, et al. 2008; Roy 2009). Kruczynski et al. 2013 obtained results of engine tests using camelinasativa oil and reported relatively good engine performance and stressed the need to change the calibration parameters of the engine fuel system that cater to the use of the reported fuel. The high content of Linolenic acid of the oil results in combustion process different to that of diesel. Tompkins et al. 2012 highlighted the parameters influencing the gross indicated fuel conversion efficiency of biodiesel derived from palmolein and its B20 blend when compared with diesel oil. Biodiesels inherently shorter combustion durations and inherently lower air-fuel ratios, resulted into lower brake

thermal efficiency and this could be linked to its bound oxygen component. Biodiesel with lower heating value requires a longer injector opening to deliver roughly the same amount of energy to produce same torque as obtained with diesel. Varuvel et al. 2012 studied feasibility of biodiesel derived from waste fish fat and reported higher NOx emissions for biodiesel. NOx could be reduced by blending biodiesel with diesel and reported lowered brake thermal efficiency and increased particulate matter for the blends studied. Vedaraman et al. 2012 used methyl ester of sal oil (SOME) in diesel engine and reported reduced CO, HC and NOx emissions with comparable brake thermal efficiency. They concluded that SOME can be a potential substitute for diesel fuel.

2013-2014 (Biodiesels)

Mohsin, and Majid 2014, investigated experimentation on the integration of compressed natural gas (CNG) in diesel engine operated in diesel dual fuel (DDF) system using biodiesel blends which offered better exhaust emission and provides an attractive option for reducing the pollutants emitted from transportation fleets. The horse power and torque of biodiesel (B20-DDF) was found to be high compared to diesel. Mohsin R. and Majid J. 2014

1. T. Korakianitis, A.M. Namasivayam, R.J. Crookes, Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions, Progress in Energy and Combustion Science 37 (2011), 89-112, 2011.

S.M. Ashrafur Rahman ,2014; conducted performance of a diesel engine operated with Jatropha and Palm biodiesel blends at high idling conditions. The results obtained from experiment elucidate that, at all idling modes HC and CO emissions of both blends decreases, however, NO emissions increases compared to pure diesel fuel at both idling conditions, Jatropha blends emitted higher CO and HC compared to Palm biodiesels. Compared to diesel fuel, at high idling conditions brake specific fuel consumption increased for all Palm and Jatropha biodiesel diesel blends.

Sakthivel G. * 2014 ; studied the feasibility of using fish oil derived biodiesel in diesel engines. Experimental tests were carried out to evaluate the performance, emission and combustion characteristics of a single cylinder, constant speed, direct injection diesel engine using biodiesel–diesel blends, under variable load conditions. It was found that there was a reduction in NOx, HC and CO emission along with a marginal increase of CO and smoke emissions with the increase in biodiesel proportion in the fuel. The brake thermal efficiency was found to be higher compared to diesel for the entire load. The ignition delay, maximum heat release rate and combustion duration were lower for biodiesel–diesel blends compared to diesel.

Gökhan Tüccar* 2014 ; investigated experimentation on diesel engine fuelled with Citrus sinensis biodiesel blended with conventional diesel fuel in varying volumetric ratios . Fuel properties of blends and pure citrus sinensis biodiesel were found out and performance characteristics and exhaust emissions of the engine fueled with blends were analyzed The

engine performance experiments indicated that citrus sinensis biodiesel cause a slight reduction in torque and brake power values. Exhaust emission tests revealed that while CO emission values decrease, NO emission values increase with citrus sinensis biodiesel usage. Combustion chamber:

The combustion chamber of an engine plays a major role during the combustion of wide variety of fuels used. In this context, many researchers performed both experimental and simulation studies on the use of various combustion chambers (Arturo et al. 2003; Matsumoto et al. 1997). In re-entrant combustion chamber intensification of swirl and turbulence were reported to be higher when compared to cylindrical chambers which lead to more efficient combustion causing higher NOx emissions and lesser soot and HC emissions (Saito et al. 1986). Montajir et al. 2000 studied the effect of combustion chamber geometry on fuel spray behavior and found that a re-entrant type combustion chamber with round lip and round bottom corners provides better air and fuel distribution than a simple cylindrical combustion chamber. Experimental study to optimize the combination of injection timing and combustion chamber geometry to achieve higher performance and lower emissions from biodiesel fueled diesel engine has been reported. Toroidal re-entrant combustion chamber and retarded injection timing has been found to improve brake thermal efficiency and reduced brake specific fuel consumption (Jaichander and Annamalai 2012). Improvement in air entrainment with increased swirl and injection pressure were reported (Bharathi and Prasanthi, 2011; Mc Cracken and Abraham, 2001). Prasad et al. 2011 studied in-cylinder air motion in a number of combustion chamber geometries and identified a geometry which produced the highest in-cylinder swirl and turbulence kinetic energy around the compression top dead centre (TDC). Three dimensional CFD simulations involving flow and combustion chemistry were used to study effect of swirl induced by re-entrant piston bowl geometries on pollutant emissions of a single cylinder diesel engine fitted with a hemispherical piston bowl and an injector with finite sac volume. The optimal geometry of the re-entrant piston bowl geometry was confirmed by the detailed combustion simulations and emission predictions used. Optimum combustion chamber geometry of the engine showed better performance and emission levels. Suitable combustion geometry of bowl shape helps to increase squish area and proper mixing of gaseous fuel with air (Arturo, 2003; Shinde, 2012). Designing the combustion chamber with narrow and deep and with a shallow reentrance had a low protuberance on the cylinder axis and the spray oriented towards the bowl entrance reduced the NOx emission levels to the maximum extent (Jaichander, S., Annamalai, 2012, 2013; Matsumoto et al. 1997). Influence of combustion chamber geometry on pongamia oil methyl ester and its blend (B20) fuelled diesel engine were investigated (Jaichander, S., Annamalai, 2012) in which toroidal re-entrant and shallow depth re-entrant combustion chambers were used. Toroidalreentrant combustion chamber resulted into higher brake thermal efficiency, higher NOx and reduced emissions of particulates, CO, UBHC. Lower ignition delay, higher peak pressure with B20 were also obtained when compared to baseline hemispherical and shallow depth reentrant combustion chambers (Jaichander, S., Annamalai, 2012) .

Injection Strategies:

The behavior of fuel once it is injected in the combustion chamber and its interaction with air is important. It is well known that nozzle geometry and cavitations strongly affect evaporation and atomization processes of fuel. Suitable changes in the in-cylinder flow field resulted in differing combustion. The performance and emission characteristics of

compression ignition engines are largely governed by fuel atomization and spray processes which in turn are strongly influenced by the flow dynamics inside injector nozzle. Modern diesel engines use micro-orifices having various orifice designs and affect engine performance to a great extent. Effects of dynamic factors on injector flow, spray combustion and emissions have been investigated by various researchers (Mulemane et al. 2004; Som et al. 2010). Experimental studies involving the effects of nozzle orifice geometry on global injection and spray behavior has been reported (Pyari et al. 2008; Benajes et al. 2004; Hans et al. 2002).

Payri et al (2009) have studied effect of nozzle geometry on the combustion. They have used, three 6-hole sac nozzles, with different orifices degree of conicity. They had studied liquid phase penetration and stabilized liquid length in real engine conditions has been done. In the present work, CH and OH chemiluminescence techniques are used to thoroughly examine combustion process.

Jonas Galle et al (2012) have conducted experiments on diesel operated on residue of a fatty acid distillation. This bio-oil was heated to 110 to decrease the viscosity to 8 mPa s. the injectors working with the bio-oil failed prematurely with operation times ranging from 50 to 1500 h. The injectors and the fuel were investigated in order to know the reasons of the failure and to improve the operation of engine. The investigations reveled different causes, including plastic deformation and clogging of the injector’s passages, as well as micro cracks, erosion and cavitations damage. The failed injectors were compared with non affected ones from the same engine injectors from fossils diesel fuelled engines. It was found that the chemical and physical composition of the fuel enforced the failure of the injections.

Salvador et al (2011) have compared the internal nozzle flow of a standard diesel with a biodiesel fuel (soybean oil) at cavitating and non cavitating conditions using a homogeneous equileribum model. The takes into account the compressibility of both phases and use a barotropic equation of state which relates pressure and density to calculate the growth of cavitation. Furthermore, turbulence effects have been introduced using a RNG- model. The compression of both fuels in real diesel injectors nozzle has been performed in terms of mass flow, momentum flux, and effective velocity at the outlet and cavitations appearance. The decrease of injection velocity and cavitations intensity for the biodiesel notced by numerical simulation at different injection conditions, predict a worse air fuel mixing process.

Producer Gas-Diesel/Biodiesel operated Engines:

2013-2014

Turbocharged single/Dual Fuel Engines:

Single Fuel:

Charles l. Peterson * et al. 1995 ; presented a case study on Dodge Cummins turbocharged and intercooled diesel engine fuelled with ethyl ester of rape seed oil powered

test vehicle. Emissions tests with this vehicle showed a reduction in HC and NO but increase in CO and PM compared to diesel operation. N. Usta* et al. 2005; conducted experimental study on the performance and exhaust emissions of a turbocharged indirect injection diesel engine fuelled with tobacco seed oil methyl ester was performed at full and partial loads. The results showed that the addition of tobacco seed oil methyl ester (TSOME) to the diesel fuel reduced CO and SO emissions while causing slightly higher NOx emissions. It was found that the power and the e ciencyffi increased slightly with the addition of tobacco seed oil methyl ester. (Effect of Turbocharging) Murat Karabektas* et al. 2008 ; investigated the effects of turbocharger on the performance of a diesel engine using diesel and rapeseed oil methyl ester in terms of brake power, torque, brake specific consumption and thermal efficiency, as well as CO and NOx emissions at full load conditions with varying speeds between 1200 and 2400 rpm in intervals of 200 rpm. The evaluation of experimental data showed that the brake thermal efficiency of biodiesel was slightly higher than that of diesel fuel in both naturally aspirated and turbocharged conditions. Use of biodiesel improved the performance parameters and decreased CO emissions of the turbocharged engine compared to natural aspirated diesel fuel. Mustafa Canakci*et al. 2006; studied the combustion characteristics and emissions of two di erent petroleum diesel fuels (No. 1 &No. 2) and (biodiesel-soybean oil wereff compared). The tests were performed at steady state conditions in a four-cylinder turbocharged DI diesel engine at full load at 1400-rpm engine speed. The experimental results compared with No. 2 diesel fuel and biodiesel provided significant reductions in PM, CO. Biodiesel with No. 1 diesel fuel had a increase in brake-specific fuel consumption gave better emission results, NOx and brake-specific fuel consumption reduced.

Chao He,Yunshan Ge *,2010 ; Characterized the PAHs emissions of diesel engine fueled with diesel, biodiesel (B100) and its blend (B20), an experimental study has been carried out on a direct-injection turbocharged diesel engine, using B100 and B20 which showed significant reduction in the total PAHs emissions of diesel engine. The Benzo[a]Pyrene (BaP) equivalent of PAHs emissions were also decreased with the use of B100.

Cooling and Cleaning Systems:

A.G. Bhave* et al ,2007; described a wet packed bed scrubber-based producer gas cooling-cleaning system. The producer gas cooling–cleaning unit developed is a compact unit, in which the gas cooling and cleaning take place effectively in one vertical tower, unlike other systems which have several chambers for these tasks. They stated that, it is easy to operate, and has a low pressure drop. The unit will give a clean gas with tar + dust content below the limit of 150 mg/nm as long as the inlet gas tar + dust content is below about 600 mg/nm.

D.S Mandwe, S.R Gadge,2006; designed 20 kW cooling and cleaning system for wood chip gasifier consists of water ,wet and dry filters used to clean producer gas which is suitable for engine application gave tar content is in the range of 24 to 53.52 mg/m3.

Patak

Effect of hydrogen addition:

Radu Chiriac* 2013, present study continued the investigation on B20, 20% biodiesel (rapeseed methyl esters) blend effects and was also extended on B20 enriched with hydrogen. It was conducted on a conventional tractor diesel engine running alternatively with B20 and petroleum diesel at various speeds and full load .It was found that compared with petroleum diesel, the engine fueled with addition of hydrogen to B20 by aspiration into the intake air flow led to an increase of NOx emission and to lower smoke and CO emissions.

H. An, W.M. Yang*,2013; With the hydrogen assisted biodiesel combustion, the peak cylinder pressure and heat release rate increase at high engine loads due to the high burning velocity and fast flame propagation speed of hydrogen. However, a reduced performanceis seen at light load conditions. A general decreased trend is seen for CO and soot emissions at all the engine speeds and loads.

Bika et al*(2013); A supplement of hydrogen to B20 by aspiration in the intake air flow at 60% load leads to an increase of NOx emission at high speeds; a similar effect has the petroleum diesel enrichment with hydrogen. Smoke and CO emissions are lowered by hydrogen addition to B20.CO emission was reduced and THC emissions are generally low at 60% load .